Microanatomy

Question 1

Conducting vs respiratory divisions of airway

Answer 1

• Conducting: nasal passages, pharynx, larynx, trachea, bronchi, bronchioles (terminal)
• Purpose: filter, moisten, warm the air
• Respiratory: respiratory bronchioles, alveolar ducts and alveoli
• For gas exchange

Question 2

Respiratory epithelium (RE)

Answer 2

• Pseudostratified columnar ciliated epithelium w/ goblet cells (secrete mucous)
• There are basal cells, some of which are stem cells that replace the epithelium
• Line majority of respiratory pathways

Question 3

Nasal cavity

Answer 3

• Vestibule lined by keratinized squamous epithelium, and gradually transitions to RE as you approach the respiratory region
• There are seromucous glands present, which secrete Igs, lysozyme, and anti-bacterial enzymes
• Vascular plexi (swell bodies) are vessels near the epithelium that act as heat exchangers for warming the air
• No goblet cells at the olfactory region
• Along w/ the olfactory neurons, there are also sustentacular (or supporting) cells and basal cells (which can replace olfactory neurons and sustentacular cells)

Question 4

Salivary glands

Answer 4

• Numerous lobules containing acini
• 2 types: serous (watery secretion, lighter under LM) and mucous (viscous secretion, darker under LM)
• The acini and ducts are lined by epithelium that have the ability to contract and aids in gland secretion
• Oral cavity is primarily stratified squamous epithelium

Question 5

Trachea

Answer 5

• Larynx is lined by respiratory epithelia
• Trachia is also lined by RE, but there are cartilaginous tracheal rings that have a C shape (opening on posterior side)
• Open ends are connected by smooth muscle
• Tracheal RE has thick BM and LCT under the BM

Question 6

Bronchi

Answer 6

• Primary bronchi look similar to trachea
• Intrapulmonary bronchi are characterized by irregular plates of hyaline cartilage
• Contain columnar RE, seromucous glands, and smooth muscle

Question 7

Bronchioles

Answer 7

• Bronchioli have cuboidal epithelium (w/ cilia), no glands, lots of SM/elastic tissue (more than bronchus), and no hyaline cartilage
• SM layer most prominent feature (PsNS -> constriction)
• Clara cells are unique to bronchioles, they are dome-shaped w/ short microvilli and produce pulmonary surfactant (reduces surface tension to maintain airway patency)
• Clara cells can also differentiate to regenerate the epithelium

Question 8

Avleoli

Answer 8

• First part of respiratory division is respiratory bronchioles (what alveoli branch off of)
• Alveoli have squamous epithelia (no cilia), no glands, no SM, no hyaline cartilage
• Type 1 alveoli: occupy 90% of alveolar surface, organelles housed near nucleus, large surface area
• Type 2 alveoli: more numerous than type 1 but only occupy 10% of alveolar space, secrete surfactant, contain mulitlamellar bodies in cytoplasm (contains surfactant)
• Can also replace type 1 alveoli
• Alveolar macrophages phagocytose debris/organisms and ingest surfactant

Question 9

Blood air barrier

Answer 9

-Capillary endothelium, interstitial space, alveolar membrane and cytoplasm