Respiratory (Histo) Flashcards
what are the 2 major division of the respiratory system? what is each of their function?
- Conduction system: to transmit air to lower division while warming, moistening, and removing particulate matter
- Respiratory system: gas exchange between air and blood
what are the 3 major components of the nasal cavity and what is the epithelium found in each?
- Vestibule (inside nostrils) = stratified squamous epithelium, slightly keratinized
- Respiratory portion = pseudostratified columnar epithelium (respiratory epithelium) + cilia (and other cells like goblet cells)
- Olfactory mucosa = super tall pseudostratified columnar WITHOUT goblet cells
what types of cells are found in the nasal cavity epithelium in the respiratory portion?
- ciliated cells
- goblet cells
- basal cells
- neuroendocrine cells of the APUD
- brush cells
what is the function of the ciliated cells in the nasal cavity?
beat synchronously in a posterior direction (TOWARDS oral cavity) in order to move mucus secreted by the goblet cells so that the mucus can trap particulates for filtration
what is the function of goblet cells in the nasal cavity respiratory epithelium?
produce mucus which traps particulate matter
what is the function of basal cells in the nasal cavity?
precursors of other cell types (aka the regenerator cells… for regeneration of damaged/old nasal epithelium)
what is the function of the neuroendocrine cells in the nasal cavity?
secrete small granules ; they are a part of the amine precursor uptake and decarboxylation (APUD) system
what is the function of the brush cells in the nasal cavity epithelium? what structure is characteristic to their function?
have short, blunt, microvilli; function in general sensation.. give you the feeling that you need to sneeze/ticklish nose
What is found in the lamina propria of the nasal cavity ? (underlying the epithelium)
- Loose connective tissue
- Serous and mucus glands
- thin-walled venules
what is the function of the thin walled venules in the lamina propria of the nasal cavity?
warms incoming air due to the arrangement of loops which causes the air to be warmed by blood flowing through the upper parts of the loops;
where is the olfactory mucosa located?
in the roof of each nasal cavity and extends a short distance down over the superior concha and the adjacent nasal septum
describe olfactory mucosa epithelium (histology + what are the cells types)
tall pseudostratified columnar and lacks goblet cells; 4 cell types: 1. supporting (sustentacular cells) 2. basal cells 3. sensory cells 4. Brush cells
describe the the sustentacular cells of the olfactory mucosa (structure and function)
structure: tall cylindrical cells, broad at the apex and narrow at the base; have apical microvilli function : provide metabolic and physical support for olfactory cells
describe the basal cells of the olfactory mucosa (structure and function)
structure = small, conical cells with dark ovoid nuclei function = mitotically active and able to regenerate olfactory function in a few weeks
describe the structure/location of the sensory cells of the olfactory mucosa.
aka bipolar cells
location = between the sustentacular cells; soma is the middle layer of the epithelium
structure =
- spindle shaped with an apical process/ dendrtie which extends to the surface;
- termination of the apical process is in a bulb-like expansion (olfactory vesicle/knob) with 10-20 cilia
- proximal part of the cell extends into the lamina propria as an axon which continue to the olfactory bulb of the brain; the axons are clustered into unmyelinated bundles by glial ensheathing cells;
- cilia contain 350 types of odorant receptors for different odorants
describe the olfactory transduction process
odorant molecules are carried through the air to the mucus in the nasal cavity where they bind to a G-protein eliciting a secondary messenger system through cAMP .. eventually the signal is transduced and reaches the bipolar cell which takes the information to the olfactory nerve to the brain for smell perception
are the neurons of the olfactory mucosa (for smell) ever replaced?
yes; every 30-60 days
what is the function of the brush cells in the olfactory mucosa
have apical microvilli which function in general sensation; they are presynaptic to afferent fibers
Describe the lamina propria of the olfactory mucosa
contains Bowman glands and unmyelinated olfactory nerves en route to cribiform plate to terminate at olfactory bulb
what are Bowman’s glands? what do they secrete? where are they found? where do they secrete their products? ducts?
- found in the lamina propria of the olfactory mucosa;
- produce a watery secretion to trap odorants and moisten and cleanse the surface
- also secrete LYSOZYME and IgA
- deliver their secretions(proteinaceous) via ducts onto the surface of the epithelium
Describe the epithelium of the nasopharynx
lining epithelium is mostly pseudostratified ciliated columnar WITH goblet cells; cilia propel material toward the oropharynx; may be stratified squamous in areas of abrasion
describe the lamina propria of the nasopharynx
contains glands, mostly mucous; abundant lymphatic tissue including the NASOPHARYNGEAL TONSILS (adenoids)
Is there any muscle associated with the nasopharynx?
yes; the pharyngeal constrictors
what are the components of the larynx and what is their general function (ie: respiratory or mechanical).. what type of epithelium can be found in each area?
