Urinary System PDF

URINARY SYSTEM COLOR OF URINE -color of urine is determined mostly by the breakdown products of red blood cell destruction *c...

URINARY SYSTEM COLOR OF URINE -color of urine is determined mostly by the breakdown products of red blood cell destruction *cleansing the blood and ridding the body of Liver-> “heme” of hemoglobin-> wastes water-soluble forms ->excreted into the bile and indirectly into the urine (urochrome) *regulation of pH and blood pressure Color can be affected by: *important in determining the concentration e.g liver diseases of red blood cells kidney stone dehydration *perform the final synthesis step of vitamin foods D production other illnesses Urine Glomerulus – 1st part of nephron -responsible for urine composition - means damaged glomerulus-> allowing protein to “leak” into the filtrate ketones in the urine suggests that the body is using fat as an energy source in preference to glucose -Inc KETONES: DM Type II or in a severe *bean-shaped; lie between the dorsal body deficiency of proteins or carbohydrates in cavity and the parietal peritoneum–extend the diet from the level of the T12 vertebra to the L3 vertebra Nitrates (NO3 – ) occur normally in the urine nitrate into nitrite (NO2 – ) by Gram (-) -> *right kidney is lower than the left adult ndirect evidence of infection kidney weighs about 150 gms, -approximately 12.5 cm x 7.5cm. x 2.5cm Should be no blood found in the urine; except in menstrual contamination -lateral surface is convex -medial surface is concave MAJOR COMPONENTS OF THE URINARY -medial surface has a vertical cleft called SYSTEM the hilus that leads to a space called the renal sinus 3 REGIONS OF THE KIDNEY 1. Outer Cortex - Light color, has granular appearance  - Inner medulla (reddish brown) Radiate Vein-> Arcuate Vein-> Interlobar - Exhibits cone-shaped masses called Vein-> Renal Vein-> Inferior Vena Cava medullary or renal pyramids 2. Renal pyramids - apices point towards the hilum - appear striped because they are formed by bundles of parallel tubules 3. Renal Pelvis - Funnel shaped: continuous w/ the ureter by adjusting the resistances of the afferent and efferent arterioles, the kidneys can regulate the hydrostatic pressures in both the glomerular and peritubular capillaries, changing the rate of glomerular filtration RENAL BLOOD FLOW and/or tubular reabsorption in response to body’s homeostatic demands *has 2 capillary beds: -glomerular capillaries THE NEPHRON -peritubular capillaries *arranged in series and separated by efferent arterioles that help regulate hydrostatic pressures in both sets of capillaries SUMMARY: Aorta-> Renal Artery-> Segmental Artery-> Interlobar Artery-> Arcuate Artery-> Cortical Radiate Artery-> Afferent Arteriole-> Glomerular Capillaries-> Efferent Arteriole-> Peritubular Capillaries-> Cortical functional unit of kidney: Layer of epithelial cells [ podocytes] Foot processes are separated by gaps X each kidney contains over 1 million called slit-pores thru which glomerular nephrons filtrate moves. *primary restriction point for plasma X has 2 major components: proteins is the basement membrane. glomerulus and tubules STRUCTURE OF A NEPHRON STRUCTURE OF A NEPHRON Glomerulus - tuft of capillaries that filters the blood; receives blood from afferent arteriole; empties blood into efferent arteriole function: filtration 3 MAJOR LAYERS OF GLOMERULAR CAPILLARY MEMB. WHICH MAKE UP THE FILTRATION BARRIER: Bowman’s capsule -surrounds the glomerulus and forms a double-walled chamber; its cavity opens into the proximal convoluted tubule Bowman’s capsule + glomerulus = renal corpuscle Tubular system -function: reabsorption and secretion Proximal convoluted tubule (PCT) lined by cuboidal epithelium loop of Henle Endothelium *thin segment –lined by squamous perforated by small holes [ fenestrae ] epithelium *thick segment –lined by cuboidal Basement membrane epithelium meshwork of collagen; proteoglycan fibrillae–strong negative charges repel the negatively charged albumin  adapted for absorption; readily absorbs