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Respiratory System

Site of gas exchange

Avenue for heat and moisture loss

Sound / voice production Others:

Immunogenic exposure site

Enzyme conversion Divisions of Respiratory Tract

1. Conducting portion

Transit of air to and from the lungs

No gas exchange

Air filtration and humidification

Nose, pharynx, larynx, trachea, bronchi, bronchioles 2. Respiratory portion

Site of gas exchange

Respiratory bronchioles, alveolar ducts, alveoli

*WHERE GAS EXCHANGE TAKES PLACE BETWEEN THE BLOOD AND INSPIRED AIR. ***CONDUCTING PORTION

1. NOSE 2. PHARYNX 3. LARYNX 4. TRACHEA 5. BRONCHI enters the lungs and undergo several orders of branching.

*RESPIRATORY PORTION

1. RESPIRATORY BRONCHIOLES – the terminal branches of bronchi 2. ALVEOLAR DUCT and myriad alveoli – thin walled, air filled sacs that make up the greater part of parenchyma of

the lungs. 3. ALVEOLI – thin walled air filled sacs that make up the greater part of the parenchyma of the lungs.

NOSE.

bony cartilage covered by the skin and the subcutaneous CT. NASAL SEPTUM. thin, cartilaginous.

o divides the nose interiorly o hyaline cartilage

1. NASAL CAVITY.

o OPENINGS: ANTERIORLY: nares POSTERIORLY: NASOPHARYNX.

o NASAL CAVITIES ARE LINED BY 4 TYPES OF EPITHLIUM:

1. Stratified squamous of the skin with large, stiff hairs that filter out the large foreign particles. 2. Transitional band of non-ciliated cuboidal/columnar epithelium 3. Ciliated pseudostratified columnar epithelium containing GOBLET CELLS that increases in number

from anterior to posterior.

NASAL CAVITY

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4. Sensory olfactory epithelium (thich pseudostratified epithelium) root of the nasal cavity and the

small area of septum and superior cocha

NASAL COCHAE. surface area of each nasal cavity is increased by 3 BONY SHELF like projections from lateral wall

Walls of nasal cavities of hyaline cartilage and bone to keep them open - Consist of 3 regions, anterior to posterior: 1) Vestibule = slight dilation inside the nares. Lined by str. squamous with filtering hairs, sweat and sebaceous glands present 2) Olfactory Region = contains olfactory mucosa, dorsally situated 3) Respiratory Region = contains respiratory mucosa, ventrally situated

LAMINA PROPRIA on lower and middle conchae is: o richly vascularized o arterial blood warms the inspired air o has an extensive venous plexus o thin walled vein become engorged which occludes the airway. o common site for nose bleed.

2. OLFACTORY EPITHELIUM- where olfactory chemoreceptors are located.

o OLFACTORY EPITHELIUM

COMPOSED OF 3 KINDS OF CELLS:

1. SUSTENTACULAR CELLS – o TALL COLUMNAR CELLS WITH STRIATED BORDER AND A CONSPICIOUS TERMINAL WEB. o CYLINDRICAL APEXES AND NARROWER BASES. o APICAL CYTOPLASM –with SER, supranuclear golgi complex, mitochondria and few pigment granules that

gives olfactory epi. a PALE YELLOWISH-BROWN COLOR.

2. OLFACTORY CELLS. NEURO SENSORY NEURONS of the epithlium. o between sustentacular cells o bipolar neurons o nuclei: at level of the supporting cells. o apical: narrowed to thin cylindrical process extending above the surface o terminates in a small, rounded expansion – OLFACTORY BULB or KNOB

o OLFACTORY BULB:

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projects somewhat above the apices of the surrounding sustentacular cell OLFACTORY CILIA –6 to 8 nonmotile basal bodies that is parallel to the surface epithelium,

very long and atypical

3. BASAL CELLS – o basal location, triangular o Small deeply basophilic o Between olfactory and sustentacular cells o Divide and differentiate into either susentacular or olfactory cells

gland of bowman. large tubuloalveolar serous gland in lamina propria of olfactory epithelium. VEMORONASAL ORGAN – second of smaller olfactory ephithelium on the nasal septum.

o lack sensory cilia but have small microvilli.

