Host Defence In The Lung: Non-Immune Mechanisms Flashcards
What are the functions of the lungs?
Respiration:
Ventilation and gas exchange: O2, CO2, pH, warming and humidifying
Non-respiratory functions:
Synthesis, activation and inactivation of vasoactive substances, hormones, neuropeptides
Lung defence: complement activation, leucocyte recruitment, host defence proteins, cytokines and growth factors
Speech, vomiting, defecation.
Why are respiratory infections so comparatively rare?
Because of host defences
Why are respiratory infections so comparatively rare?
Because of host defences
What host defences are found in the lungs?
Intrinsic: Always present: Physical and chemical. Apoptosis, autophagy, RNA silencing, antiviral proteins
Innate defence: Induced by infection (Interferon, cytokines, macrophages, NK cells
Adaptive immunity: Tailored to a pathogen (T cell, B cells)
Where do host defence functions run?
Function throughout the respiratory tract and involves the epithelium
What is the epithelium?
A tissue composed of cells that line the cavities and surfaces of structures throughout the body.
Many glands are also formed from epithelial tissue.
It lies on top of connective tissue, and the two layers are separated by a basement membrane.
What is the respiratory epithelium?
The respiratory epithelium serves to moisten and protect the airways.
It also functions as a barrier to potential pathogens and foreign particles, preventing infection and tissue injury by action of the mucociliary escalator.
What are chemical epithelial barriers?
Multiple molecules secreted from the epithelium that play a role in host defence
These are chemical epithelial barriers:
antiproteinases
anti-fungal peptides
anti-microbial peptides
Antiviral proteins
Opsins
Produced by most (all?) epithelial cells
An additional nonspecific defense mechanism is the endogenous commensal (non-pathogenic) bacterial flora (microbiota)
What does the host defence in the respiratory tract rely on?
Host defence in the respiratory tract relies on more than epithelial cell products - physical barriers (mucus) and products of the submucosal glands are important
How is mucus used for host defence?
Airway mucus is a viscoelastic gel containing water, carbohydrates, proteins, and lipids.
It is the secretory product of the mucous cells (the goblet cells of the airway surface epithelium and the submucosal glands).
Mucus protects the epithelium from foreign material and from fluid loss
Mucus is transported from the lower respiratory tract into the pharynx by air flow and mucociliary clearance.
What direction do cilia beat in?
Cilia beat in directional waves to move the mucus up the airways
What is a cough?
Cough is an expulsive reflex that protects the lungs and respiratory passages from foreign bodies
Causes of cough:
- Irritants (smokes, fumes, dusts etc)
- Diseased conditions (COPD, tumors etc)
- Infections (influenza)
What are the different pathways of coughs?
Afferent limb - includes receptors within the sensory distribution of the trigeminal, glossopharyngeal, superior laryngeal, and vagus nerves
Efferent limb - includes the recurrent laryngeal nerve and the spinal nerves
What is a sneeze?
Involuntary expulsion of air containing irritants from the nose
Causes of sneezing:
- Irration of nasal mucosa
- Excess fluid in airway
What is photic sneeze reflex?
Also known as solar sneeze reflex
Sneezing when looking at a bright light
Affects up to one third of the population