solute and water from the tubule cells Juxtaglomerular Apparatus *region of nephron where the DCT comes in contact with the afferent arteriole *at the point of contact, both the afferent arteriole and the DCT are modified Tubular system Distal convoluted tubule (DCT) lined by cuboidal epithelium *Collecting duct fuse with other collecting tubules to form the papillary ducts 2 types of nephron: that empty into the renal papillae(calyces) àrenal pelvis 1.Cortical nephrons -mainly found in the cortex URETHRA 2.Juxtamedullary nephrons -located near the cortex-medullary junction = transports urine from the bladder to the outside of the body for disposal = the only urologic organ that shows any significant anatomic difference between males and females = begins inferior and central to the two ureteral openings forming the three points of Peritubular capillaries a triangular-shaped area at the base of the - arise from the efferent arteriole bladder (TRIGONE) that drain the glomerulus closely =posterior and inferior to the pubic associated with the renal tubules symphysis Transitional epithelium – lines proximal BLADDER urethra males: pseudostratified columnar epithelium between these cell types Nonkeratinized, stratified squamous – terminal urethra voiding involuntary ANS : internal urinary sphincter voluntary : external urinary sphincter = collects urine from both ureters =retroperitoneal FEMALE URETHRA = "dome" distends superiorly when the bladder is filling with urine external urethral orifice – in the ant vag wall, = females: lies anterior to the uterus inferior to the clitoris posterior to the pubic bone anterior to the Short length 4cm rectum -> > UTI in females =males: prostate is inferior to it Pudendal nerve- voluntary control =detrusor muscle : irregular crisscrossing bands of smooth muscle MALE URETHRA =interior: transitional cellular epithelium = Volumes: 500–600 mL passes through the prostate 20 cm length 4 regions Pudendal nerve- voluntary control *About 21% of the heart's output,:1200 ml/min for both kidneys *Only 20% of it goes through filtration, Glomerular filtration occurs when NFP amounting to a GFR of 125 ml/min (or 180 is positive liters per day) Glomerular hydrostatic pressure (blood pressure) pushes fluid into Bowman's *178.5 liters of this filtrate are reabsorbed capsule back into the bloodstream daily Opposing force: osmotic pressure exerted by solutes in glomerular capillary (higher *only about 1.5 liters of fluid per day to be than Bowman's) eliminated as urine Filtration limited by size (proteins mostly stay in blood) NFP: ~10 mm Hg (relatively low pressure) III. Disruptions in GFR Protein in filtrate: reduces blood protein concentration, lowers blood osmotic pressure Water moves from blood to tissues (edema) Urine volume increases due to higher osmolarity IV. Autoregulation of GFR Smooth muscle in afferent arterioles constricts with high blood pressure Limits blood flow and filtration rate, maintaining steady GFR Conversely, relaxes with low blood pressure to maintain flow and filtration Physiology of Urine Formation I.GFR =volume of filtrate formed by both kidneys per minute (important indicator of kidney function) II. Factors Influencing GFR Net Filtration Pressure (NFP): Difference between hydrostatic & osmotic pressures Hydrostatic pressure: pressure exerted by fluid against a surface V. Clinical Significance of GFR Osmotic pressure: pressure created by GFR assessment helps diagnose kidney movement of solvent (water) across a diseases and drug dosing membrane  GFR estimated using creatinine clearance (creatinine not reabsorbed) 2 main mechanisms: Inulin (plant polysaccharide) is the most 1.Renal Autoregulation accurate method (not routinely used) -Intrinsic mechanism in the kidney VI. Blood Pressure and GFR -Inc BP -> smooth muscles in AA Mean arterial pressure (MAP) used to constricts-> inc pressure-> significant GFR estimate glomerular blood hydrostatic inc is prevented pressure (GBHP) MAP sufficient to maintain GFR must be --dec BP -> arterioles relax-> more blood