Excretory system [compatibility mode]


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Excretory system [compatibility mode]

  1. 1. 7/6/2012 Urinary System By Shahzad Bashir RN, BScN NMC (ION) 7/6/2012 1 7/6/2012 2 Objectives Urinary systemBy the end of this presentation, you will be able to: The urinary system is one of the excretory Define urinary system and its organs. system of the body. Discuss kidney in detail. It plays a vital role in maintaining homeostasis Role of kidneys in maintaining water and of water and electrolyte. electrolytes balance. Kidneys produce urine that contains metabolic Structure and functions of ureters, urinary bladder waste products. and urethra. Process of micturation. 7/6/2012 3 7/6/2012 4 Organs of urinary system Functions of Renal system Paired kidneys Formation and secretion of urine. A ureter for each kidney Production and secretion of erythropoietin. Production and secretion of renin. Urinary bladder Urethra 7/6/2012 5 7/6/2012 6 1
  2. 2. 7/6/2012 Shape Kidneys Lateral surface - convex; medial – concave. . Retroperitoneal, level of T12 to L3 About 150 g each coverings They are bean shaped organs,11cm long, 6cm wide and 3cm thick Renal fascia: binds to abdominal wall Adrenal glands lie superior to each kidney Adipose capsule: cushions kidney Renal capsule: encloses kidney7/6/2012 7 7/6/2012 8• Kidneys make up 1 % of body mass, but 2. Regulation: receive about 25% of cardiac output. Blood volume and composition• Kidney has two major functions: Electrolytes 1. Filtration of blood Blood pH • Removes metabolic wastes from the body, esp. those containing nitrogen Blood pressure7/6/2012 9 7/6/2012 10 Gross structure of kidneys Kidney has two regions Cortex: outer Columns of cortex divide medulla into “pyramids” Medulla: inner Darker, cone-shaped medullary or renal pyramids Parallel bundles of urine-collecting tubules Expanded, funnel shaped, superior part of ureter Branches to form two or three major calices Each of these divides again, minor calices: collect urine from papillae of pyramids7/6/2012 11 7/6/2012 12 2
  3. 3. 7/6/2012 Microscopic structure of kidneys The kidney is composed of about 1 million of functional units, the nephrons and smaller number of collecting tubules.The collecting tubules transport urine through the pyramids to the renal pelvis. 7/6/2012 13 7/6/2012 14 Each kidney receives blood Nephron from a renal artery, and produces urine.Kidney is made up of thousands of repeating units Urine drains from each kidney(nephrona), each with the structure of a bent tube. Blood pressure forces the fluid in blood past a filter, through a ureter which carries glomerulus, at the top of each nephron. urine to urinary bladder. Water and small molecules pass through filter and into the nephron tube. Within the kidney, mouth of Sugars and ions are removed by active transport ureter flares to form renal pelvis. Divided into renal cortex and 7/6/2012 15 7/6/2012 renal medulla. 16 Fluid then moves down the Nephron structure and function medulla and back into the cortex Blood is carried by an afferent in a loop of Henle. arteriole to the glomerulus. After leaving the loop, the fluid is Blood is filtered as it is forced delivered to a distal convoluted through porous capillary walls. tubule in the cortex that drains to Glomerular filtrate enters a collecting duct. Bowman’s capsule. merges with other collecting Moves to the proximal ducts to empty its contents into convoluted tubule. the renal pelvis 7/6/2012 17 7/6/2012 18 3
  4. 4. 7/6/20127/6/2012 19 7/6/2012 20 Reabsorption and secretion Excretion Most of the water and dissolved solutes that enter the glomerular filtrate must be returned to the blood. Some mechanism is needed to create an osmotic Reabsorption of glucose and amino acids, is driven by gradient between the glomerular filtrate and the active transport carriers. blood, allowing reabsorption Secretion of waste products involves transport across capillary membranes and kidney tubules. Proximal convoluted tubule Loop of Henle Approximately two-thirds of NaCl and water Descending limb is permeable to water, thus water filtered in Bowman’s capsule is immediately leaves via osmosis. reabsorbed across the walls of the proximal Water loss in the descending limb multiples convoluted tube. concentration achieved at each loop. Ascending limb actively extrudes N+ and Cl follows. NaCl pumped out of ascending limb is trapped within surrounding interstitial fluid. countercurrent multiplier system 4
  5. 5. 7/6/2012 Distal tubule and collecting duct Reabsorption of Salt and Water Permeability of the collecting duct to water is adjusted by antidiuretic hormone (ADH - vasopressin). Kidneys also regulate the balance of electrolytes in the blood by reabsorption and secretion. Ureters Urinary Bladder Located in pelvic cavity, posterior to pubic from renal pelvis passes dorsal to bladder and enters it symphysis from below, about 25 cm long 3 layers Outer fibrous tissue The outer layer of loose connective tissue Middle muscular The middle is smooth muscle Inner mucusa Inner ,the mucusa. Female Urethra rugae: relaxed bladder wrinkled, 3 to 4 cm long highly distensible External urethral orifice between vaginal orifice and clitoris capacity: moderately full - 500 Internal urethral sphincter ml, max. - 800 ml detrusor muscle thickened, smooth muscle, involuntary control • External urethral sphincter: –skeletal muscle, voluntary control7/6/2012 29 5
  6. 6. 7/6/2012 Male Bladder and Urethra Voiding Urine - Micturition Micturition reflex Internal urethral sphincter 1) 400 ml urine in bladder, stretch receptors send External urethral sphincter signal to spinal cord (S2, S3) 2) parasympathetic reflex arc from spinal cord,• 3 regions stimulates contraction of detrusor muscle –prostatic urethra 3) relaxation of internal urethral sphincter •during orgasm receives semen 4) this reflex predominates in infants –membranous urethra •passes through pelvic cavity –penile urethra References•Tortora, J. G., Derrichson, B. (2006).Principles of Anatomy and Physiology. (11th ed). USA:New York. John Willey 7 sons , Inc.•Ross and Wilson, Anatomy and Physiology (ninthedition) in health and illness. 6