Histology Flashcards
what does the nasal cavity do?
1 - warming
2 - moistening
3- filtering
(contains an area of specialised olfactory epithelium)
what is the lining of the nasal cavity made of?
- the initial part is lined by keratinised stratified squamous epithelium.
- deeper into the nasal cavity, the keratin is lost
- eventually it changes to pseudostratified ciliated columnar epithelium with goblet cells = respiratory epithelium
Describe respiratory epithelium (in the nose).
- has psuedostratified columnar epithelium ciliated with goblet cells
- also contains basal cells
- has cilia lining the surface
- there is a lamina propria/ submucosa below the respiratory epithelium. The lamina propria is a band of loose connective tissue containing seromucus glands and thin walled venous sinuses which can quickly engorge with blood and block the nose
what type of epithelium covers the oropharynx and epiglottis?
- because the oropharynx transmits both air and food, it must resist abrasion and is lined by non-keratinized stratified squamous epithelium, as is the anterior surface and upper part of the posterior surface of the epiglottis.
Describe the lining of the larynx.
-the walls are made up of cartilage and muscles with respiratory epithelium lining its surfaces with the exception of the vocal folds and adjacent structures, which are covered with stratified squamous epithelium.
Describe the histology of the trachea
- is continuous with the larynx and terminates by dividing into main bronchi
- contains 15-20 C shaped cartilages.
- open side of the C cartilage is spanned by fibroelastic tissue and smooth muscle
- walls include a lining of respiratory epithelium backed by a basal lamina, a lamina propria and a submucosa of connective tissue including a number of seromucous glands
Describe the lining on the bronchi.
The ‘rings’ of hyaline cartilage are replaced by irregularly shaped cartilage plates. The wall of the bronchus is made up of respiratory epithelium (RE), a lamina propria (LP), a muscularis consisting of a ring of smooth muscle and a submucosa (SM) with adipose tissue and some seromucous glands
Describe the walls of bronchioles
- they are less than 1 mm in diameter and lack cartilage but may contain a few goblet cells initially
- the epithelium decreases in height from columnar to cuboidal as you progress down the respiratory tree to the smallest bronchioles.
- the lamina propria is composed of smooth muscle and elastic and collagenous fibre
hoe do bronchioles play a role in asthma attacks and allergic reactions?
-smooth muscle of the bronchioles responds to parasympathetic innervation, histamine and other factors by contracting and constricting the diameter of the bronchiole.
what are club cells (clara cells)?
- non-ciliated cells that project above the level of adjacent ciliated cells
- roles; stem cells, detoxication, immune modulation, durfactant production
- found in terminal bronchi
what is the first functioning respirator part of the lungs?
-respiratory bronchioles
what are type 1 alveolar cells?
simple squamous epithelium that lines the alveolar surfaces covering over 90% of the alveoli
- minimal thickness so its permeable to gases
what are type 2 alveolar cells?
- polygonal in shape
- free surface is covered by microvilli and the cytoplasm has lamellar bodies which contain surfactant
- surfactant released by exocytosis and spreads over the pulmonary surface to reduce surface tension.
why can premature babies struggle with respiratory?
- lamellar bodies are needed to break up surface tension around alveoli
- premature infants may not yet be able to produce this
what do alveolar macrophages do?
- free cells either in the septa or migrating over the luminal surfaces of the alveoli
- phagocytosing inhaled particles that escaped the mucus.
