Anatomy I

• Intercostal muscles lie within each intercostal
• space; there are three layers: external, internal, and innermost; they all
• attach at the inferior border of the ribs and attach at the superior border of
• the ribs below

• Ventral ramus of the spinal nerve = intercostals
• nerve. The intercostal nerve
• travels around the rib cage and sends off two primary branches: the lateral
• cutaneous branch and the anterior cutaneous branch. These branches each have two branches of their own. The lateral cutaneous branch splits
• into the anterior and posterior branches while the anterior cutaneous branch
• splits into the medial and lateral branches.

• The posterior intercostal arteries come off of
• the thoracic aorta while the anterior intercostal arteries are branches of the
• internal thoracic artery (source = subclavian a). These arteries anastamose.

• The posterior intercostals veins dump into the
• supreme intercostal vein (1) [→ brachiocephalic vein],
• superior intercostal (2, 3, and often 4) [→azygous], azygous [→
• superior vena cava] and hemiazyhous [→ azygous] veins

• Outermost layer of intercostal muscles whose fibers
• run in the same direction as your hands would when you put them in your pocket
• (anteriorly, they run medio-caudally); extend from the tubercles of the ribs in
• the back to the cartilages of the ribs in the front, and their membranes go all
• the way to the sternum; elevate ribs

• Commence at the sternum, interspaces between the
• cartilages of the true ribs, anterior extremities of the cartilages of the back
• ribs and then run back to the angles of the ribs … then the posterior intercostal
• membrane continues to the vertebral column; fibers run opposite to external; elevate
• and depress ribs

• innermost layer of intercostal muscle; probably
• depresses the ribs; fibers run in the same direction as the internal
• intercostal muscle; elevate and depress ribs

• Ventral ramus, synonymous with the intercostal
• nerve (mixed nerve with motor and sensory components)

• Supply the muscle and the skin of the posterior
• part of the trunk

• Area of the skin that is mainly supplied by a
• single spinal nerve; can be traced back to the level from which the roots
• emerge

Surface Landmarks for Internal Structures: The manubrium of the sternum meets the body of the sternum at the angle of the sternum (can be palpated), which is also the level of rib 2. The jugular notch is the top of the manubrium.

• Has two major heads – clavicular and
• sternocostal. They have origins in
• the medial half of the clavicle and the anterior surface of the sternum + the
• superior six costal cartilates as well as the aponeurosis of the external
• oblique muscle (respectively). It
• inserts on the intertubercular groove of the humerus and is innervated by the lateral
• and medial pectoral nerves. The
• blood supply comes from the pectoral branch of the thoracoacromial artery.

Found beneath the pectoralis major extending from the 3rd to 5th ribs near the costal cartilages to the medial border and superior surface of the coracoids process of the scapula. It is innervated by the medial pectoral nerve and gets blood from the pectoral branch of the thoracoacromial artery.

• innervates pectoralis major and arises from the
• lateral cord of the brachial plexus

innervates pectoralis major and pectoralis minor (enters minor and a few branches pierce into major); arises from the medial cord of the plexus

bilateral costal facets for articulation with the heads of the ribs (usually in inferior and superior pairs); costal facets on their transverse processes for articulation with the tubercles of ribs (except for inferior 2 or 3 thoracic vertebrae)

o long, inferior slanting spinous processes

• Two types: joint head of the rib and the
• costotransverse joint

• o Joint
• head of the rib: head articulates with two adjacent vertebral bodies and the
• intervertebral disc between them

• o Costotransverse
• Joint: tubercle of the rib articulates with the transverse process of the
• vertebra

• On the right side only, transports blood from the posterior walls of the thorax and abdomen into the superior vena cava; arch of azygous vein can be
• seen in right lung

On the right side only, transports blood from the posterior walls of the thorax and abdomen into the superior vena cava; arch of azygous vein can be seen in right lung

• Seen on both sides of the interior of the ribcage just
• lateral to the sternum; supplies the anterior chest wall and the breasts;
• source = subclavian artery

Drains the chest wall and the chest; seen bilaterally inside the ribcage just lateral to the sternum with the internal thoracic arteries; drain to the brachiocephalic veins

Medial mammary branches of perforating branches and the anterior intercostal branches of the internal thoracic artery; lateral thoracic and thoracoacromial arteries; posterior intercostal arteries (drained to the axillary vein and internal thoracic vein)

• Lymph passes to the subareolar lymphatic plexus →
• axillary lymph nodes (usually initially anterior or pectoral nodes) and remaining lymph goes to the parasternal lymph nodes or to the opposite breast

• Sympathetic chain/gangliated cord; paired bundle of nerve fibers that run from the base of the skull to the coccyx; interacts with spinal nerves or their roots via rami communicantes (emerge T1 → L2/3); splanchnic nerves arise
• from the trunk

