Gas Exchange

Question 1

RESPIRATORY SYSTEM IN MAMMALS

reasons for its necessity (3)

Answer 1

1. surface area to volume ratio too large for transport of O2 by diffusion alone
2. presence of protective outer surface prevents diffusion of gases, alternative respiratory surface needed
3. increased metabolic rate = more O2 needed

Question 2

conditions for effective diffusion (4)

Answer 2

1. large surface area
2. ventilation mechanism, to maintain conc. gradient
3. good blood supply to transport away O2 quickly and maintain concentration gradient
4. presence of a haem protein to increase O2-carrying capacity of the blood.

Question 3

size of gas exchange surface in humans

Answer 3

70-75 m2

Question 4

TRACHEA
features present (4)

Answer 4

1. cartilage
2. goblet cells
3. cilia
4. smooth muscle

Question 5

TRACHEA
function of cartilage

Answer 5

prevents the trachea from collapsing into itself, particularly when a large bolus of food passes through the oesophagus

Question 6

how is air entering the lungs warmed up?

Answer 6

from the heat of blood passing through the capillary system in the nose

Question 7

MUCUS
function (2)

Answer 7

moistens air and traps fine dust particles

Question 8

what type of air is needed to protect the alveolar lining?

Answer 8

warm, moist and as free of dust and foreign bodies as possible

Question 9

CILIA

function

Answer 9

back-and-forth movement beats mucus stream into the buccal cavity, where it is swallowed

Question 10

TRACHEA

arrangement of cartilage

Answer 10

regular (incomplete) C-shaped rings

Question 11

BRONCHI + LARGE BRONCHIOLES

arrangement of cartilage

Answer 11

irregular tiny plates or rings

Question 12

BRONCHI + LARGE BRONCHIOLES

role of smooth muscle & cartilage

Answer 12

prevent collapse (eg. from sudden reductions of pressure that occur with a powerful inhale of air). smooth muscles also regulate the size of the smaller airways by contracting & relaxing

Question 13

SMALLER BRONCHIOLES

structure

Answer 13

no cartilage, very few goblet cells. smooth muscle is the major component of their walls. become progressively narrower as they branch.

Question 14

PLEURAL FLUID

source

Answer 14

made from blood plasma, secreted by internal surfaces of the thorax

Question 15

PLEURAL FLUID

function

Answer 15

provides the surface tension that holds lungs to ribcage and protects the lungs from friction during breathing movements

Question 16

water loss from the lungs

Answer 16

10-15% of total loss (3L)

Question 17

MUCUS

structure of goblet

Answer 17

upper part swollen with mucin droplets. rest of the cell contains a Golgi body, some rER, mitochondria and a nucleus. the lower part of the cell is very thin, so the cell looks like a goblet.

Question 18

role of macrophages in defending lungs

Answer 18

engulf bacteria and fine dust particles.

Question 19

STRUCTURE OF ALVEOLI

role of elastic muscle fibres

Answer 19

stretch with alveolar walls during inspiration and recoil during expiration. the recoil restores alveoli to regular shape and aids expulsion of air.

Question 20

STRUCTURE OF ALVEOLI

thickness of wall

Answer 20

one cell thick (formed by squamous epithelium)

Question 21

STRUCTURE OF ALVEOLI
function of thin walls

Answer 21

v. low distance (2-4 micrometers) for diffusion of gases = rapid gas exchange

Question 22

name of bronchiole connecting alveoli to rest of lungs

Answer 22

terminal bronchiole

Question 23

% saturation of O2 in blood coming from pulmonary artery

Answer 23

~70%

Question 24

partial pressure of O2 in blood coming from pulmonary artery

Answer 24

5.3 kPa

Question 25

partial pressure of O2 in alveolar air

Answer 25

13.9 kPa

Question 26

partial pressure of CO2 in alveolar air

Answer 26

5.3 kPa

Question 27

partial pressure of CO2 in blood coming from pulmonary artery

Answer 27

6.0 kPa

Question 28

% saturation of O2 in blood going to pulmonary vein

Answer 28

~95%

Question 29

% of O2 in expired air

Answer 29

16% (4% less than inspired air)

Question 30

% of CO2 in inspired air

Answer 30

0.04%

Question 31

% of CO2 in expired air

Answer 31

4%