kidney

Question 1

what are the excretory products of the lungs, kidneys and skin (organs of excretion)

Answer 1

lungs via blood plasma - carbon dioxide, made in respiring cells, made by respiration
kidneys & skin - urea, made in liver cells, made by breakdown of amino acids (deamination)

Question 2

how does the kidney carry out its roles of excretion?

Answer 2

• urea has been produced by liver, must be removed by another organ (kidney)
• kidney filters blood & removes any excess material and passes them to bladder to be excreted
• kidney contains millions of tiny structures called nephrons, these are the structures that filter the blood

Question 3

describe ultrafiltration in the bowman’s capsule and the composition of the glomerular filtrate

Answer 3

• diameter of efferent arteriole at exit of glomerulus smaller than diameter of afferent arteriole at entrance. this creates a build up of pressure in capillaries forming the glomerulus
• this pressure forces small molecules (urea, glucose, amino acids, salts) out of capillaries of glomerulus & into Bowman’s capsule. this forms the glomerular filtrate
• larger molecules (proteins, red blood cells) too big to fit across capillary walls so stay in blood
• capillaries of glomerulus have gaps between cells, the basement membrane surrounding the capillaries controls which molecules can pass into Bowman’s Capsule

Question 4

describe the structure of a nephron

Answer 4

nephron is made up of a kidney tubule which has several sections:
- Bowman’s capsule
- proximal convoluted tubule
- Loop of Henlé
- distal convoluted tubule
- collecting duct

surrounding the tubule is a network of capillaries with a knotted section which sits inside Bowman’s capsule

Question 5

why does selective reabsorption of glucose occur at the proximal convoluted tubule?

Answer 5

• filtrate travels to PCT, however it contains lot of useful materials such as glucose which would be wasted unless recovered
• specialised cells within walls of PCT, these move useful materials back into blood stream
• initially molecules move by diffusion, but some substances also moved against concentration gradient using ATP (active transport).

Question 6

what does urine contain?

Answer 6

water, urea, ions

Question 7

what is excretion?

Answer 7

the removal of toxic waste substances which have been made by cells

Question 8

what’s egestion?

Answer 8

the passing of undigested food as faeces through the anus

Question 9

where is urea formed?

Answer 9

liver cells

Question 10

how is urea made?

Answer 10

breakdown of amino acids (deamination)

Question 11

where’s urea excreted from?

Answer 11

the kidneys and skin

Question 12

which blood vessel carries oxygenated blood to the kidneys?

Answer 12

renal artery

Question 13

which tube carries urine from the kidney to the bladder?

Answer 13

the ureter

Question 14

go onto the summer work thing 2024 and try re-doing the diagram for the nephron’s labels

Answer 14

ok

Question 15

where does ultrafiltration occur in the nephron?

Answer 15

the glomerulus

Question 16

why do small molecules move from the capillaries of the glomerulus into the bowman’s capsule (forming the glomerular filtrate)?

Answer 16

• ultrafiltration
• build up of pressure in capillaries forming glomerulus (caused by efferent arteriole’s diameter < afferent arteriole’s diameter) forces them into Bowman’s capsule

Question 17

why’s there high pressure in the glomerulus?

Answer 17

• diameter of efferent arteriole (exit of glomerulus) &laquo_space;diameter of afferent arteriole (entrance)
• creates build up of pressure in capillaries forming glomerulus

Question 18

why is there no protein in the urine of a healthy person?

Answer 18

because larger molecules like protein or red blood cells are too big to fit through capillary walls, so stay in blood

Question 19

where does selective reabsorption occur in the nephron?

Answer 19

the proximal convoluted tubule (pct)

Question 20

what molecules are reabsorbed?

Answer 20

• all glucose, amino acids
• some salts
• 80% of water

Question 21

what transport processes occur to reabsorb glucose & amino acids (selective reabsorption)

Answer 21

active transport
also filtrate —> blood

Question 22

what transport processes occur to reabsorb water (selective reabsorption)

Answer 22

osmosis
also filtrate —> blood

Question 23

what transport processes occur to move harmful substances from blood to filtrate (selective reabsorption)

Answer 23

active transport

Question 24

what transport processes occur to filter ions from filtrate into blood (selective reabsorption)

Answer 24

active transport

Question 25

how are the cells in the PCT specialised for a fast rate of diffusion?

Answer 25

• folded membrane to increase surface area

Question 26

how are the cells in the PCT specialised for a fast rate of active transport?

Answer 26

they have many mitochondria to provide ATP for active transport

Question 27

where does concentration of the filtrate occur? (water reabsorption)

Answer 27

the loop of henle

Question 28

how does the loop of henle concentrate the urine?

Answer 28

• transports salt into blood by active transport
• this causes water to diffuse into blood by osmosis

Question 29

where does osmoregulation occur in the nephron?

Answer 29

the collecting duct

Question 30

what part of the brain detects the water concentration of the blood?

Answer 30

the hypothalamus

Question 31

if the blood is too concentrated, is more or less ADH released?

Answer 31

more - the blood doesn’t have enough water

Question 32

which part of the brain releases ADH?

Answer 32

the pituitary gland

Question 33

what effect does ADH have on the collecting duct (cd)?

Answer 33

• ADH is hormone, so carried in the blood
• cd surrounded by capillaries
• ADH diffuses out of blood, binds with receptors on surface of cd cells
• if ADH binds, this triggers wall of cd to become more permeable to water

Question 34

if there’s a high concentration of ADH in the blood, what’ll happen to urine production?

Answer 34

less urine will be produced; it’ll be more concentrated & darker in colour

Question 35

what is meant by the term osmoregulation?

Answer 35

osmoregulation is the regulation of water levels within the body to keep it rising or falling too much

Question 36

how can water levels be changed? (osmoregulation)

Answer 36

by adjusting the permeability of the collecting duct in the nephron

Question 37

describe urea formation

Answer 37

1. amino acids filtered into liver, along w rest of blood via hepatic artery & hepatic portal vein
2. excess amino acids can’t be stored & need to be broken down so they can be excreted. they’re broken down into carbs and ammonia
3. ammonia very toxic, must
   be converted into slightly less toxic chemical (urea)
4. amino acids that are needed + the urea are released back into blood stream via hepatic vein

Question 38

what are the three main sections of the kidney?

Answer 38

• around outside, lighter colour: cortex
• in middle are triangular shaped medulla
• in centre is the pelvis

(also contains millions of tiny structures, nephrons)