A system responsible for gas exchange, supplying oxygen and removing carbon dioxide.

Anatomical Classification

Upper Respiratory Tract: Nose, Nasal cavity, Pharynx, Larynx

Lower respiratory Tract: Trachea, bronchi, Bronchioles, lungs and Alveoli

Functional classification

Conduction portion

Respiratory portion

Conduction Portion

It is made up of

Nasal cavity

Pharynx

Larynx

Trachea

Bronchial tree

Respiratory Portion

It consists of

Respiratory bronchioles

Alveolar ducts

Alveolar sacs

Gas Exchange

Ventilation: Movement of air in and out of the lungs

Regulation of blood pH

Smell (Olfaction)

Protection from particles

Assists Circulation

Vocalization (Speech Production)

Larynx: Is the organ of voice production and the part of the respiratory tract between the lower part of the pharynx and the trachea.

Made of

Cartilages

Membranes

Ligaments

Muscles

Three cartilages are single (thyroid, cricoid, and epiglottic) and three are paired (arytenoid, corniculate, and cuneiform).

Single

Thyroid

Cricoid

Epiglottic

Paired

Arytenoid

Corniculate

Cuneiform

Extrinsic

Hyo-epiglottic ligament

Cricotracheal ligament

Median cricothyroid ligament

Median thyroid ligament

Lateral thyroid ligament

Intrinsic

Cricothyroid ligament

Extrinsic

Thyrohyoid membrane

Intrinsic

Quadrangular membrane

Extrinsic muscles

Suprahyoid muscles

Infrahyoid muscles

Stylopharyngeus

Intrinsic muscles

Cricothyroid

Thyroarytenoid

Posterior cricoarytenoid

Lateral cricoarytenoid

Transverse and oblique Arytenoids

There are two important soft tissue folds located within the larynx

The vestibular folds (False vocal cords)

Vocal folds (True vocal cords)

They play critical role in protection of the airway, breathing, and phonation.

BLOOD CIRCULATION

Blood supply is through superior and inferior laryngeal arteries.

Venous drainage is by thyroid veins which join the internal jugular.

INNERVATION OF LARYNX.

Nerve innervation is through parasympathetic and sympathetic fibres

The parasympathetic supply is from superior and recurrent laryngeal nerve which is the branch of vagus nerve.

Sympathetic is from superior cervical ganglia.

Swallowing

Respiration

Phonation

The pharynx is a fibromuscular tubelike structure extending from the base of the skull.

Divided into three parts

The nasopharynx: lies behind the nasal cavity, consists of ciliated pseudostratified columnar epithelium.

The oropharynx: lies behind the oral cavity, stratified squamous epithelium.

The laryngopharynx (hypopharynx): Extends from the tip of the epiglottis to the esophagus, lined with moist stratified squamous epithelium.

The pharynx is composed of three layers of tissue

Mucous membrane lining

Fibrous tissue

Muscle tissue: consists of several involuntary constrictor muscles that play an important part in the mechanism of swallowing (deglutition) which, in the pharynx, is not under voluntary control.

Blood supply is from several branches of facial artery.

Venous return is into facial and internal jugular vein.

The nerve supply

The parasympathetic is from vagus and glossopharyngeal nerves.

The sympathetic is from superior cervical ganglia.

Passageway for air and food

Warming and humidifying air

Protection

Taste

Facilitates Hearing

The pharynx is also important in vocalization and Speech

Outline the structure of the trachea

Explain the functions of the trachea in respiration

Structure of bronchi

Structure of bronchiole

The trachea is a tube formed of cartilage and fibromuscular membrane, lined internally by mucosa.

Begins at the inferior border of the cricoid cartilage (C6) as a continuation of the larynx and ends by bifurcating at the carina into the right and left main stem bronchi at the level of the sternal angle (disc between T4 and T5).

Is approximately 10-12 cm in length and has 16 to 20 incomplete hyaline cartilaginous rings that open posteriorly toward the esophagus and prevent the trachea from collapsing.

Superiorly – the larynx

Inferiorly – the left and right bronchi

Anteriorly –upper part: the isthmus of the thyroid gland, lower part: the arch of the aorta and the sternum

Posteriorly – the esophagus separate the trachea from vertebral column.

Laterally – the lungs and lobes of thyroid gland

The trachea is composed of from 16 to 20 incomplete (C-shaped) rings of hyaline cartilages lying one above the other.

The free ends of these rings are supported by the trachealis muscle.

Connective tissue and involuntary muscle join the cartilages and form the posterior wall where they are incomplete.

The soft tissue posterior wall is in contact with the esophagus.

There are three layers of tissue which ‘clothe’ the cartilages of the trachea.

The outer layer. This consists of fibrous and elastic tissue and encloses the cartilages.

The middle layer. This consists of cartilages and bands of smooth muscle that wind round the trachea in a helical arrangement. There is some areolar tissue, containing blood and lymph vessels and autonomic nerves.

The inner lining. This consists of ciliated pseudostratified columnar epithelium, containing mucus-secreting goblet cells.

The combination of sweeping movements by the cilia and mucus from the goblet cells forms the functional mucociliary escalator.

The nerve supply.

Parasympathetic supply is by the recurrent laryngeal nerves and other branches of the vagi.

Sympathetic supply is by nerves from the sympathetic ganglia.

Blood circulation.

Arterial supply is mainly by the inferior thyroid and bronchial arteries

Venous return is by the inferior thyroid veins into the brachiocephalic veins

Mucociliary escalator

Support and patency

Warming, humidifying and filtering of air

Support and patency

Cough reflex.

It conducts air into the lungs.

It is made up of hyaline cartilage.