• Superficial vein of the upper limb that runs along the anterior
• border of the deltoid in the deltopectoral groove (through deltopectoral
• triangle); empties into axillary vein

• Bilateral vein that is a continuation of the axillary vein (renamed
• at the outer border of the first rib); continues to the medial border of the
• anterior scalene muscle where it meets the internal jugular vein to form the
• brachiocephalic vein

“breast bone”; long flat bone shaped like a “T” with three main parts: manubrium, body, and xiphoid; articulates with the clavicle and the upper 7 costal cartilages

• Uppermost portion of the sternum; jugular notch lies on top with oval articular
• surfaces upweard, backward, and more lateral of the notch for articulation with
• the clavicle; continues down to the sterna angle

• Small cartilaginous extension on the lower part of the sternum (usually
• ossified in adults); forms fibrous joint with the body of the sternum; only
• bottom of 7th rib articulates

• Palpable angle found between the manubrium and body
• of the sternum

Found at the superior border of the manubrium between the clavicular notches

• Notches on the sternum found where the costal
• cartilages articulate with the sternum (sternocostal joints)

• saddle type of synovial joint that connects the sterna end of the
• clavicle with the manubrium of the sternum and the first costal cartilage;
• divided into two compartments by an articular disc

• 1-7, articulate directly with the sternum
• (via costal cartilage)

• Ribs 8-12; 8-10 have costal cartilages that connect
• with the costal cartilage of rib 7 while 11 and 12 are floating ribs

• Ribs 11 and 12; do not connect to the sternum or
• other ribs (only vertebral joint)

• Prolong the ribs anteriorly and contribute to
• the elasticity of the thoracic wall

• o Costal
• cartilages of ribs 1 – 10 anchor ribs to sternum (directly or indirectly)

• o Costal
• cartilages of 11 and 12 are essentially caps

Superior thoracic aperture; bound by vertebra T1, 1st pair of ribs, and superior border of the manubrium; trachea, esophagus, nerves, and vessels that supply and drain the head, neck, and upper limbs travel through

Inferior thoracic aperture; bounded by T12, 11th and 12th pairs of ribs, joined costal cartilages of 7-10, and xiphisternal joint; closed by the diaphragm → structures passing to/o the abdomen must pass through openings that traverse the diaphragm (esophagus and inf vena cava) or posterior to it (aorta)

Inferior margin of the lowest costal cartilages and ribs

The head articulates with the body of the vertebrae while the tubercle articulates with the transverse process of the vertebrae.

· Jugular notch: Medial position on the rostral edge of the manubrium; T2

· Sternal Angle: Where the manubrium and body of the sternum meet; T4/5 and 2nd rib

· Nipple: 4th intercostal space and left ventricle

· Xiphoid Process: Caudal-most piece of the sternum; T10

• Origin = lower border of the ribs;
• Insertion = upper border of the ribs below
• Innervation = Intercostal nerves
• for all three layers

• Outermost layer of intercostal muscles whose fibers run in the same direction
• as your hands would when you put them in your pocket (anteriorly, they run
• medio-caudally); extend from the tubercles of the ribs in the back to the
• cartilages of the ribs in the front, and their membranes go all the way to the
• sternum; bloody supply = intercostal arteries

• o Action:
• Elevate ribs during forced inspiration

Commence at the sternum in the interspaces between the cartilages of the true ribs, anterior extremities of the cartilages of the back ribs and then run back to the angles of the ribs … then the posterior intercostal membrane continues to the vertebral column; fibers run opposite to external; blood supply = intercostal arteries supply

• o Action:
• Interosseous part depresses ribs and the interchondral part elevates ribs
• during forced respiration

• innermost layer of intercostal muscle; fibers
• run in the same direction as the internal intercostal muscle

• o Action:
• Interosseous part depresses ribs and the interchondral part elevates ribs
• during forced respiration

In addition to the three layers of muscle, a bundle of nerve + artery + vein runs at the inferior border of the ribs. The nerve is the intercostal nerve, which is the ventral ramus of the thoracic spinal nerve, and it runs around the interior of the rib cage sending off cutaneous branches. The arteries are the anterior and posterior intercostal arteries (branches of the thoracic aorta and anterior thoracic arteries respectively) which anastamose laterally. The veins are anterior and posterior intercostal veins which dump into the interior thoracic veins and the azygous/hemiazygous/accessory hemiazygous veins respectively.

• Thoracic spinal nerves split into dorsal rami (innervate the muscles of the back) and ventral rami (innervate the rib cage and area surrounding it).
• Dermatomes correspond to the innervation by a specific spinal nerve.

Latiferous ducts lie beneath the areola and extend to gland lobules which comprise the bulk of the breast along with fat. The mammary gland is firmly attached to the dermis of the overlying skin by the suspensory ligaments. It extends on a bed that extends from the lateral border of the sternum to the midaxillary line and vertically from the 2nd through 6th ribs.