THE TRACHEA
Is a mobile tube formed by cartilaginous bars and lined by mucous membrane ,it begins as a continuation of the larynx (lower border of cricoid ) level with C6 vertebra and ends below as a carina (an angle of tracheal bifurcation at level of T4-T5 vertebra ( level of sternal angle) where it bifurcates into the right & laft bronchi (behind the arch of Aorta.It is 4 inches (11.25 cm) in length and 1 inch (2.5 cm) in width,in infants it is about 1.6-2 inches in length and about 3 mm in diameter.It consists of tracheal rings of cartilaginous bars which are completed posteriorly by smooth muscles connecting the edges of the bars ,it is lined by pseudostratified ciliated columnar epithelium.The TRACHEA has the following relations.ANTERIORLY by the skin ,fascia,isthmus of thyroid gland(in front of 2nd – 4th tracheal rings),inferior thyroid artery,jugular arch and occasionally thyrodea ima artery if present.
POSTERIORLY by the R.&L. recurrent laryngeal nerves and the Esophagus.
LATERALLY on each side by a lobe of thyroid gland & the carotid sheath.
In the Thorax it has the following relations:
ANTERIORLY the back of sternum,thymus gland,L.Brachiocephalic V plus arch of Aorta & L.Subclavian &left common carotid arteries.
POSTERIORLY BY esophagus& L.recurrent laryngeal nerve ,azygos V.& Vagi nerves.
The trachea bifurcates in to R .main bronchus at about 25 degree angle ( more in line with the trachea and may lodge a foreign body )& left bronchus at about 45 degree angle with the trachea,put in mind that in younger than 3 years both arise at same angles.
The bronchi divides in to millions of terminal bronchioles,which in turn gives respiratory bronchioles which gives 2-11 alveolar duct sacs and from the alveolar duct arises many alveoli as diverticulae from the side wall of the sac.The right bronchus is wider,shorter & more vertical than the left one.The Azygos vein arches over its upper border and the right bronchus gives the superior lobar bronchus at the level of Carina ,then the right principal bronchus enters the hilum of the R.Lung to give the middle & inferior lobar bronchi.The R.Bronchus is a bout 2,5 cm in length where as the Left one is a bout 5 cm in length.
The left bronchus is narrower & taller than the right one & is more horizontal than the rihjt one once it starts.It passes to the left behind the Arch of Aorta in front of the esophagus .It divides into superior & inferior lobar bronchi as it enters the lung root.
THE PLEURAE
Two serous sacs surrounding the lungs.Each pleura consists of 2 parts ,a parietal ( lines the thoracic wall,covers the thoracic surface of the diaphragm& extends into the root of the neck as a cervical part or Dome of pleura) and a visceral layer completely surrounds the outer surface of the lungs& extends in to the depth of the fissures.The parietal becomes continuous with visceral by a cuff of pleura which surrounds the structures entering &leaving the lung at the hilum to allow movement of pulmonary vessels & the bronchi during respiration ,The 2 layers of pleura are separated by a slit like space known as pleural cavity.
The nerve supply of the visceral pleura is by autonomic fibers from pulmonary plexus,while the parietal layer is supplied by intercostal nerves for the costal part,phrenic nerve for the mediastinal part & diaphragmatic part of parietal pleura and the peripheral parts of diaphragmatic pleura by intercostal nerves.
Each lung has a thin & sharp anterior border ,but on the left side this border is interrupted by the cardiac notch of the left lung,each lung has a blunt posterior border ,while the inferior border is sharp one & incinuate itself in to the costodiaphragmatic recess during deep inspiration.The lung is conical in shape whose apex projects to the root of the neck through the inlet of thorax & is separated from the structures at the root of the neck by the dome of the pleura & suprapleural membrane.The lungs are freely suspended by their roots to the mediastinum.The apex projects about 2.5 cm above the level of the clavicle,its base is concave and lies against the convexity of the dome of the diaphragm ,in adition its costal surface is convex facing the concave chest wall from inside,buts its mediastinal surface is concave.At about the middle of the mediastinal surface of each lung is the position of the hilum (lung root).
The right lung is shorter ,wider & heavier than the left lung.
The right lung has 2 fissures(oblique & horizontal fissures),while one fissure in the left lung ( oblique fissure).
The right lung is divided in to 3 lobes,while left lung into 2 lobes.
The mediastinal surface of the right lung shows a shallow impression for the heart,while the left lung shows a deeper impression caused by left ventricle.
The right lung root shows the right superior lobar bronchus & the continuity of the right main bronchus,while left lung root shows only the left main bronchus.
