Respiratory Defences Flashcards
The respiratory system is split into 2 zones, Conducting airways (Zone) and Respiratory Airways (Zone):. What are each of these zones comprised of?
Conducting airways (Zone): Nasal cavity Trachea Bronchi Bronchioles
Respiratory Airways (Zone): :
Respiratory bronchioles
Alveolar ducts and Alveoli
Function of the nose
The nose acts to filter large particle (>10μm ;nasal hairs) inspired air.
Warms & humidifies the air-prevents epithelium drying out
Mucosal layer lined with different types of epithelial cells:describe them and what they do
Respiratory epithelium-bathed in aqueous viscous& sticky mucus to trap particles.
Ciliated epithelium have a coordinated beat-mucociliary escalator push material towards naso & oropharyrnx
what stimulates irritant receptors & provoke sneezing & coughing to remove material.
irritant particles
what is the Lamina propria
\: Loose connective tissue Blood vessels and nerves Secretory glands Lymphocytes and other lymphoid cells Rigid components keeping airways open
describe the types of epithelium found in the conducting airways
Pseudostratified with 3 cell types Ciliated epithelial cells-mucociliary escalator Goblet cells (secretory, non-ciliated) Basal cells (act as stem cells, may contribute to structure)
Columnar in nasal cavities, trachea, bronchi; more cuboidal in bronchioles with Club (Clara) cells replacing goblet cells
what is the mucociliary escalator?
Mucus overlies the airway epithelium protects the mucosa
Covered with gel phase over a thin sol phase
Creates a semipermeable barrier & allows exchange of nutrients, H2O, and gases & is impermeable to most pathogens.
Cilia coordinated beating transports particles/cellular debris towards mouth.
Mucus from large bronchi to reach pharynx ~40 min
From respiratory bronchi several days.
what can damage the mucociliary escalator?
by inflammation, smoking, pollution, infections.
what does mucus contain
Anti-proteases e.g. α1-antitrypsin-inhibits proteases released from bacteria & neutrophils
Lysozyme-has anti-bacterial & anti-fungal properties
Anti-microbial properties from Lactoferrin, peroxidases & neutrophil-derived defensins
Above provide non-specific immunity
what productes mucus
goblet cells
what makes up mucus and what is its strucure?
Main component of airway mucus are mucins, which are high molecular wt glycoproteins
how do mucins affect the nature of goblet cells?
they give mucus its gel-like nature
Fluidity & ionic composition of sol phase are cntrolled by what
epithelial cells
features of the tract wall nose
nous plexus, periosteum, bone
features of the tract wall trachae and bronchioles
held open by C-shaped cartilage anterolaterally, smooth muscle (Trachealis) posteriorly
features of the tract wall trachea
(generally 16-20) rings of cartilage
features of the tract wall bronchi
cartilage plates, smooth muscle, blood vessels of systemic circulation (bronchial arteries)
features of the tract wall bronchioles
smooth muscle helical bands
whaat type of cartiage is present in the bronchus?
hyaline cartilage.
what type of epithelium lines the bronchus
ciliated pseudostratified columnar epithelium
smppthe muscle and goblet cells arent presen tin the bronchus, true or false?
false. they are present
what dont terminal bronchial have and what does it have
doesnt: cartilage, glands
does: smooth muscle
describe the eptihelium the the terminal bronchiole
Epithelium in initial portion is ciliated columnar, but becomes cuboid with cilia
Final portion un-ciliated
what is the pathway from the terminating brioloes
Terminal bronchioles lead to respiratory bronchioles, in turn these lead to alveolar ducts, alveolar sacs, as well as individual alveoli
where does gas exchange happen?
1st first respiratory alveoli
describe the diffusion distance between alveoli and pulmonary capillaries
minimal
epithelium in a respiratory bronchiole
has a low simple cuboidal epithelium and a thin coat of interlaced smooth muscle and elastic fibres.
what are the thin evaginations in the respiratory bronchiole
It has thin evaginations in its wall: 1st first respiratory alveoli, where gaseous exchange can take place.
what are Type I pneumocytes
95% of alveolar surface
Highly flattened
Simple squamous epithelium
Form occluding junctions with one another
Barrier to extracellular fluid into alveolus
how is are neighbouring alveoli interconnected
by Pores of Kohn
what is The Blood-gas interface
Type I cells forms thin diffusion barrier –fused with pulmonary capillary endothelium
what is Type II pneumocytes
More numerous; only about 5% of alveolar surface
Cuboidal
Capable of rapid cell division.
