Surface anatomy of thorax

 Thorax

Rib counting : 

Heart:

 

1Apex of the   Heart

It is situated in the left 5^th intercostal space just medial to midclavicalar   line.

Related questions:  How it is formed?

Ans: It is formed by only left ventricle of the heart.

2.     Right   border of the Heart

1^st point: On   the upper border   of the right 3^rd costal cartilage about 2.5 cm from the median   plane.

2^nd point: on   the right 6^th costal cartilage about 2.5 cm from the median plane

Join these two points by a convex line towards the right.

SN: (The maximum convexity of which lies at a distance of 3.25am from the median plane in the 4^th intercostal space.)

Related questions:

How it is formed?  Ans: it is formed by right atrium

3. Left Border of Heart

1) 1^st    Point – On the lower border of the left 2^nd costal cartilage about 2.5 cm from the median plane.

2) 2^nd   point- At the apex beat left 5^th intercostal space just medial to mid-clavicular line Join   these two points by line with convexity directed upwards and to the left.

Related questions:

How it is formed? Ans: it is formed by left ventricle of the heart

4. Lower border of the Heart

1^st point: on   the right 6th costal cartilage about 2.5 cm from the median plane

2^nd   point-At the apex beat left 5^th intercostal space just medial to mid-clavicular line

Join these two points with slight notch to the right of the apex of the heart.

Inferior border passes through the xiphisternal junction

 Related questions: How it is formed? Ans: it is formed by mostly by right ventricle and partly by left ventricle

5. Upper border of the Heart

1^st point: On   the upper border   of the right 3^rd costal cartilage about 2.5 cm from the median   plane.

2^nd point: On the lower border of the left 2^nd costal cartilage about 2.5 cm from the median plane.

Join these points.

Related questions: How it is formed? Ans: 1/3 of right atrium and 2/3 of left atrium are formed this border

6. Arch of the Aorta

1) 1^st point –On the right end of the   sternal angle.

2) 2^nd point –On the   centre of the manubrium   sterni

3)3^rd point- sternal end of left 2^nd costal cartilage 

Join the points by a curved line which represents the outer border of the arch of aorta; then the inner   border is drawn   below  &  paralled to it about 2.5 cm apart  .

Importance points :  It is the continuation of ascending aorta and It is continued as descending thoracic aorta

Related questions : What are the branches of arch of aorta?

1.     brachiocephalic artery/ trunk : right common carotid and right subclavian artery

2.   left common carotid artery

3.   left subclavian artery

What is the type of these arteries?  Ans : elastic artery.

Why they known as elastic artery? They contain large numbers of elastic lamina within the tunica media. 

LUNG

1. Apex of the Lung

1^st point – rt/lt  sternoclavicular   joint

 2^nd point –at the junction of medial 1/3 and lateral 2/3 of clavicle

Join these two points & the summit of the curve being situated in the neck about 2.5cm above the medial   third of clavicle.    

by which structure  apex of the lung is covered?

Ans:    The apex of the lung is covered by cervical pleura (part of parietal pleura) and supra-pleural membrane

What is suprapleural membrane?

Ans: it is formed by endothoracic fascia

Attachment : internal border of 1^st rib and transverse process of C7                                                                                                                                                                                                                                                                    

2. Anterior border of the right Lung

1)1^st point-At the apex of the lung (2.5 am above the medial 1/3 of clavicle)

2)2^nd point –On the right sterno- clavicular   joint  

3) 3^rd point –Opposite the centre of the sternal   angle.

4) 4^th point-On the right end of the xiphisternal junction join these four points by a line.

3. Anterior border of   left Lung

 1)1^st   2^nd &   3^rd   point –same as those for right   lung 

2) 4^th point-On the median plane opposite the 4^th costal cartilage.

Join these four points by line. Now   the 4^th point the line goes downwards and to the left for about 1-1/2 and then curves inwards & downwards to a point on the 6^th costal cartilage 3.5cm from the median plane.

Thus, a notch is formed at the lower part of the   anterior border called the cardiac notch  

4.   Posterior border of the Right or Left Lung

Draw a vertical line downwards from a point 2 cm lateral to the 7^th cervical spine to a point 2cm lateral to the10th thoracic spine

5.   Lower border of lung:

1^st point: at xiphisternal joint

2^nd point: 6^th rib in midclavicular line

3^rd point: 8^th rib in midaxillary line

4^th point: 2 cm lateral to the 10^th thoracic spine

List of living anatomy by a point

1.    Tip of the 7^th cervical spine

2.   Tip of coracoid process

3.   sternal angle:

it correspond with lower border of 4^th thoracic vertebra

Importance:

1.    it divide superior mediastinum from inferior mediastinum

2.   it is related with 2^nd costal cartilage so we use it for counting ribs

3.    

4.   jugular notch 

5.   inferior angle of scapula