The skeletal system is composed of bones and connective tissues that provide structure and support to the body. It has several functions including support, protection, movement, blood cell formation, and storing minerals. There are 206 bones in the human body that are classified as long, short, flat, or irregular. All bones consist of compact bone on the outside and spongy bone on the inside. Bones contain osteoblasts, osteoclasts, and osteocytes. Osteoblasts build bone, osteoclasts break down bone, and osteocytes maintain bone tissue. Bone matrix is made up of organic collagen fibers and inorganic minerals like hydroxyapatite that give bone its strength and rigidity.

1. Skeletal System
Prepared by
Arfan Ahmed Shourov
Radiant pharmaceutical Ltd

2. Skeletal System

3. Skeletal System
Composed of the body’s bones and associated ligaments, tendons, and
cartilages
Functions
1. Support
2. Protection
3.
Movement
4. Hematopoiesis
5. Reservoir for minerals
and adipose tissue

4. Functions
1. Support
framework that supports body and cradles its soft organs
2. Protection
For delicate organs, heart, lungs, brain
3. Movement
Bones act as levers for muscles

5. Functions
4. Hematopoiesis
Blood cell formation-
5. Reservoir for minerals and adipose tissue
calcium & phosphate

6. Bone Classification
206 named bones in the human body
Each belongs to one of 2 large groups:
1. Axial skeleton (80 bones) :
Forms long axis of the body.
Includes the bones of the skull, vertebral column, and rib cage.
2. Appendicular skeleton (126 bones) :
Bones of upper & lower limbs and the girdles (shoulder bones and hip
bones) that attach them to the axial skeleton.

7. Bone Classification
4 types of bones:
1. Long Bones:



Much longer than they are wide.
All bones of the limbs except for the patella (kneecap), and the bones of the
wrist and ankle.
Consists of a shaft plus 2 expanded ends.
Example: metacarples, metatarsals, phelangies, humerus, ulna, radius,
tibia, fibula, Femur
Femur

8. Bone Classification
2. Short Bones:
 Roughly cube shaped.
 Bones of the wrist and the ankle.
Example: carpals, tarsals

9. Bone Classification
3. Flat Bones
 Thin, flattened, and usually a bit curved.
Example: rib, scapula, skull, sternum
scapula

10. Bone Classification
3. Irregular Bones
Have weird shapes that fit none of the 3 previous classes.
Vertebrae
Example: vertebrae, some facial bones,, hip bones
2 skull bones ( sphenoid and the ethmoid bones).
vertebrae
Hip bones

12. Bone Structure
All bones consist of a dense, solid outer layer known as compact bone
and an inner layer of spongy bone – a honeycomb of flat, needle-like
projections called trabeculae.

13. Bone cell Types
Osteoblast
Osteoclast
Osteocyte
Bone forming cells.
Bone resorption cells.
Mature bone cells.

14. Bone cells
1.Osteoblasts: Bone-building cells.
Synthesize and secrete collagen fibers and other organic components
of bone matrix.
Initiate the process of calcification.
Found in both the periosteum and the endosteum

15. Bone cells
2. Osteoclasts
Huge cells derived from the fusion of as many as 50 monocytes (a type
of white blood cell).
Cells that digest bone matrix – this process is called bone resorption
and is part of normal bone growth, development, maintenance, and
repair.

16. Bone cells
3. Osteocytes: Mature bone cells.
Osteoblasts that have become trapped by the secretion of matrix.
No longer secrete matrix.
Responsible for maintaining the bone tissue.

18. Bone structure
Bone Matrix:
Consists of organic and inorganic components.
1/3 organic and 2/3 inorganic by weight.
Organic component consists of several materials that are secreted by
the osteoblasts: Collagen fibers and other organic materials
These (particularly the collagen) provide the bone with resilience and
the ability to resist stretching and twisting.

19. Bone structure
Inorganic component of bone matrix
Consists mainly of 2 salts: calcium phosphate and calcium hydroxide.
These 2 salts interact to form a compound called hydroxyapatite.
Bone also contains smaller amounts of magnesium, fluoride, and
sodium.
These minerals give bone its characteristic hardness and the ability to
resist compression.