7.2 The mammalian gaseous exchange system

what are features of the nasal cavity

• large SA, good blood supply

• hairy lining, secrete mucus trap dust and bacteria

• moist surface, inc humidity dec evaporation

what is the trachea for

main airway carrying air from the nose down into the chest

what is the trachea supported with

c shaped rings of cartilage

why is the trachea supported

to stop it from collapsing

why are the cartilage rings c shaped

so food can move easily down oesophagus behind

what lines the trachea

ciliated epithelium with goblet cells

what is role of goblet cells

secrete mucus onto lining to trap dust and microorganisms

what is the role of cilia

beat and move the mucus and trapped dirt and microorganisms away from lungs

what does smoking do to the cilia

stop it from beating, dirt and microorganisms enter lungs

what does the trachea branch into

bronchus (bronchi), like the trachea but smaller

what do the bronchi branch into

bronchioles

what differentiates bronchioles from bronchi

• no cartilage rings

• contain smooth muscle

• lined with squamous epithelium

what is at the end of bronchioles

alveoli

what is the role of the alveoli

• main gas exchange surface of body

• squamous epithelium, collagen and elastic fibres

what is the elastic recoil of the lungs

alveoli stretch as air drawn in, when return to resting size, help squeeze air out

how are alveoli adapted for gas exchange

• large SA

• thin layer

• good blood supply

• good ventilation

what is lung surfactant

makes it possible for alveoli to remain inflated

what is ventilation

movement of air as a result of pressure changes brought about by breathing movements

what external intercostal muscles do in inspiration

contract - ribs up and out

what external intercostal muscles do in expiration

relax - down and in

what internal intercostal muscles do in inspiration

relax - increase volume of thorax

what internal intercostal muscles do in expiration

contract - decrease volume of thorax

what happens to diaphragm in inspiration

contract and flatten

what happens to diaphragm in expiration

relax dome shape

what happens to air pressure in lungs in inspiration

reduced

what happens to air pressure in lungs in expiration

increased

which way does the air move in inspiration

into lungs

which way does the air move in expiration

out of lungs

what happens to lung volume in inspiration

increase

what happens to lung volume in expiration

decrease