Dispersed among type I pneumocytes and form occluding junctions with them
Produce surfactant –reduces surface tension prevents alveoli from collapse
difference between type 1 and type 2 cells
thicker & produce fluid layer that lines alveoli
what does the fluid layer that lines alveoli contain
Fluid contains pulmonary surfactant (phospholipid: dipalmitoyl phosphatidylcholine) in lamellar bodies
what is the function of the fluid layer that lines alveoli
Reduces the surface tension within alveoli
what does the interstitium contain
reticular & elastic fibres; allows elasticity
lymphoid cells
Secreted factors for non-specific defence
A No of factors produced by epithelial cells & other cells or derived from plasma
examples of anti-proteases
α1-antitrypsin-inhibits proteases released from bacteria/neutrophils
what properties have lysozymes
antifungal & bactericidal properties
what are antimicrobial proteins
Lactoferrin, Peroxidases& neutrophil-derived Defensins & Cathelicidins
Immune defence mechanisms:
Leucocytes: neutrophils & lymphocytes present in alveoli
Neutrophils kill bacteria
Alveolar macrophages migrate found throughout the respiratory tract-phagocytose any particles that get this far
Macrophages act as antigen presenting cells & products presented to T & B lymphocytes
Macrophages secrete Interleukins(ILs), Tumour Necrosis Factor (TNF) & chemokines
ILs & TNF activate immune system
Chemokines attract white cells to sites of inflammation
Mast cells-secrete heparin, Histamine, 5-HT & hydrolytic enzymes involved in allergy & anaphylaxis (IgE)
Principal immunoglobulin is IgA.
Natural Killer (NK) Cell
Present in lungs & lymphoid organs
Contains granules with hydrolytic enzymes
1st line of defence against viruses
Secrete interferons & TNFs
T & B lymphocytes migrate to lymph nodes, tonsils & adenoids
Diffuse patches of bronchus-associated lymphoid tissue (BALT) in lamina propria
Antigens presented to T-Lymphocytes by antigen-presenting cells-cascade of cytokines released & a variety of Antibodies produced (Immunoglobulins)
Most important are Dendritic cells
Specialised mononuclear phagocytes
Act as antigen presenting cells
what is a cough
Protective reflexes protect lungs & airways from a variety of foreign materials
Cough Reflex:
Caused by irritation of respiratory tract by gases, smoke & dust
Receptors throughout airways between epithelial cells
Rapidly adapting afferent myelinated fibres in vagus
In trachea leads to cough; lower airways leads to hyperpnoea
Also causes reflex bronchial & laryngeal constrictions
Characterised by deep inspiration followed by forced expiration with closed glottis
Results in expulsion of irritants from respiratory tract
Sneezing Reflex:
Caused by irritation of nasal mucous membrane due to dust particles, debris & excess fluid accumulation
Characterised by deep inspiration followed by forced expiration with open glottis
Results in expulsion of irritant from airways
Irritation of nasal mucous membrane , olfactory receptors & trigeminal nerve endings in nasal mucosa
Afferents from trigeminal & olfactory nerves pass to sneezing centre in medulla
Efferent fibres pass from medulla via trigeminal, facial, glossopharyngeal, vagus & intercostal nerves.
Results in activation of pharyngeal, tracheal & respiratory muscles
Swallowing Reflex:
Initiated by stimuli to dorsum of tongue, soft palate & epiglottis
During swallowing respiration is inhibited-Deglutition reflex
Prevents inhalation of food
Stretch Receptors:
Located in smooth muscle of bronchial walls
Slowly adapting
Afferents ascend via vagus
Stimulation results in inspiration being shorter & shallower
These receptors responsible for Hering-Breuer inspiratory reflex
Lung inflation inhibits inspiratory muscle activity
Deflation reflex-augments inspiratory muscle activity
Normal breathing weak reflex, more active during exercise when tidal vol >1 L; In neonates-protects against over-inflation
Juxtapulmonary (or J )receptors
Located on alveolar & bronchial walls close to capillaries
Afferents unmyelinated C-fibres or myelinated nerves in vagus
activation of Juxtapulmonary (or J )receptors
apnoea (cessation of breathing) or rapid shallow breathing, HR & BP fall, laryngeal constriction & relaxation of skeletal muscles.
J receptors activated by:
-Increased alveolar wall fluid
-Pulmonary congestion & oedema
-Microembolisms
-Inflammatory mediators such as Histamine
Above associated with lung disease
Somatic & Visceral Reflexes
Visceral or somatic pain produce opposite effects on breathing
Stretching intestines or distending gallbladder or bile ducts inhibits breathing
Somatic pain generally causes rapid shallow breathing
Cold H2O on bare skin produces a gasp & increases ventilation rate
Face immersion in H2O (especially Cold) the Dive reflex
Proprioceptors (position/length sensors) in muscles & joints of respiratory muscles detect load on muscles (not diaphragm) and can respond to increased load by modulating respiration
Pain receptors: stimulation often leads to brief apnoea followed by increased breathing
Receptors in trigeminal region & larynx: stimulation gives rise to apnoea or laryngeal spasm
