1 / 35

Urinary

Urinary . Part Two. Urine Formation. 3 Processes Glomerular Filtration Glomerular filtrate Tubular Reabsorption Tubular fluid Tubular Secretion Tubular fluid. Figure 15.4. Glomerular Filtration. Nonselective, passive process

niabi
Télécharger la présentation

Urinary

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Urinary Part Two

  2. Urine Formation • 3 Processes • Glomerular Filtration • Glomerular filtrate • Tubular Reabsorption • Tubular fluid • Tubular Secretion • Tubular fluid Figure 15.4

  3. Glomerular Filtration • Nonselective, passive process • Fluid from blood passes into glomerular capsule = glomerular filtrate – blood plasma w/o blood proteins • Blood cells and proteins too large, when found in urine indication problem with glomerular filtration • If blood pressure normal, filtrate made, in blood pressure drops, no movement out of blood Figure 15.5

  4. Filtration Membrane • Plasma from capillaries of glomerulus to capsular space – pass thru 3 barriers • Fenestrated endothelium – capillaries are honeycombed, larger pores • Basement membrane of capillary – proteoglycan layer, size and charge (-) • Filtration slits – podocytes octopi w/pedicels

  5. Glomerular Filtration Rate (GFR) • Filtrate formed/min by both kidneys • Men 180L/day • Women 150L/day • 50-60X blood plasma so what’s going on? • Reabsorb 99% of filtrate as forming urine

  6. Regulation of Glomerular Filtration • GFR regulated • Too fast or too slow? • Have to change the glomerular pressure – 3 homeostatic mechanisms • Renal autoregulation • Sympathetic Control • Renin-Angiotensin

  7. Regulation of GFR- Renal Autoregulation • Nephrons adjust own blood flow and GFR with hormonal or nervous control • Limited – doesn’t work at extremes! • Even as Mean Arterial Pressure (MAP) varies, filtrate production remains consistent • Helps ensure stable fluid and electrolyte balance • Two mechanisms • Myogenic Mechanism • Tubuloglomerular feedback

  8. Myogenic Mechanism • Stabilizing GFR with smooth muscle contraction • Arterial BP rises, stretches afferent arteriole • SM constrictions prevents blood flow into glomerulus from changing much • Arterial BP drops, SM relaxes, consistent blood flow • Consistent blood flow, consistent filtrate!

  9. Tubuloglomerular Feedback • Jusxtaglomerular apparatus (JGA) monitors fluid entering DCT and adjust GFR • 3 components • Juxtaglomerular (JG) cells – SM found in afferent arteriole, some efferent. Stimulated by macula densa to constrict or relax. Also release renin • Macula densa – dense epithelial cells at start of DCT • Mesangial cells – connected to JG and macula densa cells via gap junctions and may communicate

  10. Regulation of GFR - Sympathetic Control • Sympathetic nerves innervate the renal BV • Stress and exercise – sympathetic nervous and epinephrine from adrenal gland cause constriction of afferent arterioles • Less GFR, less urine • Redirects blood to heart, brain, skeletal muscles

  11. Regulation of GFR – Renin - Angiotensin • When BP drops, sympathetic system stimulates juxtaglomerular cells to secrete renin. • Renin cleaves angiotesinogen (plasma protein) into angiotensin I. • In lung and kidneys, Angiotensin-converting exzyme (ACE) cleaves angiotensin I into angiontensin II (hormone)

  12. Functions of Angiotensin II • Stimulates vasoconstriction – incr. MAP • Constrict afferent and efferent arteriole – reduce GFR • Stimulates secretion of ADH, promotes water absorption • Stimulates secretion of aldosterone, promotes sodium and water retention • Stimulates sense of thirst, incr. water intake

  13. Tubular Reabsorption • In addition to waste, nutrients also in filtrate • H2O, glucose, a.a., ions • Reclaim from filtrate • PCT – tubule cells are “transporters”, take up from filtrate and pass out into extracellular space -> peritubular capillary blood • Some passive, some use carriers, are no carriers for substances body doesn’t need • Nitrogenous Waste Products – high concentrations in urine – urea, uric acid, creatinine • Ions absorbed or not depends on blood Figure 15.5

  14. PCT – Tubular Reabsorption • Reabsorbs 60% of filtrate, removes some waste from blood and secretes into tubules • Remember microvilli! • Cells have lots of mitochondria for ATP. PCT 6% of your resting ATP and calorie consumption • Two routes for reabsorption by PCT • Trancellular route • Paracellular route

  15. How does Sodium move? • Sodium is key to everything! • Creates osmotic and electrical gradient that drives movement of everything else. • Both transcellular and paracellular • More concentrated in tubule than cell, movement into epithelial cell by facilitated diffusion • First half of PCT – • moved by symport with glucose, AA, P, etc • H+ generated in cell from CO2-> bicarbonate rxn, Na-H antiport, Na in, H out • Second half PCT – [Cl] high, antiport Na and Cl

