w2: Respiratory histology

Question 1

What is meant by cellular respiration?

Answer 1

Cells producing ATO by metabolism of organic molecules

Question 2

What is meant by mechanical respiration?

Answer 2

O2 required for cellular respiration is absorbed into the blood stream and CO2 is removed, this is what happens in the respiratory system

Question 3

What structures make up the upper and lower respiratory tract?

Answer 3

Upper: nasal cavity, pharynx, larynx
Lower: trachea, bronchi, lungs.

Question 4

How is the respiratory tract divided functionally?

Answer 4

Conducting air way - nose to terminal bronchioles, warms, filters and moistens air
Respiratory airway - respiratory bronchioles to alevoli, gas exchange with the blood.

Question 5

What type of epithelium is found in the upper respiratory tract?

Answer 5

Respiratory mucosa

Question 6

Give all the division of the respiratory tract from the trachea onwards.

Answer 6

Trachea
Primary bronchi (main)
Secondary bronchi (lobar)
Tertiary bronchi (segmental)
Bronchioles
Terminal bronchioles
Respiratory bronchioles
Alveolar ducts
Alveolar sacs
Alveoli

Question 7

What is the epithelium type of the lower respiratory tract?

Answer 7

Pseudostratified columnar ciliated epithelium
With numerous goblet cells
Eventually changes to simple sqaumous

Question 8

What type of epithelium lines the roof of the nasal cavity?

Answer 8

Olfactory epithelium

Question 9

What makes up olfactory mucosa?

Answer 9

Pseudostratified columnar ciliated epithelium
Olfactory receptor cells with cilia - bipolar neurons, pass smell information to the brain
Sustentacular cells - provide physical support, nourishment and electrical insulation for olfactory cells
Basal cells - proliferative capacity, can replace both sustentacular and olfactory cells
Bowmans glands - secrete a solvent in which odiferous particles can dissolve.

Question 10

What are some key features of respiratory epithelium?

Answer 10

Ciliated cells
Goblet cells
Basal cells - provide a site of attachment for goblet and cilliated cells to the basement membrane
K-cells/ DNES

Question 11

What are K-cells?
What is their function?

Answer 11

K-cells are diffuse neuroendocrine system cells, they are Kulchitsky cells that contain secretory granules
Secrete peptide hormones such as seratonin and ADH.
Often give rise to small cell lung carcinoma.

Question 12

What is mucocillary clearance?

Answer 12

The self clearing mechanism of the lungs to prevent inhaled pathogens from reaching the sensitive alveoli tissue.
Combined used of cilliated epithelium and goblet cells.
Cilia beats in a unidirectional fashion to move particles towards the pharynx.
Used in defence with the cough reflex.

Question 13

What part of the respiratory system has the most abundant goblet cells?

Answer 13

Terminal bronchus.

Question 14

What is the function of the trachealis?

Answer 14

Is a muscle found posterior to cartilage in the trachea
Contracts to narrow the airway during coughing or forced expiration.
Innervation is supplied by C6-T4.

Question 15

What type of cartilage is found in the respiratory system?

Answer 15

Hyaline cartilage.

Question 16

How might squamous metaplasia occur in the lungs?

Answer 16

Inhaled chemical toxins, viruses or bacteria causes prolonged or repetitive damage to the respiratory epithelium.
It dies and is replaced by stratified squamous epithelium.

Question 17

What happens to cartilage as you travel down the respiratory tract?

Answer 17

Decreases and is replaced by smooth muscle
Trachea have c-shaped rings
Extraplmonary bronchi - have incomplete cartilage rings
Intrapulmonary bronchi - have cartilage plates linked by dense fibrocollagenous bands.
As bronchi get smaller and more peripheral the amount of cartilage decreases ad is concentrated at bifurcations.

Question 18

What are chondrocytes?

Answer 18

Make up the structural components of cartilage.

Question 19

Overview of histological changes in the respiratory system>

Answer 19

Decreased cartilage
Increased smooth muscle
Increased elastic fibres
Decreased mucus glands
Epithelium changes from pseudostratified to simple sqaumous.

Question 20

What type of epithelium may be found in the segmental (tertiary) bronchi?

Answer 20

Simple columnar or simple cuboidal.

Question 21

What does the number of segmental bronchi also relate to?

Answer 21

The number of bronchopulmonary segments in the lungs.

Question 22

What are some features of terminal bronchioles?

Answer 22

No cartilage
Fewer goblet cells
Clara cells distally

Question 23

What are clara cells?
What is their function?

Answer 23

A non ciliated secretory cells
Secrete protective and functional substances, protect against toxins
Type 2 alveolar cells - secrete surfactant.
Mainly found in the respiratory bronchiole

Question 24

How does the epithelium cell type changes down the respiratory tract?

Answer 24

From nasal cavity to secondary bronchi is pseudostratified
Primary bronchioles starts to transition to simple columnar and simple cuboidal
Terminal bronchioles- complete simple cuboidal
Respiratory bronchioles - starts to becomes simple squamous
By alveolar ducts is complete simple squamous.

Question 25

What are pneumocytes?
What are the different types?

Answer 25

Pneumocytes - cells found in the alveolar section of the lungs.
Type 1 - flat, share a basal lamina with the endothelium for gas exchange with the blood
Type 2 - round, secrete surfactant.

Question 26

What is meant by the respiratory lobule?

Answer 26

The terminal bornchiole

Question 27

What is meant by the acinus?

Answer 27

The respiratory bronchiole onwards in the respiratory tract.

Question 28

What is the purpose of surfactant in the lungs?
What is important about it in newborn children?

Answer 28

Reduces surface tension and prevents the alveolar walls from sticking together during expiration

Surfactant occurs during the last few months of development in the uterus, a premature baby will have insufficient surfactant, will suffer from respiratory distress syndrome,
This is treated with positive pressure ventilation, exogenous surfactant or giving the mother corticosteroids to stimulate surfactant production before birth.

Question 29

How do the different types of pneumocytes vary in shape and structure?

Answer 29

Type 1: 95% of alveolar surface, extremely thin, with flattened nuclei.
Type 2: 60% of total cells but only 5% of the surface, have rounded nuclei.

Question 30

What makes up the blood gas barrier in the lungs?

Answer 30

Found in the alveoli.
Type 1 pneumocyte and endothelium with their fused basement membranes.

Question 31

What is the function of alveolar pores (of Kohn)?

Answer 31

Allows air in the alveoli to circulate between different alveolar, useful if the pathway into one alveoli is blocked.
This allows air pressure to equilibrate across the lungs
Are also used by pathogens to spread to different regions of the lungs.

Question 32

What can be found in the interstitial space of alveoli?

Answer 32

Fibroblasts
Collagen
Elastic fibres
Capillaries

Question 33

What are the progressive consequences of squamous metaplasia in the lungs?

Answer 33

Development of stratified sqaumous epithelium, reduces lung function
Overtime may becomes dysplasia, eventually cancer in situ or carcinoma.
A well defined tumour mass can block the bronchus airway.

Question 34

What are some features of respiratory submucosa?

Answer 34

BALT - bronchus associated lymphoid tissue
Submucosal glands

Question 35

Where is the start of the intra-pulmonary system?

Answer 35

Secondary bronchus

Question 36

Where in the respiratory system do goblet cells and glands stop?

Answer 36

Stop rather abruptly at the junction between secondary bronchus and bronchioles.