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the Muscles are lint to the bones to move

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The nervous system is about what your going to do so its like you want to walk boom imedietly you will do it because the nervous system conects to the brain so thats how you walk and same thing with me am typing and how am typing is because of the nervous system!

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The skeletal system is about holding your body so then you can walk and play! so if you did not have bones you will be like a piecse of paper! so thats why we have bones in our body. Tim 4E

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The skeletal system is what helps with your muscles aswell to move around and have flexabilites! And help us from perventing injuries that bad.(From ali b 4c)

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The respiratory system is the network of organs and tissues that help you breathe. It includes your airways, lungs and blood vessels. The muscles that power your lungs are also part of the respiratory system. These parts work together to move oxygen throughout the body and clean out waste gases like carbon dioxide.

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the 7 main parts of the respiratory are the nose, mouth, throath , voice box, windpipe , airway and lungsC

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The respiratory system is the network of organs and tissues that help you breathe. It includes your airways, lungs and blood vessels. The muscles that power your lungs are also part of the respiratory system. These parts work together to move oxygen throughout the body and clean out waste gases like carbon dioxide.

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The  purpose of the circulatory system is to move nutrients,  oxygen and other gases to your body's organs, muscles and tissues, to use for energy, growth and repair. Heart disease, stroke and high or low blood pressure, are common circulatory system conditions.

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The  purpose of the circulatory system is to move nutrients,  oxygen and other gases to your body's organs, muscles and tissues, to use for energy, growth and repair. Heart disease, stroke and high or low blood pressure, are common circulatory system conditions.

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by Mayuri and Haneul 4C

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watch if u want by Daniel Jugaj 4c

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Anatomy and physiology of the respiratory system

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mira 4a

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Respiratory System | The Dr. Binocs Show | Learn Videos For Kids

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By Dyna 4A

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 amirsam 4c our body helps us move and do anything else

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 amirsam 4c our body helps us move and do anything else

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Dyna 4A

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what is the digestive system? its a system where it operates ur body and pushes the food around ur body and goes into ur large intestine.

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This is how the digestive system works the

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the movement of blood through the vessels of the body that is induced by the pumping action of the heart and serves to distribute nutrients and oxygen to and remove waste products from all parts of the body see pulmonary circulation, systemic circulation.

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Varlaam 4A. This is the picture of the small Intestine and the big intestine. Also there is anus and rectum.

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            Aurora 4a The respiratory system includes the nose, mouth, throat, voice box, windpipe, and lungs. Air enters the respiratory system through the nose or the mouth. If it goes into the nostrils (also called nares), the air is warmed and humidified.

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            Aurora 4a The respiratory system includes the nose, mouth, throat, voice box, windpipe, and lungs. Air enters the respiratory system through the nose or the mouth. If it goes into the nostrils (also called nares), the air is warmed and humidified.

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Circulatory System and Pathway of Blood Through the Heart

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The digestive system is a long, twisting tube that starts at the mouth and goes through the oesophagus, stomach, small intestine, large intestine and ends at the anus.

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Yellow Minimalist Neat Science The Digestive System Infographic

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The Heart and Circulatory System - How They Work

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What is the skeletal system short answer?

The skeletal system is your body's support structure. It gives your body its shape, allows movement, makes blood cells, provides protection for your organs and stores minerals.

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digestive system poster

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They bring oxygen into our bodies (called inspiration, or inhalation) and send carbon dioxide out (called expiration, or exhalation). This exchange of oxygen and carbon dioxide is called         Aurora respiration.

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They bring oxygen into our bodies (called inspiration, or inhalation) and send carbon dioxide out (called expiration, or exhalation). This exchange of oxygen and carbon dioxide is called         Aurora respiration.

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Language switcher. Your lungs are the pair of spongy, pinkish-gray organs in your chest. When you inhale (breathe in), air enters your lungs, and oxygen from that air moves to your blood. At the same time, carbon dioxide, a waste gas, moves from your blood to the lungs and is exhaled (breathed out).

