Ibn Sina University College Of Medicine Biology Lecture 13: The Urinary System PDF

IBN SINA UNIVERSITY COLLEGE OF MEDICINE BIOLOGY  Lecture 13 The Urinary System  There are 2 important homeostatic processes maintain a constant internal environment in the body, these are: 1. Excretion. 2. Osmoregulation. 1. Excretion Removal of metabolic waste products f...

IBN SINA UNIVERSITY COLLEGE OF MEDICINE BIOLOGY  Lecture 13 The Urinary System  There are 2 important homeostatic processes maintain a constant internal environment in the body, these are: 1. Excretion. 2. Osmoregulation. 1. Excretion Removal of metabolic waste products from the body. 2. Osmoregulation Maintenance of constant osmotic conditions in the body. The major excretory products are: 1. Nitrogenous compounds: Excreted through the kidneys, and with sweat through the skin. 2. Carbon dioxide and water vapor: Excreted through the lungs. 3. Bile pigments: From breakdown of hemoglobin of old RBCs. Excreted with the feces through the digestive system. Functions of urinary system: 1. Removal of metabolic waste products and other harmful substances from the body. 2. Regulates the amount of water, salts, and other substances in the body. 3. Control of blood pH. Structure of urinary system  Urine is formed in the kidneys. Drained from the kidneys by a pair of ureters to the urinary bladder Then to out of the body through urethra by the process of urination. Blood vessels of urinary system Renal arteries supply the Kidneys with blood received from the dorsal aorta. Renal veins return blood to the posterior vena cava.  Structure of kidney The kidney shows three distinct regions: 1. Outer cortex. 2. Inner medulla. 3. The pelvis.  The Renal Cortex is covered by fibrous connective tissue (capsule). Contains blood capillaries. The Renal Medulla contains Fine tubules and blood vessels which together form the renal pyramids.  All pyramids drain the urine to the pelvis, and then to the ureter.  Each kidney contains about one million of nephrons. Nephrons are the blood - filtering units of the kidney. Nephrons are the basic units of structure and function of the kidney.  The nephrons are located within the cortex and medulla of each kidney. Surrounded by a network of blood vessels. Each nephron is composed of: 1. Glomerulus. 2. Bowman’s capsule. 3. Proximal convoluted tubule. 4. Loop of Henle. 5. Distal convoluted tubule. 6. Collecting duct. 1. The glomerulus : A mass of thin walled blood capillaries. 2. Bowman’s capsule (glomerular capsule): A cup - shaped structure surrounding the glomerulus. ❖ The glomerulus + Bowman’s capsule = The renal corpuscle (malpighian corpuscle). ❖ Ultra-filteration of the blood takes place in the renal corpuscle. ❖ Inside the kidney, the renal artery branches into small arterioles then into fine glomerulus capillaries. ❖ This increases the blood pressure. ❖ All blood contents will come out of the capillaries to the Bowman’s capsule. ❖ Larger molecules e.g. proteins, Blood Cells …etc. remain in the capillaries.  The Filtered fluid contains glucose, amino acids, some hormones, nitrogenous wastes (urea, uric acid,….) and water. Renal tubules reabsorb useful materials needed by the body and return them to the bloodstream. 3. The proximal convoluted tubule: Reabsorb 90% of the water, glucose, amino acids and many salts (by osmosis , diffusion, and active transport ). Return them to the bloodstream by the surrounding blood capillaries. 4. Loop of Henle conserves water. Cells of the descending limb are highly permeable to water. Cells of the ascending limb are impermeable to water but permeable to ions Na+, K+ , Cl-…. etc. 5. The distal convoluted tubule Controls the precise amount of water and salts reabsorbed. Also controls blood pH. 6. The collecting duct Collects urine pyramids pelvis ureter urinary bladder.  The kidneys filtered 180 liters of blood/day. Produce 1 to 1.5 L of urine/day. Part of the nephron Function renal corpuscle Blood filtration. Proximal convoluted Reabsorption of useful tubule substances. Loop of Henle conserves water. controls the precise amount Distal convoluted of water and salts. also tubule controls blood pH. Collecting Duct carries fluid to the pelvis. Thank You