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Anatomy And Physiology 2 > Gas Exchange > Flashcards

Gas Exchange Flashcards

1
Q

What are alveoli

A

Air filled pockets in the lungs where all gas exchange takes place

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2
Q

What are the types of cell of the alveoli

A

Pneumocytes type 1
Pneumocytes type 2
Macrophages

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3
Q

What are types one Pneumocytes and what do they do

A

Simple squamous

Thin cells, wall of alveoli

Short gas exchange distance

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4
Q

What are type two Pneumocytes and what do they do

A

More specialised

Produce surfactant

Larger cells

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5
Q

What is a macrophage and what does it do

A

Digest things that shouldn’t be there

Remove dust and foreign objects

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6
Q

What is the role of surfactant

A

Reduce surface tension to stop the alveoli from collapse h

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7
Q

Explain elasticity of the alveoli

A

Has a dense network of capillaries, is surrounded by elastic fibres

Fibres recoil during exhalation, reduce size of alveoli to push air out

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8
Q

Why is gas exchange efficient at alveoli

A

Walls less that one micro meter thick

Sa 35 x surface of the body
(Put together)

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9
Q

Explain alveolar epithelium

A

Simple squamous

Consists of thin delicate type 1 Pneumocytes

Patrolled by macrophages (dust cells)

Contain type 2 pneumocytes that produce surfactant

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10
Q

What is Henry’s law

A

When gas under pressure comes into contact with liquid, gas dissolves until liquid equilibrium is reached

At a given temperature:
Amount of gas in a solution is proportional to Pp of that gas

E.g the pp of oxygen at sea level is 20%

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11
Q

What are the factors that lead to efficient gas exchange

A
  1. Substantial differences in pp of O2 across the respiratory membrane
  2. Distances involved in gas exchange are short
  3. O2 and Co2 are lipid soluble
  4. SA is large
  5. Blood flow and air flow are coordinated
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12
Q

What does diffusion happen over

A

Concentration gradient, determined by pp

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13
Q

What is the pulmonary circuit

A

Heart and lungs,

Carries deoxygenated blood from the heart to the lungs to be oxygenated

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14
Q

What is the systemic circuit

A

Carries oxygenated blood from the left ventricle

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15
Q

How is gas transported

A

Plasma

Red blood cells - hb
- transport gas from peripheral tissues
- remove gas from plasma, allowing them to diffuse into the blood

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16
Q

How does oxygen bind to haemoglobin

A

Hemes - binding sites

Oxyhaemoglobin - saturated with oxygen

Deoxyhaemoglobin - without oxygen bound to it

Carbominohaemoglobin - carrying co2

17
Q

Why is carbon monoxide dangerous

A

Haemoglobin has a higher affinity for it, stop oxygen binding

18
Q

What factors effect o2 release

A
  • ppo2
  • blood ph
    -temperature
  • bpg levels, increase with increase
19
Q

Why is the oxyhaemoglobin saturation curve a curve not a line

A

Shape of hb molecule changes slightly every time it binds to an oxygen molecule

Each o2 binding makes more binding easier

20
Q

Explain dissociation at equilibrium

A

Oxygen molecules bind at the same rate other oxygen molecules are released

21
Q

What is normal saturation at rest

A

96%

22
Q

How does temp effect affinity

A

Temp increase = hb releases more O2, less affinity

Decrease, release less, more affinity

23
Q

What is the bohr effect

A

Result of ph on saturation curve

Caused by co2 production
= carbonic acid

Lower ph = lower affinity, more released- shift Right

Higher ph = higher affinity, less released, shift Left

24
Q

How is co2 transported in the blood

A

Generated by aerobic metabolism

  • dissolve in plasma 7%
  • red blood cells 93%,
  • 23 % of this bind to hb = cmhb
  • converted to carbonic acid 70%
25
Q

What is meant by local control of respiration

A

At the tissues

Increased activity of peripheral tissue = less o2 more co2 pp

Changes in gas exchange

Increased blood flow

26
Q

Explain neural control of respiration

A

Respiratory centres at brain-
Increased demand = increased Q and resp rates

Involuntary:
Reg resp muscle activity
Freq and depth

Voluntary:
- reflects activity in cerebral y
- effect output of med ob, pons, motor neurons

27
Q

Where are respiratory centres

A

Rcc in medulla oblongata

Pons has some control

28
Q

Explain control of respiration in the pons

A

Pons and medulla oblongata are linked

  • paired nuclei that adjust output of respiratory rhythmicity centres

Apneustic centres:
- provides continuous stimulation DRG, increasing intensity of inhalation - inhibited during exhalation

Pneumotaxic centres:
- inhibit A centre and promote exhalation

29
Q

Where are the different respiratory areas in the brain

A

Higher centres:

  • hypothalamus, Linux system and cerebral cortex alter activity if pneumotaxic areas

A and p centre in pons

Medulla oblongata, DRG VRG

30
Q

What are the respiratory centre of the medulla oblongata

A

Dorsal respiratory group (top)
- inspiratory centre
- quiet and forceful

  • intercostalmusckes and diaphragm

Ventral respiratory group
- inspiratory and expiratory centre
- only in forced breathing
- accessory respiratory muscles

31
Q

Explain the cycle of the respiratory groups

A
  1. DRG and inspiratory centre of VRG active, expiratory centre of VRG inhibited
  2. Muscles of inhalation contract, and opposing muscles relax. Inhalation occurs
  3. DRG and inspiratory centres of VRG inhibited. Expiratory centre of VRG active
  4. Muscles of inhalation relax and muscle of exhalation contact. Expiration
32
Q

What are the respiratory reflexes

A
  1. Chemoreceptors - sensitive to pp, ph, cerebrospinal fluid
  2. Baroreceptors
  3. Stretch receptors, sensitive to changes in lung volume
  4. Irritating physical or chemical stimuli in resp tract
  5. Temp ect
33
Q

What are the mechanoreceptors involved in respiratory regulation

A

Baroreceptors

Stretch receptors - changes in lung volume

34
Q

What is the hering-breurer reflex

A

2 mechanoreceptors reflexes involved in forced breathing

  • inflation reflex
    Prevents over expansion of lungs
    As lung volume increases DRG inhibited, VRG stimulation (expiratory portion)
  • deflation reflex
    Inhibits respiratory centres
    Stimulated inspiration centre during lung deflation
35
Q

Explain the chemoreceptor reflexes involved in respiratory control

A

Influenced by chemoreceptor input from:

Cranial nerves

Central chemoreceptors that monitor cerebrospinal fluid

(Csf contains oxygen so can tell oxygen concentrations, decide if need more respiration)

  • in brain stem
36
Q

What factors stimulate chemoreceptors

A
  • drop on PO2 to 40mmHg = increase rate 50-70%
  • 10% increase PCo2 = increase rate 100%
  • chemoreceptor stimulation decreased sensitivity which chronic stimulation
  • increased lactic acid, ph

Anatomy And Physiology 2 (8 decks)

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