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excretion Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Excretory organs

A
  1. Lungs
  2. Skin
  3. Kidneys
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2
Q

products of excretory organs

A
  • Lungs- CO2 and water vapour + heat
  • Skin- sweat [water, salts + urea]
  • kidneys - urine [water salts + urea]
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3
Q

Where does urea come from

A

the breakdown of excess amino acids in the liver

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4
Q

Where are the kidneys located

A

below the diaphragm at the small of the back
abdominal cavity

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5
Q

How do the kidneys control the water content of the body

A

By varying the water content of the urine

ADH

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6
Q

How do the kidneys control the salt content of body fluids

A

by varying the ammount of salt released in the urine

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7
Q

How are the kidneys an osmoregulatory organ

A

By controlling the water and salt balance the kidneys ensure that blood plasma is the same concentration as the body cells. This means osmosis will not occur.

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8
Q

How do kidneys maintain the pH of bodily fluids at 7.4

A

By producing urine that is more or less acidic. It does this by secreting H+ ions from the blood into the cortex of the kidney.

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9
Q

Filtration

A
  • occurs from the glomerulus into the bowmans capsule
  • called ultrafiltration
  • its a passive non selective process
  • All small molecules pass through while large proteins and blood cells dont pass.
    *
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10
Q

Why does pressure force these small molecules

A
  1. the efferent arteriole is narrower than the afferent arteriole
  2. blood in the glomerulus is coming from the renal artery which is already under high pressure
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11
Q

Where does filtration occur in the kidney?

A

The nephron

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12
Q

Suggest a treatment that may be used for a person whose kidneys are not carrying out their
normal functions.

A

Transplant or dialysis

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13
Q

Give two features of the nephron that aid filtration

A
  1. Glomerular capillaries are very porous
  2. Thin walls- glomerulus and bowmans capsule consist of 1 layer of cells
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14
Q

What does the glomerular filtrate consist of

A
  • Glucose
  • amino acids
  • vitamins
  • salts
  • water
  • urea
  • uric acid
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15
Q

Reabsorption

A

High threshold substances are taken from the glomerular filtrate and returned to the blood

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16
Q

What substances are reabsorbed into the blood

A
  1. All amino acids, glucose and vitamins [active transport]
  2. most water 7/8 [osmosis]
  3. most salts [active trasnport]
  4. urea [diffusion, passively]
17
Q

Adaptions of the proximal convuluted tubule

A
  • microvilli increase surface area
  • one cell thick
  • many mitochondria for active transport
18
Q

Should glucose be present in urine

A

No- diabetes

19
Q

Secretion

A

Substances put into the nephron

20
Q

what substances are secreted and why
Give the location where they are secreted also.

A

Hydrogen and potassium ions are secreted into the distal convuluted tubule to maintain a blood ph of 7.4

21
Q

What causes low ADH levels

A
  1. High water intake
  2. Low salt intake
  3. High protein diet- excess aminoa cids converted to urea- higher leve of urea in urine.
22
Q

What happens if we drink alot of water

A
  • blood concentration falls and becomes dilute
  • This is detected by osmoreceptors in the hypothalamus which sends a message to the pituitary gland to stop releasing ADH
  • No ADH is released
  • The DCT and collecting duct remain impermeable to water allowing large volumes to pass into bladder.
  • Water levels in blood and body drop to normal levels.
23
Q

What causes high ADH levels

A
  1. excessive sweating
  2. low water intake
  3. high salt intake
  4. excercise
24
Q

What happens when the body doesnt have enough water

A
  • Blood becomes concentrated detected by osmoreceptors in the hypothalamus.
  • the hypothalamus sends a message to the pituitary gland to release the hormone ADH
  • This increases the permeability of the walls of the collecting duct.
  • more water is reabsorbed and a small volume of concentrated urine is produced.
  • There is a behavioural response to drink more water. (thirst sensation)

biology (7 decks)

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