Thorax

ThoraxThorax is the superier

part of the trunk between the neck and adomen.

It extends below the neck to the diaphragm.

It contains the primary organs of respiratory and cardiovascular system

Thoracic SkeletonThe thoracic skeleton

forms the osteocartilaginous thoracic cage, which protects the thoracic viscera and some abdominal organs.

Thoracic SkeletonThe thoracic skeleton

includes the thoracic cage formed by the horizontal bars formed by ribs and costal cartilages supported by the vertical sternum,anterierly and thoracic vertebrae,posterierly

A typical human rib cage consists of 24 ribs, the sternum, costal cartilages, and the 12 thoracic vertebrae.

All ribs are attached in the back to the thoracic vertebrae.

Thoracic ribs The upper seven are true ribs,

are attached in the front to the sternum by means of costal cartilage. Due to their elasticity they allow movement when inhaling and exhaling.

The 8th, 9th, and 10th ribs are called false ribs, and join with the costal cartilages of the ribs above.

The 11th and 12th ribs are known as floating ribs, as they do not have any anterior connection to the sternum.

The spaces between the ribs are known as intercostal spaces; they contain the intercostal muscles, nerves, and arteries.

SternumThe sternum is the

flat,elongated bone that forms the middle of the anterior part of thoracic cage.

The sternum consists of

1. Manubrium,2. Body,3. Xiphoid process

MediastinumThe thoracic cavity is

divided into three major spaces.

The central/median compartment called mediastinum houses the conducting structures(esophagus,trachea,major blood vessels and most importantly heart).

The two lateral compartments contains the lungs

Nasal cavity The lateral wall of the

nasal cavity is mainly made up by the maxilla, and the conchae on the wall

The floor of the nasal cavity, which forms the roof of the mouth, is made up by the bones of the hard palate.

The nasal cavity is divided in two by nasal septum.

Nasal CavityThe air passing through the nasal cavity is warmed or cooled to within 1 degree of body

temperature. humidified, and dust and other particulate matter

is removed by vibrissae, short, thick hairs, present in the vestibule.

The cilia of the respiratory epithelium move the particulate matter towards the pharynx where it passes into the esophagus and is digested in the stomach.

PharynxThe pharynx (plural:

pharynges) is the part of the neck and throat situated immediately posterior to (behind) the mouth and nasal cavity

PharynxThe pharynx is part of

the digestive system and respiratory system

food and air pass through the pharynx, a flap of connective tissue called the epiglottis closes over the trachea when food is swallowed to prevent choking or aspiration.

PharynxThe human pharynx is

conventionally divided into three sections:

NasopharynxOropharynxLaryngopharynx

Nasopharynx The nasopharynx region

extends between the internal nares and the soft palate and lies superior to the oral cavity.

The Eustachian tubes, or auditory tubes(equalizing the air pressure in the middle ear to that of the atmosphere. This is needed for proper conduction of sound), which connect the middle ear to the pharynx, open into the nasopharynx.

OropharynxThe oropharynx lies

behind the oral cavity.the lateral wall is

made up of the tonsil, the superior wall consists of the inferior surface of the soft palate and the uvula.

Laryngopharynx It lies inferior to the

upright epiglottis and it is continuous with the respiratory tract anterierly and digestive pathways,posterierly.

During swallowing, food has the "right of way", and air passage temporarily stops.

epiglottis closes over the trachea when food is swallowed

larynxThe larynx ("voice

box“), is involved in protection of the trachea and sound production.

The laryngeal skeleton consists of nine cartilages: three single (thyroid, cricoid, and epiglottic) and three paired (arytenoid, corniculate, and cuneiform).

Nerve supply of Larynx

Superier and inferior laryngeal brances of vaus nerve(CN X).

Superier laryngeal nerve divides into int(supplies sensory and autonomic) and ext(motor) laryngeal nerve

Inferier laryngeal nerve is the primary motor nerve

Trachea The trachea (windpipe), is

a fibrocartilagenous tube that connects to the pharynx/larynx, to the lungs.

It has mucosal goblet cells which produce mucus. This mucus lines the cells of the trachea to trap inhaled foreign particles which the cilia then waft upwards towards their larynx and then the pharynx where it can either be swallowed into the stomach or expelled as phlegm.

