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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.
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