1. The Skeletal System

2. The human body has 206 bones that vary in size and shape
Bone Structure
The human body has 206 bones that vary in size and shape

3. 5 Functions of the Skeletal System
1. Movement: Skeletal system provides points of attachment for muscles. Your legs and arms move when the muscles pull on the bones.
2. Support: The backbone is the main support center for the upper body. It holds your head up and protects your spinal cord.
Muscle attached to bones

4. 5 Functions of the Skeletal System
3. Protection: The bones of your skull protect your brain. Your ribs protect your lungs and heart from injury.
4. Makes Blood: Red and white blood cells are formed by tissue called marrow, which is in the center of the bone.

5. 5 Functions of the Skeletal System
5. Storage: Bones store minerals, such as calcium and phosphorus, for use by the body

6. Two Major Skeletal System Parts
Axial Skeleton: The axial skeleton includes the skull, spine, ribs and sternum.
Appendicular Skeleton: The appendicular skeleton includes the appendages of the body, which are the shoulders, arms, hips, and legs.

7. Bone as Cells Osteon Structural unit of compact bone
Each consists of osteocytes (living bone cells) arranged in concentric rings around a central canal
Each osteocyte lies within a lacuna (small space within the hard matrix)

8. Bone as a Living Tissue
Tiny canals connect nearby lacunae and the central canal
Nutrients, oxygen, and wastes pass from cell to cell, traveling to and from the blood vessels in the central canal
The matrix of bone tissue is
Hard due to calcium and phosphorus salts
Resilient due to strands of the elastic protein collagen

9. Skeletal System Bones Four basic bone shapes
1. Long- arms, legs and fingers
2. Short- wrist and ankles
3. Flat- skull and sternum
4. Irregular- spine

10. Bone Shape Slide 5.4c Figure 5.1
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

11. Bone Structure Typical Four Layers: Periosteum: Covers Bones
Compact Bone: Lies beneath the periosteum
Spongy Bone: Lies beneath the compact bone
Bone Marrow: Fills the gaps between the spongy bone

13. Bone Structure Compact bone Dense outer layer with few internal spaces
Forms most of the shaft of long bones
Covered by the periosteum
Membrane that contains blood vessels, nerves, and cells involved in bone growth and repair

14. Bone Structure Spongy bone Latticework of bone
Found in small, flat bones and in the head and near the ends of the shafts of long bones
In adults
The spaces of some spongy bones are filled with red marrow (generates red blood cells)
The cavity in the shaft of long bones is filled with yellow marrow (a fatty tissue for energy storage)

16. Types of Bone
Most bones contain both compact bone and spongy bone in proportions that depend on the bone’s size and shape

18. Axial Skeleton Cranial bones - Eight flat bones Functions
Protect the brain
House the structures of hearing
Provide attachment sites for the muscles of the head and neck

19. Axial Skeleton Fontanels (soft spots)
Membranous areas that connect the bones of the cranium before and shortly after birth
Allow the skull to be compressed during birth as the baby passes through the birth canal
Allow for the rapid growth of the brain during the fetal period and infancy
Replaced by bone by 2 years of age

20. Axial Skeleton Rib cage
12 pairs of ribs attach at the back of the rib cage to the thoracic vertebrae
Upper 10 pairs are attached by cartilage either directly or indirectly to the sternum
Last two pairs do not attach to the sternum and are called “floating ribs”

21. Axial Skeleton The vertebral column consists of 26 vertebrae
7 cervical
12 thoracic
5 lumbar
1 sacrum (fusion of 5 sacral vertebrae)
1 coccyx (fusion of 4 vertebrae)

22. Axial Skeleton Intervertebral disks
Separate vertebrae from one another
Pads of fibrocartilage
Become compressed over the years and individuals become shorter as they age

23. Vertebral Column or Spinal Cord
1) The cervical region (neck bones) 
2) The thorasic region (what the ribs attach to)
3) The lumbar region (the lower part of the back) 

24. Coccyx and Sacrum

25. Appendicular Skeleton
Components
Pectoral girdle
Pelvic girdle
Limbs
Function
Allows you to move and interact with the environment

26. Appendicular Skeleton
Pectoral girdle
Components
Scapulae
Clavicles
Function
Supports the arms

27. Clavicle or Collarbone
The clavicle, or collar bone, holds the shoulder joint away from the rest of the upper body and is only as thick as your little finger.

28. Scapula
The scapula is located on the back side of the ribcage and helps provide part of the shoulder joint and movement for the arms.

29. Humerus (Upper Arm Bone)

30. Radius and Ulna
Radius on Top
Ulna on Bottom
radius rotates

31. Carpals or (Wrist Bones)

32. Metacarpals (Top of Hands)

33. Phalanges (Little Fingers)

34. Rib Cage

35. Sternum (Breastbone)