Unit 5 - Respiratory System Flashcards
respiratory system allows for: (4)
- exchange of gases between atmosphere and blood
- homeostatic regulation of body pH
- protection from inhaled pathogens and irritating substances
- vocalization
respiratory system main processes (4):
- gas exchange between atmosphere & lungs
- gas exchange between lungs & blood
- transport of gases by blood
- exchange of gases between blood & tissues
3 “systems” of respiratory system involved in ventilation and gas exchange
- conducting system -> airways
- exchange surface -> alveoli
- pumping system -> bones & muscles of thorax
respiratory system can be divided into 2 parts:
- upper respiratory tract
- lower respiratory tract
upper respiratory tract components (4)
mouth, nasal cavity, pharynx, larynx
lower respiratory tract components (4)
trachea, bronchi, bronchioles, lungs
what are alveoli? where are they?
- tiny hollow sacs found at ends of terminal bronchiole
- wrapped with an extensive capillary network (covers most of alveolar surface)
how does gas exchange happen between alveoli and capillaries?
diffusion
two types of alveoli cells:
their functions:
- Type I alveolar cells -> large but thin
- rapid gas diffusion - Type II alveolar cells -> smaller but thicker
- synthesize & secrete surfactant
how many pulmonary arteries?
2 (1 to each lung)
what is rate of blood flow like to the lungs?
high because all the output of right ventricle goes to lungs (versus systemic circulation from left ventricle)
blood pressure of respiratory system relative to systemic circuit?
low relative to systemic circuit because right ventricle does not pump as forcefully
___ and ______ allow for ventilation
bones and muscles of the thorax
relation of lungs to chest wall
- what is chest
- is it open/closed compartment; how
- what is wall formed by
chest = thorax
closed compartment
-closed off at top by neck muscles and connective tissue
-closed off at bottom by diaphragm
wall formed by ribs and intercostal muscles
where are intercostal muscles
between ribs
what are the two lungs surrounded by? what is its function
surrounded by the pleural sac -> forms a double membrane around each lung
-pleura is filled with fluid
-acts as a lubricant
-pleural space
what is the purpose of the pleural space?
subatmospheric; keeps lungs inflated in resting state
total pressure of a mixture of gases =?
total pressure of a mixture of gases = sum of the partial pressure of individual gases
gases move from ___ to ___
high to low pressure
how are volume and pressure of gases related?
inversely related
amount of gas that will dissolve in a liquid is determined by (2):
- partial pressure of gas
- solubility of gas in liquid
partial pressure of an atmospheric gas =?
Patm X %(gas in atmosphere)
eg PO2 = 760mmHg X 21% =160mmHg
pressure-volume relationship formula?
described by what law?
P1V1 = P2V2
Boyle’s Law
why are pressure-volume relationships critical for ventilation?
- during inspiration and expiration, volume of thoracic cavity changes
- causing changes alveolar pressure (driving force for air flow)
can lungs change volume on their own?
no, bc they dont have muscle
lungs are what kind of structures?
passive elastic (balloon-like)
what does lung volume depends on? (2)
- transpulmonary pressure
-> difference between alveolar pressure & intrapleural pressure - degree of lung elasticity
pressure inside lungs is?
alveolar pressure
pressure outside lungs?
pressure in intrapleural fluid
what is ventilation?
exchange of air between atmosphere and lungs
how do airways condition the air before reaching lungs? (3)
- warm air to 37deg C to maintain core body temp, protect alveoli
- add water vapor to air to prevent drying of epithelia
- filter out foreign material
how do airways filter out foreign material? (detailed)
airways are lined with ciliated epithelia that secrete a watery saline solution
cilia are covered with mucus (secreted by goblet cells)
mucus contains immune cells that kill invaders
mucus is moved up to the pharynx (mucus escalator)
transferred to digestive tract where more bacteria are killed
how is the watery saline solution in the airway created?
- cells move Cl- from ECF into cell via NKCC(Na-K-Chloride-Chloride) ->
Cl- transported to airway lumen via apical anion channel (incl FTR) - Na+ moves btw cells from ECF to lumen ->
[NaCl] gradient draws water towards lumen creating WATERY SALINE solution
cystic fibrosis caused by?
mutation in a Cl- channel
- cystic fibrosis transmembrane conductance regulator (CFTR)
what are the results of cystic fibrosis?
-prevents appropriate secretion of water to make watery saline layer in lumen
-cilia are trapped in sticky/thick mucus
-blocks airways
-prevents proper removal of bacteria, repeated infections
lethal over time
during quiet breathing, expiration is a ____ process
passive
(depends on elastic recoil of thorax muscles and lungs)
what muscles does active expiration use?
internal intercostals & abdominal muscles
what muscles does inspiration use?
external intercostals & diaphragm
inspiration steps
- somatic motor neurons trigger diaphragm and external intercostal contraction
- thorax expands -> increase thoracic volume
- alveolar and intrapleural pressure decreases
- lungs expand, air flows in
expiration steps
- impulses from somatic motor neurons stop
- diaphragm and thoracic muscles relax which returns thorax to original positions -> decrease volume (elastic recoil)
- alveolar and intrapleural pressure increases
- elastic recoil of lungs decrease lung volume -> air flows out
when does intrapleural pressure develop?
foetal development
pneumothorax is?
air getting into pleural cavity, intrapleural pressure increases
-> pressure difference destroyed
-> lung collapses
how to treat pneumothorax?
apply suction to remove air and seal hole
what does the work required to breathe depend on? (2)
- compliance (stretchability) of lungs
- resistance to air flow in airways
lung compliance
ability of lungs to stretch
lower lung compliance = harder to breathe
lung elastance
degree and/or speed to return to resting lung volume
low lung elastance = expiration must be active (lung does not return on its own).
