Renal System PDF

Renal Physiology  Kidney Function 1. Regulation of water and inorganic ions balance 2. Excretion of metabolic waste products 3. Removing of foreign chemicals by producing & excreting urine to maintain the internal homeostasis of the body  Kidney Function 4. Sec...

Renal Physiology  Kidney Function 1. Regulation of water and inorganic ions balance 2. Excretion of metabolic waste products 3. Removing of foreign chemicals by producing & excreting urine to maintain the internal homeostasis of the body  Kidney Function 4. Secretion of hormones a. Erythropoietin which controls erythrocyte production b. Renin, ( is produced by juxtaglomerular cell) which controls formation of angiotensin c. 1,25-dihydroxyvitamin D3 , which influences calcium balance Anatomical Characteristics of the Kidney The kidney: renal cortex renal medulla renal pelvis  Anatomical Characteristics of the Kidney 1. Nephrons: functional unit of kidneys (1). Consist of nephron Nephron is the basic smallest functional unit of kidney. Nephron consists of renal corpuscle and renal tubule. Each kidney is composed of about 1 million microscopic functional unit.  Consist of Nephron glomerulus renal corpuscle Bowman’s capsule Nephron proximal convoluted tubule proximal tubule thick descending limb renal tubule thin descending limb loop of Henley thin ascending limb thick ascending limb distal tubule distal convoluted tubule  Anatomical Characteristics of the Kidney Functional unit -nephron: Corpuscle: Bowman’s capsule Glomerulus capillaries Tubule: PCT Loop of Henley DCT Collecting duct  Two Types of Nephron Cortical nephrons ~85% of all nephrons Located in the cortex Juxtamedullary nephrons Closer to renal medulla Loops of Henle extend deep into renal pyramids Tab. 8-1. Differences between a cortical and a Juxtamedullary nephron Cortical nephron Juxtamedullary nephron Location Outer part of the cortex Inner part of the cortex next to the medulla Glomerulus Small Big Loop of Henle Short, next to outer cortex Longer, into inner part of cortex efferent glomerular arteriole To form Peritubular capillary To form Vasa recta Sympathetic nerve innervation Rich Poor Concentration of renin High Almost no Ratio 90% 10% Function Reabsorption and secretion Concentrate and dilute urine Cortical and Juxtamedullary Nephrons Juxtaglomerular apparatus (JGA) macula densa --- in initial portion of DCT Function : sense change of volume and NaCl concentration of tubular fluid , and transfer information to JGC ⚫ mesangial cell ⚫ juxtaglomerular cell (JGC) --- in walls of the afferent arterioles) Function: secrete renin  Juxaglomerular apparatus JA locate in cortical nephron, consist of juxtaglomerular cell、 mesangial cell and macula densa.  Tubulo-glomerular Feedback Macula densa can detects Na+, K+ and Cl- of tubular fluid, and then sent some information to glomerule, regulation releasing of renin and glomerular filtration rate. This process is called Tubulo- glomerullar feedback.  Renal circulation 1.Characteristics of renal blood circulation Huge volumes blood： 1200ml/min，1/5 – 1/4 of the cardiac output. Distribution： Cortex 94%, outer medulla 5 - 6%, inner medulla 2500ml/day long time Abnormal urine volume: Losing water and electrolytes.  Micturition Functions of ureters and bladder: Urine flow through ureters to bladder is propelled by contractions of ureter-wall smooth muscle. Urine is stored in bladder and intermittently ejected during urination, or micturition.  Micturition Micturition is process of emptying the urinary bladder Two steps are involved: (1) bladder is filled progressively until its pressure rises above a threshold level (400~500ml); (2) a nervous reflex called micturition reflex occurs that empties bladder.  Micturition (Voiding or Urination) Bladder can hold 250 - 400ml Greater volumes stretch bladder walls initiates micturation reflex: Spinal reflex Parasympathetic stimulation causes bladder to contract Internal sphincter opens External sphincter relaxes due to inhibition Urination: Micturation reflex Figure 19-18: The micturition reflex