1. Section 2 Skeletal System
Chapter 45
Objectives
Distinguish between the axial skeleton and the appendicular skeleton.
Explain the function and structure of bones.
Summarize how bones develop and elongate.
List three types of joints and give an example of each.
Describe a common disorder that affects the skeleton.

2. Section 2 Skeletal System
Chapter 45
The Skeleton
A skeleton is the bones of a human or animal body that form the framework of the body, support the muscles and organs, and protect the inner organs.
The variation in size and shape among the bones that make up the skeleton reflects their different roles in the body.

3. Section 2 Skeletal System
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Human Skeleton

4. The Skeleton, continued
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The Skeleton, continued
The human skeleton is composed of two parts—the axial skeleton and the appendicular skeleton.
The bones of the arms and legs, along with the scapula, clavicle, and pelvis, make up the appendicular skeleton.
The bones of the skull, ribs, spine, and sternum form the axial skeleton.

5. Subsections of the Human Skeleton
Section 2 Skeletal System
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Subsections of the Human Skeleton
The purple is the axial skeleton and the yellow is the appendicular skeleton.

6. Anatomy of a Human Skeletal System
Section 2 Skeletal System
Chapter 45
Anatomy of a Human Skeletal System
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Visual Concept

7. Bone Function and Structure
Section 2 Skeletal System
Chapter 45
Bone Function and Structure
The bones that make up the skeleton function in a variety of ways, such as supporting the muscles, protecting internal organs, helping movement, and playing vital roles in important metabolic processes.
Bones do not make up most of a body’s mass.

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Bone Function and Structure, continued
Long Bone Structure
A long bone’s surface is covered by a tough membrane called the periosteum.
Periosteum is a white, double layered membrane that covers the entire surface of bone except for the joint surfaces and is richly supplied with nerve fibers and blood vessels.

9. Bone Function and Structure, continued
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Bone Function and Structure, continued
Long Bone Structure, continued
Under the periosteum is a hard material called compact bone, and this part of the bone gives all bones their strength and rigidity.
Compact bone is composed of cylinders made of mineral crystals and protein fibers called lamellae.

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Bone Function and Structure, continued
Long Bone Structure, continued
Each lamellae is made up of a narrow channel called a Haversian canal, which contains the blood vessels in compact bone.
Surrounding each Haversian canal are protein fibers and osteocytes.
Osteocytes are a specific type of bone cell.

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Bone Function and Structure, continued
Long Bone Structure, continued
Beneath some compact bone is a network of connective tissue called spongy bone.
Spongy bone is less dense bone tissue that has many open spaces.

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Structure of Bone

13. Bone Function and Structure, continued
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Bone Function and Structure, continued
Bone Marrow
Bone marrow is a soft tissue inside some bones that can be either red or yellow.
The type of bone marrow present determines both its composition and function.

14. Parts of a Human Bone - 1 & 2 Chapter 45 Section 2 Skeletal System
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15. Bone Function and Structure, continued
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Bone Function and Structure, continued
Injury and Repair
Despite their strength, bones will crack or even break if they are subjected to certain situations or are overused.
A crack or break is referred to as a fracture.
A fracture is an injury in which the tissue of a bone is broken.

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Bone Development
During fetal development, some bones that were originally cartilage will slowly be replaced by actual bone. This process is called ossification.

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Bone Development, continued
Bone Elongation
Bones continue to grow after a person’s birth.
Bone elongation and growth take place near the ends of long bones in an area known as the epiphyseal plate.
The epiphyseal plate is found at the joint ends of long bones and is composed of cartilage. This area of bone will eventually become mature bone.

18. Human Bone Growth Chapter 45 Section 2 Skeletal System
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19. Joints Chapter 45 The place where two bones meet is known as a joint.
Section 2 Skeletal System
Chapter 45
Joints
The place where two bones meet is known as a joint.
Three major kinds of joints are found in the human body—fixed, semimovable, and movable.
Fixed Joints
A fixed joint is a joint at which no movement occurs.

20. Joints, continued Semimovable Joints Chapter 45
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Joints, continued
Semimovable Joints
A semimovable joint is one that will permit limited movement.
Cartilage can be involved to help these joints move.

21. Joints, continued Movable Joints Chapter 45
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Joints, continued
Movable Joints
A movable joint is a joint at which a wide range of motion occurs.
There are different types of movable joints, including hinge, ball-and-socket, pivot, saddle, and gliding.
A hinge joint allows limited movement in only one plane.

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Joints, continued
Movable Joints, continued
A ball-and-socket joint is another type of moveable joint and allows 360 degree movement in 2 planes.
A pivot joint allows 180 degree movement in only one plane.
A saddle joint will allow 360 degree movement in only one plane.
A gliding joint allows bones to slide over one another.

23. Joints, continued Joint Structure Chapter 45
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Joints, continued
Joint Structure
Joint structure helps movable joints deal with the pressure and stress of everyday life.
Joints are covered with cartilage and secrete synovial fluid to reduce friction. Joints are also connected with ligaments to aid in joint movement.
Even with all this protection a joint can still be injured.

24. Joints, continued Joint Structure, continued Chapter 45
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Joints, continued
Joint Structure, continued
The term arthritis is used to describe disorders that cause painful, swollen joints.
Rheumatoid arthritis develops when the immune system begins to attack body tissues, and joints become stiff and deformed.
Osteoarthritis is a degenerative joint disease in which the cartilage covering the surface of bone becomes thinner and rougher.

25. Section 2 Skeletal System
Chapter 45
Types of Joints

26. Types of Joints Chapter 45 Section 2 Skeletal System
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