Anatomy & Physiology
Chapter 3: The Skeletal System
Unit 1: Structure and Classification of Bones
Types of Bone Tissue
o Compact bone (Cortical bone): Strongest bone; supports,
protects, enables movement.
o Cancellous bone (Spongy/trabecular bone): Found at long
bone ends, pelvis, ribs, skull, spine.
o Woven bone: Temporary bone that forms during fracture repair.
Structure of Compact Bone
o Periosteum: Fibrous outer layer; contains osteoblasts that build
bone matrix.
o Osteon (Haversian system): Central canal surrounded by
concentric lamellae with lacunae (spaces for bone cells).
Types of Bone Marrow
o Red marrow: Hematopoiesis (produces blood cells); found
in skull, pelvis, spine, sternum, long bones.
o Yellow marrow: Fat-rich; contributes to bone/cartilage
formation; found in long bones.
Bone Classifications by Shape
o Long bones: Femur, tibia, humerus. Key parts: diaphysis,
epiphysis, metaphysis, medullary cavity, articular cartilage,
periosteum, endosteum.
o Short bones: Wrists, ankles; support/stability.
o Flat bones: Skull, chest, pelvis; protect organs.
o Sesamoid bones: Embedded in tendons (e.g., patella).
, o Irregular bones: Complex shapes (e.g., vertebrae, jaw).
Unit 2: Process of Osteogenesis
Bone-Forming Cells
o Mesenchymal cells: Stem cells; give rise to all connective
tissues.
o Osteoblasts: Build bone; secrete osteoid.
o Osteocytes: Mature bone cells in lacunae.
o Osteoclasts: Break down bone for remodeling.
o Cartilage cells: Involved in endochondral ossification.
Bone Formation Types
o Intramembranous ossification: Bone develops directly
from mesenchyme (e.g., skull bones).
o Endochondral ossification: Bone replaces cartilage
model (e.g., long bones).
Hormones Affecting Bone Growth
o Growth hormone + IGF-I: Promote bone growth.
o Vitamin D: Aids calcium absorption.
o Calcitonin: Lowers blood calcium.
o Parathyroid hormone: Raises blood calcium.
Unit 3: Major Bones and Bony Landmarks
Axial Skeleton
o Includes: Skull, vertebral column, rib cage.
Chapter 3: The Skeletal System
Unit 1: Structure and Classification of Bones
Types of Bone Tissue
o Compact bone (Cortical bone): Strongest bone; supports,
protects, enables movement.
o Cancellous bone (Spongy/trabecular bone): Found at long
bone ends, pelvis, ribs, skull, spine.
o Woven bone: Temporary bone that forms during fracture repair.
Structure of Compact Bone
o Periosteum: Fibrous outer layer; contains osteoblasts that build
bone matrix.
o Osteon (Haversian system): Central canal surrounded by
concentric lamellae with lacunae (spaces for bone cells).
Types of Bone Marrow
o Red marrow: Hematopoiesis (produces blood cells); found
in skull, pelvis, spine, sternum, long bones.
o Yellow marrow: Fat-rich; contributes to bone/cartilage
formation; found in long bones.
Bone Classifications by Shape
o Long bones: Femur, tibia, humerus. Key parts: diaphysis,
epiphysis, metaphysis, medullary cavity, articular cartilage,
periosteum, endosteum.
o Short bones: Wrists, ankles; support/stability.
o Flat bones: Skull, chest, pelvis; protect organs.
o Sesamoid bones: Embedded in tendons (e.g., patella).
, o Irregular bones: Complex shapes (e.g., vertebrae, jaw).
Unit 2: Process of Osteogenesis
Bone-Forming Cells
o Mesenchymal cells: Stem cells; give rise to all connective
tissues.
o Osteoblasts: Build bone; secrete osteoid.
o Osteocytes: Mature bone cells in lacunae.
o Osteoclasts: Break down bone for remodeling.
o Cartilage cells: Involved in endochondral ossification.
Bone Formation Types
o Intramembranous ossification: Bone develops directly
from mesenchyme (e.g., skull bones).
o Endochondral ossification: Bone replaces cartilage
model (e.g., long bones).
Hormones Affecting Bone Growth
o Growth hormone + IGF-I: Promote bone growth.
o Vitamin D: Aids calcium absorption.
o Calcitonin: Lowers blood calcium.
o Parathyroid hormone: Raises blood calcium.
Unit 3: Major Bones and Bony Landmarks
Axial Skeleton
o Includes: Skull, vertebral column, rib cage.