Trachea Trachea is supported by incomplete cartilaginous

rings(keeping the trachea patent), that occupies a median position in the neck.

The posterior gap in tracheal rings is spanned by involuntary trachealis muscle,smooth muscle connecting the ends of the cartilages.

The esophagus is right behind the trachea, so the smooth muscle of trachea can accommodate according to the esophagus.

The brachiocephalic trunk is related to the right side of the trachea in the root of the neck.

So any deviation of the trachea from midline,apparent superficially or radiographically, is the sign of any pathological process.

Trachea Trachea bifrucates at

the level of sternal angle into primary bronchus, one to each lung to enter the lung at the hila

The right main bronchus is wider,shorter and runs more vertically than left

Within the lungs the bronchi branch in a constant fashion.

Each main bronchus divides into lobar bronchi(secondary bronchi) 2 on left and 3 on right.

Lobar bronchus several segmental bronchi

segmental bronchi after 30-35 generation of branches end in terminal bronchioles.

Terminal bronchioles respiratory bronchiole alveolar ducts alveolar sacs , which are lined by alveoli

Lungs Their principal function is

to transport oxygen from the atmosphere into the bloodstream, and to release carbon dioxide from the bloodstream into the atmosphere.

This exchange of gases is accomplished in the mosaic of specialized cells that form millions of tiny, exceptionally thin-walled air sacs called alveoli,that are sorrounded by the pulmonary capillaries

pleura The pleura is a serous

membrane which form a two-layered, membrane structure.

The outer parietal pleura is attached to the chest wall.

The inner visceral pleura covers the lungs

The thin space between the two pleural layers is known as the pleural cavity; it normally contains a small amount of pleural fluid

The parietal pleura is highly sensitive to pain while the visceral pleura is not, due to its lack of sensory innervation.

Bronchopulmonary SegmentsRight lung is divided

into superier,middle and inferior lobes

Left lung is divided into superior and inferior lobe

•These lobes are inturn divided into 10 bronchopulmonary segments, each of which are seperated anatomically from each other by a connective tissue layer.•each segment is indepently supplied by a segmental bronchi and a tertiary branch of pulmonary artery.

AlveoliPulmonary alveolus is

the basic structural unit of gas exchange in the lung.

In both lungs by 8 yrs of age we have 300 million alveoli

Blood supply

The lungs have a double blood supply, the pulmonary circulation for gas exchange with the alveoli and the bronchial circulation to supply the parenchyma (tissue) of the lung itself.

MediastinumThe thoracic cavity is

divided into three major spaces.

The central/median compartment called mediastinum houses the conducting structures(including pericardium,heart and roots of its great vessels

PericardiumThere are two layers to

the pericardial sac: 1. the fibrous

pericardium and2. the serous

pericardium. The serous

pericardium, in turn, is divided into two layers, the parietal pericardium and visceral pericardium

In between the parietal and visceral pericardial layers there is a potential space called the pericardial cavity.

It normally contains thin film of fluid,pericardial fluid that enables the heart to move and beat in a frictionless environment

The inferior wall of the fibrous pericardium is firmly attached and partically blended with central tendon of diaphragam. The heart is well tethered in place inside the fibrous sac

HeartThe wall of each heart chamber consists of 1. Endocardium:thin internal layer of endothelium2. Myocardium: thick, middle layer composed of

cardiac muscle3. Epicardium:thin external layer fromed by the

visceral layer of serous pericardium

The heart has four chambers:

Right and left atriaRight and left

Ventricles

Three borders of the heart:

right border made up of the right atrium

inferior border made up of right atrium, right ventricle and left ventricle

left border made up of the left ventricle

Surfaces of the heart

Anterior sterno-costal surface, formed mainly by R. ventricle

Diaphragmatic or inferior surface is formed mainly by L. ventricle and partly by R. ventricle.

Right pulmonary surface is formed by R. atrium

Left pumonary surface is formed by L. ventricle which forms the cardiac impression of the left lung

Apex of the heart Is the infero-lateral

part of left ventricleLies beneath the 5th

intercostal space in adults, approxiamately 9 cm from median plane

Is where the sounds of mitral valve closure(apex beat) are maximal

Atrium

The superior vena cava opens at the level of R. 3rd costal carilage and inferior vena cava at 5th costal cartilage.

