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(Chapter 23)

The Urinary System. (Chapter 23). Lecture # 10: Functions of the Urinary System and Anatomy of the Kidneys. Objectives. 1- To name and locate the organs of the urinary system. 2- To list several functions of the kidneys in addition to urine formation. .

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(Chapter 23)

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  1. The Urinary System (Chapter 23) Lecture # 10: Functions of the Urinary System and Anatomy of the Kidneys Objectives 1- To name and locate the organs of the urinary system. 2- To list several functions of the kidneys in addition to urine formation. 3- To name the major nitrogenous waste and identify their sources. 4- To describe the location and identify the major external and internal features of the kidneys. 5- To trace the flow of blood through the kidneys, and the flow of fluids through the renal tubules.

  2. The Urinary System Kidneys Ureters Urinary bladder Urethra (a) Anterior view (b) Posterior view

  3. Functions of the Kidney 1- Filters blood plasma, separates waste from useful chemicals, returns useful substances to blood, and eliminates wastes. 2- Regulates blood volume and pressure by eliminating or conserving water. 3- Regulates the osmolarity of the body fluids by controlling the relative amounts of water and solutes eliminated. 4- Secretes the enzyme, renin, which activates hormonal mechanisms that control blood pressure and electrolyte balance. 5- Secretes erythropoietin, a hormone that stimulates the production of red blood cells. 6- Collaborate with the lungs to regulate the PCO2 and acid-base balan-ce of body fluids. 7- Carries out the final step in synthesizing hormone, calcitriol, which contributes to calcium homeostasis. 8- Carries out the gluconeogenesis from amino acids in extreme star-vation.

  4. Nitrogenous Wastes Waste: It is any substance that is useless to the body or present in excess of the body’s needs. Metabolic waste: It is a waste substance produced by the body. Among the most toxic metabolic wastes are the nitrogenous wastes: 1- Proteins NH2removed Liver 3- Creatine Phosphate 2- Nucleic Acids

  5. Blood Urea Nitrogen (BUN) It is an expression of the level of nitrogenous waste in the blood (normal value: 10-20 mg/dL) An elevated BUN is called Azotemia and may indicate renal insufficiency. It is a syndrome produced by extremely high values of BUN due to renal failure. Uremia: • It consists of diarrhea, vomiting, dyspnea, and cardiac arrhythmia stemming from the toxicity of nitrogenous waste. Excretion Excretion is the process of separating wastes from the body fluids and eliminating them. Four body systems carry out excretion: • 1- The respiratory system (CO2, small amounts of other gases, and water) • (water, inorganic salts, lactic acid, urea in sweat). • 2- The integumentary system • 3- The digestive system • (water, salts, CO2, lipids, bile pigments, cholesterol, other metabolic waste, and food residue). • 4- The urinary system • (many metabolic wastes, toxins, drugs, hormones, salts, H+ and water).

  6. Anatomy of Kidney • 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. Stomach Small intestine Pancreas Hilum Visceral Peritoneum Parietal Peritoneum Lumbar muscles Renal fascia Perirenalfat capsule Fibrous capsule

  7. Fibrous capsule Parenchyma: Renal cortex Renal column Renal pyramid Renal medulla Renal artery Renal vein Renal lobe Renal pelvis Major calyces Renal papilla Minor calyces Ureter Parenchyma Renal sinus Hilum

  8. Renal Circulation Glomerular capillaries Afferent arteriole Efferent arteriole Segmental artery Peritubular capillaries Renal artery Venule Interlobular vein Renal vein Arcuate vein Arcuate artery Interlobular artery Interlobar artery and vein Arcuate artery and vein Interlobular (cortical radiate) artery and vein

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

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

  11. 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 Proximal convoluted tubule (PCT) Distal convoluted tubule (DCT) - Proximal convoluted tubule (PCT) - Nephron loop (loop of Henle) - Distal convoluted tubule (DCT) - Collecting duct Renal corpuscle The collecting duct receives fluids from the distal convoluted tubules of several nephrons as it passes back into the medulla. Nephron loop (loop of Henle) Collecting duct (CD) • Numerous collecting ducts converge toward the tip of the medullary pyramid to form a papillary duct. About 30 papillary ducts end in the tip of each papilla.

  12. The Renal Corpuscle Glomerular capsule: Parietal layer Capsular space A resin cast of the glomerulus Afferent arteriole Podocytes of visceral layer Podocyte Blood flow Proximal convoluted tubule Efferent arteriole Glomerular capillaries (podocytes and capillary wall removed) Blood flow Capillaries of the glomerulus wrapped in podocyte

  13. It arises from glomerular capsule • longest and most coiled region. • Simple cuboidal epithelium with microvilli for majority of absorption. Proximal convoluted tubule (PCT) Distal convoluted tubule (DCT) • It is shorter and less coiled that PCT. • Cuboidal epithelium without microvilli. Nephron loop: Descending limb Ascending limb Thick segment It is heavily engaged in the active transport of salts and have many mitochondria. Collecting duct (CD) Minor calyx It receives fluid from the DCTs of several nephrons as it passes back into the medulla. • 30 papillary ducts end in the tip of each papilla. Thin segment • Simple squamous epithelium with cells very permeable to water. Papillary duct It is formed by merger of several collecting ducts.

  14. Flow of fluid from the point where the glomerular filtrate is formed to the point where urine leaves the body. Glomerular capsule Proximal convoluted tubule Nephron loop Distal convoluted tubule Collecting duct Papillary duct Minor calyx Major calyx Renal pelvis ureter Urinary bladder Urethra

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