functional histology of the RT

Question 1

where is the conducting zone and what is its funciton (5)

Answer 1

from the nose to the bronchioles;
function:
1. passage of air from environment to lungs;
2. airway protection;
3. air humidification and warming;
4. smell;
5.speech

Question 2

what is the structure of the conducting zone and how does this allow it to achieve its function

Answer 2

made of cartilage and muscle - allows rigidity but also flexibility of the airways, makes them resistant to compression + collapse but also allows for expansion during breathing; trachea has C shaped cartilage to allow for swallowing

cartilage not present in bronchioles

Question 3

what is Bernoulli’s principle

Answer 3

an increase in the speed of a fluid occurs simultaneously with a decrease in static pressure or a decrease in the fluid’s potential energy

Question 4

how does Bernoulli’s principle relate to the lungs

Answer 4

high flowing air = decreased pressure and so anything with higher pressure around it will collapse in (i.e. air in trachea)

Question 5

why do squaemous epithelial cells line the oesophagus

Answer 5

they are v resisitant/robust and the oesphagus is subject to many force/temperature extremities so these robust cells are needed

Question 6

what are the 3 components of the mechanical cellular barrier for the conducting zone

Answer 6

1. nasal hair;
2. ciliated epithelium;
3. mucous secreting cells (goblet)

Question 7

what are the 4 components of the immunological barrier for the conducting zone

Answer 7

1. mucosal associated lymphoid tissue (MALT - thought to be acquired in response to antigenic stimulation, often found at bifurcations)
2. Waldeyer’s ring - tonsils, adenoids, and other lymphoid tissue, contain lymphocytes
3. dense lymphoid tissue in the nasopharynx
4. bronchial epithelial cell + serous cell secretions (lysozomes, IgA, lactoferrin etc.)

Question 8

what are 3 components of the anatomical mechanical protection of the conducting zone

Answer 8

1. cough reflex
2. swallow reflex
3. gag reflex

Question 9

what tissue has a high density of neural receptors that stimulate the cough reflex

Answer 9

carina

Question 10

what nerve controls the cough reflex and what can cause a loss of reflex

Answer 10

vagus;
can be lost in stroke, LMN lesion, anesthetics, alcohol/drug use etc.

Question 11

what does the swallow reflex do

Answer 11

allows the epiglottis to cover the larynx to prevent aspiration

Question 12

what does the gag reflex do and where is it stimulated

Answer 12

reflex contraction at the back of the throat to prevent foreign bodies entering the upper airway;
stimulated via touching the back of the thorat, tonsils, ulva etc.

Question 13

where does humidification/warming mostly occur and why is it important (2)

Answer 13

in the nasal sinuses;
important because :
cold-dry air impairs muco-ciliary function -> damages the delicate respiratory type epithelium; it induces thicker mucin therefore the removal of pathogens may be compromised
Upper airways immunological function also compromised at lower temperatures

Question 14

how does humidification of air occur

Answer 14

evaporation of watery mucous from seromucinous glands allows for 100% humidity

Question 15

how does warming of air occur

Answer 15

transfer of heat from warm blood to the air -> nasal sinuses are highly vascular, this is combined with increased turbulence of air in the sinuses allows for increased contact of air with vasculature => maximising heat transfer

Question 16

what is the function of the Bowman gland

Answer 16

secretes water mucous that dissolves odours -> this is then picked up by epithelial cells (i.e. allows for smell)

Question 17

what are the 3 phases of speech, what part of the RT is involved in each and what are symptoms of their dysfunction

Answer 17

1. respiration - lung function -> stuggling to finish sentances, SOB, deep gasping breath, cough;
2. phonation - laryngeal function -> horse voice;
3. articulation - vocal tract -> stroke

Question 18

how can enlarged thyroid cause a horse voice

Answer 18

it can compress the recurrent laryngeal nerve which affects larynx function

Question 19

what are the 6 cartilages in the layrnx and what is their function

Answer 19

Three paired cartilages (corniculate, cuneiform and arytenoid) and three unpaired (cricoid, thyroid and epiglottis): function to maintain a patent airway for gas transfer, movement with the vocal muscles allows for speech

Question 20

what cells line the true vocal chords and why does this differ from the rest of the RT

Answer 20

squaemous epithelium -> true vocal chords experience high forces due to trubulent flow over them so cells undergo metaplasia and differentiate into the more robust squaemous epithelium

Question 21

how does the larynx anatomy affect laryngeal cancer progression

Answer 21

Early stage laryngeal carcinoma is limited by endolaryngeal structures (connective tissue membranes) and there is little vasculature

Question 22

why is structural support lost in the gas transfer zone

Answer 22

to allow for maximal expansion

Question 23

what are clara cells (bronchiolar exocrine cells) and what is their function (3)

Answer 23

non-ciliated secretory cells in the small airways and trachea;
function: modulation of bronchiolar inflammation, secrete endothelin (bronchoconstrictor), have stem cell capability (ciliated/mucous cells if exposed to irritants)

Question 24

what does the interstitium comprise of? (8)

Answer 24

collagen, elastin fibres, fibroblasts myofibroblasts, pericytes, histiocytes, mast cells and the odd neuroendocrine cell

Question 25

morphology and role of type 1 pneumocytes

Answer 25

flattened nuclei and thing; provide a thin layer for gas exchange but at the same time form a barrier to prevent fluid loss; less numerous

Question 26

morphology and role of type 2 pneumocytes

Answer 26

larger darker nuclei, more numerous; produce surfactant

Question 27

what are Lambert’s canals

Answer 27

tubular connections which connect terminal and respiratory bronchioles with adjacent peribronchial alveoli

Question 28

pressure and location of pulmonary arteries

Answer 28

low pressure system;
Lie in close proximity to the airways, Main pulmonary arteries arise from the bifurcation of the pulmoary trunk shortly after its origin from the right ventricle and divide to follow the lobar bronchi

Question 29

what is the function of pulmonary capillaries and how is their structure suited to this

Answer 29

function - gas exchange;
structure - continuous type endothelium so have a larger diameter than in systemic circulation; Pulmonary arteries divide into the pulmonary capillaries which form a meshwork situated in the alveolar walls -> incr SA for gas exchange

Question 30

what arteries supply the lungs themselves and where do they arise/drain

Answer 30

bronchial arteries;
arise from the systemic circulation, drains into the azygos venous system via the bronchial veins

Question 31

role of the lymphatic system in the lungs

Answer 31

1. fluid control system prevents pulmonary oedema
2. Removes particles (which is why hilar lymph nodes are black)
3. ! Immune control; allows the transfer of macrophages to present pathogens to the hilar lymph nodes, Commence in the cenriacinar regions not the alveoli

Question 32

what is the pleura, what are the 2 membranes and what is their structure

Answer 32

A pair of serous membranes lining the thoracic wall (parietal) and lungs (visceral); lined by mesothelial cell lining, connective tissue submesothelium and an elastin layer (2 layers of elastin on visceral as it expands more)

Question 33

what do mesothelial cells secrete

Answer 33

Hyaluronic acid - a key component of the extracellular matrix of the lungs. A unique attribute of HA is its water-retaining properties

Question 34

why are pores of Kohn important to consider in infectio/malignancy

Answer 34

provides channels for the spread of pneumonia and also for cancer that grows along the walls of the alveoli (lepidic pattern)