7.2 The mammalian gaseous exchange system

Question 1

the need for humans

Answer 1

They’re big and have a small SA:V ratio

Active and maintain own body temperature so high metabolic rate

Question 2

nasal cavity

Answer 2

a large surface area with a good blood supply, which warms the air to body temperature

a hair lining which secretes mucus to trap dust and bacteria protecting lung tissue from irritation and infection

moist surfaces, which increase the humidity of incoming air, reducing evaporation from exchange surfaces

Question 3

Trachea

Answer 3

wide tube supported by incomplete rings of strong flexible cartilage, preventing collapse.

Rings incomplete so food can move easily down the oesophagus

ciliated epithelium and goblet cells, which secrete mucus to trap dust and dead micro organsims. Cilia beat to move mucus away from lungs

Question 4

bronchus

Answer 4

smaller supporting rings of cartilage

split in two to form the left and right bronchus

Question 5

bronchioles

Answer 5

no cartilage rings.

smooth muscle which contract and the bronchioles constrict and relaxes and the bronchioles dilate

flattened epithelium

Question 6

alveoli

Answer 6

tiny air sacs

200-300 micrometers in diameter

flattened epithelial cells, collagen and elastic fibres

elastic recoil- alveoli stretch as air is drawn in. when returning to original size, they help squeeze air out.

Question 7

adaptions of the alveoli

Answer 7

large surface area- millions of them

walls only one epithelial cell thick, short diffusion distance

good blood supply- network of many capillaries

good ventilation

lung surfactant enables the alveoli to reman inflated

Question 8

rib cage

Answer 8

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

Question 9

diaphragm

Answer 9

broad domed sheet of muscle, forming the floor of the thoraz

Question 10

intercostal muscles

Answer 10

in between the ribs

Question 11

pleural membranes

Answer 11

line the thorax and surround the lungs. the space between them is the pleural cavity and is filled with a thin layer of lubricating liquid so membranes slide easily over each other as you breath

Question 12

inspiration

Answer 12

diaphragm contracts, flattening and lowering

external intercostal muscles contract, moving rib cage up and out

vol of thorax increases so pressure decreases, lower than the atmospheric air

air drawn in, equalising pressure

Question 13

expiration

Answer 13

passive

diaphragm relax, moves up to its resting dome shape

external intercostal muscles relax, ribs move down and in

elastic fibres return to normal lengh

vol of thorax decreases, pressure increases to above atmospheric air pressure

air moves out until pressure is equal

Question 14

exhaling forcibly

Answer 14

using energy

internal intercostal muscles contact, ribs pulled down hard and fast

abdominal muscles contracting helps force diaphragm up to rapidly increase lung pressure