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this is the digestive system and first you chew the food and then it go's in your auspices and then in your stomach and then in your intestine.

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The respiratory system takes up oxygen from the air we breathe and expels the unwanted carbon dioxide. The main organ of the respiratory system is the lungs. Other respiratory organs include the nose, the trachea and the breathing muscles (the diaphragm and the intercostal muscles).

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The digestive system is made up of the digestive tract (the gut) and other organs like the liver, pancreas and gall bladder. It is where your body breaks down food and absorbs nutrients.

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digestive system diagram

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1. first, you chew the food

2. the food goes into the esophagus

3. from the esophagus, it goes into the stomach where it gets broken down

4. after the food goes into the small intestine

5. then the large intestine

6. Lastly, it goes out from the anus

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The gastrointestinal system is the body system that eats and digests food; it is also called a digestive system.

By breaking down food into simple chemicals that can be absorbed by other parts of the body so the chemicals can be used for energy and building the body, it also gets rid of waste after digestion. The gastrointestinal system starts at the lips and ends at the anus. Animals like worms, insects, mammals, birds, fish, and people all have digestive systems.

The gastrointestinal tract is the gut and other organs that help us digest food.

The gut is the round tubes that food goes through and is digested. The parts of the human, and some other animals, gut system are:

Other organs that are part of the gastrointestinal system but are not part of the gut are:

Food does not go through these organs. But they help the gut digest the food. They also have other work. For example, the pancreas, thyroid, liver, and parathyroids are also endocrine glands that make hormones like insulin.

There are many diseases that affect the gastrointestinal system. Doctors who study the gastrointestinal tract are called gastroenterologists.

Human gastrointestinal tract

The structure and function can be described both as gross anatomy and as microscopic anatomy or histology. The tract itself is divided into upper and lower tracts, and the intestines small and large parts.

Upper gastrointestinal tract

The upper gastrointestinal tract consists of the mouth, pharynx, esophagus, stomach, and duodenum. The exact demarcation between the upper and lower tracts is the suspensory muscle of the duodenum. This differentiates the embryonic borders between the foregut and midgut, and is also the division commonly used by clinicians to describe gastrointestinal bleeding as being of either "upper" or "lower" origin. Upon dissection, the duodenum may appear to be a unified organ, but it is divided into four segments based upon function, location, and internal anatomy. The four segments of the duodenum are as follows (starting at the stomach, and moving toward the jejunum): bulb, descending, horizontal, and ascending. The suspensory muscle attaches the superior border of the ascending duodenum to the diaphragm.

The suspensory muscle is an important anatomical landmark which shows the formal division between the duodenum and the jejunum, the first and second parts of the small intestine, respectively. This is a thin muscle which is derived from the embryonic mesoderm.

Lower gastrointestinal tract

The lower gastrointestinal tract includes most of the small intestine and all of the large intestine. In human anatomy, the intestine ( bowel, or gut. Greek: éntera) is the segment of the gastrointestinal tract extending from the pyloric sphincter of the stomach to the anus and, as in other mammals, consists of two segments, the small intestine and the large intestine. In humans, the small intestine is further subdivided into the duodenum, jejunum and ileum while the large intestine is subdivided into the cecum, ascending, transverse, descending and sigmoid colon, rectum, and anal canal.

Small intestine

The small intestine begins at the duodenum and is a tubular structure, usually between 6 and 7 m long. Its mucosal area in an adult human is about 30 m ² (320 sq ft). The combination of the circular folds, the villi, and the microvilli increases the absorptive area of the mucosa about 600-fold, making a total area of about 250 square meters for the entire small intestine. Its main function is to absorb the products of digestion (including carbohydrates, proteins, lipids, and vitamins) into the bloodstream. There are three major divisions:

1. Duodenum: A short structure (about 20-25 cm long) which receives chyme from the stomach, together with pancreatic juice containing digestive enzymes and bile from the gall bladder. The digestive enzymes break down proteins, and bile emulsifies fats into micelles. The duodenum contains Brunner's glands which produce a mucus-rich alkaline secretion containing bicarbonate. These secretions, in combination with bicarbonate from the pancreas, neutralize the stomach acids contained in the chyme.

