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What are the important topics of the Thorax Anatomy

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In this post we have discussed all the important questions topics of the Thorax anatomy. This topics can help you to understand the theory and Viva exam questions.

Meaning/ Definition :

The thorax is a cavity which is divided by the Diaphragm into two parts :

  • The upper part is called the Thoracic cavity.
  • The lower part is called the Abdominal cavity.

What are the important topics :

1. What is the boundary of the Thoracic cage :

  1. Anteriorly : By Sternum
  2. Posteriorly : By 12 thoracic vertebrae and intervening intervertebral discs
  3. Laterally : By 12 pairs of ribs and associated 12 pairs of costal cartilages

The rib cage is formed by sternum, costal cartilages, and ribs attached to the thoracic vertebrae.

2. What are the Bones and Joints of the Thorax :

What are the Bones of the thorax :

  1. Sternum : This is an elongated bone which lies in the anterior median part of the chest wall.
  2. Ribs : The ribs are flat, ribbon-like, elastic bony arches which extend from thoracic vertebrae posteriorly to the lateral borders of the sternum anteriorly.
  3. Thoracic Vertebrae : There are 12 thoracic vertebrae classified into two types : Typical(2nd-8th), Atypical(1st, 9th-12th)

What are the Joints of thorax :

  1. Costovertebral These joints are formed by the articulation of articular facets on the head of ribs and costal facets on the bodies of thoracic vertebrae.
  2. CostotransverseIn this joints the tubercle articulates with the transverse process fo the numerically corresponding vertebrae to form a synovial joint.
  3. Costochondral These are primary cartilaginous joints between the anterior end of the rib and its cartilage .
  4. Chondrosternal Joints between the medial ends of 1st-7th costal cartilages and lateral border of the sternum.
  5. InterchondralHere the 7th-9th costal cartilages comes in contact with one another and articulate with each other by number of small synovial joints.
  6. Manubriosternal This joint is formed between the lower end of the manubrium stern and upper end of the body of sternum.
  7. Intervertebral Formed between the bodies of the vertebrae, and between the articular processes of the vertebra.

3. Coarctation of Aorta :

This is narrowing of the arch of aorta, where the posterior intercostal arteries are markedly enlarged and cause notching of the ribs, particularly in their posterior parts.

4. Pleura of the lung :

Pleura is the covering of the lung, is a serous membrane lined by flattened epithelium(mesothelium). The lining epithelium secretes a watery lubricant which is called the serous fluid.

Layers of Pleura : Visceral pleura, and parietal pleura.

  • Visceral Pleura : The visceral pleura covers the surface of the lung except at the hilum.
  • Parietal Pleura : This pleura thicker than the visceral pleura and lines the walls of the pulmonary cavity.

Recesses of the Pleura :

  • Costodiaphragmatic recesses : Located inferiorly between the costal and diaphragmatic pleurae.
  • Costomediastinal recesses : Located anteriorly between the costal and mediastinal pleurae and lies between sternum and costal cartilages.

Nerve Supply :

  • Intercostal nerve : Supply the costal and peripheral part of the diaphragmatic pleura.
  • Phrenic nerve : Supply the mediastinal and central part of the diaphragmatic pleura.

The Visceral pleura is develops from splanchopleuric layer of the lateral plate of mesoderm, hence it is supplied by the autonomic nerves(T2-T5).

5. Lungs gross anatomy :

These are principal organs of respiration.

Each lung hold the following parts :

  1. Apex
  2. Base
  3. Three borders(anterior, posterior, and inferior)
  4. Two surface (costal and medial)
  • Arterial Supply : Bronchial arteries and Pulmonary arteries
  • Venous Drainage : Bronchial veins and Pulmonary veins
  • Lymphatic Drainage : The lymph from the lung is drained by two sets of lymph vessels : Superficial and Deep vessels.
  • Nerve Supply : The parasympathetic fibres are derived from the vagus nerve and sympathetic fibres are derived from T2-T5 spinal vertebrae region.

Lobes and Fissures :

The right lung has three lobes(Superior, Middle and Inferior)

The left lung has two lobes (Superior and Inferior)

Root of the Lung :

The root of the lung is a short broad pedicle connecting the medial surface of the lung with the mediastinum.

Components :

  1. Principal bronchus in the left lung, and eparterial and hyparterhal bronchi in the right lung.
  2. Pulmonary artery
  3. Pulmonary veins
  4. Bronchial arteries
  5. Bronchial veins
  6. Lymphatics of the lung
  7. Anterior and posteror pulmonary plexuses of the nerves

Bronchopulmonary Segments :

This is well-defined, wedge-shaped sectors of the lung, which are aerated by tertiary bronchi.

