L14 Respiratory Physiology

Question 1

What are the functions of the respiratory system?

Answer 1

1) exchange of gases : atmosphere - blood and blood - tissues
2) regulation of body pH : retaining or removing CO2
3) protection from inhaled pathogens and irritants : epithelial cells and mucus trap and destroy substances before they can enter the body
4) vocalisation - movement of air across vocal cords for speech

Question 2

What are the conduction systems in the RS?

Answer 2

Upper respiratory tract - nasal cavity, pharynx, larynx
Lower respiratory tract - trachea, bronchi, bronchioles

Question 3

What is the respiratory zone comprised of?

Answer 3

Alveoli and capillary supply

Question 4

Outline the nose and nasal cavity

Answer 4

• entryway into the respiratory system
• inhaled air is warmed and humidified
• filters debris from inhaled air
• secretes antibacterial substances
• houses olfactory receptors for smell
• enhances resonance for voice

Question 5

Outline the pharynx (throat)

Answer 5

• warm, humidify and filter inspired air
• soft palate component moves posteriorly during swallowing to prevent food from entering nasopharynx and nasal cavity
• protects against mechanical stress (air and food)

Question 6

Outline the larynx

Answer 6

• prevents food and liquids entering the respiratory tract
• sound production as vocal cords crate sound as air passes over them

Question 7

Outline the structure of the lower respiratory tract - the bronchial tree

Answer 7

Larynx, trachea, bronchus, bronchiole, alveoli
The trachea branches into two primary bronchi
- 5 secondary bronchi, feeding lobes
- 18 tertiary bronchi, feeding lung segments
- continue to divide into smaller bronchi
- divide into bronchioles
- terminal division into a cluster of alveoli

Question 8

What are the larynx, trachea and primary bronchi lined with?

Answer 8

Lined by ciliated respiratory epithelial cell layer

Question 9

Define globlet cells

Answer 9

Secrete mucus to form continuous mucus layer over the surface of the respiratory tract

Question 10

Define ciliated cells

Answer 10

Produce saline and sweep mucus upwards to the pharynx

Question 11

Define mucociliary escalator

Answer 11

Removes noxious particles from lungs

Question 12

Outline the saline secretion pathway

Answer 12

1) NKCC brings chloride ions into epithelial cells from the ECF
2) Apical anion channels including CFTR, allow chloride ions to enter the lumen
3) Sodium ions goes from ECF to lumen by the paracellular pathway, drawn by the electrochemical gradient
4) NaCl movement from ECF to the lumen creates a concentration gradient so water follows into the lumen

Question 13

Why does cystic fibrosis occur?

Answer 13

There is a defect in CFTR channel resulting in a decreased fluid component of mucus
This results in thick, sticky mucus layer which cannot be cleared
Bacteria can colonise causing recurrent lung infections

Question 14

What’s the role of c-shaped cartilage rings?

Answer 14

They support the lower conduction system
They keep the trachea open and are flexible enough to allow the trachea to change in diameter during pulmonary ventilation

Question 15

What is the posterior surface of the trachea covered with?

Answer 15

Elastic connective tissue and smooth muscle which allows the oesophagus to expand during swallowing

Question 16

What changes occur when the bronchi divide into bronchioles?

Answer 16

1) cartilage changes to complete rings, to progressively fewer, irregular plates
2) epithelium gradually changes to columnar cells in smaller bronchi
3) amount of smooth muscle increases
These changes allow tiny airways to change diameter to control air flow in bronchioles and alveoli

Question 17

Describe bronchioles

Answer 17

Non-ciliated epithelium, smooth muscle layer and no cartilage

Question 18

What do each respiratory bronchiole branch into?

Answer 18

Branch into two or more alveolar ducts
Alveolar ducts end in alveolar sacs

Question 19

What are alveolar sacs?

