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Secondary 3 Biology > excretion in humans > Flashcards

excretion in humans Flashcards

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1
Q

what is metabolism?

A

the sum of all the chemical reactions within the body of an oganism
anabolism + catabolism = metabolism
- metabolic reactions produce metabolic waste products that are toxic to the body if they accumulate, must be removed

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2
Q

what is an example of anabolic reactions?

A

glucose –> glycogen

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3
Q

what is an example of catabolic reactions?

A

deamination of excess AA –> form urea

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4
Q

define excretion?

A

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

  • unicellular: diffusion
  • larger organisms : excretory organs (lungs etc)
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5
Q

what is the organ and mode of excretion for carbon dioxide?

A

lungs, expired air

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6
Q

what is the organ and mode of excretion for urea and excess mineral salts?

A

kidney and skin, urine and sweat

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7
Q

what is the organ and mode of excretion for excess water?

A

skin, lungs and kidneys , urine, sweat and expired air (water vapour)

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8
Q

what is the organ and mode of excretion for bile pigment (breakdown of haemoglobin)?

A

liver, faeces via intestines

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9
Q

what are the components of the human urinary system?

A
  1. pair of kidneys
  2. hilus
  3. ureters
  4. urinary bladder
  5. sphincter muscle
  6. urethrea
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10
Q

what is the function of the kidneys?

A
  • 10-13cm
  • attached to dorsal wall of absominal cavity
  • produce urine
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11
Q

what is the function of the hilus?

A
  • at the centre of kidney concave

- renal artery, renal vein, nerves are connected to kidney at hilus

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12
Q

what is the function of the ureters?

A
  • narrow tube in which urine from each kidney passes through, to urinary bladder
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13
Q

what is the function of the urinary bladder?

A
  • stores urine

- elastic muscular bag in front of rectum

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14
Q

what is the function of the sphincter muscle?

A
  • controls urination
  • when bladder is full, sensory neurons send nerve impulses to brain
  • brain sends nerve impulses to sphincter muscle to cause it relax
  • urine flows to urethra and out of body
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15
Q

what is the function of the urethra?

A
  • duct

- urine is discharged from bladder

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16
Q

what are the parts that form the kidney?

A
  1. cortex
  2. medulla
  3. medulla pyramids
  4. renal pelvis
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17
Q

what is the function of the cortex?

A
  • outer dark red region

- surrounded by fibrous capsule

18
Q

what is the function of the medulla?

A
  • inner pale red region

- contains 12 to 16 medulla pyramids

19
Q

what is the function of the medulla pyramids?

A
  • conical structures in medulla
  • radial stripes on MP indicate numerous kidney tubules (nephron)
  • urine is formed there, richly supplies with blood vessels
20
Q

what is the function of the renal pelvis?

A
  • medulla pyramids project into funnel-like space called RP

- it is the enlarged portion of ureter inside kidney

21
Q

what are the parts that form the nephron inside the kidney tubule?

A
  1. Bowman’s capsule
  2. proximal (first) convoluted tubule
  3. Loop of Henle
  4. Distal convoluted tubule
  5. collecting duct
22
Q

what is the function of the Bowman.s capsule?

A
  • each nephron begins in cortex with cuplike structure (Bowman’s capsule)
23
Q

what is the function of the PCT?

A
  • BC leads to a short, convoluted tubule which straightens out as it passes through medulla
24
Q

what is the function of the loop of Henle?

A
  • in medulla, tubule extends into renal pyramid and makes a U turn back into cortex
  • U-shape: Loop of Henle
25
Q

what is the function of the Distal convoluted tubule?

A
  • tubule becomes convoluted when enters cortex again
26
Q

what is the function of the collecting duct?

A
  • tubule opens to a collecting duct

- runs straight through medulla and opens into renal pelvis

27
Q

describe the blood circulation at kidney tubule?

A
  1. blood enters kidney by renal artery which branches out into arterioles
  2. each arterioles further branches out into a mass of blood capillaries in Bowman’s capsule, called glomerulus
    - Bowman’s capsule + glomerulus : renal corpuscle
  3. blood leaving glmerulus enters blood capillaries surrounding nephrons
  4. blood capillaries unite to form venules, which in turn join to form a branch of renal vein
28
Q

how is urine formed?

A

excess mineral salts and nitrogenous waste products are removed in the form of urine

29
Q

how is urine formed in kidneys?

A
  1. ultrafiltration

2. selective reabsorption

30
Q

describe ultrafiltration at renal corpuscle?