2. Jejunum: This is the midsection of the small intestine, connecting the duodenum to the ileum. It is about 2.5 m long, and contains the circular folds also known as plicae circulares, and villi that increase its surface area. Products of digestion (sugars, amino acids, and fatty acids) are absorbed into the bloodstream here.

3. Ileum: The final section of the small intestine. It is about 3 m long, and contains villi similar to the jejunum. It absorbs mainly vitamin B12 and bile acids, as well as any other remaining nutrients.

Large intestine

The large intestine also called the colon, consists of the cecum, rectum, and anal canal. It also includes the appendix, which is attached to the cecum. The colon is further divided into:

1. Cecum (first portion of the colon) and appendix

2. Ascending colon (ascending in the back wall of the abdomen)

3. Right colic flexure (flexed portion of the ascending and transverse colon apparent to the liver)

4. Transverse colon (passing below the diaphragm)

5. Left colic flexure (flexed portion of the transverse and descending colon apparent to the spleen)

6. Descending colon (descending down the left side of the abdomen)

7. Sigmoid colon (a loop of the colon closest to the rectum)

The main function of the large intestine is to absorb water. The area of the large intestinal mucosa of an adult human is about 2 m ² (22 sq ft).

Related pages

Images for kids

Illustration of the small intestine

In Spanish: Tracto gastrointestinal para niños

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Learn Gastrointestinal tract facts for kids

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The digestive system includes structures that form the alimentary canal and the accessory organs of digestion.

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The digestive system includes structures that form the alimentary canal and the accessory organs of digestion.

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By Karim 4A

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how does the digestive system works

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Digestive System | The Dr. Binocs Show | Learn Videos For Kids

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The digestive system is a long, twisting tube that starts at the mouth and goes through the oesophagus, stomach, small intestine, large intestine and ends at the anus. The digestive system breaks down food into simple nutrients such as carbohydrates, fats and proteins.

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The digestive system helps to break down the food for the body to process and use.

by Alex 4A

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This is the video to help you.

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Human digestive system - How it works! (Animation)

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We need food to fuel our bodies for energy, growth and repair. The digestive system converts the foods we eat into their simplest forms, like glucose (sugars), amino acids (that make up protein) or fatty acids (that make up fats). The broken-down food is then absorbed into the bloodstream from the small intestine and the nutrients are carried to each cell in the body.
The digestive tract begins at the mouth and ends at the anus. It is like a long muscular tube, up to 10 meters long, with digestive organs attached along the way.
A large reservoir of microbes, such as bacteria, live within the large intestine and, to a lesser degree, in vote rest of the digestive system. These bacteria play an important role in healthy digestion. The exact types of bacteria are particular to each person. Other factors that influence the type of bacteria in your digestive system include where you live in the world, what health conditions you have and what medications you have received.

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The respiratory system's main job is to move fresh air into your body while removing waste gases. Once in the lungs, oxygen is moved into the bloodstream and carried through your body. At each cell in your body, oxygen is exchanged for a waste gas called carbon dioxide.

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Fun Facts About the Digestive System

What is the digestive system?

The digestive system serves the role of taking in nutrients, eliminating waste, and absorbing and using the nutrients we take in. The digestive system includes all the parts of your body that are involved when you eat or drink.

While you may not think about your digestive system often, you are using it all the time. You also may not think of the digestive system as fun, but let’s take a look at some fun facts about your digestive system you may not have known.

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You swallow your food and it goes down your esophagus which goes into the stomach which then goes through to the small intestine to the large intestine into the anus.

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What is the digestive system?

