Exchange Surfaces and Breathing

Question 1

Why is diffusion alone, enough to supply the needs of single celled organisms?

Answer 1

• the metabolic activity of a single celled organism is usually low and the need for oxygen even lower
• the SA:V ratio of the organism is large

Question 2

What are the 4 examples of things an effective exchange surface has?

Answer 2

• increased surface area
• thin layers (faster rate of diffusion)
• good blood supply (to maintain the concentration gradient)
• ventilation to maintain diffusion gradient

Question 3

What is the human exchange system called?

Answer 3

gaseous exchange system

Question 4

Why do mammals e.g. humans need a high volume of oxygen and be able to get rid of c02 quickly?

Answer 4

they have a small SA:V ratio
they have a high metabolic rate (in order to maintain body temp independent of the environment)
need for respiration

Question 5

The Nasal cavity involves the first step of the human gas exchange system. How does it work?

Answer 5

• large SA, good blood supply, warms body temp
• hairy lining, secretes mucus and protects lungs from irritation and infection

Question 6

The trachea involves the second step to the human gas exchange system. How does it work?

Answer 6

Wide tube which is supported by rings of cartilage (stops the trachea from collapsing)
the rings are incomplete so that the food can move down the oesophagus behind trachea
trachea lined with ciliated epithelium with goblet cells between and below the epithelial cells

Question 7

What do goblet cells do?

Answer 7

secrete mucus onto lining of trachea, cilia beat and move the mucus, along with trapped dirt and microorganisms

Question 8

The third step in the human exchange system is the Bronchus. How does it work?

Answer 8

they are similar structure to the trachea , with supporting rings of cartilage but smaller

Question 9

The fourth step in the human gas exchange system is the bronchioles? How do thy work?

Answer 9

(1mm diameter or less)
inner walls contain smooth muscle, when muscle contracts they constrict and close, when the muscles relax they dilate

Changes the amount of air reaching the lungs

Question 10

The final step in the human gas exchange system is the alveoli? How do they work?

Answer 10

tiny air sacs, each one consists of a layer of thin, flattened epithelial cells, along with some collagen and elastic fibres

Allow to stretch to air in

Question 11

What are the main adaptations of the alveoli for effective gaseous exchange?

Answer 11

1. Large surface area - 300 - 500 million per adult lung, large SA:V ratio
2. Thin layers, capillaries and alveoli are one cell thick, shorter diffusion distance between the air and the blood
3. good blood supply
4. good ventilation

Question 12

What is lung surfactant?

Answer 12

Makes it possible for the alveoli to remain inflated, located on the inner surface of the alveoli of water and salt and lung surfactant

Question 13

What is the difference between internal and external intercostal muscles?

Answer 13

internal = inside

external = outside

Question 14

Inspiration is an energy using process. What is it?

Answer 14

• the dome shaped diaphragm contracts, flattening
• external intercostal muscles contract , moving ribs upwards and outwards
• volume of the thorax increases so pressure is reduced
• pressure is lower than the atmospheric air, so air is drawn in
• travels down the conc gradient to reach equilibrium

Question 15

Expiration is a passive process. How does it work?

Answer 15

• muscles in the diaphragm relax, into a dome shape
• external intercostal muscles relax, causing gravity to move the ribs down and inwards
• the elastic fibres in the alveoli return to normal length
• this decreases the volume of the thorax
• pressure inside the thorax is greater than the atmospheric air so air is forced outwards to reach equilibrium

Question 16

What are the three methods used for measuring the capacity of the lungs?

Answer 16

• peak flow meter
• vitalograph
• spirometer

Question 17

What is tidal volume?

Answer 17

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

Question 18

What is vital capacity?

Answer 18

volume of air that can be breathed in when deepest inhalation and deepest exhalation

Question 19

What is meant by inspiratory reserve volume?

Answer 19

max volume of air you can breathe in over and above normal

Question 20

What is meant by expiratory reserve volume?

Answer 20

extra amount of air you can force out of your lungs over and above normal

Question 21

What is meant by residual volume?

Answer 21

volume of air that is left in your lungs when exhaling as hard as possible (can’t be measured directly)

Question 22

What is meant by total lung capacity?

Answer 22

sum of the vital capacity and the residual volume

Question 23

What is meant by breathing rate?

Answer 23

number of breaths taken per minuet

Question 24

How do you calculate the ventilation rate?

Answer 24

tidal volume x breathing rate

Question 25

How does a peak flow meter work?

Answer 25

what you use to measure the rate at which air is expelled e.g. when you have asthma

Question 26

Why can no gaseous exchange take place in insects?

Answer 26

they have a tough exoskeleton

Question 27

How does gas exchange take place in insects?

Answer 27

along thorax and abdomen, there are small openings known as spiracles
air moves in and out of these as well as water

Question 28

What open and close the spiracles in insects?

Answer 28

the spiracle sphincters (used to prevent water loss)

Question 29

What structure leads away from the spiracles and what does it do?

Answer 29

The tracheae, large tubes in the respiratory system
run both into and along the body
lined with chitin (which makes up the cuticle)
relatively impermeable to gases

Question 30

The tracheae branches to form what and what does it do?

Answer 30

tracheoles, single elongated cell, no chitin so permeable to gases
they are so small spread throughout tissue running between cells
gas exchange takes place

Question 31

What is located at the end of tracheoles and what does it do?

Answer 31

tracheal fluid, which limits the penetration of air for diffusion
when oxygen is low, lactic acid can build up causing the water to spread out more, more efficient gas exchange

Question 32

When insects have a higher energy demand, the may use mechanical ventilation of the tracheal system. How does this work?

Answer 32

air actively pumped into the system by muscular pumping system in the thorax, causes pressure changes
air is forced in/out

Question 33

How does having collapsible enlarged trachea/ air sacs help gas exchange?

Answer 33

they are used to increase the amount of air moved, they can be inflated/deflated by ventilating movements of the thorax/abdomen