3.3.2 human gas exchange

Give the gross structure of the lungs, trachea, bronchi, bronchioles and alveoli- label the picture

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

Trachea- flexible airway supported by rings of cartilage- which prevents the trachea from collapsing in on itself when breathing in

Bronchi - two divisions of the trachea, each leading to one lung. They are similar to trachea structure and also produce mucus to trap dirt particles and cilia that move it towards the throat

Bronchioles - series of Branching subdivisions of the bronchi.

Alveoli- minute air-sacs at the end of the bronchioles where gas exchange occurs

Give the adaptations of the alveoli , what’s the name of thee surface on the alveoli

Alveolar epithelium

• large surface area - millions of alveoli increase the surface area and are tightly packed

• Thin exchange surface- alveolar epithelium is one cell thick - the epithelial cells are also flattened. Provides a short diffusion pathway

• Good blood supply - alveoli are surrounded by a dense capillary network- maintains steep diffusion gradient.

• Red blood cells are slowed as they pass through pulmonary capillaries- allowing more time for diffusion

• The distance between the red blood cells and alveolar air is reduced as the red blood cells are flattened against the capillary walls

What. Is ventilation

The process of inspiration and expiration to maintain a concentration gradient for gas exchange. It relies on pressure changes in the thoracic cavity due to actions of the diaphragm and the intercostal muscles

Which gases are exchanged in the lungs

Oxygen diffuses down its concentration gradient from the air into the blood

Carbon dioxide diffuses down its concentration gradient from the blood into the air

The concentration gradients required are maintained by the ventilation in the lungs - forcing the air into/out and the continuous flow of blood into the capillaries- carries the blood away from the capillaries at a high rate so there is always a lower concentration gradient/ a higher gradient

Describe eh mechanism of inhalation

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 oof the thorax results in the reduction of pressure in the lungs

Atmospheric PRESSURE is now greater than the pulmonary pressure and so air is forced into the lungs

During inhalation, what happens to the ribs

They are pulled upwards and outwards

During inhalation, which intercostal muscles relax relax and which contract

External - contract

Internal- relax

Describe the process of exhalation

• internal intercostal muscles contract and the external intercostal muscles relax

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

• The diaphragm muscles relax and so it is pushed by the contents of the abdomen that were compressed during inspiration. Volume of the thorax is therefore further decreased

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

• The pulmonary pressure is now greater than that of the atmosphere, and s air is forced out of the lungs

What type of relationship does the internal and external intercostal muscles have

An antagonistic interaction - means one does the opposite of the other so one is always contracting and one is always relaxing

(Understanding) where are the external intercostal muscles

Between the ribs and the lungs - and then the contract the ribs are pulled upwards and outwards

Leads to inspiration

(Understanding) where are the intercostal muscles

Located deeper to the external intercostal muscles

They pull the ribcage downwards and inwards- causing expiration