Bones Anatomy and Composition

Composition

• Bones are composed of:
  • Organic material (35%): collagen, a protein that gives bone its flexibility
  • Inorganic material (65%): hydroxyapatite, a mineral that gives bone its hardness and rigidity

Structure

• Bones have a compact outer layer (cortical bone) and a spongy inner layer (cancellous bone)
• Cortical bone is dense and compact, making up 80% of adult bone mass
• Cancellous bone is porous and lightweight, making up 20% of adult bone mass

Functions

• Support: provide a framework for the body
• Protection: protect internal organs, such as the brain and heart
• Movement: serve as attachment points for muscles
• Blood cell production: bone marrow produces blood cells
• Storage: store minerals such as calcium and phosphorus
• Endocrine function: regulate mineral homeostasis and hormone production

Types of Bones

• Long bones: characterized by a shaft (diaphysis) and two ends (epiphyses)
• Short bones: cube-shaped and approximately equal in length, width, and height
• Flat bones: thin and flat, often curved
• Irregular bones: complex shapes that do not fit into other categories
• Sesamoid bones: small, round bones embedded within tendons

Bone Development and Growth

• Ossification: the process of bone formation
• Endochondral ossification: bone formation from cartilage models
• Intramembranous ossification: bone formation from mesenchymal tissue
• Bone growth: occurs through the growth plate, a layer of cartilage at the end of long bones

Composition of Bones

• 35% of bone is composed of organic material, primarily collagen, which provides flexibility
• 65% of bone is composed of inorganic material, primarily hydroxyapatite, which provides hardness and rigidity

Structure of Bones

• Bones have a compact outer layer called cortical bone, which makes up 80% of adult bone mass
• Bones have a spongy inner layer called cancellous bone, which makes up 20% of adult bone mass
• Cortical bone is dense and compact, while cancellous bone is porous and lightweight

Functions of Bones

• Bones provide a framework for the body and support its overall structure
• Bones protect internal organs, such as the brain and heart
• Bones serve as attachment points for muscles, enabling movement
• Bones are responsible for producing blood cells through the bone marrow
• Bones store minerals such as calcium and phosphorus
• Bones regulate mineral homeostasis and hormone production through endocrine function

Classification of Bones

• Long bones have a shaft (diaphysis) and two ends (epiphyses)
• Short bones are cube-shaped and approximately equal in length, width, and height
• Flat bones are thin and flat, often curved
• Irregular bones have complex shapes that do not fit into other categories
• Sesamoid bones are small, round bones embedded within tendons

Bone Development and Growth

• Ossification is the process of bone formation
• Endochondral ossification is the process of bone formation from cartilage models
• Intramembranous ossification is the process of bone formation from mesenchymal tissue
• Bone growth occurs through the growth plate, a layer of cartilage at the end of long bones