Overview of Renal System Function PDF

Overview of function of Renal System Dr Sovan Bagchi, PhD December 10, 2024 www.gmu.ac.ae COLLEGE OF Learning objectives Describe functions of kidney List the steps in urine formation; Define GFR Describe the process of glomer...

Overview of function of Renal System Dr Sovan Bagchi, PhD December 10, 2024 www.gmu.ac.ae COLLEGE OF Learning objectives Describe functions of kidney List the steps in urine formation; Define GFR Describe the process of glomerular filtration; tubular reabsorption and tubular secretion Enlist the factors determining urine output Kidneys The kidney is a reddish brown, bean-shaped organ 12 centimeters long ; it is enclosed in a tough, fibrous capsule. Location of the Kidneys – lie on either side of the vertebral column; retroperitoneal against the deep muscles of the back. Functions of kidney  Excretion of waste products and foreign chemicals.  Regulation of water and electrolyte balances.  Regulation of body fluid osmolality and electrolyte concentrations - Na+, Ca2+, K+ etc.  Regulation of arterial blood pressure via renin –angiotensin system  Regulation of acid balance.  Secretion, metabolism, and excretion of hormones.  Hemopoietin function - Regulation of red blood cell production via the hormone erythropoietin.  Help in the production of vitamin D  Renal Kidney Pyramids structure Renal Renal pelvis cortex Renal capsule Ureter Renal medulla Nephron It is the structural and functional unit of the kidney. Each nephron has two components Vascular component Tubular component Structure of renal corpuscle  It is formed by two parts  1.Glomerulus  2.Bowman’s capsule, which encloses glomerulus  Glomerulus is a tuft of capillaries On end is afferent arteriole and on the other end is efferent arteriole. A glomerulus is a network (as a tuft) of capillaries located at the beginning of a nephron in the kidney. It serves as the first stage in the filtering process of the blood carried out by the nephron in its formation of urine.  Bowman’s capsule  It is a blunt end which encloses capillaries  Tubules extends from bowman’s capsule. Parts of the renal tubule include the proximal convoluted tubule(PCT) loop of Henle (ascending & descending limbs) distal convoluted tubules(DCT) collecting duct, which empties into the minor calyx  Renal Tubule 1. Proximal convoluted tubule (PCT) – Reabsorbs water and solutes from filtrate and secretes substances into it 2. Loop of Henle – a hairpin-shaped loop of the renal tubule Proximal part is similar to the proximal convoluted tubule Proximal part is followed by the thin segment (simple squamous cells) and the thick segment (cuboidal to columnar cells) Renal Tubule 3. Distal convoluted tubule (DCT) – cuboidal cells without microvilli that function more in secretion than reabsorption 4. Collecting ducts - Receive filtrate from the distal convoluted tubules and deliver it to the minor calyces Capillary Beds of the Nephron Every nephron has two capillary beds Glomerulus Peritubular capillaries Each glomerulus is: Fed by an afferent arteriole Drained by an efferent arteriole Urine formation Glomerlar filtration Tubular reabsorption Tubular secretion Renal function Mechanisms of Urine Formation There are three basic renal processes 1. Glomerular filtration-certain substances move from the glomerular capillaries into the renal tubules 2. Tubular reabsorption– some of these substances move back into blood plasma 3.Tubular secretion certain other substances move from the peritubular capillaries into the renal tubules  Juxta glomerular apparatus It is a specializes organ situated near the glomerulus of each nephron(juxta =near) It is formed by three structure as 1)Macula densa –sensitive to the concentration of sodium chloride. 2)Extra glomerular mesengial cells: Regulate glomerular filtration rate by decreasing surface area of glomerular capillaries 3)Juxtaglomerular cells Secrete renin  In the kidney, the macula densa is an area of closely packed specialized cells lining the wall of the cortical thick ascending limb, at the transition to the distal convoluted tubule. The cells of the macula densa are sensitive to the concentration of sodium chloride in the late thick ascending limb. A decrease in sodium chloride concentration initiates a signal from the macula densa that has two effects: (1) it decreases resistance to blood flow in the afferent arterioles via vasodilation, which increases glomerular capillary hydrostatic pressure and helps return glomerulus filtration rate (GFR) toward normal, and (2) it increases renin release from the juxtaglomerular cells of the afferent and efferent arterioles, which are the major storage sites for renin Micturition It is a process by which urinary bladder empties The muscles controlling micturition are controlled by the autonomic and somatic nervous systems. During the storage phase the internal urethral sphincter remains tense and the detrusor muscle relaxed by sympathetic stimulation During micturition, parasympathetic stimulation causes the detrusor muscle to contract and the internal urethral sphincter to relax. The external urethral sphincter (sphincter urethrae) is under somatic control and is consciously relaxed during micturition. Bladder can hold 250 - 400ml Greater volumes stretch bladder walls initiates micturation reflex: Urination coordinated by micturition reflex Initiated by stretch receptors in wall of bladder Urination requires coupling micturition reflex with relaxation of external urethral sphincter  Learning Resources  Text Book: Marieb EN. Human Anatomy and Physiology. 9th Edition, Pearson International Edition; 2014. ISBN-13: 978-1-2920-2649-7.  Power-point presentation in the moodle December 10, 2024 www.gmu.ac.ae COLLEGE OF