Lecture 24- respiration Flashcards
the upper respiratory tract contains
nasal cavity
pharynx
larynx
site of gas exchange
alveoli
common passageway shared by respiratory and digestive system
pharynx
why is the surface of the lungs moist?
thin layer of fluid for oxygen to dissolve into before it can diffuse across the alveolar and capillary endothelium
why does the trachea have rings?
to prevent collapse from pressure changes
why does air move into the lungs?
the gas pressure in the lungs is less than atmospheric pressure
why does air move out of the lungs?
gas pressure in lungs is more than atmospheric pressure
(pressure moves to region of lower pressure)
our respiratory system is optimized to take advantage of
bulk flow and diffusion
distance between alveolar airspace and capillary endothelium is —-, allowing gases to diffuse —- between them
short, rapidly
how many cell membranes does a molecule of O2 need to cross to get from the inside of an alveolus into blood?
4 cell membranes
(2 cells)
lower respiratory system
trachea
primary bronchi (R, L)
many smaller bronchi
bronchioles
alveoli
functions of the respiratory system
- Gas exchange: O2 uptake and CO2 release
- Regulating body pH (homeostasis)
- Conditioning of inspired air
- Protection: filtering and clearing foreign particles
- Vocalization
External respiration
= movement of gases between internal environment of body and external environment
inspiration and expiration
describe the 3 types of exchange
exchange 1: atmosphere to lungs (ventilation)
exchange 2: lungs to blood
exchange 3: blood to cells
muscles used for ventilation
external intercostals and diaphragm
for forceful breathing, sternocleidomastoids and scalenes are recruited
pleural membranes
= fluid-filled ballon that wraps around lungs
- visceral pleural membrane
- parietal pleural membrane
what is the pleural membrane made of?
a thin layer of secretory epithelial cells and a thin layer of connective tissue
what does the pleural sac do?
protects lungs
pleural fluid lubricates membranes so they can slide against each other during ventilation
“sticks” the lungs tightly to the thoracic wall; to keep lungs inflated!
role of the airways
filter out foreign substances
- ciliated epithelium
line the trachea and bronchi
warm air to body temp
adds water vapor
how does mucus move out of respiratory tract?
epithelial cells lining the airways secrete saline and mucus
cilia move the mucus layer towards the pharynx, removing trapped pathogens and particles
How is resistance or air flow changed?
resistance is changed by radius!!!!
a small change in radius (r^4) created a large change in resistance (R)
What is R proportional to?
length or airways
viscosity
resistance
R proportional to Ln/r^4
L= length of airways
n= viscosity of air
r= radius
How does radius change? (the radius of the trachea and bronchi can’t change)
Mucus built up in the trachea and bronchi is a common cause of increased airway resistance!!!
Can bronchioles change their radius?
YES
they are collapsible
radius can be changed by neural, hormonal and paracrine effects on smooth muscle
obstructive lung diseases —– airway resistance
increase
Resistance depends on total —–
cross sectional area
where is the most resistance to flow?
trachea and bronchi (small TOTAL cross sectional area)
where is least resistance to flow?
bronchioles; large TOTAL cross sectional area
what significantly increases resistance in bronchioles?
bronchoconstriction
Bronchodilation
=decreased resistance to airflow
Paracrine response to:
CO2
SNS response:
norepinephrine/epinephrine bind to beta 2-adrenergic receptors: relaxation of bronchiole smooth muscle
Bronchodilation SNS response pathway
Gs–> AC –> cAMP –> PKA
Bronchoconstriction
= increased resistance to airflow
paracrine response to:
-histamine released by local mast cells in an immune response
PNS response:
-ACh binds to muscarinic receptors (M3) –> constriction of smooth muscle
Bronchoconstriction PNS response pathway
Gq–> PLC–> IP3–> IP3R–> Ca2+
how many alveoli do we have?
approx 300 million
-600ft^2 surface area
each alveolus is made of
one layer of epithelial cells
type I alveolar cells
gas exchange
make up 95% of alveolar surface area
type II alveolar cells
make and secrete surfactant
surfactant
a fluid that lines all the alveoli
makes them easier to expand and prevents them from collapsing
how are the alveoli optimized for diffusion?
v thin
v little interstitial fluid
alveolus and capillary are held close together by fused basement membranes
