respiratory system anatomy

مبسم هللا الرحمن الرحي

DARWISH BADRAN

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Darwish H. Badran MD, PHD, FFDRCSI

Professor of Anatomical Sciences

Anatomy of the Respiratory System

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The Nose & Nasal Cavity

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Columella

PhiltrumDARWISH BADRAN

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Nasal Cavity Basic Structure

The Nares (nostrils):open into the nasal cavity at the vestibule.

The Choana: opens into the nasopharynx.

The Septum: extends medially from the roof to the floor. Cartilage + bone.

Conchae (turbinates): Project from the lateral wall into the cavity.

Meatus: a slit like space below the conchae.

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Floor of the Nasal Cavity

The hard palate, formed by:

• The palatine process of the maxilla and horizontal plate of palatine bone.

• Has the incisive foramen which transmits:

• Nasopalatine nerve.

• Sphenopalatine artery.

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Roof of the Nasal Cavity

Anterior (sloping): • Frontal and nasal bones

Middle (horizontal):

• Cribriform plate of the ethmoid.

Posterior (sloping):

• Body of he sphenoid

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Medial Wall of the Nasal Cavity

The nasal septum forms the medial wall.

It is commonly deviated to one side.

Parts:

• Anteriorly: Septal cartilage.

• Postero-inferior: Vomer bone.

• Postero-superior: Perpendicular plate of the ethmoid.

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Lateral Wall of the Nasal Cavity

The maxilla, antero-inferiorly

The perpendicular plate of the palatine bone posteriorly.

The three concha and meatuses below them.

Sphenoethmoidal recess above the superior concha.

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Nasal Mucosa….(1)

Olfactory:

• Covers the superior nasal concha and the upper 1/3 of the nasal septum.

• It appears yellowish in color.

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Nasal Mucosa….(2)

Conductive:

• Covers the lower part of the nasal cavity.

• Appears purple in color.

• Covered by skin in its lower part vestibule.

• Covered by respiratory epithelium in its upper part.

• The junction between the 2 epithelia _white line (mucocutaneous junction).

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Venous Drainage of the Nasal Cavity

Nasal veins tend to drain into the pterygoid plexus.

The submucous plexus modifies the physical properties of air.

Venous engorgement is associated with mucosal edema occlusion of the airway.

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Innervation of the Nasal Cavity

Antero-superior quadrant:

• Anterior ethmoidal nerve (nasociliary).

Antero-inferior quadrant:

• Anterior superior alveolar nerve (maxillary).

Postero-superior quadrant:

• Sphenopalatine nerve and nasal branches of the sphenopalatineganglion.

Postero-inferior quadrant:

• Greater palatine nerve.

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Innervation of the Nasal Septum

Olfactory nerve.

Anterior ethmoidal nerve.

Sphenopalatine nerve.

Posterior superior alveolar nerve.

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Epistaxis and Little’s Area

Epistaxis: bleeding from the nose.

Commonly occurs from Little’s area:

• Lies in the anterior part of the nasal septum, 2.5 cm from the nares, opposite the vestibule.

• It is the site of anastomosis of:

• Sphenopalatine artery.

• Greater palatine artery.

• Septal branches of the facial.

Arteries in the area form together Kieselbach’s plexus.

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Blood Supply of the Nasal Cavity

anterosuperior quadrant

Anterior and posterior ethmoidal

posterosuperiorquadrant

Sphenopalatine artery

anteroinferior quadrant & nasal septum

Superior labial of facial

Posteroinferior quadrant

Greater palatine artery

Supplied in quadrants

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Vessels and Nerves of the Nasal Septum

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Paranasal Sinuses

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At birth, all sinuses are rudimentary

EXCEPT the frontal sinus (by 2nd

year).

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Functions of the paranasal sinuses

Sinuses lighten the facial skeleton?!!.

Sinuses produce resonance of the voice.

They may act as insulators.

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All sinuses are lined with respiratory epithelium.

Gravity plays no role in emptying a normal sinus.

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Sinuses undergo two phases of rapid

enlargement; one at 6-7 years and another phase after puberty.

