Chapter 7 - Exchange surfaces and breathing

Question 1

Single Celled Organisms

Answer 1

➜ can diffuse directly into or out the cell due to small distance
➜ low metabolism due to low activity
➜ high SA : V ratio

Question 2

Multicellular Organisms

Answer 2

➜ diffusion across outer membrane is too slow
➜ large diffusion distance between some body cells and outer environment
➜ low SA : V ratio
➜ high metabolic rate due to high activity so use up oxygen/glucose faster

Question 3

Need for specialised system for gas exchange

Answer 3

➜ supply of oxygen - organisms require ATP to carry out biochemical processes
➜ removed of CO2 - toxic waste product, if let to accumulate in cells/tissue it can alter pH

Question 4

Large Surface Area

Answer 4

➜ high SA : V ratio
➜ root hair cells have a root hair that increases surface area
➜ therefore, rate of water uptake by osmosis is greater

Question 5

Thin Layers

Answer 5

➜ diffusion distance is short
➜ exchange of O2 and CO2 happens in alveoli and capillaries in lungs
➜ this is done by simple diffusion
➜ air in alveoli = high conc of O2 and oxygen diffuses from alveoli to capillaries
➜ blood in capillaries = low conc of O2 but high conc of CO2
➜ CO2 diffuses into alveoli and exhaled

Question 6

Good Blood Supply

Answer 6

➜ maintains a steep conc gradient so faster diffusion

Question 7

Ventilation

Answer 7

➜ maintain conc gradient

Question 8

Alveoli

Answer 8

➜ large number of alveoli - increases surface area
➜ wall of alveoli is single layer thick - elastic fibres in extracellular matrix = small diffusion distance
➜ always a higher concentration of oxygen in the alveoli than in the blood CONC GRAD
➜ O2 diffuses out of the alveolar space into blood and CO2 diffuses in opposite direction
➜ capillary narrow = squash red blood cells = closer to alveoli
➜ good blood supply so constant flow of O2 so maintains conc grad
➜ watery fluid lines alveoli, facilitating the diffusion of gases

Question 9

Ciliated epithelium

Answer 9

➜ trachea, bronchi
➜ each cell has small projections of cilia which sweep mucus

Question 10

Squamous epithelium

Answer 10

➜ alveoli
➜ forms structure of alveolar wall so it is very thin and permeable for easy diffusion of gases

Question 11

Trachea

Answer 11

➜ main airway leading from back of mouth to the lungs
➜ C shaped rings of cartilage to keep air channel open all the time
➜ C shaped to prevent any friction from rubbing with oesophagus
➜ substantial amount of mucus

Question 12

Bronchi

Answer 12

➜ similar to trachea but thinner walls and small diameter
➜ cartilage rings = full circles

Question 13

Bronchioles

Answer 13

➜ narrow self-supporting tubes with thin walls
➜ each bronchiole varies in size but get smaller as they get closer to the alveoli
➜ elastic fibres and smooth muscle that adjust size of airway
➜ smallest bronchiole = no smooth muscle but has elastic fibres

Question 14

Goblet Cells

Answer 14

➜ line the airways and secrete mucus
➜ mucus is swept along by cilia

➜ mucus traps microorganisms and prevents from reaching alveoli

Question 15

Cilia

Answer 15

➜ surface of cells lining airways
➜ cilia beat the mucus
➜ moves mucus up and away from alveoli to throat –> then swallowed
➜ prevents lung infections

Question 16

Elastic fibres

Answer 16

➜ walls of trachea, bronchi, bronchioles, alveoli
➜ Help process of breathing
➜ Breathing in = lungs inflate and elastic fibres are stretched
➜ Fibres recoil to help push out air when exhaling

Question 17

Smooth Muscle

Answer 17

➜ walls of trachea, bronchi, bronchioles
➜ allows diameter to be controlled
- more air needed = dilates
- less air needed = constricting
➜ this means less resistance to airflow and air can move in and out of lungs more easily

Question 18

Rings of Cartilage

Answer 18

➜ walls of trachea and bronchi
➜ provide support
➜ strong but flexible
➜ prevents trachea and bronchi from collapsing when you breathe in and pressure drops

Question 19

Inspiration

(active process)

Answer 19

➜ The external intercostal muscles and diaphragm contracts
➜ This causes ribs to move up and out, the diaphragm flattens
➜ This increases volume of thorax (lung cavity)
➜ Lung pressure of chest cavity drops to below atmospheric pressure
➜ Air flows into lungs from a high pressure outside body

Question 20

Expiration

(passive process)

Answer 20

➜ The external intercostal muscles and diaphragm relaxes
➜ This causes ribs to move down and in, the diaphragm becomes curved again (OG pos)
➜ This decreases volume of thorax (lung cavity)
➜ Lung pressure of chest cavity increases to above atmospheric pressure
➜ Air is forced out of the lungs

