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Surface Anatomy of the Abdomen – Anatomy | Lecturio

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Trigonometric identities (trig identities) are equalities that involve trigonometric functions that are true for all values of the occurring variables. These identities are useful when we need to simplify expressions involving trigonometric functions.

The following is a list of useful Trigonometric identities: Quotient Identities, Reciprocal Identities, Pythagorean Identities, Co-function Identities, Addition Formulas, Subtraction Formulas, Double Angle Formulas, Even Odd Identities, Sum-to-product formulas, Product-to-sum formulas.

Scroll down the page to learn how the different Trigonometric identities are derived and how they may be used.

Quotient, Reciprocal and Pythagorean Identities

This video shows how to derive the Quotient, Reciprocal and Pythagorean identities.

Cofunction Identities

This video explains the cofunction identities and how to determine cofunctions given a function value. Cofunction Identities - Solving Trigonometric Equations
This video explains how to use cofunction identities to solve trigonometric equations.

Sum and Difference Identities for Sine and Cosine

The cosine addition formula calculates the cosine of an angle that is either the sum or difference of two other angles. It arises from the law of cosines and the distance formula. By using the cosine addition formula, the cosine of both the sum and difference of two angles can be found with the two angles' sines and cosines.

This video shows how to derive an identity for Cosine of a sum of two angles. It will use the unit circle definition for sine and cosine, the Pythagorean Identity, the distance formula between two points, and some algebra to derive an identity for cos ( a + b)

How to use the formula for the cosine of the sum of two angles to derive the formulas for the cosine of the difference of two angles, the sine of the sum of two angles, and the sine of the difference of two angles?
Examples using the formula are provided. How to use the sum and difference formula for cosine to find exact values of non-special angles? Sum and Difference Identities for Sine and Cosine
More examples of using the sum and difference identities to find value other trig values. Sine Addition Formula
Starting with the cofunction identities, the sine addition formula is derived by applying the cosine difference formula. There are two main differences from the cosine formula: (1) the sine addition formula adds both terms, where the cosine addition formula subtracts and the subtraction formula adds; and (2) the sine formulas have sin-sin and cos-cos. Both formulas find values for angles.
How to Prove the Addition and Subtraction Formula for sin(x+y) or sin(x-y)?

Using the Sine and Cosine Addition
Formulas to Prove Identities: Applying the cosine addition and sine addition formulas proves the cofunction, add π, and supplementary angle identities. Using the formulas, we see that sin(π/2-x) = cos(x), cos(π/2-x) = sin(x); that sin(x + π) = -sin(x), cos(x + π) = -cos(x); and that sin(π-x) = sin(x), cos(π-x) = -cos(x). The formulas also give the tangent of a difference formula, for tan(α - β).

How to use the sine and cosine subtraction formulas to prove the cofunction identities? How to use the sine and cosine addition formulas to prove the cofunction identities?

Sum and Difference Identities for Tangent

Double Angle Identities

Double Angle Formulas
The double angles sin 2θ and cos 2θ can be rewritten as sin(θ + θ) and cos(θ + θ). Applying the cosine and sine addition formulas, we find that sin 2θ = 2sin θ cos θ and cos 2θ = cos ² θ - sin ² θ. cos 2θ = cos ² θ - sin ² θ. Combining this formula with the Pythagorean Identity, cos ² θ + sin ² θ = 1, two other forms appear: cos 2θ = 2cos ² θ - 1 and cos 2θ = 1 - 2sin ² θ.

How to use the sine and cosine addition formulas to prove the double-angle formulas?
The derivation of the double angle identities for sine and cosine, followed by some examples. How to use the double-angle identities to determine function values

Sum to Product and Product to Sum Identities

How to use trig identities to rewrite trig expressions?

Half Angle Identities

The half angle identities come from the power reduction formulas using the key substitution α = θ/2 twice, once on the left and right sides of the equation. With half angle identities, on the left side, this yields (after a square root) cos(θ/2) or sin(θ/2); on the right side cos 2θ becomes cos θ because 2(1/2) = 1. For a problem like sin(π/12), remember that θ/2 = π/12, or θ = π/6, when substituting into the identity.
The derivations of the half-angle identities for both sine and cosine, plus listing the tangent ones. Then a couple of examples using the identities. How to use the half-angle identities to determine function values?

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Trigonometric identities (trig identities) are equalities that involve trigonometric functions that are true for all values of the occurring variables. These identities are useful when we need to simplify expressions involving trigonometric functions. The following is a list of useful Trigonometric identities: Quotient Identities, Reciprocal Identities, Pythagorean Identities, Co-function Identities, Addition Formulas, Subtraction Formulas, Double Angle Formulas, Even Odd Identities, Sum-to-product formulas, Product-to-sum formulas.

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Trick for Memorizing the Reciprocal Identities

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Shannon had NO CLUE what this was! LOL

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Using Padlet, create a bookmark for your muscle group. 1)identify the origin and insertion 2) insert a labeled image of the muscle.

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Using Padlet, create a bookmark for your muscle group. 1)identify the origin and insertion 2) insert a labeled image of the muscle.

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TRICEPS SURAE GASTROCNEMIUS SOLEUS PLANTARIS with Clinical Aspects – Sanjoy Sanyal

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Zygote Body 3D Anatomy Online Visualizer | Human Anatomy 3D

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Zygote Body is a free online 3D anatomy atlas. View, isolate, and learn human anatomy structures with Zygote Body.

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Learning Objectives

By the end of this section, you will be able to identify the following muscles and give their origins, insertions, actions and innervations:

Axial muscles of the head neck and back

Axial muscles of the abdominal wall and thorax

Muscles of the pectoral girdle and upper limb

Appendicular muscles of the pelvic girdle and lower limbs

The muscles of facial expression originate from the surface of the skull or the fascia (connective tissue) of the face. The insertions of these muscles have fibers intertwined with connective tissue and the dermis of the skin. Because the muscles insert in the skin rather than on bone, when they contract, the skin moves to create facial expression ( Figure 11.4.1).

Editor's note: Replace figure with one that includes all muscles from table for example figure 10.7 from Marieb or 9.8 from Amerman

The orbicularis oris is a circular muscle that moves the lips, and the orbicularis oculi is a circular muscle that closes the eye. The occipitofrontalis muscle elevates the scalp and eyebrows. The muscle has a frontal belly and an occipital belly (near the occipital bone on the posterior part of the skull). In other words, there is a muscle on the forehead ( frontalis) and one on the back of the head ( occipitals). The two bellies are connected by a broad tendon called the epicranial aponeurosis, or galea aponeurosis (galea = "apple"). The physicians originally studying human anatomy thought the skull looked like an apple.

The buccinator muscle compresses the cheek. This muscle allows you to whistle, blow, and suck; and it contributes to the action of chewing. There are several small facial muscles, one of which is the corrugator supercilii, which is the prime mover of the eyebrows. Place your finger on your eyebrows at the point of the bridge of the nose. Raise your eyebrows as if you were surprised and lower your eyebrows as if you were frowning. With these movements, you can feel the action of the corrugator supercilli. Additional muscles of facial expression are presented in Figure 11.4.2.

The movement of the eyeball is under the control of the extra ocular (extrinsic) eye muscles, which originate from the bones of the orbit and insert onto the outer surface of the white of the eye. These muscles are located inside the eye socket and cannot be seen on any part of the visible eyeball ( Figure 11.4.3 and Table 11.3). If you have ever been to a doctor who held up a finger and asked you to follow it up, down, and to both sides, he or she is checking to make sure your eye muscles are acting in a coordinated pattern.

