Lecture 24 Respiratory 1 Flashcards Preview

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1

Primary functions of respiratory system

supply O2 and eliminate CO2
maintain acid-base balance via regulation of CO2 in blood
ventilation and gas exchange

2

4 integrated processes

1. Ventilation
2. gas exchange
3. transport of O2 and CO2 in the blood
4. exchange of O2 and CO2 between blood and cells

3

Conducting zone

nasal cavity
pharynx
larynx
trachea
primary bronchi
bulk flow region, no gas exchange = anatomic "dead space"

4

Upper respiratory

nasal cavity
pharynx

5

Lungs

secondary, tertiary, and smaller bronchi
bronchioles
terminal bronchioles

6

respiratory zone

respiratory bronchioles
alveolar ducts
alveolar sacs
alveoli
gas exchange region

7

Alveoli

primary sites of gas exchange
huge surface area
type 1 cells - simple squamous
type 2 cells - surfactant cells
alveolar macrophages ("dust cells")

8

Pulmonary Capillaries

surround alveoli, exchange O2 and CO2 with air in the alveoli

9

Thoracic Cavity

chest wall, diaphragm, pleurae, intrapleural space, respiratory muscles

10

Chest wall

surrounds thoracic cavity (ribs, intercostal muscle, etc.)

11

Diaphragm

separates thoracic and abdominal cavities
primary muscle of inspiration

12

Pleurae

serous membranes surround each lung, form fluid-filled pleural sacs
parietal pleura lines chest wall and diaphragm
visceral pleura covers the lungs

13

Intrapleural space

thin, fluid filled space between parietal and visceral pleurae
fluid in the intrapleural space connects lungs to chest wall and diaphragm

14

Inspiration
muscles

primary: diaphragm
secondary: external intercostals, neck muscles

15

Expiration
muscles

passive: elastic recoil of lungs
active: internal intercostals, abdominal muscles

16

Mechanics of air breathing

Pressure
Air flow
Forces

17

Pressure

P of gas is inversely related to volume (V)
Boyle's law P1V1=P2V2 (closed system)
during inspiration, resp. muscles contract -> lungs expand -> V increases -> P decreases

18

Air Flows

in and out of lungs because of pressure differences between lungs and atmosphere
air flows from higher pressure to lower pressure
during inspiration, P decreases -> air flows in
during expiration, P increases -> air flows out

19

Forces

are transmitted between chest wall and lungs through fluid in the intrapleural space
opposing recoil forces of the lungs (inward) and chest wall (outward) create a negative pressure in the intrapleural space

20

Pressures involved in breathing

atmospheric
alveolar
intrapleural space

21

atmospheric

(Patm) = 760 mm Hg at sea level (= "0 mm Hg" used as reference)

22

alveolar

intrapulmonary Palv - air pressure in the alveoli
P alv= P atm (=0) at end of expiration
Palv < Patm during inspiration, Palv>Patm during expiration

23

intrapleural

Pip
pressure inside the intrapleural space = -4 mm Hg (0 lung coppalses (atelectasis)

24

Inspiration pressure changes during breathing

resp. muscles contract -> Pip decreases (< -4 mm Hg) -> V increase -> Palv decreases -> air flows in

25

Expiration changes during breathing

resp. muscles relax -> Pip increases )back to -4 mmHg) -> V decreases -> Palv increases -> air flows out

26

Physical Properties of lungs

compliance
elasticity
airway resistance

27

compliance

ease of expansion
increase compliance -> easier to expand lungs -> decrease work of breathing

28

elasticity

stretching force; ability to return to normal length or volume
inward recoil force of lungs is due to elastic tissue and surface tension of fluid lining alveoli

29

airway resistance

mostly depends on diameter of small airways
smooth muscle of bronchioles -> bronchoconstriction/dilation

30

Surface tension

results from forces between water molecules at air-water interface
contributes to inward recoil force in lungs, tends to collapse alveoli inward
greater effect on small alveoli than large alveoli (Law of LaPlace: P=2T/r)