w1 histology of the respiratory tract

Question 1

What is mechanical respiration?

Answer 1

Type of respiration that occurs in the respiratory tract.
O2 required for respiration is absorbed into the bloodstream and CO2 is excreted.

Question 2

What are the divisions of the respiratory tract from the trachea to the alveoli?

Answer 2

Trachea
Main Bronchi
Lobar Bronchi
Segmental Bronchi
Bronchioles
Terminal Bronchioles
Respiratory bronchioles
Alveolar ducts
Alveolar sacs
Alveoli

Question 3

What is respiratory mucosa?

Answer 3

Pseudostratified columnar ciliated epithelium
Found only in the conducting part of the respiratory system.

Question 4

What is the function or paranasal sinuses?

Answer 4

Lighten the skull weight and increases resonance in speech (transfer of sounds out of voice box)

Question 5

What sections of the respiratory tract has more elastic fibres?

Answer 5

The respiratory portion (respiratory bronchi downwards)

Question 6

What is carina?

Answer 6

The section of the trachea where it bifurcates into two bronchi.

Question 7

What type of specialist cell is found in the conductive portion of the respiratory tract epithelium?

Answer 7

Numerous goblet cells

Question 8

What is the function of respiratory epithelium?

Answer 8

Inspired air is moistened by secretions from serous glands
Sheet of mucus is secreted from goblet cells, traps external particles that can then be wafted into nasopharyn by cilia (mucociliary clearance), then swallowed or destroyed by phagocytes.

Question 9

What is olfactory mucosa?

Answer 9

Found on the roof of the nasal cavity.
Recieves and relays olfactory signals (odor signals).

Question 10

What different structures can be found in olfactory mucosa?

Answer 10

Bipolar neurons
Bowman/olfactory glands
Sustentacular cells
Basal cells

Question 11

What is the function of bipolar neurons in the olfactory mucosa?

Answer 11

A neuron with two extensions, an axon and a dendrite which extend on opposite sides of the cell body.
Helps carry electrical impulses between the brain and the epithelium.

Question 12

What is the function of the Bowman/Olfactory gland in the olfactory mucosa?

Answer 12

Dissolve odiferous particles,
Glands secretions may act as the solvent for which the odorous substances dissolve, makes them easier to detect.

Question 13

What is the function of sustentacular cells in the olfactory mucosa?

Answer 13

Provide physical support, nourishment and electrical insulation for the olfactory cells.

Question 14

What is the function of the basal cells?

Answer 14

Have considerable proliferative capacity and can replace both sustentacular and olfactory cells.

Question 15

What are K-cells?

Answer 15

Kulchitsky cells are a type of DNES (diffuse neuroendocrine system),
Cells contain secretory granules such as seratonin, calcitonin, ADH and ACTH.
May give rise to small cell lung cancer.

Question 16

What do basal cells look like under a microscope in histology?

Answer 16

Sit deep to the epithelium but superficial to the basement membrane.
They are rounded mitotic stem cells.
Short and stubby, with a darkly stained nucleus taking up the majority of the cell.

Question 17

What is mucocillary clearance?
What are other terms for it?

Answer 17

Also called mucociliary transport or mucociliary escalator.
Is the self clearing mechanism of the airways of the respiratory system, cilia waft in a unidirectional fashion to move mucus and content up towards the larynx, where it can be swallowed or coughed up.
A protective process against pathogens.

Question 18

What is the average dimension of a trachea in a healthy adult?

Answer 18

10cm in length and 2-3cm in diameter

Question 19

What are the different layers in the trachea?

Answer 19

1. Respiratory mucosa
2. Submucosa
3. Cartilaginous layer (bridged posteriorly by smooth muscle and fibroelastic fibres)
4. Adventita

Question 20

What is the function of the trachealis muscle?

Answer 20

To contract and constrict the airway, allows more air to be expelled with more force such as when coughing.
Used during involuntary/parasympathetic nervous control.
Under autonomic nervous system control.
Is smooth muscle with some longitudinal muscle fibres posteriorly.

Question 21

What sort of structures are found in the adventitia of the respiratory tract?

Answer 21

Is a loose connective tissue.
Contains fibroblasts and blood vessels

Question 22

What is the function of seromucous glands in the respiratory tract?

Answer 22

Help humidify inspired air as watery secretions.

Question 23

What type of cartilage is found in the trachea?

Answer 23

C shaped hyaline cartilage.

Question 24

What is meant by squamous metaplasia in the lower respiratory tract?

Answer 24

The tracheobronchial mucosa is subject to lots of damage,
Prolonged or repeated damage to the epithelial cells by smoking results in their death, they are replaced by squamous metaplasia.
SM it self is neoplastic, simply causes thickening of the lungs, may eventually develop into carcinoma insitu or a neoplasm blocking the bronchi.

