Page 186 - 84 human physiolofy part-1

Chapter 10

10 THE URINARY SYSTEM

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Introduction

T he Urinary System is a group of organs in the body concerned with filtering out excess fluid and

other substances from the bloodstream. The substances are filtered out from the body in the form
of urine. Urine is a liquid produced by the kidneys, collected in the bladder and excreted through the
urethra. Urine is used to extract excess minerals or vitamins as well as blood corpuscles from the body.
The Urinary organs include the kidneys, ureters, bladder, and urethra. The Urinary system works with
the other systems of the body to help maintain homeostasis. The kidneys are the main organs of
homeostasis because they maintain the acid base balance and the water salt balance of the blood.

Functions of the Urinary System

One of the major functions of the Urinary system is the process of excretion. Excretion is the
process of eliminating, from an organism, waste products of metabolism and other materials that are of
no use. The urinary system maintains an appropriate fluid volume by regulating the amount of water
that is excreted in the urine. Other aspects of its function include regulating the concentrations of
various electrolytes in the body fluids and maintaining normal pH of the blood. Several body organs
carry out excretion, but the kidneys are the most important excretory organ. The primary function of
the kidneys are to maintain a stable internal environment (homeostasis) for optimal cell and tissue
metabolism. They do this by separating urea, mineral salts, toxins, and other waste products from the
blood. They also do the job of conserving water, salts, and electrolytes. At least one kidney must
function properly for life to be maintained. Six important roles of the kidneys are:

Regulation of plasma ionic composition. Ions such as sodium, potassium, calcium, magnesium,
chloride, bicarbonate, and phosphates are regulated by the amount that the kidney excretes.

Regulation of plasma osmolarity. The kidneys regulate osmolarity because they have direct
control over how many ions and how much water a person excretes.

Regulation of plasma volume. Your kidneys are so important they even have an effect on your
blood pressure. The kidneys control plasma volume by controlling how much water a person excretes.
The plasma volume has a direct effect on the total blood volume, which has a direct effect on your
blood pressure. Salts such as NaCI can cause osmosis, the diffusion of water into the blood.

Regulation of plasma hydrogen ion concentration (pH). The kidneys partner up with the lungs
and they together control the pH. The kidneys have a major role because they control the amount of
bicarbonate excreted or held onto. The kidneys help maintain the blood Ph mainly by excreting
hydrogen ions and reabsorbing bicarbonate ions as needed.

Removal of metabolic waste products and foreign substances from the plasma. One of the
most important things the kidneys excrete is nitrogenous waste. As the liver breaks down amino acids it
also releases ammonia. The liver then quickly combines that ammonia with carbon dioxide, creating

186 | Human Physiology