Lecture 16- Anatomy of the thorax and breathing

Question 1

Which of these is not associated with the respiratory
membrane?
A. Capillary endothelium
B. Simple squamous epithelium
C. Type 1 pneumocytes
D. Type 2 pneumocytes
E. Fused basement membrane

Answer 1

D. Type 2 pneumocytes

Question 2

Which cells remove debris from the alveoli?
A. Pseudostratified ciliated columnar epithelium
B. Goblet cells
C. Type 1 pneumocytes
D. Type 2 pneumocytes
E. Macrophages

Answer 2

E. Macrophages

Question 3

What are all our body cavities lined with?

Answer 3

• Serous membranes
• Is a double layer of secretory tissue with fluid between layers to allow for the smooth movement of the organs contained within it (lubricant)
• The visceral layer is on the organ (inside)
• The parietal layer on body wall (outer)

Question 4

What are the two body cavities?

Answer 4

• Thoracic cavity

- Abdominopelvic cavity

Question 5

What are the two serous membranes contained in the thoracic cavity?

Answer 5

• Pericardium (around heart)

- Pleura (around each lung)

Question 6

What is the Mediastinum?

Answer 6

Within the thoracic cavity. Takes up the middle region and include the heart, vessels and pericardium.

Question 7

What are the boundaries of the thoracic cavity?

Answer 7

• Anterior: Sternum
• Posterior: Thoracic vertebrae
• Lateral: Ribs
• Superior: base of neck
• Inferior: diaphragm (only one that is not a bone)

Question 8

Why are the lungs in two separate pleural cavities?

Answer 8

Independent, if one stops functioning, you have another

Question 9

What is the relationship between pressure and volume in the lungs?

Answer 9

• Pressure is inversely proportional to volume in a relationship called Boyle’s law P=1/V
• If change one the other will change

Question 10

How is pressure measured in the lungs?

Answer 10

By collisions:

• smaller space = more collisions = increased pressure
• bigger space = less collisions = decreased pressure

Question 11

How do pressure changes drive ventilation?

Answer 11

To breathe, we need to establish a pressure gradient to make air move…
-Between breaths- pressure inside cavity = pressure
outside. No gradient therefore no movement
-Increase volume (therefore decrease pressure) – air
flows in= inhalation
-Decrease volume (therefore increase pressure) - air flows out= exhalation

Question 12

What are alternative names of exhalation and inhalation and what happens to the volume of the thorax (one word answer)?

Answer 12

• Inhalation= Inspiration: volume increases

- Exhalation= Expiration: volume decreases

Question 13

Where will air move?

Answer 13

To the lower pressure space

Question 14

What are the names of the anterior thoracic joints? Where are the located?

Answer 14

-Sternocostal: Connect cartilage to the sternum
Synovial, Except 1st = cartilaginous
-Costochondral: Connect ribs to cartilage. Cartilaginous
-Interchondral: connect different parts of cartilage. Synovial

Question 15

Do the ribs connect directly to the sternum?

Answer 15

No instead there is a band of hyaline cartilage

Question 16

Why are there differences in the types of joints making up the thoracic cage?

Answer 16

• Cartilaginous is when a bit more stability is needed

- Synovial is when more movement is wanted

Question 17

What are the names of the posterior thoracic joints? Where are the located?

Answer 17

In general articulate the thoracic vertebrae and the ribs
-Costotransverse: between rib and transverse
process of vertebrae
-Costovertebral between rib and body of vertebrae

Question 18

What joint type are the posterior thoracic joints?

Answer 18

All synovial (want a bit of movement)

Question 19

Which of the thoracic joints are NOT synovial joints?

Answer 19

-Costochondral (between cartilage and ribs)
-Also the 1st of the sternocostal.
Why? Because they require a bit more stability

Question 20

What is the general role of respiratory muscles?

Answer 20

• Pull on the bones to create movement

- Move the rib cage to allow us to breathe

Question 21

What are the two primary inspiratory

muscles?

Answer 21

• Diaphragm

- Intercostals (muscles between ribs)

Question 22

What are accessory muscles in respiration?

Answer 22

-Several muscles that attach to the thoracic
cage and are active only when needed
-Some accessory muscles increase cavity volume for
forced inspiration. Other accessory muscles decrease cavity volume for forced expiration

Question 23

What is the diaphragm and how does it differ when contracted as opposed to relaxed?

Answer 23

-Is a sheet of skeletal muscle that separates the thorax from the abdomen
-When relaxed is dome-shaped
-When contracted it flattens expanding the thoracic
cavity (and compressing abdominopelvic cavity)

Question 24

What are the intercostal muscles and how do they differ when contracted as opposed to relaxed?

Answer 24

-Attach diagonally between neighbouring ribs a made of 2 bands of muscle
-External intercostals when contracted lift ribcage and
expand the cavity resulting in inspiration- quiet and
forced
-Internal intercostals when contracted depress ribcage and decrease cavity resulting in expiration- forced only

Question 25

What happens to respiratory muscles in inspiration? How does this differ between quiet and forced inhalation?

Answer 25

During normal ‘quiet’ inspiration:

• Diaphragm contracts = flattens
• External intercostals contract = lifts ribs

During active ‘forced’ inspiration:
-As above, plus accessory muscles contract to further
expand thoracic cavity

Question 26

What happens to respiratory muscles in expiration? How does this differ between quiet and forced exhalation?

Answer 26

During normal ‘quiet’ expiration:

• Passive process
• Diaphragm relaxes = dome shaped
• External intercostals relax = ribs no longer lifted

During active ‘forced’ expiration:
-As above plus:
-Internal intercostals contract = depress ribs
-Accessory muscles contract to further decrease cavity
volume

Question 27

How do the lungs expand as the cavity does?

Answer 27

-Lung tissue is elastic and always trying to recoil
-Therefore the pleura make the lungs ‘stick’ to the
thoracic wall
-Lungs expand during inspiration
-Lungs decrease during expiration

Question 28

What is the chain of events that occurs after there is an increase in volume of the thorax?

Answer 28

Increase volume of thorax means increase volume of lung means decrease pressure in lung means air flows in