Gas Exchange In humans

HUMANS need to get OXYGEN into the BLOOD for RESPIRATION.

C02 needs to be DISPOSED OF.

GAS EXCHANGE ASSIST with this.

FOUND : Between the ribs

STRUCTURE : Two including INTERNAL and EXTERNAL

-The internal intercostal muscles are found inside of the external intercostal muscles.

-These two sets help with breathing.

-External intercostal muscles and diaphram muscles contract.

-This causes the rib cage to move upwards and the diaphram to flatten.

-This then increases the thoracic cavity, so the lung pressure dereases.

-Air flows from trachea to lungs (down a pressure gradient).

-Energy is required as inspiration is an active process

-External intercostal muscles and diaphram muslces relax

-The ribcage moves downwards and inwards, whilst the diaphram curves upwards.

-Volume of thoraic cavity decreases, causing pressure to increase.

-Air is pushed down a pressure gradient and out of the lungs.

What are they? - Small air sacs surrounded by a network of capillaries.

AVEOLAR EPITHELIUM : JSingle layer of thin, flat cells making up the wall of each aveoli.

CAPILLIARY ENOTHELIUM : Make up wall of the capillaries.

ELASTIN : Protein inside aveoli walls which helps aveoli to return to its normal shape after inhaling and exhaling.

Oxygen diffuses out of the aveoli, across the alveolar epithelium and the capillary endothelium and into a compound called haemoglobin located in the blood.

Carbon dioxide diffuses into the alveoli from the blood.

TRACHEA - BRONCHI - BRONCHIOLES - ALVEOLI - AE - CE - BLOOD

________________________________ __________________________________           PRESSURE GRADIENT                              DIFFUSION GRADIENT

(oxygen in the air)                                                                   (oxygen in haemoglobin)

(Carbon dioxide moves in an opposite direction)

Aveoli has features which speed up the rate of diffusion.

THIN EXCHANGE SURFACE : The aveolar epithelium is only one cell thick, creating a short diffusion pathway.

LARGE SURFACE AREA :  There is a large amount of aveoli, meaning theres a large surface area.

STEEP CONCENTRATION GRADIENT : Of oxygen and carbon dioxide between the aveoli and the capillaries.