Intercostal Arteries

Arteries enter intercostal spaces at the back and front
Posterior
- Back upper 2 spaces: Supplied by the Superior intercostal artery, i.e. the descending branch of the Costocervical Trunk (from the 2nd part of the Subclavian Artery behind Scalenus Anterior)
  - Enters thorax by passing across the front of the neck of 1st rib
    - Relations here: Medial side: Sympathetic Trunk; Lateral side: 1st Thoracic nerve passes across 1st rib to join Brachial plexus
      - Small 1st Posterior Intercostal Vein lies between artery and Sympathetic Trunk
  - Here: 1st Thoracic Sympathetic Ganglion frequently fused with Inferior Cervical Ganglion to form the Cervicothoracic (Stellate) Ganglion
- Remaining 9 spaces: Supplied by separate branch of Descending Thoracic Aorta
- Branches cross the front of the vertebrae and Anterior Longitudinal Ligaments, behind the Hemiazygous Veins and Thoracic Duct
- All 11 arteries = Posterior Intercostal Arteries
- Each artery gives off small collateral branch – passes around neurovascular plane at a lower level than the main trunk
Anterior
- At the front: Internal thoracic artery in the upper 6 spaces and the Musculophrenic Artery in the 7-9th spaces give off 2 Anterior Intercostal Arteries ⇒ Pass backwards and anastomose with Posterior vessels
  - No anterior intercostal spaces in the last 2 spaces

Intercostal Veins

In each space: 1 Posterior and 2 Anterior Intercostal Veins
Anterior Intercostal Veins:
- Drain into Musculophrenic and Internal Thoracic Veins
Posterior Intercostal Veins:
- Supreme Intercostal Vein - 1st Posterior Intercostal Vein ⇒ Drains either into the Vertebral Vein or the Brachiocephalic Vein on its own side
- Superior intercostal vein - 2nd and 3rd (and sometimes 4th) Posterior Intercostal Vein ⇒ Form a single trunk on each side (Superior Intercostal Vein) ⇒ On the right, drains into the Azygos vein; On the left, runs forward over Arch of Aorta, Lateral to Vagus Nerve and medial to Phrenic Nerve and empties into Left Brachiocephalic Vein
- Azygos Vein and Hemiazygos Veins
  - In lower 8 spaces ⇒ Drain into Azygous system: Azygos Vein on the right and the Hemiazygos and Accessory Hemiazygos Veins on the left

From 1st part of the Subclavian Artery
Passes vertically downwards about 1cm lateral to sternal border
Gives off 2 Anterior Intercostal Arteries in each intercostal space
At costal margin, it divides into the Superior Epigastric Artery and the Musculophrenic Arteries
- Superior Epigastric Artery:
  - Passes between xiphisternal and highest costal fibres of the diaphragm to enter the Rectus Sheath behind the muscle
- Musculophrenic Artery:
  - Passes along the costodiaphragmatic gutter and gives off 2 Anterior Intercostal Arteries in each space until it ends by piercing the diaphragm in the 9th space to ramify on its abdominal surface
Internal Thoracic Artery – accompanied by 2 venae comitantes that empty into the Brachiocephalic Vein

Origin: Formed by the union of the Right Ascending Lumbar Vein and Right Subcostal Vein
Travels through the Aortic Opening under shelter of Right Crus
- Lateral to the Thoracic Duct
Passes upwards lying on the sides of the Vertebral bodies on a plane posterior to that of the Oesophagus
Termination: Superior Vena Cava
- At level of T4
- Azygos Vein arches forwards over the Hilum of the Right lung
Receives blood from:
- Lower 8 Posterior Intercostal Veins of the Right Side
- Superior Intercostal Vein
- Bronchial veins from the Right Lung
- Pericardial Veins
- Veins from the Middle third of the Oesophagus
Two Hemiazygos Veins usually join it at the levels of T7 and T8

Two veins
Lie longitudinally on the left side of the bodies of the Thoracic Vertebrae
Communicate with each other
- BUT characteristically drain separately from their adjoining ends behind the Oesophagus into the Azygos Vein
Receive blood from:
- Lower 8 Posterior Intercostal Vein of the Left Side (4 each)
Inferior vein, a.k.a. Hemiazygos Vein, formed in the abdomen by the union of the Left Ascending Lumbar Vein and the Left Subcostal Vein
- Often communicates with the Left Renal Vein
- Passes up through the Left Crus of the Diaphragm
- Receives blood from the lower Oesophagus
Superior vein, a.k.a. Accessory Hemiazygos Vein, receives Bronchial veins from the Left Lung

Commences at lower border of T4 where Arch of Aorta ends
Initially to the left of midline
Slants gradually to the midline
Leaves Posterior Mediastinum at the level of T12 by passing behind the Diaphragm between the Crura, i.e. behind the Median Arcuate Ligament
Branches:
- 9 x pairs of Posterior Intercostal Arteries
- 1 x pair of Subcostal Arteries
- Bronchial Arteries
- Oesophageal Arteries
- Few small Pericardial and Phrenic Branches

Overview

Formed behind the Sternoclavicular Joints by confluence of Internal Jugular and Subclavian Veins
Medial to the Anterior Scalene, located anterior to the Subclavian Artery (1st part) and receives tributaries corresponding to the branches of the 1st part of Subclavian – i.e. Vertebral, Inferior Thyroid, Internal Thoracic, Supreme Intercostal Vein and Superior intercostal vein (on left hand side only)

Right Brachiocephalic Vein

Commences behind the right Sternoclavicular Joint
Receives at its commencement: Right Jugular, Subclavian, Bronchomediastinal lymph trunks separately or via their confluent channel, the Right Lymphatic Duct

Left Brachiocephalic Vein

Passes to the right with a downward inclination across the Superior Mediastinum
Passes above the Arch of the Aorta
Passes posterior to the Thymus and the Upper ½ of the Manubrium
At its commencement, receives the Thoracic Duct
Receives most of the Inferior Thyroid Veins, Left Superior Intercostal Vein, and the large Thymic Vein

Commences at lower border of the 1st Right Costal Cartilage by confluence of the two Brachiocephalic Veins
Passes vertically downwards behind the right border of the Sternum
Pierces the Pericardium at the level of the 2nd Costal Cartilage
Enters the Upper border of the Right Atrium at the lower border of the 3rd Right Costal Cartilage
Receives the Azygos Vein behind the Sternal Angle and the right Superior intercostal vein
No valves in the SVC, Brachiocephalic Vein, or Azygos Vein systems