week 7 Flashcards
describe the upper respiratory tract
the upper respiratory tract is composed of the airways from the nasal cavity to the larynx
describe the lower respiratory tract
the lower respiratory tract is composed of the airways from the trachea to the lungs which are composed of the bronchi which leads to the bronchioles which lead to the alveoli
where are the lungs found?
the lungs are found in the thoracic cavity and are enclosed within the rib cage and diaphragm
describe the nasal cavity
the nasal cavity is found within the nose. it contains hairs and a mucosa to filter air and trap particles. it is connected to paranasal sinuses by small passageways
describe the 3 sections of the pharynx (throat)
nasopharynx: important for warming, humidifying, and filtering inspired air.
oropharynx: passageway for both air and food
laryngopharynx: also a common passageway for both air and food
- anterior portion opens into the larynx and posterior portion opens into the esophagus
describe the larynx
also known as the voice box, the larynx contains the vocal cords and is an important passageway for keeping food and liquids out of the respiratory tract
describe what happens to the larynx during swallowing
the larynx is lifted up by the surrounding muscles and the glottis is closed by the epiglottis - this blocks off the entryway into the larynx
glottis is the opening to the larynx
describe the trachea
- the anterior and lateral surfaces of the trachea are covered in rings of hyaline cartilage. the posterior opening allows the esophagus to expand during swallowing.
the lumen of the trachea is lined with a mucosa - pseudostratified ciliated columnar epithelial cells and goblet cells
lowest part branches into the right and left primary bronchi.
describe the bronchial tree
the primary bronchi are very similar in appearance to the trachea
as the bronchi become smaller:
- cartilage rings become incomplete and more space is found between each ring
- smooth muscle lining - the small bronchi can change diameter to control air flow into specific bronchioles and alveoli
describe the bronchioles
the bronchioles are the smallest airways. they have an inner lining composed of simple cuboidal epithelium and are enclosed within a thick ring of smooth muscle.
bronchioles have no hyaline cartilage and are lined w/ elastic fibers
airflow is modulated by bronchoconstriction and bronchodilation
respiratory bronchioles have some alveoli budding directly off the walls and each respiratory bronchiole branches into two more alveolar ducts.
describe the alveoli
the alveolar ducts end in alveolar sacs. alveoli are the final destination for inspired air within the respiratory tract - alveoli are also lined with elastic fibers
describe type I alveolar cells
- innermost layer of the resp membrane
- simple squamous cells
- account for 90% of cells in the alveoli
- gases diffuse across these cells (O2 and CO2)
describe type II alveolar cells
- small cuboidal cells
- account for 10% of alveolar wall
- responsible for making and secreting surfactant
describe alveolar macrophages
immune cells that eat up and digest debris that get into the alveolus
what does surfactant do
surfactant interrupts the H bonds that create surface tension in the inner lining of the alveoli in order to reduce this tension within the alveoli
what are the left and right lungs separated by?
they are separated by the heart and the mediastinum
the left lung only has 2 lobes (superior and inferior) and a cardiac notch (groove to make space for the heart)
right lung has 3 lobes (superior, middle, and inferior)
inferior base of the lungs rest on the diaphragm
each lung is found within a pleural cavity
describe the 2 serous membranes that each lung is encased in within the pleural cavity
parietal pleura: the outer layer, fused to the rib cage and the diaphragm - turns over itself and turns into the visceral pleura
visceral pleura: the inner layer, continuous with the surface of the lungs. divides into fissures to form the lobes
what do the pleural membranes secrete in to the pleural cavity and why
they secrete a fluid in order to lubricate the lungs as they expand and recoil during ventilation
define ventilation
the mvmt of air in and out of the lungs
what way does air flow in the pressure gradient
air ALWAYS flows down the pressure gradient - moves from areas of high pressure to areas of low pressure.
