Guided learning- Respiratory histology Flashcards
1
Q
What type of epithelium line the nasal cavity?
A
Respiratory mucosa lines the nasal cavity. Respiratory mucosa is pseudostratified ciliated columnar epithelium with mucus producing goblet cells.
2
Q
Describe the histology of respiratory epithelium in the nasal cavity.
A
- Top layer is a layer of Mucus overlying the ciliated psuedostratified columnar epithelium.
- Interspersed are goblet cells which appear paler (take up stain less as mucus producing).
- The columnar epithelium lie on top of a basement membrane.
- This thin BM lies over the lamina propria which is a thicker layer of loose connective tissue.
- Many blood vessels and seromucosal glands are present in the lamina propria.
3
Q
What do the letters on the image stand for?
A
E= respiratory epithelium- pseudostratified ciliated columnar cells with goblet cells interspersed
M- mucosal glands
S- serous glands
V- venules
4
Q
Correlate the structure of the nasal epithelium to its function.
A
- Mucus production by goblet cells traps bacteria and particles
- This is then swept away by the cilia and down the pharynx and oesophagus to be killed by acid in the stomach. (Mucociliary escalator).
- These secretions also help to humidify the air
- The lamina propria is highly vascular (dense submucosal vasculature) which helps warm air to body temperature.
5
Q
How does the mucosa in the olfacotory region of the nose differ to the rest of the nasal mucosa?
A
The olfactory region is lined by olfactory mucosa not respiratory mucosa.
Olfactory mucosa is tall pseudostratified columnar epithelium.
6
Q
Describe olfactory epithelium:
What types of cells make up the epithelium?
What does this mean for function?
A
- Tall pseudostratified columnar epithelium.
- Olfactory receptor cells extend through the epithelium and end superficially in an olfactory knob.
- From the olfactory knob are non motile olfactory cilia which extend to lie in the mucus layer and interact with odourous substances via odorant receptors on the cilia.
- Basally the olfactory receptor cells form axons which join together to form the olfactory nerve and pass through the cribriform plate.
- Once axons pass through the cribriform plate they terminate and synapse with second order neurones in the olfactory bulb of the forebrain.
- There are also supporting cells called sustenticular cells which have villi that form a tangled mat with olfactory cilia.
- Lastly there are Basal cells resting near the basal lamina of the olfactory epithelium. These are capable of becoming olfactory receptor cells or epithelium.
7
Q
State 3 functional correlates of olfactory epithelium
A
- Basal cuboidal cells are stem cells for other cell types - become either olfactory receptors or supporting cells.
- Olfactory cells are receptors for smell
- Bowman’s submucosal glands provide secretions for olfactory sensors to lie.
8
Q
Where is respiratory epithelium found and what type of epithelium is it?
Where is simple cuboidal epithelium found in the respiratory tract?
Where is simple squamous epithelium found in the respiratory tract?
A
- In the conducting airways, from the nasal passage into the bronchi- ciliated psuedostratified columnar epithelium.
- In the bronchioles- simple cuboidal epithelium.
- In lung alveoli- simple squamous epithelium.
9
Q
Describe the pharyngeal mucosa.
A
- Dense lymphoid infiltrate which forms a ring of lymphoid tissue called Waldeyer’s ring.
- Waldeyers ring is made up of the adenoid, tubal, palatine and lingual tonsils.
- This ring of lymhoid tissue encircles openings of GI tract and respiratory tract
- Respiratory epithelium is again present- pseudostratified ciliated columnar cells.
10
Q
Describe the Laryngeal mucosa:
What folds are there superiorly and inferiorly?
What type of epithelium overlies them?
How does this link to function?
A
- larynx is the beginning of lower respiratory tract and leads into the trachea
- contains false vocal folds (vestibular folds) superiorly- the vestibular ligament covered by mucous membrane
- contains the true vocal folds (vocal folds) inferiorly - which contain your vocal cords covered by mucous membrane
- Inbetween the false/ vestibular fold and the true/vocal fold is the ventricle and saccule.
