Lecture 28: Pulmonary Histology

Question 1

Describe the epithelium that lines the nares

Answer 1

NAres: stratified squamous epithelium continuous w/ epidermis

Mucosa begins at level of nasal septum: resp. Epithelium (pseudostratified ciliated columnar epithelium), basement membrane, and lamina propria.

Question 2

Characterize the respiratory epithelium

Answer 2

Pseudostratified ciliated columnar epithelium

Lines most of conducting structures

Question 3

Describe the changes that occur in the mucosa beginning at the level of the nasal septum and continuing through the bronchioles.

Answer 3

Stratified squamous epithelium continues w/ epidermis is transformed to resp. Epithelium. Basement membrane formed. Lamina propria

Question 4

List and describe the characteristics and functions of the cells types that make up the olfactory epithelium (sustentacular cells, basal cells, olfactory cells, and glands of bowman)

Answer 4

sustentacular cells: support cells-w/ pigment

Basal cells: routinely replaced- only cell in body. Stem cells-give rise to immature olfactory cells.mitotic

olfactory cells: bipolar neurons, GP-linked odor specific receptors.

glands of bowman: in lamina propria. secrete odorant-binding protein. Where odorant binding protein binds to odorant molecule

Question 5

Describe the kinds of tissues found in the various parts of the larynx and specify the type of epithelium found in each part of the larynx

Answer 5

Epiglottis: lingual-stratified squamous epithelium. Pharyngeal surface-pseudostratified ciliated epithelium. Core of epiglottis:elastic cartilage.

False vocal cords: pseudostratified ciliated epithelium. Lamina w/ seromucous glands.

True vocal cords: stratified squamous epithelium. Lack seromucous glands in lamina.
—*remainder is covered in pseudostratified ciliated Epithelium.

Found in larynx:

• Epithelium:resp epithelium. Stratified squamous epi.
• Cartilage: hyaline:thyroid,cricoid. Elastic:
• Muscle: skeletal

Question 6

Describe the histology of the three layers of the trachea and identify on photomicrographs.

Answer 6

Mucosa: resp. Epithelium w/ thick basement membrane. Lamina propria w/ delicate FECT and lymphatic tissue.

Submucosa: sero-mucous glands

Adventitia: 16-20 horseshoe-shaped cartilages interconnected by FECT, opening btw arms of cartilages closed by FECT, smooth muscle, mucous membrane. Mixed glands and capillaries.

Question 7

Compare the histology of each part of the respiratory passages, beginning with the bronchi through the alveolar ducts.
**

Answer 7

Bronchi: Lil’ smaller diameter than trachea. Segmental-intrapulmonary mostly. Rings become plate-like. *As bronchi, become smaller, there is a decrease in the height of the epithelium and in cartilage and glands, but a INCREASE in proportion of elastic fibers and smooth muscles. Change occurs for better gas exchange.

Bronchiole: cartilage and glands absent. Sparse goblets, much smooth muscle. Diameter is greater decreased (1mm-0.3mm). Epithelium transitions from ciliated columnar w/ few goblets to cilitaed cuboidal w/ no goblets (terminal bronchioles-smallest bronchioles, branches)-low columnar to low cuboidal. Smooth muscle w/in FECT. May have few alveolar outpocketing.

Alveolar ducts:continuations of resp. Bronchioles. Cone-shaped. Squamous epithelium. Wall=smooth-muscle w/ FECT. Alveolar sac: several alveoli.

Alveoli: w/in sacs, separated by septa, walls of alveoli and septa are thin and composed of: type 1/2 alveolar cells.

Question 8

Identify parts of the lung histology from photomicrographs

Answer 8

K

Question 9

Compare structure and function of type 1 alveolar, type 2 alveolar cells (type I pneumocytes and type II pneumocytes), neuroendocrine cells, clara cells, and dust cells.

Answer 9

Type 1 alveolar: covers largest SA. Less numerous than type 2. Very thin cytoplasm. Covers 95% of total alveolar surface. Tight junctions. Basal lamina fused w/ nearby capillaries.

Type 2 alveolar(type I and II pneumocytes): cuboidal/rounded. Stem cells for type 1and 2 pneumocytes. Contain lamellar bodies-contain lecithin. Secreted by apocal domain of cells. Phagocytize old surfactant. Cover 5% of alveolar surface. Bulge into alveolar lumen. can DIVIDE and replace type I cells.

Neuroendocrine cells: may be asso. W/ sensory reception and are more prevalent in infants. Release catecholamines.

Clara cells: secrete (lipoprotein) surfactant [w/type 2 alveolar cells]. Only in bronchioles. Also bulge apical surface into lumen of airway.

Dust cells: macrophages derived from monocytes. In CHF, breakdown of hemoglobin are phagocytized by dust cells=called heart failure cells

Question 10

Define: pore of kohn

Answer 10

Openings btw adjacent alveoli

Question 11

List the 3 components of the blood-air barrier

Answer 11

Thin capillary endothelium

Thin epithelium of pneumocyte

Intervening basal lamina produced by both cell types

This permits gas exchange but doesnt allow fluids or cells to enter alveoli.