Ciliated Cells

Of the 5 Respiratory epithelium cell types, the most abudant.

Contact the basement membrane and reach the free surface. They have many cilia and short microvilli on their surface. Tall columnar in larger bronchi, cuboidal in periphery.

Ciliated Cells

Of the 5 Respiratory epithelium cell types, the most abudant.

Contact the basement membrane and reach the free surface. They have many cilia and short microvilli on their surface. Tall columnar in larger bronchi, cuboidal in periphery.

Goblet cells - one of the 5 Respiratory type epithelial cells

Secrete mucus in packets; diminish in number as the tracheobronchial tree approaches the respiatory bronchioles;

absent in terminal bronchioles

Goblet cells - one of the 5 Respiratory type epithelial cells

Secrete mucus in packets; diminish in number as the tracheobronchial tree approaches the respiatory bronchioles;

absent in terminal bronchioles

Neuroendocrine cell - one of the 5 Respiratory type epithelial cells

Physical: On EM have the characteristic 'dense core' granules of neuroendocrine cells; small round cells located on the basement membrane

Function: produce a wide variety of hormones including serotonin, dopamine, somatostatin

Brush cells - one of the 5 respiratory type epithelial cells

have microvilli on their free surface;

sensory nerves contact their basal surface

Basal cells - one of the 5 respiratory type epithelial cells

Reserve (progenitor) cells that can differentiate to become the other cell types;

Only contact the basement membrane; do not reach the lumen

Clara cells - (Bronchiolar epithelial cells)

Physical: Found in bronchioles; lack cilia

Function: (1) serve as progenitor cells after injury;

(2) secrete components of surfactant (glycoproteins and GAGs) that help reduce surface tension in small bronchioles, preventing collapse

(3) produce defensive proteins of the innate immune system (immunoregulatory and anti-inflammatory)

What type of cell is the vestibule of the nasal cavity lined with?

Respiratory epithelium or stratified squamous epithelium?

Stratified squamous epithelium

Since it lies near the body surface, the vestibule region is frequently exposed to destructive agents. The vibrissae (long nose hairs) help filter out particles as they enter the nasal cavity.

Further in, however, it becomes respiratory epithelium

What type of cell is the nasal fossae/cavities lined with?

Respiratory or stratified squamous epithelium?

Respiratory epithelium

The conchae create turbulance for moisterizing;

Swell bodies are found in the lamina propria (numerous blood vessels); vascular "erectile-type" tissue that can engorge, decreasing the flow of air locally, diverting drying air.

Olfactory mucosa

Olfactory cells 
- - Bipolar neurons (unmyelinated)
- - Long nonmotile cilia
- - Can regenerate

Sustentacular cells (supporting)
- - Microvilli
- - Junctional complexes with olfactory cells
- - Inactivate odorants

[image]

Olfactory mucosa

[image]

Olfactory cells 
- - Bipolar neurons (unmyelinated)
- - Long nonmotile cilia
- - Can regenerate

Sustentacular cells (supporting)
- - Microvilli
- - Junctional complexes with olfactory cells
- - Inactivate odorants

Basal cells - reserve cells for both sensory and sustentacular cells

Lamina propria - unmyelinated axons; serous Bowman's olfactory glands; secrete odorant binding protein, lysozyme, IgA and vessels

Olfactory mucosa

Olfactory cells 
- - Bipolar neurons (unmyelinated)
- - Long nonmotile cilia
- - Can regenerate

Sustentacular cells (supporting)
- - Microvilli
- - Junctional complexes with olfactory cells
- - Inactivate odorants

Basal cells - reserve cells for both sensory and sustentacular cells

Lamina propria - unmyelinated axons; serous Bowman's olfactory glands; secrete odorant binding protein, lysozyme, IgA and vessels

Where are the two places on the larynx that does NOT have respiratory epithelium?

Epiglottis and true vocal folds, which have stratified squamous epithelium (non-keratinized)

The vestibular folds have respiratory type epithelium, and so does the rest of the larynx.

Where on the larynx is respiratory epithelium NOT found?

Where on the larynx are mucous glands NOT found in the lamina propria?

[image]

Respiratory epithelium: upper surface of epiglottis and true vocal folds (stratified squamous)

Mucous glands: true vocal folds, vocalis ligament, and vocalis muscle

Where is hyaline cartilage found in the larynx?

Where is elastic cartilage found in the larynx?