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Maxillary Sinus

The largest sinus, occupies the body of the maxilla its average volume is ~15ml.

Pyramidal in shape with the base directed towards the nose.

The ostium lies in the upper part of the base of the sinus.

It drains into the hiatus semilunaris of the middle meatus.

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Relations of the Maxillary Sinus

Superiorly: the floor of the orbit.

Inferiorly: 2nd premolar and 1st molar teeth.

Anteriorly: the cheek.

Posteriorly: pterygopalatine fossa.

Medially: nasal cavity.

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Innervation of the Maxillary Sinus

Anterior superior alveolar nerve: supplies the pulp of the canine and incisors, and the antero-inferior quadrant of the lateral nasal wall.

Middle superior alveolar nerve: supplies the premolar teeth and the overlying antral mucosa.

Posterior superior alveolar nerve: supplies the molars and gives tiny branches to the mucosa.

Greater palatine nerve: minute branches to supply the posterior part of the medial wall of the sinus.

Infra-orbital nerve: supplies the roof of the antrum.

Remember: the infraorbital nerve is related to the roof of the sinus.

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Relation of the Teeth to the Maxillary Sinus

Maxillary canine raises a ridge on the facial surface of the wall of the maxilla but not on the wall of the sinus.

The posterior 5 teeth lie below the floor of the sinus.

The roots of the 1st molar and the 2nd premolar lie nearest to the to the curve of the base of the sinus.

Improper extraction or implantation may lead to antro-oral fistula particularly in old age.

Maxillary teeth and the mucosa of the maxillary sinus are innervated by the superior alveolar nerve.

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The sinus is lined with mucoperiosteum, with cilia that beat toward the ostia.

This membrane is also referred to as the "SchneiderianMembrane", which is histologically a bilaminar membrane with ciliated columnar epithelial cells on the internal (or cavernous) side and periosteum on the osseous side.

a genuine osteogenic potential is associated with the membrane and can contribute to development of successful sinus augmentation techniques

Schneiderian Membrane

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Other

Paranasal Sinuses

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Frontal Air Sinuses

The right and left sinuses are unequal and separated by a septum which is commonly resorbed in old age.

The ostium is present at the lower medial corner.

Drains into the middle meatus.

Innervated by the supraorbital and supratrochlearnerves.

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Ethmoidal Air Cells

Arranged in groups (anterior, middle and posterior).

Each sinus contains 3-20 air cells, separated by a thin incomplete bony septa.

Innervated by anterior and posterior ethmoidal nerves and branches from the pterygopalatine ganglion.

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The Ethmoidal Air Cells

The anterior drain into the middle meatus in the hiatus semilunaris.

The middle drain on or above the bulla ethmoidale.

The posterior drain into the superior meatus.

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Sphenoid Air Sinus

Present in the body of the sphenoid.

Innervated by the posterior ethmoidal nerve and the orbital branch of the sphenopalatine ganglion.

Relations: ?????

It drains into the spheno-ethmoidal recess.

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The nasolacrimal

duct drains into

the inferior meatus.

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Nasal Meatuses

Sphenoethmoidal recess Sphenoid sinus.

Superior meatus Posterior ethmoidal sinus.

Middle meatus _ Frontal, maxillary, anterior and middle ethmoidal sinuses.

Inferior meatus _ Nasolacrimal duct.

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The Pharynx

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It is a musculo-fascial tube incomplete anteriorly.

Extends from the base of the skull to the level of C6; it continues as the esophagus.

Runs in front of the vertebral column and behind the nose, mouth and larynx

Its diameter decreases from 3.5 cm to 1.5 cm.

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Lies behind the nose and soft palate.

Its posteromedial wall is formed by the anterior arch of the atlas and sphenoid bone.

It is an airway only.

Contains:

• Naopharyngeal tonsil

• Opening of Eustachian tube.

• Tubal tonsil

• Salpingopharyngeal fold

• Pharyngeal recess

Nasopharynx

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Lies behind mouth.

