human gas-exchange

Question 1

why do organisms need a constant supply of oxygen?

Answer 1

to release energy in the form of ATP during respiration

Question 2

why does carbon dioxide need to be removed from the body?

Answer 2

build up can be harmful to the body

Question 3

the volume of oxygen absorbed is large and the volume of carbon dioxide removed is large because..?

Answer 3

• lots of living cells
• maintain high body temp which is related to high metabolic and respiratory rates

Question 4

why are lungs not located on the ouside of the body?

Answer 4

• air is not dense enough to protect these delicate structures
• body as a whole would loose water quickly and dry out

Question 5

what are the lungs?

Answer 5

a pair of lobed structures made up of a series of highly branched tubules, called bronchioles, which end up in tiny air sacs- alveoloi

Question 6

what is the trachea?
what do the rings of cartilage do?

what are the walls made up of?

Answer 6

a flexible airway that is supported by rings of cartilage. The cartilage prevents the trachea from collapsing as the air pressure inside falls when breathing in.

the tracheal walls are made up of muscle, lined with ciliated epithelium and goblet cells

Question 7

what is the bronchi?

what is the function?

Answer 7

two divisions of the traches.

they produce mucus to trap dirt particles and have cilia the move dirt to mucus in the throat

Question 8

what are the bronchioles?

what are their walls made up of and how do it help it to carry out it’s function?

Answer 8

branching subdivision of the bronchi.

the walls are made of muscle lined with epithelial cells . the muscle allows them to constrict so they can control the flow of air in and out of the alveoli

Question 9

what are the alveoli?

what are the properties of the alveoli and how does it help it to carry out its job?

Answer 9

are small air sacs.
between the alveoli there are some collagen and elastic fibres. the alveoli are lined with epithelium.
the elastic fibres allow the alveoli to stretch as they fill with air when breathing in. they then spring back during breathing out in order to expel c02 rich air.

Question 10

explain the movement of air from nose to the lungs?

Answer 10

nostrils
nasal cavity
pharynx
larynx
trachea
bronchi
bronchioles

Question 11

explain the function of these in gas exchange

Answer 11

nostril to nasal cavity - has hairs and mucus is present to filter the air. temperature of air changes here according to body temp
pharynx - where germs are removed
to the larynx to trachea - has mucus to filter the air more breaks into the bronchi - bronchioles - contain air sacs, alveoli where diffusion occurs

Question 12

what is ventilation?

Answer 12

constant movement of air into and out of the lungs

Question 13

explain why air is forced into the lungs?

Answer 13

the air pressure of the atmosphere is greater than the air pressure inside the lugs so air is forced in - this is called inspiration

Question 14

when is air forced out of the lungs?

Answer 14

when the air pressure of the lungs is greater than that of the atmosphere - this is called expiration

Question 15

describe the process of inhalation in the lungs?

Answer 15

The external intercostal muscles contract, while the internal intercostal muscles relax.

The ribs are pulled upwards and outwards, increasing the volume of the thorax.

The diaphragm muscles contract, causing it to flatten, which also increases the volume of the thorax.

The increased volume of the thorax results in reduction of pressure in the lungs.

atmospheric pressure is now greater than pulmonary pressure, and so air is forced into the lungs

Question 16

what type of process is expiration?

Answer 16

largely passive - does not require much energy

Question 17

describe the process of exhalation in the lungs?

Answer 17

The internal intercostal muscles contract, while the external intercostal muscles relax.

The ribs move downwards and inwards, decreasing the volume of the thorax.

The diaphragm muscles relax and so is pushed up again by the contents of the abdomen that were compressed during inspiration the volume of the thorax is further reduced.

The decreased volume of the thorax increases the pressure in the lungs.

The pulmonary pressure is now greater than that of the atmosphere so air is forced out of the lungs.

Question 18

why do our lungs expand with our chest while breathing?

Answer 18

Each of the lungs is enclosed in a double membrane known as the pleural membrane. The space between the two membranes is called the pleural cavity, and is filled with a small amount of pleural fluid.
This fluid lubricates the lungs. It also adheres to the outer walls of the lungs to the thoracic (chest) cavity by water cohesion, so that the lungs expand with the chest while breathing.

