Lecture 21: Macro- and Micro-Structure of the Lungs Flashcards
lobes of lungs
right upper, middle lower
left upper, lower
fissures of lungs
oblique fissures (2) - separate L/R upper/lower lobes
horizontal fissure - RIGHT only; divides R middle lobe
why no left middle lobe of lungs?
because need space for the heart
lung lymphatics
lymphatic channels, appear as little white lines, unless have carbon pigment within visceral pleural lymphatic channels, then appear black
channel lymph fluid through lungs, towards hilum (root of lung) and to mediastinal lymph nodes (toward midline of body)
pleura
single layer of mesothelial cells
visceral layer of pleura
layer of connective tissue over surface of lung
parietal layer of pleura
layer of connective tissue against thoracic wall
neumothroax/hemothorax
when visceral and parietal layers dissociate because of air/blood entry into lungs
does lung feel a puncture from inside?
no
if tear parietal pleura, nerve that detects pain/causes action?
intercostal and phrenic afferent nerves perceive pain
GSA pain results
if tear visceral pleura, nerve that detects pain/causes action?
vagus and sympathetics perceive pain
little/no GVA pain results
what does vagus nerve control innervation for in lungs?
changes in: smooth muscle (stretch); muscosa of trachea and bronchi (irritation); C pain fibers in alveoli and bronchi (inflammation); pulmonary veins, cardiac plexus (chemical); aortic arch and wall, pulmonary arteries (pressure)
where does vagus nerve run re: T-E?
posterior to hilum of lung; on either side of esophagus and trachea
hilum
root of lung, where structures (bronchus, artery, vein) enter/leave
what type of fibers do phrenic nerves carry to diaphragm?
GSE fibers
where does phrenic nerve run?
anterior to hilum of lung
what kind of blood does pulmonary artery carry?
deoxygenated blood
originate from pulmonary trunk, go to lungs from R ventricle of heart
what kind of blood does pulmonary vein carry?
oxygenated blood
where does pulmonary trunk bifurcation occur?
to left of midline, just inferior to vertebral level TIV/V
what is longer- right or left pulmonary artery?
right
order of bronchus/artery/vein at hilum of lung
left: are brides vain? - artery, bronchus, vein
right: brides are vein - bronchus, artery, vein
bronchial arteries
part of lung’s dual blood supply system
arise from aorta, intercostal arteries, or subclavian arteries
enter lungs at hilum
are nutrient arteries supplying oxygenated blood to tissue
pulmonary arteries
follow bronchial tree to form capillaries around alveoli
provide deoxygenated blood to lungs
2 types of arteries that supply blood to lungs
bronchial arteries, pulmonary arteries
where bronchial veins drain
pulmonary veins or left atrium, and into azygos vein on R and superior intercostal vein/meiazygos vein on L
tracheobroncial tree divisions
trachea > intrapulmonary brunchs > main (primary > lobar (secondary) > segmental (tertiary) > bronchioles
divisions smaller than bronchioles bronchioles
terminal bronchiole, respiratory bronchiole, alveolar duct, alveolar sac, alveolus
bronchogram
old image of bronchiole tree, taken by having pt ingest metal dust
carina
cartilaginous ridge within trachea, runs between the 2 primary bronchi of the trachea where they bifurcate
bronchoscopy
image down trachea into 2 main bronchi
cell type in trachea
pseudo stratified ciliated columnar
layers from out > in of the trachea
adventitia, C-shaped rings, trachealis and longitudinal muscles, submucosa, mucosa
adventitia
connective tissue on outside of trachea
c-shaped rings of trachea
hyaline cartilage that’s incomplete dorsally
tracheal is and longitudinal
smooth muscles of trachea
submucosa
mucous and serous glands of trachea
mucosa of trachea
made of epithelium and lamina propria
epithelium of trachea
pseudo stratified ciliated columnar & goblet cells (produce mucus)
lamina propria of trachea
connective tissue, elastic fibers
how many layers of respiratory epithelium in trachea?
1! just appears to be more because pseudo stratified
cilia function in trachea
bring fluid from lungs to trachea, so can get rid of bacteria/other particles not desired in the lungs
2 other cell types of respiratory epithelium
endocrine (kulchisky) cells- secrete serotonin, regulate airway reflexes; basal cells (not columnar)- will give rise to epithelia
orientations of mainstem bronchi
right is more vertical than left; inhaled objects thus tend to lodge in right mainstem bronchus
intrapulmonary bronchus
usually next to branch of pulmonary artery, irregular cartilage plates, smooth muscle, goblet cells, ciliated pseudo stratified columnar epithelium, transitions to ciliated simple columnar as bronchi get smaller
broncho-pulmonary segment
area of lung supplied by a segmental bronchus and its accompanying pulmonary artery branch
smallest functionally independent region of a lung and smallest area of lung that can be isolated/removed without affect adjacent regions
secondary/tertiary bronchi travel alongside, and branch in parallel with, pulmonary arteries/arterioles
10 in each lung
bronchiole
really thin epithelium so can have gas exchange with alveoli
characterized by no cartilage, smooth muscle, very few/no goblet cells, and epithelium transfers from ciliated simple columnar to ciliated simple cuboidal
4 F’s of sympathetic innervation
fright, flight, fight, fornicate
autonomic innervation of bronchial glands
sympathetic: inhibitory - make lumens BIG
parasympathetic (vagus): secretomotor
autonomic innervation of bronchial smooth muscle
sympathetic: bronchodilation
parasympathetic (vagus): bronchoconstriction
autonomic innervation of bronchial vasculature
sympathetic: vasoconstriction
parasympathetic: vasodialation
why is it good to have a large diameter lumen in the bronchi/bronchioles?