PARANASAL SINUSES o Cavities within bones, named accordingly: frontal, ethmoidal, sphenoidal and maxillary o Lined with ciliated epithelium that move mucus blanket toward nasal cavity

o Thin lamina propria indistinct and tightly adherent to the periosteum

o Sinusitis

LARYNX o location: between the oropharynx and trachea o hollow organ

FUNCTIONS: 1. produce sound (VOICE BOX) 2. close airway during swallowing

o Bounded by o Thyroid and cricoid hyaline cartilages o EPIGLOTTIS – projects from the upper rim of the larynx, extends into the pharynx and has a lingual and

laryngeal surfaces. ANTERIOR SURFACE OF EPIGLOTTIS – covered with STRATIFIED SQUAMOUS EPITHELIUM LOWER LARYNGEAL TO TRACHEOBRONCHIAL TREE – CILIATED PSEUDOSTRATIFIED COLUMNAR

EPITHELIUM LAMINA PROPRIA – mixed mucous and serous gland can be found

o Laryngeal mucosal folds

o Vestibular folds (false vocal cords) o Upper pair o Duplication of mucosa

o Vocal folds (vocal cords) o Lower pair o No glands o Vocal ligament; vocalis muscle o covered with STRATIFIED SQUAMOUS EPITHELIUM

TRACHEA o Tubular air-conducting structure o Reinforced by 16-20 C-shaped hyaline cartilage rings o Surrounded by dense connective tissue o Smooth muscle fills gap between cartilaginous ends

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Tracheal Epithelium

o Ciliated, pseudostratified columnar epithelium with thick basal lamina o Numerous goblet cells o Various cell types

Ciliated Epithelium

Ciliated cells

o Microvillous border through which cilia project o Responsible for the movement of the mucus blanket

Goblet cells o Expanded apical region occupied by mucinoen granules o Main contributor to the viscous luminal fluid

Brush cells o Slender columnar cells with luminal border of microvilli o No secretory granules; unknown function

Serous cells o Apical granules; produce secretion of low viscosity

Basal cells o Small, pyramidal, between bases of columnar cells o Reserve stem cells

Bronchial Kulchitsky cells o Also basally situated with vesicles o Presumed to have neuroendocrine function

Migratory cells o Lymphocytes, globule leukocytes

LUNGS 1. BRONCHI

o PRIMARY BRONCHI – tracheal branches (left and right) o HILUM – opening in the surface of the lungs where primary bronchi enters

2 LOBAR BROCHI LEFT: 2 LOBES RIGHT: 3 LOBES

o (TERTIARY) SEGMENTAL BRONCHI BRONCHOPULMONARY SEGMENT

BRONCHIOLES o TERMINAL BRONCHIOLES (5 TO 7)

PRIMARY BRONCHI:

o Structure: similar to trachea up to hilus EXCEPT for the organization of the cartilage and smooth muscle o Then, cartilage rings replaced by plates of hyaline cartilage o Smooth muscles become prominent

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o Bronchial Epithelium o Ciliated columnar epithelium with goblet cells and submucous glands o Epithelial height gradually decreases

o Lamina propria o Separated from epithelium by thick basal lamina o Lymphocytes, mast cells, occasional eosinophils

2. BRONCHIOLES o 12th to 15th generation of branching o No cartilaginous plates o No glands in lamina propria o Discrete bundles of smooth muscles which influence luminal

diameter o No goblet cells o Epithelium consists of ciliated and nonciliated bronchiolar cells

that replace the mucous secreting cell o PNS- bronchiolar constriction o SNS- bronchiolar dilation, relax smooth muscle o CLARA CELL non ciliated bronchiolar cell

Columnar with rounded apex projecting above other cells Covered with microvilli Apical cytoplasm contains secretory granules Basal cytoplasm contains long mitochondria and cisternae of RER Protein-rich secretion Function still obscure

3. TERMINAL BRONCHIOLES o Branching of bronchiole which gives to 5 to 7 smaller branches. o Pseudostratified columnar in larger bronchi o gradually reduced in height to simple columnar epithelium o Further reduced in terminal bronchioles

to cuboidal epithelium ***RESPIRATORY PORTION OF THE LUNGS 1. RESPIRATORY BRONCHIOLES

o Very short tubes o Lined by cuboidal to low cuboidal,

nonciliated epithelium o Walls interrupted by alveoli

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o ALVEOLI saccular outpocketing of the wall lined by SQUAMOUS EPITHELIAL CELLs which are thin enough to permit gas exchange

o Gas exchange can take place o Number of alveoli increases with each branching o ALVEOLAR DUCT –

Numerous and closely spaced alveoli Distinguishable only by alignment of thickened interalveolar septal edges ATRIA/ atrium – small space where alveolar ducts terminate.