Extends between the soft palate and the upper of the epiglottis

Lies in front of the bodies of C2 & C3

Contains:

• Palatine tonsil

Oropharynx

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Lies in front of the bodies of C3 – C6.

Extends from the epiglottis to the lower border of C6.

Contains:

• Piriform fossa on each side

Laryngopharynx

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Superior constrictor:

• Origin: medial pterygoid plate and hamulus, and the pterygomandibularraphe

• Insertion: pharyngeal raphe

Muscles of the Pharynx

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Middle constrictor:

• Origin: grater and lesser horns of the hyoid bone, and the stylohyoid ligament

• Insertion: pharyngeal raphe


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Inferior constrictor:

• Parts:

• Thyropharyngeus: from the side of the laryngeal cartilage to the pharyngeal raphe.

• Cricopharyngeus: from the arch of the cricoid cartilage; muscles from both sides merge together.


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Stylopharyngeus: from the styloid procaess to the thyroid cartilage.

Palatopharyngeus: from palatal aponeurosis to the pharynx.

Salpingopharyngeus: the cartilaginous part of Eustacheantube to the posterior border of thyroid lamina.


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Homework:

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What (is) are the gap(s) in the lateral pharyngeal wall? What (is) are the structure(s) passing through each of them?

Name the arteries supplying the pharynx.

What are the components of the pharyngeal plexus?

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The Larynx

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An airway extending from the root of the tongue to the lower border of cricoid cartilage.

Formed of cartilages and ligaments.

Lined by a mucous membrane.

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Single:

• Thyroid

• Cricoid

• epiglottis

Paired:

• Arytenoid

• Cuniform

• Corniculate

Cartilages:

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Name the intrinsic laryngeal muscles.

Mention the function(s) of each of them.

Name the nerve supply of each of them.

Name the abductor(s) and adductor(s) of the vocal cord.

Laryngeal muscles

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The vestibular folds are covered by respiratory epithelium.

The vocal cords are covered by stratified squamous non-keratinized epithelium.

Trachea

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Trachea: Landmarks

Begins at lower border of cricoid cartilage / C6

Extends to Carina

• Right of the midline

• Sternal angle

• T4 on inspiration / T6 on expiration

15 cm long / 2cm in diameter

15 – 20 incomplete rings of cartilage

• Bridged posteriorly by trachealis muscle

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TRACHEA

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Trachea

Variable shape

• Usually round, oval, oval with flattened posterior border

• Square

• Inverted pear

• Horseshoe

Very pliable in children

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Trachea: Carina

Lies at T5 level

• T4 on expiration

• T6 on inspiration

Normal angle: 55°-65°

• 20° to right of midline

• 40° to left of midline

Angle slightly larger and symmetrical in children

Angle increases by 10° - 15°in recumbency

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Relations: Cervical

Anterior:

• Isthmus anterior to 2nd, 3rd, 4th rings

• Inferior thyroid veins

• Strap muscles: Sternohyoid, Sternothyroid

Posterior:

• Oesophagus, recurrent laryngeal nerves

Lateral:

• Lobes of thyroid

• Common carotid artery

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Relations: Thoracic

Anterior:

• Brachiocephalic a.

• Left common carotid a.

• Left brachiocephalic v.

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Relations: Thoracic

Posterior:

• Oesophagus

• Left recurrent laryngeal n.

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Relations: Thoracic

Left lateral:

• Arch of the aorta

• Left common carotid a.

• Left subclavian a.

Right lateral:

• Right vagus nerve

• Arch of the azygos vein

• PleuraDARWISH BADRAN

Blood supply

Upper part

• Inferior thyroid artery

Lower part

• Branches of the bronchial artery

Venous drainage

• Inferior thyroid venous plexus

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Pleura & Lungs

Surface Anatomy of the Pleura

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4

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Apex (of each lung): lies one inch above the medial 1/3 of the clavicle.

Right pleura:

• The anterior margin extends vertically from sternoclavicular joint to 6th costal cartilage.

• Inferior margin : passes round chest wall, on the 8th rib in midclavicular line, 10th rib in mid-axillary line and finally reaching to the last thoracic spine.

