Exchange Surfaces And Breathing: Biology A (Ocr As/a Level)

Front 1

Alveoli structure

Back 1

-100-300µm

-Small, air-filled sacks

-Exchange takes place at walls

-Surrounded by capillaries

-Thin endothelium

Front 2

Adaptions to reduce diffusion distance (alveoli)

Back 2

-Alveolus wall = 1 cell thick

-Capillary wall = 1 cell thick

-Both walls = squamous cells

-Capillaries = close contact with the alveolus walls

-Capillaries are narrow so that the red blood cells (erythrocytes) are squeezed against the capillary wall, making them closer to the air in the alveoli and reducing the rate at which they flow past in the blood.

-Total barrier to diffusion is only 2 flattened cells thick and is less than 1µm thick.

Front 3

A thin layer of moisture lines the alveoli. The moisture passes through the cell membranes from the cytoplasm of the alveolus cells. As we breathe out, it evaporates and is lost. How does alveolus not collapse (from the cohesive forces between the water molecules lining the air sac)?

Back 3

The lungs must produce a product called a surfactant to reduce the cohesive forces between the water molecules.

Front 4

How does the diaphragm and intercostal muscles help with the exchange of gases?

-Briefly-

Back 4

maintain a concentration gradient

Front 5

What does the ciliated epithelial do and goblet cells do?

-Briefly-

Back 5

remove dust, bacteria, pollen and spores

Front 6

What does cartilage do?

-Briefly-

Back 6

Holds airways open (during inhalation)

Front 7

What does smooth muscles do?

-briefly-

Back 7

Control and constrict the diameter of the airway

Front 8

What does the elastic fibres do?

-briefly-

Back 8

recoil, aiding ventilation by helping to expel air

Front 9

Gas exhange/breathing: macrophages and neutrophils do?

-briefly-

Back 9

engulf and destroy pathogens

Front 10

What does haemoglobin (Hb) do?

-briefly-

Back 10

They are in red blood cells; they carry oxygen and have a high affinity for oxygen.

Front 11

What is the importance of ventilation?

Back 11

increases concentration of oxygen in the alveoli

= the concentration of oxygen is higher than that in the blood

decreases concentration of carbon dioxide

=the concentration of CO2 is lower than that in the blood

higher concentration gradient - more efficient

Front 12

Trachea and Bronchi:

What requirements must the airways reach to be effective?

Back 12

Larger airways -> large enough -> allow sufficient air flow w/out obstruction.

Divide into smaller airways -> deliver air to all the alveoli.

Strong enough -> prevent collapsing when the air pressure inside is low (during inhalation)

Flexible -> allow movement, stretching and recoiling

Front 13

Structure of cartilage in trachea

Back 13

the cartilage bands are incomplete (C-shaped)

-allowing food to pass down the oesophagus (which runs behind the trachea)

Front 14

1) What are goblet cells?

2) What is ciliated epithelium?

Back 14

1) cells that secrete mucus

2) a layer of cells that have mnay hair-like extensions called cilia.

Front 15

What is smooth muscle?

Back 15

Involuntary muscle that contracts without the need for conscious thought.

Front 16

Compare the trachea and bronchi

Back 16

the trachea and bronchi have a similar structure:

*the bronchi are narrower than the trachea.

*Both walls' consist of cartilage, these are in the form of C-rings in trachea, less regular in bronchi

Front 17

Compare bronchioles to bronchi

Back 17

-bronchioles are much narrower than bronchi

-smaller bronchioles do not have any cartilage

-bronchioles end in clusters of alveoli

Front 18

What are bronchioles mostly comprised of?

Back 18

Elastic fibres and smooth muscle

Front 19

What are elastic fibres?

Back 19

protein fibres that can deform and then recoil to their original size

Front 20

Explain the function of Smooth muscles contracting.

Back 20

-can involuntarily contract

-constrict airways

-makes lumen of airway narrower (constricts the lumen)

-restricts the flow of air to/from alveoli

-important if there's harmful substances in the air

e.g. can occur as a result of allergic reaction

Front 21

What part do elastic fibres play in the functioning of smooth muscles?

Back 21

Smooth muscles cannot reverse effects of contracting on its own

muscles contracts -> deforms the elastic fibres

muscles relax -> elastic fibres recoil to their original size and shape, dilating the airway

Front 22

What is the meaning of the word tissue?

Back 22

A collection of similar cells performing the same function

Front 23

What is the difference between squamous epithelium and ciliated epithelium?

Back 23

Squamous-> flat and cells are very thin

Ciliated ->usually thicker, has numerous hair-like projections called cilia.

Front 24

What does squamous epithelium do?

-briefly-

Back 24

provides a short diffusion distance

Front 25

What does glandular tissue do?

