Page 10 - 84 human physiolofy part-1

Chapter 1

Respiratory System

The respiratory system works in conjunction with the cardiovascular system to provide oxygen to
cells within every body system for cellular metabolism. The respiratory system also removes carbon
dioxide. Since CO2 is mainly transported in the plasma as bicarbonate ions, which act as a chemical
buffer, the respiratory system also helps maintain proper blood pH levels a fact that is very important
for homeostasis. As a result of hyperventilation, CO2 is decreased in blood levels. This causes the pH
of body fluids to increase. If acid levels rise above 7.45, the result is respiratory alkalosis. On the other
hand, too much CO2 causes pH to fall below 7.35 which results in respiratory acidosis. The respiratory
system also helps the lymphatic system by trapping pathogens and protecting deeper tissues within.
Note that when you have increased thoracic space it can provide abdominal pressure through the
contraction of respiratory muscles. This can assist in defecation. Remember the lungs are the gateway
for our breath of life.

Digestive System

Without a regular supply of energy and nutrients from the digestive system all body systems would
soon suffer. The digestive system absorbs organic substances, vitamins, ions, and water that are needed
all over the body. In the skin the digestive tract provides lipids for storage in the subcutaneous layer.
Note that food undergoes three types of processes in the body: digestion, absorption, and elimination. If
one of these is not working, you will have problems that will be extremely noticeable. Mechanics of
digestion can be chemical digestion, movements, ingestion absorption, and elimination. In order to
maintain a healthy and efficient digestive system we have to remember the components involved. If
these are disturbed, digestive health may be compromised.

Urinary System

Toxic nitrogenous wastes accumulate as proteins and nucleic acids are broken down and used for
other purposes. The urinary system rids the body of these wastes. The urinary system is also directly
involved in maintaining proper blood volume (and indirectly blood pressure) and ion concentration
within the blood. One other contribution is that the kidneys produce a hormone (erythropoietin) that
stimulates red blood cell production. The kidneys also play an important role in maintaining the correct
water content to of the body and the correct salt composition of extracellular fluid. External changes
that lead to excess fluid loss trigger feedback mechanisms than they act to maintain the body's fluid
content by inhibiting fluid loss.

Reproductive System

The Reproductive System is unique in that it does little to contribute to the homeostasis of the
organism. Rather than being tied to the maintenance of the organism, the reproductive system relates to
the maintenance of the species. Having said that, the sex hormones do have an effect on other body
systems, and an imbalance can lead to various disorders (e.g. a woman whose ovaries are removed
early in life is at much higher risk of osteoporosis).

10 | Human Physiology