Ch 37 Pulmonary Ventilation

Question 1

What are the muscles of inspiration?

Answer 1

1. External intercostals
2. Sternocleidomastoid (lift up sternum)
3. Anterior serrati (lifts ribs)
4. Scaleni (lift first two ribs)
   (5) Diaphragm

Question 2

What are the muscles of expiration?

Answer 2

1. Abdominal recti
2. Internal intercostals

Question 3

What is transpulmonary pressure?

Answer 3

The difference between alveolar pressure and the pleural pressure.
*A measure of elastic forces in the lungs that pull toward lung collapse (Recoil pressure)

Question 4

What is lung compliance? What components comprise it?

Answer 4

The extent to which the lungs will expand for each unit increase in transpulmonary pressure.
Comprised by:
1. Elastic forces of the lung tissue (makes up 1/3 of total elasticity)
2. Elastic forces from surface tension of the fluid lining the inside walls of the alveoli (makes up 2/3 of lung elasticity)

Question 5

What tissue types determine lung compliance?

Answer 5

Elastin and collagen.

Question 6

Briefly, how does surfactant reduce surface tension on the alveolar surface?

Answer 6

Because the phospholipids do not dissolve uniformly in the fluid lining the alveolar surface.
Bonus: also made of surfactant apoproteins and calcium in addition to these phospholipids

Question 7

What are the three types of ‘work’ that are required, together, for inspiration to occur?

Answer 7

1. Compliance/elastic work: must overcome lung/chest elastic forces
2. Tissue resistance work: required to overcome viscosity of lung and chest structures
3. Airway resistance work: required to overcome airway resistance

Question 8

Define the following: Tidal volume, inspiratory reserve volume, expiratory reserve volume, residual volume

Answer 8

Tidal: vol insp/expired with each breath
IRV: EXTRA volume you can inspire when inspiring with full force
ERV: Max EXTRA vol of air you can expire when expiring with full force
Residual: vol of air remaining in the lungs after the most forceful contraction

Question 9

What is minute respiratory volume?

Answer 9

The total amount of NEW air moved into the respiratory passages each minute.
MRV = Tidal volume x respiratory rate

Question 10

What is dead space air? What is anatomic vs physiologic dead space?

Answer 10

Air not useful for gas exchange because it’s never at the alveoli.
Physio DS: Air within nonfunctional alveoli
Anatomic DS: Air within all respiratory spaces BESIDES alveoli

Question 11

How is alveolar ventilation measured? (aka what components comprise it?)

Answer 11

Resp rate x amount of new air entering alveoli with each breath (which is tidal volume minus physiologic dead space volume)

Question 12

What keeps bronchioles from collapsing?

Answer 12

They lack cartilage, so they’re kept open by transpulmonary pressures.

Question 13

Why and in what ways do the smaller bronchioles play a significant role in determining airflow in disease conditions?

Answer 13

-smaller size
-easily occluded by:
1. smooth muscle contractions in their walls
2. edema in their walls
3. mucus collecting in their lumens

Question 14

How does the autonomic nervous system influence bronchiolar tree diameter?

Answer 14

Sympathetic:
poorly innervated, but they have beta-2 adrenergic receptors, which are VERY sensitive to epinephrine and to a lesser extent, norEpi . DILATED by epi/norEpi

Parasympathetic: A few PSNS nerves from the vagus innervate lung. Acetylcholine secreted causes mild-moderate bronchiolar constriction. This is why giving atropine, which blocks ACh, can relax resp passages.
-PSNS reflexes are also activated by irritations and infection

Question 15

How do histamine and slow reactive substance of anaphylaxis influence bronchiolar diameter?

Answer 15

Both are released by mast cells during allergic reactions and cause bronchiolar constriction

Question 16

How does cilia function differ in the upper vs lower airway passaged?

Answer 16

In the sinuses/nose, cilia beat their power stroke downward to push down mucus trapping particles
In lower airways and trachea, the cilia beat upward to push mucus toward the pharynx to cough out or swallow

Question 17

Which cranial nerve carries afferent stimuli from the airways to the medulla for the
1. Cough reflex
2. Sneeze reflex?

Answer 17

Cough: vagus CN X
Sneeze: Trigeminal CN V

Question 18

How are particles filtered from the nose?

Answer 18

Turbulent precipitation

Question 19

In which airways does the most airway resistance occur?

Answer 19

The intermediate-sized bronchi.
Also resistance is highest at the dependent-most part of the lungs

Question 20

Which airways have the least (but still have) smooth muscle?

Answer 20

Respiratory bronchioles (few fibers)