no gas exchange
autonomic innervation to alveolar vasculature
none! they are capillaries, controlled by locally circulating factors like histamine, not by nervous system
sympathetics control in lungs
secretory inhibition, bronchodilation, vasoconstriction
parasympathetics control in lungs
secretomotor, bronchoconstriction, vasodilation
COPD and asthma
chronic obstructive pulmonary disease and asthma
may have abnormally high parasympathetic discharge and flow of air through bronchi, and inflammation
L/R vagus orientations re: esophagus
left: anterior
right: posterior
posterior pulmonary plexus
come off of vagus; sit on top of esophagus; eventually provide PARASYMPATHETIC innervation to lungs
where does parasympathetic innervation to the lungs come from?
pulmonary plexus
where does sympathetic innervation to the lungs come from?
sympathetic chain
terminal bronchiole characteristics
biggest of microstructures
surrounded by layer of smooth muscle, no goblet cells, ciliated simple cuboidal epithelium, clara cells
clara cells
precursors of bronchiolar epithelial cells
detoxify carcinogens, synthesize a surfactant-like protein, secrete alpha-1-antitrypsin which inhibits digestion of elastin
have secretory vesicles, no cilia
emphysema
caused by elastic tissue breakdown
can be caused by breakdown of clara cells
what does alveolar wall contain?
elastic tissue (elastin)
acinus (pl=acini)
functional subunit of the lung supplied by a single respiratory bronchiole
subdivisions from bronchus to alveolus
bronchus, respiratory bronchiole, alveolar duct, alveolar sac, alveolus
respiratory bronchiole characteristics
simple cuboidal epithelium, wall punctuated by alveoli and smooth muscle; isn’t smooth anymore, has potholes in it with lumps of smooth muscle
alveolar duct characteristics
wall punctuated by alveolar sacs and alveoli
alveolar sac characteristics
terminal part of alveolar duct, alveolar clusters = alveolar sac
alveolar capillaries
seen inside of alveolar sac
can fit 1 RBC through
cell types in capillary walls / function
function: more surface area for gas exchange
cells:
type I alveolar cell, capillary endothelial cell
blood-air barrier for gas exchange made of
simple squamous epithelium
direct exchange from endothelial cell to alveolar cell
cell types in alveolar wall cells
endothelial cells,
type I pneumocytes,
type II pneumocytes
characteristics of endothelial cells in alveolar wall cells
thin, flat
do gas exchange
characteristics of type I pneumocyte cells in alveolar wall cells
thin, flat
do gas exchange
only 40% of alveolar cells
cover 90% surface of alveoli
characteristics of type II pneumocyte cells in alveolar wall cells
thick, protruding, "foamy" no gas exchange 60% alveolar cells replace damaged type I cells secrete surfactant
what type of cell secretes surfactant?
type II pneumocyte
what is alveolar surface area equal to?
tennis court!
lamellar bodies
secretory vesicles that produce surfactant in type II pneumocytes
produce it in form of tubular myelin weaves
look like little jupiters
surfactant characteristics
phospholipids, cholesterol, carbs, proteins
decreases alveolar surface tension
keeps cell surface water layer thin, so increases gas exchange
increases stretchability (compliance)
prevents alveolar collapse
reduces fluid flow from capillaries into airways
what does low surfactant levels cause?
respiratory distress syndrome
ie in premature babies
pore of kohn
alveolar pores
allow equalization of pressure between alveoli, facilitate flow between acini when bronchioles are blocked
is it good to have surfactant in alveolar pores?
no; blocks communication between alveoli
alveolar macrophages
phagocytyze extra surfactant
aka “dust cells” because ingest inhaled particulate matter
what is rate that lungs can recruit alveolar macrophages?
1 million macrophages/hr!
characteristics of smoker’s lungs
excess carbon particles (trapped in macrophages)
chronic bronchitis (excess mucus from goblet cells)
increased pneumonia risk
loss of elasticity (emphysema, fibrosis)
metaplasia (bronchi epithelium changes to stratified squamous), interstitial disease (thickened alveolar walls)
cancer
cell type of trachea and mainstem bronchus
ciliated pseudo stratified columnar
cell type of intrapulmonary bronchus
transitions
cell type of broncho-pulmonary segment
ciliated simple columnar
cell type of bronchiole
transitions
cell type of terminal bronchiole
ciliated simple cuboidal
cell type of respiratory bronchiole
simple cuboidal
cell type of alveolus
simple squamous
