Muscles Of Respiration

Question 1

What happens during inspiration?

Answer 1

Contraction

Diaphragm - flattens, extending the superior/inferior dimension of the thoracic a cavity

External intercostal muscles - elevates the ribs and sternum superiorly and anteriorly, extending the anterior/posterior dimensions of the thoracic cavity

Question 2

Define Boyles Law

Answer 2

Volume of gas is inversely proportional to pressure

Example
Volume of thoracic cavity increases - volume of lungs increases = pressure within lungs decreases

Volume of thoracic cavity decreases - volume of lungs decreases = pressure within the lungs increases

Question 3

Does the volume increase in the lungs or decrease as a result of inspiratory muscles?

Answer 3

Increase

Question 4

Does the volume increase in the lungs or decrease as a result of expiratory muscles?

Answer 4

Decrease

Question 5

What is the process of passive expiration?

Answer 5

Relaxation

Diaphragm - relaxes returning to resting position, domes superiorly. Reduces superior/inferior dimension of the thoracic cavity

External intercostal muscles - relax to depress the ribs and sternum. Rescues the anterior/posterior dimensions of the thoracic cavity

Internal intercostals - contract. Pull ribs inferiorly, and pull the sternum inferiorly and posteriorly. Decreasing the anterior/posterior lateral dimensions of the thoracic cavity

Question 6

What is forced breathing?

Answer 6

Active mode of breathing which utilises additional muscles to rapidly expand and contract the thoracic cavity volume e.g. during exercise

Question 7

What is the mode of active inspiration?

Answer 7

Contraction of accessory muscles
(Act to increase volume)

Question 8

What does scalenes muscle do in active inspiration?

Answer 8

Elevates the upper ribs

Question 9

What does sterncleidmastoid muscle do in active inspiration?

Answer 9

Elevates the sternum

Question 10

What does pectoralis major and minor muscle do in active inspiration?

Answer 10

Pull ribs outwards

Question 11

What does serratus anterior muscle do in active inspiration?

Answer 11

Elevates the ribs (when the scapulae are fixed)

Question 12

What does latissimus Doris muscle do in active inspiration?

Answer 12

Elevates the lower ribs

Question 13

What is active expiration?

Answer 13

Utilises the contraction of several thoracic and abdominal muscles
(Act to decrease volume of the thoracic cavity)

Question 14

What does anterolateral abdominal wall do in active expiration?

Answer 14

Increase the intra-abdominal pressure, pushing the diaphragm further upwards into the thoracic cavity

Question 15

What do the internal and innermost intercostal do in active expiration?

Answer 15

Depresses the ribs

Question 16

When does the pressure inside the lung rise?

Answer 16

During the expiration phase of breathing

Question 17

Do muscles contract or relax during expiration?

Answer 17

Relax

Question 18

Do muscles contract or relax during inspiration?

Answer 18

Contract

Question 19

Which nerve provides motor innervation to the diaphragm?

Answer 19

Phrenic

Question 20

What does the scalenes do in active inspiration?

Answer 20

Elevate the upper ribs

Question 21

What does the sternocleidomastoid do during active inspiration?

Answer 21

Elevates the sternum

Question 22

What does the pectoralis major and minor do during active inspiration?

Answer 22

Pull the ribs outwards

Question 23

What does the serratus anterior do during active inspiration?

Answer 23

Elevates the ribs (when the scapulae are fixed)

Question 24

What does the latissimus dorsi do during active inspiration?

Answer 24

Elevates the lower ribs

Question 25

What does the anterolateral abdominal wall do during active expiration?

Answer 25

Increase the intra-abdominal pressure, pushing the diaphragm further upwards into the thoracic cavity

Question 26

What does the internal intercostal do during active expiration?

Answer 26

Depresses the ribs

Question 27

What does the innermost intercostal do during active expiration?

Answer 27

Depresses the ribs

Question 28

What are the muscles of active expiration

Answer 28

Anterolateral abdominal wall Internal intercostal Innermost intercostal

Question 29

What are the muscles of active inspiration?

Answer 29

Scalenes Sternocleidomastoid Pectoralis major and minor Serratus anterior Latissimus dorsi

Question 30

What type of muscle and shape is the diaphragm

Answer 30

Broad, thin, domed sheet of skeletal muscle

Question 31

What does the diaphragm separate

Answer 31

Thoracic and abdominal cavities

Question 32

What is the superior (thoracic) surface adjacent to

Answer 32

Parietal pleura

Question 33

What do apertures in the diaphragm allow

Answer 33

Passage of structures between the abdomen and thorax (e.g. the aorta, inferior vena cava and oesophagus)

Question 34

What is the function of the diaphragm

Answer 34

Mechanics of breathing (ventilation)

Question 35

Where is the diaphragm attached

Answer 35

Xiphoid process Costal margin (and to the tips of the 11th and 12th ribs) Lumbar vertebrae

Question 36

What is the central part of the diaphragm

Answer 36

Not muscular Fibrosis = central tendon

Question 37

What innervates the left and right sides of the diaphragm

Answer 37

Left and right phrenic nerves Somatic nerves Formed in the neck by fibres from the C3, C4 and C5 spinal nerves Motor and sensory fibres

Question 38

What are the 5 key principles of the mechanics of breathing

Answer 38

Muscles move the thoracic cage and change the dimensions of the thoracic cavity Dimensions of the thoracic cavity determine the intrathoracic volume Changes in intrathoracic volume alter intrathoracic pressure Pressure changes inside the thorax drive inspiration and expiration Different muscles are involved in normal, vigorous and forced ventilation

Question 39

During ventilation what are the three planes that the dimensions the thoracic cavity changes in

Answer 39

Vertically - due to contraction and relaxation of the diaphragm Laterally - due to the contraction of the intercostal muscles which move the ribs Antero-posteriorly (AP) - due to the movement of the sternum secondary to the movement of the ribs

Question 40

What is the role of the pleural fluid

Answer 40

Creates surface tension between the pleura lining the thoracic cavity and the visceral pleura on the surface of the lungs

Question 41

What does surface tension caused by the pleural fluid do

Answer 41

Keeps the lungs and thoracic wall together Between the two pleural membranes keeps them in contact with each other - prevents the lung from collapsing away from the thoracic wall

Question 42

In normal (quiet breathing) what is active and passive

Answer 42

Inspiration is active (mainly driven by diaphragm) Expiration is passive

Question 43

In vigorous breathing (exercise) what muscles become important

Answer 43

Intercostal muscles

Question 44

What muscles do active expiration use

Answer 44

Internal intercostal muscles

Question 45

In vigorous or forced breathing (e.g. exacerbation of asthma) what muscles contribute

Answer 45

Accessory muscles

Question 46

What are the accessory muscles

Answer 46

Sternocleidomastoid Pec major Pec minor Serratus anterior

Question 47

What is involved in inspiration

Answer 47

Diaphragm contracts External intercostals

Question 48

What is involved in expiration - passive

Answer 48

Diaphragm relaxes External intercostals relax

Question 49

What are the muscles of active inspiration

Answer 49

Scalenes Sternocleidomastoid Pectoralis major and minor Serratus anterior Latissimus dorsi

Question 50

What are the muscles of active expiration

Answer 50

Anterolateral abdominal wall Internal intercostals Innermost intercostals