THE URINARY SYSTEM The anatomy The functions

The functions of the system To filter the blood and form urine. To remove waste products. To reabsorb nutrients, acids, trace elements and water as required. To work together with the Endocrine and cardio vascular and digestive systems in the regulation of fluids, blood cells, electrolytes, minerals and hormones in the body.

The anatomy consists of : Two kidneys. Two ureters 1 bladder 1 urethra

The kidneys 1.The kidneys are surrounded by an outer fibrous renal capsule. 2. Underneath this is found the cortex in which is found visceral connective tissue, blood vessels and capillaries. 3. Underneath this is found the medulla, containing the renal pyramids with arcuate arteries and veins and interlobular vessels. 4. Within the pyramids are located the nephrons or filtering units. 5. At the base of the pyramids are located the minor and major calyxes. These are part of the renal pelvis, which eventually gives way to the ureter. 6. The pelvis is found in an area of the kidney known as the hilus where the ureters, renal vein and arteries enter and exit.

Within each pyramid are found thousands of nephrons. Each one with its own set of convoluted tubules. 1 Proximal tubule 2.Loop of Henle 3. Distal tubule 4. Collecting duct. These structures are surrounded by capillaries. At the top end, the distal tubule divides to form the Bowmans Capsule. Which houses The Glomerulus, a collection of specialised capillaries which filter the blood. The Nephron

The Glomerulus The Glomerulus is fed by an arteriole, bringing blood to be filtered under pressure into the Bowman’s capsule from where it passes into the proximal tubule. The capillaries have special cells which are called podocytes, they look as if they have legs which pass around the vessel, assisting in the filtration process. Large molecules and blood cells will remain in the blood stream. The glomerulus is unusual as it is both fed and drained by an arteriole

Formation of Urine This takes place in three phases : 1.Simple Filtration Blood is filtered under pressure through the glomerulus into the bowmans capsule and proximal renal tubule. This will be a mixture of water, sodium, potassium,acids bicarbonate and urea. Components staying in the glomerulus include plasma proteins, corpuscles and other large molecules 2. Selective re absorption As the filtrate passes on and into the loop of Henle and distal renal tubule, the filtrate will be altered by hormonal messages, osmotic pressure and feed back systems connected to the endocrine, cardio vascular and respiratory systems. 3. Secretion At the collecting tubule end, the resultant urine will pass down and into the renal pelvis before eventually descending with the assistance of peristaltic action into the bladder

Urine WATER96% UREA2% URIC ACID CREATINE AMMONIA SODIUM POTASSIUM 2% CHLORIDES PHOSPHATES SULPHATES OXALATES

URETERS, BLADDER, URETHRA The ureters are long three layer muscular tubes which convey the urine from the kidney and to the bladder. The bladder is described as a pear shaped organ. The peritoneum covers the superior surface and posteriorly it is surrounded by the uterus in the female and the rectum in the male. It has three layers, the outer is loose connective tissue and the middle is smooth muscle and elastic fibres. The innermost layer is transitional epithelium.It can contain from 300mls to 800mls of urine. When the bladder is empty it forms into folds called ruggae and when full takes on a smooth appearance. The three orifices form a triangle called the trigone. The lower orifice leads into the urethra and the internal sphincter which is not under conscious control.

THE MALE AND FEMALE PELVIC CAVITIES The Urethra is a canal which extends from the bladder to the outside. In women it is around 4 inches long and in men it extends through the penis, surrounded by the prostate gland and the erectile tissues. The external orifice is guarded by another sphincter muscle which is under conscious control.

SOME DISEASES AND DISORDERS Cystitis: This is inflammation of the bladder, which causes pain when urinating. This is usually as a result of an infection. It is more common in women than men where the urethra is far shorter and closer to the other orifices. It can be very debilitating and reoccur. Nephritis or Bright’s disease: This is inflammation of the filtration units of the kidneys, where it includes the glomerulus it is known as Glomerula nephritis. This can become a very troublesome disorder and again very painful with pain radiating out and around to the groin and lower abdominal areas. Both the above are aided by hydration. Kidney stones: This is caused by oxalates and calcium deposits which form over a period of time within the kidney, renal pelvis and bladder. These can be extremely painful if passed and attempts to dissolve them en situ are far more preferable. Diabetes Insipidus : This is caused by lack of ADH and leads to very frequent urination, leading to a build up of toxins in the body. Cancer : It is worth noting that cancers of the bladder and kidneys can often be secondary to prostate cancer.