How does the digestive system and muscular system work together?

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• What is the digestive system?
• How does the digestive system work?
• What are common conditions related to the digestive system?
• Related information on Australian websites

What is the digestive system?

The digestive system is made up of the digestive tract and other organs that help the body break down and absorb food. It is a long, twisting tube that starts at the mouth and goes through the oesophagus, stomach, small intestine, large intestine and anus.

The digestive system breaks down food into nutrients such as carbohydrates, fats and proteins. They can then be absorbed into the bloodstream so the body can use them for energy, growth and repair. Unused materials are discarded as faeces (poo).

Other organs that form part of the digestive system are the pancreas, liver and gallbladder.

How does the digestive system work?

Each organ of the digestive system has an important role in digestion.

Mouth

When someone eats, the teeth chew food into very small pieces. Glands in the cheeks and under the tongue produce saliva that coats the food, making it easier to be chewed and swallowed.

Saliva also contains enzymes that start to digest the carbohydrates in food.

Oesophagus

The oesophagus is the muscular tube that carries food from the mouth to the stomach after it is swallowed. A ring of muscle at the end of the oesophagus relaxes to let food into the stomach and contracts to prevent stomach contents from escaping back up the oesophagus.

Stomach

The stomach wall produces gastric juice (hydrochloric acid and enzymes) that digests proteins. The stomach acts like a concrete mixer, churning and mixing food with gastric juice to form chyme — a thick, soupy liquid.

Small intestine

Bile from the gallbladder and enzymes in digestive juices from the pancreas empty into the upper section of the small intestine and help to break down protein into amino acids and fat into fatty acids. These smaller particles, along with sugars, vitamins and minerals, are absorbed into the bloodstream through the wall of the small intestine.

It is called small because it is about 3.5cm in diameter, but it is about 5m long to provide lots of area for absorption. Most of the chemical digestion of proteins, fats and carbohydrates is completed in the small intestine.

Large intestine and anus

The lining of the large intestine absorbs water, mineral salts and vitamins. Undigested fibre is mixed with mucus and bacteria — which partly break down the fibre — to nourish the cells of the large intestine wall and so help keep the large intestine healthy. Faeces are formed and stored in the last part of the large intestine (the rectum) before being passed out of the body through the anus.

What are common conditions related to the digestive system?

Gastro-oesophageal reflux

Gastro-oesophageal reflux (GORD) occurs when acidic stomach contents move from the stomach back up the oesophagus. It causes a burning sensation in the chest or throat.

Diverticulitis

Diverticulitis is caused by inflammation or infection of abnormal pouches in the lower part of the large intestine. It can cause mild or severe pain on the lower left-hand side of the abdomen.

Stomach ulcers

Stomach ulcers are commonly caused by the bacterium Helicobacter pylori that can live in the stomach of about 4 in 10 Australians. They can cause long-term, low-level inflammation of the stomach lining in some people. It is not well understood why they cause stomach ulcers in some people and not in others.

Haemorrhoids

Haemorrhoids are itchy or painful lumps that occur in and around the anus. The lumps contain swollen blood vessels. Haemorrhoids can cause bleeding when you go to the toilet (do a poo) — you might notice bright red blood on the toilet paper or in the toilet. If you find blood on the toilet paper or in the toilet, always seek medical advice.

The human body contains trillions of cells, 78 different organs and more than 60,000 miles of blood vessels if you stretched them end-to-end. Incredibly, all of these cells, vessels and organs work together to keep you alive.

Each organ belongs to one of ten human body systems. These body systems are interconnected and dependent upon one another to function. Your heart does not beat unless your brain and nervous system tell it to do so. Your skeletal system relies on the nutrients it gains from your digestive system to build strong, healthy bones.

There are 10 body systems:

1. Circulatory
2. Respiratory
3. Nervous
4. Muscular
5. Skeletal
6. Digestive
7. Endocrine (hormones)
8. Lymphatic, or immune system
9. Reproductive
10. Integumentary (skin, hair)

A body system is a group of parts that work together to serve a common purpose. Your cardiovascular system works to circulate your blood while your respiratory system introduces oxygen into your body.

Each Body System Works with the Others

Each individual body system works in conjunction with other body systems. The circulatory system is a good example of how body systems interact with each other. Your heart pumps blood through a complex network of blood vessels. When your blood circulates through your digestive system, for example, it picks up nutrients your body absorbed from your last meal. Your blood also carries oxygen inhaled by the lungs. Your circulatory system delivers oxygen and nutrients to the other cells of your body then picks up any waste products created by these cells, including carbon dioxide, and delivers these waste products to the kidneys and lungs for disposal. Meanwhile, the circulatory system carries hormones from the endocrine system, and the immune system’s white blood cells that fight off infection.

Each of your body systems relies on the others to work well. Your respiratory system relies on your circulatory system to deliver the oxygen it gathers, while the muscles of your heart cannot function without the oxygen they receive from your lungs. The bones of your skull and spine protect your brain and spinal cord, but your brain regulates the position of your bones by controlling your muscles. The circulatory system provides your brain with a constant supply of oxygen-rich blood while your brain regulates your heart rate and blood pressure.

Even seemingly unrelated body systems are connected. Your skeletal system relies on your urinary system to remove waste produced by bone cells; in return, the bones of your skeleton create structure that protects your bladder and other urinary system organs. Your circulatory system delivers oxygen-rich blood to your bones. Meanwhile, your bones are busy making new blood cells.

Working together, these systems maintain internal stability and balance, otherwise known as homeostasis. Disease in one body system can disrupt homeostasis and cause trouble in other body systems. If you become ill with the AIDS virus that affects your immune system, for example, you may develop pneumonia in your respiratory system, a yeast infection in your reproductive system, Candida that affects your esophagus in your digestive system or the skin cancer known as Kaposi’s sarcoma.

For more information on the connection between body systems, talk to your health professional at Revere Health. We offer family practice and 39 medical specialties to help all ten of your body systems work together. 

Sources:
Organs of the Body
Cleveland Clinic
AIDS.org