Excretion

Question 1

What is excretion

Answer 1

removal of the waste substances of metabolic reactions (the chemical reactions that take place inside cells), toxic materials and substances in excess of requirements.

Question 2

What are metabolic reaction in plant and their waste and where it takes place

Answer 2

• two main metabolic reactions are aerobic respiration and photosynthesis.
  1. waste product of aerobic respiration is carbon dioxide
  2,waste product of photosynthesis is oxygen
  ** plants don’t contain specialised excretory organs and excretion of these gases happen through the stomata.

Question 3

what is the excretory products of the lungs

Answer 3

mainly excretes: Carbon dioxide

* lungs excrete CO2 during exhaltion

Question 4

what is the excretory products of the kidney

Answer 4

excretes : urea, excess water and salts.

* excrete those by making urine

Question 5

what is the excretory products of the skin

Answer 5

excretes: water salt urea
* excretes them through sweat glands on skin by making sweat, and H2O is not excreted cause it excess but to cool the body down.

Question 6

What is osmoregulation

Answer 6

Is the control of water content in the body, and an example of homeostasis.

Question 7

how the kidney carries out its roles of excretion and osmoregulation

Answer 7

1. removes urea, excess water and excess salts from the blood as it passes through its internal structures
   2, this way it acts as an excretory organ.
   3.excretory products form urine, which is taken to bladder where it is stored.
   * Before urine leaving the body water is regulated depending how much of it is in the blood.
2. This is monitored by the brain and communicated to kidney by ADH.
3. Depending on the level of ADH in the blood, the kidney will reabsorb more water from the urine
   *this way it acts as an osmoregulatory organ.

Question 8

function of renal artery

Answer 8

Carries oxygenated blood which contains urea, salts and water to kidney

Question 9

function of kidney

Answer 9

Two bean shaped organs that filter the blood.

Question 10

function of ureter

Answer 10

tube that connects kidney to bladder

Question 11

function of bladder

Answer 11

Organ that stored urine as it is produced by the kidney.

Question 12

function of Urethra

Answer 12

Tube that connects bladder to the exterior where urine is released.

Question 13

function of Renal vein

Answer 13

Carries deoxygenated blood that had been filtered away from the kidney.

Question 14

What is the nephron

Answer 14

The nephron is the functional unit of the kidney
This is where filtration of the blood takes place
* Small sturtures hat each have their own blood supply branching off the renal artery and are responsible for filtering a small amount of blood.

Question 15

Function of the bowman’s capsule in the nephron

Answer 15

Connects filtrate forced out of the glomerulus and allows it to enter kindey tubules

Question 16

Function of the glomerulus in the nephron

Answer 16

Filters blood by increasing pressure to produce filtrate that enters Bowman capsule

Question 17

Function of the Convuluted tubules in the nephron

Answer 17

Glomerular filtrate flows through these and useful substances in the filtrate are reabsorbed back into blood capillaries wound around them

Question 18

Function of the loop of henle in the nephron

Answer 18

Maintain water concentration in the body by filtering out salts.

Question 19

Function of the Collecting duct in the nephron

Answer 19

reabsorbs water back into the blood depending on levels of ADH in blood and collects urine and pass on to the ureter.

Question 20

What is the process of ultrafiltration

Answer 20

1. The glomerus is a knot of capillaries sitting inside bowman capsule.
2. The capillaries get narrower further into the glomerus therefore there is increase in pressure of blood.
3. This eventually causes smaller molecules being carried to blood to be forced out into Bowman’s capsule, it’s known as the filtrate
   * this is known as ultrafiltration
   substances forced out of the capillaries are: glucose, water, urea, salts

Question 21

What substances are reabsorbed and where in the nephron

Answer 21

water : collecting duct
salts : loop of henle
glucose : proximal (first) convuluted tubule
urea : not reabsorbed

Question 22

how water and salts is reabsorbed into the blood in the nephron

Answer 22

1. the filtrate drips through the loop of henle and thats where salt’s are reabsorbed back into the hair.
2. This lowers the water concentration in that part of nephron
3. The urine from the loop of henle goes to the collecting duct where some water moves out of the urine through the walls of collecting duct by osmosis.
   * walls for collecting duct are vert permeable to water.
   the permeability of water depends on how much water needs to be reabsorbed into the blood

Question 23

The role of ADH in regulating the water content of the blood if too low

Answer 23

• ADH alters the permeability of the collecting duct to water
  1. If there is too little water in blood ( after exercise) ADH is secreted in larger amounts by the pituitary gland.
  2. this makes collecting duct more permeable to water therefore more water is reabsorbed
  3. this increases the water content in the blood,
  4. Urine that is produce will be darker as it is concentrated in more urea and salts.

Question 24

The role of ADH in regulating the water content of the blood if too high``

Answer 24

1. If there is too much water in blood ( after drinking water) ADH is secreted in lower amounts by the pituitary gland.
2. this makes collecting duct less permeable to water therefore less water is reabsorbed
3. this decreases the water content in the blood,
4. Urine that is produce will be light as less concentrated in urea and salts and higher in volume

Question 25

why selective reabsorption of glucose occurs at the proximal convoluted tubule

Answer 25

1. Glucose is the first substance to be reabsorbed at the proximal (first) convoluted tubule by active transport
   * Nephron is adapted to this as it has a lot of mitochondria to give energy for active transport.
2. Glucose absorption can’t take place anywhere else as e in the nephron as the protein gates that facilitate the active transport of glucose are only found in the proximal convoluted tubule.

Question 26

How do know if people have diabetes

Answer 26

1. People with normal blood glucose would have enough gates present to remove all of the glucose from the filtrate back into the blood.
2. People with diabetes cannot control their blood glucose levels and they are often very high, meaning that not all of the glucose filtered out can be reabsorbed into the blood in the proximal convoluted tubule.
   * This is why doctors check the urine for presence of glucose to figure out if person is diabetic as there is nowhere else for the glucose to be reabsorbed, it continues in the filtrate and ends up in urine.