Respiratory Tract Histology Flashcards
there are two different portions of the respiratory tract. what are they?
the conducting portion and the respiratory portion
what makes up the conducting portion?
air passages that lead to the sites of respiration within the lungs where gas exchange takes place; the nasal cavity, paranasal sinuses, nasopharynx, larynx, trachea; primary, secondary, and tertiary bronchi, and bronchioles and terminal bronchioles
what makes up the respiratory portion of the respiratory tract?
respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli
what cell types make up the respiratory epithelium?
ciliated, columnar epithelial cells; goblet cells, brush cells, and small granule cells
what are brush cells/ what is their purpose?
they have short blunt microvilli; they act as chemosensory cells that are connected to sensory nerve fibers
what are small granule cells?
they resemble basal cells, but they have secretory granules; they are endocrine cells of the DNES
what are basal cells?
they are non-ciliated stem cells that line on the basement membrane
there are three regions associated with the nasal cavity. What are they?
nasal vestibule, respiratory region, and the olfactory region
what is the nasal vestibule?
it is just inside the nostrils, lined by skin
what is the respiratory region?
it is the inferior 2/3 of the nasal cavities lined with respiratory mucosa
what is the olfactory region?
it is located at the apex (upper 1/3), lined by specialized olfactory mucosa
what is the role of the nasal cavity?
it adjusts temperature and humidity of inspired air- this is enhanced by the large surface area that is provided by the turbinate bones
what are the paranasal sinuses?
air-filled spaces in the bones of the walls of the nasal cavity
what are the paranasal sinuses lined by?
respiratory epithelium
how do the paranasal sinuses communicate with the nasal cavities?
via narrow openings onto the respiratory mucosa
what is the epithelium that makes up the nasal vestibule?
skin- so keratinized stratified squamous epithelium
what is the epithelium that makes up the respiratory region of the nasal cavity posterior to the vestibule?
pseudostratified columnar ciliated epithelium (aka respiratory epithelium)
how is the olfactory mucosa different than the rest of the respiratory mucosa in the nasal cavities?
it is dramatically thicker and it lacks goblet cells; it also has nonmotile cilia
what glands are found in the olfactory mucosa?
olfactory (bowman’s) glands- produce a serous secretion that dissolve odorant molecules
what nervous tissue is found within the olfactory mucosa?
olfactory receptor neurons (ORNs)
what type of epithelia are brush cells?
ciliated columnar epithelial cells
what are sustentacular cells and where are they found?
found in the olfactory mucosa; they provide mechanical and metabolic support to ORNs
what is the larynx?
a short passage for air between the pharynx and the trachea
what is the larynx comprised of?
numerous pieces of cartilage
what do movements of the larynx involve and for what reason?
they involve skeletal muscle- produces phonation
what types of cartilage is found in the larynx?
hyaline cartilage and elastic cartilage
what types of cartilage make up the hyaline cartilage?
thyroid, cricoid, and inferior arytenoid cartilages
what types of cartilage make up the elastic cartilage?
epiglottis, cuneiform, corniculate, and superior arytenoid cartilages
what is the biggest piece of cartilage that we have (related to our airways)?
the epiglottis
what is the purpose of the epiglottis?
it prevents swallowed food/fluid from entering the air ways
what makes up the core of the epiglottis?
elastic cartilage
what is the lingual surface of the epiglottis made up of?
stratified squamous epithelium
what is the laryngeal surface of the epiglottis made up of?
transitions to ciliated pseudostratified columnar epithelium
what glands are found in the lamina propria beneath the epithelium of the epiglottis?
mixed mucous and serous glands
what folds are found in the larynx?
vestibular and vocal folds
what are vestibular folds?
respiratory epithelium with seromucous glands and lymphoid nodules; superior pair and immovable
what are the vocal folds?
the inferior pair of folds; covered with nonkeratinized stratified squamous epithelium
what supports the free edge of each vocal fold?
a dense regular bundle of elastic connective tissue, known as the vocal ligament
what causes laryngitis?
edema of the lamina propria changes the shape of the vocal folds which causes the hoarseness/loss of voice
what causes croup?
edema of laryngeal mucosa cause hoarseness and loud harsh coughs
what is the trachea?
a short flexible air tube that extends from the larynx and divides into the main/primary bronchi
how does the lumen of the trachea remain open?
because of the stacked hyaline cartilaginous rings
the cartilaginous rings are incomplete at the posterior surface; what connects the two open ends of the cartilaginous ring?
the trachealis muscle (smooth muscle)
what is the lamina propria of the trachea rich with?
elastic fibers, goblet cells, and BALT
what does the submucosa of the trachea house?
incomplete rings of hyaline cartilage; rich in submucosal glands
the trachea branches into main/primary bronchi. Where do these enter the lung?