Hyaline: All the -oid's-> thyroid, cricoid, part of arytenoid

Elastic: epiglottis, cuneiform, corniculate ,rest of arytenoid

Arytenoid has both hyaline and elastic cartilage

What type of epithelium does the trachea have?

What are the contents in the lamina propria in the trachea?

Respiratory type epithelium

Lamina propria: mixed mucous glands, fibroelastic layer, hyaline cartilage, trachealis muscle, fibroelastic ligament

The presence of cartilage

If it has cartilage, it must be a bronchus; if it doesn't have cartilage, it is a bronchiole

What two distinguishing factors does this structure have?

[image]

Bronchus

Smooth muscle: bundles spiral around the lumen in the lamina propria

Cartilage (hyaline): discontinuous plates; plates get smaller peripherally, where they tend to be found at bifurcations

What two distinguishing factors does this structure have?

[image]

Bronchus

Smooth muscle: bundles spiral around the lumen in the lamina propria

Cartilage (hyaline): discontinuous plates; plates get smaller peripherally, where they tend to be found at bifurcations

What two distinguishing factors does this structure have?

[image]

Bronchus

Smooth muscle: bundles spiral around the lumen in the lamina propria

Cartilage (hyaline): discontinuous plates; plates get smaller peripherally, where they tend to be found at bifurcations

What distinguishing factor differentiates it from the rest of the respiratory epithelia?

[image]

Bronchioles (<5mm)

NO cartilage or submucosal glands

Smoth muscle is prominent, since cartilage is lacking

ciliated epithelium that becomes less columnar -> cuboidal

Goblet cells are diminished and absent in terminal bronchioles

Prominent clara cells, which are secretory and lack cilia (produce defensive proteins and glycoproteins and GAGs that help reduce surface tension in the small bronchioles)

Diffuse neuroendocrine system cells

Bronchioles (<5mm)

NO cartilage or submucosal glands

Smoth muscle is prominent, since cartilage is lacking

ciliated epithelium that becomes less columnar -> cuboidal

Goblet cells are diminished and absent in terminal bronchioles

Prominent clara cells, which are secretory and lack cilia (produce defensive proteins and glycoproteins and GAGs that help reduce surface tension in the small bronchioles)

Diffuse neuroendocrine system cells

Bronchioles (<5mm)

Prominent clara cells, which are secretory and lack cilia (produce defensive proteins and glycoproteins and GAGs that help reduce surface tension in the small bronchioles)

Bronchioles (<5mm)

NO cartilage or submucosal glands

Smoth muscle is prominent, since cartilage is lacking

ciliated epithelium that becomes less columnar -> cuboidal

Goblet cells are diminished and absent in terminal bronchioles

Prominent clara cells, which are secretory and lack cilia (produce defensive proteins and glycoproteins and GAGs that help reduce surface tension in the small bronchioles)

Diffuse neuroendocrine system cells

What is the difference between a terminal and respiratory bronchiole?

[image]

[image]

While terminal and respiratory bronchioles are cuboidal and ciliated, respiratory bronchiole has alveoli along their walls.

Other differences include: (1) epithelium merges to flattened non-ciliated cells; (2) they terminate in alveolar ducts, which are passages of adjacent alveoli, with smooth muscle bundles at their openings, lined by flattened epithelium

What is the name of the passageway by which adjacent alveoli open to each other?

Pores of Kohn

The Pores of Kohn are pores between adjacent alveoli, or interalveolar connections. They function as a means of collateral ventilation; that is, if the lung is partially deflated, ventilation can occur to some extent through these pores. The pores also allow the passage of other materials such as fluid and bacteria.

The Pores of Kohn take their name from the German physician Hans Kohn [1866-1935] who first described them in 1893 ^[1].

Respiratory acinus

Composed of Respiratory bronchioles (RB), Aveolar Ducts (AD), Alveolar sacs (cluster of aveoli with common opening), alveoli - the functional part of gas exchange

[image]

The septa contain pulmonary veins and lymphatics (arteries travel with the bronchus tree)

What is the difference between centriacinar and panacinar ephysema?

[image]

[image]

• Panacinar emphysema: The entire respiratory acinus, from respiratory bronchiole to alveoli, is expanded. 
• Centriacinar emphysema: The respiratory bronchiole (proximal and central part of the acinus) is expanded.

Type I (40%) |  Type II (60%)

Type I covers 95% of the alveolar surface, while type II covers 5% of the surface.