In anatomical terminology, chewing is called mastication. Muscles involved in chewing must be able to exert enough pressure to bite through and then chew food before it is swallowed ( Figure 11.4.4 and Table 11.4). The masseter muscle is the prime mover muscle for chewing because it elevates the mandible (lower jaw) to close the mouth, and it is assisted by the temporalis muscle, which retracts the mandible. You can feel the temporalis move by putting your fingers to your temple as you chew. The medial pterygoid and lateral pterygoid muscles provide assistance in chewing and moving food within the mouth by moving the mandible laterally and medially to grind food between the molars.

EDITOR'S NOTE: THIS IMAGE SHOULD BE REPLACED WITH ONE THAT MORE ACCURATELY ILLUSTRATES THE ORIGIN OF THE MASSETER MUSCLE. FOR EXAMPLE MARIEB FIG. 10.8 OR FIGURE 9.10 FROM AMERMAN

Although the tongue is obviously important for tasting food, it is also necessary for mastication, deglutition (swallowing), and speech ( Figure 11.4.5 and Figure 11.4.6). Because of its mobility, the tongue facilitates complex speech patterns and sounds.

Tongue muscles can be extrinsic or intrinsic. Extrinsic tongue muscles insert into the tongue from outside origins, and the intrinsic tongue muscles insert into the tongue from origins within it. The extrinsic muscles move the whole tongue in different directions, whereas the intrinsic muscles allow the tongue to change its shape (such as, curling the tongue in a loop or flattening it).

The extrinsic muscles all include the word root glossus (glossus = "tongue"), and the muscle names are derived from where the muscle originates. The genioglossus (genio = "chin") originates on the mandible and allows the tongue to move downward and forward. The styloglossus originates on the styloid process of the temporal bone, and allows upward and backward motion. The palatoglossus originates on the soft palate to elevate the back of the tongue, and the hyoglossus originates on the hyoid bone to move the tongue downward and flatten it.

The muscles of the anterior neck assist in deglutition (swallowing) and speech by controlling the positions of the larynx (voice box), and the hyoid bone, a horseshoe-shaped bone that functions as a foundation on which the tongue can move. The muscles of the neck are categorized according to their position relative to the hyoid bone ( Figure 11.4.7). Suprahyoid muscles are superior to it, and the infrahyoid muscles are located inferiorly.

The suprahyoid muscles raise the hyoid bone, the floor of the mouth, and the larynx during deglutition. These include the digastric muscle, which has anterior and posterior bellies that work to elevate the hyoid bone and larynx when one swallows; it also depresses the mandible. The stylohyoid muscle moves the hyoid bone posteriorly, elevating the larynx, and the mylohyoid muscle lifts it and helps press the tongue to the top of the mouth. The geniohyoid depresses the mandible in addition to raising and pulling the hyoid bone anteriorly.

The strap-like infrahyoid muscles generally depress the hyoid bone and control the position of the larynx. The omohyoid muscle, which has superior and inferior bellies, depresses the hyoid bone in conjunction with the sternohyoid and thyrohyoid muscles. The thyrohyoid muscle also elevates the larynx's thyroid cartilage, whereas the sternothyroid depresses it.

The head is balanced, moved and rotated by the neck muscles ( Table 11.5). When these muscles act unilaterally, the head rotates. When they contract bilaterally, the head flexes or extends. The major muscle that laterally flexes and rotates the head is the sternocleidomastoid. In addition, both muscles working together are the flexors of the head. Place your fingers on both sides of the neck and turn your head to the left and to the right. You will feel the movement originate there. This muscle divides the neck into anterior and posterior triangles when viewed from the side ( Figure 11.4.8).

The posterior muscles of the neck are primarily concerned with head movements, like extension. The back muscles stabilize and move the vertebral column, and are grouped according to the lengths and direction of the fascicles.

The splenius muscles originate at the midline and run laterally and superiorly to their insertions. From the sides and the back of the neck, the splenius capitis inserts onto the head region, and the splenius cervicis extends onto the cervical region. These muscles can extend the head, laterally flex it, and rotate it ( Figure 11.4.8).

The erector spinae group forms the majority of the muscle mass of the back and it is the primary extensor of the vertebral column. It controls extension, lateral flexion, and rotation of the vertebral column, and maintains the lumbar curve. The erector spinae comprises the iliocostalis (laterally placed) group, the longissimus (intermediately placed) group, and the spinalis (medially placed) group.

The iliocostalis group includes the iliocostalis cervicis, associated with the cervical region; the iliocostalis thoracis, associated with the thoracic region; and the iliocostalis lumborum, associated with the lumbar region. The three muscles of the longissimus group are the longissimus capitis, associated with the head region; the longissimus cervicis, associated with the cervical region; and the longissimus thoracis, associated with the thoracic region. The third group, the spinalis group, comprises the spinalis capitis (head region), the spinalis cervicis (cervical region), and the spinalis thoracis (thoracic region).

The transversospinales muscles run from the transverse processes to the spinous processes of the vertebrae. Similar to the erector spinae muscles, the semispinalis muscles in this group are named for the areas of the body with which they are associated. The semispinalis muscles include the semispinalis capitis, the semispinalis cervicis, and the semispinalis thoracis. The multifidus muscle of the lumbar region helps extend and laterally flex the vertebral column.

Important in the stabilization of the vertebral column is the segmental muscle group, which includes the interspinales and intertransversarii muscles. These muscles bring together the spinous and transverse processes of each consecutive vertebra. Finally, the scalene muscles work together to flex, laterally flex, and rotate the head. They also contribute to deep inhalation. The scalene muscles include the anterior scalene muscle (anterior to the middle scalene), the middle scalene muscle (the longest, intermediate between the anterior and posterior scalenes), and the posterior scalene muscle (the smallest, posterior to the middle scalene).

EDITOR'S NOTE: WE NEED A TABLE FOR THE MUSCLES OF POSTERIOR NECK AND BACK

AXIAL MUSCLES OF THE ABDOMINAL WALL AND THORAX

It is a complex job to balance the body on two feet and walk upright. The muscles of the vertebral column, thorax, and abdominal wall extend, flex, and stabilize different parts of the body's trunk. The deep muscles of the body's core help maintain posture as well as provide stability for movement of the limbs.

There are four pairs of abdominal muscles that make up the abdominal wall: the rectus abdominis, the external abdominal obliques, the internal abdominal obliques and the transverse abdominis ( Figure 11.4.9 and Table 11.6).

There are three flat skeletal muscles in the antero-lateral wall of the abdomen. The external oblique, closest to the surface, extend inferiorly and medially, in the direction of sliding one's four fingers into pants pockets. Perpendicular to it is the intermediate internal oblique, extending superiorly and medially, the direction the thumbs usually go when the other fingers are in the pants pocket. The deep muscle, the transverse abdominis, is arranged transversely around the abdomen, similar to a belt. This arrangement of three bands of muscles in different orientations allows various movements and rotations of the trunk. The three layers of muscle also help to protect the internal abdominal organs in an area where there is no bone.

The linea alba is a white, fibrous band that is made of the bilateral rectus sheaths (see Figure 1a) that join at the anterior midline of the body. These enclose the rectus abdominis muscles that originate at the pubic crest and symphysis, and extend the length of the body's trunk. Each muscle is segmented by three transverse bands of collagen fibers called the tendinous intersections resulting in the look of "six-pack abs".

The posterior abdominal wall is formed by the lumbar vertebrae, parts of the ilia of the hip bones, psoas major and iliacus muscles, and quadratus lumborum muscle. This part of the core plays a key role in stabilizing the rest of the body and maintaining posture.

Career Connection - Physical Therapists

Those who have a muscle or joint injury will most likely be sent to a physical therapist (PT) after seeing their regular doctor. PTs have a master's degree or doctorate, and are highly trained experts in the mechanics of body movements. Many PTs also specialize in sports injuries.