Question 21

Tidal Volume

Answer 21

➜ the volume of air in each breath

Question 22

Vital Capacity

Answer 22

➜ the max volume of air that can be breathed in or out

Question 23

Residual Volume

Answer 23

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

Question 24

Inspiratory reserve Volume

Answer 24

➜ max vol of air you can breathe in, over a normal inhalation

Question 25

Expiratory reserve Volume

Answer 25

➜ extra amount of air you can force out of your lungs over and above the normal tidal volume of air you breathe out

Question 26

Ventilation rate = tidal vol x breathing rate (per min)

Answer 26

total vol of air inhaled in one min

Question 27

Spirometer

Answer 27

➜ chamber filled with O2 floats on H20
➜ wear nose clip to ensure gas exhaled goes back into tank
➜ breathe in, chamber ↓ , breathe out, chamber ↑
➜ movements of chamber recorded on datalogger/kymograph
➜ soda lime absorbs CO2 produced
➜ total vol in tank decreases over time as O2 is used up

Question 28

Single circulatory systems

Answer 28

➜ Fish
➜ Deoxy blood pumped from heart to gills (exchange site)
➜ oxy blood flows from gills to rest of body
➜ blood returns to heart
➜ heart = one atrium and one ventricle

➜ blood only passes through the heart once for each complete circuit of the body

Question 29

Double circulatory systems

Answer 29

➜ mammals
➜ blood passes heart twice
➜ mammalian heart has a wall (septum) dividing the heart
left side = oxy
right side = deoxy
➜ required to maintain steep conc grad for efficient gas exchange as pressure changes while in capillary (blood has to pass through 2 capillary networks before returning to heart)

➜ blood passes through the heart twice for each complete circuit of the body

Question 30

Closed circulatory systems

Answer 30

➜ Fish and Mammals
➜ blood is pumped within a network of blood vessels

➜ blood is enclosed inside the blood vessels

Question 31

Open circulatory systems

Answer 31

➜ Invertebrates - insects
➜ blood is not contained in blood vessels and is pumped directly into body cavities

➜ blood isn’t enclosed in blood vessels and it can flow free through body cavity

Question 32

Countercurrent flow

Answer 32

➜ Blood flows along the gill arch and out along the filaments to the secondary lamellae.
➜ The blood then flows through capillaries in the opposite direction to the flow of water over lamellae
➜ absorbs the max amount of oxygen from water

Question 33

Gas Exchange in Bony Fish

Answer 33

➜ use gills
➜ each gill has2 rows of filaments attached to a bony arch
➜ on surface of each filament there is lamellae = single layer of flattened cells that cover a vast network of capillaries
Filaments have large surface area and folded into secondary lamellae (gill plates)
➜ short diffusion distance - capillaries carry blood close to secondary lamellae
➜ countercurrent flow

Question 34

Ventilation in Bony Fish

Answer 34

➜ buccal cavity (mouth) floor moves down - vol increases and press decreases
➜ water drawn into buccal cavity
➜ buccal cavity closes
➜ buccal cavity is raised - chamber contracts and vol decreases and press increases
➜ water flows into gill cavity (now at low pres)
➜ as water enters, pressure builds up in gill cavity causing operculum to be forced open and water leaves fish
➜ operculum is pulled shut when the floor of the buccal cavity is lowered at the start of the next cycle

Question 35

Circulatory system in insects

Answer 35

➜ one main blood vessel = dorsal vessel
➜ tubular heart in the abdomen pumps haemolymph (blood in insects) into dorsal vessel
➜ dorsal vessel delivers the haemolymph into the haemocoel (body cavity)
➜ Haemolymph surrounds the organs and eventually re-enters the heart via one-way valves called ostia

Question 36

Gas Exchange in Insects

Answer 36

➜ open circulatory system = O2 not transported in blood
➜ rigid exoskeleton with waxy coating = impermeable to gases
➜ Air enters via spiracles (has valves) into tracheal system
➜ Air transported through tracheae which lead to tracheoles (rigid rings of cartilage that keep tracheae open)
➜ large number of tracheoles run between cells and into the muscle fibres
➜ tracheoles = open and filled with tracheal fluid - exchange happen between fluid and air in tracheoles, as well as through thin tracheole wall
➜ active tissue withdraw tracheal fluid into body fluid to increase surface area of tracheole wall

Question 37

Ventilation in Insects

Answer 37

➜ insect flies = muscles squeeze air sacs pushing air into tracheal system
➜ air moves into tracheae through pores on the insect (spiracles)
➜ O2 travels down conc grad towards cells
➜ CO2 moves down its own conc grad towards spiracles to be released into atm
➜ tracheae branch off into smaller tracheoles which have thin permeable walls and contain fluid which O2 dissolves into - then goes to body cells
➜ CO2 diffuses in opposite direction

Question 38

What happens if u take a fish out of water

Answer 38

• water is no longer separating the filaments and so they’ll stick together which decreases surface area so no exchange of gas can happen and fish die !