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Sec 3 Pure Bio > Excretion in humans > Flashcards

Excretion in humans Flashcards

1
Q

Catabolic reactions

A
  • chemical reactions in which complex substances are broken down into simpler ones
  • e.g. glucose (complex substance) oxidised/ broken down into carbon dioxide and water (simpler substances) with release of energy during cellular respiration
  • e.g. proteins and amino acids are deaminated in the liver to form urea
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2
Q

Anabolic reactions

A
  • chemical reactions in which simple substances are built up into complex ones
  • e.g formation of new proteins from amino acids
  • e.g. conversion of glucose into glycogen in liver and muscles
  • e.g. photosynthesis
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3
Q

Metabolism

A
  • catabolism + anabolism , the sum of all chemical reactions in body
  • metabolic reactions produce waste products, can be harmful, toxic if accumulated
  • removed thru excretion
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4
Q

Excretion

A
  • the process by which metabolic waste products and toxic substances are removed from the body of an organism
  • excretory products refer to metabolic waste products and toxic substances
  • unicellular organisms: excrete waste products via diffusion into surrounding environment
  • multicellular organisms: esp animals with impermeable skin need excretory organs
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5
Q

Excretory products of lungs

A
  1. carbon dioxide
    - excreted as gas in expired air
  2. excess water
    - water vapour in expired air
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6
Q

Excretory products of kidneys

A
  1. excess mineral salts, nitrogenous waste products
    - e.g. mainly urea (indirectly from deamination of protein), uric acid (from breakdown of nucleic acids), creatinine (from breakdown of muscle proteins)
    - excreted as a constituent of urine
  2. excess water
    - excreted as main constituent of urine
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7
Q

Excretory products of skin

A
  1. excess mineral salts and nitrogenous waste products
    - mainly urea (indirectly from deamination of protein)
    - uric acid (from breakdown of nucleic acids)
    - creatinine (from breakdown of muscle proteins)
    - excreted as constituents of sweat, but only in small quantities for nitrogenous waste products
  2. excess water
    - excreted as a main constituent of sweat
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8
Q

Excretory products of liver

A
  • bile pigments (from breakdown of haemoglobin)

- excreted as constituent of faeces via intestines

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9
Q

Human Urinary System: Hilus

A
  • the depression at the centre of the concave surface

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

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10
Q

Human Urinary System: Ureter

A

-narrow tube that connects the kidney to urinary bladder that urine passes thru

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11
Q

Human Urinary System: Urinary bladder

A
  • an elastic muscular bag located in front of the rectum

- stores urine

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12
Q

Human Urinary System: Urethra

A

-the duct thru which urine passes from the bladder to outside of the body

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13
Q

Human Urinary System: Sphincter muscle

A
  • located at bottom of bladder
  • used to control urination
  • when bladder is full, sensory neurones send nerve impulses to the brain
  • to urinate, brain sends nerve impulses to sphincter muscle to relax, urine can flow into urethra and out of body
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14
Q

Structure of kidney: Cortex

A
  • outer dark red region

- covered and protected by fibrous capsule

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15
Q

Structure of kidney: Medulla

A
  • inner pale region

- contains renal pyramids

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16
Q

Structure of kidney: Renal pyramids

A
  • conical structures located in the medulla, human kidney contains 12-16 renal pyramids
  • radial stripes indicate numerous kidney tubules (nephrons)
  • urine is formed in these nephrons
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17
Q

Structure of kidney: Renal Pelvis

A

-enlarged portion of the ureter inside the kidney

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18
Q

Structure of nephron: Bowman’s capsule

A
  • cup-like structure

- contains glomerulus

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19
Q

Structure of nephron: Proximal (first) convoluted tubule

A

-short, coiled tubule, straightens out as it passes into the medulla

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20
Q

Structure of nephron: Loop of Henle

A
  • in medulla, tubule extends into renal pyramid, makes u-turn back into cortex
  • u-shaped portion is known as loop of Henle
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21
Q

Structure of nephron: Distal convoluted tubule

A

-when tubule enters cortex again, becomes convoluted

22
Q

Structure of nephron: Collecting duct

A
  • tubule then opens into a collecting duct
  • runs straight thru the medulla
  • eventually opens into the renal pelvis
23
Q

Flow of blood in nephrons (kidney tubules)

A
  1. blood enters kidney via renal artery, branches out into arterioles
  2. arterioles further branches into a mass of blood capillaries (glomerulus) in Bowman’s capsule
  3. Bowman’s capsule + glomerulus = renal corpuscle
  4. blood leaving the glomerulus enters blood capillaries surrounding nephron
  5. blood capillaries unite to form venules,
  6. venules join to form a branch of the renal vein
24
Q

Urine formation: Ultrafiltration

A
  • blood flow from renal artery to glomeruli in renal corpuscles
    1. caused by hydrostatic blood pressure
  • diameter diff between afferent and efferent arteriole
  • creates high blood pressure, main force required for filtration process
    2. Basement membrane
  • partially permeable membrane, wraps arnd glomerular blood capillaries like a fine filter
  • small pores, only allow water, glucose, amino acids, mineral salts and nitrogenous waste products to flow thru), called filtrate
  • retains rbc and plasma proteins
25
Q

Urine formation: Selective reabsorption

A
  • normal adult, 120cm3 of filtrate formed in kidney every min
  • if this amt of filtrate were allowed to pass out as urine, body lose too much water and other useful substances, become dehydrated
  • thus as filtrate passes thru tubule, useful substances reabsorbed into bloodstream
26
Q