• Posterior margin : along the vertebral column from the apex to the inferior margin.

Left pleura:

• The anterior margin extends from sternoclavicular joint to the level of 4th costal cartilage, then deviates for about 1 inch to left at 6th costal cartilage to form cardiac notch.

Surface Anatomy of the Pleura

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Apex, anterior border and posterior border correspond nearly to the lines of pleura but are slightly away from the median plane.

Inferior margin:

• as the pleura but more horizontal and finally reaching to the 10th thoracic spine.

Oblique fissure:

• represented by a line extending from 3rd

thoracic spine, obliquely ending at 6th

costal cartilage.

Transverse fissure only in right lung: represented by a line extending from 4th right costal cartilage to meet the oblique fissure.

Surface Anatomy of the Lungs

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It is a closed serous sac which surrounds the lung and invaginated from its medial side by the root of lung.

It has 2 – layers:

• parietal pleura which lines the thoracic cavity.

• visceral pleura which surrounds the lung, separated by a pleural cavity.

Pleural cavity:

• Contains 5-10 ml. of serous fluid which lubricates both surfaces and allows the lungs to move free during respiration.

The Pleura

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1- Cervical pleura: It is part of parietal pleura which protrudes up into the root of the neck.

2-Costal pleura: It lines inner surface of ribs, costal cartilages, intercostal muscles and back of the sternum. Innervated by intercostal nerves.

3-Diaphragmatic pleura: It covers upper surface of the diaphragm. Innervated medially by the phrenic nerve, and peripherally by the lower 6 intercostal nerves.

4-Mediastinal pleura: It covers mediastinal surface of the lung. Innervated by the phrenic nerve.

Parts of Parietal Pleura

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Firmly covers outer surfaces of the lung and extends into its fissures.

The 2- layers (mediastinal parietal pleura & visceral pleura) are continuous with each other to form a tubular sheath (pleural cuff) that surrounding root of lung (vessels, nerves & bronchi) in the hilum of the lung.

On the lower surface of root of the lung, pleural cuff hangs down as a fold called pulmonary ligament.

Innervated by sympathetic fibres from pulmonary plexus.

Visceral Pleura

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Anterior border : is sharp, thin and overlaps the heart.

Anterior border of left lung presents a cardiac notch at its lower end + thin projection called the lingula below the cardiac notch.

Posterior border : is rounded, thick and lies beside the vertebral column

Lungs .. General ..1/3

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The lung is conical in shape.

• It has an apex, a base and 2 surfaces.

• The costal surface of each lung borders the ribs (front and back).

• On the medial (mediastinal) surface, the bronchi, blood vessels, and lymphatic vessels enter the lung at the hilum.

Apex: projects into root of the neck(one inch above the medial 1/3 of the clavicle) and it is covered by cervical pleura.

Base: (inferior= diaphragmatic surface) is concave and rests on the diaphragm.


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Costal surface:

• Convex.

• Covered by costal pleura which separates lung from: ribs, costal cartilages & intercostal muscles.

Medial surface: It is divided into 2 parts:

• Anterior (mediastinal) part:

• Contains a hilum in the middle (it is a depression in which bronchi, vessels, & nerves forming the root of lung).

• Posterior (vertebral) part:

• It is related to: bodies of thoracic vertebrae, intervertebral discs, posterior intercostal vessels & sympathetic trunk.


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Larger & shorter than left lung.

Divided by 2 fissures(oblique & horizontal) into 3 lobes (upper, middle and lower lobes).

Right Lung

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Azygos vein and its arch (posterior and over the root of the lung).

Vagus nerve posterior to the root.

Esophagus above and posterior to the root.

Phrenic nerve anterior to the root.

Cardiac impression: related to right atrium.

Below hilum and in front of pulmonary ligament: Groove for I.V.C.

Mediastinal Surface of the Right Lung

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2 bronchi lie posterior.

Pulmonary artery is superior

2 Pulmonary veins are inferior and anterior.

Root of the Right Lung

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Divided by one oblique fissure into -2 lobes, Upper and lower.

