Histology and Embryology (Respiratory) Flashcards
What are the respiratory system functions in blood pressure control?
Via renin-angiotensin system. Angiotensin I -> angiotensin II via angiotensin-converting enzyme (ACE) in lung capillaries.
Describe the epithelial changes that happen as you move through the nasal cavity.
Initial part (vestibule) has keratinised stratified squamous epithelium, then keratin is lost, then it is respiratory epithelium.
Describe respiratory epithelium.
Pseudostratified ciliated columnar epithelium with goblet cells.
What does the lamina propria in the nose contain?
Seromucous glands and a rich venous plexus which can quickly engorge with blood and block the nose.
What is the difference between olfactory and respiratory epithelium?
It is taller.
What parts of the oropharynx and epiglottis have non-keratinised stratified squamous epithelium?
All of the oropharynx, the anterior (lingual) surface and upper part of the posterior surface of the epiglottis.
What are the vocal folds and adjacent structures covered with?
Stratified squamous epithelium.
What is the open side of the C shaped cartilage of the trachea spanned by?
Fibroelastic tissue and smooth muscle (trachealis muscle).
Describe the layers of the trachea.
Respiratory epithelium -> basal lamina -> lamina propria (connective tissue with abundant elastic fibres) -> submucosa (connective tissue, includes numerous seromucous glands).
What are the rings of hyaline cartilage in the trachea replaced by in the bronchi?
Irregularly shaped cartilage plates.
Describe the layers of a bronchus.
Respiratory epithelium -> lamina propria -> muscularis (ring of smooth muscle) -> submucosa (adipose tissue with some seromucous glands)
When is cartilage lost in the airway?
When it is about 1mm in diameter.
Compared to bronchi, what do bronchioles lack and still have?
Lack cartilage and glands, still have smooth muscle.
What happens to the epithelium as you progress down the respiratory tree?
It decreases in height from columnar to cuboidal.
What is the lamina propria composed of in bronchioles?
Smooth muscle, elastic and collagenous fibres.
What are the terminal bronchioles?
The smallest bronchioles that lack respiratory (gas exchange) function.
What are the roles of club cells and where are they found?
Stem cells, detoxification, immune modulation, surfactant production.
Where does gas exchange start?
Respiratory bronchioles.
Describe type I alveolar cells (pneumocytes).
Simple squamous epithelium that lines the alveolar surfaces covering over 90% of alveolar surface. Provide a barrier of minimal thickness that is permeable to gases.
Describe type II alveolar cells (pneumocytes).
Polygonal in shape, free surface covered by microvilli and cytoplasm displays dense membrane bound lamellar bodies which contain surfactant (released by exocytosis).
What are alveolar macrophages (dust cells)?
Free cells in septa or migrating over luminal surfaces of alveoli, phagocytosing inhaled particles that escape entrapment.
What does the air-blood barrier consist of?
Type I cell, the endothelial cell and the basal lamina of each (200-600nm).
What are the pores of Kohn?
Pores between alveoli.
What are the pleural membranes composed of?
Outer layer of simple squamous epithelium (mesothelium) backed by layers of fibrous and elastic connective tissue.
What is the structural difference between the visceral and parietal pleura?
They are similar but parietal generally simplest membrane lining the thoracic cavity.
What is the ridge called that forms between the respiratory diverticulum and the eosophagus?
Treacheoesophageal ridge.
What does the respiratory diverticulum split into?
2 lung buds.
What does the tracheoesophageal ridge close up to form?
The trachea and the oesophagus.
What surrounds the lung buds and the oesophagus?
Splanchnic mesoderm.
What is an oesophageal atresia?
Blind ending of the oesophagus.
What is a tracheoesophageal fistula?
Communication between the trachea and oesophagus.
Can fistulas and atresias occur in combos?
Yes.
At what days do the primary, secondary and tertiary bronchial buds form?
Primary - 28 days, secondary - 30 days, tertiary - 38 days.
When are the terminal bronchioles formed?
At 16 weeks.
What are the stages of embryological lung development?
Embryonic, pseudoglandular, canalicular, saccular, alveolar.
What time periods are these stages associated with?
Embryonic: 26 days - 6 weeks. Pseudoglandular: 6-16 weeks. Canalicular: 16-28 weeks. Saccular: 28-36 weeks. Alveolar: 36 weeks - early childhood.
Describe lung tissue in the newborn.
Blood capillaries are in direct contact with the mature alveoli.
