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7.4 The Thoracic Cage - Anatomy and Physiology - BC Open Textbooks, Rice University

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7.4 The Thoracic Cage - Anatomy and Physiology - BC Open Textbooks, Rice University

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This chapter provides a nice review of thoracic anatomy. Please read the chapter and answer the review questions found at the end.

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Chapter 7. Axial Skeleton

Learning Objectives

By the end of this section, you will be able to:

Discuss the components that make up the thoracic cage

Identify the parts of the sternum and define the sternal angle

Discuss the parts of a rib and rib classifications

The thoracic cage (rib cage) forms the thorax (chest) portion of the body. It consists of the 12 pairs of ribs with their costal cartilages and the sternum ( Figure 1). The ribs are anchored posteriorly to the 12 thoracic vertebrae (T1-T12). The thoracic cage protects the heart and lungs.

The sternum is the elongated bony structure that anchors the anterior thoracic cage. It consists of three parts: the manubrium, body, and xiphoid process. The manubrium is the wider, superior portion of the sternum. The top of the manubrium has a shallow, U-shaped border called the jugular (suprasternal) notch. This can be easily felt at the anterior base of the neck, between the medial ends of the clavicles. The clavicular notch is the shallow depression located on either side at the superior-lateral margins of the manubrium. This is the site of the sternoclavicular joint, between the sternum and clavicle. The first ribs also attach to the manubrium.

The elongated, central portion of the sternum is the body. The manubrium and body join together at the sternal angle, so called because the junction between these two components is not flat, but forms a slight bend. The second rib attaches to the sternum at the sternal angle. Since the first rib is hidden behind the clavicle, the second rib is the highest rib that can be identified by palpation. Thus, the sternal angle and second rib are important landmarks for the identification and counting of the lower ribs. Ribs 3-7 attach to the sternal body.

The inferior tip of the sternum is the xiphoid process. This small structure is cartilaginous early in life, but gradually becomes ossified starting during middle age.

Each rib is a curved, flattened bone that contributes to the wall of the thorax. The ribs articulate posteriorly with the T1-T12 thoracic vertebrae, and most attach anteriorly via their costal cartilages to the sternum. There are 12 pairs of ribs. The ribs are numbered 1-12 in accordance with the thoracic vertebrae.

Parts of a Typical Rib

The posterior end of a typical rib is called the head of the rib (see Chapter 7.3 Figure 8). This region articulates primarily with the costal facet located on the body of the same numbered thoracic vertebra and to a lesser degree, with the costal facet located on the body of the next higher vertebra. Lateral to the head is the narrowed neck of the rib. A small bump on the posterior rib surface is the tubercle of the rib, which articulates with the facet located on the transverse process of the same numbered vertebra. The remainder of the rib is the body of the rib (shaft). Just lateral to the tubercle is the angle of the rib, the point at which the rib has its greatest degree of curvature. The angles of the ribs form the most posterior extent of the thoracic cage. In the anatomical position, the angles align with the medial border of the scapula. A shallow costal groove for the passage of blood vessels and a nerve is found along the inferior margin of each rib.

Rib Classifications

The bony ribs do not extend anteriorly completely around to the sternum. Instead, each rib ends in a costal cartilage. These cartilages are made of hyaline cartilage and can extend for several inches. Most ribs are then attached, either directly or indirectly, to the sternum via their costal cartilage (see Figure 1). The ribs are classified into three groups based on their relationship to the sternum.

Ribs 1-7 are classified as true ribs (vertebrosternal ribs). The costal cartilage from each of these ribs attaches directly to the sternum. Ribs 8-12 are called false ribs (vertebrochondral ribs). The costal cartilages from these ribs do not attach directly to the sternum. For ribs 8-10, the costal cartilages are attached to the cartilage of the next higher rib. Thus, the cartilage of rib 10 attaches to the cartilage of rib 9, rib 9 then attaches to rib 8, and rib 8 is attached to rib 7. The last two false ribs (11-12) are also called floating ribs (vertebral ribs). These are short ribs that do not attach to the sternum at all. Instead, their small costal cartilages terminate within the musculature of the lateral abdominal wall.

The thoracic cage protects the heart and lungs. It is composed of 12 pairs of ribs with their costal cartilages and the sternum. The ribs are anchored posteriorly to the 12 thoracic vertebrae. The sternum consists of the manubrium, body, and xiphoid process. The manubrium and body are joined at the sternal angle, which is also the site for attachment of the second ribs.