If you injured your shoulder while you were kayaking, the first thing a physical therapist would do during your first visit is assess the functionality of the joint. The range of motion of a particular joint refers to the normal movements the joint performs. The PT will ask you to abduct and adduct, circumduct, and flex and extend the arm. The PT will note the shoulder's degree of function, and based on the assessment of the injury, will create an appropriate physical therapy plan.

The first step in physical therapy will probably be applying a heat pack to the injured site, which acts much like a warm-up to draw blood to the area, to enhance healing. You will be instructed to do a series of exercises to continue the therapy at home, followed by icing, to decrease inflammation and swelling, which will continue for several weeks. When physical therapy is complete, the PT will do an exit exam and send a detailed report on the improved range of motion and return of normal limb function to your doctor. Gradually, as the injury heals, the shoulder will begin to function correctly. A PT works closely with patients to help them get back to their normal level of physical activity.

The muscles of the chest serve to facilitate breathing by changing the volume of the thoracic cavity ( Table 11.7). When you inhale your chest rises increasing the volume of the thoracic cavity. Alternately, when you exhale, your chest falls decreasing the volume of the thoracic cavity.

The Diaphragm

The change in volume of the thoracic cavity during breathing is due to the alternate contraction and relaxation of the diaphragm ( Figure 11.4.10). It separates the thoracic and abdominal cavities, and is dome-shaped at rest. The superior surface of the diaphragm is convex, creating the elevated floor of the thoracic cavity. The inferior surface is concave, creating the curved roof of the abdominal cavity.

Defecating, urination, and even childbirth involve cooperation between the diaphragm and abdominal muscles (this cooperation is referred to as the "Valsalva maneuver"). While you hold your breath the diaphragm and abdominal muscles contract increasing the pressure of the peritoneal cavity and stabilizing the core. When the abdominal muscles contract, the pressure cannot push the diaphragm up, so it increases pressure on the intestinal tract (defecation), urinary tract (urination), or reproductive tract (childbirth).

The inferior surface of the pericardial sac and the inferior surfaces of the pleural membranes (parietal pleura) fuse onto the central tendon of the diaphragm. To the sides of the tendon are the skeletal muscle portions of the diaphragm, which insert into the tendon while having a number of origins including the xiphoid process of the sternum anteriorly, the inferior six ribs and their cartilages laterally, and the lumbar vertebrae and 12th ribs posteriorly.

The diaphragm also includes three openings for the passage of structures between the thorax and the abdomen. The inferior vena cava passes through the caval opening, and the esophagus and attached nerves pass through the esophageal hiatus. The aorta, thoracic duct, and azygous vein pass through the aortic hiatus of the posterior diaphragm.

The Intercostal Muscles

There are three sets of muscles, called intercostal muscles, which span each of the intercostal spaces. The principal role of the intercostal muscles is to assist in breathing by changing the dimensions of the rib cage (Figure 11.4.11).

The 11 pairs of superficial external intercostal muscles aid in inspiration of air during breathing because when they contract, they raise the rib cage, which expands it. The 11 pairs of internal intercostal muscles, just under the externals, are used for expiration because they draw the ribs together to constrict the rib cage. The innermost intercostal muscles are the deepest, and they act as synergists for the action of the internal intercostals.

The pelvic floor (also referred to as the pelvic diaphragm) is a muscular sheet that defines the inferior portion of the pelvic cavity. The pelvic floor extends anteriorly to posteriorly from the pubis to the coccyx and is comprised of the levator ani and the ischiococcygeus. Its openings include the anal canal and urethra, and the vagina in women.

The large levator ani consists of two skeletal muscles, the pubococcygeus and the iliococcygeus ( Figure 11.4.12). The levator ani is considered the most important muscle of the pelvic floor because it supports the pelvic viscera. It resists the pressure produced by contraction of the abdominal muscles so that the pressure is applied to the colon to aid in defecation and to the uterus to aid in childbirth (assisted by the ischiococcygeus, which pulls the coccyx anteriorly). This muscle also creates skeletal muscle sphincters at the urethra and anus.

The perineum is the diamond-shaped space between the pubic symphysis (anteriorly), the coccyx (posteriorly), and the ischial tuberosities (laterally), lying just inferior to the pelvic diaphragm (levator ani and ischiococcygeus). Divided transversely into triangles, the anterior is the urogenital triangle, which includes the external genitals and the posterior is the anal triangle containing the anus ( Figure 11.4.13). The perineum is also divided into superficial and deep layers with some of the muscles common to men and women ( Figure 11.4.14). Women also have the compressor urethrae and the sphincter urethrovaginalis, which function to close the vagina. In men, the deep transverse perineal muscle plays a role in ejaculation.

MUSCLES OF THE PECTORAL GIRDLE AND UPPER LIMBS

Muscles of the shoulder and upper limb can be divided into four groups: muscles that stabilize and position the pectoral girdle, muscles that move the arm, muscles that move the forearm, and muscles that move the wrists, hands, and fingers.

The pectoral girdle, or shoulder girdle, consists of the lateral ends of the clavicle and scapula, along with the proximal end of the humerus, and the muscles covering these three bones to stabilize the shoulder joint. The girdle creates a base from which the head of the humerus, in its ball-and-socket joint with the glenoid fossa of the scapula, can move the arm in multiple directions.Muscles that position the pectoral girdle are located either on the anterior thorax or on the posterior thorax ( Figure 11.4.15 and Table 11.8). The anterior muscles include the subclavius, pectoralis minor, and serratus anterior. The posterior muscles include the trapezius, rhomboid major, and rhomboid minor. When the rhomboids are contracted, your scapula moves medially, which can pull the shoulder and upper limb posteriorly.

Muscles that Position the Pectoral Girdle (Table 11.8)

Position in the thorax

Movement

Target

Target motion direction

Prime mover

Origin

Insertion

Similar to the muscles that position the pectoral girdle, muscles that cross the shoulder joint and move the humerus bone of the arm include both axial and scapular muscles ( Figure 11.4.16 and Figure 11.4.17). The two axial muscles are the pectoralis major and the latissimus dorsi. The pectoralis major is thick and fan-shaped, covering much of the superior portion of the anterior thorax. The broad, triangular latissimus dorsi is located on the inferior part of the back and has multiple points of origin including the lumbosacral fascia attached to the inferior 6 thoracic vertebrae, the inferior 3 ribs, the iliac crest and inferior angle of the scapula.

The rest of the shoulder muscles originate on the scapula and help to move the arm. The deltoid is the major abductor of the arm but also facilitates flexing and medial rotation, as well as extension and lateral rotation. The subscapularis originates on subscapular fossa and medially rotates the arm. Named for their locations, the supraspinatus (originating from the supraspinous fossa) and the infraspinatus (originating from the infraspinous fossa) abduct the arm, and laterally rotate the arm, respectively. The thick and flat teres major is inferior to the teres minor and extends the arm, and assists in its adduction and medial rotation. The long teres minor laterally rotates the arm. Finally, the coracobrachialis flexes and adducts the arm.

The tendons of the subscapularis, supraspinatus, infraspinatus, and teres minor connect the scapula to the humerus, forming the rotator cuff (musculotendinous cuff), the circle of tendons around the shoulder joint. Although the shoulder joint allows a great deal of freedom of movement due to the shallow glenoid cavity it is extremely vulnerable to downward dislocation. The muscles and tendons of the rotator cuff provide stability to the joint. When baseball pitchers undergo shoulder surgery it is usually on the rotator cuff, which becomes pinched and inflamed, and may tear away from the bone due to the repetitive motion of bringing the arm overhead to throw a fast pitch.