what are volume changes in the lungs due to
contraction and relaxation of skeletal muscles as well as the recoil properties of the elastic lungs
what are the 2 main pressures that determine air flow in and out of the lungs
- atmospheric pressure (at seal level = 760 mmHG)
- intrapulmonary pressure (within all the alveoli)
there is a 3rd pressure called intrapleural pressure - pressure within the pleural cavity that changes a small amount during pulmonary ventilation
briefly outline the steps of the process of pulmonary ventilation
- lungs between breaths, just after expiration - no air flow in or out of lungs
pulm pressure = atm pressure - lungs increase volume - descreases pulm pressure. air flows into lungs
pulm pressure < atm pressure
air continues to flow in until pulm pressure = atm pressure
- the lungs are at the end of inspiration - no airflow in or out of lungs
pulm pressure = atm pressure - expiration - lung volume decreases - air flows out of lungs
pulm pressure > atm pressure
list skeletal muscles of quiet inspiration and expiration
quiet inspiration:
- diaphragm
- external intercostals
quiet expiration:
- none
describe when accessory muscles of expiration/inspiration are used
when inspiration/expiration is more deep and forceful
list the factors that influence pulmonary ventilation
- airway resistance
- alveolar surface tension
- pulmonary compliance and elastance
describe bronchodilation vs. bronchoconstriction
bronchodilation: relaxation - increases the diameter of bronchioles. decreases airway resistance and increases air flow
bronchoconstriction: contraction - decreases the diameter of the bronchioles. increases airway resistance and decreases airflow.
what 3 factors is pulmonary compliance and elastance determined by
- degree of alveolar surface tension
- distensibility and elasticity of elastic tissue
- ability of the chest wall to expand during inspiration
what happens if compliance and elastance decrease?
if compliance decreases: lungs are less able to expand and the effectiveness of inspiration decreases
if elastance decreases: lungs are less able to recoil and the effectiveness of expiration decreases
what do we use to measure the volume of air exchanged with each breath
a spirometer. it produces a graph that allows us to measure lung volumes and capacities - these are called pulmonary function tests
minute ventilation
the total volume of air that moves in/out of the lungs per minute
minute ventilation = tidal volume x # of breaths per min
tidal volume
the amount of air inspired or expired during ventilation at rest
normal value is ~500 mL
inspiratory reserve volume
the amount of air that can be forcibly inspired after normal inspiration
normal value is ~1900-3000 mL
expiratory reserve volume
the amount of air that can be forcibly expired after normal expiration
normal value is ~1000 mL
residual volume**
**can’t be measured with spirometry
the air remaining in the lungs after max expiration
normal value is ~1200 mL
inspiratory capacity
total amount of air that a person can inspire
IC = TV + IRV
functional residual capacity
amount of air left in the lungs after tidal expiration
FRC = ERV + RV
vital capacity
total amount of air that you can move in and out of your lungs
VC = TV + IRV + ERV
total lung capacity
total amount of air that can fill the lungs
TLC = TV + IRV + ERV + RV
alveolar ventilation
the total volume of air reaching alveoli per min - some air never reaches the alveoli; remains in conducting portion of the lungs (anatomical dead space: VD = VT x 0.3)
VA = breaths per min x (tidal volume - anatomic dead space)
define gas exchange
the diffusion of gases from one medium to another (ex: air in lungs to blood in capillaries and vice versa)
daltons law of partial pressures
each gas in a mixture exerts its own pressure (partial pressure). the total pressure of a gas mixture is the sum of the partial pressures of all its component gases
P ATM = P N2 + P O2 + P CO2
henrys law
the degree to which gas dissolves in liquid is proportional to both partial pressure and solubility in liquid. explains the behaviour of gases in air that come in contact with water in the body.
- N2 has very low solubility in water, so although there is high PN2 gradient between lungs and blood, virtually none enters into the blood
- O2 has a relatively low solubility in water
- CO2 is the most soluble in water of the 3 gases
what factors affect the efficiency of pulmonary gas exchange
- surface area of the total respiratory membrane (where gas exchange occurs)
- the distance for the diffusion of gases
- matching of ventilation and perfusion
list the factors affecting the efficiency of tissue gas exchange
- surface area available for gas exchange
- perfusion of the tissue
- distance of diffusion
