- Present throughout most of respiratory tract

- Pseudostratified ciliated columnar with goblet cells

Respiratory type epithelium

- most abundant respiratory epithelium cell

- contact basement membrane and free surface

-many cilia/short microvilli

Ciliated Cells

- secrete mucous

- narrow base, bulging center, narrow apical surface

- diminish in number as the tracheobronchial tree appraochs the respiratory bronchioles

Goblet Cells

- sensory nerves contact their basal surface

- microvilli on their free surface

Brush Cells

- Reserve cells that differentiate into the other respiratory epithelium cell types

- only contact the basement membrane (triangular)

Basal Cells

- part of the neuroendocrine system

- 'dense core' granules that release hormones

- serotonin, dopamine, somatostatin, calcitonin (inferior secretion to blood capillaries)

Neuroendocrine Cells

(Small granule cells, Kulchitsky cells)

- stratified squamous epithelium

- keratinized near opening, non-keratinized towards major portion

- sebaceous glands and hairs are abundant

Nasal Vestibule

- lined by respiratory epithelium

- not lined in olfactory region at the roof of the nasal cavity

- warms and humidifies incoming air

Nasal cavities/fossa

- numerous blood vessels, venous-plexus of erectile-type tissue forming 'swell bodies'

- mixed muco-serous glands likes small salivary glands

Lamina Propia

- can engorge which decreases the flow of air locally in the nasal cavities

Swell bodies

- located superiorly in the nasal cavity

- contains supporting/sustentacular, olfactory, basal, and unmyelinated nerve cells

Olfactory mucosa

- have microvilli on their free surface

- secretory and have abundant ion channels

- junctional complexes hold these with bipolar neurons

Supporting/Sustentacular Olfactory Mucosa Cells

- bipolar neurons (can regenerate)

- dendrite with expanded termination

- olfactory vesicle with mitochondria

- long cilia extend from the vesicles

Olfactory Cells

- cilia are matted down on the surface and have a central bulb

- distally (doublet), proximally (singlet)

- contact external environment

- unmyelinated axons that pass through cribiform plate of the ethmoid bone

Olfactory Cells

- unmyelinated nerves (primary olfactory)

- Bowman's olfactory glands (serous)

- vessels

Olfactory Mucosa Lamina Propria

- Non-keratinized stratified squamous on upper surface of epiglottis and true vocal folds

- respiratory type everywhere else

Larynx epithelium

- mixed muco-serous glands except on true vocal folds

- vocalis muscle and ligament found on vocal folds

Larynx Lamina Propria

- thyroid, cricoid, part of arytenoid cartilage

Hyaline Cartilage

- Epiglottis, cuneiform, corniculate, rest of arytenoid cartilage

Elastic Cartilage

- respiratory type epithelium

- mixed muco-serous gland lamina propria

- multiple C-shaped hyaline cartilages alternating with connective tissue

- trachealis muscle bridges cartilage posteriorly
(smooth muscle)

Trachea/Extrapulmonary bronchi

- pseudostratified ciliated columnar with goblet cells

- mixed glands and elastic fibers in lamina propria

- smooth muscle bundles around lumen

- irregular hyaline cartilage plates reinforce wall

Intrapulmonary bronchi

- lack cartilage

- progressively simpler pseudostratified columnar (respiratory) epithelium

- goblet cells absent in terminal

- clara cells present

-no glands

Bronchioles (Terminal)

- present in epithelium of smaller bronchioles

- secretory and lack cilia

- produce defensive proteins of the immune system

- produce glycoproteins and GAGs that reduce surface tension

Clara Cells

- require elasticity of alveolar walls to remain open

- prominent bands of smooth muscle encircling

Bronchioles

- resemble small terminal bronchioles except a few alveoli can be found along their walls

Respiratory bronchioles

- Alveolar duct

- Atrium

- Alveolar Sacs

- Alveoli

Pulmonary Acinus

- equalizes pressure

- allows for passage of macrophages

Pores of Kohn

- contains pulmonary veins and lymphatics

- binds 3-7 terminal bronchioles into lobules

- visible to naked eye due to macrophage carbon uptake into lymphatics

Interlobular septa (fibrous)

- loss of alveolar walls around the terminal bronchiole

- associated with smoking

Centrilobular emphysema

- loss of alveolar walls adjacent to the interlobular septa

- associated with pre-existing scars

Paraseptal Emphysema

- associated with alpha1-antitrypsin deficiency

Panlobular emphysema

- water-surfactant layer lining the alveoli

- squamous (Type I) alveolar cell

- shared basal lamina

- endothelium of pulmonary capillaries (non-fenestrated)

Blood-Air Barrier (Respiratory Membrane)

- cell type covers 95% of the alveolar surface

- only about 50% in number of alveolar cells

- extremely thin (nuclei almost not present)

Type I pneumocytes (squamous alveolar cells)

- 50% of cell population, 5% of covering of alveolar epithelium

- granules in apical cytoplasm (lamellar bodies) contain phospholipids and proteins

- progenitor cells for both pneumocytes

Type II pneumocytes

- lowers surface tension in the alveoli

- phospholipids condense in the aqueous environment to provide hydrophilic coating

- mostly dapalmitoyl phosphatidylcholine and proteins

Pulmonary surfactant

- consists of blood-air barrier structures

- mostly Type I pneumocyte cytoplasm

Thin portion of alveolar wall

- consists of regions where the shared basal lamina separates

- contains many elastic fibers

- source of elastic recoil in lung

- collagen fibers, macrophages, and CT cells present

Thick portion of alveolar wall

- collect particulate matter in airspaces

- migrate out of microvasculature and into thick portion of alveolar wall

- end up in lymphatics that begin at respiratory bronchiole

- moved by "mucociliary escaltor" into bronchi where they are expectorated (coughed up)

Alveolar macrophages

- follow the branching bronchi & bronchioles

- carry unoxygenated blood

Pulmonary arteries

- carry oxygenated blood

- small, supplying the bronchial tree through respiratory bronchioles

- anastomose with pulmonary arteries in the distal region

Bronchial arteries

- run in the interlobular septa

- join bronchovascular tree at the level of the bronchi

- main bronchial drainage

Pulmonary veins

- begins to drain at the level of the respiratory bronchiole

- not associated with alveolar structures

- travel with the bronchovascular tree, in the interlobular septa and in the visceral and parietal pleura

Lymphatics of the lung

- composed of mesothelium and underlying CT

- deep is a thin layer of loose CT that contains lymphatics and small blood vessels, collagen and elastic fibers

Pleura

- secrete a serous fluid that lubricates the pleural cavity

(between layers of visceral and parietal plurae)

Mesothelial cells

- drain the fluid in pluerae

- maintain the right volume of pleural fluid

Pleural lymphatics