excretion Flashcards
functions of the kidney
-excretion - removing urea from the circulating blood
-osmoregulation - regulating the water content of the blood
where is urea made?
-made in the liver, from the deamination of amino acids
what is the renal cortex?
-outer portion of the kidney
what is the renal medulla?
-inner portion of the kidney, which consists of a number of renal pyramids
what is the renal pelvis?
-funnel-shaped chamber where urine flows from collecting ducts to the ureter
what is the nephron?
-the nephron is the functioning unit of the kidney
-nephrons/ kidney tubules
functions of the nephrons
-ultrafiltration
-selective reabsorption
what is the afferent arteriole?
-branch of the renal artery
-blood containing water, useful molecules and waste materials are delivered from the circulation
what is the efferent arteriole?
-diameter is smaller than the afferent arteriole, creating a high hydrostatic pressure in the glomerulus
what is bowman’s capsule?
-where ultrafiltration takes place
-wastes and small molecules like glucose, amino acids, mineral ions and water are filtered into the nephron
what is the proximal convoluted tubule?
-useful molecules like glucose and amino acids are selectively reabsorbed into the blood (flowing in capillaries surrounding the nephron)
what is the loop of henle?
-aids in the reabsorption of water
what is the distal convoluted tubule?
-reabsorbs water and mineral ions into blood
what is the collecting duct?
-under the influence of anti-diuretic hormone, the permeability of the walls of the collecting duct can change to aid in reabsorption of water
what is renal venule?
-blood containing useful molecules and water but removed of wastes is returned to the circulation
processes of the formation of urine
-ultrafiltration at bowman’s capsule and glomerulus
-selective reabsorption at proximal convoluted tubule, loop of henle, distal convoluted tubule, collecting duct
-secretion at distal convoluted tubule
what is ultrafiltration?
-ultrafiltration is the passage of solutes and water out of the glomerulus, driven by the pressure exerted by the blood.
what is the process of ultrafiltration?
-the diameter of the afferent arteriole is larger than the efferent arteriole, creating a high hydrostatic blood pressure in the glomerulus that drives ultrafiltration
-small molecules (water, glucose, amino acids, urea and ions Na+, Cl-, HCO3-) are forced out of the glomerulus (a network of capillaries) into the bowman’s capsule, forming the glomerular filtrate
-large particles and cells (proteins and fats, blood cells) cannot pass the glomerulus
what is selective reabsorption?
-selective reabsorption is the selective uptake of solutes and water through processes such as osmosis, active transport and diffusion
what is the process of selective reabsorption?
-salt and water are selectively/ partially reabsorbed
-glucose and amino acids are entirely reabsorbed
-urea is not reabsorbed in large amounts
composition of urine in a healthy person
-contains water, urea and some mineral salts
-protein rich diet results in increased urea in urine
-drinking more water results in increased volume of urine, urine is more dilute
-diet high in salt results in increased mineral salts excreted in urine
composition of urine suffering for diabetes
-contains glucose, water, urea and mineral salts
-diabetics have high blood glucose levels, especially after meals
-this results in high glucose concentration in glomerular filtrate during ultrafiltration
-the proximal convoluted tubule is unable to absorb all the glucose
-resulting in excess glucose being excreted in urine
what is osmoregulation?
-osmoregulation is the control of water and solute concentrations in the blood to maintain a constant water potential in the blood plasma
when there is insufficient intake of water and/ or increased water loss
-blood plasma has a more negative water potential than norm
-more ADH is released into the blood, that targets the walls of the collecting duct of the nephron
-more ADH causes the permeability of the walls of the collecting duct to increase
-more water is absorbed into blood
-lower volume of urine produced. urine contains lower water content of water, and tends to be concentrated.
-water potential of the blood rises.
when there is increased intake of water and/ or decreased water loss
-blood plasma has a less negative water potential than norm
-less ADH is released into the blood, that targets the walls of the collecting duct of the nephron
-less ADH causes the permeability of the walls of the collecting duct to decrease
-less water is reabsorbed into blood
-higher volume of urine produced. urine contains a higher content of water, and tends to be more dilute.
-water potential of the blood falls.