above 60 mm Hg flow-> GFR maintained Low blood pressure (shock) impairs renal function 2.Glomerulotubular Balance -communication between the glomerulus Unlike glomerular filtration, which is and the renal tubules relatively nonselective, tubular -Inc BP-> GFR inc-> tubules react-> inc reabsorption is highly selective. reabsorption rate of more water and solutes-> dec GFR-> maintains stable urine Reabsorption of water & solutes includes output (PRESSURE DIURESIS/ active or passive transport mechanisms as PRESSURE NATRIURESIS) in other cell membranes. Renal blood flow is tightly regulated to Eventually urine that is formed & all the maintain a constant GFR despite substances in the urine represent the sum fluctuations in overall blood pressure. of 3 basic renal processes: Here's a breakdown of the two main mechanisms: Glomerular filtration Tubular reabsorption Tubular secretion 1.Renal Autoregulation: This is an intrinsic mechanism within the kidneys Normal adults: GFR averages 125 ml/ themselves. When blood pressure min or 180 L/day. increases, the smooth muscle in the The kidneys filter 180 L/day -> excrete a afferent arterioles (vessels bringing small volume (1.5 L/day) of urine. blood to the glomerulus) constricts. This =99% of the filtrate is reabsorbed back constriction resists the increased into the bloodstream by the tubules (178.5 pressure and prevents a significant rise L/day) in GFR. Conversely, when blood remains stable despite blood pressure pressure drops, these arterioles relax to changes due to Two key mechanisms allow more blood flow and maintain 1.Renal autoregulation GFR. 2.Glomerulotubular balance 2.Glomerulotubular Balance: This Renal blood flow mechanism involves communication between the glomerulus and the renal =stimulates aldosterone release from the tubules. When GFR increases due to adrenal cortex, causing the collecting duct higher blood pressure, the tubules to retain Na+ , which promotes water "sense" this change and amp up retention and a longer-term rise in blood pressure (increase) their reabsorption rate. This effectively reclaims more water and ADH= promotes water recovery by the solutes from the filtrate, counteracting collecting ducts by stimulating the insertion the rise in GFR and keeping urine of aquaporin water channels into cell output stable. This process is also called membranes pressure diuresis or pressure natriuresis (increased excretion of sodium and Endothelins =elevated in cases of diabetic water with high pressure). kidney disease, increasing Na+ retention and decreasing GFR. JUXTAGLOMERULAR APPARATUS (JGA) --- Atrial Natriuretic Peptide (ANP)= -located in the kidney within each nephron released primarily from the atria of the heart JGA is found between the afferent arteriole in response to stretching of the atrial walls, (bringing blood into the glomerulus) and the stimulate Na+ excretion and thereby thick ascending limb of Henle's loop (part of decrease blood pressure the renal tubule) PTH=stimulates the final step in the Renin -> increase formation of angiotensin I formation of active vitamin D3 and reduces -> to angiotensin II ->constricts the efferent phosphate reabsorption, resulting in higher arterioles ->increasing glomerular HP & circulating Ca++ levels returning GFR to normal Beyond Urine Production: The Crucial ENDOCRINE REGULATION OF KIDNEY Roles of Healthy Kidneys FUNCTION *Strong Bones: Kidneys activate the final step in creating the "active" form of vitamin Endocrine hormones =act from a distance D, essential for calcium absorption and paracrine hormones=act locally strong bones. (The Renin-Angiotensin-Aldosterone Oxygen Delivery: EPO System (RAAS)) Renin= renal; converts angiotensinogen Blood Pressure Control: by balancing into angiotensin I sodium and water levels in the body. ACE= lungs; converts angiotensin I into Stable Blood Chemistry: healthy balance active angiotensin II of electrolytes, especially sodium, calcium, and potassium Angiotensin II =active vasoconstrictor that increases blood pressure Healthy pH: regulate blood pH