Exchange Surfaces and Breathing

Question 1

What are the two main reasons as to why single celled organisms can rely on diffusion alone?

Answer 1

Metabolic demands are low

Surface area to volume ratio is high

Question 2

What are the 4 key features of a good exchange surface?

Answer 2

Increased Surface Area
Thin Layers
Good Blood Supply
Ventilation to maintain diffusion gradient

Question 3

What are the benefits of an increased surface area? Give examples of places with this.

Answer 3

Provides are for exchange and overcomes the limitations of SA:V ratio
Eg. Root Hair Cells and Villi

Question 4

What are the benefits of thin layers? Give examples of places with this.

Answer 4

Distances substances have to diffuse is short, making process faster and more efficient
Eg. Alveoli and Villi

Question 5

What are the benefits of a good blood supply ? Give examples of places with this.

Answer 5

Steeper the concentration gradient, faster diffusion takes place.
Eg. Alveoli, Gills and Villi

Question 6

What are the benefits of good ventilation? Give examples of places with this.

Answer 6

For gases, helps maintain concentration gradients and make process more efficient
Eg. Alveoli and Gills

Question 7

What has the Mammalian Gaseous Exchange system had to evolve to do?

Answer 7

Complex systems that allow for efficient gaseous exchange but minimise water loss

Question 8

What are three key features of the nasal cavity and what do they do?

Answer 8

Large surface area with good blood supply- warms air to body temperature
Hairy lining- which secretes mucus to trap dust and bacteria protecting lungs from irritation
Moist surfaces- increase humidity preventing evaporation

Question 9

What is the trachea?

Answer 9

Main airway carrying clean warm, moist air from the nose down the chest

Question 10

What is the structure of the trachea?

Answer 10

Wide tube supported by incomplete rings of strong, flexible cartilage which stop the tube from collapsing

Question 11

Why are tracheal rings incomplete?

Answer 11

To allow food to easily move down the oesophagus because that is behind the trachea

Question 12

What is the trachea lined with?

Answer 12

Ciliated epithelium and goblet cells

Question 13

What is the role of goblet cells?

Answer 13

To secrete mucus onto the lining of the trachea, to trap dust and microorganisms that have escaped the nose lining.

Question 14

What prevents mucus entering the lungs? How?

Answer 14

Cilia beat mucus and microorganisms away from lungs, mostly into the throat where it is digested

Question 15

What is the effect of cigarette smoke on the trachea?

Answer 15

Stops cilia beating

Question 16

What are the bronchi?

Answer 16

Supporting rings of cartilage that are smaller than the trachea and branch into each lung

Question 17

What is the structure of bronchioles?

Answer 17

No cartilage rings

Smooth muscle

Question 18

How does smooth muscle link to role of bronchioles?

Answer 18

Smooth muscles contract- bronchioles constrict
Smooth muscle relaxes- bronchioles dilate
Affects how much oxygen reaches lungs

Question 19

Can gaseous exchange occur in bronchioles?

Answer 19

Yes, as the are lined with a layer of flattened epithelium

Question 20

What is the structure of alveoli?

Answer 20

Tiny air sacs made from thin, flattened epithelial cells

Contains some collagen and elastic fibres

Question 21

What is elastic recoil?

Answer 21

Elastic tissues stretching to allow alveoli to draw in maximum amount of air, then returning to resting size to help squeeze air out.

Question 22

How are alveoli adapted?

Answer 22

Large surface area
Thin layers- one epithelial cell thick cell walls
Good blood supply
Good ventilation - from breathing

Question 23

What is the role of ‘lung surfactant’?

Answer 23

Allows alveoli to remain inflated

Question 24

What causes ventilation to occur?

Answer 24

Pressure changes in the thorax

Question 25

What is the pleural cavity filled with? Why?

Answer 25

Thin layer of lubricating fluid so the membranes slide easily over each other

Question 26

Explain what happens during inspiration

Answer 26

Diaphragm contracts- flattening and lowering
External intercostal muscles contract
Ribs move upwards and outwards
Volume of thorax increase= pressure in thorax decreases
Lower than atmospheric pressure so air drawn in

Question 27

Explain what happens during passive expiration

Answer 27

Diaphragm relaxes into resting dome shape
External intercostal muscles relax
Ribs move downwards and inwards
Alveoli elastic fibres return to normal length
Decreased volume of thorax
Pressure inside greater than outside, air forced out

Question 28

What happens during forced expiration?

