Intro to Pulmonary

Question 1

Structure of the lungs

Answer 1

Right: 3 lobes

Left: 2 lobes

Both have 10 segments, and middle right lobe has corresponding 4+5 segment on left upper lobe

Question 2

Pores of Kohn

Answer 2

Fenestrations between alveoli

Question 3

Channels of Lambert

Answer 3

Connection between small bronchioles and alveoli

Question 4

Channels of Martin

Answer 4

Between bronchioles

Question 5

How do alveoli form during development?

Answer 5

Septation

Complete by age 8, then grow

Retinoic acid can induce septation, but not much use in older people with emphysema because septation finished

Question 6

What is the resistance in the pulmonary blood vessels?

Answer 6

Very low resistance in pulmonary blood vessels (1/6 of aorta) in order to get lower pressure in lungs (the lungs can’t stand the high pressure that the body can!)

Also can lower resistance by recruiting more capillaries and putting them in parallel during exercise

P = RQ

Question 7

Alveolar-capillary membrane

Answer 7

Air of alveoli –> alveoli epithelium –> basement membranes of alveoli and capillary are FUSED! –> capillary endothelium –> lumen of capillary

(Normally, when you’re not at alveolar-capillary membrane, have two separate basement membranes with space in between)

Question 8

Type I alveolar epithelial cells

Answer 8

Squamous

Broad, flat, 0.1um thick

93% of alveolar lining membrane

Cannot divide

Question 9

Type II alveolar epithelial cells

Answer 9

Cuboidal

Have microvilli

Located at septal junctions

Secrete surfactant

Can transform into Type 1 cells (responsible for growth and repair)

Question 10

Type III alveolar brush cells

Answer 10

Cone shaped cells

Dense microvilli

Rare, found in central part of acinus

Unknown function, maybe chemoreceptor

Question 11

Alveolar macrophages

Answer 11

Arrive via blood as monocytes

Lie within alveolar lining fluid

Have destructive enzymes to combat infection and scavenge foreign bodies (dust)

Function is impaired by tobacco smoke

Question 12

Clara cells

Answer 12

Non-ciliated

Reside in bronchioles

Contribute to surfactant production

Contain CYP 450 isoenzymes

Question 13

Mast cells

Answer 13

Located in sub-pleural area

Secrete heparin, histamine, other mediators

Question 14

Interstitial cells

Answer 14

Fibroblasts (produce collagen and elastin), myocytes, dendritic cells, neurons (in walls of airways)

Question 15

Non-respiratory functions of the respiratory system

Answer 15

Filtration of particles

Filtration and dissolution of thrombi (microemboli)

Anti-protease

Hormonal (angiotensin I to angiotensin II)

Lipid metabolism (make surfactant)

Acid/base regulation

Immunological protection

Phonation (talking)

Neurotransmitter removal, paracrine removal, histamine release, antioxidase production

Question 16

Airway zones and generations

Answer 16

Conduction, transitional, respiratory zones

Trachea

Main (primary) bronchi (R and L)

Lobar (secondary) bronchi

Segmental (tertiary) bronchi

Bronchioles

Terminal bronchioles

Respiratory bronchioles (alveoli bud off)

Alveolar ducts

Alveolar sacs

Question 17

What happens when you get to generation 16 (end of conducting zone?

Answer 17

Bulk flow drives air until generation 16, then cross-sectional area gets huge and diffusion is now mechanism of ventilation

Question 18

Function of conducting zone

Answer 18

Humidify, warm, clean, conduct air to respiratory zone

Cilia (until 12th generation) beat to propel mucous viscous layer that captured dust upward –> irritant reflexes in upper airway trigger cough

Question 19

Which chemoreceptors are used by the lungs?

Answer 19

Peripheral chemoreceptors in carotid body (NOT aortic arch)

Glossopharyngeal nerve (CN IX) is nerve from carotid bodies, and goes to brainstem

At similar level as CN IX comes into brain, have central chemoreceptors

Sense blood draining lungs

Question 20

What causes negative intrapleural pressure?

Answer 20

Opposing elastic recoil properties of lung and chest wall

Lung wants to collapse and chest wall wants to expand

Note: at 55% VC, chest wall at equilibruim, so past this, chest wall actually wants to collapse too

Question 21

Functional residual capacity (FRC)

Answer 21

Lung volume at rest/equilibrium when recoil forces of lung and chest wall are equal and opposite

FRC increases if lungs decrease recoil

FRC decreases if lungs increase recoil

Question 22

Inspiration

Answer 22

1) Respiratory muscle force expands ribcage
2) Pleural space is virtual, so lung expands
3) Lungs increase elastic recoil
4) Pleural pressure becomes more negative
5) Volume increases so alveolar pressure falls
6) Air flows into lung

Question 23

Expiration

Answer 23

PASSIVE PROCESS

1) Respiratory muscles relax
2) Lung elastic recoil pulls ribcage inward
3) Pleural pressure becomes less negative
4) Volume decreases so alveolar pressure rises
5) Air flows out of lung

Question 24

Compliance vs. Elastance

Answer 24

Compliance: distensibility; how accommodating; change in voulme per unit distending pressure; V/P

Elastance: stiffness; P/V

Opposites!!

Question 25

Surfactant

Answer 25

Reduces surface tension in alveoli by breaking up the attractive forces of water lining alveoli Lipoprotein material (dipalmitoyl phosphatidylcholine; dipalmitol lecithin) Synthesized in Type II alveolar cells

Question 26

Advantages of surfactant

Answer 26

1) Reduces surface tension/lung recoil and increases compliance 2) Counters tendency for smaller alveoli to empy into larger ones 3) Prevents trasudation of fluid into alveoli from pulmonary capillaries

Question 27

Lung compliance

Answer 27

Lungs are not compliant at first because have to get past point where you've broken up intermolecular forces and they're strongest when alveoli are small and molecules are densely packed Low compliance on the curve is where surface area is increasing faster than surfactant can be added to liquid layer so hard to break up forces. After enough surfactant added, lung is more compliant the rest of the way up

Question 28

What does gravity do to regional ventilation?

Answer 28

Top/apex of lung: pleural pressure LESS, -5; alveoli larger so don't expand as much because don't have as far to go Bottom/base of lung: pleural pressure MORE, -1; alveoli smaller expand more (on steep part of compliance curve too) More ventilation goes to bottom of the lung