The oblique fissure runs from the inferior border upward,back ward a cross the medial &costal surfaces until it cuts the posterior border.
The horizontal fissure runs horizontally a cross the costal surface to meets the oblique fissure forming a small middle lobe between both fissures.
Related to the root of right lung the arch of a zygos vein above the lung root and the azygos vein behind the lung root
The root of left lung is related to the arch of aorta above the lung root and descending thoracic aorta behind the lung root.
THE BRONCHOPULMONARY SEGMENTS:
Are the anatomical,functional & surgical units of the lungs.Each lobar bronchus divides in to segmental (Tertiary) bronchi,this segmental bronchus leads to a piece of lung tissue to bring to it some amount of inspired air for the exchange of gasses between the alveoli & capillary plexus on the walls of the alveoli.Thus bronchopulmonary segment is being considered as a subdivision of a lung lobe which is pyramidal in shape(surrounded byC.T ) has a segmental bronchus ,artery lymphatic & autonomic nerve fibers.The vein lies in the C.T between adjacent bronchopulmonary segments.The segmental bronchus divided repeatedly until becomes smaller & smallers where the U shaped Bars of cartilage are replaced by plates of very thin cartilage,the smallest bronchi divides repeatedly and give to Bronchioles ( of less than 1 mm in diameter ).The bronchioles pocesses no cartilages on their walls & lined by columnar ciliated epithelium,the submucosa contains circularly arranged smooth muscle fibers and eventually the bronchioles gives Terminal Bronchioles ( Respiratory Bronchioles ) & each in turn ends by branching into Alveolar Ducts.Each alveolar duct give to Alveolar Sacs as an out pouchings .Now each Alveolar Sac is surrounded by a rich network of capillaries & lymphatics to allow gaseous exchanges on the wall of these out pouching(Alveolar Sacs ).
The Right Lung has the following B-P segments:
Superior lobe has 3 segments,an apical,anterior & posterior B-P segments.
The middle lobe has 2 segments a lateral & medial segments.
The inferior lobe has 5 segments named as apical,anterior,posterior,lateral & medial basal B-P segments……
The left lung has the following B-P segments :
The superior lobe gives apico-posterior,anterior &lingular (superior & inferior) segs
The inferior lobe gives 5 segment as that of the right side..
The bronchi , C.T of lung & visceral pleura by branches of Bronchial artery ( from descending thoracic Aorta ).The bronchial veins drain to Azygos vein on the right side & to hemiazygos on the left side.
The lymphatic drainage in to the superficial & deep pulmonary plexuses.The superficial ( subpleural ) plexus beneath the visceral pleura draining the surface of the lung and leads to the Bronchopulmonary (B-P) lymph nodes,while the deep pulmonary plexus are seen related to the bronchi & pulmonary vessels and passing the pulmonary nodes within the lung substance to end in the B-P lymph nodes in the lung root.Then from here ( i.e B-P nodes) goes to Tracheo-Bronchial lymph nodes & eventually leads in to the BRONCHO_MEDIASTINAL .
Nerves supply are from the pulmonary plexuses( Anterior & posterior) containing fibers from both sympathetic & parasympathetic .The sympathetic causes bronchodilatation & vasoconstriction ,while the parasympathetic components causes Bronchoconstriction & Vasodilatation in addition it increases the glandular secretion
Surface marking of pleurae:The cervical part of parietal pleura ( Dome of pleura ) project through the inlet of thorax to the root of the neck(just like the apex of the lung) and is being separated from the structures at the root of the neck by suprapleural membrane which interveans between these structures & the dome of the pleura..it starts from sternoclavicular joint to appoint about 1 inch (2.5 cm ) above the junction between the medial & intermediate thirds of the clavicle.The anterior border pf parietal pleura( on Right side ) extends anteriorly & down wards from the Right sternoclavicular joint to the level of the sternal angle and then continues down ward to the level of Xiphisternal joint.
While on the left side the anterior border descends downward too till the level of the 4th costal cartilage ,then deviates laterally along the lateral margin of the sternum to reach the level of the cardiac notch.It then descends sharply to reach the level of Xiphisternal joint
The inferior border of the parietal pleura will passes downward and laterally from Xiphisternal joint crossing the 8th Rib at the midclavicular line, the 10th Rib at midaxillary line & the 12th Rib adjacent to the vertebral column >the posterior border of the parietal pleura extends from the back of the Dme of pleura above to end just below the neck of the last rib where it meets the terminal end of the line representing the anterior border of the pleura.
