Gas exchange in mammals and plants

What’s pulmonary ventilation

The movement of fresh air into the lungs and removal of stale air out of the lungs

How is Pulmonary ventilation measured

PV = tidal volume x breathing rate

What’s FEV1

Forced expiratory volume in 1 second - the volume of air forcibly exhaled in the first second of forced exhalation

PEFR

Peak expiratory flow rate - maximum rate of forced exhalation through the mouth

what is tidal volume

the volume of air inhaled or exhaled in a normal deep breath

what is breathing rate

the number of breaths taken in in a given time period

what is vital capacity

maximum volume of air exhaled after the deepest inhalation (breath in)

what is residual volume

volume of air that remains in the lungs after a forced exhalation

what can cause respiratory arrest

• obstruction of trachea/bronchi

• asthma attack

• heart attack

• drug overdose

how to treat respiratory arrest: expired air resuscitation

1. call 999

2. open airway by removing any visible obstruction from mouth + tilting head back

3. check breathing: look for chest movements + listen to breathing sounds

4. pinch nostrils (prevent air escaping) and exhale into mouth —> chest should rise

5. check for pulse —> no pulse do CPR

how does air resuscitation differ for babies

• cover both nose and mouth with your mouth

• give smaller, more gentle breaths

how is the alveoli adapted for gas exhange

1. large surface area —> increases surface are —> more diffusion of O2/CO2 per unit time

2. thin —> each alveoli made from single epithelium layer —> shorter diffusion distance —> increased rate of diffusion (capillaries are also one cell thick)

3. good blood supply - large capillary network surrounds each alveoli —> maintains conc gradient so O2/CO2 can be exchanged in opposite directions

4. well ventilated —> steep diffusion gradient

why do we need a specialised gas exchange system

• humans have low SA:V

• hard to exchange enough gases to meet demands + remove waste a suitable rate

what specialised structures are in the GES + what’s their role

• trachea - C-shaped rings of cartilage —> provide support + prevent trachea/bronchi collapsing during inhalation

• bronchi - divides into bronchioles

• bronchioles - has alveoli at the ends

• alveoli - site of gas exchange —> walls have collagen to provide structural support —> layer of surfactant which reduces surface tension of water

• goblet cells - secrete mucus to trap pathogens

• cilia - hair-like extensions that waft mucus up

what tissues + muscles are in trachea, bronchioles + alveoli

• trachea - smooth muscle, elastic fibres, ciliated epithelium (goblet cells) +glandular/connective tissue, cartilage

• bronchioles - smooth muscle, elastic fibres, ciliated epithelium (goblet cells)

• alveoli - elastic fibres

role of elastic fibres in alveoli/lungs

• inhalation - elastic fibres STRETCH to allow alveoli to INFLATE —> also prevents alveoli from bursting

• exhalation - elastic fibres RECOIL to DEFLATE alveoli

• allows lung tissue to expand + recoil

role of surfactant in alveoli

• reduces surface tension of water —> prevents alveoli sticking together in exhalation

• easier to inflate the lungs

• allows O2 to diffuse into surfactant, then into alveoli

• has antibacterial chemicals

outline inhalation

• external intercostal muscles contract

• ribcage moves up and out

• diaphragm contracts

• volume of thorax + lungs increases

• pressure in lungs decreases

• air goes into lungs

outline exhalation

• external intercostal muscles relax

• ribcage moves in and down

• diaphragm relaxes

• volume in thorax/lungs decreases

• pressure in lungs increases

• air rushes out of lungs