Pack 6 – Excretory System

Question 1

Excretion

Answer 1

The process by which waste matter is expelled from an organism

Question 2

Water balance

Answer 2

The balance between water that is taken into the body (through fluids and food) and expelled from the body

Question 3

Urinary bladder structural features:

Answer 3

Sac composed of smooth muscle located in the pelvis, just above and behind the pubic bone

Question 4

Urinary bladder function:

Answer 4

Short term storage organ for urine that has travelled through the ureters from the kidneys

Question 5

Kidneys structural features:

Answer 5

• Two bean-shaped organs, each about the size of a fist
• They are located just below the rib cage, one on each side of your spine

Question 6

Kidneys function:

Answer 6

Water and essential nutrients are reabsorbed into the blood. Removes waste products and excess fluid from the body as urine

Question 7

Urethra structural features:

Answer 7

• Muscular tube
• In males this passes through the penis and in females it is embedded in the vaginal wall

Question 8

Urethra function:

Answer 8

Transports urine from the bladder to the exterior of the body during urination

Question 9

Nephron structural features:

Answer 9

Microscopic structures consisting of a glomerulus and tubule

Question 10

Nephron function:

Answer 10

• Functional unit of the kidney
• Filters blood

Question 11

Ureter structural features:

Answer 11

25-30 cm long tubes made of smooth muscle fibres, running from each kidney to the urinary bladder

Question 12

Ureter function

Answer 12

Drain urine from the kidneys to be stored in the bladder

Question 13

Two major regions in the kidney:

Answer 13

A lighter coloured outer region called the cortex, and a darker inner region called the medulla

Question 14

What is the medulla subdivided into?

Answer 14

Renal pyramids, which contain the nephrons (the tops of which extend into the cortex)

Question 15

What happens to water and waste in relation to the kidney?

Answer 15

Water and waste that is filtered out of the blood drains into the renal passage, and from there into the ureter

Question 16

How is blood supplied to and from the kidneys?

Answer 16

To the kidneys through the renal arteries, and leaves through the renal vein

Question 17

The 3 main processes by which filtering of the blood and forming the urine happens:

Answer 17

1. Glomerular filtration (ultrafiltration) - takes place in the renal corpuscle/Bowman’s capsule of the nephron
2. Reabsorption - takes place in the renal tubule of the nephron
3. Secretion - takes place in the renal tubule of the nephron

Question 18

What are the 2 parts of the renal corpuscle?

Answer 18

Bowman’s capsule and the glomerulus

Question 19

How is the filtrate formed in glomerular filtration?

Answer 19

As the blood flows through the glomerulus, plasma with dissolved glucose and ions filters across the walls of the capillaries into Bowman’s capsule

Question 20

What is within the renal tubule?

Answer 20

• Proximal convoluted tubule
  2. Loop of Henle
  3. The distal convoluted tubule

Question 21

Reabsorption in the kidney:

Answer 21

• Reabsorption is the selective transport of useful molecules and ions from the proximal convoluted tubule of the kidney nephron back into the blood
• Reabsorption can be by active transport or passive transport depending on the substance

Question 22

Water reabsorption in the kidney:

Answer 22

• 99% of water is reabsorbed - By osmosis down its concentration gradient in the proximal and distal convoluted tubules and the Loop of Henle
• Extra water can be reabsorbed from the Loop of Henle into the blood to regulate the water concentration of the blood

Question 23

Glucose reabsorption in the kidney:

Answer 23

100% of glucose is reabsorbed - By active transport against its concentration gradient in the proximal convoluted tubule

Question 24

Sodium reabsorption in the kidney:

Answer 24

Sodium ions are reabsorbed – In the proximal convoluted tubule and Loop of Henle

Question 25

Secretion in the kidney:

Answer 25

- Secretion is when molecules move from the plasma in the capillaries into the filtrate in the tubule - Secretion can be by active transport or passive transport depending on the substance

Question 26

Excretion in the kidney:

Answer 26

- Urine made in the kidneys is pushed down the ureters by peristalsis - The ureters empty in to the bladder, which stores urine - When it gets full, stretch receptors in the walls of the bladder tell the brain this - The brain then sends signals to the sphincter muscles to relax, allowing urine to pass out of the body through the urethra

Question 27

How does the kidneys maintain water balance:

Answer 27

If the solute concentration of the blood is too high, the blood needs to become more dilute (needs more water in it)

Question 28

How does the body deal with high solute concentration in relation to the brain:

Answer 28

- Cells called osmoreceptors in the hypothalamus of the brain detect the rise in solute concentration - This stimulates the pituitary gland to release (ADH) from the pituitary gland - ADH travels in the blood to the kidneys, where it causes the kidneys to reabsorb more water

Question 29

How does the body deal with high solute concentration in relation to a human:

Answer 29

- The osmoreceptors also stimulate the thirst centre of the brain, so the person drinks more water - The water volume of the blood increases so the solute concentration decreases - With an increase in blood volume, blood pressure also increases

Question 30

How does the body deal with low solute concentration?

Answer 30

- Cells called osmoreceptors in the hypothalamus of the brain detect the fall in solute concentration - This stimulates the pituitary gland to reduce the release antidiuretic hormone (ADH) from the pituitary gland - The kidneys reabsorb less water - The water volume of the blood decreases so the solute concentration increases

Question 31

What is the effect of water balance control on blood pressure?

Answer 31

- A drop in blood volume due to a net loss of water would lead to a drop in blood pressure - This is detected by baroreceptors - Impulses from these baroreceptors pass to the hypothalamus - The hypothalamus triggers the release of more ADH from the pituitary gland - This causes the kidneys to reabsorb more water into the blood stream to increase the blood volume and consequently pressure