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