2. PULMONARY ALVEOLI

o Very thin-walled saccular compartments o where most gas exchange takes place o Rounded to polygonal

Septa: delineate boundary between alveoli o CT containing capillaries supported by collagenous and elastic fibers; covered by very thin alveolar

epithelium Alveolar Pores

o Pores of Kohn o Openings thru the alveolar septa o Communication prevents alveolar collapse despite

blockage of a small bronchus o Collateral respiration-ventilation of blocked respiratory

unit from unobstructed units through the pores *2 TYPES OF ALVEOLAR EPITHELIUM Squamous (Type I) Alveolar Cells

o Very thin o Occupy 95% of total alveolar space

Great (Type II) Alveolar Cells o Commonly located near angles between neighboring septa o Thicker than squamous o Rounded apical surface projecting above the level of epithelium o Free surface covered by short microvilli

Lamellar bodies o Dense ovoid membrane-bound granules with closely space, thin

lamellae o Becomes pulmonary surfactant when secreted through exocytosis

Pulmonary surfactant o Spreads over thin film of fluid coating the alveolar wall o Lowers surface tension o dipalmitoyl phosphatidylcholine

Interstitium of the Lung

Refer to the tissue between 2 layers of epithelium on the alveolar septa

Composed of capillaries, collagen and elastic fibers, septal cells (interstitial fibroblasts) mast cells, few lymphocytes

Septal Cells

Interstitial fibroblast

“myofibroblast”- contractile property during hypoxic conditions

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Production of extracellular matrix of alveolar septa 3. ALVEOLAR MACROPHAGE

o found in INTERALVEOLAR SEPTA o phagocytize dust particles and other particulates o Principal mononuclear phagocyte of the lungs o Monocyte that migrates out of the circulation and into the alveolar lumen o Directly exposed to dust or bacteria o Prominent filopodia and membrane-bound cytoplasmic inclusions

4. Pleura

Thin layer of CT lining the thoracic cavity

Parietal pleura o Layer applied on the thoracic wall

Visceral pleura o Layer apposed over the lung surface

5. Blood Supply of the Lungs

Pulmonary trunk pulmonary arteries alveolar capillaries venules pulmonary veins

Bronchial arteries from descending aorta

Numerous anastomoses between pulmonary and bronchial systems 6. Lymphatics of the Lung 2 main division

Pleura

Pulmonary parenchyma Both drain into hilar lymph nodes efferent trunks right lymphatic duct Innervation of the Lungs

Parasympathetic (vagal) and sympathetic innervation

Form plexus around hilus, then accompany bronchial and blood vessel ramifications

Influence bronchoconstriction and relaxation Small Granule Cells

Argyrophilic

May emit serotonin-like flourescence

Tall, broad-based, with narrow apex and short microvilli

Believed to be adapted to receive stimuli from the lumen with corresponding release of regulatory substances

Neuroepithelial Bodies

Cluster of similar cells with associated nerves

Resemble small granule cells

Speculated to function as chemoreceptors sensitive to oxygen concentration/hypoxia

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RESPIRATORY TRACT CROSS-SECTIONS review

LAYER Trachea

Mucosal lining Ciliated pseudostratified with goblet cells* L. propria Reticular CT, longitudinal elastic fibers at border M. rnucosae Absent, tracheal is muscle instead Submucosa Adipose CT, Bowman's glands (mixed serous/mucous secretion) Tunics Adventitia, shared w/ esophagus - carries carotid artery, jugular vein, nerves * Cell Types: Ciliated columnar cells Goblet cells Basal cells Brush cells = columnar cells with microvilli; may have sensory function Small Granule cells = similar to enteroendocrine cells

Primarv Bronchus Mucosal lining Ciliated pseudostratified w/ goblet L. propria Decrease in reticular and elastic fibers M. mucosae In circular configuration around bronchus Submucosa Dense irregular CT w/ mucus glands, hyaline cartilage present as overlapping plates Tunic Tunica serosa = CT + mesothelium Secondarv Bronchus Mucosal lining Ciliated pseudostratified with fewer goblet cells L. propria Decrease M. mucosae Decrease Submucosa Thinner, no glands, cartilage plates no longer overlap = "cartilage islands" Tunic Adventitia (shared w/ other parts of lung) Tertiarv Bronchus Mucosal lining PSC cells lower (almost simple cuboidal), no goblet cells L. propria Decrease M. mucosae Decrease Submucosa Decrease, cartilage plates smaller Bronchiole Mucosal lining Simple cuboidal, no goblet cells L. propria Decrease M. rnucosae Decrease Submucosa Decrease, no cartilage Respiratorv Bronchiole Mucosal lining Simple cuboidal becoming perforated simple squamous L. propria Decrease M. mucosae Decrease Submucosa Decrease to become continuous with adventitia Alveolar Duct Mucosal lining Simple squamous L. propria Very thin M. mucosae Sphincters present as duct opens into atrium

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RESPIRATORY review o Trachea

o PAS positive c-shaped cartilage ring o Pseudostratified ciliated columnar epithelium o goblet cells and a thick basement membrane o Seromucous glands, cartilage rings

o Bronchi o Pseudostratified ciliated columnar epithelium o Cartilage plates o Mucous glands and ducts

o Bronchiole o No cartilage o Continuous smooth muscle coat o Ciliated cuboidal epithelium o clara cells o No goblet cells

o Lung o Very thin alveolar walls o Bronchi with arteries