Your digestive system is a network of organs that help you digest and absorb nutrition from your food. It includes your gastrointestinal (GI) tract and your biliary system. Your GI tract is a series of hollow organs that are all connected to each other, leading from your mouth to your anus. Your biliary system is a network of three organs that deliver bile and enzymes through to your GI tract your bile ducts.What does the digestive system do?

Your digestive system is uniquely constructed to do its job of turning your food into the nutrients and energy you need to survive. And when it’s done with that, it handily packages your solid waste, or stool, for disposal when you have a bowel movement

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The skeletal system is made up of about 270 bones at birth and decreases to about 206 bones as you reach adulthood.

More than half of the bones in the human skeleton are in the hands and feet.

Cartilage is a smooth and flexible substance that covers the tips of your bones where they meet.

Joints are where two or more bones in the body come together.

Ligaments are bands of strong connective tissue that hold bones together.

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I learned the organs and tissues help people breathe and clean the wasted gases such as carbon dioxide from the blood.

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The Nervous System | Educational Video for Kids

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The circulatory system in the human body stretches 66,000 miles, more than two and a half times the circumference of the Earth. The heart beats 2.5 billion times during the life of a 75-year-old. The heart expels 2 ounces of blood with each beat, five quarts of blood each minute, 220 million quarts in 70 years.

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The circulatory system in the human body stretches 66,000 miles, more than two and a half times the circumference of the Earth. The heart beats 2.5 billion times during the life of a 75-year-old. The heart expels 2 ounces of blood with each beat, five quarts of blood each minute, 220 million quarts in 70 years.

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By Karim 4A

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this is all of the respetory system.

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There are 26 bones in the human foot.

The human hand, including the wrist, contains 54 bones.

The femur, or thighbone, is the longest and strongest bone of the human skeleton.

The stapes, in the middle ear, is the smallest and lightest bone of the human skele

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Your digestive system is made up of a series of organs that allows your body to get the nutrients and energy it needs from the food we eat. As food travels through the digestive system it is broken down, sorted, and reprocessed before being circulated around the body to nourish and replace cells and supply energy to our muscles.

Digestion starts in the mouth where chewing and saliva breaks down food so it is more easily processed by your body.

Esophagus: The esophagus is a muscular tube that connects the pharynx (throat) to the stomach. The esophagus contracts as it moves food into the stomach. A "valve" called the lower esophageal sphincter (LES) is located just before the opening to the stomach. This valve opens to let food pass into the stomach from the esophagus and it prevents food from moving back up into the esophagus from the stomach.

Medical conditions related to the esophagus:

Stomach: An organ with strong muscular walls, the stomach holds the food and mixes it with acid and enzymes that continue to break the food down into a liquid or paste.

Small Intestine (Small Bowel): Almost 20 feet long, the small intestine is the workhorse of the digestive system. It will continue to break down food with enzymes released by the pancreas and bile released from the liver. It is made up of three segments, the duodenum, which continues the breakdown of food; and the jejunum and ileum, which are mainly responsible for the absorption of nutrients.

Medical conditions related to the small bowel:

Pancreas: Your pancreas is located behind your stomach and is attached to both your gall bladder and your small intestines. Among other functions, the pancreas aids in digestion by producing digestive enzymes and secreting them into the duodenum (the first segment of the small intestine). These enzymes break down protein, fats, and carbohydrates.

Medical conditions related to the pancreas:

Liver: An organ with many functions, your liver's two main responsibilities in the process of digestion are to make and secrete bile and to process and purify the blood containing newly absorbed nutrients that are coming from the small intestine. Bile has two main purposes: to help absorb fats and to carry waste from the liver that cannot go through the kidneys.

Medical conditions related to the liver:

Bile Ducts: Bile made in the liver travels to the small intestine through the bile ducts. If the bile isn't needed immediately, it is stored in the gallbladder.

