The digestive system is in charge of breaking down complex food particles into small molecules that can be transported in the blood plasma. It involves ingestion (taking in food), digestion (breaking down food), and absorption (passing nutrients from the digestive tract to blood stream). Chemicals such as mucin (which line the walls of the stomach to protect it from the acid) and rennin (which aids in the coagulation and digestion of milk proteins) are involved in this complex process. The end result is urine and solid waste.

Circulation of blood allows the transportation of some waste products. The liver takes excessive amino acids from the excess protein out of the blood and removes the amino groups in order to convert the rest of the molecule into a useful form for energy production by body cells. Pancreatic hormones such as insulin,

There are 2 groups of lymphacytes called T-cells (thymus) and B-cells (Bursa). T-cells rapidly produce and kill invading organisms by having the correct antibody embedded on its plasma membrane as it comes in direct contact with the organisms. B-cells produce and secretes antibodies against invading antigens.

Some diseases that affect the digestive tract are cirrhosis of the liver (portions of the liver enlarge then shirk then harden. This is then replaced by scar tissue.) gallstones (bile so concentrated that it solidifies) and peptic ulcers (inflammation and death of the membranes covering the intestinal walls of the stomach.).

In the respiration system, air enters the respiratory system either through two nasal cavities or the mouth. The nasal cavities open into an air-filled channel into the mouth, called the pharynx. Two openings branch from the pharynx - the trachea and the esophagus. Air is carried down the trachea to the larynx. From there, the airway branches into two bronchi. The bronchi is carried into smaller airways called bronchioles. Air moves from the bronchioles into tiny-blind-ended sacs called alveoli. In the alveoli, gas diffuse between the air and blood accordingly to concentration gradients.

The respiratory tract starts through the nose, or through the mouth. It is a very well-known fact that ingestion also starts in the mouth. The pharynx is lined with a musous membrane for further cleansing. It serves as a common passage for both the respiratory and the digestive tract. While food goes down the esophagus, air flows down the trachea. That air enters the lungs, the oxygen is passed through into the blood stream to be transported where needed to perform things such as the liver to produce bile and other organ systems.

O2 is crucial for energy in cells. In turn, the body's transportation system must deliver and remove materials at a suitable rate is the cells are to function effectively. The energy is supplies by attaching the phosphate group from a molecule of ATP to the glucose phosphate. Muscle cells enter lactic acid fermentation during vigorous or prolonged activity when the circulation cannot deliver sufficient O2 to meet the demand. The gradual accumulation interferes with the cells activity, causing cramps.

Some common words found in the essay are:
, O2 CO2, Enzyme System, CO2 H2O, Nephritis Bright's, Antibodies Killer, T-cells B-cells, FUNCTIONS Monocytes, Bursa T-cells, Type B, immune system, blood cells, circulatory system, white blood cells, white blood, blood stream, blood pressure, krebs' cycle, digestive tract, cellular respiration, body energy, system immune system, functioning properly reabsorb, kidneys functioning properly, glucose blood stream,
Approximate Word count = 2724
Approximate Pages = 11 (250 words per page double spaced)