Introduction of Skeletal System lectures chpt 6

Sep 15, 2024

Skeletal System Overview

Main Components

  • Axial Skeleton: Includes skull, mandible, vertebral column, thoracic cage, and hyoid bone.
  • Appendicular Skeleton: Includes pectoral girdle, upper and lower appendages, and pelvic girdle.
  • Total Bones in Adults: Approximately 206 bones.

Types of Bones

  • Long Bones: Longer than they are wide.
  • Short Bones: Compact shape, relatively equal on all sides.
  • Flat Bones: Thin, broad (e.g., sternum, scapula, parietal bones).
  • Irregular Bones: No particular shape (e.g., vertebrae, ethmoid, zygomatic).
  • Sesamoid Bones: Sesame seed shape (e.g., patella, pisiform).

Bone Composition

  • Two Types: Spongy Bone and Compact Bone.
    • Compact Bone: Dense, made of osteons, contains lamella, lacuna, osteocytes.
    • Spongy Bone: Porous, made of trabecula, similar components as compact bone but lacks reversion canal.

Bone Cells

  • Osteogenic Cells: Precursor cells that develop into osteoblasts.
  • Osteoblasts: Secrete bone matrix, form osteocytes when isolated.
  • Osteocytes: Maintain bone tissue, isolated in lacuna.
  • Osteoclasts: Break down bone, derived from bone marrow.

Bone Matrix

  • Composition: Organic (collagen fibers, elastic, and reticular fibers) and Inorganic (calcium phosphorus salts, hydroxyapatite).
  • Collagen: Provides flexibility and strength.
  • Calcium Salts: Crystallize on collagen, provide hardness.
  • Hydroxyapatite: Combination of calcium salts.

Forces Acting on Bone

  • Tensile Force: Ability to be slightly stretched.
  • Compressional Force: Ability to be compressed.
  • Torsional Force: Allows slight twisting.

Summary

  • Bone structure and composition provide strength and flexibility.
  • Osteons and trabeculae contribute to the structural integrity.
  • Bone cells have specific roles in formation, maintenance, and breakdown of bone.
  • The combination of collagen and calcium salts creates a balance of rigidity and slight flexibility.