BY Dr Pradeep Kumar Karem

MODERATOR-Dr VENUGOPAL MD

PROFESSOR OF ANAESTHESIOLOGY

REGIONAL ENT HOSPITAL

Structure and anatomy of

respiratory system

Respiratory organs Upper respiratory tract

Nose, nasal cavity, and paranasal sinuses

Pharynx and larynx

Lower respiratory tract Trachea

Bronchi and smaller bronchioles

Lungs and alveoli

Functional Anatomy of the Respiratory System

Basic Anatomy of the Upper Respiratory Tract

Provides an airway for respiration

Moistens and warms air

Filters inhaled air

Resonating chamber for speech

Houses olfactory receptors

Nose

External nares – nostrilsNasal cavity divided by – nasal septumPosterior nasal apertures-choanae

continous with nasopharynx–

NOSE

Superior and middle nasal conchae Part of the ethmoid bone

Inferior nasal conchaeSeparate bone

Project medially from the lateral wall of the nasal cavity

Create streamline flow of air and provide larger surface area for humidification of air

Nasal Conchae

Two types of mucous membrane

Olfactory mucosa Near roof of nasal cavity Houses olfactory (smell) receptors

Respiratory mucosa Lines nasal cavity Epithelium is pseudostratified ciliated columnar

Nose

The Paranasal SinusesMay provide air

condition to inspired air by supplying warm and humid air.

May reduce weight of the skull or simply act as protector to to eyes in trauma.

May thermally insulate skull base and orbit.

Through out respiratory tract cilia are present which prevent the accumulation of secretions.

In nose the flow f cilia is swept towards the pharynx,..

In the bronchial tree the flow is swept towards the entrance of larynx.

o Factors affecting ciliary activity• All volatile general anaesthetics depress the

propelling action of cilia.• They also decrease the secretions and there by

reduces ciliary activity.• Opiates has direct depressant action over the

cilia while atropine weakens the ciliary activity by altering the viscosity of the mucous.

Ciliary activity

Funnel-shaped passageway

Connects nasal cavity and mouth

Divided into three sections by locationNasopharynxOropharynxLaryngopharynx

The Pharynx

Only an air passagewayClosed off during swallowingPharyngeal tonsil (adenoids)

Located on posterior wallDestroys entering pathogens

Contains the opening to the pharyngotympanic tube (auditory tube)• Tubal tonsil

Provides some protection from infection

The Nasopharynx

Arch-like entranceway – faucesExtends from soft palate to the epiglottis

EpitheliumStratified squamous epithelium

Two types of tonsils in the oropharynxPalatine tonsils – in the lateral walls of the

fauces Lingual tonsils – covers the posterior surface

of the tongue

The Oropharynx

Passageway for both food and air.

EpitheliumStratified squamous epithelium

Continuous anteriorly with the larynx and posteriorly with esophagus.

The Laryngopharynx

Three functionsVoice production

Provides an open airway

Routes air and food into the proper channelsSuperior opening is

Closed during swallowing Open during breathing

The larynx

Larynx is formed by Nine CartilagesThyroid cartilage

Shield-shaped, forms laryngeal prominence (Adam’s apple)

Three pairs of small cartilagesArytenoid cartilagesCorniculate cartilagesCuneiform cartilages

Epiglottis

Cricoid cartilage

The Larynx

Vocal ligaments of the larynx

Vocal folds (true vocal cords) Act in sound production

Vestibular folds (false vocal cords) No role in sound production

Epithelium of the larynxStratified squamous – superior portion

Pseudostratified ciliated columnar – inferior portion

The Larynx

Anatomy of larynx

Movements of vocal cords

Superior laryngeal nerve• Supplies cricothyroid muscle .

• Sensory supply to larynx above vocal cords

Recurrent laryngeal nerve• Supplies all intrinsic muscles except

cricothyroid.

• Sensory supply to larynx below vocal cords.

Nerve supply of larynx

Unilateral superior laryngeal nerve palsy.

Unilateral recurrent laryngeal nerve palsy.

Bilateral recurrent laryngeal nerve palsy.

Unilateral recurrent and superior laryngeal nerve palsy.

Bilateral recurrent and superior laryngeal nerve palsy.

Vocal cord palsies

Loss of sensation of supraglottic larynx Frequent throat clearing, paroxysmal cough Vocal fatigue and vague foreign body sensation

Loss of motor function of cricothyroid muscle Slight voice change and diplophonia

Signs Normal vocal cord position during quiet

respiration Deviation of posterior commissure to paralysed

side Shortened vocal cord on paralysed side.

