EXCHANGE SURFACES

What is an amoeba?

single-celled organism

how does an amoeba use diffusion or active uptake, and why?

amoebas can use diffusion or active uptake to obtain all the materials it needs to stay alive because they're very small and therefore have a large SA:VOL

What does SA:VOL stand for?

Surface area to volume ratio

How do you work out SA:VOL?

Surface area divided by volume

(look at notes for example)

Fill in the gaps.

Large cubes have a ________ SA:VOL

Small cubes have a ________ SA:VOL

Large cubes have a smaller SA:VOL

Small cubes have a larger SA:VOL

Fill in the gaps.

The higher the SA:VOL, the ____ ______ a cell can supply all of its parts with useful substances (and remove waste).

The higher the SA:VOL, the more quickly a cell can supply all of its parts with useful substances (and remove waste).

What type of organisms will find it harder to obtain the materials they need by diffusion alone?

larger multicellular organisms

What are the 2 examples of organisms that have adaptations that increase their SA:VOL that you need to know?

Hydra and Flat worms

What adaptations do Hydra (small invertebrate that live in freshwater) have that increases SA:VOL?

hollow body

What adaptations do flat worms have that increases SA:VOL?

flattened bodies

What are the 2 examples of special exchange surfaces in multicellular organisms (with low SA:VOL) you need to know?

- lungs

- gills

what do the lungs and gills have that allow for efficient gas exchange?

a huge SA

Fill in the gaps.

The more metabolically active and organism is, the _______ the demand for ______. Therefore, aerobic respiration has to happen at a ______ rate. This means that the supply of ______ & _______ to cells must be fast and efficient.

The more metabolically active and organism is, the greater the demand for energy. Therefore, aerobic respiration has to happen at a faster rate. This means that the supply of oxygen & glucose to cells must be fast and efficient.

Endotherms (e.g. mammals and birds) maintain their own body temp, what do they need as a result?

lots of energy

LOOK AT NOTES FOR PRACTICAL ***

LOOK AT NOTES FOR PRACTICAL ***

What are the features of an efficient gas exchange surface?

- large SA

- thin layer

- good blood supply / ventilation to maintain gradient

Why is having a large SA an important feature of an efficient gas exchange surface?

so that (in a given time) more substances can cross the exchange surface

How is a large SA achieved in an efficient gas exchange surface?

achieved by folding membrane/wall

what is an example of a cell with a large SA?

root hair cell

Why is having a thin layer an important feature of an efficient gas exchange surface?

reduces time taken for molecules to diffuse across the surface

what is an example of a thin layer in an efficient gas exchange surface?

thin wall of alveoli (in the lungs)

Why is having a maintaining a steep diffusion gradient an important feature of an efficient gas exchange surface?

- ensures a fresh supply of molecules are present on one side of the exchange surface

- ensures removal of molecules on the other side of the exchange surface

Look at diagram on notes ****

Look at diagram on notes ****

State and explain the properties of an alveolus?

- large SA:VOL

- 300 million alveoli in a lung

- alveoli are very thin & lined with squamous epithelium (0.1 µm - 0.5µm thick)

- average diameter of an alveolus = 100 µm

- each alveolus is surrounded by a network of capillaries

- good blood supply: helps maintain concentration gradients bc blood is always taking oxygen away from alveolus & returning with carbon dioxide

- blood capillaries cover 87% of the surface of the alveoli

- surfaces are moist for gases to dissolve & to reduce water loss from the cells lining the alveolus, into the air (which is exhaled)

What do the walls of the alveoli contain?

- macrophages

- type II cells

what are macrophages in the walls of the alveoli?

phagocytes that constantly patrol the surfaces of the alveoli on a search & destroy mission to rid airways of bacteria

what are Type II cells in the walls of the alveoli?

produce a detergent-like substance (surfactant) that reduces surface tension, which prevents alveoli from sticking together

why is the passage of blood through the lungs slow?

- capillaries are very narrow (RBCs have to squeeze through)

- it gives time for gaseous exchange to occur

LOOK AT DIAGRAM OF STRUCTURE OF LUNGS ON HANDOUTS****

LOOK AT DIAGRAM OF STRUCTURE OF LUNGS ON HANDOUTS****

What key features must airways have/be?

must

- be large enough to allow air to flow freely

- divide into small enough tubes to reach the tiny alveoli

- able to withstand collapse due to low air pressure caused whilst you breathe in

- flexible so you can move and breathe

- able to stretch and recoil

What is the function of cartilage (in the wall of airways)?

provides support (cartilage is strong but flexible) - stops airways from collapsing when you breathe in and pressure drops

what is the function of ciliated epithelium (that lines the airways)?

wafts mucus out of airways towards the throat so mucus can be swallowed

what is the function of goblet cells (that line the airways)?

secrete mucus (mucus traps microbes and dust particles that enter airways when a person breathes in)

what is the function of smooth muscle (in the walls of airways)?

control diameter of airways (e.g. when muscles relax, airways widen)

what is the function of elastic fibres (in the walls of airways)?

stretch & recoil to help breathing out

how do smooth muscle and elastic fibres work together?

work antagonistically (against each other)

What happens to and in the airway when smooth muscle contracts?

When smooth muscle contracts, it causes the lumen (hole) of the bronchioles to become narrower (airway constricts). The elastic fibres stretch.

