Biology Of Human Aging

1. Biology Of Human Aging Chapter 12 Urinary System

2. Outline • Review of the Structure and Function • Kidneys / Ureters / Urinary Bladder / Urethra • Age-Related Changes • Kidneys / Bladder and Urethra • Age-Related Dysfunctions • Urinary iIncontinence • Nocturia • Dysfunctions Caused by the prostate gland • Pyelonephritis • Renal Calculi

3. Kidney Functions • Filter 200 liters of blood daily, allowing toxins, metabolic wastes, and excess ions to leave the body in urine • Regulate volume and chemical makeup of the blood • Maintain the proper balance between water and salts, and acids and bases • Production of rennin to help regulate blood pressure and erythropoietin to stimulate RBC production • Activation of vitamin D

4. Other Urinary System Organs • Urinary bladder – provides a temporary storage reservoir for urine • Paired ureters – transport urine from the kidneys to the bladder • Urethra – transports urine from the bladder out of the body

5. Urinary System Organs Figure 25.1a

6. Layers of Tissue Supporting the Kidney • Renal capsule – fibrous capsule that prevents kidney infection

7. Internal Anatomy • A frontal section shows three distinct regions • Cortex– the light colored, granular superficial region • Medulla – exhibits cone-shaped medullary (renal) pyramids • Pyramids are made up of parallel bundles of urine-collecting tubules • Renal pelvis – flat, funnel-shaped tube lateral to the hilus within the renal sinus

8. Internal Anatomy • Major calyces – large branches of the renal pelvis • Collect urine draining from papillae • Empty urine into the pelvis • Urine flows through the pelvis and ureters to the bladder

9. Internal Anatomy Figure 25.3b

10. The Nephron • Nephrons are the structural and functional units that form urine, consisting of: • Glomerulus – a tuft of capillaries associated with a renal tubule • Glomerular (Bowman’s) capsule – blind, cup-shaped end of a renal tubule that completely surrounds the glomerulus

11. The Nephron • Renal corpuscle – the glomerulus and its Bowman’s capsule • Podocytes (cleft cells)

12. Renal Tubule • Proximal convoluted tubule (PCT) –with numerous microvilli and mitochondria • Reabsorbs water and solutes from filtrate and secretes substances into it • Loop of Henle – a hairpin-shaped loop of the renal tubule • Distal convoluted tubule (DCT) – cuboidal cells without microvilli that function more in secretion than reabsorption

13. Renal Tubule Figure 25.4b

14. Capillary Beds Figure 25.5a

15. 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

16. Capillary Beds of the Nephron • Blood pressure in the glomerulus is high because: • Arterioles are high-resistance vessels • Afferent arterioles have larger diameters than efferent arterioles

17. Filtration Membrane Figure 25.7a

18. Filtration Membrane Figure 25.7c

19. Mechanisms of Urine Formation • Urine formation and adjustment of blood composition involves three major processes • Glomerular filtration • Tubular reabsorption • Secretion Figure 25.8

20. Ureters • Slender tubes that convey urine from the kidneys to the bladder • Ureters enter the base of the bladder through the posterior wall • This closes their distal ends as bladder pressure increases and prevents backflow of urine into the ureters • Ureters actively propel urine to the bladder via response to smooth muscle stretch

21. Urinary Bladder • Smooth, collapsible, muscular sac that temporarily stores urine • Outlined by the openings for the ureters and the urethra • Clinically important because infections tend to persist in this region

22. Urinary Bladder Figure 25.18a, b

23. Urethra • Muscular tube that: • Drains urine from the bladder • Conveys it out of the body

24. Urethra • Sphincters keep the urethra closed when urine is not being passed • Internal urethral sphincter – involuntary sphincter at the bladder-urethra junction • External urethral sphincter – voluntary sphincter surrounding the urethra as it passes through the urogenital diaphragm

25. Age-Related Changes • Kidney • Thickening of connective tissue capsule • Decrease in thickness of cortical region • General atrophy of cells and gradual decrease in kidney weight • Decrease in kidney functioning • Increase in the incidents of abnormal glomeruli and replacement of degenerated glomeruli by connective tissue (non-permeable) • Proteinuria (presence of protein in urine) • Increased abnormalities and degeneration of renal tubules • Blood vessels: thickening of walls, loss of muscular tissue, and atherosclerotic deposits • Decline in the ability to handle large changes in acid base levels

26. Age-Related Changes • 2. Bladder and Urethra • Weakening and loss of elasticity of the muscles in the walls • Inability to expand or contract  lower bladder capacity in elderly • Retention of residual urine (100 ml) after urination in elderly • Delay in awareness of the need to urinate • Urination in elderly may be urgent, & due to weakness of external urethral sphincter elderly may be unable to reach the lavatory in time • Urination during night more common in elderly • Weakness of the muscles of the pelvic cavity floor  ineffectiveness of external urethral sphincter  urine leakage (usually seen in sudden rise in pressure of bladder) cough or sneeze This is calledStress Incontinence (more common in older women)

27. Age-Related Dysfunctions • Urinary Incontinence • Involuntary passing of urine through the urethra • Incidents twice as high in women as in men • Due to weakness of internal & external urethral sphincters & uninhibited contractions of smooth muscles  hyperactive bladder • Significant problem in older persons  marketing of adult diaper-like undergarments is a profitable enterprise • Also reduction of bladder volume & delayed sensation to urinate due to muscle atrophy • Post-menopausal women: estrogen deficiency  weak muscles • Involuntary urine passage is due to: • Mechanical conditions that elevate bladder pressure (cough or sneeze) • Incomplete emptying of the bladder

28. 2. Nocturia • Excessive urination at night • Not a serious condition by itself, yet disturbs sleep • Taking drugs: bodily reactions to drugs (relaxation of sphincters or stimulation of muscles) • Not taking drugs: due to age related losses in bladder distensibility & inability of kidney to concentrate here

29. 3. Dysfunctions caused by the Prostate Gland • Reproductive organ, yet interferes with function of urinary system • Overall atrophy of prostate with aging, yet a lot of men experience growth of prostate • Benign hyperplasia of prostate: compresses the urethra, difficulty in urination, bladder never completely emptied • Increases pressure in glomerular capsules  kidney malfunction • Symptoms: Reduced force behind urine stream, frequent urination, inability to empty bladder • Treatment: surgery, transurethral resection

30. 3. Dysfunctions caused by the Prostate Gland • Carcinoma: most frequent tumor of old men • Early stages: little or no urethral obstruction, unaware of tumor • Later stage: restrict urine flow, tumor too far advanced to be treated • Regular examination, Digital Rectal Exam (DRE), PSA test • Drugs: lengthy remissions, surgery

31. 4. Pyelonephritis • Inflammation of the kidney • Not restricted to older persons • Acute pyelonephritis is a bacterial infection that travels to the kidney in the blood or lymphs • Causes swelling of kidney due to fluid build up • In severe cases, abscesses develop  inflammation & pus • Chronic problem and causes extensive scar tissue in kidney  kidney failure • Responds well to antibiotic treatment • Serious condition (uremia)

32. 5. Renal Calculi • Kidney stones, not restricted to elderly • Most stones do not cause significant symptoms • Passage of stones from kidney, ureter, & bladder  strong muscle contractions  episodes of severe pain • If stone lodged in ureter obstructs urine flow  kidney damage, ulceration, vulnerable to infection • Cause: Ca2+, uric acid, cystine, magnesium, ammonium phosphate • Kidney stone formation related to: Various kidney infections, high salt concentration in urine, Vit. A deficiency, tumor of parathyroid gland