URINARY SYSTEM

  The urinary system plays a major role in the elimination of waste from the body. The urinary system is also called the excretory system that produces, stores, and eliminates urine. It also regulates the volume and chemical composition of blood by selectively adjusting the amounts of water and electrolytes in the body. In addition to this excretory function, the urinary system performs endocrine activities by secreting substances into the bloodstream that produce specific effects on the body. Erythropoietin produced by kidneys stimulates the production of red blood cells in the bone marrow. Renin, also produced by kidneys is an enzyme that regulates blood pressure.

While the female reproductive system is separate from the urinary system, the male reproductive system has some structures that are part of both the urinary and the reproductive system. When discussed together, these structures are referred as the genitourinary system. The medical study of the genitourinary system is known as urology. A physician who deals with and treats genitourinary disorders is known as an urologist. Nephrology is a related specialty that deals with the structure and conditions of the kidney. Nephrologists diagnose and treat conditions associated with the kidneys.

 THE URINARY SYSTEM

 The urinary system or the urinary tract consists of 2 kidneys, 2 ureters, 1 bladder, and 1 urethra. The kidneys produce urine by filtering blood off its waste products like urea, uric acid, and creatinine and dissolving it in water. Urine also contains excessive electrolytes and salts. This urine is then transported to the urinary bladder through the ureters where it is stored until eliminated out of the body through the urethra.

THE KIDNEYS

 The kidneys are reddish-brown, bean-shaped, organs located on either side of the vertebral column at the back of the upper abdominal cavity, just below the costal margin. The kidneys are about the size of a human fist. The kidneys receive blood supply from the abdominal aorta. Each kidney is roughly 10 cm long and 5 cm wide.

Each kidney is surrounded by a thick cushion of perinephric fat, which is covered by a fibrous connective tissue. This cushion provides protection and support to the kidney and anchors it to the body wall.

The kidneys perform a number of tasks 

• Elimination of wastes 

• Maintain body homeostasis by regulating volume of water and electrolytes and blood 

• Maintain acid-base homeostasis by regulating pH balance 

• Produce erythropoietin that stimulates production of red blood cells 

• Produce renin that regulates blood pressure

Three major regions can be distinguished when studying the anatomy of the kidney 

• The outer cortex containing millions of nephrons

• The inner medulla containing collecting tubules

• The renal pelvis that leads to the renal hilum – the point of entry and exit into the kidneys