Urinary System Anatomy Saladin
Filtration Membrane
1. Fenestrated endothelium 2. Basement membrane 3. Filtration slits
Organs of urinary system
Kidneys (2) Urinary bladder (1) Ureters (2) Urethra (1)
Major functions of kidneys
1. Filters blood plasma 2. Regulate blood volume/pressure, and osmolarity 3. Stimulates production of red blood cells 4. Regulate PCO2 and acid-base balance 5. Calcium homeostasis
4 Body systems that carry out excretion
1. Respiratory 2. Integumentary 3. Digestive 4. Urinary
Mesangial cells
Cells b/w arterioles and amongst glomerular capillaries
Juxtamedullary nephrons
15% of all nephrons Very long nephron loops Maintain salinity gradient in medulla and help conserve water Efferent arterioles branch into vasa recta around long nephron loop
Renal pyramids
6 - 10 with broad base facing cortex and renal papilla facing sinus
Cortical nephrons
85% of all nephrons Short nephron loops Efferent arterioles branch into peritubular capillaries around PCT and DCT
Hormones that regulate the amount of water and salt reabsorbed by DCT and collecting duct
Antidiuretic hormone Aldosterone Atrial natriuretic peptide
Waste
Any substance that is useless to the body or present in excess of the body's needs
Distal convoluted tubule
Begins shortly after ascending limb reenters cortex Shorter and less coiled Cuboidal epi w/o microvilli (brush border) End of nephron
Interlobular artery
Branch into afferent arterioles Each supply 1 nephron Leads to glomerulus
Glomerulus
Capillary bed fed by afferent arteriole and drained by efferent arteriole
Filtration pressure at glomerulus is determined by balance of
Colloid Osmotic pressure Hydrostatic pressure
Primary function of nephron loop is to generate a medullary ECF osmotic gradient that allows the ____ of urine
Concentration
Ureters
Convey urine from kidneys to bladder
Minor calyx
Cup that nestles the papilla of each pyramid Collects urine
Sympathetic innervation
Decreases glomerular blood flow and rate of urine production Drop in blood pressure > secrete renin > activates hormonal mechanisms to restore BP
Nephron Loop (Loop of Henle)
Descending and ascending limbs Thick segments = simple cuboidal epi > Heavily engaged in active transport of salts, many mitochondria Thin segments = simple squamous epi > lower part of descending limb > cells very permeable to water
Renal artery
Divides into segmental arteries that give rise to: Interlobar a Articulate a Interlobular a
Kidneys play a major role in the regulation of
Electrolytes Acid-Base Balance
How kidneys regulate blood volume/pressure and osmolarity
Eliminate or conserve water Secrete renin
Renal vein
Empties into inferior vena cava
Interlobular veins
Empty directly into arcuate veins - interlobar veins
Macula Densa
Epithelial cells at end of nephron loop
Blood Urea Nitrogen (BUN)
Expression for level of nitrogenous waste Normal concentration is 10-20 mg/dL
Renal columns
Extensions of cortex that project inward toward sinus
Renal corpuscle
Filters blood plasma Glomerulus 2-layered glomerular (Bowman) capsule
Renal pelvis
Formed by convergence of 2 or 3 major calyces
Major calyces
Formed by convergence of 2-3 minor calyces
Renal fraction
Fraction of cardiac output received by kidneys 21%
Efferent arterioles in medulla
Give rise to vasa recta > supply nephron loop portion of nephron
Renal parenchyma
Gladular tissue that forms urine Appears c-shaped in frontal section 2 zones > Renal cortex & renal medulla
Flow of fluid in renal tubule
Glomerular capsule>PCT>Nephron loop>DCT>Collecting duct>Papillary duct>Minor calyx>Major calyx>Renal pelvis>Ureter>Urinary bladder>Urethra
How kidneys maintain calcium homeostasis
Help synthesize the hormone calcitrol (active vitamin D)
Effects of activation of Renin-Angiotensin System
Increased water retention Vasoconstriction Increased blood pressure Stimulate thirst Increased release of ADH Increased secretion of aldosterone
