Urinary System. Dr. Ahmed Maher Dr. Ahmed Manhal

Transcription

1 Urinary System Dr. Ahmed Maher Dr. Ahmed Manhal

2 Presentation Map Kidney (cortex & medulla). Nephron. Duct system. Juxtaglomerular apparatus. Ureter, bladder & urethra.

3 Definition & General Structure The system which eliminates waste products of the body and maintains fluid/salt balance. It consists of paired kidneys & ureters and unpaired urinary bladder and urethra. Most of the functions are preformed in the kidneys.

4 The Kidney Two reddish bean shape structures each one is surrounded by a thick C.T. capsule. Located in the abdominal cavity. The right kidney is pushed downwards by the liver, so the left one is 1-2 cms higher. It s divided to outer cortex and inner medulla.

5 The Cortex Dark brown granular appearance. 5 mm thick. Contains glomeruli & convoluted tubules. Medullary rays; coming from medulla, are recognized here. Between two rays is a region called cortical labyrinth. The medullary ray and its surrounding cortical labyrinth form the LOBULE.

6 Renal Cortex

7 The Medulla Organized as multiple medullary pyramids with the base towards the cortex. Each pyramid and its associated cap of cortical tissue is known as LOBE. Contains Henle s loop, collecting tubules and ducts.

8 Renal Medulla

9 The Nephron It s the structure responsible for urine formation. Consists of the renal corpuscle, proximal convoluted tubule, Henle s loop and distal convoluted tubule. There are two types of nephrons: cortical & juxtamedullary nephrons.

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11 The Renal Corpuscle The point at which the nephron starts. All renal corpuscles lie within the renal cortex. It consists of Bowman s capsule and the glomerulus.

12 Bowman s Capsule The part of renal corpuscle than envelopes the glomerulus. It consists of two layers. Outer parietal layer. Inner visceral layer. Between these two layers is the urinary space.

13 The Glomerulus The capillary bed found within Bowman s capsule of the renal corpuscle. It begins with afferent arteriole and forms efferent arteriole. The process of filtration takes place in the glomerulus.

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15 Filtration Mechanism Movement of fluid from vascular glomerulus across the filtration barrier into the urinary space. The endothelium, basement membrane & podocytes prevent formed elements of blood and other molecules from passing with the filtrate.

16 The Proximal Convoluted Tubule PCT is longer & wider than DCT. Cuboidal \ truncated pyramid cells. Acidophilic cytoplasm. The cells form brush border on the apex. The apical part of the cells contain canaliculi that increase the absorbance potency of the cell.

17 Henle s Loop U shaped structure that lies within the medulla. Responsible for water retention. Begins at the end of PCT & ends at the beginning of DCT. Consists of: 1. Thick descending arm. 2. Thin descending arm. 3. Thin ascending arm. 4. Thick ascending arm.

18 The Descending Arm The thick arm is similar to PCT. It narrows to form the thin arm. The thin arm is lined with simple squamous epithelium; therefore, it has a wide lumen.

19 The Ascending Arm The thin arm is only found in juxtamedullary nephrons and it s similar in structure to the thin descending arm. The thick arm is similar in structure to the DCT. Responsible for sodium & chloride absorption from urine.

20 The Distal Convoluted Tubule Lies within the cortex. Tortuous course with simple cuboidal epithelium lining. Has no brush borders in the apices of the cells. No canaliculi. Responsible for ion transportation.

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22 Collecting Tubules & Ducts The collecting tubule begins at the end of DCT. Collecting tubules join each other to form collecting ducts. The collecting ducts form the papillary ducts near the tips of medullary pyramids. The lining begins as simple cuboidal and ends as simple columnar.

23 Juxtaglomerular Apparatus Consists of 1. macula densa of DCT. 2. Juxtaglomerular cells 3. Lacis cells (extraglomerular mesangial cells). This apparatus participates in controlling blood pressure through some hormones secretions.

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25 Macula Densa Formed by DCT when it approaches the glomerulus. Have a columnar (instead of cuboidal) cells which are densely packed together. It secretes the hormone renin which takes a part in blood pressure control.

26 Juxtaglomerular Cells Formed by tunica media of the afferent arteriole. Have round nuclei. Also takes a part in blood pressure control.

27 Lacis Cells Bounded by: 1. Afferent & efferent arterioles. 2. Macula densa. 3. Glomerulus. The function of these cells isn t well defined yet.

28 The Ureter Composed of: 1. folded mucus membrane. Transitional epithelium. Lamina propria. 2. Smooth muscle coat. 3. Fibro-elastic adventitia. There is no sub mucosa.

29 Urinary Bladder Composed of the same layers of ureter, but the muscular layer is much thicker. It stores urine until its excreted outside the body.

30 Transitional Epithelium It has the ability to: 1. Stretch and yet maintain a strong barrier that prevents diffusion of urine components. 2. Change the number of layers. 3. Change the shape of cells. Outer cells are umbrella shape. Mid layers cells are polygonal in shape. When stretched, the cells become squamus in shape and the number of layers is decreased.

31 Urethra The last part of the urinary system. It passes from the bladder to the exterior. Composed of: 1. Mucosa. 2. Sub mucosa. 3. Muscular coat. 4. Adventitia.

32 Thank You