Answer 28

Requires energy
Internal intercostal muscles contract
Ribs pulled down hard and fast
Abdominal muscles contract forcing diaphragm up to increase pressure rapidly

Question 29

What does a peak flow meter measure?

Answer 29

The rate at which air can be expelled from the lungs

Question 30

What does a vitalograph measure?

Answer 30

Amount of air breathed out and how quickly (the forced expiratory volume in 1 second)

Question 31

What does a spirometer measure?

Answer 31

Different aspects of long volume or breathing patterns

Question 32

Define ‘tidal volume’

Answer 32

The volume of air that moves into and out of the lungs with each resting breath

Question 33

Define ‘vital capacity’

Answer 33

Volume of air that can be exhaled when the deepest possible intake of breath is followed by the longest possible exhalation

Question 34

Define ‘inspiratory reserve volume’

Answer 34

The maximum volume of air you can breath in over a normal exhalation

Question 35

Define ‘expiratory reserve volume’

Answer 35

The maximum volume of air you can force out of your lungs above your tidal volume of air you breathe out

Question 36

Define ‘residual volume’

Answer 36

The volume of air that is left in your lungs when you have exhaled as hard as possible

Question 37

Define ‘total lung capacity’

Answer 37

The sum of the vital capacity and residual volume

Question 38

What is the breathing rate?

Answer 38

The number of breaths taken per minute

Question 39

What is the ventilation rate?

Answer 39

The total volume of air inhaled in one minute

Question 40

Give the equation for ventilation rate

Answer 40

Ventilation Rate= breathing rate x tidal volume

Question 41

Explain how a spirometer works

Answer 41

Nose clip
Subject breaths in and out until oxygen is used up
Trace drawn on revolving drum
Cannister of soda lime removes carbon dioxide

Question 42

What are spiracles?

Answer 42

Small openings in the thorax of an insects body that allows for the movement in and out of oxygen and carbon dioxide

Question 43

How do insects minimise water loss during gaseous exchange?

Answer 43

Spiracle sphincters remain shut as much as possible

Question 44

What is the structure of trachea in an insect?

Answer 44

Tubes lined with chitin which keep them open if bent or pressed

Question 45

Can gaseous exchange occur in the trachea of an insect?

Answer 45

Very little because chitin is impermeable

Question 46

What is the structure of tracheoles?

Answer 46

Single, elongated cells which have no chitin lining which pass throughout the tissues of an insect

Question 47

How does oxygen move through an insect normally?

Answer 47

Through the trachea into the tracheoles where oxygen dissolves into the moisture on the cell walls and then diffuses into cells

Question 48

How is tracheal fluid adapted to help the insect?

Answer 48

Tracheal fluid normally limits the penetration of air
Lactic acid builds up when oxygen demands are high
This lowers water potential of tracheal fluid so water moves out via osmosis.
Exposes more surface area for gaseous exchange

Question 49

What are two alternative methods that insects have to gain more oxygen?

Answer 49

Mechanical ventilation of the tracheal system

Collapsible enlarged tracheae or air sacs

Question 50

What adaptations to gill lamellae have? What occurs there?

Answer 50

Main site of gaseous exchange in a fish

Rich blood supply and large surface area= efficient exchange

Question 51

What is the structure of gill filaments and how does this help gaseous exchange occur?

Answer 51

Large stacks of gill filaments-gill plates

Flow of water keeps them apart showing large surface area for gaseous exchange

Question 52

What is the role of a gill arch?

Answer 52

Supports structure of gills

Question 53

What is the operculum?

Answer 53

The flap that covers gills

Question 54

What is ram ventilation?

Answer 54

Relying on continual movement to ventilate the gills

Question 55

Explain process of ventilation in a bony fish

Answer 55

Floor of buccal cavity drops
Volume increases
Pressure decreases
Water enters
Mouth closes
Operculum squeezes inwards
Buccal cavity floor moves upwards
Volume decreases
Pressure increases
Water forced out over gills

Question 56

What are the 3 major adaptations for successful gaseous exchange in bony fish?

Answer 56

Large Surface Area
Adjacent gill filaments overlap increasing resistance so more time for exchange to occur
Counter current blood flow system-allows steep concentration gradient to be maintained

Question 57

Compare blood flow systems in cartilaginous and bony fish

Answer 57

Cartilaginous- parallel system, 50% oxygen extracted

Bony- counter current, 80% oxygen extracted