  16. More Sodium • Sodium only moves because of gradient • With all sodium going into cell, what happens to gradient? • Na-K pumps on basement and lateral membranes into ECF • Secondary active transport – some solutes transported with Na, and they rely on gradient which is powered by Na-K pump

  17. Chloride • Paracellular and transcellular • Cl- follows Na+ • Water reabsorption concentrates Cl and creates gradient in lower half of PCT • Some antiports

  18. Bicarbonate • Urine is bicarbonate free • Not reabsorb by nephron • Cells produce own bicarbonate molecules which diffuse into ECF picked up by blood

  19. Electrolytes and Glucose • K, Mg, Pi diffuse thru paracellular route with water • Most Ca is later but some via paracellular route • Sulfates and nitrates are waste, not reabsorbed • Glucose cotransported with Na = sodium-glucose transport proteins

  20. Water • Kidneys reduce 180L of filtrate to 1-2L of urine each day • Water reabsorption imp • 2/3 of water absorption by PCT • Water follows solutes via paracellular and transcellular routes (aquaporins) • PCT water absorbed at constant rate, regulated by hormones in other tubule areas

  21. Peritubular Capillaries • Reabsorption from ECF into peritubular capillaries by osmosis and solvent drag (movement of water drags solvents) • High interstitial fluid pressue • Low hydrostatic pressure in peritubular capillaries • High colloid pressure

  22. Tubular Secretion – PCT and Loop • From BV into tubule • Waste removal – urea, uric acid, bile acids, ammonia, catecholamines, creatinine, drugs, toxins • Acid-base balance – H and bicarbonate ions regulates pH

  23. Nephron Loop • Generate salinity gradient allows collecting duct to [urine] and conserve water • Reabsorbs 25% of Na, K, Cl and 15% of water. • Thick segment – cells bind 1Na, 1K, and 2Cl from tubular fluid and contransport into cytoplasm • K re-enters cell via Na-K pump, NaCl remains in tissue fluid of medulla • Water cannot enter thick segment, filtrate dilute as enters DCT

  24. DCT and Collecting Duct • Still contains 20% of water from glomerular filtrate – still doing reabsorption • Hormonal regulation!!! – aldosterone, atrial natruiretic peptide, ADH, and PTH • Two types of cells • Principal cells – more abundant, receptors for hormones, salt and water balance • Intercalated cells – lots of mitochondria, reabsorb K, secrete H, acid-base balance

  25. Aldosterone • Salt retaining hormone • Secreted by adrenal cortex • Drop in blood Na or incr in K stimulates release directly • Drop in BP – stimulates renin->angiotensin II-> stimulates release of aldosterone • Causes DCT and cortical part of collecting duct to reabsorb more Na (Cl and water follow) • Secrete more K • Urine volume is reduced, contains more K and less NaCl

  26. Atrial Natriuretic Peptide • Secreted by atrial myocardium in response to high BP • 4 actions to excrete salt and water in urine • Dilates afferent arteriole and constricts efferent, incr GFR • Antagonizes angiotensin-aldosterone mechanism, inhibits secretion of aldosterone and renin • Inhibits secretion of ADH and action on kidney • Inhibits NaCl reabsorption by collecting duct

  27. ADH • Secreted by Post Pituitary in response to dehydration and rising blood osmolarity • Makes collecting ducts more permeable to water

  28. PTH • Promotes Ca reabsorption by ascending loop of Henle and DCT • Also inhibits reabsorption of P by PCT • Prevents P from binding to Ca

  29. Collecting duct • Starts in cortex, multiple nephrons • In medulla, reabsorbs water and concentrates urine • Osmolarity of ECF is 4x as high in deep medulla than in cortex • Medullary part is more permeable to water than to NaCl • As pass thru CD, water leaves thru osmosis, NaCl and wastes remain

  30. Urine • Yellow color – urochrome, pigment form destroyed Hb, pale vs. darker, diet • Sterile when formed • pH is slightly acidic pH=6.0 • Diet can change, protein, wheat, or vegetarian • Some diseases or food can change smell • Substances not common in urine = glucose, blood proteins, RBCs, Hb, WBC, bile

  31. Abnormal Urinary Constituents

  32. Urinary Diseases • Urinary Retention – unable to expel urine • After surgery – anesthesia • Hyperplasia of prostate gland • May require catheter to avoid damage • Incontinence – unable to control external sphincter. • Ages 2 and younger • Sound sleepers • Emotional problems, pressure (pregnancy), Nervous system (stroke, spinal cord damage)

  33. Polycystic Kidneys • Congenital abnormality • Degenerative disease • Enlarged kidneys, blisters contain urine • Sac obstruct urine drainage • Can prevent infection, but renal failure inevitable. http://web.med.unsw.edu.au/pathmus/F1340092.htm

More Related