Urinary System

KIDNEYS

The urinary system of the human body consists of:

Two kidneys Two ureters Urinary bladder Urethra

Kidneys - Introduction Are a pair of bean-shaped, red-brown

organs Each is about 4 inches (10 cm) long, 2 inches (5 cm) wide, and 1 inch (2.5 cm) thick Each weighs about 5 ounces (140 g)

Function of the Kidneys

Main Function: Regulate the volume and concentration of

fluids and minerals in the body Remove the waste matter produced by the

normal functioning of the body Produce urine

Other Functions of the Kidneys:

Detoxify harmful substances (e.g. drugs, free radicals)

Secrete Renin (hormone that regulates blood pressure and electrolyte balance)

Produce Erythropoietin (hormone that stimulates red blood cell production in the bone marrow)

Increase the absorption of Calcium by producing Calcitriol (form of vitamin D)

Location of the Kidneys

On the posterior wall of the abdomen One on each side of the spine At the level of the lowest ribs (the right kidney in most people is

located slightly lower than the left

one because of the position of the liver)

Anatomy of the Kidney

Each kidney has:

An outer layer – the cortex An inner layer – the medulla Cuplike structures – the major and minor

calyces The renal pelvis

Anatomy of the Kidney (cont.)

The renal hilus (the exit point for the ureter, the location where nerves, blood and lymphatic vessels enter and exit)

A renal artery and arterioles A renal vein and capillaries A protective membrane – the renal

capsule (enclosing each kidney)

Anatomy of the Kidney (cont.)

Surrounding each capsule is a cushion of fatty tissue and a layer of connective tissue which attaches the kidneys to the back of the abdomen

On top of each kidney is adrenal gland

Anatomy of the Kidney (cont.)

The renal medulla contains 8-18 renal pyramids (their tips – renal papillae are facing towards the renal hilus, and their bases are aligned with the edge of the renal cortex)

Between each pyramid

are renal columns

Anatomy of the Kidney (cont.)

The functional units of the kidneys are nephrons – about 1.2 million in each

kidney – filter the blood – produce a liquid (the filtrate) containing minerals, wastes, and water

Structure of the Nephron

Structure of the Nephron

Glomerulus – extensive ball-shaped capillary network

The Bowman’s capsule – a double-walled cup of epithelial tissue surrounding the glomerulus

The Bowman’s capsule and glomerulus together form the renal corpuscle

Structure of the Nephron (cont.)

Proximal convoluted tubule – coiled region of the tube

Loop of Henle Distal convoluted tubule Collecting duct

The Nephron at Work

Blood enters the glomerulus via the afferent arteriole and exits through the efferent arteriole

Endothelial-capsular membrane of the renal corpuscle filters water and substances from the blood into the nephron

The Nephron at Work (cont.) The filtrate passes into the renal tubule

A network of the peritubular capillaries reabsorbs useful substances from the filtrate and secretes additional wastes into it

About 99 percent of the filtrate is reabsorbed and returned to the blood circulation.

Urine About 1 percent of the filtrate (1-11/2 liters

a day) collects in the renal pelvis and forms urine

Urine exits the kidney via left and right ureters

Is transported to the bladder Leaves body through the urethra

Facts About Urine

The volume of urine formed at night is about half that formed during the day

Normal urine is sterile The tissue of the bladder wall is isolated

from urine and toxic substances by a coating that discourages bacteria from growing there

Pathology of the Kidney Acute tubular necrosis (ATN) – damage

to the renal tubules caused by toxins or ischemia

Diabetic nephropathy – damage to the glomerulus capillaries due to high blood sugar

Glomerulonephritis – inflammation of the glomerulus

Pathology of the Kidney (cont.)

Hydronephrosis – distention of the renal pelvis due to urine collection caused by obstruction

Nephrolithiasis – presence of calculi (stones) in the kidney

Nephrotic syndrome (NS) – damage to the glomerulus

Pathology of the Kidney (cont.)

Nephroptosis – downward displacement of the kidney ( a floating kidney)

Polycystic kidneys – multiple cysts within the kidney tissue

Pyelonephritis – inflammation of the renal pelvis and the kidney

Pathology of the Kidney (cont.)

Renal cell carcinoma – cancerous tumor of kidney tubule cells

Renal failure – inability of the kidneys to filter wastes from the blood

Wilm’s tumor – malignant kidney tumor (often in children)

Renal Replacement Therapies

Hemodialysis – blood is allowed to flow, a few ounces at a time, through a special machine with a filter (dialysis machine) that removes harmful wastes, extra salt, and extra fluids. The clean blood is then returned to the body.

Hemodialysis

Hemodialysis Equipment

Renal Replacement Therapies (cont.) Peritoneal dialysis – a dialysis fluid is

entered into the patient’s abdominal cavity, which is covered by a thin membrane (peritoneum), containing many small vessels. The peritoneum works as a dialysis filter, and the dialysis fluid makes water, salt, and the waste products move from the blood into the fluid.

PeritonealDialysis

Renal Replacement Therapies(cont.)

Renal transplant – an operation that places a healthy kidney in the body. The transplanted kidney takes over the work of the two kidneys that failed.

Sources

MedicineNet.com. Hemodialysis (cont.) How Hemodialisis Works.Retrieved June11, 2009, from http://www.medicinenet.com/hemodialysis/page2.htm

Wikipedia, the free encyclopedia (Last modified: June 3, 2009). Peritoneal Dialysis. Retrieved June 11, 2009, from http://en.wikipedia.org/wiki/Peritoneal_dialysis

Health & Wellness REMEDY Life. Renal system Anatomy. Retrieved June 15, 2009, from http://www.nephrologychannel.com/anatomy.shtml

Fremgen, Bonie F., Frucht, Suzanne S. Medical Terminology: a living language (4th.ed.). Pearson Education, Inc.