- Overlying the vestibular ligament is respiratory epithelium- pseudostratified ciliated columnar cells with goblet cells.
- Overlying the vocal cords is stratified squamous epithelium.
- This is designed to withstand wear and tear during phonation and swallowing.
11
Q
Describe this mucosa overlying the true vocal folds
A
- Mucosa overlying true vocal folds consists of stratified squamous epithelium.
- Basally cells are cuboidal/ columnar.
- Moving more towards the lumen they become polyhedral
- It is only at the luminal surface do they become squamous.
12
Q
Describe the histology of the trachea
A
- Lumen is lined by ciliated pseudostratified columnar epithelium with goblet cells.
- Underneath respiratory epithelium is lamina propria which contains elastin and collagen fibres (support and elastic recoil), blood vessels (warm air) and nerve tissue.
- Underneath lamina propria is the submucosal layer which contains mixed seromucous glands whose secretions humidify air and together with mucus from goblet cells trap particles and bacteria.
- Underneath submucosa is cartilaginous layer- contains C shaped rings of hyaline cartilage that are connected by longitudinal smooth muscle fibres of the trachealis muscle.
- Hyaline cartilage prevents complete collapse.
- Trachealis muscle bows outward in inspiration (increase diameter) and can contract during coughing to increase intrathoracic pressure.
13
Q
Compare the histology of the bronchi and bronchioles to the trachea.
A
- Amount of cartilage, thickness of resp epithelium and degree of pseudostratification all decrease as you descend from conducting airways towards alveoli.
- Respiratory epithelium less tall and fewer goblet cells
- Lamina propria has more elastin and a layer of smooth muscle between it and submucosa.
- Layer of smooth muscle increases as you move distally.
- Fewer submucosal glands
- Cartilage support is in discontinous plates which are replaced increasingly by smooth muscle and you progress distally. (in trachea cartilage rings tend to encircle whole trachea).
14
Q
Describe how the structure of bronchi and bronchioles correlates to their function.
A
- Respiratory epithelium well suited to clearance of foreign material, mucociliary escalator sweeps mucus up to pharynx.
- Replacement of cartilage by smooth muscle creates increasing flexibilty as you move distally.
- Support also comes from surrounding elasticity of alveoli
- Epithelium changes to simple ciliated columnar with few goblet cells as you reach the bronchioles.
15
Q
Desrcibe histology of terminal bronchioles
A
- Last part of conducting system before gas exchange
- Then divide into respiratory bronchioles
- Lined by ciliated cuboidal cells
- only 1-2 layers of smooth muscle, no cartilage and no submucosal glands
- Goblet cells are replaced by clara cells:
- non ciliated cells with apical granules
- stem cells
- Secrete surfactant
- produce enzymes that help breakdown mucus and detoxify noxious substances
16
Q
Describe the histology of respiratory bronchioles
A
- Respiratory zone can exchange gas, begins with respiratory bronchiole which branches into several alveolar ducts with numerous alveolar outpouchings.
- These alveolar outpouchings end in alveolar sacs which end in individual alveoli.
- The whole system is served by a single respiratory bronchiole, and termed a respiratory lobule.
- Respiratory alveoli are lined by simple squamous epithelium. (Transition from terminal bronchiole with simple cuboidal epithelium).
19
Q
Describe the histology of the alveoli
A
- Epithelium of alveoli contains two main cell types:
- Type 1 pneumocytes (squamous epithelial cell) (95% total alveolar area)- large flattened cells spread out, very thin diffusion barrier for gas exchange. Connected by tight junctions.
- Type 2 pneumocytes (5% total alveolar area)- secrete surfactant, reduces surface tension to prevent collapse during expiration. Connected by tight junctions and can become type 1 pneumocyte if needed.
- Also pores of kohn- holes between walls of adjacent alveoli.
- Alveolar supporting tissue made up of collagen and elastin/ fibroblasts.
- Elasticity of alveoli important in recoil and passive expiration.
- Basement membrane between alveolar epithelium and endothelial cells in close opposition or even fused to faciliate gas transfer.