Medical conditions related to the bile ducts:

Gallbladder: A pear-shaped reservoir located just under the liver that receives and stores bile made in the liver. The gallbladder sends this stored bile into the small intestine to aid in the digestion of food.

Colon (Large Intestine): A 5- to 7-foot-long muscular tube that connects the small intestine to the rectum and is responsible for processing waste so that defecation is easy and convenient. It is made up of the ascending (right) colon, the transverse (across) colon, the descending (left) colon and the sigmoid colon, which connects to the rectum.

Medical procedure related to the colon:

Rectum: An 8-inch chamber that connects the colon to the anus. The rectum receives stool from the colon, sends signals to the brain if there is stool to be evacuated, and holds stool until evacuation can happen.

Anus: The last part of the digestive tract, the anus, consists of pelvic floor muscles and two anal sphincters (internal and external). Together their jobs are to detect rectal contents, whether they are liquid, gas or solid, and then control when stool should and shouldn't be excreted from your body.

University of Michigan program related to the anus:

Medical Conditions Involving Multiple Digestive Organs

There are many medical conditions that involve more than one digestive organ. These include:

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Your digestive system is made up of a series of organs that allows your body to get the nutrients and energy it needs from the food we eat. As food travels through the digestive system it is broken down, sorted, and reprocessed before being circulated around the body to nourish and replace cells and supply energy to our muscles.

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The nervous system is the body's inner communication system. It's made up of the body's many nerve cells. The nerve cells take in information through the body's senses: touch, taste, smell, sight, and sound. The brain interprets these sensory cues to understand what's going on outside and inside the body

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The nervous system is the body's inner communication system. It's made up of the body's many nerve cells. The nerve cells take in information through the body's senses: touch, taste, smell, sight, and sound. The brain interprets these sensory cues to understand what's going on outside and inside the body

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By Karim 4A

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The respiratory system is the network of organs and tissues that help you breathe. It includes your airways, lungs and blood vessels. The muscles that power your lungs are also part of the respiratory system. These parts work together to move oxygen throughout the body and clean out waste gases like carbon dioxide

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The respiratory system is the network of organs and tissues that help you breathe. It includes your airways, lungs and blood vessels. The muscles that power your lungs are also part of the respiratory system. These parts work together to move oxygen throughout the body and clean out waste gases like carbon dioxide

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By Karim 4A

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SKELETAL system helps you move

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amirsam the human skeleten has more than 250 bones

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amirsam the human skeleten has more than 250 bones

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This is the systems in the body.

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respiratory system aumsum - Google Search

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Human Respiratory System | Respiratory System Anatomy | Biology | Letstute ... The Human Heart | #aumsum #kids #science #education #children. It’s…

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Nervous system send messages to your body like your brain.

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What is the skeletal system the skeletal system is a strong flexible framework of bones and connective tissue it provides support for the body and protection for many of it's internal parts. are you :) or :( lol  

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What is the skeletal system the skeletal system is a strong flexible framework of bones and connective tissue it provides support for the body and protection for many of it's internal parts. are you :) or :( lol  

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A skeletal system is a part of our body which can make us move.

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What Is the Nervous System?The nervous system includes the brain, spinal cord, and a complex network of nerves. This system sends messages back and forth between the brain and the body.The brain is what controls all the body's functions. The spinal cord runs from the brain down through the back. It contains threadlike nerves that branch out to every organ and body part. This network of nerves relays messages back and forth from the brain to different parts of the body.What Are the Parts of the Nervous System?The nervous system is made up of the central nervous system and the peripheral nervous system:The central nervous system includes the brain and spinal cord.The peripheral nervous system includes the nerves that run throughout the whole body.How Does the Nervous System Work?The nervous system uses tiny cells called neurons (NEW-ronz) to send messages back and forth from the brain, through the spinal cord, to the nerves throughout the body.Billions of neurons work together to create a communication network. Different neurons have different jobs. For example, sensory neurons send information from the eyes, ears, nose, tongue, and skin to the brain. Motor neurons carry messages away from the brain to the rest of the body to allow muscles to move. These connections make up the way we think, learn, move, and feel. They control how our bodies work — regulating breathing, digestion, and the beating of our hearts.

