Thoracic Cage and Diaphragm Anatomy

A thin layer of loose connective tissue found deep to the intercostal spaces, containing variable amounts of fat, that separates the ribs and intercostal spaces from the underlying pleura.

These muscles are located between the ribs, filling and supporting the intercostal spaces. They play a crucial role in breathing.

This muscle lies deep to the internal intercostals and helps to further depress the ribs during forced expiration.

This muscle runs obliquely, crossing multiple ribs and helps to depress the costal cartilages, aiding in forced expiration.

These muscles help to elevate the ribs during inspiration, increasing the volume of the thoracic cavity and helping to draw air into the lungs.

These muscles help to depress the ribs during forced expiration, decreasing the volume of the thoracic cavity and forcing air out of the lungs.

These muscles help to depress the ribs, aiding in forced expiration.

These muscles, along with the intercostal muscles, alter the position of the ribs and sternum, ultimately changing the volume of the thoracic cavity and affecting breathing.

These muscles provide structural support for the intercostal spaces, helping to maintain the shape of the rib cage during breathing.

The intercostal muscles are supplied by the intercostal nerves.

The external intercostal muscles help with inhalation by lifting the ribs upwards and outwards.

The internal intercostal muscles can help with exhalation by pulling the ribs downwards and inwards, but their primary role is stabilization during breathing.

Arteries that supply the spaces between the ribs, originating from the aorta and internal thoracic artery.

The main artery that supplies blood to the chest cavity.

A large artery in the chest that branches off from the subclavian artery, providing blood to the chest wall and other structures.

The upper two posterior intercostal arteries on each side, originating from the costocervical trunk in the neck.

The main artery that supplies blood to the shoulder and neck.

A branch of the subclavian artery that contributes to the blood supply of the neck and shoulders.

The anterior intercostal arteries that supply the upper six intercostal spaces originate as lateral branches from the internal thoracic artery. The lower intercostal spaces are supplied by the musculophrenic artery.

The anterior intercostal arteries typically branch into two, one passing below the upper rib's margin, and the other passing above the lower rib's margin, meeting with a branch from the posterior intercostal artery.

The anterior and posterior intercostal vessels overlap and can connect through anastomoses, providing alternative pathways for blood flow.

Anterior intercostal arteries are generally smaller than the posterior intercostal vessels.

The superior epigastric artery, a continuation of the internal thoracic artery, goes through the diaphragm and ends near the last intercostal space.

Venous drainage from the thoracic wall generally follows the pattern of arterial supply.

The intercostal veins drain into the azygos system, eventually connecting to the brachiocephalic veins in the neck.

The internal thoracic vein drains into the brachiocephalic veins in the neck.

The subcostal nerve (T12) is located below the 12th rib, while typical intercostal nerves run between the ribs.

The lateral cutaneous branch is the largest branch of an intercostal nerve. It divides into an anterior branch and a posterior branch that innervate the skin.

The intercostal nerves end as anterior cutaneous branches, supplying the skin of the anterior chest and abdominal wall.

Intercostal nerves provide motor innervation to the intercostal, subcostal, and transversus thoracis muscles.

Intercostal nerves provide sensory innervation to the skin and parietal pleura, the lining of the chest cavity.

Intercostal nerves carry postganglionic sympathetic fibers, contributing to the autonomic nervous system.

The anterior ramus of T1 contributes to the brachial plexus, which innervates the upper limb.

The intercostobrachial nerve, a branch of the second intercostal nerve, innervates the medial surface of the upper arm.

The inferior vena cava (IVC) passes through the central tendon of the diaphragm, at approximately vertebral level TVIII.

The esophagus, carrying food from the mouth to the stomach, passes through the muscular part of the diaphragm just to the left of the midline, at about vertebral level TX.

The aorta, the largest artery in the body, passes behind the posterior attachment of the diaphragm, at vertebral level TXII.

The thoracic duct, which transports lymph fluid, passes behind the diaphragm with the aorta.

The phrenic nerves (C3, C4, and C5) innervate the diaphragm, controlling its contraction and relaxation.

When the diaphragm contracts, its domes flatten, increasing the volume of the thoracic cavity and causing inhalation.

Diaphragmatic paralysis, or weakness, occurs when the phrenic nerves are damaged, often due to lung cancer or other medical conditions.

Common causes of phrenic nerve palsy, besides lung cancer, include postviral neuropathy, trauma, surgical injury, and degenerative changes in the cervical spine.