Lecture 11 - Microscopic structure of gas exchange Flashcards

1
Q

what is the smallest unit in which gas exchange occurs?

A

alveoli

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

where are alveoli scattered?

A

within the walls of respiratory bronchi

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

where are alveoli continuous? what do they lead to?

A

in walls of alveolar ducts which lead to terminal alveolar

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what are the two cell types of the alveoli epithelial cells

A

type 1 alveolar epithelial cells

type 2 alveolar epithelial cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

describe the shape and function of type 1 alveolar cells, can they divide?

A
  • very flattened cells, sit on basement membrane
  • terminally differentiated (cannot divide)
  • allow gas diffusion across cytoplasm
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

describe the shape and function of type 2 alveolar cells

A
  • cuboidal
  • cytoplasmic granules contain surfactant (surface tension)
  • divide to replace type I and II cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

other than type I and II epithelial cells, what else can be found within the alveoli?

A

macrophages

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

how are alveolar seperated? what do they contain

A

by inter alveolar septa: contain fibroblasts, mast cells and macrophages

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what are alveolar pores?

A

holes in septa between adjacent alveoli, allow passage of air between alveoli

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

blood - air barrier

A

oxygen must diffuse across;

  • alveolar fluid
  • alveolar epithelium
  • basement membrane of alveolar epithelium
  • basement membrane of capillary cell
  • capillary endothelial cell
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

how thick is the blood - air barrier

A

0.2 - 2 micron thick

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what are pulmonary macrophages, where are they present?

A

present in 3 locations
1. intravascular: associated with endothelium
2. interstitial
3. alveolar: function to clear alveolar surface - removed via trachea
can proliferate locally

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what does the interlobar septa contain?

A

collagen and elastic fibres

blood vessels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what is partial pressure?

A

pressure exerted by a given gas in a mixture of gases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

alveolar air

A
water vapour added to air in inspiration --> changes in partial pressure
o2 = 146
CO2 = 0.27
N2 = 556
H20 = 47
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

how much alveolar air is replaced with each normal breath?

A

around 15% total alveolar air replaced with each breathe, air enters alveolus, diluted by stale air remaining

17
Q

how does partial pressures of gasses change in liquid?

A

determined by concentration of gas dissolved in fluid
O2 bound to Hb, does not contribute to PO2
CO2 dissolved in blood equilibrates to H+ and HCO3-

18
Q

partial pressure gradients

A

gases diffuse from area of high partial pressure to area of low partial pressure, passive diffusion down

19
Q

how is the rate of diffusion through tissues (DR) determined?

A
DR = PD x A x DC / T 
PD = partial pressure gradient
A = surface area available 
DC = diffusion coefficient
T = thickness of barrier
20
Q

describe the diffusion co-efficient (DC)

A

each gas has co-efficient
CO2 more soluble than O2 in water, therefore it diffuses more quickly
factors limiting diffusion may result in hypoxia without hypercapnia because CO2 diffuses out so fast

21
Q

how is surface area available increased or decreased?

A

increased during exercise

decreased in diseased state

22
Q

how is barrier thickness increased?

A

increased in disease - pulm oedema, pulmonary fibrosis, pneumonia

23
Q

what is a gill

A

water contains less O2 than air = makes use of gills

gills = delicate evagination of tissue protruding into surrounding water, consist of this epidermis highly perfused

24
Q

how does a fish breath underwater?

A
  • take water into mouth while operculum is closed,

mouth is then shut and operculum opened, forcing water over gills and out through operculum

25
Q

is flowthrough in a fish uni- or bi- directional

A

uni-directional