1. Skeletal system

2. introduction
Bone consists of a variety of very active, living tissues:
Bone tissue
cartilage
Dense connective tissue
Blood
Nervous tissues

3. Physiology of bone: Provide point attachment for muscles
Protect and support softer tissues
House blood-producing cells
Store inorganic salts
Form passageways for blood vessels and nerves

4. Bone classification Bones are classified according to their shapes:
Short
Flat
Irregular
Sesamoid (round)
Long

5. Short bone
Short bones are somewhat cube like, with their lengths and widths roughly equal
Bones of the wrists and ankles

6. Flat bones Flat bones are plate like structures with broad surfaces
Ribs
Scapulae
Some bones of the skull

7. Irregular bones
Irregular bones have a variety of shapes and are usually connected to several other bones.
Vertebrae
Many facial bones

8. Sesamoid (round) bones
Small and nodular and are embedded within tendons adjacent to joints
Patella (kneecap)

9. Long bones Long bones have long longitudinal axes and expanded ends
Examples of long bones:
Forearm
thigh

10. Epiphysis of a long bone
At each end of a long bone is an expanded portion called an epiphysis.
The epiphysis articulates (forms a joint) with another bone.
The proximal epiphysis is nearest to the center of the body.
The distal epiphysis is farthest from the center of the body.
The shaft of the bone between the epiphysis, is called the diaphysis

11. Articular cartilage of a long bone
The outer surface of the articulating portion of the epiphysis is coated with a layer of hyaline cartilage called articular cartilage.

12. periosteum
Except for the articular cartilage on the bone’s ends, the long bone is completely enclosed by a tough, vascular covering of fibrous tissue called the periosteum

13. Periosteum continued The periosteum is firmly attached to the bone
The periosteal fibers are continuous with the connecting ligaments and tendons
The periosteum helps form and repair bone tissue

14. Shape determines function
A bone’s shape makes its functions possible
Processes are bony projections that provide sites where ligaments and tendons attach
Grooves and openings form passageways for blood vessels and nerves
Depression of one bone may articulate with a process of another.

15. Compact bone
The wall of the diaphysis is mainly composed of tightly packed tissue called compact bone or cortical bone.
This type of bone has a continuous extracellular matrix with no spaces.

16. Spongy bone The epiphysis are composed of spongy (cancellous) bone.
Spongy bone consists of numerous branching bony plates.
Irregular connecting spaces between these plates help reduce the bone’s weight.
The bony plates are most highly developed in the regions of the epiphysis that are subjected to compressive forces.

17. Medullary cavity
Compact bone in the diaphysis of a long bone forms a semi rigid tube, which has a hollow chamber called the medullary cavity that is continuous with the spaces of the spongy bone

18. Endosteum cells
The endosteum is a thin membrane which consists of connective tissue and lines the medullary cavities.
It is highly vascular and contains osteoclasts and osteoblasts.

19. Yellow marrow
A specialized type of soft connective tissue that fills the medullary cavity
Yellow marrow stores fat which the body consumes as a last resort in cases of extreme starvation. It also turns into red marrow in emergencies such as blood loss or anemia