Ch 26-Urinary System Flashcards
Kidneys
Organs that produce urine
Urinary tract-functions and organs
Organs that eliminate urine-ureters ( paired tubes) urinary bladder (muscular sac), urethra (exit tube)
Micturition
Process of eliminating urine
Homeostatic functions of the urinary system (5)
- Regulates blood volume and blood pressure
- Regulates plasma ion concentrations
- Helps stabilize blood ph
- Conserves valuable nutrients
- Assists liver
Kidney position maintained by….
Overlying peritoneum, contact with adjacent visceral organs, supportive connective tissues
Each kidney protected and stabilized by these 3 connective tissue layers…
- Fibrous capsule, layer of collagen fibers, covers outer surface of entire organ
- Perinephric fat, thick layer of adipose tissue, surrounds renal capsule
- Renal fascia, dense fibrous outer layer, anchors kidney to surrounding structures
Sectional anatomy of kidneys
Renal sinus, renal cortex, renal pyramids, renal columns
Kidney lobe consists of:
Renal pyramid, overlying area of renal cortex, adjacent tissues of renal columns
Blood flow through the kidneys
IN…
- Renal artery
- Segmental artery
- Interlobar artery
- Arcuate artery
- Interlobular artery
- Afferent arteriole
- Glomerular capillaries
- Efferent arteriole
- Peritubular capillaries (gas and fluid exchange occurs)
- Interlobular vein
- Arcuate vein
- Interlobar vein
- Renal vein…OUT
3 Functions of Urinary System
- Excretion
- Elimination
- Homeostatic regulation
Renal papilla
Ducts discharge urine into minor calyx, a cup-shaped drain
Major calyx
Formed by four or five minor calyces
Renal pelvis
Large, funnel-shaped chamber, consists of two or three major calyces, fills most of renal sinus, connected to ureter
Sympathetic Innervation
Adjusts rate of urine formation by changing blood flow and blood pressure at nephron
Stimulates release of renin
Release of renin
Restricts losses of water and salt in urine by stimulating re-absorption at nephron
Renal tubule
Long tubular passageway, begins at renal corpuscle
Renal corpuscle
Spherical structure consisting of: glomerular capsule, cup-shaped chamber, capillary network (glomerulus)
Filtration
Occurs in renal corpuscle
Blood pressure forces water and dissolved solutes out of glomerular capillaries into capsular space
Produces protein-free solution (filtrate) similar to blood plasma
3 Functions of Renal Tubule
- Reabsorb useful organic nutrients that enter filtrate
- Reabsorb more than 90% of water in filtrate
- Secrete waste products that failed to enter renal corpuscle through filtration at glomerulus
Segments of Renal Tubule
Located in cortex-PCT (proximal convoluted tubule), DCT (distal convoluted tubule), separated by nephron loop (loop of Henle)
Organization of Nephron
Traveling along tubule, filtrate gradually changes composition
Changes vary with activities in each segment of nephron
Each nephron empties into the__________
collecting system-a series of tubules that carries tubular fluid away from nephron
Collecting ducts
Receive fluid from many nephrons, Each duct begins in cortex, descends into medulla, carries fluid to papillary duct that drains into a minor calyx
Renal corpuscle function
Filtration, pressure forces water and solutes out of capillaries into capsular space, filtrate enters renal tubule where nutrients get reabsorbed
Visceral epithelium
Consists of large cells (podocytes) with complex processes or “feet” (pedicels) that wrap around specialized dense layer of glomerular capillaries
Filtration slits
Narrow gaps between adjacent pedicels, materials must be small enough to fit through these
Blood flow control
Special supporting cells (mesangial cells) between adjacent capillaries, control diameter and rate of capillary flow
Filtration membrane consists of…
Fenestrated endothelium, Dense layer, Filtration slits
Filtration at renal corpuscle
Is passive
Solutes enter capsular space-metabolic wastes and excess ions, glucose, free fatty acids, amino acids, vitamins
Reabsorption
Useful materials are recaptured before filtrate leaves kidneys, re-absorption occurs in PCT
3 Processes at the DCT
- Active secretion of ions, acids, drugs, and toxins
- Selective reabsorption of sodium and calcium ions from tubular fluid
- Selective reabsorption of water (concentrates tubular fluid)
Juxtaglomerular Complex (JGC)
Endocrine structure that secretes erythropoietin (EPO) and renin
Formed by: macula densa and JGC cells
Structures lined by transitional epithelium
Minor and major calyces, renal pelvis, ureters, urinary bladder, proximal portion of urethra
External Urethral Sphincter
Both sexes A circular band of skeletal muscle where urethra passes through urogenital diaphragm Acts as a valve Under voluntary control Has resting muscle tone
Internal Urethral Sphincter
In neck of urinary bladder, muscular and provides involuntary control of urine discharge
Goal of urine production
To maintain homeostasis…by: regulating blood volume and composition, Including excretion of metabolic waste products
Kidney functions
To concentrate filtrate by glomerular filtration (failure leads to fatal dehydration), absorbs and retains valuable materials for use by other tissues (sugars and amino acids)
Basic Processes of urine formation
- Glomerular filtration
- Tubular Reabsorption
- Tubular Secretion
Glomerular filtration
BP forces water/solutes across capillaries
Tubular reabsorption
removal of water/solutes from filtrate, reclaims water, electrolytes, and glucose
Tubular secretion
transport of solutes from, peritubular capillaries into tubular fluid (backup to filtration, excretion of toxins)
Urine=……
Glomerular filtration + tubular secretion - tubular reabsorption
3 organic waste products
- Urea
- Creatinine
- Uric acid
Where does filtration exclusively occur?
