Thoracic Skeleton Anatomy

• The concept covers the skeleton of the thorax and the breast.

Structure of the Thoracic Skeleton

• The Thoracic Skeleton is OSTEOCARTILAGINOUS.
• It's made of Bone
  • Includes 12 thoracic vertebrae.
  • Includes 12 pairs of ribs.
  • Includes the Sternum
• Also has Cartilage:
  • Features 10 pairs of costal cartilages, but the last 2 rib pairs do not have costal cartilages
  • Includes Hyaline cartilage
• Cartilage joints give the thoracic skeleton flexibility and slight movement during breathing.

Sternum

• The sternum is divided into three sections.
• The first section is the Manubrium
  • This features a Superior joint with clavicles
  • A Lateral joint with costal cartilages of Rib 1.
  • and an Inferior joint with the body of the sternum and part of the second costal cartilages.
  • It has a Sternal (jugular) notch; blood pulsing through the aorta can be seen above the notch if exercising heavily, if its valve doesn't function properly or if its diameter is too small.
  • Also contains the Sternal angle, which is where the manubrium and body meet and is a clinical marker for the second rib; the 2nd intercostal space is the location of 2 major heart valves.
• The second section is the Body
• The third section is the Xiphoid process

Clinical Importance

• Locating the 2nd rib is important as the sternal angle helps locate the 2nd rib.
• Use of a stethoscope to listen to heart valves closing requires placement at the location of the four yellow circles.
• Actual valve positions are the blue ovals.
• Two valves are heard in the second intercostal space.

Structure of Bony Thorax

• The sternum is divided into 3 sections.
• First is the Manubrium.
• Second is the body
  • This area is Inferior to sternal angle
  • Where the body Forms joints laterally with costal cartilages on ribs 2-7.
  • The joint inferiorly forms with the xiphoid process.
• Third is the Xiphoid process
  • The Xiphoid process is the Most inferior section of the sternum
  • Is a Clinical marker for the superior liver surface and the apex (tip) of the heart

Types of Ribs

• There are three types of ribs
• First is the Vertebrosternal (vertebrocostal) : Ribs 1-7 also called "true ribs"
  • Each directly attaches to the sternum via its costal (rib) cartilage.
• Second is the Vertebrochondral: Ribs 8-10
  • These All attach to rib 7 by an elongated cartilage (chondros =cartilage) and have no direct connection to the sternum.
• Third is the Vertebral (floating ribs): Ribs 11 and 12
  • Have no sternal attachment; end in muscles of the lower lumbar area

Structure of a Typical Rib

• Ribs 3-9 are typical ribs and have these features.
• They include a Head: which forms joints with thoracic vertebral bodies and has flattened articular facets
• They also include a Neck: between the head and tubercle
• And also a Tubercle which forms joints with transverse processes of vertebrae on ribs 1-10
• The rib ends twist such that ribs slant inferiorlaterally
• They also contain a Costal groove which is the location of the costal Vein-Artery-Nerve (VAN)
• and have an Angle: where the rib travels laterally, then anteriorly

Posterior Rib Joints

• All ribs form joints with their respective vertebral bodies.
• The Articular facet on the head of a ribs forms a facet joint with costal facets of the vertebral body
• Rib 1 and Ribs 10-12 only have one costal facet on their heads and they each form a facet joint of rib only with its respective vertebral body.
• Ribs 2-9 have superior and inferior articular facets.
• Thoracic vertebral bodies 1-9 have superior/inferior costal facets
  • Small sizes of facets are called demifacets
• Ribs 2-9 form joints with their respective vertebral bodies the body of the vertebra
• Ribs 1-10 have a tubercle
  • Tubercles form joints laterally with transverse costal facets

Anterior Rib Joints

• Ribs 1-10 have costal cartilages (hyaline cartilage)
• Costal cartilages of vertebrosternal ribs (1-7) attach rib ends to the sternum.
• Costal cartilages of vertebrochondral ribs (8-10) attach rib ends to rib 7.

Rib 9 Joints

• Rib 9 features costal facets on the head of Rib 9 that attach to demifacets of T9 and T8
• Also the Tubercle of Rib 9 attaches to the transverse costal facet of T9
• Note the anterior end of Rib 9 twists laterally

Atypical Ribs

• Rib 1 is flattened and the shortest rib
• It has grooves subclavian vessels on its superior surface
• It also forms joints with the T1 vertebral body and the T1 transverse costal facet -Is directly inferior and posterior to the clavicle
• Ribs 11 and 12
  • Have Single facets on their heads
  • Have No tubercles
  • Each has a single joint with their respective vertebral bodies.

The Human Breast

• Breasts are found in both genders but are only functional in females men can and do develop breast cancer and should do periodic self exams.
• Found on the fascia covering the pectoralis major muscle.
• The Breast is a Modified apocrine sweat gland
  • Similar to sweat glands in the axilla and genital areas
  • Milk-secreting cells are in lobules -Small oval structures lined with secretory cells
• Drained by a lactiferous duct that empties into a lactiferous sinus just deep to the nipple
• Usually 15-20 lobules in each breast, organized into lobes

Support & Structure

• Breast Support Structure: Surrounded by adipose; supported from skin and fascia by suspensory ligaments
• Areola = darkly pigmented ring of skin surrounding nipple; contains numerous areolar glands that lubricate nipple during lactation
• Breast is arranged into 4 quadrants: Upper outer and inner quadrants and Lower outer and inner quadrants
• Axillary Tail: extension into the axilla

Human Breast Blood and Lymphatic Supply

• Blood supply Internal thoracic arterylateral thoracic artery
• Lymphatic drainage: Axillary lymph nodes (to clavicular and cervical) Parasternal- lymph nodes

Human Breast Cancer

• Usually begins in cells of lobules or lactiferous sinuses.
• Has Varying Signs and symptoms: such as a Painless lump or thickening in breast, found by self-examination or screening mammography, Painful lump, Swelling, puckering, or redness of skin, Bloody discharge from nipple, Changes to size, shape or skin appearance and sometimes an Inverted nipple Lymphatic drainage of breast is primarily to nodes at end of axillary tail
• Cancer cells may spread by breaking free of the tumor and traveling here, cancer cells may also spread to parasternal nodes and cross to opposite breast
• Cancer cell spread is called metastasis
  • Sentinal lymph node = first node in chain of lymph nodes draining breast
  • If surgically removed and free of cancer, patient may have no metastasis
  • Additional nodes might (or might not) be removed during breast cancer surgery
• More conservative surgery reduces