-briefly-

Back 25

provides mucus

Front 26

What does nervous tissue do?

-briefly-

Back 26

carries messages to coordinate action

Front 27

What may cause airways to collapse (without the support of cartilage)?

Back 27

During inspiration, pressure inside the gaseous exchange system drops below the atmospheric pressure.

Front 28

How does cilia and mucus work together?

Back 28

mucus - traps pathogens

cilia - move mucus (containing trapped pathogens) up to back of mouth where they may be swallowed.

Front 29

Lung tissue contains many small blood vessels. Why are these blood vessels important?

Back 29

-Blood carries carbon dioxide in towards alveoli

-and oxygen away.

-many, small blood vessels give a larger surface area for gas exchange than fewer, larger vessels.

Front 30

Inspiration; how does air enter the lungs?

Back 30

pressure inside must be lower than the atmospheric pressure

-Diaphragm: contracts (move down, flatter, displaces organs beneath)

-External intercostal muscles: contract to raise the ribs

-volume of the chest cavity: increased

-pressure in the chest drop below atmospheric pressure

-air moved into lungs

Front 31

Expiration; how does air leave the lungs?

Back 31

-Diaphragm: relaxes, pushed up by the displaced organs beneath

-External intercostal muscles: relax, ribs fall

-Volume of chest cavity: decreased

-Pressure in the lungs increased above atmospheric pressure

-air moved out of the lungs

Front 32

What does ventilation ensure?

Back 32

-the concentrations of oxygen in the air of the alveolus remains higher than that in the blood

-the concentrations of carbon dioxide in the alveoli remains lower than that in the blood

Front 33

What is the breathing rate?

Back 33

the number of breaths per a minute

Front 34

What is the oxygen uptake?

Back 34

the volume of oxygen absorbed by the lungs in one minute

Front 35

What is the tidal volume?

Back 35

the volume of air inhaled or exhaled in one breath, usually measured at rest.

Front 36

What is the vital capacity?

Back 36

the greatest volume of air that can be expelled from the lungs after taking the deepest possible breath

Front 37

What is soda-lime for?

Back 37

Absorbs CO2 preventing it from being breathed back in

Front 38

What is the residual volume?

Back 38

Air remaining in the lungs after a deep breath out (to stop the lungs collapsing)

Front 39

The buccal cavity is...

Back 39

the mouth

Front 40

What is countercurrent flow?

Back 40

where two fluids flow in opposite directions

Front 41

What are filaments (primary lamellae)?

Back 41

Slender branches of tissue that make up the gill.

Front 42

What are lamellae (secondary lamellae)?

Back 42

folds of the filaments to increase the surface area, also known as gill plates.

Front 43

What is the operculum?

Back 43

a bony flap that covers and protects the gills

Front 44

What is the spiracle?

Back 44

an external opening or pore that allows air in and out of the trachea

Front 45

What is tracheal fluid?

Back 45

the fluid found at the ends of the tracheoles in the trachea system

Front 46

What is the trachea system?

Back 46

a system of air-filled tubes in insects.

Front 47

How does countercurrent flow work?

Back 47

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

-absorbs the maximum amount of oxygen from the water.

Front 48

How does the buccal cavity work?

Back 48

The floor of the mouth moves downwards, drawing water into the buccal cavity. The mouth then closes and the floor is raised again pushing water through the gills.

Front 49

How are movements of the operculum coordinated with the movements of the buccal cavity?

Back 49

As water is pushed from the buccal cavity, the operculum moves outwards. This reduced the pressure in the opercular cavity, helping water through to flow through the gills.

Front 50

Summarise briefly gas exchange in insects.

Back 50

-do not transport oxygen in the blood

-Open circulatory system

-body fluids act as both blood and tissue fluid

-Circulation is slow + affected by body movements

Front 51

Describe the steps of gas exchange in insects.

Back 51

-Tracheal system supplies air directly to respiring tissues

-Air enters the system via a spiracle

-The air is transported into the body through a serious of tubes; tracheae

-These divide into smaller tubes: tracheoles

-The ends are open and filled with tracheal fluid

(some exchange can happen through the thin walls of the tracheoles)

Front 52

Many insects are very active, how do these insects get a good supply of oxygen?

Back 52

When tissues are active, the tracheal fluid can be withdrawn into the body fluid in order to increase the surface area of the tracheole wall exposed to the air

->more oxygen can be absorbed

Front 53

What are the 3 main parts that make up the basic structure and function of blood vessels?

Back 53

innermost layer - endothelium

1 cell thick, smooth, to reduce friction (minimum resistance to flow of the blood)

middle layer - elastic fibres and smooth muscle

thicker in arteries than in veins to accomodate changes in blood flow and pressure as blood is pumped from heart

outer layer - collagen fibres

resistant to over-stretching.