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Flashcards in Respiratory Defences Deck (50):

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

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



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
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
-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