The right atrium opens into the R. ventricle thru Tri cuspid valve

The pairs of right and left pulmonary veins enter the posterior aspect of atrium.

The left atrium opens into L. ventricle thru Bicuspid or mitral valve.

Left AtriumRight Atrium

AuriclesThe auricles are think ear-like conical

muscular pouch which projects from the atria, increasing the capacity of atria

Each atria has an auricle on the superior surface

Ventricles

Receives the deoxygenated blood from the atium

And thru R. and L. pulmonary arteries pumps blood to the lungs

Receives the oxygenated blood from the atium

And thru Aorta pumps blood to the systemic circulation

Left ventricleRight ventricle

Papillary muscles Papillary muscles are

nothing but the conical muscular projections from the myocardium of the heart

They support, strenghthen and responsible for the opening and closure of the cuspid valves.

They area attached to the cuspid valves thru tendinous cords called chordae tendinae

Conducting systemof the heartConducting

system of the heart consists of the cardiac muscle cells, SA and AV nodes, purkinje fibres and Bundle of His.

Nodal tissuesSinuatrial node(SA)

is located antero-laterally just deep to epicardium at the jucnction of SVC and R.atrium.

It is the pacemaker of the heart,initiating and regulating the impulses for contraction.

It is a small collection of nodal tissue and specialized cardiac muscle fibres.

It could be stimulated or inhibited by the sympathetic or parasympathetic division

Atrio-Ventricular Node(AV)

Smaller collection of nodal tissue than SA node.

Located in the posteroinferior region of the interatrial septum.

Bundle of His, Purkinje firbesAV bundle- the AV

node passes the signal from atrium to the ventricles thru AV bundle,which is the only bridge between the atrial and ventricular myocardium.

Av bundle divides into R. and L. bundles.

These bundles proceed on each side and then ramify into subendocardial branches(purkinje fibres)

These purkinje fibres on both side stimulate the IVS, papillary muscles and respective ventricles.

Nerve supply to the heartThe sympathetic

fibers arise from segments T2-T4 of the spinal cord

The vagus provides the parasympathetic control to the heart

Nerve supply to the heartThe cardiac plexus,

the nerve network consisting of both sympathetic and parasympathetic nerves is located primarily in the level of bifurcation of trachea.

This supplies the nodal tissues, conducting system and coronary vessels

Sympathetic or adrenergic stimulation causes increased heart rate; impulse conduction; also increases the blood flow through the coronary vessels.

Parasympathetic stimulation slows the heart rate,reduces the force of contraction

Vasculature of the heart

Endocardium receive O2 and nutrients by diffusion or microvasculature directly from the chambers of the heart.

The R. and L. coronary artery the direct and the first branches of aorta, arising from R. & L. aortic sinus supplies both atria and ventricles.

R. Coronary arteryRCA supplies1. SA node thru sinuatrial nodal branch2. Right border of the heart thru R.marginal

branch3. AV node thru atrioventricular nodal

branchIt supplies R. atrium, most of R. ventricle.

L. Coronary artery LCA L. marginal artery ant. Interventricular branch

L. marginal artery circumflex branch of L. coronary artery

ant. Interventricular branch lateral diagonal branch

L. Coronary artery Left border thru L. Marginal arteryMost of L.ventricle and part of R.ventricle

and apex thru ant. Interventricular branchIt supplies L.atrium , most of L.ventriclePart of R.ventricleMost of interventricular systemApex of the heart

Posterier interventricular artery is given out by the RCA(66%) in the Right dominant coronary arterial system.

Post & ant interventricular artery anastomosis at the posterior aspect.

AortaThe ascending

aorta,which is intra-pericardial begins at aortic orifice and gives out coronary arteries

The arch of aorta which is the continuation of

ascending aorta begins at the the 2nd R.sternocostal joint at the level of sternal angle

It gives out brachiocephalic trunk,left common carotid artery and L. subclavian artery.

The brachiocephalic trunk first and largest branch of arch of aorta gives out R.common carotid artery and R.subclavian artery

Thoracic aortaThoracic aorta,which is a continuation of

arch of the aorta extends between the levels of T5-T12 verterbrae.

They give out posterior intercostal arteries, subcostal, some phrenic arteries and visceral branches (eg.,esophaus, bronchial for bronchus and visceral pleura)