4.1 Breathing - Structure and Regulation

Question 1

What is the difference between internal and external respiration?

Answer 1

Internal = oxidative breakdown of foodstuff to produce energy, requires O2 and produces O2

External = intake of O2 from the atmosphere for internal respiration and expulsion of CO2 into atmosphere

Question 2

The human respiratory tract is made up of the upper and lower airways. What are the structure and function of these two parts?

Answer 2

Upper = nasal cavity, pharynx, larynx
Function = Filters, warms, and humidifies air

Lower = trachea, bronchi, bronchioles, lung + alveoli
Function = gas exchange + protection

Question 3

The nasal septum + conchae make up the nasal cavity. What are the characteristics of the nasal mucosa?

Answer 3

Ciliated epithelium

Goblet cells (mucous secreting cells)

Olfactory cells

Question 4

The pharynx has three segments important for breathing and swallowing. What are they?

Answer 4

1. Nasopharynx
2. Oropharynx
3. Laryngopharynx

Question 5

The larynx pulls air through the lower airway and is essential. What is the larynx?

Answer 5

Cartilage + muscular structure
Crucial for breathing + sound generation

Used in critical care = tracheal intubation + surgical airway

Question 6

What are the characteristics of the trachea?

Answer 6

10-13 cm long

Connect larynx to bronchial tree

16-20 C-shaped carilages

Ciliated epithelium + goblet cells (sputum)

Question 7

What are the characteristics of the bronchial tree?

Answer 7

Consists of primary bronchus (cartilage) and bronchioles (no cartilage)

Terminates in alveoli

Affected by foriegn body aspiration

Question 8

What is the thin tissue that covers the lungs?

Answer 8

The pleura

Question 9

What are the characteristics of alveoli?

Answer 9

Functional units of the lung

Surrounded by capillaries

Two cell types (gas exchange + surfactant productoin to prevent collapse)

Question 10

What are the functions of the lungs + alveoli?

Answer 10

Making oxygen available to tissues for metabolism

Removing the major by-product of metabolism (CO2)

Question 11

What are the differences between ventilation, diffusion, and perfusion?

Answer 11

Ventilation = movement of air between atmosphere and alveoli + distribution of air within

Diffusion = blood-gas exchange between alveoli and capillaries following concentration gradients (high to low pressure)

Perfusion = movement of blood through pulmonary capillaries (blood flow, ventilation + perfusion = match)

Question 12

What is the mechanism behind ventilation?

Answer 12

Inhalation = active, muscle effort negative pressure in alveoli

Exhalation = passive, relation + release of stored elastic energy (can be forced via abdominal muscles)

Question 13

Diffusion is the movement of O2 and CO2 across the alveolar-capillary membrane. What is the mechanism behind diffusion?

Answer 13

Partial pressure = individual pressure exerted by a particular gas within a mixture of gases

O2 flows downhill from the air through alveoli and blood into tissue

CO2 flows downhill from tissues to the alveoli

Question 14

How is oxygen transported in blood?

Answer 14

Haemoglobin

Question 15

What are the factors that limit oxygen uptake in blood?

Answer 15

1. Diffusion properties (surface area, thickness of membrane)
2. Partial pressure gradient
3. Pulmonary capillary blood flow (changed with cardiac output)
4. Carbon monoxide poisoning (combine with Hb)

Question 16

How is carbon dioxide transported in blood?

Answer 16

Physically dissolved in plasma

Bicarbonate ions and red cells (60%)
Carbamino proteins (30%)

Question 17

What is the importance of plasma acid-base balance in respiration?

Answer 17

Normal pH of arterial plasma = 7.4

Respiratory acidosis (high pH) = hypoventilation

Respiratory alkalosis (low pH) = hyperventilation

Question 18

Chemoreceptors are chemosensitive cells that respond to certain chemical changes in blood. What are the central and peripheral chemoreceptors important for respiration?

Answer 18

Central = medulla

Peripheral = carotid body (most significant) + aortic body

Question 19

How is breathing regulated through nervous control?

Answer 19

1. Decrease O2
2. Peripheral chemoreceptors notice and send signal
3. Medulla activates nervous control (involuntary = central pattern generator, voluntary = higher brain)
4. Increase respiration