Histology/Embryology Flashcards
What is the functions of the nasal cavity?
- Warming 2. Moistening 3. Filtering
What kind of epithelium lines the vestibule (initial part) of the nasal cavity?
Keratinised stratified squamous epithelium.
Which epithelium lines the deeper part of the nasal cavity and the rest of the conducting system?
Pseudostratified ciliated columnar epithelium with goblet cells, or Respiratory Epithelium.
What kind of epithelium lines the oropharynx and epiglottis?
Non-keratinized stratified squamous epithelium (as it transmits both air and swallowed food so must resist abrasion)
What spans the open side of the ‘C’ shaped cartilage rings of the trachea?
Fibroelastic tissue and smooth muscle (trachealis muscle).
One more time for luck: what kind of epithelium is respiratory epithelium?
Pseudostratified ciliated columnar epithelium with goblet cells
What replaces the rings of cartilage in the trachea when it bifurcates into bronchi?
Becomes irregularly shaped cartilage plates
What changes in the epithelium of bronchioles as you move down?
The epithelium decreases in height from columnar to cuboidal
What kind of epithelium and cells line the terminal bronchioles?
Lined with cuboidal ciliated epithelium and contain non-ciliated club cells (Clara cells) that project above the level of adjacent ciliated cells.
What are the roles of the Clara cells of the terminal bronchioles?
• Stem cells • Detoxification • Immune modulation • Surfactant production
What are the 2 cell types of the alveoli and what are their function?
Type I Alveolar cells: engage in gas exchange Type II Alveolar cells: produce surfactant
What are alveolar dust cells?
- Aka dust cells - Free cells either in the septa or migrating over the luminal surfaces of the alveoli, phagocytosing inhaled particles that may have escaped entrapment by the mucous lining of the airway.
What makes up the air-blood barrier?
Consists of Type I cell, endothelial cell and the basal lamina of each
Which germ layer does the lining of trachea and bronchial tree arise from?
Endoderm
Which germ layer does all other lung tissue arise form?
Visceral mesoderm
Oesophageal atresia
Proximal part of the oesophagus has a blind ending like a pouch, while the distal end is attached to the trachea. Means the baby cant feed, so need to ensure it is nourished
Tracheoesophageal fistula
Occurs when the oesophagus doesn’t split like in a fistula, so there is no blind ending so both ends are attached (communicating) at the trachea
What is the most common respiratory congenital defect?
Failure of the trachea and oesophagus to separate as they both arise form the gut tube (endoderm)
What is the order of stages of maturation of the lungs embryologically and what is the time period for each?
1) Embryonic (26 days- 6 wks)
2) Pseudoglandular (6-16 wks)
3) Canalicular (16-38 wks)
4) Saccular (28-36 wks)
5) Alveolar (36wks-early childhood)
What occurs during the 1) Embryonic stage?
Large structures of the lung are set out: Respiratory diverticulum forms and Initial branching to give lungs, lobes and segments
What occurs during the 2) Pseudoglandular stage?
14 more generations of branching: Terminal Bronchioles
What occurs during the 3) Canalicular stage?
Terminal Bronchioles → ≥2 Respiratory bronchioles → 3 – 6 alveolar ducts associated with these
What occurs during the 4) Saccular stage?
Terminal sacs actually form; Capillaries establish close contact
What occurs during the 5) Alveolar stage?
Alveoli mature; up until this point the alveolar sacs may be present but they haven’t matured so they are still too thick to allow gas exchange, so in this stage the mature alveoli form with thin walls and large SA