Answer 19

Grapelike clusters of alveoli which are surrounded by elastic fibres and a network of capillaries

Question 20

Outline the structure of the vascular system in the respiratory zone

Answer 20

• extensive capillary network which provides large surface area for gas exchange
• pulmonary artery supplies deoxygenated blood
• pulmonary vein carries oxygenation blood

Question 21

Describe the structure of alveoli in the respiratory zone

Answer 21

• single epithelial cell layer
• supported by elastic fibres
• large surface area for gas exchange

Question 22

What does the mechanisms of ventilation involve?

Answer 22

The diaphragm
Respiratory muscles
Pressure changes

Question 23

What happens to the diaphragm during breathing?

Answer 23

Inhalation : active contraction
Expiration : passive relaxation

Question 24

What happens to the respiratory muscles during forced breathing?

Answer 24

Internal intercostals are active and accessory muscles play a role

Question 25

What happens to respiratory muscles during expiration?

Answer 25

External intercostal muscles and scalenes raise rib cage upwards and outwards

Question 26

What happens to the thoracic volume during breathing?

Answer 26

Movement of the thoracic cage and diaphragm Inspiration : increased Expiration : decreased

Question 27

Describe the Boyle’s law

Answer 27

Describes the relationship between pressure and volume States that at constant temperature and number of gas molecules, pressure and volume of gas are inversely related

Question 28

Explain how pressure and volume are inversely related?

Answer 28

As volume of container increases, the pressure that the gas exerts on the container decreases As volume of container decreases, the pressure that the gas exerts on the container increases

Question 29

What is the process of pulmonary ventilation?

Answer 29

Involved volume changes in thoracic cavity and lungs that lead to creation of a pressure gradient The gradient causes air to move in to or out of lungs

Question 30

Which pressure gradients influence ventilation?

Answer 30

1) atmospheric pressure 2) intrapulmonary pressure 3) intrapleural pressure

Question 31

How is atmospheric pressure created?

Answer 31

- created by a pull of gravity on air around us

Question 32

How is intrapulmonary pressure created?

Answer 32

- air pressure within alveoli rises and falls with inspiration and expiration - eventually equalises with atmospheric pressure due to pressure gradients reaching equilibrium

Question 33

How is intrapleural pressure created?

Answer 33

The pressure found within pleural cavity which rises and falls with breathing Does not equalise with atmospheric pressure

Question 34

How is a pleural sac formed?

Answer 34

Each lung is fond within a pleural sac - formed by two membranes of elastic connective tissue and capillaries

Question 35

What is the parietal pleura?

Answer 35

The outer layer of the serous membrane which is fused to the rib cage, diaphragm and other local structures

Question 36

What happens to the parietal pleura at the hilam?

Answer 36

It turns over on itself to create visceral pleura which is the inner layer of the membrane and is continuous with the surface of the lungs

Question 37

What is the role of pleural fluid?

Answer 37

It is a very thin film of fluid in the cavity - acts as a lubricant to allow lungs to move within the thorax to maintain lung inflation at rest - keeps lung and chest wall together

Question 38

Why is intrapleural pressure less than atmospheric pressure in the pleural cavity?

Answer 38

Because the lungs and chest wall pull away from each other -> elastic recoil

Question 39

Why does intrapleural pressure vary along the lung?

Answer 39

Due to gravity During the respiratory cycle

Question 40

Define elasticity

Answer 40

The ability of tissue to return to its original state when stretched

Question 41

What pull does elastic recoil cause for lungs and chest wall?

Answer 41

Lung : inward pull Chest wall : outward pull

Question 42

What happens during inspiration?

Answer 42

- inspiratory muscles contract - thoracic volume increases - lung volume increases - intrapulmonary pressure decreases to below atmospheric pressure - air flows into lungs

Question 43

What happens during expiration?

Answer 43

- inspiratory muscles relax - thoracic volume decreases due to elastic recoil - lung volume decreases - intrapulmonary pressure increases to above atmospheric pressure - air flows out of lungs

Question 44

What happens in between breaths?

Answer 44

Intrapulmonary pressure equals atmospheric pressure