ch06 Student

Chapter 6: The Skeletal System

Overview

  • This chapter examines the skeletal system, particularly the structure and function of bone tissue.

  • It is based on the 14th Edition of "Principles of Anatomy and Physiology" by John Wiley & Sons, Inc.

6.1 Functions of the Skeletal System

  • Support: Provides a framework for the body and supports soft tissues.

  • Protection: Shields vital organs (e.g., skull protects the brain, rib cage protects the heart and lungs).

  • Movement: Serves as levers for muscles to produce movement.

  • Mineral Storage: Stores minerals such as calcium and phosphorus, which can be released into the bloodstream as needed.

  • Blood Cell Production: Houses red bone marrow, which produces blood cells.

  • Energy Storage: Stores lipids in adipocytes within yellow marrow.

6.2 Structure of Long Bones

  • Parts of a Long Bone:

  • Diaphysis: The shaft of the bone.

  • Epiphyses: The ends of the bone at joints.

  • Metaphysis: The region between diaphysis and epiphysis, including the growth plate.

  • Articular Cartilage: Hyaline cartilage covering the epiphyses for friction-free movement.

  • Medullary Cavity: Hollow space within the diaphysis that contains bone marrow.

  • Endosteum: A thin membrane lining the medullary cavity.

  • Periosteum: A connective tissue layer surrounding the outer surface of the bone.

6.3 Bone Classes

  • Long Bones: E.g., Humerus and Femur.

  • Short Bones: E.g., Talus.

  • Flat Bones: E.g., Sternum.

  • Irregular Bones: E.g., Vertebrae.

6.4 & 6.5 Bone Tissue Classification and Cellular Composition

  • Bone is classified as a connective tissue due to its extracellular matrix.

  • Cell Types in Bone:

  • Osteoprogenitor Cells: Stem cells that develop into osteoblasts.

  • Osteoblasts: Cells that form bone extracellular matrix.

  • Osteocytes: Mature bone cells that maintain bone tissue.

  • Osteoclasts: Cells responsible for bone resorption, breaking down bone matrix.

6.6 Compact vs. Spongy Bone Tissue

  • Compact Bone: Dense outer layer, provides strength and support.

  • Spongy Bone: Lighter, contains red marrow, provides space for bone marrow.

6.7 Blood and Nerve Supply of Bone

  • Periosteal Arteries: Enter diaphysis through Volkmann’s canals.

  • Nutrient Artery: Enters through a nutrient foramen.

  • Metaphyseal and Epiphyseal Arteries: Supply blood to metaphysis and epiphysis respectively.

6.8 Ossification Processes

  • Intramembranous Ossification: Formation of flat bones; begins with osteoblasts secreting the matrix.

  • Endochondral Ossification: Formation of long bones; cartilage model is replaced by bone.

6.9 & 6.10 Bone Growth and Remodeling

  • Bone Growth: Occurs through interstitial growth (length) and appositional growth (thickness).

  • Remodeling: Continuous process of bone resorption and formation; regulated by mechanical stress and hormonal changes.

6.11-6.12 Fracture Types and Repair

  • Types of Fractures: Open (compound), comminuted, greenstick, impacted, Pott’s, and Colles fractures.

  • Healing Stages:

  • Reactive Phase: Formation of fracture hematoma.

  • Reparative Phase: Development of fibrocartilaginous callus and bony callus.

  • Bone Remodeling Phase: Reshaping and strengthening of the bone after healing.

6.13-6.14 Bone Tissue's Role in Calcium Homeostasis

  • Regulation of Blood Calcium: Involves parathyroid hormone (increases calcium levels) and calcitriol (active form of vitamin D).

6.15-6.17 Effects of Aging on Bone Tissue

  • Aging leads to decreased bone density and strength, resulting from a balance between bone deposition and resorption shifting towards resorption.

  • Common Disorders: Osteoporosis, osteomalacia, and Paget’s disease may arise as bone remodeling processes change.