respiratory physiology

Question 1

respiratory muscles

Answer 1

Diaphragm major inspiratory, dome-shaped skeletal muscle.

Other respiratory skeletal muscles active during more strenuous breathing.

Question 2

quiet breathing

Answer 2

inspiration- active
Diaphragm contracts downwards pushing abdominal contents outwards.
External intercostals pull ribs outwards and upwards.
expiration- passive
elastic recoil

Question 3

strenuous breathing, inspiration- active

Answer 3

inspiration- active
Greater contraction of diaphragm (1cm quiet breathing up to 10cm during strenuous breathing) and external intercostals.
Inspiratory accessory muscles active, e.g., sternocleidomastoid, alae nasi, genioglossus.

Question 4

strenuous breathing, expiration-active

Answer 4

Abdominal muscles (rectus abdominus, internal oblique, external oblique and transversus abdominus).
Internal intercostal muscles oppose external intercostals by pushing ribs down and inwards.

Question 5

nasal cavities, paranasal sinuses

Answer 5

• filter, warm, humidfy air, detect smells

Question 6

pharynx

Answer 6

conducts air to larynx, a chamber with the digestive tract

Question 7

larynx

Answer 7

protects opening to trachea and contains vocal chords

Question 8

trachea and bronchi

Answer 8

• filters air, traps particles in mucus, cartilages keep airway open

Question 9

lungs

Answer 9

responsible for air movement through volume changes during movement of ribs and diaphragm, include airways and alveoli

Question 10

alveoli

Answer 10

acts as sites of gas exchnage between air and blood

Question 11

filtering air

Answer 11

Upper airways to bronchioles
lined by pseudo-stratified, ciliated, columnar epithelium.

Inhaled particles stick to mucus. Mucus moved towards mouth by beating cilia.

Question 12

cough reflex

Answer 12

Cough is protective reflex - rids airway of offending material.

Rapidly adapting pulmonary stretch receptors (RARs) are found in epithelium of respiratory tract.

RARs activated by dust, smoke, ammonia, oedema etc.

RARs afferents of vagus nerve.

Question 13

cough reflex

Answer 13

• Stimulation of RARs by irritant.
  – Afferent information sent via vagus nerve to brain.
  – Brain sends information to diaphragm & external intercostals to induce strong contraction.
  – air rushes into lungs.
  – abdominal muscles
  contract to induce expiration.
  – glottis opens to
  forcefully release air and
  irritants.

Question 14

respiratory tree

Answer 14

Airways branch into smaller and more numerous bronchioles until terminating in a group of alveoli.
Each division results in an increase in number, a decrease in diameter and an increase in surface area.

Question 15

respiratory tree- conducting airways

Answer 15

Do not participate in gas exchange.

Form anatomic dead space.

Bronchi containing cartilage and nonrespiratory bronchioles.

Conducting airways 150mls in volume (30% of average breath).

Question 16

respiratory tree- respiratory airways

Answer 16

bronchioles with alveoli where gas exchange occurs (from terminal bronchioles to alveoli).

The region is ~5mm long.

~2500ml volume.

Question 17

type 1 and 2 epithelial cells

Answer 17

type 1- occupy 97% of surface area of alveoli. Primary site of gas exchange.

type 2- occupy 3%
surface area.
Produce pulmonary
surfactant (reduces
surface tension).

Alveolar macrophages:
removal of debris.

Question 18

alveoli function

Answer 18

Alveoli perfectly designed for gas exchange:
- Large surface area: ~100m2
- Very thin walls (mean 0.5m)
- Good diffusion characteristics

Question 19

blood circulation

Answer 19

Pulmonary circulation: brings deoxygenated blood from heart to lung and oxygenated blood from lung to heart and then rest of body.

Bronchial circulation:
brings oxygenated
blood to lung
parenchyma.

Lymphatic system:defence and removal
of lymph fluid.

Question 20

pulmonary circulation

Answer 20

Total blood volume in pulmonary circulation = 500mls (10% total).

At rest - 75mls blood in alveolar-capillary network.
Exercise – increases to 150-200mls due to recruitment of new capillaries secondary to an increase in pressure and flow.

Arteries: thin walled,
highly compliant,
larger diameter,
low resistance
(compared to
systemic circulation).

Question 21

alveolar- capillary network

Answer 21

Gas exchange occurs through dense mesh-like network of capillaries and alveoli.

Distance between alveoli and red blood cell 1-2µm:
Type 1 alveolar epithelial cell, capillary endothelial cell and basement membrane.

Gas exchange occurs through dense mesh-like network of capillaries and alveoli.

Distance between alveoli and red blood cell 1-2µm:
Type 1 alveolar epithelial cell, capillary endothelial cell and basement membrane.

Question 22

gas gradients

Answer 22

Gases move down their pressure gradients.

Pulmonary circuit: O2 enters blood, CO2 leaves

Systemic circuit: O2 leaves blood, CO2 enters.

Question 23

gas concentration gradients

Answer 23

Similar volumes of CO2 and O2 move each minute.

Pressure gradient for O2 is much bigger than for CO2.

CO2 is more diffusible.

Question 24

pulmonary and systemic capillary

Answer 24

Pulmonary Capillary
Alveolar Air Venous Blood
PO2 100 —-> 40 mmHg
PCO2 40 <—— 46mmHg

Systemic capillary
Tissues Arterial Blood
PO2 <40 <——- 100 mmHg
PCO2 >46 ——> 40 mmHg