Question 25

How does cartilage change along the bronchi?

Answer 25

Extrapulmonary bronchi have incomplete cartilage rings similar to the trachea
Intrapulmonary bronchi have more irregular cartilage plates around its circumferences, deeper into the lungs cartilage becomes less common and more focused around bifurcations.

Question 26

How can smooth muscle be identified under a microscope in histology?

Answer 26

Elongated/flat cells with an elongated nucleus.
Cells are relatively eosinophilic.

Question 27

What are chondrocytes?

Answer 27

Cells that up the structural components of cartilage.

Question 28

What is the important histological change in the segmental bronchi?

Answer 28

Epithelium starts to change from pseudostratified epithelium, to simple columnar to simple cuboidal and eventually simple squamous in the alveoli.

Question 29

What happens to the number of mucous glands as you move from the conducting to the respiratory zone of the respiratory tract?

Answer 29

Decreased number of mucous glands.
No submucosal glands in the terminal bronchi onwards

Question 30

What is the most probable type of epithelium from the lobar bronchi onwards?

Answer 30

Lobar - respiratory (pseudostratified)
Terminal bronchioles - simple cuboidal
Respiratory bronchioles - mix of simple cuboidal and simple sqauamous
Alveolar ducts and sacs - simple sqauamous.

Question 31

What are some key features of the terminal bronchioles?

Answer 31

No cartilage
Fewer goblet cells
More clara cells.

Question 32

Roughly how many divisions of the bronchioles are there?

Answer 32

13 divisions

Question 33

What is the function of clara cells in the respiratory tract?

Answer 33

Secrete non mucus substances, mainly protein, into the lumen.
Site of xenobiotic metabolism within the lungs
Progenitor cell for an injured bronchiole.
Secrete surfactant and protect from toxins.
Found in the proximal alveolar ducts and respiratory bronchioles.

Question 34

What are the cells in the alveoli called?

Answer 34

Pneumocytes
Type 1: structural role, flat and share basal lamina with endothelial cells for gas exchange
Type 2: round and secrete surfactant.

Question 35

List the type of epithelium and distinguishable features in the:
Terminal Bronchioles
Respiratory bronchioles
Alveolar ducts
Alveolar sacs
Alveoli

Answer 35

TB = simple cuboidal, ciliated, clara cells, no cartilage, no goblet cells, smooth muscle.
RB = simple cuboidal, ciliated, clara cells
AD onwards = squamous, no cilia, types 1 and 2

Question 36

What are the different proportions of pneumocytes?

Answer 36

Type 1 = 40% of total cells but 95% of the alveolar surface
Type 2 = 60% of the total cells but 5% of the alveolar surface.

Question 37

How can the different types of pneumocytes by identified under a microscope?

Answer 37

Type 1: Thin and flattened with a flat nuclei, difficult to view with a light microscope - thin diffusion pathway
Type 2: Rounded with a rounded nuclei - secrete surfactant.

Question 38

What is neonatal respiratory distress syndrome?
Give an overview of the condition?

Answer 38

Surfactant production occurs in late gestation, hence premature babies have less surfactant so struggle to inflate their lungs.
Can be treated with positive pressure ventilation, giving the mother during pregnancy corticosteroids to encourage surfactant production or giving the baby exogenous surfactants after birth.

Question 39

What is an alveolar pore?
Why are they important clinically?

Answer 39

Pores allow air pressure to equilibrate and air to circulate between alveoli on different ducts or sacs if the local airway becomes blocked.
Clinically this may contribute to the spread of bacteria in the lungs.

Question 40

What makes up the blood air barrier in the lungs?

Answer 40

The air-blood barrier consists of an alveolar type 1 cell, a capillary endothelial cell and their fused basement membranes.
The inner lining of the alveoli is covered by surfactants.

Question 41

What is an interalveolar septum?

Answer 41

An infolding of the blood gas barrier, a inward part between alveoli, separate partially into different air spaces

Question 42

Where might macrophages be found in relation to the alveoli?

Answer 42

Inside the alveoli sacs
Outside in the interstitial space surrounding the capillaries.

Question 43

What is important about the interstitial space in the lungs?

Answer 43

Contains elastic fibres, needed for elastic recoil.

Question 44

What type of immune tissue may be found in the respiratory system?

Answer 44

BALT in submucosa.

Question 45

What happens to cillia as you progress down the respiratory tract?

Answer 45

Gradually decreases

Question 46

What histological changes occur abruptly at the junction of a secondary bronchus with a bronchiole?

Answer 46

Goblet cells and mixed glands stop.

Question 47

What is a basal body?

Answer 47

Found at the base of cilia or falgellum, superficial to the main epithelial cell.
Are a microtubule organelle that produces cillia etc.