excretion

Question 1

functions of the kidney

Answer 1

-excretion - removing urea from the circulating blood
-osmoregulation - regulating the water content of the blood

Question 2

where is urea made?

Answer 2

-made in the liver, from the deamination of amino acids

Question 3

what is the renal cortex?

Answer 3

-outer portion of the kidney

Question 4

what is the renal medulla?

Answer 4

-inner portion of the kidney, which consists of a number of renal pyramids

Question 5

what is the renal pelvis?

Answer 5

-funnel-shaped chamber where urine flows from collecting ducts to the ureter

Question 6

what is the nephron?

Answer 6

-the nephron is the functioning unit of the kidney
-nephrons/ kidney tubules

Question 7

functions of the nephrons

Answer 7

-ultrafiltration
-selective reabsorption

Question 8

what is the afferent arteriole?

Answer 8

-branch of the renal artery
-blood containing water, useful molecules and waste materials are delivered from the circulation

Question 9

what is the efferent arteriole?

Answer 9

-diameter is smaller than the afferent arteriole, creating a high hydrostatic pressure in the glomerulus

Question 10

what is bowman’s capsule?

Answer 10

-where ultrafiltration takes place
-wastes and small molecules like glucose, amino acids, mineral ions and water are filtered into the nephron

Question 11

what is the proximal convoluted tubule?

Answer 11

-useful molecules like glucose and amino acids are selectively reabsorbed into the blood (flowing in capillaries surrounding the nephron)

Question 12

what is the loop of henle?

Answer 12

-aids in the reabsorption of water

Question 13

what is the distal convoluted tubule?

Answer 13

-reabsorbs water and mineral ions into blood

Question 14

what is the collecting duct?

Answer 14

-under the influence of anti-diuretic hormone, the permeability of the walls of the collecting duct can change to aid in reabsorption of water

Question 15

what is renal venule?

Answer 15

-blood containing useful molecules and water but removed of wastes is returned to the circulation

Question 16

processes of the formation of urine

Answer 16

-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

Question 17

what is ultrafiltration?

Answer 17

-ultrafiltration is the passage of solutes and water out of the glomerulus, driven by the pressure exerted by the blood.

Question 18

what is the process of ultrafiltration?

Answer 18

-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

Question 19

what is selective reabsorption?

Answer 19

-selective reabsorption is the selective uptake of solutes and water through processes such as osmosis, active transport and diffusion

Question 20

what is the process of selective reabsorption?

Answer 20

-salt and water are selectively/ partially reabsorbed
-glucose and amino acids are entirely reabsorbed
-urea is not reabsorbed in large amounts

Question 21

composition of urine in a healthy person

Answer 21

-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

Question 22

composition of urine suffering for diabetes

Answer 22

-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

Question 23

what is osmoregulation?

Answer 23

-osmoregulation is the control of water and solute concentrations in the blood to maintain a constant water potential in the blood plasma

Question 24

when there is insufficient intake of water and/ or increased water loss

Answer 24

-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.

Question 25

when there is increased intake of water and/ or decreased water loss

Answer 25

-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.