Chapter 11: Excretion (incomplete)

Question 1

What are the 4 parts of a nephron?

Answer 1

1. Glomerulus
2. Bowman’s Capsule
3. Proximal convoluted tubule
4. Distal convoluted tubule

Question 2

Describe the process of ultrafiltration

Answer 2

1. Blood flows from the renal artery, through the wider different arteriole into the glomerulus
2. High hydrostatic pressure occurs at the glomerulus, due to the afferent arteriole being wider than the efferent arteriole.
3. The high hydrostatic pressure causes ultrafiltration of the blood where water and small molecules like amino acids, glucose, urea and mineral salts are forced through the partially permeable basement membrane of the glomerulus into the Bowman’s capsule, forming the filtrate
4. Blood cells, platelets and large molecules such as protein and fats are retained in the glomerular capillaries and do not pass into the Bowman’s capsule. These then flow out via the efferent arteriole.

Question 3

Define excretion

Answer 3

Excretion is the process by which metabolic waste and toxic substances are removed from the body of an organism

Question 4

Describe the concentration of substances in the renal artery

Answer 4

The renal artery has a higher concentration of oxygen and urea, and a lower concentration of carbon dioxide compared to renal veins

Question 5

Describe the concentration of substances in the renal vein

Answer 5

The renal vein has a lower concentration of oxygen(due to respiration) and urea(used in urine formation), and a higher concentration of carbon dioxide compared to renal arteries

Question 6

Describe the process of selective reabsorption

Answer 6

1. At the proximal convoluted tube, most of the mineral salts (sodium ions) and all glucose and amino acids are reabsorbed via diffusion and active transport, through the walls of the tubule, into surrounding blood capillaries. Most of the water in the filtrate is reabsorbed into the surrounding blood capillaries, by osmosis
2. At the loop of Henle, some water is reabsorbed by osmosis
3. At the distal convoluted tubule, some water and mineral salts are reabsorbed by osmosis and diffusion/active transport
4. At the collecting duct, some water is reabsorbed back by osmosis. Excess water, metabolic waste products such as urea, uric acid and creatinine pass out of the collecting duct into the renal pelvis as a mixture called urine.

Question 7

Describe the Urinary bladder and its functions

Answer 7

The urinary bladder is an elastic muscular bag located in front of the rectum to temporarily store urine.

Question 8

Define osmoregulation

Answer 8

Osmoregulation is the control of water and solute concentrations in the blood to maintain a constant water potential in the body

Question 9

Describe what happens when there is low water potential in the blood

Answer 9

1. Low water potential in the blood stimulates the hypothalamus in the brain to produce more antidiuretic hormone (ADH).
2. More ADH is stored temporarily at the pituitary gland and released from the pituitary gland.
3. The cell membranes of cels in the walls of the collecting cuts become more permeable to water. More water is reabsorbed from the collecting ducts into the blood capillaries
4. Smaller volume of urine is produced and urine is more concentrated.

Question 10

Describe what happens when there is high water potential in the blood

Answer 10

1. High water potential in the blood stimulates the hypothalamus in the brain to produce less antidiuretic hormones (ADH)
2. Less ADH is stored temporarily at the pituitary gland and released from the pituitary gland
3. The cell membranes of the cell in the walls of the collecting ducts become less permeable to water. Thus less water is reabsorbed from the collecting ducts into the blood capillaries
4. Larger volume of urine is produced and urine is more dilute.

Question 11

What are a few causes of kidney failure?

Answer 11

1. High blood pressure
2. Diabetes
3. Alcohol abuse
4. Severe accidents that physically damage the kidney
5. Complications from undergoing major surgery