Bronchiole diameter can be affected by ___, ___, and ____
nervous system, hormones, paracrines
___ causes bronchodilation
CO2
____ released in response to tissue damage or allergic reactions causes _____
histamine
bronchoconstriction
neural control of bronchioles & function?
primarily by parasympathetic neurons that cause bronchoconstriction
- to protect lower respiratory tract from inhaled irritants
NO significant sympathetic innervation
hormonal control of bronchioles is done primarily via ___ ___
circulating epinephrine
-through beta2 receptors in smooth muscles of bronchioles -> bronchodilation
-used as treatment for asthma
instrument that measures air movement for assessment
spirometer
TV =?
tidal volume;
amount of air moved in a single normal expiration/inspiration
IRV?
inspiratory reserve volume;
maximum amount of air that can be inspired above tidal volume
ERV?
expiratory reserve volume; maximum amount of air that can be expired above tidal volume
RV?
residual volume;
amount of air left in lungs after maximal expiration
the sum of two or more lung volumes is called?
capacity
VC?
vital capacity;
maximum amount of air that can be voluntarily moved into or out of respiratory system
VC=IRV+ERV+VT
TLC?
total lung capacity
TLC = VC + RV
MV stands for?
formula?
minute volume
MV(mL/min) =
VT(mL/breath) X respiratory rate(breaths/min)
anatomic dead space located airways ->?
no gas exchange
air in trachea, bronchi, bronchioles do not participate in gas exchange
alveolar volume =?
alveolar volume = VT - dead space
alveolar ventilation formula?
Alveolar ventilation =
ventilation rate X alveolar volume
(more accurate bc it considers dead space)
ventilation is matched to ___ ___ ___
alveolar blood flow (to maximize gas exchange)
increase in tissue PO2 results in _________
vasodilation in the arteriole
if ventilation of alveoli in an area of the lung decreases, then ________________
tissue O2 in that area also decreases
decreases in tissue po2 result in ________
vasoconstriction in arteriole (divert blood)
rate of diffusion across lungs is:
- ___ to partial pressure gradient
- ___ to available surface area
- ___ to membrane thickness
- ___ over short distances
proportional
proportional
inversely proportional
greatest
partial pressure gradient influenced by (2):
- composition of inspired air (affected by altitude)
- alveolar ventilation
(affected by airway resistance/lung compliance)
emphysema
destruction of alveoli
- physical loss of alveolar surface area
fibrotic lung disesase
- scarring thickens alveolar membrane
pulmonary oedema
- increase in interstitial fluid in lungs leads to increase in diffusion distance
asthma
- increase airway resistance, decrease ventilation
each haemoglobin molecule can bind up to ___ oxygen molecule
4
what does oxygen bind with in haeme group?
iron
what is haemoglobin bound to oxygen called?
oxyhaemoglobin (HbO2)
what is unbound haemoglobin called?
deoxyhaemoglobin (Hb)
does increasing alveolar PO2 have an effect on percent saturation of haemoglobin?
not much effect
the 3 ways CO2 is transported in blood?
the majority is through?
- dissolved in plasma
- interact with proteins (incl Hb)
- convert to bicarbonate (majority)
what is co2 + hb called?
carbaminohaemoglobin (Hb X CO2)
how is co2 converted to bicarbonate?
catalyzed by carbonic anhydrase (in RBCs) ->
H+ formed binds to Hb
bicarbonate ions are moved out by transporter protein (chloride shift); trade chloride for bicarbonate
how does bicarbonate turn back into co2?
alveoli PCO2 lower than blood;
CO2-bicarbonate reaction shifted other way (still carbonic anhydrase)
CO2 diffuses out of RBC into plasma then alveoli
diaphragm and intercostals are ____ muscles
skeletal
contraction of respiratory muscles initiated in ___ ____
a) what nuclei are involved?
what contributes to breathing rhythm?
medulla oblongata
a) Dorsal respiratory group (DRG) -> inspiratory neurons (I neurons)
Ventral respiratory group (VRG) -> ACTIVE expiratory neurons (E neurons)
network of neurons called central pattern generator in medulla oblongata
chemoreceptors can modify rhythm of central pattern generator. what 2 are involved?
- peripheral chemoreceptors
- central chemoreceptors
peripheral chemoreceptors
- located in carotid bodies -> glomus cells
- decrease PO2 or decrease pH or increased PCO2 = faster ventilation
- most cases, pH and PCO2 more important (PO2 needs BIG change)
central chemoreceptors
- located in medulla oblongata (most important chemical controller of ventilation)
- higher PCO2 in arterial blood -> faster ventilation
- CO2 crosses blood brain barrier into CSF -> activates central chemoreceptors via changes in pH from making carbonic acid
(NOTE: sense changes of H+ in CSF, NOT in arterial blood)
why do mechanoreceptors control ventilation?
to protect the lungs
what are the 2 mechanoreceptors?
- irritant receptors - in airway mucosa
- stimulation triggers parasympathetic neurons (bronchoconstriction) - stretch receptors - in airway smooth muscle
- triggered if lungs are over-inflated
- terminate ventilation -> Hering-Breuer inflation reflex
