Pulmonary Histology Flashcards
The respiratory system consists of a ______ portion and a _____ portion
Conducting, gas exchange
Respiratory mucosa lines the respiratory passageway and consists of
- Pseudostratified ciliated columnar epithelium:
- Respiratory epithelium
- Lines most of conducting structures
- Lamina propria
- Thin layer of loose CT
- Submucosa
- Dense irregular CT
Respiratory epithelium structure
Pseudostratified ciliated columnar epithelium
The lamina propria of respiratory mucosa is
thin layer of loose CT
The submucosa of respiratory system
dense irregular CT
Respiratory epithelium lines
most of the conducting structures
Epithelium of the nares/Nostrils composition
- Stratified squamous epithelium continuous with epidermis
- Contains sebaceous glands, sudoriferous glands, and hair follicles
Respiratory/nasal mucosa begins where in the nose
at the level of nasal septum
Nasal mucosa includes:
- Respiratory epithelium
- basement membrane
- Lamina propria (blends with underlying bone or cartilage)
- Depending on location, mucosa may be called mucoperiosteum, mucoperichondrium, or the Schneiderian membrane)
Where is olfactory epithelium located
in the nasal cavity roof
composition of olfactory epithelium
- pseudostratified columnar epithelium without goblet cells
- no distinct basement membrane
Cell of olfactory epithelium
- Sustentacular cells (supporting cells) with pigment granules
- basal cells with pigment granules:
- Stem cells-give rise to immature olfactory cells
- Olfactory cells:
- Bipolar neurons
- Apical end projects into nasal cavity as a knoblike ending with nonmotile cilia
- Cilia possess G-protein-linked odor-specific receptors
- Basal end of the cell extends as an unmyelinated axon, bundled with other similar axons, through the ethmoid plate to mitral cells located in the olfactory bulb
- Olfactory cells senesce and are replaced from basal cells
- olfactory glands of bowman:
Where are olfactory glands of bowman located
in the lamina propria of olfactory mucosa
What do olfactory glands of bowman secrete
odorant-binding protein, which binds to odorant molecule in nasal cavity
Generation of AP in Olfactory system
odorant-binding protein+ odorant molecules—> binds to odorant receptor protein (G protein) on olfactory cell cilium—> G-protein activated adenyl cyclase—> G-protein activated adenyl with ATP —-> cAMP—> Opening of Na+ channels —-> AP
What are the only neurons that can repopulate
Olfactory cells
mucosa of the nasopharynx
- Respiratory epithelium
- Lamina propria with FECT, mucous glands, serous and mixed glands, and diffuse lymphatic tissue
Submucosa of Nasopharynx
- Loose CT
- MALT (mucosa-associated lymphoid tissue)
What is Waldeyer’s ring
- Located in the Nasopharynx
- Ring of lymphoid tissue around nasopharynx
- Includes Tonsils and Adenoids
What is FECT
Fibrous-elastic Connective Tissue
Histology of the Larynx components
Epiglottis
False vocal cords (vestibular folds)
True vocal cords
- Remainder of the larynx is covered with pseudostratified ciliated epithelium
Epiglottis
- sits above the opening to the trachea
- Lingual surface: covered with stratified squamous epithelium
- Lamina propria with loose CT and elastic fibers
- Pharyngeal surface:
- Covered with pseudostratied ciliated epithelium
- Lamina propria with tubuloacinar seromucous glands
- Core of the epiglottis consists of elastic cartilage
False vocal cords (vestibular folds)
- Covered with pseudostratified ciliated epithelium
- Lamina with seromucous glands
True vocal cords
- Covered with stratified squamous epithelium
- Lack seromucous glands in lamina propria
Tissues found in the layrnx
- Epithelium
- Respiratory epithelium (pseudostratified ciliated columnar)
- Stratified squamous epithelium (in 2 places)
- Cartilage
- Hyaline cartilages:
- Thyroid, cricoid, arytenoids
- Elastic cartilages:
- Corniculates, cuneiforms, tips of arytenoids, epiglottis
- Hyaline cartilages:
- Muscle
- Skeletal muscle
Composition of the Trachea
- Mucosa:
- Respiratory epithelium with thick basement membrane
- Lamina propria with delicate FECT and lymphatic tissue
- Submucosa
- many sero-mucous glands
- Adventitia
- 16-20 horseshoe-shaped cartilages interconnected by FECT
- opening between arms of horseshoe-shaped cartilages closed by: FECT, Mucous membrane, and smooth muscles (Trachealis muscles)
- mixed glands and capillaries
The right lung has how many lobes
3
Lungs refers to
all respiratory system components distal to the trachea
each lobe of the lung is divided into a number of lobules called
bronchopulmonary segments
The trachea divides into ____ primary bronchi
two, one to each lung
Each primary bronchus divides into _____ (to the right lung) or____ (to the left lung) secondary bronchi, also referred to as segmental bronchi
3, 2
each bronchus divide into
secondary bronchi, also referred to as segmental bronchi
The primary bronchi lie
outside the lung and are referred to as extrapulmonary
The bronchi resemble the trachea except
for a smaller diameter, and the cartilage ring that reinforces them are circular rather than horseshoe-shaped
Segmental bronchi are mostly
intrapulmonary
