Functions, Tissues and Classes of Bones

Functions of the Skeleton

• It supports soft tissues
• Enables movement via acting as levers for muscles
• It protects major organs
• It stores minerals
• It forms red blood cells in marrow

Bone Tissue Types

• There are two types of bone tissue: compact and cancellous
• Both types share the same material but have different structures
• Compact bone is strong and transmits force in one direction
• Cancellous bone is light and spongy and shock-absorbing
• Cancellous bone resists and channels forces from multiple directions

Bone Classes

• Long bones are longer than they are wide
• Long bones are composed of wider epiphyses and a longer, narrower diaphysis
• Long bones act as levers for movement
• Long bones have thicker compact bone in the diaphysis
• Limb bones are long bones
• Short bones have roughly equal width and length
• Short bones are mostly cancellous bone
• Short bones bear weight from multiple directions
• Carpals and tarsals are short bones
• Flat bones function in muscle attachment
• Scapulas are flat bones
• Flat bones also provide protection
• The skull and sternum are flat bones
• Flat bones consist of thin plates of compact bone with some cancellous bone
• Irregular bones do not fit into other categories
• Irregular bones have varied shapes and functions
• Irregular bones often have foramina

Divisions of the Skeleton

• The axial skeleton includes:
  • Bones of the core
  • Skull, sternum, ribs, vertebral column, sacrum, and coccyx
• The axial skeleton protects vital organs
• The appendicular skeleton includes:
  • Bones of the limbs

Axial Skeleton Details

• The skull includes:
  • Cranium, which encloses the brain and provides muscle attachments
  • Facial bones, which protect and support sensory organs
• Cranial bones join at immovable sutures
• The vertebral column supports the trunk and head
• The vertebral column has multiple muscle/ligament attachments
• The vertebral column divisions:
  • Cervical (7 vertebrae)
  • Thoracic (12 vertebrae)
  • Lumbar (5 vertebrae)
  • Sacrum and coccyx
• The rib cage (thoracic cage) includes:
  • Ribs
  • Sternum

Appendicular Skeleton Details

• The appendicular skeleton consists of the limbs
• Limb regions include:
  • Arm
  • Forearm
  • Thigh
  • Leg
• Limb structure includes:
  • A single proximal long bone in the upper and lower limb
    • Humerus/Femur
  • Two distal long bones in the upper and lower limb
    • Ulna and Radius/Tibia and Fibula
    • The ulna and radius are more mobile
  • The hands and feet
• Human skeletons are shaped the way they are because form relates to function
• Bipedalism means walking on two limbs.
• Quadrapedalism involves walking on four limbs
• The human needs to be stable as well as capable of movement
• Unlike apes, human hands are not involved in locomotion (so we have hands free)
• As a result, human hands lack stability
• hands are designed for manipulation of the environment
• The radius and ulna enable pronation and supination through the shape of their distal articulation

Appendicular attachment to Axial Skeleton

• Limbs connect limbs via girdles + exoskeleton
• Pectoral (shoulder) girdle:
  • Specializes in connection
  • Includes Clavicle (collarbone)
  • Includes Scapula (shoulder blade)
• Pelvic girdle
  • Includes Hip bones (2)
  • Includes Sacrum (axial) which attaches appendage to the core
• Clavicle (collarbone) stabilizes
• Scapula (shoulder blade) is free-moving and features muscle attachments
• Pelvic girdle consists of Os coxae (pelvic) and sacrum
• Sacrum is part of the axial skeleton
• Pelvic bones + sacrum = pelvis
• The pelvic girdle Lots of weight bearing

Sex Differences in Pelvic Anatomy

• There are multiple differences in biology based on the shape of the skeletal system
• The pelvic cavity is more circular in biological females
• The pelvic outlet is more open in biological females
• The subpubic angle is larger in biological females
• The shape of the pelvic cavity differs between biological females and males to maximize space.
• Biological females require a greater subpubic angle for childbirth.

Hands and Feet

• Hand consists of:
  • Carpals (8)
  • Metacarpals (5)
  • Phalanges (14, only 2 in the thumb)
• Foot consists of:
  • Tarsals (7)
  • Metatarsals (5)
  • Phalanges (14)