Aortic sinus

L

Arch
of aorta

   Origin: It
is the continuation of ascending aorta and end as descending thoracic  

    aorta.

   Branches:
right to left

       1.   Brachiocephalic trunk : sub branch:

   Lateral
to medial:

       a)   right subclavian artery

       b)  right common carotid artery

      2.   Left common carotid artery

       3.   Left subclavian artery

 

Descending
thoracic aorta

  Origin: It is the continuation of arch of aorta and ends as abdominal aorta.

   Branches:

 Unpaired artery:  Ventral branches

     1.   Left bronchial artery directly arises from aorta but right bronchial
artery arises from 3^rd posterior intercostal artery which is the
branch of aorta

      2.  Mediastinal arteries : supply connective tissue of posterior mediastinum

      3.  Esophageal arteries :  they are unpaired arteries
arising from ventral surface of aorta

      4.  Pericardial arteries : Small unpaired arteries that arise
  anteriorly to supply the dorsal portion of the pericardium

Paired arteries

        1.   
Superior phrenic arteries: Paired
parietal branches that supply the superior portion of the diaphragm.
Inferior phrenic arteries are the 1^st branch of abdominal aorta 

       2.   3^rd to 11^th Posterior intercostal arteries: The 1^st and 2^nd   posterior intercostal arteries originate from the
  superior (supreme) intercostal artery, a branch
   of the costocervical trunk.

       3. Subcostal arteries 

Subclavian arteries

Origin:

Right subclavian arteries	Left subclavian arteries
It is the branch of brachiocephalic trunk / artery which is the branch of arch of aorta	It is the direct branch of arch of aorta

 

They become axillary arteries when they enter axilla, then they continued as brachial arteries and supply upper limbs.

 

Branches of subclavian arteries

1.   the vertebral artery,

2.   the internal thoracic artery,

3.   the thyrocervical trunk,

4.   the costocervical trunk, and

5.   the dorsal scapular artery

 

Part	Branches	Small branches
First part From its origin to the medial border of scalenus anterior	Vertebral artery	It  forms the basilar artery
	Internal thoracic artery	It giving off  ·       anterior intercostal branches, ·       perforating vessels to the breast and ·       terminating in ·       superior epigastric artery and the musculophrenic artery.
	Thyrocervical trunk	It gives off following branches ·       inferior thyroid artery,  ·       suprascapular artery and ·       transverse cervical artery (also called cervicodorsal trunk)
Second part Lying behind scalenus anterior	Costocervical trunk	Splits into  ·       superior intercostal artery and  ·       deep cervical artery
Third part Between the lateral border of scalenus anterior and the outer border of the 1st rib	Dorsal scapular artery	From either second or third part. Passes backwards to supply levator scapulae and rhomboids.

 

Internal thoracic artery

 

Origin : From the first part of the subclavian artery

Branches :

1.   1^st to 6^th Anterior intercostal arteries , 

2.   Perforating and 

3.   Sternal branches

4.   Terminal branches :  

•        Musculophrenic artery : 7^th to 9^th anterior intercostal arteries arises from it

•        Superior epigastric arteries: It anastomoses with the inferior epigastric artery within the rectus abdominis muscle at the umbilicus

 

 

Intercostal arteries

	Anterior intercostal arteries	Posterior intercostal arteries
Number	9	11
Main artery	Mainly internal thoracic artery	Mainly descending thoracic aorta
Origin	•        1st to 6th Anterior intercostal arteries:  arises from internal thoracic artery •         7th to 9th Anterior intercostal arteries:  arises from Musculo-phrenic artery	•        1st & 2nd posterior intercostal arteries:  arises from superior intercostal artery & •        3rd & 11th posterior intercostal arteries: arises from descending thoracic aorta

Anterior intercostal arteries

•        1^st to 6^th Anterior intercostal arteries:  arises from internal thoracic artery

•         7^th to 9^th Anterior intercostal arteries:  arises from Musculo-phrenic artery

Posterior intercostal arteries

·       1^st & 2^nd posterior intercostal arteries:  arises from superior intercostal artery &

·       3^rd & 11^th posterior intercostal arteries: arises from descending thoracic aorta

Veins of thorax

Superior vena cava

 

Formation:

 It is form by the union of the right and left brachiocephalic veins.

Tributaries:

 Azygous vein.

Minor veins:

·       Mediastinal veins,

·       Pericardial veins and

·       Oesophageal veins.

  Right and left brachiocephalic veins

 

Formation: it is formed by internal jugular vein and subclavian vein

 

Topics	Right brachiocephalic vein	Left brachiocephalic vein
Size	Short	Longer
Why short?	SVC is situated in right side of body so right vein is short	Svc is in right so it need to cross a long distance to form SVC
Tributaries	·       Right vertebral, ·       internal thoracic and ·       inferior thyroid veins, and ·       occasionally,  the right posterior intercostal vein of the 1st intercostal space.	·       left vertebral, ·       internal thoracic, ·       inferior thyroid and ·       superior intercostal veins. ·        In addition, the thymic, supreme intercostal, pericardiacophrenic and the left posterior intercostal vein of the 1st intercostal space.
Drainage of Lymphatic vessels	Right lymphatic duct near the junction of the left subclavian and left internal jugular veins.	the thoracic duct terminates in the internal jugular vein, the subclavian vein, or the angle between the two

 

Clinical Relevance: Jugular Venous Pressure

The superior vena cava is a valveless structure. This allows the pressure in the right atrium to be conducted upwards into the right internal jugular vein.

Visualisation of the right internal jugular vein is an indicator of the jugular venous pressure – which in turn represents the pressure in the right atrium.  To examine, the patient should be at a 45° angle with their head turned slightly to the left. The JVP can be identified as a pulsation between the two heads of the sternocleidomastoid muscle.

Causes of a raised JVP include right-sided heart failure, pulmonary hypertension, and SVC obstruction.

 

The superior vena cava is classified as a large vein, with a wide diameter of up to 2cm and a length of approximately 7cm.

It arises from the union of the left and right brachiocephalic veins, posterior to the first right costal cartilage. It descends vertically through the superior mediastinum, behind the intercostal spaces and to the right of the aorta and trachea.