12. urinary system


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12. urinary system

  1. 1. URINARY SYSTEM S.S.MOORTHY SEMENCHALAM M.Sc. Comm Health (Occ Health) UKM B.HSc. Nursing (Aust) Dip Med Sc. (Moh)
  2. 2. Learning objectivesAt the end of the lesson, students will be able to:1.State the main components of urinary system2.Lists the functions of kidney3.State the path of blood flow through the kidney4.State the structure of nephrones5.State and describe 3 main processes in urine formation6.State the compositions of urine7.State the structure and specific functions of ureter, urinary bladder and urethra8.Discuss the process of micturition
  3. 3. Urinary system consists of: • 2 kidneys ; urine formation takes place • 2 ureters; carry urine from kidney to urinary bladder • 1 urinary bladder; storage of urine • 1 urethra; carries urine from bladder out from body
  4. 4. Function of the Kidney1. Eliminates waste products – urea, creatinine etc2. Regulates blood pressure by secreting renin (juxtaglomerular cells)3. Maintains water & electrolyte balance4. Synthesis of prostaglandins & erythropoitein
  5. 5. Structure of kidney• Retroperitoneal• Superior lumbar region• Right kidney slightly lower than left• Bean-shaped, indentation: hilus• Adrenal gland on top
  6. 6. Three layers of supportive tissue• Renal capsule: fibrous connective tissue that enclosed kidney• Renal fat pad: adipose tissue around renal capsule; protects kidney from mechanical shock• Renal fascia: connective tissue that anchor kidney to abdominal wall
  7. 7. Longitudinal section of kidney  cortex- outer, made of bowman’s capsule enclosing glomerulus  medulla- inner, tubules responsible for urine formation
  8. 8. • Within medulla, triangular shaped structures; renal pyramids• Base: open into cortex• Apex: point to apexbase centre; renal papilla
  9. 9. • Renal cortex & renal pyramids- form the functional portion of kidney• Each renal cortex & medulla; is made of 1 million nephrons• Each nephron is the basic unit of urine formation. When nephrons are damaged they are not replaced
  10. 10. • Urine formed by nephron, drains into large ducts- papillary ducts• Papillary ducts drain their contents into minor calyces• Papillary ducts: 8-18 per kidney
  11. 11. • Contents of minor calyces drain into major calyces• Major calyces: 2-3 per kidney• From major calyces, urine drains into renal pelvis• From renal pelvis it drains into the ureters
  12. 12. Route taken by the urine in the kidney after its formation: Nephrons Papillary ducts (renal pyramid) Minor calyx Major calyx Renal pelvis Ureters
  13. 13. Renal medulla ureter urinary bladder urethra ureterUrinary bladder urethra
  14. 14. Nephron: The basic functional unit of kidney • Each kidney made of millions of nephron • Tubule; closed at one end, other end opening to collecting tubule
  15. 15. Nephron Closed-end - indented to form cup-shaped glomerular capsule(Bowman’s capsule) - enclosed arterial capillaries network (glomerulus) Remainder: i. Proximal convoluted tubule (PCT) ii. Loop of Henle ii. Distal convoluted tubule (DCT)
  16. 16. Nephrons: functional units of kidney
  17. 17. Renal artery (at hilum):• from abdominal aorta, enters renal sinus• Branches to form afferent arterioles• Supply oxygenated blood to glomerular capillaries of renal corpuscles
  18. 18. • Efferent arterioles arise from glomerular capillaries & carry blood away from glomeruli• These gives rise to plexus of capillaries around PCT & DCT• a.k.a peritubular capillary system• Join to form renal vein• Renal vein: drains deoxygenated blood into inferior vena cava
  19. 19. Afferent arteriole - brings blood to the glomerulusEfferent arteriole - brings blood away from the glomerulus
  20. 20. Bowman’s capsule:• externally layered with squamous epithelium• Internal viscera: specialized epithelial cells (podocytes)• Basement membranes: separate endothelial calls of glomerular capillaries & podocytes
  21. 21. • Capillary endothelium *• Basement membrane• Podocytes* Made of filtrate membrane; major role in the first step of urine formation
  22. 22. The renal corpuscle opens into:• Proximal convulated tubule (PCT) - lined with microvilli in lumen - cuboidal epithelium - absorption & secretion - opens into nephron loop
  23. 23. • Distal convulated tubule (DCT), further end of the nephron - cuboidal epithelium with fewer microvilli - surrounded by smooth muscles of the space to form juxta glomerular apparatusPCT, renal corpuscle & DCT: placed in outer kidney cortex
  24. 24. i. nephron loop connect PCT & DCTii. collecting tubule receives contents from DCTiii. squamous epithelium protect the tubules against abrasioniv. cuboidal epithelium: reabsorption of water & ions in the process of urine formationv. nephron loop, collecting ducts & DCT placed in medullavi. The DCT opens into collecting tubule carrying urine into calyces •DCT < microvilli than PCT
  25. 25. Urine production:In nephron• 3 processes  Glomerular Filtration  Tubular Reabsorption  Tubular Secretion
  26. 26. Filtration• Occurs in Bowman’s capsule by filtrate or hydrostatic pressure from glomerular capillaries• Due to smaller diameter of efferent arterioles than afferent arterioles
  27. 27. Filtration Cont.• Pressure exerted by plasma & osmotic pressure in glomerulus (filteration pressure) -forces substances out of glomerulus• The portion of the plasma entering the nephron is called -Filtrate• Generally, small molecule: - diameter <40,000 daltons/ 7nM - e.g. water, sugar, ions, aminoacids, ammonia, urea, creatine able to pass through• Large molecules: - exit into glomerulus - transported through blood into efferent arterioles
  28. 28. Tubular Reabsorption: • The filtrate leaves Bowman’s capsule & flow through proximal tubule, nephron loop & DCT • Substances needed in filtrate are reabsorbed back into blood - to maintain fluid & electrolyte, pH • Active transport
  29. 29. • These include water, important amino acids, nutrients, hormones etc. a. Water is reabsorbed by osmosis in PCT b. Amino acids, ions(Na+) are reabsorbed by active transport in the PCT c. limit to glucose reabsorbtion: up to 100 mg/100ml, then all is reabsorbed (no glucose in urine)
  30. 30. d. above 150 mg/100ml glucose, then glucose present in urinee. active ion reabsoption: sodium, potassium, calcium, magnesium,bicarbonate, phosphate, and sulfate ions actively resorbed (selective reabsorption)f. The small volume of filterate forming a part ofurine are urea, creatine, toxic substances and K+.
