Urinary System PDF

Functions of kidney 1- Regulation of total body It consists of: water. 1-Kidneys. 2- maintenance of the 2-Ureters. extracellular fluid. 3- Excretion of waste 3-Urinary products of metabolism. bladder. 4-...

Functions of kidney 1- Regulation of total body It consists of: water. 1-Kidneys. 2- maintenance of the 2-Ureters. extracellular fluid. 3- Excretion of waste 3-Urinary products of metabolism. bladder. 4-Regulation of blood 4-Urethra. pressure The kidney The kidneys are paired organs the kidney consists of an outer dark stained cortex and an inner pale medulla The structural and functional unit of the kidney is the nephron  The nephron Each nephron is formed of: -Bowman's capsule. -Proximal convoluted tubule. -Loop of Henle which consists of: a. Descending segment. b. Ascending segment. -Distal convoluted tubule.  RENAL CORPUSCLES The proximal end of each nephron is expanded to form the Bowman's capsule. This capsule is indented by a globular tuft of capillaries called the glomerulus. The tuft of capillaries with its surrounding Bowman's capsule form the renal corpuscle. Each renal corpuscle has 2 poles: a vascular pole and a urinary pole. RENAL CORPUSCLES  Bowman's capsule It is a double walled cup, formed of a parietal and visceral layers separated by Bowman's space. The parietal layer is lined by a single layer of squamous epithelium. The visceral layer dips inward between the capillary lobules. The cells lining this layer are called podocytes.  Podocytes The podocytes are stellate in shape. They give many primary processes, which in turn give secondary processes (foot processes or pedicles). These pedicles make intimate contact with the basement membrane of blood capillaries. The pedicles of adjacent podocytes are separated by narrow spaces or filtration slits (25 nm) closed by "filtration slit membrane".  The filtration barrier This barrier is present between the blood circulating in the capillaries and the filtrate in the capsular spaces. The barrier consists of: 1-The fenestrated endothelium. 2-The basement membrane. 3-The filtration slit membrane.  Proximal convoluted tubules Distal convoluted tubules P.C.T. D.C.T. 1- The P.C.T. is lined with simple 1- The D.C.T. is lined with shorter cuboidal epithelium. cuboidal cells. 2- They have brush borders. 2- No brush border. 3- The cytoplasm is granular and deeply 3- Less granular & Less acidophilic acidophilic. cytoplasm. 4- The basal part of the cytoplasm show 4- less basal striations. vertical acidophilic striation. 5- The number of the cells is larger (5- 5- Only 3-5 nuclei appear in a cross 8). section. 6- The cell borders are more 6- The cell border is ill defined. distinguishable. Juxtaglomerular apparatus Some modifications in the wall of the afferent arteriole, and in the portion of the distal convoluted tubule which lies in contact with the renal corpuscle. A) Modification in the afferent arteriole: 1- The media of the wall of the arteriole is differentiated into epilheloid cells (Juxtaglomerular cells): The nuclei become rounded. The cytoplasm contains granules (renin or its precursor) instead of myofibrils.  B) Modification in the distal convoluted tubule:in contact with renal corpuscle. The basement membrane is lost. The cells become taller, columnar and crowded. The nuclei become deeply stained and close together. These cells are called macula densa. C) The area between the macula densa, the glomerulus and the afferent arterioles is occupied by small pale cubodial cells called extra glomerular mesangial cells. The function of the juxtaglomerular apparatus: The different components of the juxtaglomerular apparatus play a role in control the blood Thank you