The forearm, made of the radius and ulna bones, has four main types of action at the hinge of the elbow joint: flexion, extension, pronation, and supination. When the forearm faces anteriorly, it is supinated. When the forearm faces posteriorly, it is pronated. The forearm flexors include the biceps brachii, brachialis, and brachioradialis. The extensors are the triceps brachii and anconeus. The pronators are the pronator teres and the pronator quadratus, and the supinator turns the forearm anteriorly.

The biceps brachii, brachialis, and brachioradialis flex the forearm. The two-headed biceps brachii crosses the shoulder and elbow joints to flex the forearm, also taking part in supinating the forearm at the radioulnar joints and flexing the arm at the shoulder joint. Deep to the biceps brachii, the brachial is a synergist in forearm flexion. Finally, the brachioradialis can flex the forearm quickly or help lift a load slowly. These muscles and their associated blood vessels and nerves form the anterior compartment of the arm (anterior flexor compartment of the arm) ( Figure 11.4.18 and Figure 11.4.19).

Wrist, hand, and finger movements are facilitated by two groups of muscles. The forearm is the origin of the extrinsic muscles of the hand. The palm is the origin of the intrinsic muscles of the hand.

Extrinsic Muscles of the Hand

The muscles in the anterior compartment of the forearm (anterior flexor compartment of the forearm) originate on the humerus and insert onto different parts of the hand. These make up the bulk of the forearm. From lateral to medial, the superficial anterior compartment of the forearm includes the flexor carpi radialis, palmaris longus, flexor carpi ulnaris, and flexor digitorum superficialis. The flexor digitorum superficialis flexes the hand as well as the digits at the knuckles, which allows for rapid finger movements, as in typing or playing a musical instrument (see Figure 11.4.20 and Table 11.9). However, repetitive movement with poor ergonomics can irritate the tendons of these muscles as they slide back and forth with the carpal tunnel of the anterior wrist and pinch the median nerve, which also travels through the tunnel, causing Carpal Tunnel Syndrome. The deep anterior compartment produces flexion and bends fingers to make a fist. These are the flexor pollicis longus and the flexor digitorum profundus.

The muscles in the superficial posterior compartment of the forearm (superficial posterior extensor compartment of the forearm) originate on the humerus. These are the extensor radialis longus, extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, and the extensor carpi ulnaris.

The muscles of the deep posterior compartment of the forearm originate on the radius and ulna. These include the abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, and extensor indicis (see Figure 11.4.20).

The tendons of the forearm muscles attach to the wrist and extend into the hand. Fibrous bands called retinacula sheath the tendons at the wrist. The flexor retinaculum extends over the palmar surface of the hand while the extensor retinaculum extends over the dorsal surface of the hand.

Intrinsic Muscles of the Hand

The intrinsic muscles of the hand both originate and insert within it ( Figure 11.4.21). These muscles allow your fingers to make precise movements for actions, such as typing or writing. These muscles are divided into three groups. The thenar muscles are on the radial aspect of the palm. The hypothenar muscles are on the ulnar aspect of the palm, and the intermediate muscles are midpalmar.

The thenar muscles include the abductor pollicis brevis, opponens pollicis, flexor pollicis brevis, and the adductor pollicis. These muscles form the thenar eminence, the rounded contour of the base of the thumb, and all act on the thumb. The movements of the thumb play an integral role in most precise movements of the hand.

The hypothenar muscles include the abductor digiti minimi, flexor digiti minimi brevis, and the opponens digiti minimi. These muscles form the hypothenar eminence, the rounded contour of the little finger, and as such, they all act on the little finger. Finally, the intermediate muscles act on all the fingers and include the lumbrical, the palmar interossei, and the dorsal interossei.

The appendicular muscles of the lower body position and stabilize the pelvic girdle, which serves as a foundation for the lower limbs. Comparatively, there is much more movement at the pectoral girdle than at the pelvic girdle. There is very little movement of the pelvic girdle because of its connection with the sacrum at the base of the axial skeleton and because the deep acetabulum provides a stable point of articulation with the head of the femur. The pelvic girdle's lack of range of motion allows it to stabilize and support the body. The body's center of gravity is in the area of the pelvis. If the center of gravity were not to remain fixed, standing up would be difficult. Therefore, what the leg muscles lack in range of motion and versatility, they make up for in size and power, facilitating the body's stabilization, posture, and movement.

Gluteal Region Muscles That Move the Thigh

Most muscles that insert on the femur (the thigh bone) and move it, originate on the pelvic girdle. The major flexors of the hip are the psoas major and iliac which make up the iliopsoas group. Some of the largest and most powerful muscles in the body are the gluteal muscles or gluteal group. The gluteus maximus, one of the major extensors of the thigh at the hip, is the largest; deep to the gluteus maximus is the gluteus medius, and deep to the gluteus medius is the gluteus minimus, the smallest of the trio ( Figure 11.4.22 and Figure 11.4.23).

The tensor fascia latae is a thick, squarish muscle in the superior aspect of the lateral thigh. It acts as a synergist of the gluteus medius and iliopsoas in flexing and abducting the thigh. It also helps stabilize the lateral aspect of the knee by pulling on the iliotibial tract (band), making it taut. Deep to the gluteus maximus, the piriformis, obturator internus, obturator externus, superior gemellus, inferior gemellus, and quadratus femoris laterally rotate the thigh at the hip.

Deep fascia in the thigh separates it into medial, anterior, and posterior compartments ( EDITOR'S NOTE: SEE FIGURE X NEEDS TO BE ADDED-MARIEB 10.26). The muscles in the medial compartment of the thigh responsible for adducting the femur at the hip are the adductor group including the adductor longus, adductor brevis, and adductor magnus which all adduct and medially rotate the thigh. The adductor longus also flexes the thigh, whereas the adductor magnus extends it. Like the adductor longs, the pectineus adducts and flexes the femur at the hip. The pectineus is located in the femoral triangle, which is formed at the junction between the hip and the leg and includes the femoral nerve, the femoral artery, the femoral vein, and the deep inguinal lymph nodes. The strap-like gracilis adducts the thigh in addition to flexing the leg at the knee

Thigh Muscles That Move the Femur, Tibia, and Fibula

The muscles of the anterior compartment of the thigh flex the thigh and extend the leg. This compartment contains the quadriceps femoris group, which is comprised of four muscles that extend the leg and stabilize the knee. Within the compartment the rectus femoris is on the anterior aspect of the thigh, the vastus lateralis is on the lateral aspect of the thigh, the vastus medialis is on the medial aspect of the thigh, and the vastus intermedius is between the vastus lateralis and vastus medialis and deep to the rectus femoris. The tendon common to all four is the quadriceps tendon (patellar tendon), which inserts into the patella and continues below it as the patellar ligament. The patellar ligament attaches to the tibial tuberosity. In addition to the quadriceps femoris, the sartorius is a band-like muscle that extends from the anterior superior iliac spine to the medial side of the proximal tibia. This versatile muscle flexes the leg at the knee and flexes, abducts, and laterally rotates the thigh at the hip. This muscle allows us to sit cross-legged.

The posterior compartment of the thigh includes muscles that flex the leg and extend the thigh. The three long muscles on the back of the thigh are the hamstring group, which flexes the knee. These are the biceps femoris, semitendinosus, and semimembranosus. The tendons of these muscles form the upper border of the popliteal fossa, the diamond-shaped space at the back of the knee.

Muscles That Move the Feet and Toes

Similar to the thigh muscles, the muscles of the leg are divided by deep fascia into compartments, although the leg has three: anterior, lateral, and posterior (SEE FIGURE Xb MARIEB 10.26b ).

