Please enable JavaScript.
Coggle requires JavaScript to display documents.
human gas exchange system (Alveoli (adaptations for effective gas exchange…
human gas exchange system
Nasal cavity
large surface area - good blood supply, warms air to body temperature
hairy lining - secretes mucus to trap dust and bacteria, protecting delicate lung tissue from irritation and infection
moist surfaces - increase humidity of incoming air, reducing evaporation from exchange surfaces
Trachea
main airway - carries clean, warm, moist air from nose to chest
wide tube supported by incomplete rings of strong, flexible cartilage - stop trachea from collapsing
food can move easily down oesophagus behind trachea
lined with ciliated epithelial cells, with goblet cells between epithelial cells
goblet cells secrete mucus onto lining of trachea - trap dust and microorganisms which escaped nose lining
cilia beat and move mucus, trapped dirt and microorganisms away from lungs
goes to throat - swallowed and digested
cigarette smoke stops cilia beating
Bronchus
trachea divide to form left and right bronchus
similar in structure to trachea - supporting rings of cartilage, but smaller
Bronchioles
bronchi divide to form many small bronchioles in lungs
smaller bronchioles have no cartilage rings
contain smooth muscle
smooth muscle contracts - bronchioles constrict (close up)
smooth muscle relaxes - bronchioles dilate (open up)
changes amount of air reaching lungs
lined with a thin layer of flattened epithelium - some gaseous exchange possible
Alveoli
tiny air sacs - main gas exchange surfaces of the body
structure - layer of thin, flattened epithelial cells, collagen and elastic fibres
elastic fibres allow alveoli to stretch as air is drawn in
returning to resting size helps air to squeeze out - elastic recoil
adaptations for effective gas exchange
large surface area - 300-500 million alveoli per adult lung
important in increasing SA:V ratio
thin layers - alveoli and capillaries surrounding them have one epithelial cell thick walls
diffusion distances between the air in alveolus and blood in capillaries are very short
good blood supply - alveoli are surrounded by a network of capillaries
constant flow of blood through capillaries brings carbon dioxide and carries away oxygen
steep concentration gradient is maintained
good ventilation - breathing moves air in and out of alveoli
maintains steep concentration gradient for oxygen and carbon dioxide
lung surfactant - covers inner surface of alveoli
allows alveoli to remain inflated
inner surface of alveoli - covered in layer of water, salts and lung surfactant solution
oxygen dissolves in this water before diffusing into blood
loss of water - water can evaporate into air in alveoli