Copyright 2010, John Wiley & Sons, Inc. Chapter 6: Introduction to the Skeletal System

Copyright 2010, John Wiley & Sons, Inc. Chapter 6: Introduction to the Skeletal System The skeletal system provides a framework for all of the other structures in the body The skeletal system consists of bones, cartilages, ligaments, and tendons Each bone is a dynamic structure that contains multiple tissues Long term changes in bone at the tissue level can lead to an overall change in bone shape and strength

Copyright 2010, John Wiley & Sons, Inc. The Skeletal System Performs Six Key Functions in the Body Support - the structural framework of the body Protection - bones protect sensitive internal organs Movement - bones and joints allow muscular actions Mineral homeostasis - bones store calcium and other important minerals Blood cell production - all blood cells originate in the red bone marrow Triglyceride storage

Copyright 2010, John Wiley & Sons, Inc. The Six Key Functions of the Skeletal System Fall into Two Groups STRUCTURAL ROLES Support Protection Movement HOMEOSTASIS Mineral homeostasis Blood cell production Triglyceride storage

Copyright 2010, John Wiley & Sons, Inc. Bones are Classified into One of Five Basic Shapes

Classification of Bone Long Flat Short Irregular Sesamoid

Long bones - slightly curved for strength – femur, tibia, fibula, humerus, ulna, radius, phalanges Short bones - cube shaped – carpals and tarsals Flat bones - thin, protection, muscle attachment. – cranial bones, sternum, ribs, scapula

Irregular bones - complex shape – vertebrae, hip bones, facial bones, heel bone (calcaneus) Sesamoid bones – seed shaped – develop in tendons due to friction – palms of hands, soles of feet, patella

Copyright 2010, John Wiley & Sons, Inc. Long Bones - Anatomy and Terminology Regions of a long bone – 1 diaphysis [the shaft] – 2 metaphyses – 2 epiphyses (proximal and distal) – 1 marrow cavity Surface tissues – Endosteum – Periosteum – Articular cartilage

Anatomy of a long bone Diaphysis=shaft Epiphysis=ends Metaphysis=between diaphysis and epiphysis Articular cartilage=hyaline cartilage covering the epiphysis Periosteum=layer of CT covering outside of bone Medullary cavity=marrow cavity contains yellow bone marrow Endosteum= layer of CT that lines medullary cavity

Anatomy of a long bone

Copyright 2010, John Wiley & Sons, Inc. Long Bones - Anatomy and Terminology

Histology of bone What type of tissue is bone? Extracellular matrix= 25% water, 25% collagen fibers, 50% crystalllized mineral salts(hydroxyapatite) Hardness of bone is due to mineral salts Tensile strength (resistance to being stretched or torn apart) due to collagen fibers

Bone Strength human-body-bone-strength-video.htm human-body-bone-strength-video.htm

CONCEPT CHECK DEC 3 You know what to do… 1. These bones are characterized by a cube-like shape and include the carpals. 2. Where is red bone marrow found within a long bone? 3. Bone is classified as this tissue type. 4. New growth occurs in this region of a long bone. 5. Which three functions of bone have structural roles in the human body?

CONCEPT CHECK DEC 3 You know what to do… 1. SHORT BONES 2. IN THE EPIPHYSES 3. CONNECTIVE TISSUE 4. METAPHYSES ALONG THE EPIPHYSEAL LINES – Growth Plates 5. STRUCTURE, PROTECTION, MOVEMENT

A&P Critical Thinking Extension Humans are the most advanced species on Earth. All living things are said to progressively evolve to best survive and reproduce in their environments. Is it possible that humans have degenerated in some way? (Consider Anatomy and Physiology of the Human Body)

Bone Mass and Growth “Modern human skeletons have shifted quite recently towards lighter—more fragile, if you like—bodies. It started when we adopted agriculture. Our diets changed. Our levels of activity changed,” says study co-author Habiba Chirchir, an anthropologist in the Smithsonian’s Human Origins Program.Habiba Chirchir “Modern humans had 50 to 75 percent less dense trabecular bone than chimpanzees” Thickness, volume, and surface area of cancellous bone is very indicative of bone joint strength. Read more: made-human-joint-bones-lighter /#1LUlt7GTpxkAeuuV.99http:// made-human-joint-bones-lighter /#1LUlt7GTpxkAeuuV.99

Cells of Bone Osteogenic cells=unspecialized stem cells. Undergo cell division. Develops into osteoblast Osteoblast= cells that form bone do not undergo mitosis. Secrete collagen to build bone

Cells of Bone Osteocytes= mature bone cells derived from osteoblasts. No mitosis. Involved in exchange of nutrients and wastes in the blood. Osteoclasts=derived from monocytes(wbc) function in bone resorption (breakdown of matrix)

Copyright 2010, John Wiley & Sons, Inc. Osseous Tissue - Four Cell Types