UNIT 3 (topic 2) gas exchange in people

Question 1

what is respiration

Answer 1

process by which energy is released from molecules of glucose, and ATP is synthesised

Question 2

what is ventilation

Answer 2

a sequence of breathing movements, moves air in and out, to and from the gas exchange surfaces

Question 3

what is the order of structures air travels through for one inhalation and one exhalation

Answer 3

through the nostril, trachea, bronchi, bronchioles, alveoli, bronchioles, bronchi, trachea

Question 4

what are the mechanisms of inspiration

Answer 4

• external intercostal muscles contract, internal intercostal muscles relax
• diaphragm muscles go down and flatten (contract)
• ribs move up and out
• volume of thoracic cavity increases, pressure decreases
• air flow into the lungs down a pressure gradient

Question 5

what are the mechanisms of expiration

Answer 5

• external intercostal muscles relax, internal intercostal muscles relax
• diaphragm muscles go up and expand (relax)
• ribs move down and in
• volume of thoracic cavity decreases, pressure increases
• air flows out the lungs down a pressure gradient

Question 6

what happens to intercostal muscles during active expiration

Answer 6

external = relax
internal = contract

Question 7

adaptions of the alveoli and capillaries for sufficient gas exchange

Answer 7

short diffusion pathway = alveoli walls are a single layer of epithelial cells, capillary walls one cell thick
steep concentration gradient = in alveoli, when O2 conc. decreases, we breathe air out and breathe in O2, capillaries carry oxygenated blood away
large SA = lots of alveoli, alveoli walls fold, lots of capillaries surrounding alveoli

Question 8

what are the adaptions of capillaries for gas exchange

Answer 8

narrow so only one RBC can pass through at a time = allows maximum time therefore maximum amount of diffusion to happen
narrow so every RBC passing through is pushed against the capillary walls = reduces the diffusion pathway to each RBC

Question 9

explain what is meant by tidal volume

Answer 9

volume of air taken in and out in one breath at rest

Question 10

what is inspiratory reserve volume

Answer 10

amount of extra inhaled air above tidal volume during a forceable breath in

Question 11

what is expiratory reserve volume

Answer 11

amount of extra exhaled air above the tidal volume during a forceable breath out

Question 12

what is the vital capacity

Answer 12

maximum amount of air a person can expel from the lungs after maximum inhalation

Question 13

what is the breathing rate

Answer 13

breaths per minute

Question 14

what is the equation for the PVR

Answer 14

PVR = TV x BR
volume exchanged with the environment per minute = tidal volume x breathing rate

Question 15

what is meant by FEV1

Answer 15

forced expiratory volume
- measured during the first second

Question 16

what are the structural changes when someone has asthma

Answer 16

• contractions of muscles in bronchi and bronchioles
• epithelial cells in walls secrete larger volumes of mucus
• Mast cells secrete histamine (makes bronchial linings inflamed and swollen)

Question 17

what are the structural changes when someone has pulmonary tuberculosis (TB) or pulmonary fibrosis

Answer 17

• scar tissue forms in the lungs
• TB caused by bacterial infection in lungs
• fibrosis caused by inhalation of materials that irritate the lungs
• phagocytes are attracted to lungs to engulf bacteria or foreign material, but also destroy lung tissue in alveoli and replace it with thicker, inelastic scar tissue

Question 18

what are the structural changes when someone has emphysema

Answer 18

• breakdown of elastin in alveoli walls due to a chemical found in cigs
• elastin becomes permanently stretched - reduces ability of the lungs to recoil
• alveolar walls become damaged and can burst