Renal corpuscle
Organic waste products….
Are dissolved in bloodstream, are eliminated only while dissolved in urine, removal is accompanied by water loss
Ways of expressing osmotic concentration
Osmolarity-osmoles per liter (Osm/L) or milliosmoles per liter (mOsm/L)
Ion concentrations, concentrations of large organic molecules
Glomerular filtration
Involves passage across a filtration membrane
3 Components of membrane
- Capillary endothelium
- Dense layer
- Filtration salts
Glomerular Filtration Rate (GFR)
Amount of filtrate produced by kidneys each minute
Myogenic mechanisms
how arteries/arterioles react to change in Blood Pressure
Reabsorption
Recovers useful materials from filtrate
Secretion
Ejects waste products, toxins, and other undesirable solutes
Reabsorption and secretion
Occur in every segment of nephron except renal corpuscle
Renin-angiotensin system
BV/BP decrease leads to drop in GFR= renin release
Renin converts angiotensinogen to angiotensin I
ACE converts antiotensin I to angiotensin II
Vasoconstriction=increase in BP/BV, restores GFR
ANP (atria) and BNP (ventricles)
Blood volume increases=GFR increases (speed up fluid loss in urine)
Dilation of afferent/constriction of efferent
Increases GFR, Na+ secretion
Nephron loop
reabsorbs about 1/2 water and 2/3 sodium and chloride ions remaining in tubular fluid
Countercurrent Multiplication
Occurs between thin, descending limb and thick ascending limb
Countercurrent-exchange between tubular fluids moving in opposite directions
multiplication-refers to effect of exchange and increases as movement of fluid continues
Thin, descending limb
Permeable to water, not solutes (salts)
Thick ascending limb
Impermeable to water, active solute transport (Na+)
DCT
Reabsorption of Na+ and Cl-, secretion of K+, H+
CD
Reabsorption of Na+, HCO3-, urea
Aldosterone
Stimulates synthesis of Na channels/pumps=reduction in Na lost
pH drops
H+ into tubular fluid and reabsorb HCO3-
pH rises
secrete HCO3- and pumps H+ in
Obligatoy water reabsorption
Water movement that cannot be prevented
Facultative water reabsorption
ADH release=aquaporin (water channels) insertion into plasma membrane
Vasa recta
Reabsorption, maintains concentration gradient of medulla (vascular system)
Diuresis
Elimination of urine, indicates large volumes of urine
Diuretic therapy reduces…
Blood volume, blood pressure, extracellular fluid
Diuretics-Lasix
Given to decrease fluids in body (human) for CHF/edema
Given for nasal bleeding (horse)
Diseases of urinary system
Glomerulonephritis-inflammation of glomeruli, kidney stones, renal failure-kidneys unable to perform functions to maintain homeostasis
Seven steps of renal function
- Glomerulus
- Proximal Convoluted Tubule (PCT)-removal of ions
- PCT and Descending Limb-water moves into peritubular fluids, leaving highly concentrated tubular fluid/reduction in volume by water reabsorption
- Thick Ascending Limb-transport Na+ and Cl- out of tubule
- DCT and Collecting Ducts-final adjustments in tubular fluid conc, osmotic conc is adjusted through active transport
- DCT and Collecting Ducts-final adjustments cont. + exposure to ADH determines final urine conc.
- Vasa Recta-absorbs solutes and water reabsorbed by nephron loop, maintains concentration gradient
Aging problems on urinary system
Decline in functional nephrons, reduction in GFR, reduced sensitivity to ADH, micturition reflex problems