20110131 10 respiratory notes

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LECTURE OBJECTIVES: RESPIRATORY SYSTEM 1. Descnl>e the cells ofthe respiratory epithelium and know their function.

2. Know the cells ofthe olfactory epithelium and understand how these cells function to sense smell.

3. Traveling along the respiratory track from the nasal cavity to the alveoli, various segments have important histological characteristics. Be able to describe and distinguish the epithelium, unique cells, and the presence/absence ofcartilage, muscle, and glands for the various airway segments.

4. Understand the structure and function oftype I and type ll cells ofthe alveolar system and how these cells contribute to the blood-air barrier.

5. The respiratory vasculature functions to both re-oxygenate the blood and also to supply the respiratory tissue with oxygenated blood. Be able to describe the components ofthis network and their respective functions.


Overall Structure and Function Air conduction, air filtration, gas exchange, smell, speech, endocrine, immune response Two anatomical regions: Conducting-Nasal cavity to terminal bronchioles; function to condition inspired air Respiratory-Respiratory bronchioles to alveoli; function for respiratory gas exchange

Respiratory epithelium = majority of epithelium, ciliated pseudostrati:fied columnar -Ciliated cells = most abundant cell; mucus transport -Goblet cells = contribute to mucus production through their production ofmucin glycoproteins; number increases during chronic irritation -Brush cells =microvilli; nerve endings -Basal cells= stem cells Metaplasia = transformation ofepithelium from one type to another; example is when respiratory epithelium changes to stratified squamous due to chronic insult by turbulent flow (chronic cough via bronchitis or smoking) Olfactory epithelium= located on the roofofthe nasal cavity (superior choncha); pseudostratified

-Olfactory cells =bipolar neurons, ciliated (with odorant receptors)

-Supporting cells = microvilli, apical nucleus

-Basal cells = single layer at epithelium base, stem cell

-Bowman's gland= serous glands; secretions contain odorant-binding protein (OBP) which binds odorant molecules, carries them to receptors on specialized cilia

Conducting region Nasal cavity= paired chambers separated by septum; comprised ofvestibule and nasal cavity -Vestibule= contains vibrissae (nasal hairs); transition from keratinized stratified squamous epithelium from skin to respiratory epithelium ofthe remainder ofthe tract; sebaceous glands -Nasal cavity (fossae)= three conchae (turbinates) the superior one contains olfactory epithelium; function to produce turbulent air flow; highly vascularized Paranasal sinuses= cavities in facial bones; mucus travels to nasal cavity; prone to infection (sinusitis). Phacynx = connects the nasal cavity to the larynx; segments are the nasophacynx and oropharynx Larynx = connects pharynx to trachea; irregular shaped plates ofcartilage (hyaline & elastic) Vestibular folds = (also called false vocal cords); two upper mucosal folds projecting into the lumen ofthe larynx Vocal folds = (also called vocal cords); two lower mucosal folds projecting into lumen ofthe larynx; each fold contains a supporting ligament and skeletal muscle (vocalis muscle) which controls tension to produce sound; covered by stratified squamous epithelium (better at resisting abrasion from friction than respiratory epithelium) Trachea= from base oflarynx. to start ofbronchial tree; hyaline cartilage rings in 'C' shaped pattern; perichondrium attached to trachealis muscle (smooth muscle) which serves to contract lumen Bronchial Tree = from bronchi to terminal bronchioles; progressive transition to smaller diameter Primary bronchi {bronchus)= two; one enters each ofthe lungs at hilum Bronchi= one for each lobe ofthe lung (two lobes in left lung, three in right); irregular cartilage plates which decrease in size/number as tube gets smaller; contains circular layer ofsmooth muscle; abundant mucous and serous glands Bronchioles = no glands or cartilage but still has smooth muscle; some goblet cells; progressive transition from ciliated pseudostrati:fied columnar epithelium to ciliated simple columnar epithelium to cuboidal; final portion is called terminal bronchiole Clara cells = secrete alveolar fluid which serves as the aqueous phase ofsurfactant Asthma = airway hyperresonsiveness; bronchoconstriction ofsmooth muscle bundles

Respiratory region Respiratory bronchioles =two or more arise from each terminal bronchiole; similar to terminal bronchiole except wall is interrupted by alveoli; Clara cells can be present Alveolar ducts = region oftube at which the respiratory bronchiole wall contains only alveoli; lined by squamous alveolar cells; contains smooth muscle and both elastic and reticular fibers Alveolar sacs = collection ofalveoli at end of alveolar duct Alveoli = saclike evaginations ofrespiratory structure; 02 and C02 exchange; lined by simple squamous epithelial cells (type I cells) and cuboidal cells (type II cells) Interalveolar septum =wall separating two adjacent alveoli; display capillaries to create a minimal barrier to gas exchange; comprised of two layers ofsquamous epithelium between which are capillaries, connective tissue, leukocytes; alveolar pores connect adjacent alveoli; Emphysema = permanent enlargement and wall destruction of air spaces distal to the terminal bronchioles. Breakdown is primarily due to loss ofelasticity (elastic fibers) via elastase (from neutrophils ). Various types classified by location ofeffect (either respiratory walls only or both respiratory walls and alveoli). Smoking is major cause Pneumonia = bacterial infection in alveoli leading to inflammation and fluid accumulation

Respiratory lecture notes PageS of6

Cells ofthe alveolar system -Type I {squamous alveolar cells)= flat cells that line majority ofalveolar surface; provide a minimum thickness barrier for gas exchange; contain both desmosomes and occluding junctions -Type II (great alveolar or 'niche' cells) =cuboidal cells located in comers ofalveoli (groups of 2-3 cells); contain lamellar bodies which secrete pulmonary surfactant (acts to lower surface tension such that less pressure is required to keep alveoli open); can differentiate to replace injured type I cells

Neonatal respiratory distress syndrome (RDS) = surfactant deficiency in premature infants (production begins at 35th week ofgestation); collapse of alveolar walls; treated with corticosteroids which stimulates synthesis of surfactant or artificial surfactant. -Alveolar macrophage (dust cell)= in alveolar septum and alveolar surfaces; remove degraded surfactant; either migrate up the bronchial tree or remain in the alveolar wall for life -Endothelial cells= Thin, no fenestrations; express angiotensin-converting enzyme (important in control ofblood volume/pressure) Alveolar Nucleus of capillary connective endothelial cell tissue Nucleus of alveolar type I cell Alveolus {Alveolar epithelium Alveolar type I cell

Fused basement membranes Respiratory of the alveolar epithelium and membrane the capillary endotheliur Capillary endothelium

a b

Blood-air barrier Separates air in alveoli from blood in capillaries (0.1 to 1.5 microns thick). Three components: 1) Surface lining and cytoplasm ofthe alveolar cells 2) Fused basement membrane ofthe alveolar and endothelial cells 3) Cytoplasm ofthe endothelial cell Respiratory lecture notes Page 6 of6

Pleura Serous membrane covering the lung that serves to facilitate sliding during respiration Two layers: Parietal= lines inner surface ofthoracic cavity Visceral = closely adherent to the lung.

Vasculature Pulmonary arteries = contain deoxygenated blood; thin wall with low pressure; follows bronchial tree and branches to extensive capillary network in interalveolar septum; pulmonary veins (with oxygenated blood) are not closely associated with the bronchial tree and exit to the left atrium Bronchial vessels = supply OA.)'genated blood to bronchial tree up to respiratory bronchioles where it merges with pulmonary arteries ' Lymphatic vessels =follow bronchi and pulmonary vessels, exit lung at the hilum

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