EXCRETORY SYSTEM

Function Disposes of wastes & excess ions Regulates volume & chemical makeup of blood by maintaining proper balance between water & salts, acids & bases UREA

Produces renin to regulate blood pressure & kidney function Produces erythropoietin to stimulate RBC production in bone marrow Metabolizes vitamin D to its active form

Organs   Kidneys Ureters Urinary Bladder Urethra

Anatomy of Kidney Bean-shaped Located between 12th thoracic vertebra and 3rd lumbar vertebra (partial protection) Rt. kidney lies lower than left Concave cleft on medial surface called- hilus which leads to the renal sinus

Adrenal Glands lie on top of each kidney 

External anatomy surrounded by renal capsule (protects from surrounding infection and trauma),   adipose capsule (holds kidneys in place and protects from trauma), renal fascia (anchors).

Internal anatomy renal cortex - outer region renal medulla - inner region with cone shaped renal pyramids renal columns separate pyramids renal pelvis - continuous with the ureter leaving the hilus major and minor calyces

Renal column Renal pyramid Renal calyx

Blood and Nerve Supply renal arteries - deliver 1/4 total cardiac output to kidneys per minute  lobar arteries interlobar arteries  arcuate arteries  Interlobular arteries

Nephron (this is where the action is!) Interlobar, Interlobular, Arcuate, Lobar, Renal veins  Renal Plexus – sympathetic nerve fibers

Nephron over 1 million/ kidney; filtering unit of kidney; results in production of urine 

renal corpuscle - consisting of glomerulus, Bowman's capsule proximal convoluted tubule (PCT)  loop of Henle

distal convoluted tubule (DCT)  collecting tubule (urine collecting duct) papillary ducts (collection of all collecting tubules)

Nephron

Bowman’s Capsule PCT DCT Loop of Henle Collecting Tubule Renal artery

7. Renal vein 8. Interlobular artery 9. Afferent artery 10. Glomerulus 11. Efferent artery 12. Peritubule capillaries

Kidney Physiology 3 Steps involved in kidney filtration Glomerular Filtration  Passive Mechanical

based on hydrostatic pressure enhanced by permeability of filtration membrane filtration membrane consists of 3 layers

porous endothelium - prevents passage of cells & large proteins thin basement membrane – charged to repel charged proteins

visceral membrane with slit-like openings; prevents passage of large plasma proteins Net Filtration Pressure – Glomerular hydrostatic pressure + Bowman's hydrostatic pressure (opposing forces)

Filtration Rate: rate at which fluid is forced from blood into Bowman's capsule; dependent upon: - surface area - filtration membrane permeability  - Net filtration pressure

Glomerular filtration rate is proportional to Net filtration pressure anything changing pressure at the membrane also changes the GFR, therefore higher blood pressure = higher GFR; dehydration = lower GFR

Tubular Reabsorption - reclamation of tubule contents difference b/t filtrate & urine filtrate - everything in blood plasma except proteins & cells urine - wastes & unneeded substances

reclamation begins in PCT (both active/passive transport) active - glucose; a.a., vit, Na, Ca, Cl, K, P,; most require a carrier molecule. When all carrier molecules are bound, excess are excreted into urine

passive - (diffusion, osmosis) usually tied to active transport of Na other anions move with Na to balance charges in the blood. The anions that move depend on the blood pH H2O moves passively (osmosis) due to its linkage to Na+

solvent drag occurs when filtrate becomes concentrated & solvent follows the concentration gradient back into the body Explains why some drugs & toxins are not excreted easily

Nonreabsorbed substances Urea (40% reabsorbed) Creatine uric acid Tubule absorption capabilities PCT most reabsorption occurs here Uric Acid

DCT permeable to Na but not H2O urine concentration determined here dependent on blood pressure or volume dependent on hormone release:

aldosterone - increases Na reabsorption & therefore H2O ANF - opposes this sex hormones glucocorticoids

Tubular Secretion – Reabsorption in reverse ammonia (secreted into the collecting tubule from the blood) Active process Some drugs (penicillin)

Pathology Suppression - holding back Pyuria - tract infection Ptosis (hydronephrosis) - kinked ureter Pyelonephritis – kidney inflammation

Pyelitis - inflammation of pelvis Anuria - no output due to low pressure Urethritis - inflammation of urethra Cystitis- inflammation of bladder

Dysuria- painful urination Incontinence - sphincter control Retention - involuntary suppression Diabetes insipidus – lack of ADH Addison's Disease – not enough aldosterone Excess Cl – indicate stone formation

Excess phosphates - alkaline urine Cushing's Disease - hyperaldosteronism  Dehydration – low GFR Hypotonic hydration – “water intoxication”; Hyponatremia, too much ADH Renal calculi – kidney stones