What happens to and in the airway when smooth muscle relaxes?

Relaxation of the smooth muscle causes the elastic fibres to recoil (return to normal shape). The airways are now said to be dilated (wider).

What type of muscle is the trachealis muscle?

smooth muscle

what does the trachealis muscle do?

bridges the gap between the free ends of C-shaped cartilage at the posterior border of the trachea, adjacent to the oesophagus.

What is the primary function of the trachealis muscle?

to constrict the trachea, allowing air to be expelled with more force (e.g. during coughing)

LOOK AT NOTES FOR DIAGRAM ON TRACHEA****

LOOK AT NOTES FOR DIAGRAM ON TRACHEA****

Is cartilage present or absent in the trachea of the airways, in what way?

present, C-shaped rings

Is smooth muscle present or absent in the trachea of the airways?

present

Are elastic fibres present or absent in the trachea of the airways?

present

Are goblet cells present or absent in the trachea of the airways?

present

Are ciliated epithelium present or absent in the trachea of the airways

present

Is cartilage present or absent in the bronchi of the airways, in what way?

present, smaller blocks

Is smooth muscle present or absent in the bronchi of the airways?

present

Are elastic fibres present or absent in the bronchi of the airways?

present

Are goblet cells present or absent in the bronchi of the airways?

present

Are ciliated epithelium present or absent in the bronchi of the airways

present

Is cartilage present or absent in the large bronchiole of the airways, in what way?

absent

Is smooth muscle present or absent in the large bronchiole of the airways?

present

Are elastic fibres present or absent in the large bronchiole of the airways?

present

Are goblet cells present or absent in the large bronchiole of the airways?

present

Are ciliated epithelium present or absent in the large bronchiole of the airways

present

Is cartilage present or absent in the small bronchiole of the airways, in what way?

absent

Is smooth muscle present or absent in the small bronchiole of the airways?

present

Are elastic fibres present or absent in the small bronchiole of the airways?

present

Are goblet cells present or absent in the small bronchiole of the airways?

absent

Are ciliated epithelium present or absent in the small bronchiole of the airways

present

Is cartilage present or absent in the smallest bronchiole of the airways, in what way?

absent

Is smooth muscle present or absent in the smallest bronchiole of the airways?

absent

Are elastic fibres present or absent in the smallest bronchiole of the airways?

present

Are goblet cells present or absent in the smallest bronchiole of the airways?

absent

Are ciliated epithelium present or absent in the smallest bronchiole of the airways?

no cilia

Is cartilage present or absent in the alveoli of the airways, in what way?

absent

Is smooth muscle present or absent in the alveoli of the airways?

absent

Are elastic fibres present or absent in the alveoli of the airways?

present

Are goblet cells present or absent in the alveoli of the airways?

absent

Are ciliated epithelium present or absent in the alveoli of the airways?

no cilia

what is the diaphragm?

a sheet of muscle

What does the rib cage do during inspiration?

moves up and out

what do the external intercostal muscles do during inspiration?

contract

what happens to the volume of the thorax during inspiration?

increases

what happens to the diaphragm during inspiration?

moves down and flattens and contracts

what happens to the volume of the thorax during inspiration, after the diaphragm contracts?

increases

what happens to the air pressure in the thoracic (chest) cavity during inspiration?

drops below air pressure outside of the body

how does air move during inspiration?

into the lungs

What happens to the rib cage during expiration?

moves down and in

what do the external intercostal muscles do during expiration?

relax

what happens to the volume of the thorax during expiration?

decreases

what happens to the diaphragm during expiration?

moves up and becomes bell-shaped and relaxes

what happens to the volume of the thorax during expiration, after the diaphragm relaxes?

decreases

what happens to the air pressure in the thoracic (chest) cavity during expiration?

rises above air pressure outside of the body

how does air move during expiration?

out of the lungs

What do the internal intercostal muscles do during inspiration and expiration?

nothing

What happens during inspiration?

- rib cage moves up and out

- external intercostal muscles contract

- volume of thorax increases

- diaphragm moves down and flattens

- diaphragm contracts

- volume of thorax increases

- air pressure in the thoracic (chest) cavity drops below the air pressure outside of the body

- air moves into the lungs

What happens during expiration?

- rib cage moves down and in

- external intercostal muscles relax

- volume of thorax decreases

- diaphragm moves up and becomes bell-shaped

- diaphragm relaxes

- volume of thorax decreases

- air pressure in the thoracic (chest) cavity rises above the air pressure outside of the body

- air moves out of the lungs

The more active you are, the more what do you need?

oxygen

what does the rate of oxygen supply to cells depend on?

- breathing rate (number of inhalations per minute)

- breathing depth

- heart rate (beats per min)

what is kung volume measured in?

decimetres (dm³)

how many cm and l is 1 dm³ = to?

1 dm³ = 1000 cm = 1 litre

what is the approx vol of a human lung?

5 dm³

define tidal volume

the volume of air breathed in and out in one breath

fill in the gaps.

with increasing activity, both the __________ & ________ of inhalation will increase

with increasing activity, both the frequency & depth of inhalation will increase

Define vital capacity

total volume of air that can be exhaled after a maximum inhalation

Define residual volume

amount of air remaining in the lungs at the end of maximum expiration

define ventilation rate

total volume of air moved into the lungs in 1 minute (dm³min⁻¹)