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What Is the Nervous System?The nervous system includes the brain, spinal cord, and a complex network of nerves. This system sends messages back and forth between the brain and the body.The brain is what controls all the body's functions. The spinal cord runs from the brain down through the back. It contains threadlike nerves that branch out to every organ and body part. This network of nerves relays messages back and forth from the brain to different parts of the body.What Are the Parts of the Nervous System?The nervous system is made up of the central nervous system and the peripheral nervous system:The central nervous system includes the brain and spinal cord.The peripheral nervous system includes the nerves that run throughout the whole body.How Does the Nervous System Work?The nervous system uses tiny cells called neurons (NEW-ronz) to send messages back and forth from the brain, through the spinal cord, to the nerves throughout the body.Billions of neurons work together to create a communication network. Different neurons have different jobs. For example, sensory neurons send information from the eyes, ears, nose, tongue, and skin to the brain. Motor neurons carry messages away from the brain to the rest of the body to allow muscles to move. These connections make up the way we think, learn, move, and feel. They control how our bodies work — regulating breathing, digestion, and the beating of our hearts.

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What does the respiratory system do?

Allows you to talk and to smell.

Warms air to match your body temperature and moisturizes it to the humidity level your body needs.

Delivers oxygen to the cells in your body.

Removes waste gases, including carbon dioxide, from the body when you exhale

fun facts-the right lung is bigger than the left lung because the heart takes a bit of space from the lung

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Circulatory System and Pathway of Blood Through the Heart

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What are the parts of the respiratory system?

The respiratory system has many different parts that work together to help you breathe. Each group of parts has many separate components.

Your airways deliver air to your lungs. Your airways are a complicated system that includes your:

Mouth and nose: Openings that pull air from outside your body into your respiratory system.

Sinuses: Hollow areas between the bones in your head that help regulate the temperature and humidity of the air you inhale.

Pharynx (throat): Tube that delivers air from your mouth and nose to the trachea (windpipe).

Trachea: Passage connecting your throat and lungs.

Bronchial tubes: Tubes at the bottom of your windpipe that connect into each lung.

Lungs: Two organs that remove oxygen from the air and pass it into your blood.

From your lungs, your bloodstream delivers oxygen to all your organs and other tissues.

Muscles and bones help move the air you inhale into and out of your lungs. Some of the bones and muscles in the respiratory system include your:

Diaphragm: Muscle that helps your lungs pull in air and push it out.

Ribs: Bones that surround and protect your lungs and heart.

When you breathe out, your blood carries carbon dioxide and other waste out of the body. Other components that work with the lungs and blood vessels include:

Alveoli: Tiny air sacs in the lungs where the exchange of oxygen and carbon dioxide takes place.

Bronchioles: Small branches of the bronchial tubes that lead to the alveoli.

Capillaries: Blood vessels in the alveoli walls that move oxygen and carbon dioxide.

Lung lobes: Sections of the lungs - three lobes in the right lung and two in the left lung.

Pleura: Thin sacs that surround each lung lobe and separate your lungs from the chest wall.

Some of the other components of your respiratory system include:

Cilia: Tiny hairs that move in a wave-like motion to filter dust and other irritants out of your airways.

Epiglottis: Tissue flap at the entrance to the trachea that closes when you swallow to keep food and liquids out of your airway.

Larynx (voice box): Hollow organ that allows you to talk and make sounds when air moves in and out.

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Respiratory System: Functions, Facts, Organs & Anatomy

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The respiratory system is the network that helps you breathe and smell, absorbing oxygen and cleaning waste gases so that the organs can work.

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The respiratory system includes the nose, mouth, throat, voice box, windpipe, and lungs. Air enters the respiratory system through the nose or the mouth. If it goes in the nostrils (also called nares), the air is warmed and humidified.