There is No horizontal fissure.

It has a cardiac notch at lower part of its anterior border.

Left Lung

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Descending aorta posterior to the root.

Arch of the aorta above the root.

Vagus nerve posterior to the root.

Groove for left common carotid artery.

Groove for left subclavian artery.

Phrenic nerve anterior to the root.

Cardiac impression : related to left ventricle.

Mediastinal Surface of the Left Lung

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One bronchus lies posterior

Pulmonary artery is superior

2 Pulmonary veins are inferior and anterior.

Root of the Left Lung

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Bronchial arteries (branches of descending thoracic aorta)….. supply oxygenated blood to bronchi , lung tissue & visceral pleura.

Bronchial veins: drain into azygos & hemiazygos veins.

Pulmonary artery carries non-oxygenated blood from right ventricle to the lung alveoli.

2 pulmonary veins from each lung : carry oxygenated blood to the left atrium.

Blood Supply of the Lungs

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Pulmonary plexus :at the root of lung. It s formed of sympathetic & parasympathetic fibres.

• 1- Sympathetic: from sympathetic trunk they are broncho-dilators and vasoconstrictors.

• 2- Parasympathetic: from the Vagus nerve. They are broncho-constrictors and secretomotor to bronchial glands and vasodilators.

Nerve Supply of the Lung

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There are 2 lymphatic plexuses

• Superficial plexus (subpleural): lies under the visceral pleura and drains to bronchopulmonary nodes in the hilum of lung.

• Deep plexus:

• Lies along the bronchial tree & pulmonary blood vessels and drain into the pulmonary nodes within the lung substance. Then into bronchopulmonary nodes in the hilum of lung. Then into the tracheo-bronchial nodes at the bifurcation of trachea, and finallyinto broncho-mediastinal lymph trunks to end in thoracic duct (left) or in right lymphatic duct (right).

Lymph Drainage of the Lung

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The trachea divides into 2 main bronchi:

• Right main bronchus: divides before entering the hilum, it gives off superior lobar (secondary) bronchus. On entering hilum, it divides into middle & inferior lobar bronchi.

• Left main bronchus: it divides after entering the lung into superior & inferior lobar bronchi.

Within the lung each bronchus divides into number of branches.

Bronchi

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They are the anatomic, functional, and surgical units of the lungs.

Each lobar (secondary) bronchus gives off segmental (tertiary) bronchi.

Each segmental bronchus divides repeatedly into bronchioles.

Bronchioles divide into terminal bronchioles, which show delicate outpouchings ‘the respiratory bronchioles’.

Bronchopulmonary Segments

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The respiratory bronchioles end by branching into alveolar ducts, which lead into alveolar sacs.

The alveolar sacs consist of several alveoli, each alveolus is surrounded by a network of blood capillaries for gas exchange.


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It is pyramidal in shaped, its apex lies toward the root, while its base lies on the lung surface.

It is surrounded by connective tissue septa.

It has a segmental bronchus, a segmental artery, lymph vessels, and autonomic nerves.

The segmental vein lies in the inter-segmental C.T. septa between the segments.

A diseased segment can be removed surgically, because it is a structural unit..


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HISTOLOGY OF THE CONDUCTING SYSTEM

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Upper Respiratory

Tract

Lower Respiratory

Tract

Nasal Conchae

The Nose

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A. THE NOSE -- a hollow organ, covered with skin, provided with muscles, supported by cartilage and bone and lined with a mucous membrane (mucoperiosteum).

B. THE NASAL CAVITIES --(separated by the nasal septum):

1. The vestibule -- opens to the outside at the anterior nares. The skin continues into the vestibule; Changes from epidermis of thin skin to pseudostratified, ciliated, columnar epithelium in the rest of the nasal cavity. The junction between the skin and the mucous membrane is known as the white line; it has relatively low blood supply.

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2. The respiratory region -- includes nearly all of the septum and lateral walls. The surface area of the lateral walls is increased by shelf-like projections (supported by bone) called conchae or turbinates.

