Anatomy of Breathing - Lecture 17

Question 1

What are the lungs?

Answer 1

○ Located in thorax
○ Separated by mediastinum and heart
○ Extend from neck to diaphragm
○ Diaphragm separates throacic and abdominal cavities

Question 2

What makes up the lungs?

Answer 2

○ Conical shaped with soft, spongy texture
○ Apex of the lung lies above the clavicle
○ Diaphragmatic surface: sits on the diaphragm
○ Costal surface: lies adjacent to the ribs
○ Mediastinal surface: faces the mediastinum

Question 3

What are the features of the right lung?

Answer 3

○ Wider and shorted than the left lung: liver underneath the diaphragm
○ Three lobes: superior, middle, inferior
○ Two fissures: oblique and horizontal

Question 4

What are the features of the left lung?

Answer 4

○ Narrower and longer than the right lung
○ Two lobes: superior and inferior
○ One fissure: oblique

Question 5

What is the hilum of the lung?

Answer 5

○ Located on the mediastinal surface
○ The area where the pulmonary vessels, bronchi, bronchial vessels, lumpathics and nerves enters/leaves the lung

Question 6

What are the physical properties of the lungs?

Answer 6

○ Compliance: the ability of the lungs to expand
○ Elasticity: elastic tissue allows lung expansion during inspiration and recoil during expiration

Question 7

What factors can affect compliance?

Answer 7

○ Connective tissue structure of the lungs
○ Level of surfactant
○ Mobility of thoracic cage

Question 8

What is the pleura?

Answer 8

Double layered serous membrane

Question 9

What makes up the serous membrane?

Answer 9

○ Visceral pleura: adheres to the lung
○ Parietal pleura: attaches to the thoracic wall and diaphragm
○ Pleural cavity: Thin layer of serous fluid that holds the two layers together

Question 10

What are the functions of the pleura?

Answer 10

○ Reduces friction during breathing
○ Creates a pressure gradient which assists in ventilation
○ Compartmentalises each lung: reduces spread of infection

Question 11

What is the bony thorax and what does it consist of?

Answer 11

○ Forms the skeleton of the chest wall
Consists of:
○ Sternum
○ Ribs (12 pair)
○ Thoracic vertebrae (12)

Question 12

What is the sternum and what does it consist of?

Answer 12

○ Breast bone
Consists of:
○ Manubrium
○ Body
○ Xiphisternum

Question 13

What are the ribs?

Answer 13

○ Attached by the head and tubercle to the thoracic vertebrae
○ Slope downwards and forwards

Question 14

How are the ribs attached?

Answer 14

○ Ribs 1-10 attached by costal cartilage to the sternum:
- 7 pairs true
- 3 pairs false
- 2 floating

Question 15

What is the thoracic vertebrae?

Answer 15

○ Head of rib articulates with the body of the thoracic vertebrae
○ Tubercle of rib articulates with the transverse process of the thoracic vertebra
○ Synovial joints between the ribs and vertebrae to allow movement of ribs

Question 16

What are intercoastal muscles and what does it consist of?

Answer 16

○ Span the spaces between the ribs
○ External intercostal muscles: superficial layer
○ Internal intercostal muscles: middle layer
○ Innermost intercostal muscles: deep layer

Question 17

Which direction does the external intercostal run?

Answer 17

Downwards and fowards

Question 18

Which direction does the internal intercostal run?

Answer 18

Downwards and backwards

Question 19

How is blood and nerves supplied to the intercostal muscles?

Answer 19

○ Nerves and vessels course between the internal intercostal and innermost intercostal muscles
○ Protected by the ribs
○ Supply the muscles, adjacent skin and pleura

Question 20

What are the features of the diaphragm?

Answer 20

○ Separates the thorax from the abdomen
○ Dome-shaped skeletal muscle with a central tendon
○ Attached to the xiphisternum, costal margin, 11th and 12th ribs and the lumbar vertebrae
○ Openings for inferior vena cava, oesophagus & aorta
○ Fibrous pericardium fused to central tendon
○ Innervated by the phrenic nerve

Question 21

When does inspiration occur?

Answer 21

When intrapulmonary pressure is lower than atmospheric pressure

Question 22

When does expiration occur?

Answer 22

When intrapulmonary pressure is greater than atmospheric pressure

Question 23

How is intrapulmonary pressure altered?

Answer 23

Changes in thoracic volume

Question 24

How can thoracic volume be altered?

Answer 24

Changes in:
○ Vertical diamter: top of thorax to diaphragm
○ Anterior posterior (AP) diameter: between sternum and vertebral column
○ Transverse diameter: left and right side of ribcage

Question 25

How is the vertical diameter altered?

Answer 25

○ Increase = contraction of diaphragm
○ Decrease = relaxation of diaphragm
○ Contraction responsible for 75% increase in thoracic capacity during inspiration

Question 26

How is AP and transverse diameters increased?

Answer 26

○ Elevation of the ribs at the sternal makes them more horizontal and pushes sternum forward (pump handle movement)
○ Responsible for 25% increase in thoracic capacity

Question 27

How is transverse diameter increased?

Answer 27

○ Many of the ribs are lowest near their middle and rise at each end
○ If the middle of the rib rises, it moves away from the midline of the body and makes the chest wider
○ Responsible for 25% increase in thoracic capacity

Question 28

What muscles are involved in quiet inspiration?

Answer 28

○ Contraction of diameter
○ External intercostals elevate the ribs

Question 29

How does quiet expiration happen?

Answer 29

○ Passive process
○ Diaphragm and external intercostal muscles relax

Question 30

What muscles are involved in forced inspiration?

Answer 30

○ Sternocleidomastoid: pulls up the manubrium of the sternum and the clavicle and brings them up and fowards which increases AP diameter
○ Scalenes: Holds the 1st and 2nd ribs in place which results in more effective movement of intercostal muscles
○ Serratus anterior: pulls the scapular forward
○ Pectoralis minor: pulls ribs 3-5 out when scapula is pulled
○ Pectoralis major: involved in the movement of the humerus and if humerus is fixed ribs move up and out

Question 31

What muscles are involved in forced expiration?

Answer 31

○ Internal and innermost intercostals depress the ribs and reduce the size of the thoracic cavity
○ Abdominal muscles compress the abdomen and force the diaphragm upwards