Humans

Question 1

Pleural membranes

Answer 1

Line thorax and cover lung. Fluid in cavity acts as lubricant and reduces friction between lungs and chest cavity

Question 2

Diaphragm

Answer 2

Muscle that separates thorax form abdomen

Alters size of thoracic cavity so changes pressure and volume

Question 3

Intercostal muscles

Answer 3

Between the ribs and enlarge the thorax so cause pressure and volume changes

Question 4

Epiglottis

Answer 4

Covers opening to trachea when swallowing

Question 5

Goblet cells

Answer 5

Secrete mucus to trap dust, dirt and microbes

- Trachea, bronchi, large bronchioles

Question 6

Ciliated epithelium

Answer 6

• Have cilia
• Waft mucus and bacteria up trachea to be swallowed
• Stomach acid kills bacteria

Question 7

Smooth muscle

Answer 7

• Adjusts size of airways
• Contracts = constriction and restrict air flow as smaller diameter

Question 8

Elastic fibres

Answer 8

• Stretch and elastic recoil of alveoli in respiration
• Expand during inhalation = large SA and recoil to force air out
• Prevents alveoli from bursting
  IN ALVEOLI

Question 9

Cartilage

Answer 9

• Prevents collapse of trachea and trachea closing during inspiration
• Supports and helps keep shape
• C ring and not full ring to allow oesophagus to expand and increase in size due to passage of food, so it allows peristalsis

Question 10

Advantages of internal gas exchange surfaces

Answer 10

Minimises heat and water loss and lungs protected by ribs

Question 11

Inspiration

Answer 11

• Intercostal muscles contract and ribs move upwards and outwards
• Outer pleural membrane moves up and out and surface tension pulls on inner memb which moves outwards (pulls on lung and alveoli expand)
• Diaphragm contract and flattens
• Volume increases and pressure in thorax decreases below atmospheric
• Higher pressure outside draws air into lungs, down gradient

Question 12

Expiration

Answer 12

• Intercostal muscles relax, ribcage moves downwards and inwards
• Diaphragm relaxes
• Decreases the volume of the thorax = increases the pressure inside the lungs
• Forcing the air out down pressure gradient

Question 13

Forced Expiration

Answer 13

• Singing and exercising
• Internal intercostal muscles contract, pulling the ribcage downwards and inwards
• Abdominal muscles contract to push diaphragm up and it becomes dome-shaped
• Volume of thorax decreases ad pressure inside the lungs increases
• Forcing the air out of lungs down pressure gradient

Question 14

Alveoli features

Answer 14

• Thin alveolar and capillary walls = shorter diffusion distance
• Large SA (many alveoli)
• Large no of blood capillaries = circulation maintains steep concentration gradient
• Capillaries close to alveoli = short diffusion distance
• Moist lining/ layer for gases to dissolve in
• Ventilation mechanism- fresh air to maintain gradient
• Lined with surfactant to reduces surface tension and prevents collapse during expiration

Question 15

Gas exchange (O2 and CO2 at alveoli)

Answer 15

• Deoxygenated blood from pulmonary artery enters capillaries
• O2 diffuses out of air in alveoli into the capillaries into RBCs
• CO2 diffuses out of plasma in capillary to the air in alveoli. Exhaled