Secondary/segmental bronchi are reinforced by
circular rings of hyaline cartilage that transition to irregular plates
As the bronchi become smaller there is a ________ in height of the epithelium, a _______ in cartilage and glands, and an ______ in the proportion of elastic fibers and smooth muscles
decrease, decrease, increase
General histology of the intrapulmonary bronchi
- Mucosa
- Similar to trachea and extrapulmonary bronchi
- mucosal folds may be present due to smooth muscles
- Elastic fibers are prominent
- Submucosa
- Characterized by loose CT and lymphatic tissue
- Contains mixed glands and mucous glands
- Adventitia
- Contains hyaline cartilage plates surrounded by dense FECT
General characteristic of bronchioles
- Absence of cartilage
- Absence of glands
- Sparse goblet cells, especially in terminal bronchioles
- Large amount of smooth muscle tissue
- Diameter ranges from 1 mm to about 0.3 mm
- Epithelium transitions form ciliated columnar with a few goblet cells to ciliated cuboidal with no goblet cells (terminal bronchioles)
- Smallest brochioles are the terminal bronchioles
- Each terminal bronchiole branches to form two or more respiratory bronchioles
general characteristic of respiratory bronchioles
-Diameter
Alveolar ducts
- continuations of respiratory bronchioles
- cone-shaped
- squamous epithelium
- Wall consists of smooth muscle with FECT
Alveolar sacs
each sac is composed of several alveoli
Alveoli within alveolar sacs are separated by
alveolar septa
Walls of the alveoli and septa are thin and composed of
- Type I alveolar cells (type I pneumocytes)
- less numerous than type II alveolar cells
- Cover larges surface area
- Type II alveolar cells (type II pneumocytes)
- Cuboidal or rounded
- Serve as stem cells for type I and type II pneumocytes
- Macrophages (dust cells)
What are the pores of Kohn
openings between adjacent alveoli
Cell types in the respiratory epithelium and alveoli
- Ciliated columnar cells
- Nonciliated columnar cells
- have microvilli but no cilia
- Stem cells
- Basal cells of pseudostratified epithelium
- Replace themselves
- Goblet cells
- Mucous secreting cells
- Also stem cells; can replace other cells of epithelium
- Neuroendocrine cells (small granule cells)
- May be associated with sensory reception and are more prevalent in infant
- Release catecholamines
neuroendocrine cells (small granule cells)
- may be associated with sensory reception and are more prevalent in infants
- release catecholamines
Surfactant is secreted by
Clara cells and type II alveolar cells
Type II alveolar cells contain numerous
lamellar bodies
what is the function of surfactant
reduces surface tension on alveolar surface
Type II alveolar phagocytize
old surfactant
Type II alveolar cells contain numerous lamellar bodies, which
- are distinctive under EM
- Contain dipalmitoyl phosphatidylcholine (lecithin)
- secreted from apical domain of cells
- combine with proteins from clara cells
Type I pneumocytes (alveolar cells)
- very thin cytoplasm
- cover about 95% of the alveolar surface
- tight junctions connect with other type I cells
- Basal lamina may be fused with basal lamina of nearby capillaries
Type II pneumocytes (alveolar cells)
- Rounded cells that bulge into the alveolar lumen
- Cover about 5% of the alveolar surface
- Can divide and replace type I pneumocytes
- Produce phospholipid-protein surfactant that coats alveolar walls
Type II pneumocytes (alveolar cells ) produce
phospholipid-protein surfactant that coats alveolar walls
explain how odors lead to action potential
(odorant-binding protein + odorant molecule) —–> binds to odorant receptor protein (G protein) on olfactory cell cilium ——> G-Protein activated adenyl cyclase——- turns ATP to cAMP——–> opens Na+ channels ——-> Action potential
Clara cells are only found in the
bronchioles
The number of Clara Cells in the bronchioles increases as
ciliated columnar cells decrease
What is the Histological identification characteristic of Clara Cells
can be identified by an apical surface that bulges into the lumen of the airway
Clara cells function
secrete surface-active lipoprotein that prevents collapse of terminal bronchioles during exhalation (surfactant)
Do Clara cells contain abundant SER
Yes
Dust cells are _____ and are derived from ____-
Macrophages, derived from monocytes
Function of dust cells
phagocytize particles such as pollutants, bacteria, and surfactant that are not trapped in the mucous and expectorated
What is the relation of dust cells to CHF (congestive heart failure)
- in CHF, fluid containing the breakdown products of hemoglobin (iron-containing hemosiderin) leak into alveolar spaces and are phagocytize by dust cells
- the iron-containing dust cells are referred to as heart failure cells
Iron-containing dust cells are referred to as
heart failure cells
List the components of the air-blood respiratory barrier
- Thin capillary endothelium (continuous endothelium)
- Thin epithelium of pneumocyte (type I)
- intervening basal lamina produced by both cell types
function(s) of blood-air barrier
permits gas exchange but does not allow fluids or cells to enter alveoli (normally)