Alveolar Wall, thin part

Blood-air barrier

1. A water-surfact layer lining the alveoli

2. Type I (squamous) alveolar cell

3. A shared (fused) basal lamina

4. The endothelium of the pulmonary capillaries, which are non-fenestrated (which makes sense, since you're only diffusing small particles like oxygen and CO2)

Thin: Most places the alveolar wall consists of blood-air barrier structures.

Thick: consists of regions where the shared basal lamina separates into basal lamina for alveolar epithelim and basal lamina for endothelium, thus forming a tissue space containing many elastic fibers, important in the elastic recoil of the normal lung. Collagen fibers, macrophages, and other connective tissue cells are also present here.

Alveolar wall, thick wall

separate basal lamina for alveolar epithelim and endothelium

forms a tissue space containing many elastic fibers (elastin), important in the elastic recoil of the normal lung, allowing the lung to stretch to accomodate inhaled air; becomes like a string-like tether supporting bronchioles by attachment to lung parechyma (alveoli).

Collagen fibers, macrophages, and other connective tissue cells are also present here.

(silver stain highlights the elastin in alveolar walls)

Alveoli (air space)

Air space: Macrophages (or dust cells)

Surfactant: lowers surface tension

Walls have thick and thin parts.

Alveolar pores: equalize interalveolar air pressure

Type I pneumocyte

Attenuated cytoplasm, relatively few organelles.

Joined together by tight junctions.

Part of the blood-air barrier.

Line 95% of the lung (40% of cell population).

300 million alveoli per lung.

Type II pneumocyte

Surfactant production: responsible for the production and secretion of surfactant (the majority of which are dipalmitoyl phosphatidylcholine), a group of phospholipids that reduce the alveolar surface tension. Surfactant phospholipids are stored in Type II pneumocytes in lamellar bodies, which are granules in the apical cytoplasm.

Progenitor cells: for type I pneumocyte

cuboidal, often at corners of alveoli confluences

Line 5% of alveolar surface (but form 60% of cell's population).

What are the arrows pointing to?

[image]

Lamellar bodies

Located in type II pneumocytes, they are granules in the apical cytoplasm that contain phospholipids (mostly dipalmitoyl phosphatidylcholine) and proteins. When exocytosed, these products form pulmonary surfactant, which lowers surface tension in the alveoli, preventing alveolar collapse.

Lamellar bodies

Located in type II pneumocytes, they are granules in the apical cytoplasm that contain phospholipids (mostly dipalmitoyl phosphatidylcholine) and proteins. When exocytosed, these products form pulmonary surfactant, which lowers surface tension in the alveoli, preventing alveolar collapse.

Alveolar Wall

composed of thick (macrophages, elastic fibers, collagen fibers) and thin parts (blood-air barrier)

Pulmonary arteries: accompany bronchi and bronchioles

Pulmonary veins: run in the fibrocollagenous septa (run in the bronchovascular bundle at the level of bronchi)

Bronchial arteries: follow bronchial tree to the level of respiratory bronchiole, where they anastamose with pulmonary artery branches

Bronchial veins: run with bronchial arteries, in airway adventitia; drainage via pulmonary veins

Alveolar Macrophage

Collect particulate matter in airspaces and migrate out of microvasculature to...

(1) the thick portion of alveolar wall where they migrate to lympatics that start at the level of the respiratory bronchiole

(2) into bronchioles, where the "mucociliary ladder/escalator" moves them into bronchi where they are expectorated (coughed up)

Lymphatic drainage begins at the level of the respiratory bronchiole (as opp. to the alveolar structures).

Travels with the bronchovascular tree, in the interlobular septa and visceral and parietal pleura.

Viseral and Parietal pleura

covered by simple squamous (to cuboidal) mesothelium

subpleural (Loose CT tissue) soft tissue contains lymphatics and small blood vessels, collagen (type III and some type I) and elastic fibers

lymphatics drain the fluid in the pleura, secreted by the mesothelial cells, lubricating the potential space (pleural cavity) between the visceral and parietal layers.

Pleura controls volume and protein content by...

(1) capillariers (volume) and (2) mesothelial microvilli (protein content)

Visceral vs. Parietal Pleura:

Blood supply, drainage, and innervation

Viseral pleura

Blood supply: bronchial arteries

drainage: pulmonary veins and superficial lymphatic plexus (with extensive interconnections to other vessels)

Innervation: vagus and sympathetic nerves

Parietal pleura

Blood supply: intercostal vessels

Drainage: lymphatic lacunae separate mesothelium that drain to intercostal lymphatics -> mediastinum

Innervation: intercostal nerves