excretion Flashcards
define excretion
-process by which metabolic waste products and toxins are removed from an organism’s body
define urea
-waste product from the deamination of excess amino acids in the liver
function of kidney
-filter waste products in the blood
-prevent accumulation of waste products that may be toxic
how does blood enter the kidney tubule
-blood enter kidney via renal artery
-renal artery branches into many arterioles
-arterioles further divide into mass of blood capillaries, glomerulus
-blood leaves renal corpuscle and enters tubule
-blood capillaries unite to form venules
-venules join to form renal vein
-blood exits kidney via renal vein
define ultrafiltration
-water and small molecules forced out from the blood due to high pressure in the glomerulus into the bowman’s capsule through basement membrane
define tubular reabsorption
-water by osmosis and essential molecules by active transport being reabsorbed from the kidney into the capillaries
describe the process of ultrafiltration
-in renal corpuscle, renal artery split up into arterioles each entering a nephron
-arterioles split into capillaries which form a knot, glomerulus, surrounded by bowman’s capsule
-afferent arteriole wider than efferent arteriole, blood pressure is high in capillaries of glomerulus
how does filtrate collect in bowman’s capsule
-high hydrostatic blood pressure forces plasma out of blood by ultrafiltration
-only blood cells, platelets and large plasma proteins and fats molecules with plasma remain
-basement membrane that wraps around glomerulus has small pores that allow water and small molecules to pass through
-filtrate collects in bowman’s capsule of renal corpuscle
what is selectively reabsorbed
-80 percent of filtrate in PCT is reabsorbed to ensure all useful materials is reabsorbed into blood
-all amino acids, glucose and 85% of mineral ions through active transport
-small proteins
-80% of water reabsorbed through osmosis in LoH, DCT, collecting duct
-some salts in DCT
-water salts and metabolic waste products like urea, uric acid and creatinine passes out of collecting duct into renal pelvis as urine
adaptations of proximal convoluted tube for selective reabsorption
-contains mitochondria to provide ATP for active transport
-microvilli that increase SA for absorption
effect of diabetes in glucose reabsorption
-maximum threshold is exceeded, active transport cannot keep out to reabsorb back the glucose
-excess glucose excreted in urine
what is the chemical composition of urine
-95% water 5% solutes
-nitrogenous waste include urea, uric acid and creatinine
-other solutes, sodium, potassium, phosphate, sulphate ions, calcium, magnesium, bicarbonate ions
-abnormal high concentration of any urinary constituents may indicate disease
mechanism of osmoregulation
-excess water detected by hypothalamus
-stimulate pituitary glands to secrete less ADH, less water reabsorbed by kidney tubules, urine excreted is more diluted
what is kidney dialysis
-process of removing excess fluids and toxins from the blood
-continually shunting patients blood from body into dialysis machine with a system of partially permeable membrane tubings surrounded by dialysis fluid for filtering
-returning clean blood to patient’s bloodstream
process of kidney dialysis
-blood drawn from patients artery
-blood pumped through tubing to DM
-semi permeable tubing bathed in dialysis fluid
-small molecules like urea and metabolic waste products diffuse out of tubing
-larger molecules like platelets and BC remain in tubing
-filtered blood return to patient’s vein