The muscles in the anterior compartment of the leg all contribute to dorsiflexion: the tibialis anterior, a long and thick muscle on the lateral surface of the tibia, the extensor hallucis longus, deep under it, and the extensor digitorum longus, lateral to it. The fibularis tertius, a small muscle that originates on the anterior surface of the fibula, is associated with the extensor digitorum longus and sometimes fused to it, but is not present in all people. Thick bands of connective tissue called the superior extensor retinaculum (transverse ligament of the ankle) and the inferior extensor retinaculum, hold the tendons of these muscles in place during dorsiflexion.

The lateral compartment of the leg includes two muscles which contribute to eversion and plantar flexion: the fibularis longus (peroneus longus) and the fibularis brevis (peroneus brevis). The superficial muscles in the posterior compartment of the leg all insert onto the calcaneal tendon (Achilles tendon), a strong tendon that inserts into the calcaneal bone of the ankle, all contribute to plantar flexion. The muscles in this compartment are large and strong and keep humans upright. The most superficial and visible muscle of the calf is the gastrocnemius. Deep to the gastrocnemius is the wide, flat soleus. The plantaris runs obliquely between the two; some people may have two of these muscles, whereas no plantaris is observed in about seven percent of other cadaver dissections. The plantaris tendon is a desirable substitute for the fascia lata in hernia repair, tendon transplants, and repair of ligaments. There are four deep muscles in the posterior compartment of the leg as well: the popliteus, flexor digitorum longus, flexor hallucis longus, and tibialis posterior all contribute to plantar flexion or inversion of the foot.

The foot also has intrinsic muscles, which originate and insert within it (similar to the intrinsic muscles of the hand). These muscles primarily provide support for the foot and its arch, and contribute to movements of the toes ( Figure 11.4.27 and Figure 11.4.28). The principal support for the longitudinal arch of the foot is a deep fascia called plantar aponeurosis, which runs from the calcaneus bone to the toes (inflammation of this tissue is the cause of "plantar fasciitis," which can affect runners. The intrinsic muscles of the foot include the extensor digitorum brevis on the dorsal aspect and a plantar group, which consists of four layers.

Chapter Review

Muscles are either axial muscles or appendicular. The axial muscles are grouped based on location, function, or both. Some axial muscles cross over to the appendicular skeleton. The muscles of the head and neck are all axial. The muscles in the face create facial expression by inserting into the skin rather than onto bone. Muscles that move the eyeballs are extrinsic, meaning they originate outside of the eye and insert onto it. Tongue muscles are both extrinsic and intrinsic. The genioglossus depresses the tongue and moves it anteriorly; the styloglossus lifts the tongue and retracts it; the palatoglossus elevates the back of the tongue; and the hyoglossus depresses and flattens it. The muscles of the anterior neck facilitate swallowing and speech, stabilize the hyoid bone and position the larynx. The muscles of the neck stabilize and move the head. The sternocleidomastoid divides the neck into anterior and posterior triangles.

The muscles of the back and neck that move the vertebral column are complex, overlapping, and can be divided into five groups. The splenius group includes the splenius capitis and the splenius cervicis. The erector spinae has three subgroups. The iliocostalis group includes the iliocostalis cervicis, the iliocostalis thoracis, and the iliocostalis lumborum. The longissimus group includes the longissimus capitis, the longissimus cervicis, and the longissimus thoracis. The spinalis group includes the spinalis capitis, the spinalis cervicis, and the spinalis thoracis. The transversospinales include the semispinalis capitis, semispinalis cervicis, semispinalis thoracis, multifidus, and rotatores. The segmental muscles include the interspinales and intertransversarii. Finally, the scalenes include the anterior scalene, middle scalene, and posterior scalene.

Made of skin, fascia, and four pairs of muscle, the anterior abdominal wall protects the organs located in the abdomen and moves the vertebral column. These muscles include the rectus abdominis, which extends through the entire length of the trunk, the external oblique, the internal oblique, and the transversus abdominus. The quadratus lumborum forms the posterior abdominal wall.

The muscles of the thorax play a large role in breathing, especially the dome-shaped diaphragm. When it contracts and flattens, the volume inside the pleural cavities increases, which decreases the pressure within them. As a result, air will flow into the lungs. The external and internal intercostal muscles span the space between the ribs and help change the shape of the rib cage and the volume-pressure ratio inside the pleural cavities during inspiration and expiration.

The perineum muscles play roles in urination in both sexes, ejaculation in men, and vaginal contraction in women. The pelvic floor muscles support the pelvic organs, resist intra-abdominal pressure, and work as sphincters for the urethra, rectum, and vagina.

The clavicle and scapula make up the pectoral girdle, which provides a stable origin for the muscles that move the humerus. The muscles that position and stabilize the pectoral girdle are located on the thorax. The anterior thoracic muscles are the subclavius, pectoralis minor, and the serratus anterior. The posterior thoracic muscles are the trapezius, levator scapulae, rhomboid major, and rhomboid minor. Nine muscles cross the shoulder joint to move the humerus. The ones that originate on the axial skeleton are the pectoralis major and the latissimus dorsi. The deltoid, subscapularis, supraspinatus, infraspinatus, teres major, teres minor, and coracobrachialis originate on the scapula.

The forearm flexors include the biceps brachii, brachialis, and brachioradialis. The extensors are the triceps brachii and anconeus. The pronators are the pronator teres and the pronator quadratus. The supinator is the only one that turns the forearm anteriorly.

The extrinsic muscles of the hands originate along the forearm and insert into the hand in order to facilitate crude movements of the wrists, hands, and fingers. The superficial anterior compartment of the forearm produces flexion. These muscles are the flexor carpi radialis, palmaris longus, flexor carpi ulnaris, and the flexor digitorum superficialis. The deep anterior compartment produces flexion as well. These are the flexor pollicis longus and the flexor digitorum profundus. The rest of the compartments produce extension. The extensor carpi radialis longus, extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, and extensor carpi ulnaris are the muscles found in the superficial posterior compartment. The deep posterior compartment includes the abductor longus, extensor pollicis brevis, extensor pollicis longus, and the extensor indicis.

Finally, the intrinsic muscles of the hands allow our fingers to make precise movements, such as typing and writing. They both originate and insert within the hand. The thenar muscles, which are located on the lateral part of the palm, are the abductor pollicis brevis, opponens pollicis, flexor pollicis brevis, and adductor pollicis. The hypothenar muscles, which are located on the medial part of the palm, are the abductor digiti minimi, flexor digiti minimi brevis, and opponens digiti minimi. The intermediate muscles, located in the middle of the palm, are the lumbricals, palmar interossei, and dorsal interossei.

The pelvic girdle attaches the legs to the axial skeleton. The hip joint is where the pelvic girdle and the leg come together. The hip is joined to the pelvic girdle by many muscles. In the gluteal region, the psoas major and iliacus form the iliopsoas. The large and strong gluteus maximus, gluteus medius, and gluteus minimus extend and abduct the femur. Along with the gluteus maximus, the tensor fascia lata muscle forms the iliotibial tract. The lateral rotators of the femur at the hip are the piriformis, obturator internus, obturator externus, superior gemellus, inferior gemellus, and quadratus femoris. On the medial part of the thigh, the adductor longus, adductor brevis, and adductor magnus adduct the thigh and medially rotate it. The pectineus muscle adducts and flexes the femur at the hip.

