7.2 The mammalian gaseous exchange system

Question 1

Nasal cavity:

Answer 1

-large surface area with good blood supply to warm the air to body temperature
-hairy lining, which secretes mucus to trap dust and bacteria, protecting delicate lung tissue from irritation and infection
-moist surfaces, to increase humidity of incoming air, reducing evaporation from exchange surfaces

Question 2

Trachea:

Answer 2

-supported by incomplete rings of strong, flexible cartilage, which stops trachea from collapsing and incomplete so food can easily move down the oesophagus behind
-lined with ciliated epithelium with goblet cells between and below the epithelial cells
-goblet=mucus
-cilia=beat and move mucus away from lungs to be digested
-smoking=cilia cant beat

Question 3

Bronchus

Answer 3

-supporting rings of cartilage but smaller

Question 4

Bronchioles

Answer 4

-smooth muscle
=when contract, bronchioles constrict
=when relax, bronchioles dilate
-lines with thin layer of flattened epithelium=some gaseous exchange possible

Question 5

Alveoli

Answer 5

-layer of thin, flattened epithelial cells
-collagen
-elastic fibres (allow to stretch as air drawn in)
=when return to resting size, help squeeze air out = elastic recoil
-large surface area 50-75 m^2
-thin layers, single epithelial cell thick=short diffusion distance between alveoli and capillaries
-good blood supply-network of capillaries surround= constant blood flow to bring CO2 and take O2= steep conc gradient
-good ventilation-breathing= moves air in and out and keeps steep conc gradient

Question 6

Lung surfactant

Answer 6

-thin layer of solution of water, lung surfactant covers inner surface of alveoli
-allows for alveoli to remain inflated
O2 dissolves water before diffusing into blood but H2O can also evaporate into air in alveoli

Question 7

Rib cage

Answer 7

-semi-rigid case within which pressure can be lowered with respect to the air outside it

Question 8

Diaphragm

Answer 8

-broad, domes sheet of muscle, which forms the floor of the thorax

Question 9

Thorax lines by

Answer 9

pleural membranes, space between=pleural cavity and usually filed with a thin layer of lubricating fluid so membranes slide easily over each other as you breathe

Question 10

Inspiration (inhalation) (energy using)

Answer 10

-diaphragm contracts, flattens and lowers
-external intercostal muscles contract, moving ribs upwards and outwards
-volume of thorax increases so pressure is reduced
-pressure now lower than atmospheric pressure
-air is drawn through nasal passages, trachea, bronchi and bronchioles into lungs

Question 11

Expiration (exhalation) (passive)

Answer 11

-diaphragm relaxes, so up and out
-external intercostal muscles relax so ribs move down and inwards under gravity
-elastic fibres in alveoli return to normal length
-volume in thorax decreases
-now pressure inside thorax is greater than atmospheric pressure
-air moves out of lungs until pressure inside and out is equal again

Question 12

Exhale using energy

Answer 12

-internal intercostal muscles contract
-pulling ribs down hard and fast
-abdominal muscles contract forcing diaphragm up to increase pressure in lungs rapidly