The Urinary System

(Renal System)

The Urinary system, also known as the renal system, is a group of organs in the body involved in eliminating wastes from the body through the process of filtration.

FUNCTIONS OF THE URINARY SYSTEM:

• Formation of urine.
• Elimination of urine.
• Removal of waste product from the body (urea and uric acid)
• Regulation of electrolyte balance (sodium, potassium and calcium)
• Maintain a steady acid – base homeostasis. Helps in the regulation of pH of the blood. Blood pH is controlled by maintaining the concentration of Carbonic acid (controlled by the Respiratory System) and Sodium Bicarbonate (controlled by kidneys). Carbonic acid and Sodium Bicarbonate form the most important buffer systems that maintain a relatively constant plasma pH.
• Helps in production of Red Blood Cells (RBC). The kidneys produce erythropoietin that helps produce red blood cells).
• Helps in maintaining blood pressure. The kidneys produce renin (a hormone important in regulating blood pressure).

 

PARTS OF URINARY SYSTEM AND THEIR FUNCTIONS:

1). KIDNEYS (enclosed in a renal capsule)

• Nephron (consists of Glomerulus and Tubules) – is the functional unit of the kidney.
• Medulla, Cortex, and Papillary Ducts – are the non-functional parts of the kidney.
• Glomerulus (enclosed in Bowman’s Capsule) – helps in filtering of fluids out of blood.
• Bowman’s Capsule – collects the fluids or waste products from Glomerulus.
• Tubules – are the Proximal Convulated Tubule, Henle’s loop, Distal Convulated Tubule and Collecting Duct. The fluid or waste filtered from the blood is converted into urine in the tubules.

Functions of Kidneys:

• Kidneys filter the blood.
• The kidneys excrete wastes.
• Kidneys regulate the balance of electrolytes.
• Kidneys control the body’s fluid balance.

2). URETER

• The ureters are narrow tubes measuring up to 18 inches long, that extend from the kidneys to the urinary bladder. There are two ureters, one attached to each kidney.
• The function of the ureters is to transport urine from the renal pelvis of the kidneys to the urinary bladder for storage before disposal by urination.
  

3). BLADDER

• The urinary bladder is pear shaped, muscular organ that is located in the lower abdominal region, above and behind the pubic bone.
• It is the organ that collects and stores urine excreted by the kidneys before it is expelled by urination.
• Total capacity of the urinary bladder is 700 ml to 1 liter.

4). URETHRA

• The urethra is the tube that connects the urinary bladder to the genita through which urine is eliminated from the body.
• Male Urethra – is 8 inches long, from the bladder to the tip of the penis. It is longer than the female Urethra. The male urethra serves as an exit for urine and for releasing semen during ejaculation.
• Female Urethra – is 2 inches long. Because female urethra is shorter than the male urethra, it is more prone to get infections from bacteria in the vagina. It serves solely for urinary elimination.

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