- ventricular folds = false vocal folds; involved in respiration (respiratory epithelium + mucous/serous glands)
- vocal folds = true; involved in mechanical trauma (stratified squamous epithelium non-keratinized)
Describe the mucosa of the larynx
2 parts:
- PSC respiratory epithelium typically covering the ventricular folds
- non-keratinized stratified squamous epithelium in regions of abrasion (vocal folds)
what is squamous metaplasia?
when the respiratory mucosa of the larynx (PSC epithel) changes to stratified squamous epithelium;
it is generally reversible and in areas of altered air flow, the change may persist
clinically correlated to bronchitis
Describe the components of the submucosa of the larynx
- contains MANY mucus glands, few serous glands
2. the true vocal folds contain a supporting ligament of fibroelastic CT and the skeletal muscle of the vocalis muscle
what supports the wall of the larynx?
hyaline and elastic cartilages; also CT and skeletal muscle
what maintains patency in the trachea?
the cartilagenous rings (~ 20)
describe the mucosa of the trachea
PSC epithelium with a DISTINCT basement membrane and underlying lamina propria
same 4 cells: ciliated epithelium, goblet cells, brush cells, basal cells
describe the ciliated cells of the trachea
most common; propel material UPWARD toward the pharynx in order to protect the lungs from mucus accumulation;
what is chronic bronchitis caused by? what happens in chronic bronchitis?
caused by a loss of cilila from irritation which leads to mucus accumulation in the lungs;
clinical relevance :
- respiratory epithelium changes to stratified squamous epithelim (squamous metaplasia), but the stratified squamous epithelium is not as functionally efficient
- loss of cilia
- removal of mucus is impaired
- coughing as a compensatory means to expel accumulated mucus
- overtime, the number of ciliated cells continuous to DECREASE significantly (cycle can be repeated!)
where are the granules of the neuroendocrine cells located in the trachea? why is there location significant?
located basally and are released into the underlying connective tissue where they provide local regulatory control
what type of granules do the neuroendocrine cells of the trachea contain? what do they produce?
produce biogenic amines (serotonin from 5-hydroxytryptophan) contain neuropeptides (bobesin, calcitonin, enkephalin, calcitonin gene-regulated peptide, somatostatin
describe the submucosa of the trachea; how is the submucosa separated from the mucosa layer?
loose CT with mixed serous and mucous glands, lymphatic tissue is also present;
separated from the mucosa via aband of ELASTIC tissue
Describe the structure of the cartilagenous layer of the trachea; what is its primary function
function = maintain patency of the tracheal tube structure = 20 "C-shaped" hyaline cartilages which have the open part of the C POSTERIORLY; they are connected to adjacent cartilagenous rings via fibro-elastic connective tissue which blends with their perichondrium
what is located external to the tracheal cartilages? what does it contain?
adventitia; contains CT, blood vessels, and nerves
How many generations of branching occurs in the bronchi?
10
what are extrapulomnary bronchi? how do they differ from the trachea?
aka the right and left primary bronchi; they are branches that ARE NOT confined within the lung lobes; differ from the trachea only in diameter
What are intrapulmonary bronchi? how many are located in each lung (rt/left)
bronchi located within the lung;
right lung = 3 secondary bronchi; each serving one of the lobes
left lung = 2 secondary bronchi
what supplies the bronchopulmonary segments? how many are in the right lobe? left lobe? how are they separated?
supplied by tertiary segmental bronchi;
right lobe = 10 bronchopulmonary segments
left lobe = 8-10
beach bronchopulmonary segment is separated via a layer of CT and thus provides a discrete anatomical and functional unit
how does the intrapulomnary bronchi differ from the extrapulmonary bronchi/trachea?
in the intrapulmonary:
- epithelium is initially PSC but CHANGES to cililated COLUMNAR with goblet cells (cilia moves material upward and out of the lungs)
- Interlacing bundles of smooth mucles (muscularis mucosae) are added to the mucosa at the border with the submucosa
what are the layers of the intrapulmonary bronchi?
- mucosa (with muscularis mucosae)
- submucosa (with glands)
- cartilagenous layer
- adventitia
what happens to the cartilagenous plates in the intrapulmonary bronchi?
no longer C-shaped… the bronchi increase in branching and thus decrease in diameter and then you get an increase in the number of plates but a decrease in the plate size (just like plate bits)
what defines bronchioles?
air passageways of 1 mm or less in diameter; they exhibit 10 generations of branching
what is characteristic of the bronchiole wall?
thin; no cartilage and no submucosal glands; relatively more smooth muscle
Describe the bronchiolar epithelium (and the cells)
SIMPLE columnar or cuboidal;
cells =
1. ciliated cells
2. goblet cells (decrease in number as branching continues)
3. Clara cells (noncilated bronchiolar cells)
4. basal, brush, an dsmall granule cells
what are clara cells? describe their histology
noncilated bronchiolar cells; dome shaped apical margin; have the appearance of typical protein-secretory cells (rER, golgi, secretory granules)
what is the function of clara cells?