  31. 31. Secretion• Substances that is not required & foreign material (e.g. drugs); secreted into tubules to be excreted out from body (in urine)• Tubular secretion: secrete H+ to maintain homeostasis of blood pH
  32. 32. • Ammonia is secreted by the epithelial cells of nephron and secreted into lumen of nephron by passive transport.• Substances that are toxic to body include drugs, hydrogen ions, K+ ions are secreted into PCT, DCT by active transport.• Though the filtrate that enters the proximal convoluted tubule is 180 lts,• only 1% is ultimately removed as urine and• 99% is reabsorbed along the different regions of the nephron
  33. 33. Urine composition• Colour: clear - Light yellow (presence of urobilin)• Normal volume 1 to 1.5L/day• pH ≈ 6 (4.5-8) but mostly acidic• Normal specific gravity- 1.003 to 1.040
  34. 34. Major nitrogen-containing wastesa. Urea: most abundant organic waste product (21g/day), d/t breakdown of amino acidsb. Uric acid: results from breakdown of nucleic acids (0.5g/day)c. Creatinine: generated in muscle tissue from breakdown of creatine phosphate (1.8g/day: amount depend on muscle mass)d. Ammonia salt: small amount filtered into Bowman’s capsule
  35. 35. Water balance & urine output• Regulation of urine formation – regulates homeostasis of fluids in the body• Hormones: i. Antidiuretic hormone (ADH) ii. Aldosterone iii. Antinatriuretic hormone (ANH)
  36. 36. a. When water concentration is low………. Aldosterone releasedStimulates gene expression of those proteins that involved in Na+ active transport Na+ ion concentration in blood (K+ eliminate) Water reabsorbed & conserved Urine formation i. Maintain water levels in blood ii. Maintain blood pressure
  37. 37. b. When water concentration is high……… Release of aldosterone is inhibitedStopping gene expression of those proteins that involved in Na+ active transport Na+ ion concentration in blood (reduce ion Na+ uptake) Water excretion increases Urine formation i. Maintain water levels in blood ii. Maintain blood pressure
  38. 38. Ureters• Tubes; convey urine from kidney to urinary bladder• Continuous with renal pelvis; passes obliquely through the posterior wall of bladder• Urine accumulates – pressure in bladder – ureters compressed – opening occluded - to prevent urine reflux back
  39. 39. Ureters: structure & function• 3 layers of tissue: i. fibrous tissue – outer covering ii. muscular layer – middle iii. Mucosa – inner, transitional epithelium• Function: propel urine from kidney into bladder by peristaltic contraction of the smooth muscle
  40. 40. Urinary bladder• Reservoir for urine• Situated in pelvic cavity – size & position vary depends on the amount of urine contain• Structure: - pear-shaped – oval (filled with urine) - 3 surface: anterior, superior & posterior (base) - opens into urethra at the lowest point (neck) - have folds/ rugae - 3 orifices; form trigone (2: posterior wall – opening of ureters & 1: lower – origin of urethra)
  41. 41. Urinary bladder: structure & function• 3 layers of bladder wall i. outer: loose connective tissue (blood, lymph vessels & nerves) ii. middle: smooth muscle & elastic tissue; dextrusor muscle iii. inner: mucosa, transitional epithelium
  42. 42. Urethra• Urethra opens to out side by external sphincter made of skeletal muscles.• ♂ - opens into penis• ♀ - opens into vestibule in vagina.• By parasympathetic stimulation , muscles of bladder expel urine.
  43. 43. Male urethra• 18-20cm long• 2 curvatures – s- shaped• Extend from internal urethral orifice at the neck of bladder to external urethral orrifice at tip of penis
  44. 44. Female Urethra • Narrow membranous about 4cm long • Extend from internal to external urethral orifice directly in front of the vaginal opening • Place behind the symphysis pubis in the anterior wall of vagina
  45. 45. MICTURITION• The reflex center for urination is present in the spinal cord• Reflex center respond to stretch receptors of urinary bladder• Initiates urge to urinate
  46. 46. • Process of urination requires i. relaxation of external urethral sphincter, ii. contraction detrusor muscles iii. the muscles of abdominal wall and pelvis• Detrusor is a smooth muscle under parasympathic control• Where as• Muscles of abdomen and pelvis and external urethral sphincter are skeletal muscles under voluntary control
  47. 47. Muscle involved in micturition
  48. 48. Thank you….Questions please!!