Efferent arterioles
Lead to either peritubular capillaries or vasa recta
Renal Tubule
Length of tube that includes the proximal convoluted tubule, nephron loop, distal convoluted tubule, and collecting duct
Renal tubule
Long coiled tube that converts filtrate into urine Leads away from glomerular capsule 4 regions > PCT, Nephron loop, DCT, Collecting duct
Proximal convoluted tubule
Longest and most coiled region Simple cuboidal epi with prominent microvilli (brush border) for majority of absorption
Renal sinus
Medial cavity Occupied by blood and lymphatic vessels, nerves, urine collecting structures
Order of structures a drop of urine will flow after it drains from the renal papilla
Minor calyx Major calyx Renal pelvis Ureter
Renal plexus
Nerves and ganglia wrapped around each renal a Follows branches of renal a into parachyma of kidney Issues nerve fibers to blood vessels and convoluted tubules
Urinary pole
Opposite side of corpuscle where renal tubule begins
Bowman capsule layers
Parietal (outer) = simple squamous epi Visceral (inner) = podocytes Capsular space separates 2 layers
Efferent arterioles in cortex
Peritubular capillaries > supply tissues near glomerulus, proximal and distal convoluted tubules
Variables that affect glomerular filtration rate
Permeability of filtration membrane Level of hydration
Glomerular filtration
Plasma filtered to form filtrate
Glomerular Filtration
Process by which water and solutes pass in blood plasma pass from glomerular capsule into capsular space
Creatinine
Produced of creatine phosphate catabolism
Uric acid
Product of nucleic acid catabolism
Collecting duct
Receives fluid from DCTs of several nephrons as it passes back into nephron Numerous collecting ducts converge toward the tip of medullary pyramid
Kidney Gross Anatomy
Receives renal nerves, blood vessels, lymphatics, and ureters
Kidneys regulate blood volume and blood pressure by
Regulating water output
Parts of nephron
Renal corpuscle Renal tubule
Nephron
Renal corpuscle and its renal tubules
Layers of protective connective tissue that surround kidney
Renal fascia - binds kidney to abdominal wall Perirenal fat capsule - cushions kidney and holds in place Fibrous capsule - encloses kidney and protects
Capsular pole
Side of corpuscle where afferent arterial enters corpuscle and the efferent arteriole leaves
Glomerular filtrate
Similar to blood plasma but contains little or no proteins
Kidneys and ureters are retroperitoneal or peritoneal?
Retroperitoneal Behind the peritoneum
Position of kidneys
Retroperitoneal Right kidney slightly lower due to large right lobe of liver
How kidneys stimulate red blood cell production
Secrete erythropoietin
Excretion
Separation of wastes from body fluids and the elimination
Cortical Nephrons
Short nephron loop Renal corpuscles near kidney surface
Juxtaglomerular cells
Smooth muscle cells w/i walls of afferent arteriole Dilate/constrict arterioles Release renin (when blood pressure drops)
Uremia
Syndrome of diarrhea, vomiting, dyspnea, and cardiac arrhythmia stemming from toxicity of nitrogenous waste Treatmenat > hemodialysis or organ transplant
Trigone
Triangular area within the bladder marked by the openings of ureters and the urethra
Ureter
Tubular continuation of renal pelvis that drains urine down to urinary bladder
Process by which fluids and solutes from the tubular fluid are moved into blood
Tubular reabsorption
Juxtaglomerular Apparatus
Tubuloglomerular feedback mechanism of GFR regulation
Metabolic waste
Waste substance produced by the body Includes nitrogenous waste
Nitrogenous waste
Urea formation Proteins > aminos > NH2 removed > forms ammonia, liver converts to urea
Urine is conveyed out of the body by a tube called the
Urethra
Parasympathetic innervation
Vagus nerve Increases rate of urine production Carries afferent pain fibers
Podocytes
Wrap around capillaries of glomerulus