Structure And Function of the Airways Flashcards
What is meant by dichotomous branching?
Where each part of the bronchi splits into two
What does the cartilage around the bronchi provide?
Mechanical stability
What is the main unbranched part of the airway called?
Trachea
What is the first branch of the trachea called?
Primary bronchus
What is the carina?
A ridge at the base of the trachea (windpipe) that separates the openings of the right and left main bronchi (the large air passages that lead from the trachea to the lungs).
What is an alveolar duct?
Ducts that connect the alveolar sacs to the bronchioles
Do the respiratory bronchioles contain cartilage?
no - they are non-cartilaginous
What do Type II Pneumocytes secrete and why?
Surfactant - in order to reduce surface tension
What happens to Type II cells if Type I cells become damaged?
They form type 1 cells
What do the anti-proteases produced by Type 2 pneumocytes do?
They degrade foreign proteases which may have entered into the airways
Which type of alveolar cell is involved in xenobiotic metabolism?
Type 2
Describe the structure of Type 1 alveolar cells?
They are thin, and very flat that form a barrier between alveolus and capillaries
What percentage of the alveolar surface do type 1 cells cover?
95%
What percentage of the alveolar surface do type 2 cells cover?
5%
Are there more type 1 or type 2 alveolar cells?
Type 2
What are the two basic functions of the respiratory airway?
Conducting oxygen to the alveoli and conducting carbon dioxide out the lungs
What are the three things which facilitate the efficient gas exchange?
- Mechanical stability from cartilage
- Control of calibre from smooth muscle
- Protection and cleaning to remove foreign particles
What are the three regions of the pharynx?
Nasopharynx, oropharynx and laryngopharnx
What is the pharynx?
A common passageway for food, liquids and air
What do the conchae found in the nose do?
They contribute to the warming and humidification of intra-nasally-inhaled air
Why must the air be warmed before being breathed in?
Cool air damages the alveoli
What property of the conchae makes them able to humidify nasally inhaled air?
They are highly vascular
What filters out large particles from nasally inhaled air?
Nasal hairs
What is the main function of the goblet cells?
To produce mucus
What are the 7 types of airway cell types?
Lining cells Contractile Secretory Neuroendocrine Connective tissue Vascular Immune
What is contained within the granules found in the goblet cells?
Mucin
Why do the cillia contain many mitochondria?
They need ATP to power their movement
What happens after the granules recieve a stimuli tht they need to secrete their mucin?
The secretory cells take on alot of water, causing the granules to expand and release their mucus
What part of the granule attracts the large volume of water?
The glycans
What type of secretion do mucins show?
Constituitive
What can stimulate mucin secretion?
Dust and smoke
What is mucocilliary clearance?
The process by which mucus is swept by the cilia of the respiratory epithelium and propelled out the lungs and into the pharynx which results in the removal of debris and pathogens from the airways
What do mucous cells in the airways secrete?
Mucous
What do serous cells in the airways secrete?
Anti-bacterial enzymes like lysozyme
What is the 9+2 arrangement?
Refers to how the microtubules are arranged in the cillia
Helps the cilia to move rhythmically
How many cilia are there per ciliated cell?
Approx 200
What is the name given to the rhythm which cilia move by?
Metachondral rhythm
What does nitric oxide synthase do?
produces nitric oxide
What does nitric oxide do?
Interacts with the calcium ions to facilitate the beating of the cilia
What is the purpose of smooth muscle in the airways?
So that it an contract to stop accidentally inhaled particles from going to far down which could result in choking - contraction means it can be coughed up
What does the smooth muscle in the airways secrete?
Mediators, cytokines and chemokines
What are some bronchoconstrictor mediators that are released from mast cells?
Histamine, cys-LTs and PGD2
what are mitogens?
Peptides that induce cell division
What do fibrotic mediators do?
Thicken the tissue
What is the blood flow levels to the airway mucosa?
100-150mL/min/100g
Where do bronchial arteries arise from?
Many sites on the aorta and intercostal arteries
How does the blood return from tracheal circulation?
Via systemic veins
How does blood return from bronchial circulation?
Via bronchial and pulmonary veins
What are the function of the tracheo-bronchial circulation?
- gas exchange
- warming and humidification of air
- clears inflammatory mediators
- clears inhaled drugs
- supplies airways tissue with inflammatory cells and proteinaceous plasma
What is plasma exudation?
The leak of plasma into the airway tissue and lumen
What are the four mechanisms of the control of airway function?
Nerves
Proteases
Reactive gas species eg NO
Regulatory and inflammatory mediators
What type of control is the airway function under?
Parasympathetic
What effect does nitric oxide gas have on the smooth muscle in the airway?
It causes it to relax
What is the predominant parasympathetic neurotransmitter in the airway?
Acetylcholine
What does acetylcholine regulate?
Bronchoconstriction and mucus secretion
How many mediators do regulatory-inflammatory cells produce?
They can produce more than 1
What are the regulatory-inflammatory cells which are found in the airways?
Eosinophils, Neutrophils, Macrophages, Mast cells and T Cells
What are the functions of he regulatory-inflammatory cells found in the airways?
Contraction and relaxation of smooth muscle Secretions Plasma exudation Neural modulation Chemotaxis Remodelling
What percentage of the population suffers from ashtma?
5%
What event is common with asthma, COPD and cystic fibrosis?
An increase in airway inflammation
Why is it helpful for surfactant to be released by the alveolar cells?
Surfactant helps to create a moist surface for gas exchange to occur over as it is easier for oxygen to diffuse across the alveolar membranes when dissolved in a liquid
How does alveolar surfactant ensure that all the alveoli inflate at roughly the same time?
When the alveoli inflate with air, the surfactant becomes spread out. Smaller alveoli have more surfactant per area which reduces surface tension and allows faster inflation; eventually they all inflate at the same time
What is xenobiotic metabolism?
The metabolism of Nox-ous chemicals which might get into the airways