The thigh muscles that move the femur, tibia, and fibula are divided into medial, anterior, and posterior compartments. The medial compartment includes the adductors, pectineus, and the gracilis. The anterior compartment comprises the quadriceps femoris, quadriceps tendon, patellar ligament, and the sartorius. The quadriceps femoris is made of four muscles: the rectus femoris, the vastus lateralis, the vastus medius, and the vastus intermedius, which together extend the knee. The posterior compartment of the thigh includes the hamstrings: the biceps femoris, semitendinosus, and the semimembranosus, which all flex the knee.

The muscles of the leg that move the foot and toes are divided into anterior, lateral, superficial- and deep-posterior compartments. The anterior compartment includes the tibialis anterior, the extensor hallucis longus, the extensor digitorum longus, and the fibularis (peroneus) tertius. The lateral compartment houses the fibularis (peroneus) longus and the fibularis (peroneus) brevis. The superficial posterior compartment has the gastrocnemius, soleus, and plantaris; and the deep posterior compartment has the popliteus, tibialis posterior, flexor digitorum longus, and flexor hallucis longus.

Review Questions

1. Which of the following abdominal muscles is not a part of the anterior abdominal wall?

2. Which muscle pair plays a role in respiration?

3. What is the linea alba?

4. The rhomboid major and minor muscles are deep to the ________.

5. Which muscle extends the forearm?

6. What is the origin of the wrist flexors?

7. Which muscles stabilize the pectoral girdle?

8. The large muscle group that attaches the leg to the pelvic girdle and produces extension of the hip joint is the ________ group.

9. Which muscle produces movement that allows you to cross your legs?

10. What is the largest muscle in the lower leg?

11. The vastus intermedius muscle is deep to which of the following muscles?

Critical Thinking Questions

1. Explain the difference between axial and appendicular muscles.

2. Describe the muscles of the anterior neck.

3. Why are the muscles of the face different from typical skeletal muscle?

4. Which muscles form the hamstrings? How do they function together?

5. Which muscles form the quadriceps? How do they function together?

6. Describe the fascicle arrangement in the muscles of the abdominal wall. How do they relate to each other?

7. What are some similarities and differences between the diaphragm and the pelvic diaphragm?

8. The tendons of which muscles form the rotator cuff? Why is the rotator cuff important?

9. List the general muscle groups of the shoulders and upper limbs as well as their subgroups.

Glossary

abductor digiti minimi

muscle that abducts the little finger

abductor pollicis brevis

muscle that abducts the thumb

abductor pollicis longus

muscle that inserts into the first metacarpal

adductor brevis

muscle that adducts and medially rotates the thigh

adductor longus

muscle that adducts, medially rotates, and flexes the thigh

adductor magnus

muscle with an anterior fascicle that adducts, medially rotates and flexes the thigh, and a posterior fascicle that assists in thigh extension

adductor pollicis

muscle that adducts the thumb

anal triangle

posterior triangle of the perineum that includes the anus

anconeus

small muscle on the lateral posterior elbow that extends the forearm

anterior compartment of the arm

(anterior flexor compartment of the arm) the biceps brachii, brachialis, brachioradialis, and their associated blood vessels and nerves

anterior compartment of the forearm

(anterior flexor compartment of the forearm) deep and superficial muscles that originate on the humerus and insert into the hand

anterior compartment of the leg

region that includes muscles that dorsiflex the foot

anterior compartment of the thigh

region that includes muscles that flex the thigh and extend the leg

anterior scalene

a muscle anterior to the middle scalene

appendicular

of the arms and legs

axial

of the trunk and head

biceps brachii

two-headed muscle that crosses the shoulder and elbow joints to flex the forearm while assisting in supinating it and flexing the arm at the shoulder

biceps femoris

hamstring muscle

brachialis

muscle deep to the biceps brachii that provides power in flexing the forearm.

brachioradialis

muscle that can flex the forearm quickly or help lift a load slowly

buccinator

muscle that compresses the cheek

calcaneal tendon

(also, Achilles tendon) strong tendon that inserts into the calcaneal bone of the ankle

caval opening

opening in the diaphragm that allows the inferior vena cava to pass through; foramen for the vena cava

compressor urethrae

deep perineal muscle in women

coracobrachialis

muscle that flexes and adducts the arm

corrugator supercilii

prime mover of the eyebrows

deep anterior compartment

flexor pollicis longus, flexor digitorum profundus, and their associated blood vessels and nerves

deep posterior compartment of the forearm

(deep posterior extensor compartment of the forearm) the abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, extensor indicis, and their associated blood vessels and nerves

deep transverse perineal

deep perineal muscle in men

deglutition

swallowing

deltoid

shoulder muscle that abducts the arm as well as flexes and medially rotates it, and extends and laterally rotates it

diaphragm

skeletal muscle that separates the thoracic and abdominal cavities and is dome-shaped at rest

digastric

muscle that has anterior and posterior bellies and elevates the hyoid bone and larynx when one swallows; it also depresses the mandible

dorsal group

region that includes the extensor digitorum brevis

dorsal interossei

muscles that abduct and flex the three middle fingers at the metacarpophalangeal joints and extend them at the interphalangeal joints

epicranial aponeurosis

(also, galea aponeurosis) flat broad tendon that connects the frontalis and occipitalis

erector spinae group

large muscle mass of the back; primary extensor of the vertebral column

extensor carpi radialis brevis

muscle that extends and abducts the hand at the wrist

extensor carpi ulnaris

muscle that extends and adducts the hand

extensor digiti minimi

muscle that extends the little finger

extensor digitorum

muscle that extends the hand at the wrist and the phalanges

extensor digitorum brevis

muscle that extends the toes

extensor digitorum longus

muscle that is lateral to the tibialis anterior

extensor hallucis longus

muscle that is partly deep to the tibialis anterior and extensor digitorum longus

extensor indicis

muscle that inserts onto the tendon of the extensor digitorum of the index finger

extensor pollicis brevis

muscle that inserts onto the base of the proximal phalanx of the thumb

extensor pollicis longus

muscle that inserts onto the base of the distal phalanx of the thumb

extensor radialis longus

muscle that extends and abducts the hand at the wrist

extensor retinaculum

band of connective tissue that extends over the dorsal surface of the hand

external intercostal

superficial intercostal muscles that raise the rib cage

external oblique

superficial abdominal muscle with fascicles that extend inferiorly and medially

extrinsic eye muscles

originate outside the eye and insert onto the outer surface of the white of the eye, and create eyeball movement

extrinsic muscles of the hand

muscles that move the wrists, hands, and fingers and originate on the arm

femoral triangle

region formed at the junction between the hip and the leg and includes the pectineus, femoral nerve, femoral artery, femoral vein, and deep inguinal lymph nodes

fibularis brevis

(also, peroneus brevis) muscle that plantar flexes the foot at the ankle and everts it at the intertarsal joints

fibularis longus

(also, peroneus longus) muscle that plantar flexes the foot at the ankle and everts it at the intertarsal joints

fibularis tertius

small muscle that is associated with the extensor digitorum longus

flexor carpi radialis

muscle that flexes and abducts the hand at the wrist

flexor carpi ulnaris

muscle that flexes and adducts the hand at the wrist

flexor digiti minimi brevis

muscle that flexes the little finger

flexor digitorum longus

muscle that flexes the four small toes

flexor digitorum profundus

muscle that flexes the phalanges of the fingers and the hand at the wrist

flexor digitorum superficialis

muscle that flexes the hand and the digits

flexor hallucis longus

muscle that flexes the big toe

flexor pollicis brevis

muscle that flexes the thumb

flexor pollicis longus

muscle that flexes the distal phalanx of the thumb

flexor retinaculum

band of connective tissue that extends over the palmar surface of the hand

frontalis

front part of the occipitofrontalis muscle

gastrocnemius

most superficial muscle of the calf

genioglossus

muscle that originates on the mandible and allows the tongue to move downward and forward