A

cause:
- high hydrostatic blood pressure at glomerulus
- because the afferent arteriole is wider than efferent arteriole that carries blood away
- this creates high bp at glomerulus
- high hydrostatic bp provides main force required for filtration
- partially permeable membrane that wraps around the glmerular blood capillaries is like a very fine filter
basement membrane:
- has very small pores only allowing water and small molecules to pass
- high b.p. in glomerulus forces water and small molecules (e.g. glucose, AA, mineral salts and nitrogenous waste products) into Bowman’s capsule, forming filtrate
- blood cells, platelets and large molecules such as proteins and fats are retained in glomerular capillaries

31
Q

describe how selective reabsorption returns useful substances to blood?

A
  1. at proximal convolued tubule, most mineral salts (sodium ions), and in a healthy person, all the glucose and AA are reabsorbed through walls of tubule into surrounding blood capillaries, via active transport and diffusion. The reabsorption is highly selective and only substances required by body are reabsorbed readily
    - most water in filtrate is reabsorbed by osmosis
  2. at loop of Henle, some water is rebaosbred
  3. at distal convoluted tubule, some water and mineral salts are reabsorbed
  4. at collecting duct, some water is reabsorbed. Excess water, excess salts and metabolic waste products e.g. urea, uric acid and creatinine pass out of collecting duct into renal pelvis as mixture called urine
32
Q

what is the composition of urine?

A

water: 96.0g
mineral salts: 1.8g
urea: 2.0g
other nitrogenous substances: 0.2g

33
Q

explain the different medical conditions?

A
  • protein rich diet: more urea due to excess deaminated AA in liver
  • more liquids: increased water potential of blood , large volume of urine
  • salty food: excess salts excreted
  • person with diabetes: large amount of glucose in urine as glucose cannot be stored as blycogen. High concentration of glucose in blood glucose filtered out of glomerulus to be part of glmerular filtrate. Nephrons are unable to reabsorb all glucose fast enough
34
Q

what is osmoregulation?

A

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

35
Q

further explain osmoregulation?

A
  • w.p. of the body has to be kept relatively constant (drastic changes: fatal)
  • w.p. depends on amount of water and mineral salts in blood plasma
  • amount of water in blood plasma is controlled by antidiuretic hromone (ADH)
  • produced by hypothalamus, released by pituitary gland
  • increases water reabsorption into the blood capillaries surrounding nephrons
36
Q

what happens when there is a large intake of water?

A
  1. w.p. in blood plasma increases
  2. stimulates hypothalamus in brain to produce less ADH
  3. causes pituitary glands to release less ADH into bloodstream
  4. cells in walls of collecting ducts become less permeable to water. Less water reabsorbed from collecting duct into blood capillaries
    - large volume of urine produced
    - urine produced in more diluted
  5. w.p. of blood plasma returns to normal
37
Q

what happens when there is a loss of water?

A
  1. w.p. in blood plasm decreases
  2. stimulates hypithalamus in brain to produce more ADH
  3. causes pituitary glands to release more ADH into bloodstream
  4. cells in wall of collecting ducts become more permeable to water. More water rebasorbed from the collecting duct into blood capillaries
    - smaller volume of urine produced
    - urine produced in more concentrated
  5. w.p. of blood plasm returns to normal
38
Q

what are the effects of osmoregulation?

A
  1. blood plasm too diluted: blood cells will absorb water, expand and burst
  2. blood plasma too concentrated: blood cells dehydrate and crenate
    - increase in blood volume causes increase in blood pressure. large increase may cause stroke
    - doctors provide diuretics: reduce ADH production.
    - large amount of dilue urine and volume of water in blood decreases, lowering b.p.
39
Q

what is the importance of kidneys?

A
  1. excretory organ
    - excretes metabolic waste products such as urea, excess water, mineral salts (as urine)
  2. osmoregulators
    - regulate solute and water concentration in blood, maintaining constant w.p. in blood
40
Q

what happens if kidney fails?

A
  • if one fails, you can still lead a normal life
  • if both fails: death
    common causes:
  • alcohol abuse
  • severe accidents that physically damage kidney
  • complications from undergoing major surgery
    treatment:
  • transplant
  • dialysis (2-3 times a day. 3-5hr each)
41
Q

how does a dialysis machine work?

A
  1. blood is drawn from the vein in the patient’s arm is allowed to be pumped through tubing in the machine
  2. walls of tubing is partially permeable and tubing is long, narrow coiled to increase surface area to volume ratio for faster removal of metabolic waste products via diffusion
  3. dialysis fluid contains same concentration of essential substances such as glucose and AA to ensure that these substances do not diffuse back into dialysis fluid. If the blood lacks these substances, they can diffuse into the blood
  4. there is no urea in dialysis fluid to set up a concentration gradient so urea will diffuse out of the blood into dialysis fluid as there is a higher concentration of urea in the blood than in the fluid. Large molecules like proteins and blood cells remain in tubine
  5. dialysis fluid flows in opposite direction as compared to blood to maintain costant concentration gradient for faster removal of metabolic waste products via diffusion
  6. blood is returned to the body through the ven after it is filtered

Secondary 3 Biology (13 decks)

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