Ribs are flattened, curved bones and are numbered 1-12. Posteriorly, the head of the rib articulates with the costal facets located on the bodies of thoracic vertebrae and the rib tubercle articulates with the facet located on the vertebral transverse process. The angle of the ribs forms the most posterior portion of the thoracic cage. The costal groove in the inferior margin of each rib carries blood vessels and a nerve. Anteriorly, each rib ends in a costal cartilage. True ribs (1-7) attach directly to the sternum via their costal cartilage. The false ribs (8-12) either attach to the sternum indirectly or not at all. Ribs 8-10 have their costal cartilages attached to the cartilage of the next higher rib. The floating ribs (11-12) are short and do not attach to the sternum or to another rib.

Review Questions

1. The sternum ________.

2. The sternal angle is the ________.

3. The tubercle of a rib ________.

4. True ribs are ________.

Critical Thinking Questions

1. Define the parts and functions of the thoracic cage.

2. Describe the parts of the sternum.

3. Discuss the parts of a typical rib.

4. Define the classes of ribs.

Glossary

angle of the rib

portion of rib with greatest curvature; together, the rib angles form the most posterior extent of the thoracic cage

body of the rib

shaft portion of a rib

clavicular notch

paired notches located on the superior-lateral sides of the sternal manubrium, for articulation with the clavicle

costal cartilage

hyaline cartilage structure attached to the anterior end of each rib that provides for either direct or indirect attachment of most ribs to the sternum

costal groove

shallow groove along the inferior margin of a rib that provides passage for blood vessels and a nerve

false ribs

vertebrochondral ribs 8-12 whose costal cartilage either attaches indirectly to the sternum via the costal cartilage of the next higher rib or does not attach to the sternum at all

floating ribs

vertebral ribs 11-12 that do not attach to the sternum or to the costal cartilage of another rib

head of the rib

posterior end of a rib that articulates with the bodies of thoracic vertebrae

jugular (suprasternal) notch

shallow notch located on superior surface of sternal manubrium

manubrium

expanded, superior portion of the sternum

neck of the rib

narrowed region of a rib, next to the rib head

sternal angle

junction line between manubrium and body of the sternum and the site for attachment of the second rib to the sternum

true ribs

vertebrosternal ribs 1-7 that attach via their costal cartilage directly to the sternum

tubercle of the rib

small bump on the posterior side of a rib for articulation with the transverse process of a thoracic vertebra

xiphoid process

small process that forms the inferior tip of the sternum

Solutions
Answers for Review Questions Answers for Critical Thinking Questions

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Chapter 7. Axial Skeleton By the end of this section, you will be able to: Discuss the components that make up the thoracic cage Identify the parts of the sternum and define the sternal angle Discuss the parts of a rib and rib classifications The thoracic cage (rib cage) forms the thorax (chest) portion of the body.

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Adult chest radiograph common exam pathologyDr Rohit Sharma and Dr Jeremy Jones, et al.

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Adult chest radiograph common exam pathologyDr Rohit Sharma and Dr Jeremy Jones, et al.

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CHeck out this article on some of the more common pathologies seen on chest radiographs. This article contains links to other great resources on radiopaedia as well!

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adult chest radiograph common exam pathology

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Adult chest radiograph common exam pathology | Radiology Reference Article | Radiopaedia.org

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Adult chest radiograph common exam pathology is essential to consider in the build up to radiology exams. The list of potential diagnoses is apparently endless, but there are some favourites that seem to appear with more frequency. When dealing ...

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This is an excellent image for review, as several important structures are called out, including the trachea and costophrenic angles.

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Public Domain

Alright, x-ray students - what is wrong with this lateral chest radiograph?

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Mediastinal structures on chest X-ray, annotated.jpg

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Mediastinal structures on chest X-ray, annotated.jpg

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In this image, the mediastinal structures, including the vascalature, are highlighted, allowing you to get a feel for where these structures lie in a PA chest radiograph. Although most of these structures are not directly visible on a chest x-ray, it is important to know their location and function.

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This is a short video from the National Cancer Institute of several patients being positioned for a standard chest x-ray. Note the correct use of shielding and tight collimation used.

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Button Battery Ingestion, R.E.B.E.L. EM, by  Salim R. Rezaie, MD

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Button Battery Ingestion, R.E.B.E.L. EM, by  Salim R. Rezaie, MD

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Creative Commons Attribution-NonCommercial-NoDerivs 3.0

Interesting article, and great demonstration of the importance of two views, 90 degrees from each other, in determining the location of foreign bodies.