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a. Epithelium: pseudostratified, ciliated columnar with goblet cells; Cilia beat backwards, toward the pharynx; Goblet cells sometimes are concentrated in intraepithelial pits; The basement membrane varies from thin to very thick.

b. Lamina propria: of loose connective tissue; it contains: mixed sero-mucous glands (comp. tubuloalveolar) and a rich cavernous venous plexus, which serves to warm the passing air; upon irritation the plexus can be distended by blood and reduces air flow; it is described as erectile tissue.

c. Submucosa: absent, the deepest layer of the lamina propria fuses with the periosteum below;

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The olfactory region -- located on the superior concha and adjacent septum (dime-size areas).

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Olfactory Epithelium

1) Olfactory cells: spindle shaped, with round nuclei; (Nuclei are in the middle and deep zone of the epithelium.) the apical part extends to the epithelial surface, ends in a bulbous knob which bears 6-8 olfactory hairs; these hairs or cilia are non-motile, sensory and serve as dendrons; they are embedded in a thick layer of mucus and parallel the surface of the olfactory epithelium. The proximal (basal) part of the cells form a long thin axonal process, which constitute the olfactory nerve fibers; these unmyelinated fibers are

connected to the olfactory center of the brain (in the olfactory bulbs). Olfactory cells are modified bipolar neurons.

Functions: the olfactory cilia are stimulated by gaseous, odori-ferous substances dissolved in the secretion of serous glands moistening the epithelium.

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SEM of the surface of the Olfactory Epithelium

2) Supporting cells: tall slender cells make up the upper third of the pseudostratified epithelium (nuclei in top 2-3 rows). They are attached to the sensory (olf.) cells at the surface of the epithelium by zonulaadherens (junctionalcomplex with terminal web). Have a small Golgi complex in the apical cytoplasm and pigment granules (brown). There are numerous slender villi on their apical surface.

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3) Basal cells:constitute a single layer of conical elements a the base of supporting cells (bottom layer of nuclei); have dark nuclei and branching processes.

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Lamina propria: continuous with the dense connective tissue of the underlying periosteum in the adult or with the perichondrium in the fetus. The venous plexus in the lamina propria is continuous with that of the respiratory regions.

A group of branched, tubuloalveolar (mainly serous) olfactory glands called Bowman's glands present in the lamina propria supply the necessary solvents to trap odoriferous substances. The continuous replacement of secretion keeps the receptors ready for new stimuli.

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Bronchiolar Epithelium

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Thin walled tube 10 cm long

Bifurcates into 2 primary bronchi

Respiratory mucosa

C-shaped hyaline cartilage rings with open ends connected by elastic ligament and smooth muscle (Trachealis); contraction occurs in coughing to increase velocity of air

TRACHEA

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Trachealis

Bronchial Tree

2 primary bronchi enter lungs

3 intrapulmonary bronchi on right and 2 on the left

Bronchioles

Terminal bronchioles

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> 5 mm diameter

Mucosa and submucosa like trachea

Smooth muscle, elastic fibers, and serous/mucous glands in lamina propria

Lymphoid nodules may be present in lamina propria

Hyaline cartilage present in interrupted plates.

BRONCHI

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Respiratory Epithelium

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Pseudostratified columnar epithelium ciliated with goblet cells.

Lies on relatively thick basement membrane.

Contains 5-6 types of cells:

1) Goblet 2) Ciliated columnar 3) Basal

4) Brush 5) Serous?? 6) DNES

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1) Goblet cells

Form 30% of total cells.

Secrete mucinogen which becomes mucin on hydration. They can absorb water in < 20ms.

The part containing secretory granules is known as the theca.

The basal part is called the stem.

Cytoplasm contains: rER, Golgi, ribosomes, mitochondria.

Apical plasmalemma shows microvilli.

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Stem

Theca

2) Ciliated columnar cells

Form ~35% of total cells.

Have basally located nucleus.

Posses cilia and microvilli.

Apical cytoplasm is rich in mitochondria and Golgi apparatus.

Basal cytoplasm is rich in rER.

They move the mucus upwards

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3) Basal (Stem) cells


Considered as stem cells.