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The respiratory system includes the nose, mouth, throat, voice box, windpipe, and lungs. Air enters the respiratory system through the nose or the mouth. If it goes in the nostrils (also called nares), the air is warmed and humidified.

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Emre

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The Heart and Circulatory System - How They Work

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With each heartbeat, blood is sent throughout our bodies, carrying oxygen and nutrients to every cell. Every day, the approximately 10 pints (5 liters) of blood in your body travel many times through about 60,000 miles (96,560 kilometers) of blood vessels that branch and cross, linking the cells of our organs and body parts.

About the Heart and Circulatory System

The circulatory system is composed of the heart and blood vessels, including arteries, veins, and capillaries. Our bodies actually have two circulatory systems:

1. The pulmonary circulation is a short loop from the heart to the lungs and back again.

2. The systemic circulation (the system we usually think of as our circulatory system) sends blood from the heart to all the other parts of our bodies and back again.

The heart is the key organ in the circulatory system. As a hollow, muscular pump, its main job is to move blood through the body. It usually beats from 60 to 100 times per minute, but can go much faster if needed. It beats about 100,000 times a day, more than 30 million times per year, and about 2.5 billion times in a 70-year lifetime.

The heart gets messages from the body that tell it when to pump more or less blood depending on an individual's needs. When we're sleeping, it pumps just enough to provide for the lower amounts of oxygen needed by our bodies at rest. When we're exercising or frightened, the heart pumps faster to increase the delivery of oxygen.

The heart has four chambers that are enclosed by thick, muscular walls. It lies between the lungs and just to the left of the middle of the chest cavity. The bottom part of the heart is divided into two chambers: the right ventricle and the left ventricle. These pump blood out of the heart. A wall called the interventricular septum divides the ventricles.

The upper part of the heart is made up of the other two chambers of the heart: the right atrium and the left atrium. The atria receive the blood entering the heart. A wall called the interatrial septum divides the atria, which are separated from the ventricles by the atrioventricular valves. The tricuspid valve separates the right atrium from the right ventricle, and the mitral valve separates the left atrium from the left ventricle.

Two other cardiac valves separate the ventricles and the large blood vessels that carry blood leaving the heart. These are the pulmonic valve, which separates the right ventricle from the pulmonary artery leading to the lungs, and the aortic valve, which separates the left ventricle from the aorta, the body's largest blood vessel.

Arteries carry blood away from the heart. They are the thickest blood vessels, with muscular walls that contract to keep the blood moving away from the heart and through the body. In the systemic circulation, oxygen-rich blood is pumped from the heart into the aorta. This huge artery curves up and back from the left ventricle, then heads down in front of the spinal column into the abdomen. Two coronary arteries branch off at the beginning of the aorta and divide into a network of smaller arteries that provide oxygen and nourishment to the muscles of the heart.

Unlike the aorta, the body's other main artery, the pulmonary artery, carries oxygen-poor blood. From the right ventricle, the pulmonary artery divides into right and left branches, on the way to the lungs where blood picks up oxygen.

As they get farther from the heart, the arteries branch out into arterioles, which are smaller and less elastic.

Veins carry blood back to the heart. They're not as muscular as arteries, but they contain valves that prevent blood from flowing backward. Veins have the same three layers that arteries do, but are thinner and less flexible. The two largest veins are the superior and inferior vena cavae. The terms superior and inferior don't mean that one vein is better than the other, but that they're located above and below the heart.

A network of tiny capillaries connects the arteries and veins. Though tiny, the capillaries are one of the most important parts of the circulatory system because it's through them that nutrients and oxygen are delivered to the cells. Waste products such as carbon dioxide are also removed by the capillaries.

What the Heart and Circulatory System Do

The circulatory system works closely with other systems in our bodies. It supplies oxygen and nutrients to our bodies by working with the respiratory system. At the same time, the circulatory system helps carry waste and carbon dioxide out of the body.

