Introduction of the Respiratory, Mechanics of Breathing System

main functions of the respiratory system

1. gas exchange

2. pH balance

3. phonation

4. pulmonary defense mechanisms

5. pulmonary metabolism of bioactive materials 

gas exchanges in the respiratory system

1. atmosphere to lung (ventilation)

2. lung to blood

3. blood to cells

phonation

production of sound by air movement through the vocal cords

pulmonary defense mechanisms

1. nasopharynx: swallowing particles

2. bronchi: mucociliary system transports particles

3. alveoli: macrophages engulf particles and send to lymphatics

where do bronchi cilia push particles trapped in mucus towards?

pharynx

goblet cell

secretes mucus

muscles of inspiration

1. external intercostals

2. diaphragm 

muscles of expiration 

1. internal intercostals

2. abdominal muscles 

conducting system of respiratory system

1. from trachea to terminal bronchioles 

2. no gas exchange 

3. dead space 

exchange surface of respiratory system

1. from respiratory bronchioles to alveoli

2. gas exchange

trachea structure

1. large diameter 

2. rings of cartialge 

alveolar-capillary unit

1. site of gas exchange 

2. highly perfused 

type I alveolar cells

for gas exchange

type II alveolar cell

synthesizes surfactant

alveolar capillary barrier is the perfect distance for speedy…

diffusion of gases

intrapleural space

1. space between pleural membranes

2. negative pressure at rest 

how does intrapleural pressure change with breathing?

1. inspiration: more negative

2. passive expiration: return to rest

3. active expiration: positive 

respiratory activity is under ________ and ________ control

involuntary, voluntary

where are respiratory control centers located?

1. medulla

2. pons 

what causes changes in thoracic cavity volume?

1. diaphragm contraction/relaxation

2. ribe cage movement 

when the diaphragm ______, thoracic volume increases, when the diaphragm ________, thoracic volume decreases

contracts, relaxes 

when the thoracic cavity expands in volume, the thoracic pressure ________

decreases 

elastic recoil of the chest wall tries to _______ the chest wall _______

pull, outward

the elastic recoil of the lung creates an… 

inward pull 

intrapleural pressure is…

subatmospheric

during inspiration, the intrapulmonary (alveolar) pressure… 

drops to -1 mmHg

air flows into lungs down its pressure gradient until intrapulmonary (alveolar) pressure is… 

0, equal to atmospheric 

during expiration, intrapulmonary (alveolar) pressure…

rises to +1 mmHg

formula for compliance

compliance = change in volume / change in alveolar pressure

compliance

the ease with which something can be stretched

elasticity

the tendency to oppose stretch or distortion, or the recoil force to return to original shape

a fibrotic lung has ________ compliance 

low

an emphysema lung has _______ compliance

high

what does a lung that is stiff and scarred demonstrate?

low compliance

what does a lung that has lost elastic elements and can stretch more easily demonstrate? 

high compliance 

law of LaPlace formula and units

1. P = 2T/r

2. P = pressure 

3. T = surface tension 

4. r = radius 

the pressure within an alveolus is correlated to __________ and its_________

surface tension, radius 

a smaller alveoli would tend to have _______ pressure than a larger one due to increased surface tension and a smaller radius

higher

two methods to prevent lung collapse due to surface tension forces

1. surfactant 

2. alveolar interdependence 

surfactant

lines surface of alveoli to oppose surface tension forces

when is surfactant most useful?

1. at low lung volumes 

2. resist the tendency of alveoli to become even smaller 

alveolar interdependence

1. physical tethering of lung parenchyma 

2. secures alveoli and holds them open

inspiration leads to _________ chest wall recoil and ________ alveolar recoil

decreased, increased 

at resting lung volume, lung inward recoil forces and chest wall outward recoil forces are…

balanced and in opposition

during normal inspiration as lung volume increases, the chest wall moves outward and ________ outward recoil, while inward lung recoil is ________

decreases, increased 

during maximal inspiration the chest wall and alveoli recoil forces…

are inward and of a large magnitude 

during maximal expiration the inward lung recoil _______ and the outward chest wall _______

decreases, increases 

formula for resistance, using pressure difference and flow

resistance = pressure difference / flow 

laminar flow

1. streamline 

2. usually in smaller airways

3. air flows more efficiently 

turbulent flow

1. erratic 

2. usually in large airways 

3. energy needed to drive air forward 

transitional flow

1. mix of laminar and turbulent flow 

2. occurs at branch points 

with laminar flow, what is resistance related to? 

1. directly related to viscosity and length of tube

2. indirectly related to radius of tube

where is airway resistance lowest in the respiratory system?

terminal bronchioles

overall resistance to airflow ________ with increased number of branches

decreases

parasympathetic stimulation causes _______ of airway smooth muscle

constriction

sympathetic stimulation causes _______ of airway smooth muscle

dilation

airway resistance _________ with increasing lung volume

decreases

dynamic compression of airways

1. occurs in smaller airways that lack cartilage 

2. during forceful expiration 

3. when the intrapleural pressure is greater than the pressure in the airway 

4. airway snaps shut