geniohyoid

muscle that depresses the mandible, and raises and pulls the hyoid bone anteriorly

gluteal group

muscle group that extends, flexes, rotates, adducts, and abducts the femur

gluteus maximus

largest of the gluteus muscles that extends the femur

gluteus medius

muscle deep to the gluteus maximus that abducts the femur at the hip

gluteus minimus

smallest of the gluteal muscles and deep to the gluteus medius

gracilis

muscle that adducts the thigh and flexes the leg at the knee

hamstring group

three long muscles on the back of the leg

hyoglossus

muscle that originates on the hyoid bone to move the tongue downward and flatten it

hypothenar

group of muscles on the medial aspect of the palm

hypothenar eminence

rounded contour of muscle at the base of the little finger

iliacus

muscle that, along with the psoas major, makes up the iliopsoas

iliococcygeus

muscle that makes up the levator ani along with the pubococcygeus

iliocostalis cervicis

muscle of the iliocostalis group associated with the cervical region

iliocostalis group

laterally placed muscles of the erector spinae

iliocostalis lumborum

muscle of the iliocostalis group associated with the lumbar region

iliocostalis thoracis

muscle of the iliocostalis group associated with the thoracic region

iliopsoas group

muscle group consisting of iliacus and psoas major muscles, that flexes the thigh at the hip, rotates it laterally, and flexes the trunk of the body onto the hip

iliotibial tract

muscle that inserts onto the tibia; made up of the gluteus maximus and connective tissues of the tensor fasciae latae

inferior extensor retinaculum

cruciate ligament of the ankle

inferior gemellus

muscle deep to the gluteus maximus on the lateral surface of the thigh that laterally rotates the femur at the hip

infrahyoid muscles

anterior neck muscles that are attached to, and inferior to the hyoid bone

infraspinatus

muscle that laterally rotates the arm

innermost intercostal

the deepest intercostal muscles that draw the ribs together

intercostal muscles

muscles that span the spaces between the ribs

intermediate

group of midpalmar muscles

internal intercostal

muscles the intermediate intercostal muscles that draw the ribs together

internal oblique

flat, intermediate abdominal muscle with fascicles that run perpendicular to those of the external oblique

intrinsic muscles of the hand

muscles that move the wrists, hands, and fingers and originate in the palm

ischiococcygeus

muscle that assists the levator ani and pulls the coccyx anteriorly

lateral compartment of the leg

region that includes the fibularis (peroneus) longus and the fibularis (peroneus) brevis and their associated blood vessels and nerves

lateral pterygoid

muscle that moves the mandible from side to side

latissimus dorsi

broad, triangular axial muscle located on the inferior part of the back

levator ani

pelvic muscle that resists intra-abdominal pressure and supports the pelvic viscera

linea alba

white, fibrous band that runs along the midline of the trunk

longissimus capitis

muscle of the longissimus group associated with the head region

longissimus cervicis

muscle of the longissimus group associated with the cervical region

longissimus group

intermediately placed muscles of the erector spinae

longissimus thoracis

muscle of the longissimus group associated with the thoracic region

lumbrical

muscle that flexes each finger at the metacarpophalangeal joints and extend each finger at the interphalangeal joints

masseter

main muscle for chewing that elevates the mandible to close the mouth

medial compartment of the thigh

a region that includes the adductor longus, adductor brevis, adductor magnus, pectineus, gracilis, and their associated blood vessels and nerves

medial pterygoid

muscle that moves the mandible from side to side

middle scalene

longest scalene muscle, located between the anterior and posterior scalenes

multifidus

muscle of the lumbar region that helps extend and laterally flex the vertebral column

mylohyoid

muscle that lifts the hyoid bone and helps press the tongue to the top of the mouth

obturator externus

muscle deep to the gluteus maximus on the lateral surface of the thigh that laterally rotates the femur at the hip

obturator internus

muscle deep to the gluteus maximus on the lateral surface of the thigh that laterally rotates the femur at the hip

occipitalis

posterior part of the occipitofrontalis muscle

occipitofrontalis

muscle that makes up the scalp with a frontal belly and an occipital belly

omohyoid

muscle that has superior and inferior bellies and depresses the hyoid bone

opponens digiti minimi

muscle that brings the little finger across the palm to meet the thumb

opponens pollicis

muscle that moves the thumb across the palm to meet another finger

orbicularis oculi

circular muscle that closes the eye

orbicularis oris

circular muscle that moves the lips

palatoglossus

muscle that originates on the soft palate to elevate the back of the tongue

palmar interossei

muscles that abduct and flex each finger at the metacarpophalangeal joints and extend each finger at the interphalangeal joints

palmaris longus

muscle that provides weak flexion of the hand at the wrist

patellar ligament

extension of the quadriceps tendon below the patella

pectineus

muscle that abducts and flexes the femur at the hip

pectoral girdle

shoulder girdle, made up of the clavicle and scapula

pectoralis major

thick, fan-shaped axial muscle that covers much of the superior thorax

pectoralis minor

muscle that moves the scapula and assists in inhalation

pelvic diaphragm

muscular sheet that comprises the levator ani and the ischiococcygeus

pelvic girdle

hips, a foundation for the lower limb

perineum

diamond-shaped region between the pubic symphysis, coccyx, and ischial tuberosities

piriformis

muscle deep to the gluteus maximus on the lateral surface of the thigh that laterally rotates the femur at the hip

plantar aponeurosis

muscle that supports the longitudinal arch of the foot

plantar group

four-layered group of intrinsic foot muscles

plantaris

muscle that runs obliquely between the gastrocnemius and the soleus

popliteal fossa

diamond-shaped space at the back of the knee

popliteus

muscle that flexes the leg at the knee and creates the floor of the popliteal fossa

posterior compartment of the leg

region that includes the superficial gastrocnemius, soleus, and plantaris, and the deep popliteus, flexor digitorum longus, flexor hallucis longus, and tibialis posterior

posterior compartment of the thigh

region that includes muscles that flex the leg and extend the thigh

posterior scalene

smallest scalene muscle, located posterior to the middle scalene

pronator quadratus

pronator that originates on the ulna and inserts on the radius

pronator teres

pronator that originates on the humerus and inserts on the radius

psoas major

muscle that, along with the iliacus, makes up the iliopsoas

pubococcygeus

muscle that makes up the levator ani along with the iliococcygeus

quadratus femoris

muscle deep to the gluteus maximus on the lateral surface of the thigh that laterally rotates the femur at the hip

quadratus lumborum

posterior part of the abdominal wall that helps with posture and stabilization of the body

quadriceps femoris group

four muscles, that extend and stabilize the knee

quadriceps tendon

(also, patellar tendon) tendon common to all four quadriceps muscles, inserts into the patella

rectus abdominis

long, linear muscle that extends along the middle of the trunk

rectus femoris

quadricep muscle on the anterior aspect of the thigh

rectus sheaths

tissue that makes up the linea alba

retinacula

fibrous bands that sheath the tendons at the wrist

rhomboid major

muscle that attaches the vertebral border of the scapula to the spinous process of the thoracic vertebrae

rhomboid minor

muscle that attaches the vertebral border of the scapula to the spinous process of the thoracic vertebrae

rotator cuff

(also, musculotendinous cuff) the circle of tendons around the shoulder joint

sartorius

band-like muscle that flexes, abducts, and laterally rotates the leg at the hip

scalene muscles

flex, laterally flex, and rotate the head; contribute to deep inhalation

segmental muscle group

interspinales and intertransversarii muscles that bring together the spinous and transverse processes of each consecutive vertebra

