functional histology of the RT Flashcards
where is the conducting zone and what is its funciton (5)
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
what is the structure of the conducting zone and how does this allow it to achieve its function
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
what is Bernoulli’s principle
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
how does Bernoulli’s principle relate to the lungs
high flowing air = decreased pressure and so anything with higher pressure around it will collapse in (i.e. air in trachea)
why do squaemous epithelial cells line the oesophagus
they are v resisitant/robust and the oesphagus is subject to many force/temperature extremities so these robust cells are needed
what are the 3 components of the mechanical cellular barrier for the conducting zone
- nasal hair;
- ciliated epithelium;
- mucous secreting cells (goblet)
what are the 4 components of the immunological barrier for the conducting zone
- mucosal associated lymphoid tissue (MALT - thought to be acquired in response to antigenic stimulation, often found at bifurcations)
- Waldeyer’s ring - tonsils, adenoids, and other lymphoid tissue, contain lymphocytes
- dense lymphoid tissue in the nasopharynx
- bronchial epithelial cell + serous cell secretions (lysozomes, IgA, lactoferrin etc.)
what are 3 components of the anatomical mechanical protection of the conducting zone
- cough reflex
- swallow reflex
- gag reflex
what tissue has a high density of neural receptors that stimulate the cough reflex
carina
what nerve controls the cough reflex and what can cause a loss of reflex
vagus;
can be lost in stroke, LMN lesion, anesthetics, alcohol/drug use etc.
what does the swallow reflex do
allows the epiglottis to cover the larynx to prevent aspiration
what does the gag reflex do and where is it stimulated
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.
where does humidification/warming mostly occur and why is it important (2)
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
how does humidification of air occur
evaporation of watery mucous from seromucinous glands allows for 100% humidity
how does warming of air occur
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
what is the function of the Bowman gland
secretes water mucous that dissolves odours -> this is then picked up by epithelial cells (i.e. allows for smell)
what are the 3 phases of speech, what part of the RT is involved in each and what are symptoms of their dysfunction
- respiration - lung function -> stuggling to finish sentances, SOB, deep gasping breath, cough;
- phonation - laryngeal function -> horse voice;
- articulation - vocal tract -> stroke
how can enlarged thyroid cause a horse voice
it can compress the recurrent laryngeal nerve which affects larynx function
what are the 6 cartilages in the layrnx and what is their function
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
what cells line the true vocal chords and why does this differ from the rest of the RT
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
how does the larynx anatomy affect laryngeal cancer progression
Early stage laryngeal carcinoma is limited by endolaryngeal structures (connective tissue membranes) and there is little vasculature
why is structural support lost in the gas transfer zone
to allow for maximal expansion
what are clara cells (bronchiolar exocrine cells) and what is their function (3)
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)
what does the interstitium comprise of? (8)
collagen, elastin fibres, fibroblasts myofibroblasts, pericytes, histiocytes, mast cells and the odd neuroendocrine cell
morphology and role of type 1 pneumocytes
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
morphology and role of type 2 pneumocytes
larger darker nuclei, more numerous; produce surfactant
what are Lambert’s canals
tubular connections which connect terminal and respiratory bronchioles with adjacent peribronchial alveoli
pressure and location of pulmonary arteries
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
what is the function of pulmonary capillaries and how is their structure suited to this
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
what arteries supply the lungs themselves and where do they arise/drain
bronchial arteries;
arise from the systemic circulation, drains into the azygos venous system via the bronchial veins
role of the lymphatic system in the lungs
- fluid control system prevents pulmonary oedema
- Removes particles (which is why hilar lymph nodes are black)
- ! Immune control; allows the transfer of macrophages to present pathogens to the hilar lymph nodes, Commence in the cenriacinar regions not the alveoli
what is the pleura, what are the 2 membranes and what is their structure
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)
what do mesothelial cells secrete
Hyaluronic acid - a key component of the extracellular matrix of the lungs. A unique attribute of HA is its water-retaining properties
why are pores of Kohn important to consider in infectio/malignancy
provides channels for the spread of pneumonia and also for cancer that grows along the walls of the alveoli (lepidic pattern)
