Chapter 10 : Excretion In Humans

Question 1

What is excretion

Answer 1

A process by which metabolic waste and toxic materials is removed from the organism’s body

Question 2

What waste products are excreted by the kidneys, skin and liver respectively

Answer 2

Kidneys
- urea
-excess water and salts

Skin
- urea
- excess water and salts

Liver
-bile pigments

Question 3

Describe blood circulation at the kidney tubule

Answer 3

1. Blood enters via the renal artery, which branches into many arterioles
2. Arterioles branch into a mass of blood capillaries (glomerulus)
3. Blood leaves glomerulus and enters blood capillaries surrounding kidney tubules
4. Blood capillaries then unite to form venules
5. Venules join to form renal vein and exits.

Question 4

Describe the process of ultrafiltration/glomerular filtration

Answer 4

1. High pressure blood passes through the afferent arteriole and into the glomerulus
2. High hydrostatic blood pressure forces water and other solutes out of the blood by ultrafiltration
3. Basement membrane wraps around the glomerular blood capillaries which has small pores that allow water and small molecules to pass through, keeping larger molecules like RBC and platelets out
4. Filtrate collects in the bowman’s capsule
5. Blood then leaves the glomerulus through the efferent arteriole

Question 5

1 difference btw afferent and efferent arteriole and the reason for it

Answer 5

The afferent arteriole has a larger diameter than efferent arteriole, maintain high hydrostatic blood pressure in the glomerulus

Question 6

Describe pathway of filtrate, starting from glomerulus

Answer 6

Glomerulus
Bowman’s Capsule
Proximal convoluted tubule
Loop of Henle
Distal convoluted tubule
Collecting duct

Question 7

Where does selective absorption begin ?

Answer 7

Proximal Distal tubule

Question 8

What materials are selectively reabsorbed in the PCT

Answer 8

Useful materials ( all glucose and amino acids as well as 85% of mineral salts )
80% of Water

Question 9

Adaptations of the PCT which help in selective reabsorption ?

Answer 9

Cells have many mitochondria to provide ATP for active transport
Microvilli to increase the SA for absorption

Question 10

What is reabsorbed in the loop of Henle

Answer 10

Water

Question 11

What is reabsrbed in the DCT

Answer 11

Water and some salts

Question 12

What’s is the composition of Urine (3)

Answer 12

Water
Nitrogenous waste (Urea, uric acid, creatinine)
Salts

Question 13

Describe the use of ADH

Answer 13

To signal the kidneys to take in more or less water in the DCT and collecting duct

Question 14

Where is ADH produces

Answer 14

Produces in the hypothalamus and secreted by pituitary gland

Question 15

Describe the process of osmoregulation when there is excess water

Answer 15

1. Water potential of plasma increases,
2. stimulating the release of less ADH
3. Less water is reabsorbed in the DST and the collecting duct

Question 16

Describe the features of a dialysis machine (7)

Answer 16

1. Partially permeable membrane : prevent diffusion of larger particles such as red blood cells
2. Long coiled tubing : increases SA:V, increasing diffusion of waste products
3. Same salt and glucose conc as blood : prevents diffusion of essential nutrients
4. No urea or nitrogenous waste in the blood : maintains conc grad ensuring fast rate of diffusion out of the xylem
5. Blood pump
6. Constant temp bath
7. Direction of blood flow opp dialysis fluid