RESPIRATORY

SYSTEM

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Ika Murti Harini

Histology-FK Unsoed

Conduction Area: Warming, Moistening, Filtration

Nasal Cavities

Naso & oro-pharynx

Larynx

Trachea

Bronchi

Bronchioles

Respiratory Area: Gas Exchange

Respiratory bronchioles

Alveolar ducts

Alveolar Sacs

Alveoli

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FUNCTION

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Respiratory Epithelium

Most of the conducting portion is lined with ciliated pseudostratified columnar epithelium known as respiratory epithelium

This epithelium has at least five cell types, all of which touch the thick basement membrane

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Nasal Cavity

Vestibule

Respiratory Portion Mucous layer

Lamina propria

conchae

Olfactory area Mucous layer

Lamina propria

Nasal Sinuses

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Vestibule Non-keratin Stratified squamous epithelium-ciliated pseudostratified

columnar

Vibrissae

Sebaceous glands

Respiratory Portion : mucous Ciliated Pseudostratified columnar epithelium

Goblet Cells (+)

Brush Cells

Columnar, short microvilli, Synapse branch, General sensory stimulation

Small granule cells

Neuroepithelial cells, Contain norepinephrine or neuropeptides, Reflex regulating of airway caliber or vasculature

Stem cells-precursor epithelial cells 3/2/2015 6

Nasal Cavity

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Branched Tubuloalveolar glands (mixed)

Mucous

Serous

Attached to periosteum of underlying bones

Rich vascular network

Blood flow perpendicular to air flow (warm inspired)

Arteriovenous anastomoses

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Respiratory portion: lamina propria

Shell-fish shaped

Increase surface area (moisture & warmth)

Turbulence

Allergy, common cold caused enlargement airway obstruction

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Respiratory portion: Conchae

OLFACTORY AREA

The olfactory chemoreceptors are located in the olfactory epithelium

a specialized region of the mucous membrane covering the superior conchae at the roof of the nasal cavity

Mucous layer

Lamina Propria

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OLFACTORY AREA

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Ciliated pseudostratified columnar epithelium No Goblet Cells Bipolar Neurons

Dendritic process Knob like olfactory vesicle-cilia Axon-fila olfactoria Life span about a month

Supporting (Sustentacular) cells Tall Columnar cells Apical nuclei Numerous microvilli Secretory Lipofuchsin granules (impart yellow/brown color to epithelium) Functionaly similar to glia

Basal Cells nuclei below level of olfactory cell nuclei Source of replacement olfactory cells

Brush cells

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MUCOUS LAYER

composed of a richly vascularized, loose to dense, irregular collagenous connective tissue

firmly attached to the underlying periosteum

Branched tubuloalveolar serous glands (Bowmans glands)

Lipofuchsin granules in gland cells (impart yellow/brown color to epithelium)

Short ducts lined cuboidal cells become squamous

Myelin fibers of trigeminal nerve

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LAMINA PROPRIA

Olfactory epithelium

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Lined with pseudostratified columnar epithelium

Goblet cell (+) mucous secretion

Small less well developed glands

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Nasal sinuses

MEDICAL APPLICATION

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Ciliated pseudostratifed columnar epithelium

Stratified squamous epithelium in selected areas

lingular surface epiglottis

vocal cords

Branched tubuloalveolar glands (lamina propria)-except epiglottis

Larynx-connective tissue rich in mast cells

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Pharynx-Larynx

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Cat, Bouin's, AFT, 5.5

LARYNX; Vocal folds

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Larynx

Trachea

Ciliated pseudostratified columnar epithelium-unless chronic irritation

Lamina Propria

Submucosa

Cartilaginous layer

Adventitia

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Ciliated pseudostratified columnar epithelium-unless chronic irritation Ciliary escalator Goblet Cells, brush cells, small-granule cells, basal cells Thick basement membrane

Lamina Propria Collagenous fibers, elastic rich Very Cellular-lymphocytes, plasma cells, mast cells,

eosinophil, fibroblasts Submucosa

Relatively loose CT Blood vessels and lymphatics Mucous-serous secreting glands Blends into perichondrium

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Light photomicrograph of the trachea in a monkey (270)

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Rat, Helly's fluid, H. & E., 612 x.

TRACHEA Lamina propria

Cartilaginous layer 16-20 C shaped cartilages Hyaline cartilage Closed posteriorly- fibroelastic connective

tissue and smooth muscle smooth muscle -trachealis

Patency and flexibility May ossify

Adventitia Blends adjacent structures Fat cells, nerves, blood vessels

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HYALINE CARTILAGETrachea

A. Rat, Helly's fluid,

Mallory's stain, 612 x.

B. Rat, Helly's fluid,

toluidine blue and

erythrosin, 612 x

A B

Right Bronchus = wider, straighter

Branch : Secondary then tertiary

Tertiary Bronchi

10 right

8 left

Roughly 9-12 branching generations to reach bronchioles

Bronchial Wall

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Bronchus

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Bronchial tree

Mucosa

Muscularis

Submucosa

Cartilage layer

Adventitia

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Bronchus

Mucosa Ciliated pseudostratified columnar epithelium Quickly diminishing basement membrane Much reduced lamina propria

Muscularis Becomes continuous Increasingly conspicuous relative to decreasing cartilage

Submucosa Loose CT Both mucous and serous glands Adipose tissue Bronchial arteries

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Cartilage layer Array around circumference

Becomes progressively smaller and fewer

Disappear at bronchioles

Adventitia Moderately dense CT

Blends connective tissues of pulmonary artery, lung parynchyma

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Bronchial wall

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Cat, 10% formalin, H. & E. stain, 162 x.