Selective reabsorption: Proximal convoluted tubule

A
  • most mineral salts (sodium ions), all glucose and amino acids absorbed thru walls of tubule into surrounding blood capillaries
  • these solutes reabsorbed via diffusion and active transport
  • reabsorption highly selective, readily absorb substances required by body
  • most water reabsorbed via osmosis here
27
Q

Selective reabsorption: Loop of Henle

A

-some water reabsorbed

28
Q

Selective reabsorption: Distal convoluted tubule

A

-some water and mineral salts reabosrbed

29
Q

Selective reabsorption: Collecting duct

A
  • some water reabsorbed
  • excess water, salts and metabolic wastes such as urea, uric acid and creatinine pass out of collecting duct into renal pelvis as a mixture called urine
30
Q

Composition of urine

A 
Water: 96.0g 
Mineral salts (mainly sodium chloride): 1.8g 
Urea: 2.0g 
Other nitrogenous substances: 0.2g 
Total: 100.0g
31
Q

Protein rich diet (composition of urine)

A
  • more urea present in urine

- urea is formed when excess amino acids are deaminated in liver

32
Q

Consuming more water-rich food/more liquids (composition of urine)

A
  • increases water potential of blood
  • vol of urine excreted is larger
  • also happens in cold weather (sweat secretion is reduced)
33
Q

High intake of salty foods (composition of urine)

A

-excess salts excreted in urine

34
Q

Diabetes mellitus

A
  • excrete large amt of glucose in urine
  • diabetic unable to store up excess glucose as glycogen, high glucose conc in blood
  • glucose filtered out of glomerulus to form part of glomerular filtrate
  • nephrons unable to absorb glucose fast enough
35
Q

Osmoregulation

A

-the control of water and solute concentrations (levels) in blood to maintain a constant water potential in body

36
Q

Why water potential of blood in body needs to be kept relatively constant?

A
  • drastic changes can result in serious problems
  • blood plasma too diluted, more water enter blood cells via osmosis, swell, might burst
  • blood plasma too concentrated, more water leaves blood cells via osmosis, dehydrated, shrink, unable to carry out metabolic functions properly, may be fatal
37
Q

Water potential of blood

A

-depends on amt of water and mineral salts in blood plasma

38
Q

Antidiuretic hormone (ADH)

A
  • controls amt of water in blood plasma
  • ADH produced by region of brain called hypothalamus
  • released by pituitary gland, increases water reabsorption at nephrons
39
Q

How kidneys help to regulate wp in blood

A

-kidneys are called osmoregulators, help to regualte water and solute conc in blood

40
Q

Loss of water/Large in intake of water (osmoregulation in kidneys)

A
  • e.g. sweating / drinking
    1. wp of blood decreases/increases, stimulates hypothalamus in brain
    2. pituitary gland releases more/less ADH into bloodstream
    3. cells in walls of collecting ducts become more/less permeable to water, more/less water reabsorbed from collecting ducts into blood capillaries
    4. smaller/larger vol of urine produced
    5. urine produced is more/less concentrated
    6. water potential of blood returns to normal
41
Q

How is water potential of blood related to blood pressure?

A
  • amt of water reabsorbed affects blood vol
  • blood vol rise, blood pressure rise
  • large increase in blood pressure can cause blood vessels in brain to burst, lead to stroke
  • drug called diruretics reduce production ADH, less water reabsorbed, large vol of dilute urine, wp in blood decreases, bp decreases
42
Q

Why are kidneys impt?

A
  1. excretory organs
    - excrete metabolic waste products e.g. urea, excess water, mineral salts (in form of urine)
  2. osmoregulators
    - regualte water and solutle conc in blood so wp is constant in blood
43
Q

Causes of kidney failure

A
  • high bp
  • diabetes
  • alcohol abuse (constant heavy drinking)
  • severe accidents that physically damage kidneys
  • complications from undergoing major surgery
44
Q

Dialysis

A
  • if no kidney donors
  • dialysis machine mimics functions of kidney
  • helps to clean patient’s blood from metabolic waste products and toxins
  • patient need to undergo dialysis treatment 2-3 times a week, 3-5 hrs per session
45
Q

How does a dialysis machine work?

A
  1. Blood is drawn from the vein in the patient’s arm, allowed to be pumped thru the tubing in the dialysis machine
  2. tubing is bathed in a specially controlled dialysis fluid, its walls are partially permeable
  3. small molecules such as urea and other metabolic waste products diffuse out of tubing and into dialysis fluid (blood cells and platelets are retained)
  4. filtered blood is then returned to a vein in the patient’s arm
46
Q

Features of a dialysis machine

A
  1. Dialysis fluid contains same conc of essential substances as healthy blood
  2. Dialysis fluid does not contain metabolic waste products
  3. Tubing in machine is narrow, long and coiled
  4. Direction of blood flow is opposite to the flow of dialysis fluid
47
Q

Feature 1: Dialysis fluid contains same conc of essential substances as healthy blood

A
  • ensures essential substances (e.g. glucose, amino acids, mineral salts) dont diffuse out of blood and into the dialysis fluid
  • if patient’s blood lacks these essential substances, these substances will diffuse from the dialysis fluid and into the blood
48
Q

Feature 2: Dialysis fluid does not contain metabolic waste products

A
  • sets up conc gradient that allow waste products such as urea, uric acid, creatinine and excess water and mineral salts to diffuse out of tubing and into dialysis fluid
  • waste products removed frm blood
  • maintains correct solute composition and wp of blood
49
Q

Feature 3: Tubing in machine is narrow, long and coiled

A
  • increases sa:v ratio

- helps to speed up rate of exchange of substances between patient’s blood and dialysis fluid

50
Q

Feature 4: Direction of blood flow is opposite to the flow of dialysis fluid

A

-maintains conc gradient for removal of waste products

Sec 3 Pure Bio (16 decks)

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