at the hilum- along with the arteries, veins, and lymphatic vessels
what happens to the mucosa of the bronchi?
you still have pseudostratified ciliated columnar epithelia, but the cells get shorter in height and there are fewer goblet cells
what can be said about the cartilaginous rings that are found in the primary bronchi?
they are complete- these will gradually be replaced with plates of hyaline cartilage as the lumen size decreases
what does the lamina propria of the bronchi contain?
spiral bundles of smooth muscle and increasingly prominent elastic fibers
what are the bronchioles?
they arise from the terminal branches of tertiary bronchi
what do the bronchioles enter?
a pulmonary lobule, where it branches to form 5-7 terminal bronchioles
what is the mucosa of larger bronchioles?
pseduostratified ciliated columnar epithlium
as the lumen of the bronchioles decreases in size, the mucosa with transition. what is the first thing the pseudostratified ciliated columnar epithelium will transition into?
ciliated simple columnar epithelium
what does the ciliated simple columnar epithelium transition into?
simple cuboidal epithelium
what is the mucosa of the terminal bronchioles?
simple cuboidal epithelium, no mucosal glands, and NO cartilage
what do the bronchioles lack?
they have no mucosal glands, no cartilage, and no submucosa
what is the muscularis layer of the bronchioles?
a prominent smooth muscle associated with a dense connective tissue
what is the hallmark of bronchioles?
no cartilage, no glands, the change in the mucosa, and the increasing amount of smooth muscle
what occurs during asthma?
there is recurrent obstruction of airflow due to bronchiole inflammation and smooth muscle constriction (bronchospasm)
in asthmatic patients, what is there an infiltration of and where?
there is an infiltration of the bronchiolar wall by eosinophils, lymphocytes, and mast cells
what does the simple cuboidal epithelium of the terminal bronchioles consist largely of?
club cells
what do club cells look like?
non-ciliated, dome-shaped apical ends containing secretory granules
the granules in the club cells give the terminal bronchioles an exocrine function. How so?
they will secrete surfactant, which is a combination of lipoproteins and mucins, onto the epithelial surface; they are involved in detoxification of inhaled compounds; and they are responsible for secretion of antimicrobial peptides
besides club cells, what other cell populations are found in the terminal bronchioles?
brush cells, DNES small granule cells, and stem cells
what do the terminal bronchioles branch and give way to?
the respiratory bronchioles- the transition point for moving from the conducting portion of the respiratory system to the respiratory portion
what do the respiratory bronchioles always end in?
alveoli
what are respiratory bronchiles lined with?
a simple cuboidal epithelium with elastic fibers and smooth muscle
what do respiratory bronchioles branch into?
into alveolar ducts, which then branch into alveolar sacs, which then eventually give way to individual alveoli
what are the alveolar ducts completely lined by?
the openings of the alveoli; lined with attenuated squamous cells
how is an alveolar sac defined?
clusters of 2+ alveoli, form the ends of the alveolar ducts distally
what are alveoli?
saclike evaginations from the respiratory bronchioles, alveolar ducts, and alveolar sacs
what are alveolar rings?
aggregates of smooth muscle, collagen, and elastic fibers that form rings around the alveolar ducts; help to hold the ducts open
what are alveoli lined with?
simple squamous epithelium with supporting tissue and blood vessels
what are alveolar pores?
small openings that permit the movement of air between alveoli
what is found between the alveoli?
the interalveolar septum
what are the two different cell types that are found within the alveoli?
type 1 and type 2 pneumocytes (aka type 1 and type 2 alveolar cells) and alveolar macrophages (dust cells)
what are the type 1 alveolar cells?
squamous cells that line almost the entire alveolus surface; participate in gas exchange
what are the type 2 alveolar cells?
they line portions of each alveolus, they are large and rounded cells, often bulging into the alveolus; they have many functions similar to club cells, such as producing surfactant
what separates the air in the alveoli from the capillary blood?
the respiratory membrane or the blood-air-barrier
what three components make up the respiratory membrane/ blood-air-barrier?
two/three highly attenuated thin cells lining the alveolus (type 1 alveolar cells), fused basal laminae of these cells and the capillary endothelium, and thin, endothelial capillary cells
where (very very specific) does gas exchange/ diffusion take place?
the respiratory membrane
what is emphysema?
permanent enlargement of air spaces distal to the terminal bronchiole
what causes emphysema?
chronic obstruction of airflow due to narrowing of bronchioles; accompanied by destruction of the alveolar wall
what is lost in emphysema?
a significant area for gas exchange
what is pneumonia?
inflammation of the lung tissue; air spaces are filled with exudate containing WBCs (mainly neutrophils), RBCs, and fibrin; enlarged capillaries
