Overview of the Urogenital Overview of the Urogenital system: Urinary divisionsystem: Urinary division

KidneysKidneys UreterUreter

BladderBladder UrethraUrethra

The Urinary SystemThe Urinary SystemThe mammalian KidneyThe mammalian Kidney

Macroanatomy of the Kidney

Organs of the Urogenital systemOrgans of the Urogenital system

Kidney MacroanatomyKidney MacroanatomyFrontal SectionFrontal Section

Kidney RegionsKidney Regions

Cortex

Medulla

Pyramids

papilla

Renal PelvisRenal Pelvis

Minor calycesMinor calyces

Major calyxMajor calyx

Renal Artery and Renal Artery and VeinVein

artery branches artery branches and and vein vein tributariestributaries

Location and structure of nephronsLocation and structure of nephrons

Kidney FunctionKidney Function

Excretory FunctionExcretory FunctionFilters blood plasma, eliminates waste, Filters blood plasma, eliminates waste, returns useful chemicals to bloodreturns useful chemicals to blood

Homeostatic Functions Homeostatic Functions (Endocrine System)(Endocrine System)

Osmoregulatory FunctionOsmoregulatory FunctionRegulates osmolarity of body fluidsRegulates osmolarity of body fluids

Regulates blood volume and pressure Regulates blood volume and pressure Secretes renin, activates angiotensin, Secretes renin, activates angiotensin, aldosteronealdosterone

• controls BP, electrolyte balancecontrols BP, electrolyte balance

Secretes erythropoietin, controls RBC countSecretes erythropoietin, controls RBC count

Regulates PRegulates PCO2CO2 and acid base balance and acid base balance

GluconeogenesisGluconeogenesis

Kidney FunctionKidney FunctionExcretory -- Formation of Excretory -- Formation of UrineUrine

Filter and Excrete toxins, metabolic waste products, Filter and Excrete toxins, metabolic waste products, excess ions, organic acids, and nitrogenous wastes.excess ions, organic acids, and nitrogenous wastes.

Uric acid: Uric acid: results from results from the catabolism the catabolism of nucleic acidsof nucleic acids

Urea: Urea: derived from derived from the breakdown the breakdown of amino acidsof amino acids

Proteins Proteins amino acids amino acids NH NH22 removed removed forms ammonia which the forms ammonia which the liver converts to urealiver converts to urea

Creatinine: Creatinine: derived from derived from The breakdown of creatine The breakdown of creatine phosphate ( a molecule in phosphate ( a molecule in muscle that stores energy used in muscle that stores energy used in the synthesis of ATP)the synthesis of ATP)

The main waste products excreted in urine are The main waste products excreted in urine are the nitrogenous compounds.the nitrogenous compounds.

Kidney MicroanatomyKidney Microanatomy

Kidney MicroanatomyKidney Microanatomy

Nephron (renal tubule)

Glomerular capsuleProximal convoluted

tubuleLoop of Henle

Decending limbAscending limb

Distal convoluted tubule

Collecting Duct

Kidney Urine FormationKidney Urine FormationFiltration – Reabsorption – Filtration – Reabsorption –

SecretionSecretion

Kidney Urine FormationKidney Urine FormationFiltrationFiltration

Blood with all materials Blood with all materials entersenters the glomerular the glomerular capillariescapillaries Small molecules pass from Small molecules pass from the the capillaries into the capillaries into the capsular capsular spacespace sodium (Na sodium (Na ++))

HH22OO glucoseglucose potassium (Kpotassium (K++)) nitrogenous wastesnitrogenous wastes

These molecules are These molecules are filtered by cell membranes filtered by cell membranes based on size and chargebased on size and charge

Renal Renal CorpusleCorpusle

Kidney Kidney Filtration MembraneFiltration Membrane

Fenestrated endotheliumFenestrated endotheliumof the glomerular of the glomerular

capillariescapillaries70-90nm pores exclude 70-90nm pores exclude

blood cellsblood cells

• Basement membrane Basement membrane (main (main molecular filter)molecular filter)

Proteoglycan gel, negativeProteoglycan gel, negative charge excludes charge excludes molecules molecules > 8nm (ex. Proteins)> 8nm (ex. Proteins)

Filtration slitsFiltration slitsPodocyte (Podocyte (cells of the viseral cells of the viseral

layer of the glomerular capsulelayer of the glomerular capsule) ) arms have pedicelsarms have pedicels

with negatively chargewith negatively charge filtration slitsfiltration slits

Renal Renal CorpusleCorpusle

The filtration slitsThe filtration slits

The Juxtaglomerular apparatus: The Juxtaglomerular apparatus: senses BP in the afferent arteriolesenses BP in the afferent arteriole

Reabsorption in the Proximal Reabsorption in the Proximal Convoluted TubuleConvoluted Tubule

MechanismsMechanisms

Leakage or Diffusion Leakage or Diffusion through tight through tight junctionjunction

Active transportActive transport

Secondary active Secondary active transport-- transport--

antiportantiport

Facilitated diffusionFacilitated diffusion

Diffusion through Diffusion through membrane membrane channelchannel

Solvent Drag: Solvent Drag: HH22O O absorbabsorb by osmosis and drags by osmosis and drags solute along with itsolute along with it

• PinocytosisPinocytosis

Peritubular capillary

Epithelial cells

Tubular Fluid

Additional waste materials enter the Additional waste materials enter the tubule from the interstitial fluid by the tubule from the interstitial fluid by the same mechanisms which facilitated same mechanisms which facilitated reabsorption.reabsorption.

Waste removalWaste removalurea, uric acid, bile salts, ammonia, urea, uric acid, bile salts, ammonia,

catecholamines, many drugscatecholamines, many drugsAcid-base balanceAcid-base balance

secretion of hydrogen and secretion of hydrogen and bicarbonate ions bicarbonate ions regulates pH of body regulates pH of body fluidsfluids

Primary function of nephron loop Primary function of nephron loop water conservation, also involved in water conservation, also involved in

electrolyte electrolyte reabsorptionreabsorption

Secretion into theSecretion into theProximal Convoluted Proximal Convoluted Tubule Tubule and Nephron Loopand Nephron Loop

Summary of Molecules Reabsorbed

and Secreted

UrineUrine

Physical CharacteristicsPhysical Characteristics– Color: due to urochromate (pigment released Color: due to urochromate (pigment released

in hemoglobin catabolism)in hemoglobin catabolism)– Odor: Ammonia, due to bacterial metabolismOdor: Ammonia, due to bacterial metabolism– pH: ~6.0 (acidic) that varies with dietpH: ~6.0 (acidic) that varies with diet– Specific gravity: more dense than distilled Specific gravity: more dense than distilled

waterwater Chemical CharacteristicsChemical Characteristics

– 95% water, 5% solutes95% water, 5% solutes– Urea: Nitrogenous wastes from catabolism of Urea: Nitrogenous wastes from catabolism of

Amino Acids, creatine phosphate, etc.Amino Acids, creatine phosphate, etc.