Chapter 16: Respiratory System - Ventilation Flashcards
internal vs external respiration
- external respiration refers to the exchange of oxygen and carbon dioxide between the atmosphere and body tissues
- internal respiration is the gas exchange between the blood and the tissue
major organs of the respiratory system
- lungs
- upper airways
- respiratory tract
what are the upper airways?
- refers to air passages in the head and neck
- this includes the nasal cavity and oral cavity which lead to the pharynx
what is the respiratory tract?
- includes all air passageways from the pharynx to the lungs
- has two components:
(1) conducting zone (upper part)
(2) respiratory zone (lower part)
what is the difference between the conducting zone and respiratory zone?
conducting zone:
- is the the upper part of the respiratory tract
- functions in conducting air from the larynx to the lungs
respiratory zone:
- the lowermost part of the respiratory tract
- contains the sites of gas exchange within the lungs
–> the main difference between the conducting and respiratory zones in the lungs is the thickness of the walls around the air spaces. gas exchange happens only in air spaces with thin walls.
components of the conducting zone
- larynx = voice box that air passes through
- trachea = windpipe, connects larynx to bronchi
- bronchi = main airway branching off trachea supplying each lung
- secondary bronchi = 3 on right, 2 on the left
- tertiary bronchi = supplies speicifc regions of the lungs
- bronchioles = tiny air passageways
- terminal bronchioles = final and smallest components
3 functions of the conducting zone
1) to provide a passageway for air to enter and exit the respiratory zone (where gas exchange occurs)
2) increase air temperature to adjust to body temperature
3) humidify air to keep the respiratory tract moist
what specialized cells line the conducting zone of the respiratory system?
- epithelium lines the conducting zone
- contains goblet cells
- contains ciliated cells
–> the goblet cells secrete mucus that coats the airway and traps foreign particles within inhaled air
–> cilia of the ciliated cells beat in a whiplike fashion the process the mucus up the throat where it can be swallowed
–> this is called the mucus elevator which prevents mucus from accumulating in airways and decreasing likelihood of infections
what changes occur to tissues within the conducting zone?
- cartilage is abundant in the walls of the trachea and bronchi but decreases in amount as bronchi diameter reduces.
- there’s no cartilage in bronchioles.
- smooth muscle is sparse in the trachea and bronchi but increases as airways become smaller.
- bronchioles lack cartilage and have more smooth muscle, enabling them to change diameter and regulate air flow resistance.
components of the respiratory zone
- respiratory bronchioles
- alveolar ducts
- alveolar sacs
- alveoli
functions of the respiratory zone
- allow for exchange between air and blood via diffusion
what are alveoli?
- balloon-shaped air sacs located at the end of the respiratory zone
- they facilitate the exchange of oxygen and carbon dioxide
- they expand during inhalation, taking in oxygen, and shrink during exhalation, expelling carbon dioxide
characteristics of alveoli
- alveoli are not independent structures, they are connected via alveolar pores
- type I alveolar cells form the respiratory membrane, consisting of a thin, single layer of epithelial cells.
- type II alveolar cells secrete surfactant, which reduces surface tension and prevents alveolar collapse
- also contain macrophages that engulf particles and pathogens inhaled into the lungs
what is the respiratory membrane?
- endothelial cell layer of capillaries and epithelial cell layer of alveoli alveolar fuse to form a thin barrier
- it separates air from the blood
- the thinness helps with gas exchange
structures of the thoracic cavity
- the chest wall:
(1) ribcage
(2) sternum
(3) thoracic vertebrae
(4) internal and external intercostal muscle
(5) the diaphragm - the pleura
- pleural sac around each lung
- intrapleural space with intrapleural fluid
what forces drive pulmonary ventilation?
- air moves into and out of lungs by bulk flow
- bulk flow is driven by a pressure gradient between the alveoli and the outside air (atmosphere)
- air moves from high to low pressure
inspiration vs expiration
- inspiration = pressure in the lungs is less than the pressure in the atmosphere, so air moves into the alveoli
- expiration = pressure in the lung exceeds the pressure in the atmosphere, so air leaves the alveoli
4 pressures associated with ventilation
1) atmospheric pressure
2) intra-alveolar pressure
3) intrapleural pressure
4) transpulmonary pressure
what is atmospheric pressure?
- the pressure of outside air
- at sea level = 760 mmHg
- at altitudes higher than sea level, atmospheric decreases
- at altitudes lower than sea level, atmospheric pressure increases
what is intra-alveolar pressure (Palv)
- the pressure of air within the alveoli
- intra-alveolar pressure varies during the phases of ventilation
- the difference in intra-alveolar pressure and atmospheric pressure drives ventilation
–> when atmospheric pressure > intra-alveolar pressure (is negative) = inspiration occurs
–> when intra-alveolar pressure (is positive) > atmospheric pressure = expiration