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Button Batteries: Small, disc shaped battery cells which are designed for use in small electronic devices. Common sources are kids toys, watches, calculators and hearing aids. Most batteries use lithium as a power source

Button Battery Ingestion Danger:

Contact with mucosal surfaces (oropharynx, esophagus, nasal passage) results in transmission of current

Current transmission causes chemical burns and necrosis via alkaline injury (sodium hydroxide)

Tissue damage can progress rapidly and result in devastating injuries

Nasal passage and esophagus are most susceptible to injury (narrow places for battery to become lodged)

Injury Patterns

Viscous perforation

Fistula formation

Erosion into blood vessels and resultant bleeding and possible catastrophic bleeding with erosion into aorta

When to Suspect Ingestion:

Reported pediatric ingestion of unknown substance

Parent may report seeing "shiny" object being placed in mouth

Parent may report missing battery from open electronic device

Batteries are radio-opaque and will appear on plain X-rays

Views: At least 2 (PA and lateral)

Nasal placement: Obtain skull X-ray

Swallowed battery: Chest X-ray

Battery vs. Coin

Battery can often be mistake for the more benign coin ingestion on X-ray

En face view: may see a ring of radiolucency inside outer edge of object ("halo rim")

On edge view: may see a central bulge with a battery

Supportive Care

Aggressively resuscitate patients with hematemesis and/or signs of shock

Look for signs/symptoms of airway obstruction and control airway if necessary

Keep patient NPO

Obtain X-ray for localization of button battery

Nasal and Esophageal batteries should be removed within 2 hours of presentation to avoid significant necrosis. Do Not Wait for Symptoms to Develop!

Nasal battery

If battery can be visualized, can attempt removal with forceps, suction, skin glue on cotton swab or any other standard approach

If cannot visualize battery, obtain ENT consultation for direct visualization and removal with fiberoptics

GI Tract Battery

X-ray localizes to esophagus

Emergency consultation (Institution dependent - GI, Peds surgery) for direct visualization and removal

Removal without direct visualization (i.e. foley catheter removal) sub-optimal

Does not allow for visualization of mucosal injury

May result in translocation of of the battery from the esophagus to the trachea

If patient exhibits any evidence of mucosal damage, admit for observation

X-ray localizes distal to esophagus (i.e. stomach, small intestine)

Symptomatic or magnet co-ingestion

Emergency consultation (Institution dependent - GI, Peds surgery) for direct visualization and removal

Battery and magnet can cause problems even after passage into stomach via attraction of geographically distinct parts of bowel leading to obstruction or mucosal necrosis

Asymptomatic

If battery > 15 mm in child < 6 years of age

Lower risk of spontaneous passage

Repeat X-ray in 4 days. If battery still in stomach, remove under endoscopy

Expectant Management

Discharge home

Regular diet

Confirm passage by stool inspection or repeat X-ray in 10-14 days (if no passage, consider removal)

Continued Management

Development of any symptoms in a patient with battery beyond esophagus should prompt removal

Delayed perforation possible up to 28 days out of ingestion

Some gastroenterologists recommend routine repeat endoscopy

1. Button battery ingestions are extremely dangerous. Necrosis, perforation and erosion into vessels can occur in as little as 2 hours

2. ALL esophageal button batteries should be removed within 2 hours of presentation to minimize mucosal damage

3. Consider button battery ingestion in children presenting with dysphagia, refusal to eat and hematemesis

4. Co-ingestion of a button battery with a magnet requires emergency removal regardless of where it is in the GI system

For More on This Topic Checkout:

Post Peer Reviewed By: Salim Rezaie (Twitter: @srrezaie)

The following two tabs change content below.

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Button Battery Ingestion - R.E.B.E.L. EM - Emergency Medicine Blog

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Button Batteries: Small, disc shaped battery cells which are designed for use in small electronic devices. Common sources are kids toys, watches, calculators and hearing aids.

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ICU Chest Radiography Lines NG, Dobhoff, etc.

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ICU Chest Radiography Lines NG, Dobhoff, etc.

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While this presentation was designed for physicians, it provides valuable and easy to understand information on how to distinguish between the various lines and tubes that may be seen on ICU chest radiographs. It is crucial to know how to identify these lines and their correct placement, in order to ensure that you are providing the radiologist or physician with the necessary diagnostic information.

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ICU Chest Radiography Lines NG, Dobhoff, etc.

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This PA chest x-ray shows possible lung cancer, indicated by the mass seen in the left lung.

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Neonatal chest image quality addressed through training to enhance radiographer awarenessHesta Friedrich-Nel, Belinda van der Merwe, Beatrix Kotzé

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Neonatal chest image quality addressed through training to enhance radiographer awarenessHesta Friedrich-Nel, Belinda van der Merwe, Beatrix Kotzé

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Take a look at this interesting research article, regarding one of the most challenging areas of chest radiography.

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interdisciplinary health sciences; improvement of health safety and service delivery; management and measurement of health services; evaluation and assessment of health care needs; prevention of ill health and health-affecting behaviours; promotion of healthy lifestyles; health security

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Neonatal chest image quality addressed through training to enhance radiographer awareness | Friedrich-Nel | Health SA Gesondheid

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Health SA Gesondheid promotes communication, collaboration and teamwork between professions and disciplines within the health sciences to address problems that cross and affect disciplinary boundaries.