The lungs has the same surface markings as that of parietal pleura except that the inferior border of the lung is 2 vertebral level of the pleura .Thus inferior border of the lung crosses the 6th Rib at midclavicular line,the 8th ib at midaxillary line & 10th Rib
The space between the inferior border of the lung & the parietal pleura represents the COSTODIAPHRAGMATIC pleural recess which the lung is going to occupy it completely only in deep inspiration as in cases of a cute attacks of Asthma…
The Pleural recess are in fact a gap or small spaces forms due to reflection of one part of parietal pleura against another part and normally these recesses are not occupied by lung tissues except in some cases as in Asthma and we have 3 named recess as:
1-Costodiaphragmatic due to reflection of costal against diaphragmatic parts of the parietal pleura.
2-Costomediastinal due to reflection of costal against the mediastinal part of the parietal pleura.
3-Mediastinodiaphragmatic forms due to reflection of the mediastinal against the diaphragmatic part of parietal pleura ( this recess is not important and is the smallest one among the 3 recesses ).
THE CARDIOVASCULAR SYSTEM
Is the system responsible for pumping the blood from the heart into the great blood vessels attached to it,which then takes the responsibility for conducting & circulating this blood to different parts of the body where it supplies oxygenated blood by arteries and collecting deoxygenated blood from different parts of the body and bring it back to the heart by veins.The system includes :
1-The Pumping Heart.
2-The Blood Vessels.
The heart pumps blood to two Circuits:
A-Minor Circuit ( pulmonary circulation ) between the Right ventricle & lung ,then back to the left atrium by 4 pulmonary veins ( bring back oxygenated blood to the heart ).
B- Major or Systemic Circuit , between left ventricle and different parts of the body to supply oxygenated blood ( except the lungs) and bringing back deoxygenated blood from these organs to the Right Atrium by the superior & inferior vena cavae.
The heart is located in the chest inside the pericardium within the middle mediastinum.
THE MEDIASTINUM
Is a median space or connective tissue septum contains many structures embedded in it within the thoracic cavity.It extends from the middle part of thoracic inlet ( superior thoracic aperture) to the middle part of the outlet ( inferior thoracic aperture) i.e just superior to the diaphragm.It is bounded on each side by the medial surface of the lungs& mediastinal part of the parietal pleura ,behind the sternum (anteriorly) and in front of all the thoracic vertebrae(posteriorly) & is divided by an imaginary plane passing between the sternal angle & and the intervertebral disc between T4-T5 vertebrae in to a superior above this plane & inferior mediastinum below it( the inferior is subdivided into 3 parts ,an anterior,middle & posterior mediastinums).
The superior mediastinum: It is the part above the imaginary plane between sternal angle & the disc between T4 –T5 vertebrae and between the manubrium sterni & the upper 4 thoracic vertebrae.It extends from middle part of the inlet &the imaginary plane passing between the sternal angle and the intervertebral disc between T 4-T5 vertebrae. .
CONTENTS of Superior mediastinum are the followings:
1-Arch of Aorta and the 3 grat arteries arising from it namely,Brachiocephalic,left commo
Carotid & left subclavian arteries.
2-Right & left Brachiocephalic veins.
3-The upper half of superior vena cava.
4-The Thymus Gland.
5-Left & Right Vagii nerves.
6-Left & Right Phrenic Nerves.
7-Sympathetic trunks or chains.
8-The Left Recurrent Laryngeal Nerve.
9-The Thoracic part of the Trachea.
10-The Arch of The Azygos Vein.
11-The Thoracic Duct.
12-Lymph nodes groups.
The anterior mediastinum: Is the part of the inferior mediastinum encloses between the body of the sternum & anterior to the pericardium .It contains :
1-The superior & inferior sternopericardial ligaments( Strap ligaments ).
2- Anterior mediastinal lymph nodes.
The Middle Mediastinum: Is the part of inferior mediastinum occupied by the pericardium containing the heart inside it & it contains :
1-The pericardium & the heart inside it.
2-Lower half of superior vena cava.
3-Terminal part of the inferior vena cava.
4-The ascending Aorta.
5-The Pulmonary Trunk.
6-The phrenic nerves & Pericardiophrenic vessels runnibg on each side of pericardium.
The Posterior Mediastinum: Is the part encloses between the back of pericardium & the lower eight thoracic vertebrae ( T5-T12) & is limited inferiorly by the slopping part of the Diaphragm in the direction of thoracic vertebrae. It contains :
1-The Esophagus.
2-The Descending Thoracic Aorta.
3-The Azygos Veinous System.
4-The sympathetic trunks.
5-The Two Phrenic Nerves.
6-The Right & Left Vagi Nerves.
7-The Thoracic Duct.
8-Posterior Mediastinal Lymph Nodes.