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Urinary System

Urinary System. Urinary System. 2 kidneys Two ureters Urinary bladder Urethra. Functions of the Urinary System. Formation of urine = kidneys - rids body of waste products such as urea, creatine and ammonia Elimination of urine= ureters, bladder, urethra

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Urinary System

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  1. Urinary System

  2. Urinary System • 2 kidneys • Two ureters • Urinary bladder • Urethra

  3. Functions of the Urinary System • Formation of urine = kidneys - rids body of waste products such as urea, creatine and ammonia • Elimination of urine= ureters, bladder, urethra • Regulation of the volume of blood by excretion or conservation of water • Regulation of the electrolyte content of the blood • Regulation of the acid-base balance of the blood

  4. Kidneys • Located in upper abdominal cavity on either side of the vertebral column • Are enclosed and protected by the lower rib cage • Embedded in adipose tissue that act as cushion and fibrous conn. Tissue which helps hold kidneys in place • Hilus: indention on the medial side of each kidney - Renal artery= branch of the abdominal aorta - Renal vein= returns blood to the inferior vena cava

  5. Internal Kidney Structure • The kidneys are composed of three distinct areas: • 1. Renal cortex- outer layer • 2. Renal medulla- inner layer • 3. Renal pelvis- inner cavity

  6. Internal Structure of Kidney • Renal cortex - Outer tissue layer - Made of renal corpuscles and convoluted tubules (parts of nephron) • Renal medulla - Made of loops of Henle and collecting tubules - Consist of wedge-shaped pieces called renal pyramids

  7. Internal Structure of Kidney • Renal pelvis - Cavity formed by the expansion of the ureter within the kidney at the hilus - Funnel shaped extensions of the renal pelvis called calyces - Urine flows from the renal pyramids into the calyces, then to the renal pelvis and out into the ureter

  8. The Nephron • Structural and functional unit of the kidney • Each kidney contains 1 million nephrons • It is here that urine is formed • 2 major portions - Renal corpuscle - Renal tubule

  9. The Nephron Cont. 3 basic functions • Glomerular filtration • Tubular reabsorption • Tubular secretion

  10. Renal Corpuscle • The renal corpuscles are the sites where the process of urine formation begins with a filtrate of blood plasma • The renal corpuscle consist of a glomerulus surrounded by a Bowman’s capsule • The glomerulus is a capillary network, composed of an afferent and efferent arteriole

  11. Renal Corpuscle • Blood enters the glomerulus through the afferent arteriole • Blood leaves the glomerulus through the efferent arteriole • The glomerulus is suspended within the Bowman’s capsule, and are supported by podocytes within the Bowman space

  12. Renal Tubule • Continues from the Bowman’s capsule, and can be found in both the renal cortex and renal medulla • There are four parts of the renal tubule • 1. Proximal tubule, in the cortex, is the beginning of the tubule; reabsorbs minerals and nutrients from the tubular fluid and passes them to blood

  13. Renal Tubule • 2. Loop of Henle, dips into the medulla where it helps establish the hypertonic saline environment within the medulla, which allows for the recovery of water • 3. Distal convoluted tubule returns near the corpuscle; it pumps ions and molecules through its gradient

  14. Renal Tubule • 4. Collecting ducts collect urine from the distal tubules (found in medulla) • All parts are surrounded by peritubular capillaries which arise from the efferent arteriole

  15. Glomerular Filtration • In glomerular filtration, blood pressure forces plasma, dissolved substances, and small proteins out of the glomeruli and into Bowman’s capsule • The fluid is no longer plasma but is called renal filtrate

  16. Tubular Reabsorption • Tubular reabsorption takes place from the renal tubules into the peritubular capillaries. • Peritubular capillaries arise from the efferent arteriole, and receives materials reabsorbed by the renal tubules • Approx. 99% of renal filtrate is absorbed back into the blood in the peritubular capillaries. 1% becomes urine

  17. Four Mechanisms of Reabsorption • 1. Active transport- the cells of the renal tubule use ATP to transport filtrate to the blood • 2. Passive transport- negative ions that are returned to blood are reabsorbed • 3.Osmosis- the reabsorption of water follows the reabsorption of minerals • 4. Pinocytosis- occurs in the proximal tubules, by enveloping small proteins