semimembranosus

hamstring muscle

semispinalis capitis

transversospinales muscle associated with the head region

semispinalis cervicis

transversospinales muscle associated with the cervical region

semispinalis thoracis

transversospinales muscle associated with the thoracic region

semitendinosus

hamstring muscle

serratus anterior

large and flat muscle that originates on the ribs and inserts onto the scapula

soleus

wide, flat muscle deep to the gastrocnemius

sphincter urethrovaginalis

deep perineal muscle in women

spinalis capitis

muscle of the spinalis group associated with the head region

spinalis cervicis

muscle of the spinalis group associated with the cervical region

spinalis group

medially placed muscles of the erector spinae

spinalis thoracis

muscle of the spinalis group associated with the thoracic region

splenius

posterior neck muscles; includes the splenius capitis and splenius cervicis

splenius capitis

neck muscle that inserts into the head region

splenius cervicis

neck muscle that inserts into the cervical region

sternocleidomastoid

major muscle that laterally flexes and rotates the head

sternohyoid

muscle that depresses the hyoid bone

sternothyroid

muscle that depresses the larynx's thyroid cartilage

styloglossus

muscle that originates on the styloid bone, and allows upward and backward motion of the tongue

stylohyoid

muscle that elevates the hyoid bone posteriorly

subclavius

muscle that stabilizes the clavicle during movement

subscapularis

muscle that originates on the anterior scapula and medially rotates the arm

superficial anterior compartment of the forearm

flexor carpi radialis, palmaris longus, flexor carpi ulnaris, flexor digitorum superficialis, and their associated blood vessels and nerves

superficial posterior compartment of the forearm

extensor radialis longus, extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, extensor carpi ulnaris, and their associated blood vessels and nerves

superior extensor retinaculum

transverse ligament of the ankle

superior gemellus

muscle deep to the gluteus maximus on the lateral surface of the thigh that laterally rotates the femur at the hip

supinator

muscle that moves the palm and forearm anteriorly

suprahyoid muscles

neck muscles that are superior to the hyoid bone

supraspinatus

muscle that abducts the arm

temporalis

muscle that retracts the mandible

tendinous intersections

three transverse bands of collagen fibers that divide the rectus abdominis into segments

tensor fascia lata

muscle that flexes and abducts the thigh

teres major

muscle that extends the arm and assists in adduction and medial rotation of it

teres minor

muscle that laterally rotates and extends the arm

thenar

group of muscles on the lateral aspect of the palm

thenar eminence

rounded contour of muscle at the base of the thumb

thyrohyoid

muscle that depresses the hyoid bone and elevates the larynx's thyroid cartilage

tibialis anterior

muscle located on the lateral surface of the tibia

tibialis posterior

muscle that plantar flexes and inverts the foot

transversospinales

muscles that originate at the transverse processes and insert at the spinous processes of the vertebrae

transversus abdominis

deep layer of the abdomen that has fascicles arranged transversely around the abdomen

trapezius

muscle that stabilizes the upper part of the back

triceps brachii

three-headed muscle that extends the forearm

urogenital triangle

anterior triangle of the perineum that includes the external genitals

vastus intermedius

quadricep muscle that is between the vastus lateralis and vastus medialis and is deep to the rectus femoris

vastus lateralis

quadricep muscle on the lateral aspect of the thigh

vastus medialis

quadricep muscle on the medial aspect of the thigh

Solutions
Answers for Review Questions Answers for Critical Thinking Questions

1. Axial muscles originate on the axial skeleton (the bones in the head, neck, and core of the body), whereas appendicular muscles originate on the bones that make up the body's limbs.

2. The muscles of the anterior neck are arranged to facilitate swallowing and speech. They work on the hyoid bone, with the suprahyoid muscles pulling up and the infrahyoid muscles pulling down.

3. Most skeletal muscles create movement by actions on the skeleton. Facial muscles are different in that they create facial movements and expressions by pulling on the skin-no bone movements are involved.

4. Arranged into layers, the muscles of the abdominal wall are the internal and external obliques, which run on diagonals, the rectus abdominis, which runs straight down the midline of the body, and the transversus abdominis, which wraps across the trunk of the body.

5. Both diaphragms are thin sheets of skeletal muscle that horizontally span areas of the trunk. The diaphragm separating the thoracic and abdominal cavities is the primary muscle of breathing. The pelvic diaphragm, consisting of two paired muscles, the coccygeus and the levator ani, forms the pelvic floor at the inferior end of the trunk

6. Tendons of the infraspinatus, supraspinatus, teres minor, and the subscapularis form the rotator cuff, which forms a foundation on which the arms and shoulders can be stabilized and move.

7. The muscles that make up the shoulders and upper limbs include the muscles that position the pelvic girdle, the muscles that move the humerus, the muscles that move the forearm, and the muscles that move the wrists, hands, and fingers.

8. The biceps femoris, semimembranosus, and semitendinosus form the hamstrings. The hamstrings flex the leg at the knee joint.

9. The rectus femoris, vastus medialis, vastus lateralis, and vastus intermedius form the quadriceps. The quadriceps muscles extend the leg at the knee joint.

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11.4 Identify the skeletal muscles and give their origins, insertions, actions and innervations

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By the end of this section, you will be able to identify the following muscles and give their origins, insertions, actions and innervations: Axial muscles of the head neck and back Axial muscles of the abdominal wall and thorax Muscles of the pectoral girdle and upper limb Appendicular muscles of the pelvic girdle and lower limbs The muscles of facial expression originate from the surface of the skull or the fascia (connective tissue) of the face.

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Parallel Coaching - Personal Trainer Courses

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4 Steps to Remember Muscle Origins and Insertions

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Please scan these "bookmarks" for possible ways to create virtual experiential learning opportunities for your students.

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Please scan these "bookmarks" for possible ways to create virtual experiential learning opportunities for your students.

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Supporting, balancing, and propelling the body is the work of the muscular system of the legs and feet. From the large, strong muscles of the buttocks and legs to the tiny, fine muscles of the feet and toes, these muscles can exert tremendous power while constantly making small adjustments for balance - whether the body is at rest or in motion.

The powerful muscles of the hip, buttock, and pelvis actuate the flexible ball-and-socket hip joint. Continue Scrolling To Read More Below...

Continued From Above... The anterior muscles, such as the quadriceps femoris, iliopsoas, and sartorius, work as a group to flex the thigh at the hip and extend the leg at the knee. Posterior muscles, such as the hamstrings and gluteus maximus, produce the opposite motion - extension of the thigh at the hip and flexion of the leg at the knee. Lateral muscles, such as the gluteus medius, abduct the thigh at the hip while the medial groin muscles adduct the thigh. All of these muscle groups provide powerful contractions to propel the body while making fine adjustments to maintain the body's posture and balance.

Located inferior to the knee are a number of muscles that move the ankle, foot, and toes. The calf muscles, including the gastrocnemius and soleus, join to form the strong calcaneal (Achilles) tendon of the heel and attach to the calcaneus bone in the heel. These muscles contract to plantar flex the foot - such as when standing on your tiptoes - and flex the toes. Shin muscles, such as the tibialis anterior and extensor digitorum longus, dorsiflex the foot and extend the toes. The muscles of the calf also work subtly to stabilize the ankle joint and foot and to maintain the body's balance.

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Supporting, balancing, and propelling the body is the work of the muscular system of the legs and feet. From the large, strong muscles of the buttocks and legs to the tiny, fine muscles of the feet and toes, these muscles can exert tremendous power while constantly making small adjustments for balance - whether the body is at rest or in motion.

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Zygote Body 3D Anatomy Online Visualizer | Human Anatomy 3D

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Zygote Body is a free online 3D anatomy atlas. View, isolate, and learn human anatomy structures with Zygote Body.

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