BRONCHUS AND BRONCHIOLE

1 mm or less Epithelium:

Initially pseudostratified columnar epithelium Reduces to ciliated columnar epithelium Goblet Cells

No cartilage plates No subepithelial glands Relatively thick smooth muscle layer Clara Cells : columnar cells with dome-shaped apices that

have short, blunt microvilli Branch into 5-7 Terminal bronchioles Divides into 2 respiratory bronchioles

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Bronchioles

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BRONCHIOLE

A large bronchiole has the characteristically folded respiratory epithelium (E) and prominent smooth muscle (arrows), but is supported only by fibrous connective tissue (C) with no glands. X140. H&E

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Terminal bronchiole

form the smallest and most distal region of the conducting portion of the respiratory system

the last parts of the air conducting system before the sites of gas exchange appear

Cross-section shows that a terminal bronchiole has only one or two layers of smooth muscle cells. The epithelium contains ciliated cuboidal cells and many low columnar nonciliated cells. X300. PT

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Clara cells

The nonciliated Clara cells with bulging domes of apical cytoplasm contain granules

Functions : secrete components of surfactant which

reduces surface tension and helps prevent collapse of the bronchioles

produce enzymes that help break down mucus locally

The P450 enzyme system of their smooth ER detoxifies potentially harmful compounds in air

produce the secretory component for the transfer of IgA into the bronchiolar lumen

lysozyme and other enzymes active against bacteria and viruses

several cytokines that regulate local inflammatory responses

Clara cells

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Scanning electron micrograph of Clara cells and ciliated cuboidal cells of rat terminal bronchioles (1817).

Transition passageway (conducting and respiratory)

Epithelium

Initially ciliated columnar to cuboidal epithelium

Eventually no cilia-disappear after goblet cells and glands

Clara cells eventually predominate

Scattered alveoli

Occasional brush or dense-core granule cells

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Respiratory Bronchiole

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Rat, glutaraldehyde-osmium fixation, toluidine blue stain, A. 50 x, B. and C. 162 x.

RESPIRATORY BRONCHIOLE, DUCT, AND ALVEOLI

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Alveolar Duct Extended passageway lined by alveoli Alveolar rim ringed by smooth muscle

Alveolar Sac Space surrounded by cluster of alveoli Termination of alveolar duct

Alveoli 100-150 million/lung Thin walled (.2 mm) Supported by collagenous and elastic framework

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Respiratory portion of the respiratory system

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ALVEOLAR DUCT AND ALVEOLAR SACS

Rat, glutaraldehyde-osmium fixation,toluidine blue stain, A. 162 x, B. 612 x.

Alveolar epithelial cells (Type I alveolar cells, Type I pneumocytes)

Great Alveolar cells (Type II alveolar cells (cuboidal-mitotic), septal cells, Type II Pneumocytes

Brush cells (very rare)

Alveolar macrophages (Dust Cells)

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Alveolar cells

Extremely thin squamous epithelium

95% surface of alveoli but represent only 40% of cells

Zonulae occludentes-resist fluid leakage into alveolus

Some micropinocytotic vesicles

Alveolar septum

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Type I alveolar cells (Type I pneumocytes)

= The region between adjacent alveoli Alveolar epithelium cells

Basal lamina of alveolar epithelium

Basal lamina of endothelium

Endothelial cells

Alveoli Pores

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Alveolar septum

Scanning electron micrograph of a rat lung displaying a bronchiole (b), small artery (v), and alveoli (d), some of which present alveolar pores

Cuboidal cells

Short microvilli on apical surface

Septal junctions

Equal numbers of type I

Synthezise surfactant

Apical cytoplasm-granule-lamellar bodies

Mitotically active

Possible source of alveolar epithelial replacement

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Type II alveolar cells, septal cells Type II Pneumocytes

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ALVEOLUS

Rat, glutaraldehyde-osmium fixation, toluidine blue stain, 1416 x.

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Alveolar walls

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Alveoli and the blood-air barrier

= Blood-Gas Barrier region of the interalveolar septum that is traversed by O2

and CO2 as these gases go from the lumen of the blood vessel to the lumen of the alveolus, and vice versa

These regions are composed of the following structures : - Surfactant and type I pneumocytes - Fused basal laminae of type I pneumocytes and endothelial cells of the capillary - Endothelial cells of the continuous capillary

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Alveoli and the blood-air barrier

Apical cytoplasm

Reduces surface tension

Prevents alveolar collapse

Reduces energy required for respiration

Broken down extracellularly

Hyaline membrane disease (neonatal respiratory distress syndrome)

Phosphatidylcholine, phospholipids

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Surfactant

Pulmonary surfactant

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synthesized on the RER of type II pneumocytes

modified in the Golgi apparatus and is then released from the trans Golgi network into secretory vesicles, known as composite bodies, the immediate precursors of lamellar bodies

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Dust Cell/Alveolar Macrophages

Migrate over alveolar surface

Scavenge inhaled particulates

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MACROPHAGES Lung; terminal bronchiole

Cat, 10% formalin, H. & E., 324 x.

Bronchial Arteries

Pulmonary Arteries

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Blood Supply