  18. Tubular Secretion • Changes the composition of urine • Substances are actively secreted from the blood in the peritubular capillaries into the filtrate in the renal tubules • Waste products such as ammonia, some creatine, and medication may be secreted into the filtrate to be eliminated

  19. Other Functions of Kidney • 1. Secretion of renin- when blood pressure decreases cells in the afferent arteriole secrete the enzyme renin; which triggers the renin-angiotensin mechanism and the production of aldosterone • 2. Secretion of erythropoietin- stimulates the red bone marrow to increase the rate of RBC production; which increases oxygen carrying capacity

  20. Other Functions • 3. Activation of vitamin D- vitamin D is converted to calciferol by the kidneys. Calciferol increases the absorption of calcium and phosphate in the small intestine

  21. Dialysis • Separation of large particles from smaller ones through a selectively permeable membrane

  22. Hormones that affect kidneys • Antidiuretic hormone (ADH)- Increases reabsorption of water • Aldosterone- increases reabsorption of Na and excretion of K+ • Atrial natriuretic hormone (ANH)- Decreases reabsorption of Na+

  23. Renal Failure • Inability of the kidney to function properly 3 Causes • Prerenal- problem is before the kidneys, decrease blood flow (hemorrhage) • Intrinsic- problem is in kidneys (bacterial infections) • Postrenal- problem is after kidney, obstruction of urine flow (kidney stones)

  24. Floating Kidney • A floating kidney is one that has moved out of its normal position. If a ureter becomes twisted or kinked, urine cannot flow properly. This could lead to urine backing up into the renal pelvis, and Bowman’s capsule, ultimately causing permanent kidney damage.

  25. Ureters • Ureters extend from the hilus of a kidney to the lower, posterior side of the urinary bladder • The smooth muscle in the walls of the ureter contracts in peristaltic waves to propel urine toward the urinary bladder

  26. Urinary Bladder • The urinary bladder is a muscular sac below the peritoneum and behind the pubic bone • In women, the bladder is inferior to the uterus • In men, the bladder is superior to the prostate gland

  27. Urinary Bladder • The mucosa of the bladder is transitional epithelium, which permits expansion without tearing the lining. • When the bladder is empty, the mucosa appears wrinkled; the folds are called rugae and permit expansion • The trigone is a triangular area on the floor of the bladder, it has no rugae and does not expand • The points of the triangle are the two ureters and the urethra

  28. Urinary Bladder • The detrusor muscle is the smooth muscle layer of the bladder which contracts and decreases its volume • The muscle fibers of the detrusor form the internal urethral sphincter or sphincter of the bladder (involuntary)

  29. Urethra • The urethra carries urine from the bladder to the exterior • The external urethral sphincter is made of skeletal muscle (voluntary) • In women the urethra is 1 to 1.5 inches long • In men the urethra is 7 to 8 inches long, and carries semen as well as urine

  30. Micturition (Urination Reflex) • The urination reflex is a spinal cord reflex in which voluntary control can occur • The stimulus for the reflex is stretching of the detrusor muscle of the bladder • The bladder can hold as much as 800ml of urine, but the reflex is activated around 200 to 400 ml • When the limit is reached impulses travel to the sacral spinal cord

  31. Aging • With age the number of nephrons decrease, often by half • The urinary bladder decreases in size and tone • The chance of infection also increases, because of residue left behind during micturiiton

  32. Kidney Stones • Kidney stones are crystals of the salts that are present in urine, and block the flow of urine in the ureter • Kidney stones are most likely to form in the renal pelvis

  33. Urinary Tract Infection • Infection of a part of the urinary system • Symptoms include burning or painful urination • If chronic, scar tissue forms and impairs function

  34. Bright’s disease • Inflammation of the glomeruli • Caused by bacteria • Endothelial space becomes highly permeable to blood and protein

  35. Renal Failure • Acute is a decrease in glomerular filtration • Chronic is the irreversible decline in glomerular filtration • Diminished- up to 75% • Renal- 75% • End stage- 90% Causes edema, acidosis, anemia

  36. Polycystic kidney disease • Inherited disorder (1:1000) • Tubules become filled with cyst • Apoptosis occurs in tubule cells

  37. Diabetes Insipidus • Excretion of very dilute urine • Patients exhibit extreme thirst • The cause of DI is the defect in the production of ADH

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