Hormones - produced by the endocrine system - are also transported through the blood in the circulatory system. As the body's chemical messengers, hormones transfer information and instructions from one set of cells to another. For example, one of the hormones produced by the heart helps control the kidneys' release of salt from the body.

One complete heartbeat makes up a cardiac cycle, which consists of two phases:

1. In the first phase, the ventricles contract (this is called systole), sending blood into the pulmonary and systemic circulation. To prevent the flow of blood backward into the atria during systole, the atrioventricular valves close, creating the first sound (the lub). When the ventricles finish contracting, the aortic and pulmonary valves close to prevent blood from flowing back into the ventricles. This is what creates the second sound (the dub).

2. Then the ventricles relax (this is called diastole) and fill with blood from the atria, which makes up the second phase of the cardiac cycle.

A unique electrical conduction system in the heart causes it to beat in its regular rhythm. The sinus (or sinoatrial) node, a small area of tissue in the wall of the right atrium, sends out an electrical signal to start the contracting of the heart muscle. This node is called the pacemaker of the heart because it sets the rate of the heartbeat and causes the rest of the heart to contract in its rhythm.

These electrical impulses cause the atria to contract first, and then travel down to the atrioventricular or AV node, which acts as a kind of relay station. From here the electrical signal travels through the right and left ventricles, causing them to contract and forcing blood out into the major arteries.

In the systemic circulation, blood travels out of the left ventricle, to the aorta, to every organ and tissue in the body, and then back to the right atrium. The arteries, capillaries, and veins of the systemic circulatory system are the channels through which this long journey takes place.

Once in the arteries, blood flows to smaller arterioles and then to capillaries. While in the capillaries, the bloodstream delivers oxygen and nutrients to the body's cells and picks up waste materials. Blood then goes back through the capillaries into venules, and then to larger veins until it reaches the vena cavae.

Blood from the head and arms returns to the heart through the superior vena cava, and blood from the lower parts of the body returns through the inferior vena cava. Both vena cavae deliver this oxygen-depleted blood into the right atrium. From here the blood exits to fill the right ventricle, ready to be pumped into the pulmonary circulation for more oxygen.

In the pulmonary circulation, blood low in oxygen but high in carbon dioxide is pumped out the right ventricle into the pulmonary artery, which branches off in two directions. The right branch goes to the right lung, and vice versa.

In the lungs, the branches divide further into capillaries. Blood flows more slowly through these tiny vessels, allowing time for gases to be exchanged between the capillary walls and the millions of alveoli, the tiny air sacs in the lungs.

During the process called oxygenation, oxygen is taken up by the bloodstream. Oxygen locks onto a molecule called

hemoglobin in the red blood cells. The newly oxygenated blood leaves the lungs through the pulmonary veins and heads back to the heart. It enters the heart in the left atrium, then fills the left ventricle so it can be pumped into the systemic circulation.

What Problems Can Happen With the Heart and Circulatory System?

Problems with the cardiovascular system are common - more than 64 million Americans have some type of cardiac problem. But cardiovascular problems don't just affect older people - many heart and circulatory system problems affect children and teens too.

Heart and circulatory problems are grouped into two categories: congenital (problems someone is born with) and acquired (problems developed some time after birth).

To help keep the heart healthy and avoid long-term problems, adults and kids should:

Get plenty of exercise.

Eat a nutritious diet.

Reach and keep a healthy weight.

Have regular medical checkups.

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With each heartbeat, blood is sent throughout our bodies, carrying oxygen and nutrients to every cell. Every day, the approximately 10 pints (5 liters) of blood in your body travel many times through about 60,000 miles (96,560 kilometers) of blood vessels that branch and cross, linking the cells of our organs and body parts.

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What is the skeletal system? The skeletal system is your body's central framework. It consists of bones and connective tissue, including cartilage, tendons, and ligaments. It's also called the musculoskeletal system.