- secrete one of the components of surfactant which prevents luminal adhesion (atelectesis)
- synthesis of Clara cell protein CC16 which is a measurable pulmonary marker
- involves in Cl transport into the lumen which aids in keeping the luminal surface moist
- act as reserve cells from damaged cells
- can detoxify noxious substances
what is CC16
a measurable pulmonary marker protein in the clara cell
what occurs if the Cl- transport is defected in a clara cell?
cystic fibrosis
what type of fibers does the lamina propria of the bronchioles contain?
elastic fibers
what happens to the muscularis mucosa in the bronchioles?
it increases and is surrounded by the CT of adventitia
what is a terminal bronchiole
- smallest branch of the conducting division
- defines a pulmonary lobule
- they further divide into 3 generations of respiratory bronchioles and they associated alveolar ducts
what is a respiratory bronchiole?
the smallest function unit of lung (a pulmonary acinus or respiratory bronchiolar unit)
IT IS THE FIRST SITE OF GAS EXCHANGE
what type of epithelium is found in the respiratory bronchiole?
lining epithelium is cuboidal with occasional ciliated cells, but MOSTLY CLARA CELLS
describe the lamina propria of the respiratory bronchiole
contains elastic fibers which are vulnerable to destruction by elastases and proteases from neutrophils
what gives rise to emphysema? what is emphysema characterized by?
emphysema results from: loss of elasticity of the lamina propria
characterized by: enlarged inter-alveolar airspaces which causes a decrease in the area available for gas exchange and thus efficiency of gas exchange is compromised
what are alveolar ducts?
thin walled tubes lined with bronchiolar cells;
what is found in the external wall of alveolar ducts?
fibroelastic CT with intermittant bundles of smooth muscle
what are alveoli?
the terminal air spaces of the respiratory system and the SITE OF GAS EXCHANGE BETWEEN AIR AND BLOOD!!!
what separates of the alveoli?
a thin interalveolar septae of delicate CT with collagen, elastic and reticular fibers + CAPILLARIES
what allows air to pass between alveoli?
alveolar pores (pores of Kohn)
what are the capillaries of the alveolar wall enmeshed with?
elastin + fine collagen fibers
what provides collateral air circulation should a bronchiole be obstructed?
pores; they allow for equalization of pressure between alveoli
what cells lines the alveoli wall? what is their function? what percent of the surface to they cover?
squamous alveolar cells aka type I pneunmocyte; function: freely permeable to gases; cover 95% of the surface
what are great alveolar cells? what percent of the surface of the alveoli do they cover? what are they joined to? how?
aka type II pneumocyte;
joined to type I pneumocyte via zonula occludens;
cover only 5% of the alveoli surface
what is the function of cytosomes? where are they found?
found in type II pneumocytes;
they are rich in phospholipids and are discharges into the alveolar lumen where they function as part of the surfactant system
what is the function of type II pneumocytes?
incroporate large amounts of choline as they synthesize phosphatidyl-choline which is the major component (40%) of surfactant.. to reduce surface tension and is thus essential for maintaining patency of the alveolli
what does surfactant consist of? what is its functioN?
phosphatidyl -choline = 40% cholesteral = 50% 4 proteins (SP-A SP-B SP-C SP-D)
what is the function of SP-A SP-B SP-C SP-D?
stabilize the surfactnant and contribute to immue response
what happens if a premature infant is surfactant deficient?
leads to collapse of alveoli (atelectasis) and is complicated by seepage of FIBRIN and other proteins from the capillaries into the air spaces forming a hyaline membrane
what does type II pneumocyte proliferate into?
type I or type II pneumocytes
do type I pneumocytes regenerate?
NO
what are alveolar macophages? where are they found?
found within the inter-alveolar septum and migrate along the luminal surface of the airway;
they are very phagocytic and very motile
what is the function of the alveolar macrophages?
continuously produce lysosomal enzymes
are there any fibroblasts in the alveoli?
a few in the interalvolar septume to produce collagen fibers and elastic fibers
where, specifically, does gas exchange occur?
at the thinnest portion of the junction between type I pneumocytes and endothelial of the capillary
what is found at the alveolar membrane (barrier/junction where gas exchange occurs)?
- surfactant (overlaying the barrier
- type I alveolar cell
- basal lamina of type I alveolar cell
- basal lamina of capillary endothelial cells (the two basal laminae often fuse)
- capillary endothelial cell
**1-3 function in maintaining patency
where does fluid exchange occur in alveolar membrane?
at the portions where cells are thicker and the basal laminae are not fused
what is pleura?
mesothelium covering the lungs
where are the pulmonary/bronchial arteries located wtih respect to the the bronchial tree?
accompany
where do arteries give rise to the capillary plexus in the respiratory system?
at the level of the alveolar ducts
where do veins course in the lungs?
in the septae
