scapula, coxal bones

Step Three: Learning the Shoulder and Pelvic Bones

Overview

• Focus on understanding the anatomy of the shoulder and pelvic (coxal) bones on Day Three.
• Key structures to differentiate include the right and left scapulae.

Scapula Anatomy

• The scapula, commonly known as the shoulder blade, consists of several key components:
  • Clavicle: The collarbone that articulates with the scapula.
  • Spine: A prominent ridge on the posterior of the scapula.
  • Subscapular Fossa: The shallow depression on the anterior side of the scapula.
  • Infraspinous Fossa: The depression below the spine on the posterior side, where the infraspinatus muscle attaches.
  • Acromion: The bony process on the scapula that caps the shoulder.
  • Coracoid Process: A hook-like structure that serves as an attachment point for muscles.
  • Supraspinous Fossa: The depression above the spine on the posterior side, where the supraspinatus muscle attaches.
  • Glenoid Fossa (Cavity): The shallow cavity that articulates with the head of the humerus to form the shoulder joint.

Identifying the Scapula

• When presented with an image:
  • Anterior Side: The picture shown on the left is of the anterior side of the scapula.
  • Right or Left Scapula: The identified scapula is a right scapula.

Pelvis Anatomy

• The pelvis encompasses the coxal bones (hip bones), sacrum, and coccyx. Note that the sacrum and coccyx will be discussed along with the vertebral column on Day Four.

Coxal Bones (Hip Bones) Components:

1. Ilium:

   • Iliac Fossa: A concave surface of the ilium.
   • Iliac Crest: The curved superior border of the ilium, known as the top of the hip bone.
   • Anterior Superior Iliac Spine (ASIS): The prominent front projection of the ilium.
   • Anterior Inferior Iliac Spine (AIIS): The projection below the ASIS.
   • Greater Sciatic Notch: The notch that allows the passage of the sciatic nerve.

2. Ischium:

   • Key for weight-bearing while sitting.
   • Ischial Tuberosity: The part of the ischium that bears weight when sitting; attachment point for hamstrings.
   • Ischial Spine: A bony projection which also serves as an attachment point for muscles.

3. Pubis:

   • The front portion of the pelvis.
   • Pubic Symphysis: The fibrocartilaginous joint between the two pubic bones.
   • Ramus: The part that forms the pubic arch.

Additional Structures in Pelvis

• Acetabulum: The socket that forms the hip joint with the head of the femur; notable for its depth.
• Obturator Foramen: A large opening in the pelvis for nerves and blood vessels.
• Pubic Angle: The angle formed between the inferior rami of the pubic bones; used to identify male and female pelves.

Determining Sex of Pelvis

• To distinguish between male and female pelves, several measurements and characteristics can be analyzed:
  • Pubic Angle: If the angle exceeds 90 degrees, the pelvis is classified as female.
  • Additional female characteristics include:
  • A rounder pelvic cavity.
  • More flared ilia (hip bones).
  • A larger pelvic outlet.

Significant Bone Markings

1. Ischial Tuberosity:
   • Function: Attaches the hamstrings; bears weight when sitting.
2. Greater Sciatic Notch:
   • Function: Passage of the large sciatic nerve to the back of the leg.
3. Pubic Symphysis:
   • Type of Joint: A fibrocartilage joint between the two pubic bones.
4. Pubic Angle:
   • Use: Helps in identifying the male and female pelvises.
5. Acetabulum:
   • Function: Forms the hip joint with the head of the femur; characterized by its depth.
6. Glenoid Fossa:
   • Function: Forms the shoulder joint with the head of the humerus; characterized by its shallowness.

Components of the Acetabulum

• The acetabulum is formed by three bones:
  • Ilium
  • Ischium
  • Pubis

Tissue Type in Pubic Symphysis

• The type of tissue present in the pubic symphysis is fibrocartilage.

Identifying Male or Female Pelvis

• When presented with a pelvic image, one would identify if it is a female or male pelvis based on the previously discussed criteria.