Chapter 16, Part 1-4 Flashcards
External Respiration
the exchange of oxygen and carbon dioxide between the atmosphere and the tissues of the body
- involves both the respiratory and cardiovascular systems
Air Pathway through Respiratory Tract
(1) Air travels through nares into the nasal cavity
(2) Down the pharynx (throat)
(3) Through the glottis (the opening of the larynx aka voice box)
- slit in the middle of the larynx created by 2 vocal cords
(3) Travels anteriorly to the trachea (windpipe)
- avoids posterior esophagus
(4) Splits into the left and right primary bronchus
- bronchi have rings of highland cartilage to keep tubes open
(5) Splits into secondary bronchi
- LPB splits into 2 LSB
- RPB splits into 3 RSB
(6) Splits into tertiary bronchi
- LSB and RSB split into ~10
(7) Bronchi continue branching until reach bronchioles
- diameter must be 0.5-1 mm
(8) Bronchioles continue branching into terminal bronchioles
- diameter < 0.5 mm
- end of conducting zone (conducts air in and out of lungs)
(9) Terminal bronchioles become respiratory bronchioles
(10) Respiratory bronchioles will have alveoli
- where external respiration occurs
- respiratory bronchiole –> alveoli –> alveolar ducts –> alveolar sacs
Chest Wall
encapsulates the right and left lung and heart
Bony part: ribs (12), sternum, thoracic vertebrae (12)
Muscular Part: intercostal muscles (muscle that lays between ribs), diaphragm
External Intercostal Muscles
Origin: bottom border of upper rib
- origin = bone that does NOT move
Insertion: upper border of lower rib
- insertion = bone that DOES move
when intercostal muscles contract, insertions will move towards the origin (pulled upwards and outwards)
Diaphragm
Origin: some of lumbar vertebrae and some bottom orders of lowest ribs
Insertion: central tendon (but does not attach onto a bone, so does not count)
when contracts, central tendon moves towards origin (pulled towards lumbar vertebrae and flattens out)
Pleural Membrane
Visceral Pleura: portion of the membrane physically touching the lung (direct contact with the organ)
Parietal Pleura: portion of the membrane that does not make physical contact with the lung
- attached to the inside of the chest wall
- physically makes contact with the diaphragm
Pleural cavity: space in between the visceral and parietal pleura (air)
- the L and R lung each have their own pleural membrane
- without the membranes, the lungs could not be inflated and breathing could not happen
Atmospheric Pressure
pressure air creates in the atmosphere at sea level
- standard atmospheric pressure is ~760 mm Hg
Intra-Alveolar Pressure
pressure within the alveoli themselves
- air pressure within the lungs
- same at atmospheric pressure (~760 mm Hg) in between breaths
Intrapleural Pressure
air pressure that exists inside the pleural cavity
- different than intra-alveolar pressure and atmospheric pressure (~756 mm Hg)
Transpulmonary Pressure
the difference between intra-alveolar pressure and intrapleural pressure
760 mm Hg - 756 mm Hg = 4 mm Hg
Establishment and Influence of Pleural Pressure
- lungs incredibly elastic, constantly recoiling inwards (wanting to collapse)
- chest wall constantly wanting to expand
- opposite pulling will pull visceral and parietal pleura AWAY from each other
- VP being pulled inward and PP being pulled outwards
- causes the volume of the pleural cavity to expand
- increases vol. –> gas molecules have more room –> reduction in air pressure
- intrapleural pressure (756 mm Hg) is less bc the pleural cavity is constantly expanding, thus driving down pressure so that it is less than the air pressure in the lungs
- if intrapleural pressure was not less than intra-alveolar pressure, the lungs would collapse
- air will move from high to low pressure
- air in lungs (alveoli) constantly wanting to expand outwards and move towards air in pleural cavity (reduced pressure)
- keeps lungs inflated inside of thoracic cavity
Pulmonary Ventilation
INSPIRATION
- increasing in transpulmonary gradient (pressure gradient) causes alveoli to expand and intra-alveolar pressure to fall
- 760 mm Hg –> 758 mm Hg
- need alveoli to expand because pressure will fall
- air pressure in alveoli less than atmospheric pressure –> air will move from atmosphere to lungs
- intra-alveolar pressure increases in the second half of inspiration back to 760 mmHg
- air enters lungs from atmosphere
- will continue to increase until intra-alveolar pressure and atmospheric pressure equilibrate at end of inspiration
EXPIRATION
- passive process, relaxation of inspiratory muscles
- external intercostal muscles relax, chest wall falls down and in
- parietal and visceral pleura get close together
- vol. of pleural cavity decreases
- intrapleural pressure increases (745 –> 756 mmHg)
- intra-alveolar pressure is 760 mmHg
- transpulmonary pressure decreases (6 –> 4 mmHg)
- less pressure gradient within lungs (alveoli) to expand outwards
- alveoli shrink and collapse around extra air from atmosphere
- elasticity of lungs take over transpulmonary pressure
- intra-alveolar pressure is greater than atmospheric pressure
- air moves from alveoli –> atmosphere
- as air exits, intra-alveolar pressure falls and stops at equilibrium
- returned to beginning of cycle
Influences by lung compliance and airway resistance
Lung Compliance
- first factor influencing pulmonary ventialtion
- how easily lungs (alveoli) can expand
- easy expansion = “high compliance”
- hard expansion = “low compliance”
- influenced by 2 factors:
(1) Elasticity - lungs are enormously elastic which is why they always want to collapse
- elasticity decreases compliance
(2) Surface Tension
- elasticity decreases compliance
- inside of alveolus, there is a lining of water
- water is polar –> molecules constantly want to come together and form water droplets (surface tension)
- their attraction pulls the alveolus shut –> decreases compliance
- type II alveoli produce and release surfactin which breaks hydrogen bonds and thus decreases surface tension (increasing compliance)
If lungs cannot expand –> no pressure gradient –> air flow decreases
Restrictive Lung Diseases
- cause low compliance (decrease)
- Ex: Pulmonary Fibrosis
- lungs become rigid and stiff
- elastic fibers replaced with stiff collagen –> difficult expansion
- with decreased compliance = no pressure gradient
- treatment includes slowing down synthesis of collagen but more are irreversible
Lung Resistance
- when smooth muscle contracts, the airway is narrowed (high resistance, low airflow)
- bronchoconstriction
- when the smooth muscle relaxes, the airway is widened (low resistance, high airflow)
- bronchodilation
- lots of mucus within lungs (will exist within lumen) which increases resistance, reducing airflow
- swollen bronchioles increase resistance, and decrease airflow
- flow is inverse to resistance