Relatively short, with large round-oval nucleus

Might replace goblet, columnar and brush cells.

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4) Brush cells


Columnar cells with microvilli.

Unknown function.

Cytoplasm contains small mucus granules.

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5) DNES

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Form 3-4% of total cells.

Basal cytoplasm contains several granules.

Granular content usually released into nearby connective tissue.

They secrete substances that control the functions of other cells.

It is believed that their processes into the lumen monitor the O2 & CO2 levels in the lumen.

Can be seen in immuno-stained sections only

Dome-shaped cells with microvilli.

Apical cytoplasm contains granules and many rER.

Their secretion protects bronchiolar epithelium.

They detoxify certain toxins in the sER.

They secrete surfactant like substance.

They divide to replace degenerated bronchiolar epithelium.

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Clara cells

They start to appear from the carina, and increase in number distally.

Pneumocytes type I

Simple squamous epithelial cells with tapering ends forming 90% of alveolar surface.

Has a well developed basal lamina.

Nucleus seen in the widest arts of the cell surrounded by organelles.

Form occluding junctions with each other and with type II.

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Pneumocytes type II

More numerous than type I but occupy less surface area.

They are cuboidal cells located in the interalveolar septum (septal cells).

Have apical microvilli, central nucleus, rER,Golgi, and mitochondria.

Lamellar bodies are frequent and secrete the surfactant.

These cells replace degenerated type I cells.

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AlveolrarMacrophages

Originate from blood monocytes.

Enter the alveolar lumen between alveolar cells.

They maintain sterile environment by phaocytosing foreign bodies.

They assist in uptake of surfactant.

They migrate to bronchi and they either return to alveoli or become swallowed or expectorated.

They may migrate into lymph vessels.

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Terminal Bronchioles

The smallest and the most distal of the conducting system.

Less than 0.5 mm in diameter.

Epithelium is composed of Clara cells and cuboidal ciliated cells.

Lamina propria is composed is composed of fibroelastic connective tissue surrounded by 1-2 layers of smooth muscles.

NO goblet cells, NO cartilage, No glands in the lamina propria.

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Respiratory Bronchioles

The first region for gaseous exchange.

Their wall is interrupted by alveoli. Transition between conducting and respiratory tissues

Ciliated cuboidal epithelium with Clara cells changes to type 1 alveolar cells

Smooth muscle and elastic fibers underlie epithelium (parasympathetic stimulation: bronchial constriction; sympathetic stimulation: bronchial dilation)

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Alveolar Ducts

There is no wall, but alveoli arranged in one line.

Each alveolar duct branches and ends in an alveolar sac.

The beginning of the alveolar sac is known as atrium.

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Alveoli

The primary histological and functional units of the respiratory system.

Total number of alveoli is ~ 300 million covering ~ 150 m2.

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The interalveolar septum

occupies the region between two adjacent alveoli.

Each (face) is lined by alveolar epithelium.

Its thickness is extremely variable.

It contains continuous capillaries, collagen type III, elastic fibres, fibroblasts, mast cells, and lymphocytes.

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The Blood-Air Barrier (BAB)

It is the region where the interalveolar septum septumistraversed by respiratory gases.

It is composed of:

• Surfactant

• Type I pneumocytes

• Fused basal lamina

• Endothelium.

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Eman Rababaah

Practical

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Lamina Propria

Goblet Cells

Basal Lamina

Goblet cell

Stem Cell

Seromucous gland

Vein

Duct

Glands

Hyaline cartilage

Smooth muscles

Seromucous glands

Hyaline cartilage

Terminal Bronchiole Smooth Muscles

Pulmonary vein

Cartilage

Lung tissue

Smooth muscles

Pulmonary artery

Glands

Terminal Bronchiole

Respiratory Bronchiole

Alveolar Duct

Alveolar Sac

Alveolus

Pleura

Bronchus

Bronchiole

Pulmonary artery

Bronchial artery

Pulmonary

vessel

Bronchiole

Alveolar type I

Alveolar type II

respiratory system anatomy

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