The Mammalian Gaseous Exchange System 7.2

Question 1

What gases are exchanged in humans and where?

Answer 1

Oxygen is taken in and Carbon Dioxide is taken out. This happens in the lungs

Question 2

Name all the parts of the gaseous exchange system

Answer 2

Nose, nasal cavity, mouth, larynx, trachea, bronchus, bronchioles, alveoli.

Question 3

Nasal Cavity

Answer 3

Good blood supply - warm the air to body temp
Large surface area - more air can enter
Hairy lining - traps dirt, bacteria and all things that shouldn’t be in lungs.
Good humidity - so it can be similar humidity to the inside of the body, will reduce evaporation on exchange surface.

Question 4

Trachea

Answer 4

This is the main airway which carries warm, clean air from the nose to the bronchus. It has c-shaped rings of cartilage that help reinforce its structure and support it. It is lined with ciliated epithelial cells that have goblet cells and these release mucus to trap any escaped bacteria that will then be swept by the cilia. Smoking damages this.

Question 5

Why are the rings of cartilage on the trachea incomplete?

Answer 5

So that there is room for food to travel through the oesophagus in the back.

Question 6

Bronchus

Answer 6

This is in the chest cavity and the trachea has split into two bronchi, the left and right corresponding to each lung, they have the same structure as the trachea

Question 7

Bronchioles

Answer 7

The bronchi will spilt into bronchioles which are very small (1mm diameter). They have no cartilage rings and are made of smooth muscle which contracts and relaxes to control the amount of air entering the alveoli. They are made of epithelium which is thin so some gas exchange can occur.

Question 8

Alveoli

Answer 8

Tiny air sacs at the end of the bronchioles that is where the main gaseous exchange occurs. They are made of epithelial cells and are very thin so that they can let gases diffuse easily. They also have elastic fibres so that they can stretch to hold more air when the air goes the alveoli will help squeeze the air out which is known as elastic recoil.

Question 9

What capillary surround the alveolus

Answer 9

The pulmonary capillary

Question 10

How gas exchange works

Answer 10

As you breathe air in and it enters the alveoli, there will be a high conc of oxygen and low conc of CO2 in the alveoli. In the pulmonary capillary that surrounds the alveoli, there is a low conc conc and a high conc of CO2. This means that oxygen will diffuse into the capillary and bind to the haemoglobin in red blood cells and the CO2 will diffuse into the alveoli and be exhaled as waste.

Question 11

Main adaptations of the alveoli

Answer 11

They have a big surface area - it allows the gases to diffuse quicker
They are thin - there’s only a small distance for the gases to travel so diffusion is fast
They have a good blood supply - there’s a capillary surrounding it.
They have good ventilation - you are inhaling and exhaling all the time.

Question 12

Lung Surfactant

Answer 12

There are water, salt and lung surfactant in the alveoli that keep them inflated. Oxygen dissolves in water before it diffuses which can be limiting as the water might evaporate in the air of the alveoli. They are adapted against this.

Question 13

How does air enter the lungs?

Answer 13

Air can enter the lungs because of pressure changes in the thorax brought about by the breathing movements.

Question 14

What is ventilation?

Answer 14

The movement of air

Question 15

What helps ventilate the lungs?

Answer 15

The ribcage is a semi-rigid case within which pressure can be lowered inside depending on the pressure outside. The diaphragm is a long sheet of muscle that is the floor of the thorax. The intercostal muscles, both interior and exterior sit between the ribs and enable them to move. There is lubricating fluid in the pleural cavity to lubricate the movement of membranes.

Question 16

Inspiration

Answer 16

This is the breathing in of air which is an energy-using process. The diaphragm will contract, flatten and lower which allows the lung size to increase. The ribcage will move upwards and outwards to reduce the pressure in the pleural cavity, this change in pressure allows air to be drawn into the lungs to maintain an equilibrium inside and outside the chest.

Question 17

Expiration

Answer 17

This is the breathing out of air and is a passive process. The diaphragm will relax and return to its dome shape. The ribcage will go down and in caused by the external intercostal muscles relax. The alveoli will also return to its normal size and this will reduce the pressure in the chest cavity and air will be forced out.

Question 18

What happens if you exhale forcibly?

Answer 18

This requires energy. Your interior intercostal muscles will contract which will force your ribcage up and out sharply. By using your abdominal muscles you force the diaphragm up which increases pressure in the lungs rapidly.