Notes on Thoracic Skeleton and Adjacent Structures

Thoracic Region Bones

• Key Bones:
  • Thoracic vertebrae: 12 in total, labeled T1-T12.
  • Ribs: 12 pairs, consisting of true ribs (1-7) and false ribs (8-12).
  • Sternum: Composed of the manubrium, body, and xiphoid process.

Floating Ribs

• Definition: The last two pairs of ribs (ribs 11 and 12) are termed floating ribs because:
  • They do not attach to the sternum directly.
  • They are only connected to the vertebrae at the back.
  • This arrangement allows for greater flexibility and movement of the ribcage during respiration.

Occipital Bone in Normal Position

• Definition: The occipital bone is located at the back of the skull and forms the base.
• Function: Protects the brain and supports the skull.
• Key Features: Contains the foramen magnum, where the spinal cord exits the skull.

Foramen Magnum

• Definition: A large opening at the base of the skull in the occipital bone.
• Function: Allows the passage of the spinal cord from the brain.

Structures Descending from Foramen Magnum

• Key Structures:
  • Spinal cord
  • Vertebral arteries
  • Accessory nerve (Cranial Nerve XI)

Intervertebral Disc

• Definition: Cartilaginous structures located between each pair of vertebrae.
• Function: Act as shock absorbers and provide cushioning for the spinal column.
• Structure: Comprised of an outer annulus fibrosus and an inner nucleus pulposus.

Trachea and Bifurcation

• Trachea Identification: A tubular structure extending from the larynx to the primary bronchi.
• Level of Bifurcation: The trachea bifurcates at approximately the level of the T5-T6 vertebrae into the left and right primary bronchi.

Covering of Spinal Cord

• Meninges: Protective coverings that consist of three layers:
  • Dura mater: The outer layer, tough and protective.
  • Arachnoid mater: The middle, web-like layer.
  • Pia mater: The inner layer that tightly adheres to the spinal cord.

Yellow and Red Color in Vertebral Column

• Description:
  • Yellow: Refers to the presence of elastic tissue in the ligamenta flava (ligaments connecting adjacent vertebrae).
  • Red: Indicates blood vessels and nerve supply within the vertebral bodies and intervertebral discs.

Femur and Tibia Identification

• Femur: The thigh bone, the longest bone in the body.
  • Key Features: Head, neck, greater and lesser trochanters.
• Tibia: The larger bone of the lower leg, also known as the shinbone.
  • Key Features: Tibial tuberosity, medial malleolus.

Epiphysis and Diaphysis

• Epiphysis: The end part of a long bone, initially growing separately from the shaft.
• Diaphysis: The shaft or central part of a long bone.

Ascending Colon and Liver

• Identification:
  • Ascending Colon: Located on the right side of the abdomen, part of the large intestine.
  • Liver: Large organ located in the upper right quadrant of the abdominal cavity, responsible for numerous metabolic processes.