3.1.1 c and d the mammalian gas exchange system Flashcards
adaptations of the nasal cavity when we breathe in
large surface area with rich blood supply to arm air when we breathe in.
hairy lining which secretes muscus to trap dust and bacteria.
moist surfaces to increase humidity of incoming air to prevent water loss in the alveoli
adaptations of the trachea when we breathe in
carries humid air to the lungs.
supported by a layer of cartilage that holds it open and prevents it from collapsing.
rings of cartilage are incomplete to allow the trachea to bend when we swallow food down the oesophagus.
lined with ciliated epithelial cells and goblet cells (which secrete mucus) that prevent dust and bacteria from entering
adaptations of the bronchus when we breathe in
extensions of the trachea that spilt into two for the left and right lung.
similar structure to the trachea but smaller.
adaptations of the bronchioles when we breathe in
bronchus divides to form bronchioles with a diameter of less than/equal to 1 mm.
have NO cartilage but have SMOOTH MUSCLE which contracts to cause them to constrict.
lined with a layer of flattened epithelium cells facilitating some gas exchange.
the alveoli
little air sacs where most gas exchange occurs.
200-300 micrometers in diameter.
made of a thin layer of flattened epithelial cells as well as some collagen and elastic fibres.
elastic fibres cause recoil which helps move air out of the alveoli.
what is elastic recoil in the alveoli?
the elastic tissues allow the alveoli to stretch when air enters and return back to its resting size which helps squeeze air out.
adaptations of the alveoli
300-500 million alveoli per lung making a combined surface area of 75 metres squared.
alveoli and capillary wall are one cell thick so there is a short diffusion distance.
around 280 million capillaries which maintain the concentration gradient and give a rich bool supply.
ventilation from breathing also helps maintain a concentration gradient
what is lung surfactant?
it lines the alveoli to lower surface tension and it’s what makes it possible for the alveoli to remain inflated
what is ventilation?
the movement of air in and out of the lungs that is brought about by pressure changes in the thoracic cavity
describe inspiration
energy using process.
diaphragm contracts, flattens and lowers.
external intercostal muscles contract, moving the ribs up and outwards.
volume of the thorax increases so pressure decreases.
the pressure is lower than atmospheric pressure so air is drawn into the lungs which equalises pressure inside and outside the lungs.
describe expiration
normal expiration is a passive process.
diaphragm relaxes.
external intercostal muscles relax so ribs move down and inwards.
elastic fibres in the alveoli return to their normal length.
volume of thorax decreases so pressure increases more than atmospheric pressure and air moves out the lungs so pressure is equal inside and outside the lungs again.
