The Skeletal System Chapter 5 The Skeletal System

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The Skeletal System Chapter 5

The Skeletal System Chapter 5

The Skeletal System • The skeleton is divided into two divisions: axial and appendicular

The Skeletal System • The skeleton is divided into two divisions: axial and appendicular – Axial Skeleton: bones that form the longitudinal axis of the body – Appendicular Skeleton: bones of the limbs and girdles • The Skeletal System includes: – Bones – Joints – Cartilage – Ligaments

Bones: An Overview • Besides contributing to body shape and form, our bones perform

Bones: An Overview • Besides contributing to body shape and form, our bones perform several important body functions: 1. Support – Bones form the internal framework that supports and anchors all soft organs – Ex: Bones of the legs act as pillars to support the body trunk when we stand 2. Protection – Bones protect soft body organs. – Ex: fused bones of the skull provide a snug enclosure for the brain that provides protection against injury

Bones: An Overview 3. Movement – Skeletal muscles use the bones as levers to

Bones: An Overview 3. Movement – Skeletal muscles use the bones as levers to move the body and its parts – As a result, we can walk, swim, throw a ball, and breathe 4. Storage – Bones act as a storage device for many things: – Fat is stored in the internal cavities of bones – Bones serve as a storehouse for minerals such as calcium and phosphorus 5. Blood Cell Formation – Hematopoiesis (blood cell formation) occurs within the marrow cavities of certain bones

Bones: An Overview • Classification of Bones – The adult skeleton is composed of

Bones: An Overview • Classification of Bones – The adult skeleton is composed of 206 bones – There are two basic types of bones: • Compact Bone: dense and looks smooth and homogenous • Spongy Bone: composed of small needlelike pieces of bone and lots of open space

Bones: An Overview • There are many different shapes and sizes of bones that

Bones: An Overview • There are many different shapes and sizes of bones that depend on the function of the particular bone. • There are 4 classifications of shape for bones: – Long – Short – Flat – Irregular

Bones: An Overview • Classification of Bone: – Long Bones: typically longer than they

Bones: An Overview • Classification of Bone: – Long Bones: typically longer than they are wide • As a rule, they have a shaft with heads at both ends • Mostly compact bone • Include all of the bones of the limbs, except the wrist and ankle bones

Bones: An Overview • Classification of Bone: – Short Bones: generally cube-shaped and contain

Bones: An Overview • Classification of Bone: – Short Bones: generally cube-shaped and contain mostly spongy bone • Includes the bones of the wrist and ankle • Includes Sesamoid Bones – Sesamoid Bones: specialized short bone that forms within tendons • Best known example = patella (kneecap)

Bones: An Overview • Classification of Bone: – Flat Bones: thin, flattened, and usually

Bones: An Overview • Classification of Bone: – Flat Bones: thin, flattened, and usually curved bones • Have two thin layers of compact bone sandwiching a layer of spongy bone • Includes most bones of the skull, ribs, and sternum (breast bone)

Bones: An Overview • Classification of Bone: – Irregular Bones: Any bones that do

Bones: An Overview • Classification of Bone: – Irregular Bones: Any bones that do not fit one of the other categories are called irregular bones • This includes the vertebrae, which make up the spinal column, and the hip bones

Bones: An Overview • Structure of a Long Bone: – Most of the bone’s

Bones: An Overview • Structure of a Long Bone: – Most of the bone’s length is made up of a diaphysis, or shaft. • The diaphysis is covered and protected by a fibrous connective tissue membrane called the periosteum – Hundreds of connective tissue fibers attach the periosteum to the underlying bone. These fibers are called Perforating Fibers – At the ends of the bones are the epiphyses, which consist of a thin layer of compact bone enclosing an area filled with spongy bone • Articular Cartilage covers the outside of epiphyses instead of periosteum

Bones: An Overview • Bone Structure Continued… – In adult bones, there is a

Bones: An Overview • Bone Structure Continued… – In adult bones, there is a thin line of bony tissue spanning the epiphysis that looks different from the rest of the bone in the area • This is known as the Epiphyseal Line, which is a remnant of epiphyseal plate used for bone growth in young, growing bones – In adults, the cavity of the shaft is primarily a storage area for adipose tissue and is known as the Medullary Cavity • In infants, this area forms red blood cells. Red blood cells only form in specific long bones in adults

Bones: An Overview

Bones: An Overview

Bones: An Overview • Bone Markings: – When looking at a bone, it is

Bones: An Overview • Bone Markings: – When looking at a bone, it is easy to see bumps, holes, ridges, etc. • These characteristics are known as Bone Markings – These bone markings reveal where muscles, tendons, and ligaments were attached as well as where blood vessels and nerves passed • There are 2 categories of Bone Markings – Projections (or Processes): grow out from bone surfaces – Depressions (or Cavities): indentations in the bones