Respiratory 1 Flashcards
What is the function of the respiratory system?
-exchange O2 & CO2 between the environment & tissues
What does the respiratory system include?
lungs & series of airways that connect lung to external environment
1. Conducting zone:
-air in & out of lungs
2. Respiratory zone:
-lined w alveoli = gas exchange location
Describe what the conducting zone includes.
-nasal cavity, nasopharynx, larynx, trachea, bronchi, bronchioles, terminal bronchioles
>bring air in & out of respiratory zone for gas exchange
>humidify, warm, filter air before gas exchange
>known as anatomic dead space
What is the conducting airway lined with?
-mucus secreting ciliated cells
>remove inhaled particles
>LG = filtered out in nose
>SM = enter airway, captured by mucus, swept up by cilia
What type of muscle is in the walls of the conducting airways?
-smooth muscle
>sympathetic & parasympathetic
>changes in diameter of conducting airways = changes resistance = changes airflow
Describe the sympathetic system in the conducting zone.
-via circulating EPI = activates B2
-Gs
-dilation of airway
Describe the parasympathetic system of the conducting zone.
-activates M3
-Gq
-constriction of airways
Describe the respiratory zone.
-where gas exchange occurs
-respiratory bronchioles, alveolar ducts, alveolar sacs
Describe respiratory bronchioles.
-transitional
-cilia
-sm muscle
-alveoli bud off walls
Describe alveolar ducts.
-lined w alveoli
-NO CILIA
-little sm muscle
-terminate in alveolar sacs (lined with alveoli)
Describe alveoli.
-pouch-like invaginations of walls of respiratory bronchioles, alveolar ducts, & alveolar sacs
>alveoli walls = thin, lg surface for diffusion of gases & covered by capillaries
alveoli poorly perfused w blood = dead space
Describe alveolar cells.
-alveolar walls = elastic w epithelial cells (alveolar cells)
>also called Type I & Type II pneumocytes
Describe type I alveolar cells.
-95% of alveolar surface
-form tight epithelial barrier w type II cells
-keeps alveoli dry
-thin = efficient gas exchange between alveolus & pulmonary capillaries
Describe type II alveolar cells.
-5% of alveolar surface
-synthesize pulmonary surfactants
>reduce surface tension of alveoli
>prevent alveoli from collapsing at the end of expiration
-secrete cytokines
>recruit inflammatory cells
-regen for type I & II
Describe alveolar macrophages.
-keep alveoli free of debris (since they have no cilia)
-migrate to bronchioles
>cilia go to upper airways & pharynx = swelled/expectorated
Describe the respiratory cycle.
-inspiratory phase -> expiratory phase
>inspiration = more effort than expiration (passive) except in horses
Describe inspiration.
-enlargement of thorax & lungs (inflow of air)
>enlargement due to diaphragm & external intercostal m
>diaphragm = caudal
>external intercostal m = cranial & outward
Describe expiration.
-passive (can be active during accelerated breathing or impediments to outflow of air)
-internal intercostal m
Describe abdominal breathing.
-predominates
-visible movement of abdomen
Describe costal breathing.
-rib movement
-painful conditions = predominate
IMP TERMS.
- Eupnea = normal breathing
- Dyspnea = difficult
- Hyperpnea = increased depth/freq
- Polypnea = rapid/shallow (panting/hyperpnea similar)
- Apnea = cessation
- Tachypnea = excessive rapidity
- Bradypnea = abnormal slowness
Describe pulmonary ventilation.
-lung = elastic
-thin layer of pleural fluid (lube)
-suction of excess fluids into lymphatic channels = slight neg pressure between visceral & parietal surface
Describe barometric pressure.
-aka atmospheric pressure
>mixture of gases (79% N2 & 21% O2)
>gases = total atmosphere pressure of 760 mmHg @sealevel
*respiratory pressures = expressed relative to atmospheric pressure (neg or pos)
*relative pressures = atmospheric pressure is 0
What is the pressure in the lungs?
-since barometric pressure (Pb) is constant = pressure in lungs must be high or lower than Pb for air to flow
1. Pleural pressure
2. Alveolar pressure
3. Trans pulmonary pressure
*boyles law = volume & pressure inversely proportional
Describe pleural pressure.
‘Intra-pleural pressure’
-pressure exerted outside lungs (pleural cavity)
-less than atmospheric pressure (-5 to -7)
-neg pressure increases during inspiration w the increase in volume [pressure in pleural cavity increases when volume decreases]
>during expiration its reversed
doesnt equilibrate w atmospheric pressure or alveolar pressure bc no communication
Describe alveolar pressure.
‘Intra-pulmonary pressure’
-pressure in alveoli that increases & decreases w each breath
>when the volume increases, alveolar pressure decreases
-always equal to atmospheric pressure at the end of inspiration & expiration = rest period
inward flow of air into alveoli during inspiration = pressure in alveoli falls slightly neg
Describe transpulmonary pressure.
-pressure diff between alveolar pressure & pleural pressure in lungs
-measures elastic force in lungs that collapse during respiration = recoil pressure
>at a lung volume, the transpulmonary pressure is equal & opposite to the elastic recoil pressure
>if transpulmonary pressure is 0 (alveolar pressure = pleural pressure) the lungs collapse pneumothorax
What is the transpulmonary pressure under normal conditions?
-always pos
-intrapleural always neg
-alveolar pressure from neg to pos
What causes the lungs to collapse (recoil pressure)?
- Stretching of elastin & collagen by lung inflation
- Surface tension of fluid lining the alveoli
surface tension = force between water in the liquid that lines each alveoli
Describe surfactants.
-surface active substances where water molecules have less attraction
-lipoprotein complex = 30% protein & 70% lipid
>produced by type II pneumocytes
-accumulate at surface of alveoli & displace water = decrease surface tension (T)
>prevent collapse of lung at end of expiration
>increases pulmonary compliance
—reduces work of inflating lungs
What needs to happen for inspiration to occur?
-lungs must expand when stretched = compliance
>lung expansion for each increase in transpulmonary pressure (Palv - Pip)
>factors that affect compliance =
—destroy lung tissue
—fibrotic
—edematous
—impede lung expansion
lack of surfactant = decreased compliance
What needs to happen in order for expiration to occur?
-lungs get smaller when stretching force is released = elasticity (return to normal when distended)
-elastic tension increases during inspiration when lungs are stretched & reduced by elastic recoil during expiration
elasticity = aids in pushing air out