It is lined by the mucous membrane which undergoes a transition from ciliated pseudostratified columnar epithelium to simple cuboidal epithelium to simple squamous epithelium.

No gas exchange takes place in this part of the lungs.

Two primary bronchi are formed when the trachea divides, about the level of the 5th thoracic vertebra.

THE RIGHT BRONCHUS

This is wider, shorter and more vertical than the left bronchus and is therefore the more likely of the two to become obstructed by an inhaled foreign body.

After entering the right lung at the hilum it divides into three branches, one to each lobe.

Each branch then subdivides into numerous smaller branches.

This is narrower than the right.

After entering the lung at the hilum it divides into two branches, one to each lobe.

Each branch then subdivides into progressively smaller tubes within the lung substance.

Within the lungs, the main(primary) bronchi branch into lobar (secondary) bronchi

There are 3 right lobar and 2 left lobar bronchi

The lobar bronchi then bifurcate into several segmental (tertiary) bronchi, each of which supplies a bronchopulmonary segment, which are subdivisions of the lung lobes, and acts as the functional unit of the lungs.

The structure of bronchi are very similar to that of the trachea

Though differences are seen in the shape of their cartilage

In the main bronchi, cartilage rings completely encircle the lumen.

However in the smaller lobar and segmental bronchi cartilage is found only in crescent shapes.

The segmental bronchi undergo further branching to form numerous smaller airways- the bronchioles

Do not contain any cartilage or mucus-secreting goblet cells.

Club cells produce a surfactant lipoprotein which is instrumental in preventing the wall of the small airways sticking together during expiration.

Conducting bronchioles, lacking gland, ends as terminal bronchioles

Terminal bronchioles branch further into respiratory bronchioles, which are distinguishable by the presence of alveoli extending from their lumens

Terminal bronchioles branch further into respiratory bronchioles, which go on to divide into 2 to 11 alveolar ducts

There are 5 or 6 alveolar sacs associated with each alveolar duct.

ALVEOLI are tiny air-filled pockets with thin walls (simple squamous epithelium) and are the site of gaseous exchange in the lungs.

Are the organs of respiration.

They are located in the thorax, either side of the mediastinum

Each lung is surrounded by a pleural cavity, which is formed by the visceral and parietal pleura.

The are suspended from the mediastinum by the lung root- a collection of structures entering and leaving the lungs.

The medial surfaces of both lungs lie in close proximity to several mediastinal structures.

LEFT LUNG

Heart

Arch of aorta

Thoracic aorta

Esophagus

RIGHT LUNG

Esophagus

Heart

Inferior vena cava

Superior vena cava

Azygous vein

They are roughly cone shaped, with an apex, base, three surfaces and three borders.

The left lung is slightly smaller than the right- due to the presence of the heart.

Each lung consist of

Apex

Base

Lobes

Surfaces

Borders

The blunt superior of the lung

Projects upwards, above the level of the 1st rib and into the floor of the neck.

BASE

The inferior surface of the lung, which sits on the diaphragm

The right lung has three lobes

Superior

Middle

Inferior

The lobes are divided from each other by two fissures

Oblique fissure

Horizontal fissure

The left lung has superior and inferior lobes, separated by oblique fissure.

The mediastinal surface,

faces the lateral aspect of the middle mediastinum

The hilum is located on this surface

The diaphragmatic surface

Rests on the dome of the diaphragm, and has concave shape.

This concavity is deeper in the right lung, due to the higher position of the right dome overlying the liver.

The costal surface

It faces the internal surface of the chest wall.

The anterior border

Formed by the convergence of the mediastinal and coastal surfaces

The inferior border

Separate the base of the lung from the costal and mediastinal surfaces

The posterior border

It is formed by the coastal and mediastinal surface meeting posterioly

The lung root is a collection of structures that suspends the lung from the mediastinum.

Each root contains a bronchus, pulmonary artery, two pulmonary veins, bronchial vessels, pulmonary plexus of nerves and lymphatic vessels.

All these structures enter or leave the lung via the hilum- a wedge shaped area on its mediastinal surface.

Supplied with deoxygenated blood by the paired pulmonary arteries.

Once the blood has received oxygenation, it leaves the lungs via four pulmonary veins ( two for each lung)

Bronchial arteries which arise from descending aorta supply oxygenated blood to the lung structures.

The bronchial veins provide venous drainage.

The right bronchial vein drains into the azygos vein

The left drains into the accessory hemiazygos vein.

Derived from the pulmonary plexuses

Parasympathetic

Derived from vagus nerve

Stimulate secretion from the bronchial glands, contraction of the bronchial smooth muscle, and vasodilation of the pulmonary vessels

Sympathetic

Derived from sympathetic trunks

Stimulate relaxation of the bronchial smooth muscle, and vasoconstriction of the pulmonary vessels.

Visceral afferent

conduct pain impulses to the sensory ganglion of the vagus nerve.

Superficial (subpleural)

Drains the lung parenchyma

Deep

Drains the structures of the lung root

Refers to the serous membranes that line the lungs and thoracic cavity.

They permit efficient and effortless respiration.

STRUCTURE OF THE PLEURAE

Consists of a serous membrane- a layer of simple squamous cells(mesothelium) supported by connective tissue.

Each pleurae can be divided into two parts

Visceral pleura- covers the outer surface of the lungs, and extends into the interlobar fissures.

Parietal pleura- covers the internal surface of the thoracic cavity.

These two parts are continuous with each other at the hilum of each lung.

The space between the viscera and parietal pleura is known as pleural cavity, which contains a small volume of serous fluid

Major function of pleural fluid

It lubricates the surfaces of the pleurae

Produces a surface tension