Question 19

what is the pulmonary ventilation rate?

Answer 19

the total volume of air that is moved into the lungs in 1 minute

Question 20

how do we calculate the pulmonary ventilation rate?

Answer 20

tidal volume (dm^3) x breathing rate (min-1)

Question 21

what is the tidal volume?

Answer 21

volume of air normally taken in at each breath when the body is at rest. usually 0.5dm3

Question 22

what is the breathing rate?

Answer 22

the number of breaths taken in a minute. normally 12-20 breaths in a healthy adult

Question 23

what is the average size of an alveoli?

Answer 23

100-300μm

Question 24

the capillaries and the alveoli are made up of…?

Answer 24

a single layer of cells

Question 25

each alveolus is lined with…?

Answer 25

epithelial cells

Question 26

why will diffusion of gases between the alveoli and the blood very rapid?

Answer 26

• red blood cells are slowed as they pass through pulmonary capillaries, allowing more time for diffusion
• the distance between the alveolar air and red blood cells is reduced as the red blood cells are flattened against the capillary walls
• the walls of the alveoli and capillaries are thin and therefore a short diffusion distance
• 300 mill alveoli and pulmonary capillaries have a large total SA
• breathing movements constantly ventilate the lungs, and the action of the heart constantly circulates blood around the alveoli together these ensure a conc. gradient is maintained
• blood flow through the pulmonary capillaries maintains a conc. gradient

Question 27

lung surfactant use?

Answer 27

The moist epithelium of the alveoli exerts a surface tension;
The alveoli could collapse at expiration;
Alveolar stability is achieved by the pulmonary surfactant present at the air-liquid interface which reduces surface tension

Question 28

what is a spirometer?

Answer 28

a device that measures the volume of air that passes through it during breathing . its results can be placed on a kymograph trace

Question 29

Which common diseases will impair lung function?

Answer 29

Asthma

Pulmonary fibrosis

Emphysema

Tuberculosis

Question 30

what is asthma and what causes it?

Answer 30

Localised allergic reaction that affects the bronchioles.
Allergens that stimulate asthma are pollen, animal fur and house dust mites faeces.
Thought to be a genetic link but doesn’t explain increase in incidence

Question 31

what is pulmonary fibrosis and what causes it?

Answer 31

The development of fibrous inelastic tissue between the alveoli.
Pulmonary fibrosis is most commonly associated with people working with substances such as asbestos, coal dust and metal dust.

Question 32

what is emphysema and what causes it?

Answer 32

The walls of the alveoli breakdown reducing the surface area.
Loss of elasticity of lung tissue.
Associated with air pollutants and smoking.

Question 33

How does Asthma affect lung function?

Answer 33

Muscle walls contract, Inflammation,
Mucus, Narrowing of bronchiole

Greater resistance to air flow in and out of alveoli

Difficulty in ventilation of lungs and maintenance of diffusion gradient across exchange surface

Reduction of O2 levels in the blood (cyanosis may result where skin turns bluish)

Question 34

How does pulmonary fibrosis affect lung function?

Answer 34

The walls are thicker due to formation of inelastic fibrous tissue which cause lungs to stiffen.
Thickened epithelium of alveoli increases the diffusion pathway so diffusion of oxygen into blood is slow

Reduced intake of O2 into blood results in decrease in release of energy by cellular respiration

Loss of elasticity of lungs makes ventilation more difficult. Breathing is shallow as lungs do not expand normally due inspiration or collapse fully during expiration

Question 35

How does Emphysema affect lung function?

Answer 35

The alveoli are larger in size which will reduce the surface area.
Smoke stimulates white blood cells to release protein digesting enzymes which break down the walls of the alveoli
These enzymes also reduce the elasticity of the lungs by breaking down the elastic tissue

Smaller alveoli surface area leads to reduced O2 levels in the blood leading to a decrease in release of energy by cellular respiration

Loss of elasticity reduces the ability of the lungs to recoil after breathing in which makes ventilation more difficult

Question 36

define incidence

Answer 36

number of cases of a disease in a certain group, in a given time. Expressed as number in a standard sized group e.g. per 1000