Overview of the Urogenital system: Urinary divisionKidneysUreterBladderUrethra

The Urinary SystemThe mammalian Kidney

Macroanatomy of the Kidney

Organs of the Urogenital system

Kidney MacroanatomyFrontal SectionKidney RegionsCortexMedullaPyramids papillaRenal PelvisMinor calycesMajor calyxRenal Artery and Vein artery branches and vein tributaries

Location and structure of nephrons

Kidney FunctionExcretory FunctionFilters blood plasma, eliminates waste, returns useful chemicals to bloodHomeostatic Functions (Endocrine System)Osmoregulatory FunctionRegulates osmolarity of body fluidsRegulates blood volume and pressure Secretes renin, activates angiotensin, aldosteronecontrols BP, electrolyte balanceSecretes erythropoietin, controls RBC countRegulates PCO2 and acid base balanceGluconeogenesis

Kidney FunctionExcretory -- Formation of UrineFilter and Excrete toxins, metabolic waste products, excess ions, organic acids, and nitrogenous wastes.Uric acid: results from the catabolism of nucleic acidsUrea: derived from the breakdown of amino acids

Proteins amino acids NH2 removed forms ammonia which the liver converts to ureaCreatinine: derived from The breakdown of creatine phosphate ( a molecule in muscle that stores energy used in the synthesis of ATP)The main waste products excreted in urine are the nitrogenous compounds.

Kidney Microanatomy

Kidney MicroanatomyNephron (renal tubule)Glomerular capsuleProximal convoluted tubuleLoop of HenleDecending limbAscending limbDistal convoluted tubuleCollecting Duct

Kidney Urine FormationFiltration Reabsorption Secretion

Kidney Urine FormationFiltration Blood with all materials enters the glomerular capillaries Small molecules pass from the capillaries into the capsular space sodium (Na +) H2O glucose potassium (K+) nitrogenous wastes These molecules are filtered by cell membranes based on size and charge

Renal Corpusle

Kidney Filtration Membrane Fenestrated endotheliumof the glomerular capillaries70-90nm pores exclude blood cells

Basement membrane (main molecular filter) Proteoglycan gel, negative charge excludes molecules > 8nm (ex. Proteins)

Filtration slitsPodocyte (cells of the viseral layer of the glomerular capsule) arms have pedicels with negatively charge filtration slits

Renal Corpusle

The filtration slits

The Juxtaglomerular apparatus: senses BP in the afferent arteriole

Reabsorption in the Proximal Convoluted Tubule Mechanisms Leakage or Diffusion through tight junction Active transport

Secondary active transport-- antiport

Facilitated diffusion

Diffusion through membrane channel Solvent Drag: H2O absorb by osmosis and drags solute along with it

PinocytosisPeritubular capillaryEpithelial cellsTubular Fluid

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

Waste removalurea, uric acid, bile salts, ammonia, catecholamines, many drugsAcid-base balancesecretion of hydrogen and bicarbonate ions regulates pH of body fluidsPrimary function of nephron loop water conservation, also involved in electrolyte reabsorptionSecretion into theProximal Convoluted Tubule and Nephron Loop

Summary of Molecules Reabsorbed and Secreted

UrinePhysical CharacteristicsColor: due to urochromate (pigment released in hemoglobin catabolism)Odor: Ammonia, due to bacterial metabolismpH: ~6.0 (acidic) that varies with dietSpecific gravity: more dense than distilled waterChemical Characteristics95% water, 5% solutesUrea: Nitrogenous wastes from catabolism of Amino Acids, creatine phosphate, etc.