Excretory System Urinary System

Kidney Filters 200 liters of fluid from the blood stream every day Eliminates toxins, excess ions, and metabolic wastes Returns needed substances to the blood

Other renal (kidney) functions: Regulates blood pressure (renin enzyme) Stimulates RBC production Metabolizes vitamin D to its active form

Renal Blood Flow Renal arteries take oxygenated blood to each kidney (1/4 of total cardiac output each minute) Renal veins: return blood from each kidney (low oxygen and high carbon dioxide) to the inferior vena cava

Renal Anatomy Renal capsule: outer covering Adipose capsule: fatty mass for cushioning blows Renal fascia: outer layer of dense fibrous CT that anchors the kidney to surrounding structures

Internal Renal Anatomy Renal cortex: light outer layer Renal medulla: darker middle layer Renal pyramids: in medulla Renal columns: separate pyramids Renal pelvis: flat, funneled tube Calyces: cups to collect urine

Nephron: Functional unit of the kidney Each kidney contains over 1 million of these tiny, blood- processing units

Kidney Physiology:3 Easy Steps Step 1: Glomerular Filtration Passive, Filtration Proteins and blood cells are too large to pass – would indicate filtration problems

Step 2: Tubular Reabsorption Most of tubule contents are reabsorbed to the blood Can be active or passive Almost all organic nutrients (glucose and amino acids) are reabsorbed to maintain plasma concentrations Reabsorption of water is constantly regulated. Also sodium, ions, nutrients are reabsorbed Urea, creatinine, and uric acid

Step 3: Tubular Secretion Helps dispose of substances not already in the filtrate – some drugs Eliminating urea and uric acid Getting rid of excess K+ Controls blood pH

Ureters Convey urine to the bladder Continuous with the renal pelvis

Urinary Bladder Storage tank for urine

Urethra Thin walled muscular tube Drains urine from the bladder (micturition)