Unilateral superior laryngeal nerve injury

Loss of sensory supply below vocal cords

Loss of abduction with intact adduction by cricothyroid Voice is breathy but compensation occurs

Signs Vocal cord assumes paramedian position Airway is adequate but may be compromised

with exertion

Unilateral recurrent laryngeal nerve injury

Loss of abductors of both sides except for cricothyroid muscle.

Vocal cords are in paramedian positionVoice is fairNo aspirationDegree of airway compromise may range

from mild to severe stridor and dysnoea.May develop gradually or suddenly leading to

emergency.

Bilateral recurrent laryngeal nerve injury

Both vocal cords remain in intermediate position(because of absence of cricothyroid adduction)

Very breathy voice

Possible risk of aspiration

Unilateral recurrent and superior laryngeal nerve injury

Both vocal cords are in intermediate position, flaccid and motionless.

Apnoea and high risk of aspiration.

Bilateral recurrent and superior laryngeal nerve injury

Is a tube which descends into the mediastinum.

It is kept open by C-shaped cartilage rings which are incomplete posteriorly.

The Trachea

It is 10-11cm in length extending from lower part of larynx.

It starts at the level of 6th cervical vertebra and ends near carina where it divides into left and right main bronchus.

Carina correspondes to the level of 5th thoracic vertebra

The trachea moves up with respiration and with alterations with the position of the head.

In deep inspiration the carina can descend as much as 2.5cm.

The Trachea

Extension of the head and neck for maintaining an airway in anaesthetised patients increases the length of the trachea by 23 to 30 %.

If the patient is intubated with flexion at the atlanto-occipital joint, the ET tube reaching just beyond the vocal cords, with subsequent hyperextension of the head the tube may be withdrawn into pharynx.

The Trachea

The trachea divides at the carina into right and left main bronchus.

The bronchi divide dichotomously into several million terminal bronchioles to terminate in one or more respiratory bronchioles.

Bronchioles are less than 1mm in diameter, they do not have cartilage in their walls.

Smooth muscles are found in the walls of the airways upto the level of alveolar ducts.

Bronchi and bronchioles

RIGHT MAIN BRONCHUS• It is 2.5cm long and is wider and shorter

than the left bronchus.• In children under the age of 3yrs the

angulation of two main bronchus at carina are equal on both sides.

• In adults the right main bronchus is angulated at 25˚and the left main bronchus is angulated at 45˚from midline.

• As the right bronchus is nearly vertical there is much tendency for the ETtubes and suction catheters to enter the lumen.

BRONCHI

Right main bronchus is also the commonest site for aspiration .

The right main bronchus divides into three lobar bronchus to supply respective lobes.

If a patient in right lateral position aspirates, the material gravitates into lateral portion of posterior segment of upper lobe.

If pt is in supine and aspirates the material gravitates to apical segment of lower lobe.

LEFT MAIN BRONCHUS• It is narrower than the right bronchus and is

nearly 5cm long.

• The left main bronchus divides into two lobar bronchi for upper and middle lobes.

• As the left bronchus is 5cm long without any branching it is particularly suitable for intubation and blocking during thoracic surgery.

The cartilagenous rings that are seen in bronchioles are replaced by cartilagenous plates as the size of bronchioles decrease.

The cartilage completely disappear when their size reaches to 0.6mm

The small terminal bronchioles as supported by smooth muscle cells.

Distal to each terminal bronchiole is an acinus, which consists of three to four orders of respiratory bronchioles.

Respiratory bronchioles lead to alveolar ducts. The walls of these ducts consist of alveolar sacs or the mouths of alveoli..

Bronchioles

Terminal bronchiole

Alveoli and the Respiratory Membrane

ALVEOLIRespiratory zone starts at respiratory

bronciole which consists mainly millions of alveoli.

Alveoli consist ofType I cells and basal laminae

Scattered among type I cellsCuboidal epithelial cells – type II cells

Secrete surfactantSurfactant is a mixture of

phospholipids(dipalmitoyl-phosphatidyl-choline)

Surfactant is secreted by type 2 pnuemocytes and it protects alveoli from collapse during expiration.

Structures of the Respiratory Zone

Features of alveoliSurrounded by elastic fibers.Interconnect by way of alveolar poresInternal surfaces

A site for free movement of alveolar macrophages.

Absence of surfactant at birth causes respiratory distress syndrome.

Oxygen therapy also lead to reduction of the surfactant and hence it should be used in lower most possible concentration.