There are 3 segments are present.

They are : Lateral aspect, Medial aspect, Lobar and Segmental bronchi

6. Mediastinum of thorax :

This is the median septum of the thoracic cavity between the two pleural cavities.

Boundaries :

  1. Anterior : Sternum
  2. Posterior : Vertebral column
  3. Superior : Superior thoracic aperture
  4. Inferior : Diaphragm
  5. On each side : Mediastinal pleura

Contents :

  1. Thymus
  2. Heart enclosed in the pericardial sac
  3. Major arteries and veins such as thoracic aorta, pulmonary trunk, etc.
  4. Trachea
  5. Esophagus
  6. Thoracic duct

Division :

There are mainly 4 division of the Mediastinum : Superior, Anterior, Middle and Posterior Mediastinum.

7. Diaphragm muscular structure :

The thoracic outlet is closed by a large dome-shaped flat muscle called diaphragm.

  • Origin : Sternal, Costal and Vertebral
  • Insertion : The muscles fibres converge towards the central tendon and insert into the margins.

Major Openings :

  1. Vena Caval opening
  2. Esophageal opening
  3. Aortic opening

Minor Openings :

  1. Superior epigastric vessels
  2. Musculophrenic artery
  3. Lower five intercostal nerves and vessels
  4. Subcostal nerves and vessels
  5. Sympathetic chain
  6. Greater, lesser, and least splanchnic nerves
  7. Hemiazygous vein

8. Pericardium sac/layer :

This is a fibroserous sac which encloses the heart and the roots of its great blood vessels.

Functions :

  1. Restricts the excessive movements of the heart
  2. Serves as a lubricated container in which the heart can contract and relax smoothly.
  3. Limits the cardiac distension

Subdivisons :

  1. An outer single layered fibrous sac : Fibrous pericardium
  2. Inner double layered serous sac : Serous pericardium

9. Heart viscera:

The organ which acts as a blood pumping machine in our body.

Has 4 components :

  1. Apex
  2. Base
  3. Three surfaces( Sternocostal, Diaphragmatic, and left)
  4. Four borders ( right, left, upper and inferior)

Chambers :

  1. Right atrium
  2. Right ventricle
  3. Left atrium
  4. Left ventricle

Valves of the heart :

  1. A pair of atrioventricular valves : Bicuspid/mitral valve (in Left), Tricuspid valve(In right)
  2. A pair of semilunar valves : Pulmonary valve and Aortic valve

Blood Supply :

  1. Arterial Supply : By the Right and Left coronary artery
  2. Venous drainage : By Coronary Sinus, Anterior cardiac sinus, Venae cordis minima e

10. Superior Vena cava :

  • This is 7cm long and 1.25cm in diameter.
  • Formed at the lower border of the right 1st costal cartilage by union of right and left brachiocephalic veins.

11. Ascending Aorta :

It arises from the upper end of the left ventricle.

Branches :

  1. Right coronary artery from anterior aortic sinus
  2. Left coronary artery from left posterior aortic sinus

12. Arch of Aorta :

This is the continuation of the Ascending Aorta at the level of sternal angle and continues as descending thoracic aorta at the level of sternal angle.

Branches :

  1. Brachiocephalic artery
  2. Left common carotid artery
  3. Left subclavian artery

13. Trachea and Oesophagus :

Trachea :

Long pipe like structure extends from the lower border of cricoid cartilage in the neck to the lower border of T4 vertebrae in the thorax.

  • Length : 10-12cm
  • External diameter : 2cm in males and 1.5cm in females
  • Internal diameter : 12mm in adult, 3mm in newborn
  • Lumen : 3mm(1year of age), 5mm(5year of age), 12mm(in Adults)

Oesophagus :

This is a narrow muscular tube extending from pharynx to the stomach

  • Length : 25 cm
  • Width : 2cm
  • Lumen : Flattened anteroposteriorly

Constriction of esophagus :

  1. First : at pharynx-esophageal junction, 9cm from incisor teeth
  2. Second : at 22.5cm from the incisor teeth where it is crossed by the Arch of aorta
  3. Third : 27.5cm from incisor teeth, crossed by the left principal bronchus
  4. Fourth : 40cm from incisor teeth, pierces the diaphragm

14. Thoracic Duct :

The main lymphatic conduit for returning chyle/lymph to the systemic venous system is the thoracic duct. It drains lymph from the lower limbs, the abdomen (excluding the liver’s convex area), the left hemithorax, the left upper limb, and the left face and neck.

15. Azygous Vein :

  • Present only in the right side.
  • Formed by the union of right subcostal and right ascending lumbar vein at the level of T12 vertebrae.

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