Lesson # 20

1. Lesson # 20 The Urinary System-1 Chapter 26 Objectives: 1- Describe the organs of the urinary system .2- Describe the location and structural features of the kidneys.3- Describe the structure of a nephron. 4-Trace the path of the blood flow through a kidney. 5- Describe the structure of ureter, urinary bladder and urethra.

2. Functions of the Urinary System 1- Regulates blood composition and blood pressure, as well as body fluid composition and volume. 2- Regulates blood pressure by releasing rennin, which activates the rennin-angiotensin mechanism that raises the blood pressure. 3- Regulates some metabolic reactions by converting vitamin D to its active form. 4- Releases erythropoietin, which increases production of red blood cells. 5- Helps to regulate blood pH by controlling the loss of hydrogen and bicarbonate ions in the urine. 6- Helps to regulate calcium ion levels by producing calcitriol.

3. Overview of the Urinary System

4. T11 T12 L1 L2 L3 The Kidneys Location • The kidneys lie against posterior abdominal wall at level of T12 to L3. • They are retroperitoneal along with ureters, urinary bladder, renal artery and vein, and adrenal glands.

5. Parietal peritoneum Renal fascia Adipose capsule Renal capsule External Anatomy of the Kidneys Stomach Pancreas Hylus Renal artery Spleen Renal vein Kidney Ureter It anchors the kidney to the abdominal wall. It helps protect the kidneys from trauma and maintains the kidneys in place. It protects the kidneys from trauma and infections.

6. Renal column Cortex Medulla Renal pyramids Renal sinus Renal lobe Minor calyx Major calyx Ureter Renal pelvis Sectional Anatomy of the Kidneys Blood vessels Parenchyma Renal papilla

7. Afferent arteriole Afferent arteriole Venules Efferent arteriole Peritubular capillaries Arcuate artery Nephron Interlobar artery Interlobar vein Interlobular or cortical radiate arteries Interlobular or cortical radiate veins Interlobular or cortical radiate arteries Interlobular or cortical radiate veins Segmental artery Renal artery Renal vein Blood Supply of the Kidney Arcuate vein Arcuate vein

8. Cortical nephron Glomerulus Afferent arteriole Juxtamedullary nephron Venule Efferent arteriole Cortex It receives most of the total renal blood flow Peritubular capillaries Cortical radial vein Cortical radialartery Corticomedullary junction Arcuate artery Arcuate vein Medulla It receives 1% to 2% of the total renal blood flow Vasa recta

9. Flow Chart of Renal Circulation Aorta Inferior vena cava Renal a. Renal v. Segmental a. Interlobar a. Interlobar v. Arcuate a. Arcuate v. Cortical radiate a. Cortical radiate v. Afferent arteriole Peritubular capillaries Vasa recta Juxtamedullary nephron Glomerulus Efferent arteriole

10. The Nephron The nephrons are the functional units of the kidneys. Each kidney has about 1.2 million nephrons Renal Corpuscle - Glomerulus Parietal layer (simple squamous epithelium) - Glomerular (Bowman) capsule Visceral layer (podocytes) Capsular space Renal Tubule Nephron Renal Tubule Proximal convoluted tubule (PCT) Distalconvoluted tubule (DCT) Renal Corpuscle - Proximal convoluted tubule (PCT) - Nephron loop (loop of Henle) - Distal convoluted tubule (DCT) Glomerulus The Collecting System Glomerular capsule The collecting duct receives fluids from the distal convoluted tubules of several nephrons as it passes back into the medulla. Collecting duct (CD) • Numerous collecting ducts converge toward the tip of the medullary pyramid to form a papillary duct. Nephron loop (loop of Henle) About 30 papillary ducts end in the tip of each papilla

11. Nephron Renal tubule Renal corpuscle Collecting duct Connecting tubules

12. Bowman’s capsule Parietal layer (Simple squamous epithelium) Glomerulus Arterial capillaries (Fenestrated endothelium) Pedicels & filtration slits Visceral layer (Podocytes) The Renal Corpuscle Efferent arteriole Capsular space Filtrate Proximal convoluted tubule Distal convoluted tubule Afferent arteriole

13. Fenestrated endothelium of capillaries The Filtration Membrane Podocytes Capsular Space Filtration slits Pedicels Dense layer Pedicels Filtration slits Filtrate Fenestrated endothelium of capillaries Filtrate Blood Mesangial cells They control the capillary diameter and the rate of capillary blood flow. Capsular Space Blood Capsular epithelium Filtration Membrane: Visceral layer 1- Fenestrated endothelium of glomerular capillaries 2- Dense layer 3- Filtration slits Capsular epithelium

14. The Juxtaglomerular Complex Juxtaglomerular Complex: 1- Macula densa They contain chemoreceptors that monitor the concentration of sodium. If the flow of tubular fluid increases and sodium concentration decreases, the macula densa stimulates JG cells contract which constricts afferent arteriole, reducing the glomerular filtration. Proximal convoluted tubule (PCT) Distal convoluted tubule (DCT) Renal Corpuscle 2- Juxtaglomerular cells Distal convoluted tubule (DCT) They contain mechanoreceptors that monitor blood pressure and volume. They contain granules of renin. Afferent arteriole Collecting duct (CD) If blood pressure decreases, the renin is released producing a vasoconstriction that raises the blood pressure. Nephron loop (loop of Henle)

15. The Renal Tubule Proximal convoluted tube Distal convoluted tube Connecting tubule Collecting duct Descending limb Ascending limb Papillary duct Loop of Henle

18. The Ureters They extend from the renal pelvis to the urinary bladder . Renal pelvis Ureter Kidneys and ureters are retroperitoneal organs. Histology 1- Inner mucosa (transitional epithelium + lamina propria). 2-Middle smooth muscle layer. 3-Outer connective tissue layer continuous with the peritoneum.

19. The Urinary Bladder The urinary bladder is in the pelvic cavity and it is covered by a layer of peritoneum (visceral peritoneum). Function: It is a temporary reservoir for the storage of urine. Histology 1- Inner mucosa (transitional epithelium + lamina propria) with folds called rugae. 2- Middle layer: Detrusor muscle (Inner and outer layers of longitudinal smooth muscle, and a circular layer between the two). 3-Outer connective tissue layer continuous with the peritoneum.

20. The Urethra Transitional epithelium

21. The Urethra

22. The Male Urethra The male urethra is about 8 cm long and it is shared by the urinary and reproductive systems. It consists of three regions: prostatic, membranous, and spongy (penile) urethra. Prostate gland Prostatic urethra Urogenital diaphragm Membranous urethra Spongy (penile) urethra Corpus spongiosum