The Human Body Systems

Getting to know the human body. By Jessie Ocana

The digestive system

  1. The digestive systems function is to digest and absorb. Digestion is the breakdown of food into small molecules, which are then absorbed into the body. The digestive tract is a continuous tube with two openings: The mouth and the Anus. It includes the mouth, pharynx, esophagus, stomach, small intestine, and large intestine.
  2. Function(s) of the:
Mouth: The mouth is the beginning of the digestive tract and digestion starts when taking the first bite of food. Chewing breaks the food into smaller pieces that are more easily digested, while saliva mixes with the food to begin the process to begin breaking it down into a form that your body can absorb and use.

Esophagus: This body part only sees one important function in the body- to carry food, liquids, and saliva from the mouth to the stomach.

Stomach: The stomach secretes acid and enzymes that digest food. Ridges of muscle tissue called rugae line the stomach. The stomach muscles contract periodically, churning food to enhance digestion.

Small intestines: The small intestine is the part of the intestines where 90% of the digestion and absorption of food occurs, the other 10% taking place in the stomach and large intestine. The main function of the small intestine is absorption of nutrients and minerals from food.

Large Intestines: The major function of the large intestine is to absorb water from the remaining indigestible food matter and transmit the useless waste material from the body.

Anus: The anus is the last part of the digestive system. The anus consists of the pelvic floor muscles and the two anal sphincters( the internal and external).

Liver: The livers main function is too process the nutrients absorbed by the small intestines. The liver is also the bodies chemical "factory." It takes the raw materials absorbed by the intestine and makes all the various chemicals the body needs to function.

Pancreas: The pancreas secretes digestive enzymes into the duodenum, the first segment into the small intestine. These enzymes break down protines, fats, and carbohydrates.

Gallbladder: The gallbladder stores and concentrates bile, and then releases it into the duodenum to help absorb and digest fats.

The important things

Why is digestion of large food molecules is essential?

There are two reasons why the digestion of large food molecules is vital. Firstly, the food we eat is made up of many compounds made by other organisms which are not all suitable for human tissues and therefore these have to be broken down and reassembled so that our bodies can use them. Secondly, the food molecules have to be small enough to be absorbed by the villi in the intestine through diffusion, facilitated diffusion or active transport and so large food molecules need to be broken down into smaller ones for absorption to occur.

Why are enzymes needed in digestion?

Enzymes are needed in the process of digestion as they are the biological catalysts which break down the large food molecules into smaller ones so that these can eventually be absorbed. Digestion can occur naturally at body temperature, however this process takes a very long time as it happens at such a slow rate. For digestion to increase in these circumstances, body temperature would have to increase as well. However this is not possible as it would interfere with other body functions.This is why enzymes are vital as they speed up this process by lowering the activation energy required for the reaction to occur and they do so at body temperature.

Major Disorders within these systems



Ulcers damage the lining of the stomach because of bacterial infections or adverse side effects of medications such as aspirin, ibuprofen or naporoxen, according to the National Digestive Diseases Information Clearinghouse. Spicy foods and stress may aggravate ulcers, but do not cause them. Antibiotics or antacids usually alleviate problems long enough for minor ulcers to heal.

Acid Reflux:

Heartburn or acid indigestion results in stomach acid backing up into the esophagus to create a burning sensation or sour taste in the mouth. Gastroesophageal reflux disease (GERD) affects people who suffer acid reflux symptoms more than twice a week. Acid reflux occurs because the lower esophageal sphincter does not close properly. Some people may get more bouts of heartburn from certain foods, but each individual has different reactions to particular foods. Cigarette smoking contributes to heartburn by causing the esophageal sphincter to relax.


Kidney Stones:

Kidney stones are hard masses that form in the urinary tract from crystals that have separated from the urine. The most common type of kidney stone is formed from calcium, but other types include a struvite stone or uric acid stone, according to the National Kidney and Urologic Diseases Information Clearinghouse. The exact cause of kidney stones is unknown, but those with certain genetic disorders, kidney disorders and recurrent urinary tract infections are more likely to develop kidney stones. Symptoms of kidney stones include extreme pain, cramping in the back and lower abdomen, nausea and vomiting. Most kidney stones can be passed by increasing daily fluid intake to two to three quarts of water per day. If stones are too large to pass with an increase in water consumption, surgery may be needed to break the stones.


Urethritis is an inflammation of the urethra caused by a bacterial or viral infection. The infection can be caused by the same microbes that cause urinary tract infections, gonorrhea, chlamydia and herpes simplex. Symptoms of urethritis vary between the sexes. Symptoms in men include blood in the urine or semen, burning during urination, discharge, frequent urination, pain and swelling of the penis and pain during ejaculation. Symptoms in women include abdominal pain, pain during urination, fever, chills, frequent urination, pain in the pelvis and vaginal discharge, according to Medline Plus. Treatment for urethritis includes antibiotics or anti-viral medication. Pain medications may also be prescribed to reduce symptoms associated with urethritis. During treatment, sexual intercourse should be avoided.

The function of the Excretory system

The human excretory system functions to remove waste from the human body. This system consists of specialized structures and capillary networks that assist in the excretory process. The human excretory system includes the kidneys and their functional unit, the nephron. The excretory activity of the kidneys is modulated by specialized hormones that regulate the amount of absorption within the nephron.

Excretion: The act or process of discharging waste matter from the blood, tissues, or organs.