Dominican_University_A_P_1_-_Lesson_6_-_The_Skeletal_System_-_Bone_Tissues

Dominican University - Anatomy & Physiology I

• Course: BI223 DA 3

• Instructor: Spendy Pierre-Louis, PT, DPT, GCS

Principles of Anatomy & Physiology

• Focus: The Skeletal System: Bone Tissue

Functions of Bone and the Skeletal System

Overview of Bone

• Bone is an organ consisting of various tissues:

  • Bone

  • Cartilage

  • Dense connective tissue

  • Adipose

  • Nervous tissue

• The skeletal system comprises the entire framework of bones and cartilages.

Functions of the Skeletal System

• Provides structural support to the body

• Protects vital internal organs (e.g., brain, heart)

• Facilitates body movement in conjunction with muscles

• Mineral Homeostasis: stores and releases calcium and phosphorus

• Participates in blood cell production (hemopoiesis)

• Stores triglycerides in adipose cells located in yellow marrow

Structure of Bone

Parts of a Long Bone

• Diaphysis: the shaft of the bone

• Epiphyses: two ends of the bone (located at joints)

• Metaphyses: area between diaphysis and epiphyses

• Articular cartilage: covers both epiphyses

• Periosteum: connective tissue covering the diaphysis

• Medullary cavity: hollow space within the diaphysis

• Endosteum: thin membrane lining the medullary cavity

Bone Structure and Tissues

• Bone consists of two types:

  • Compact Bone: dense and provides strength

  • Spongy Bone: lightweight, with a porous structure; supports tissue

Histology of Bone

Composition of Bone Tissue

• Extracellular Matrix:

  • Approximately 15% water, 30% collagen, and 55% crystallized mineral salts

  • Hydroxyapatite is formed from calcium phosphate and calcium hydroxide

• Bone cells:

  • Osteoprogenitor cells: stem cells that can differentiate

  • Osteoblasts: bone-building cells

  • Osteocytes: mature bone cells

  • Osteoclasts: responsible for bone resorption

Microscopic Structure

• Osteons: structural units of compact bone

  • Contain central canals, lacunae, and lamellae

• Trabecular organization in spongy bone helps distribute stress and supports marrow

Blood and Nerve Supply of Bone

• Periosteal arteries and nerves enter the diaphysis via Volkmann’s canals

• Nutrient artery penetrates through nutrient foramen, providing essential blood supply

• Metaphyses and epiphyses have their own vascular supply

Bone Formation (Ossification)

Overview

• Ossification occurs under four circumstances:

  • Embryological and fetal development

  • Growth before adulthood

  • Bone remodeling

  • Healing of bone fractures

Types of Ossification

1. Intramembranous: Formation of flat bones from connective tissue

2. Endochondral: Replacement of cartilage with bone during development

Aging and Bone Tissue

Factors Impacting Bone Growth

• Minerals: Calcium, phosphorus, magnesium, fluoride, and manganese essential for matrix formation

• Vitamins: A, C, D, K, and B12 have crucial roles in bone metabolism and health

• Hormones: GH, IGFs, thyroid hormones, and sex hormones impact growth and remodeling

Disorders

• Osteoporosis: Greater bone resorption than formation

• Rickets: Vitamin D deficiency leading to growth deformities in children

• Osteomalacia: Similar to rickets, but affects adults, resulting in soft bones

Bone's Role in Calcium Homeostasis

• Bones store 99% of body's calcium

• Parathyroid hormone (PTH) regulates calcium level by stimulating osteoclast activity

• Blood calcium levels are maintained through PTH and calcitonin interactions

Summary

• Factors affecting bone growth include minerals, vitamins, hormones, and exercise

• Aging results in decreased bone mass in post-menopausal women

• Understanding bone health is vital for avoiding fractures and maintaining overall health.