Intercostal Arteries and Veins Overview

Intercostal Arteries and Veins

• Each intercostal space has one large posterior intercostal artery and two small anterior intercostal arteries.
• The posterior intercostal arteries in the first two spaces branch off from the superior intercostal artery, a branch of the costocervical trunk of the subclavian artery.
• The posterior intercostal arteries in lower nine spaces branch from the descending thoracic aorta.
• The anterior intercostal arteries in the first six spaces branch from the internal thoracic artery.
• The anterior intercostal arteries in lower spaces branch from the musculophrenic artery, a terminal branch of the internal thoracic artery.
• Each intercostal artery branches to muscles, skin, and parietal pleura.
• Posterior intercostal veins drain backward into the azygos or hemiazygos veins.
• Anterior intercostal veins drain forward into the internal thoracic and musculophrenic veins.

Intercostal Nerves

• The intercostal nerves are the anterior rami of the first eleven thoracic spinal nerves.
• The twelfth thoracic nerve is the subcostal nerve.
• Each intercostal nerve enters an intercostal space between the parietal pleura and the posterior intercostal membrane.
• It runs forward inferiorly beside the intercostal vessels in the subcostal groove.
• The first six intercostal nerves remain within their intercostal spaces.
• The seventh through ninth nerves exit their intercostal spaces and enter the anterior abdominal wall.
• The tenth and eleventh nerves pass directly into the abdomen.
• Rami communicantes connect the intercostal nerves to the sympathetic trunk.
• Collateral branches run forward inferiorly.
• Lateral cutaneous branches reach the skin of the chest.
• Anterior cutaneous branches reach the anterior skin, dividing into medial and lateral branches.
• Each nerve also has muscular and pleural sensory branches.
• The first intercostal nerve joins the brachial plexus.
• The second intercostal nerve joins the medial cutaneous nerve.
• They supply the skin, parietal pleura and the intercostal muscles.

Suprapleural Membrane

• The suprapleural membrane is a dense layer that closes the thoracic outlet.
• It is tent-shaped, fibrous sheet attached laterally to the first ribs and medially to the seventh cervical vertebrae.
• It protects the cervical pleura.
• It resists intra-thoracic pressure changes during respiration.

Diaphragm

• The diaphragm is the primary muscle of respiration, dome-shaped with a central tendon.
• It has three parts: sternal, costal, and vertebral parts.
• The right crus arises from the bodies of the first three lumbar vertebrae.
• The left crus arises from the bodies of the first two lumbar vertebrae.
• Lateral and medial arcuate ligaments attach to the crura, lateral to the crura is the diaphragm.
• The diaphragm is inserted into the central tendon, which is fused with the inferior surface of the fibrous pericardium.
• Muscles surrounding the esophageal opening act as a sphincter preventing regurgitation.
• The diaphragm's shape varies with posture.
• The diaphragm has three openings: aortic, esophageal, and caval.

Openings in the Diaphragm

• Aortic Opening: Anterior to the body of the 12th thoracic vertebrae between the crura, transmits the aorta, thoracic duct, and azygos vein.
• Esophageal Opening: At the level of the 10th thoracic vertebra in a sling of muscle fibers, transmits the esophagus, right and left vagus nerves, and lymphatics.
• Caval Opening: At the level of the 8th thoracic vertebrae in the central tendon, transmits the inferior vena cava and terminal branches of the right phrenic nerve.

Other Openings

• The greater, lesser, and lowest splanchnic nerves pierce the crura.
• Sympathetic trunks pass posterior to the medial arcuate ligament.
• Superior epigastric vessels pass between the sternal and costal origins of the diaphragm.
• The left phrenic nerve pierces the left dome.
• Intercostal nerves pass to the anterior abdominal wall between diaphragm origins.

Lets Check Your Knowledge Questions

Different questions and possible answers relating to the above sections are mentioned in the provided text.

This quiz focuses on the anatomy of intercostal arteries and veins, detailing their origins, branches, and functions within the thoracic cavity. It covers the posterior and anterior intercostal arteries, their respective sources, and where they drain. Test your understanding of these vital structures in the respiratory system.