Alveoli

ALVEOLAR CAPILLARY PLEXUS

Partial pressures at various sites

A double-layered sac surrounding each lungParietal pleura

Visceral pleura

Pleural cavity Potential space between the visceral and

parietal pleurae

Pleurae help divide the thoracic cavity Central mediastinum Two lateral pleural compartments

The Pleurae

Diagram of the Pleurae and Pleural cavities

Major landmarks of the lungsApex, base, hilum, and root

Left lungOblique fissure divides it to

• Superior and inferior lobes

Right lungOblque and horizontal fissure divides it to

• Superior, middle, and inferior lobes

Gross Anatomy of the Lungs

LungsEach is cone-

shaped with anterior, lateral and posterior surfaces contacting ribs

Superior tip is apex, just deep to clavicle

Concave inferior surface resting on diaphragm is the base

Hilus or (hilum)Indentation on mediastinal (medial) surfacePlace where blood vessels, bronchi, lymph vessel, and nerves enter and exit the lung“Root” of the lungAbove structures attaching lung to mediastinumMain ones: pulmonary artery and veins and main bronchus

Each lobe is made up of bronchopulmonary segments separated by dense connective tissueEach segment receives air from an individual

segmental (tertiary) bronchusApproximately 10 bronchopulmonary segments in each

lungLimit spread of infectionCan be removed more easily because only small

vessels span segmentsSmallest subdivision seen with the naked eye is

the lobuleHexagonal on surface, size of pencil eraserServed by large bronchiole and its branchesBlack carbon is visible on connective tissue separating

individual lobules in smokers and city dwellers

Bronchopulmonary Segments

Bronchopulmonary segments consists of segmental bronchus, its branches and associated arteries,.

They occupy a central position in each segment.Many tributaries of the pulmonary veins run

between segments, serving adjacent segments which drain into more than one vein.

Thus a bronchopulmonary segment is not a complete vascular unit with an individual bronchus, artery and vein.

During resection of segments it is obvious that the planes between them are not avascular but are crossed by pulmonary veins and sometimes by branches of arteries.

Bronchopulmonary Segments

The lungs have two functionally distinct circulatory pathways.

These are the pulmonary vessels, which convey deoxygenated blood to the alveolar walls and drain oxygenated blood back to the left side of the heart.

The much smaller bronchial vessels, which are derived from the systemic circulation and provide oxygenated blood to lung tissues which do not have close access to atmospheric oxygen.

Blood Supply

The lungs are innervated by vagal and sympathetic fibres.

The vagal fibres supply the bronchial muscles and glands and are bronchoconstrictor and secretomotor.

The efferent sympathetic fibres are inhibitory. They relax the bronchial smooth muscle and also have vasoconstrictor effects.

Innervation of the Lungs

Spasm occures mainly on the bronchioles.It is most commonly encountered in patients with

irritable bronchial tree i.e, in chronic bronchitis patients and asthmatics.

Stimulation can be due to chemical, mechanical and neurogenic factors.

Constriction of the bronchiole occurs mostly in expiration than in inspiration.

Diagnosis of bronchospasm should be made only when all other ventilatory causes has been excluded.

Should be treated in the same way of acute asthmatic attack.

Bronchospasm

Asthma is characterised by bronchospasm with precipitating factors such as allergy.

Anxiety for surgery may also precipitate bronchospasm.

It is important to reassure the patient for relief of anxiety.

Appropriate premedication has to be used by using anxiolytics and anti histaminics.

Sever e asthmatics with steroid therapy has to be given hydrocortisone as apremedication.

Asthma

During anaesthesia it is important to reduce irritation of broncial tree and intubation is avoided as far as possible.

Halothane is useful with its bronchodilating property.

In the event of bronchospasm during anaesthesia, 250-500mg of aminophylline is given intravenously over 5min which will improve ventilation.

Metabolic functions of the lungs

Lungs are major site of inactivation of 5-hydroxytryptamine,bradykinin and noradrenaline

Converting enzyme present on the luminal surface of endothelial cells catalyses the hydrolysis of angiotensin I to angiotensin II.

PGE1 , PGE2 or PGF2 are removed in one passage through lungs whereas PGA1 , PGA2 and prostacyclins pass through unchanged.

Prostacyclin, which is a vasodilator and potent inhibitor of platelet aggregation is produced partly in lungs.

Certain anaphylactic mediators like histamine and SRS-A (slow reacting substances of anaphylaxis)are also released by lungs.