2. Chapter 4: The Skeletal System
Lesson 4.1
Bone as a Living Tissue

3. Functions of the Skeletal System
Support
Our bones form the internal support system that provides shape and support to our trunk and limbs.
Protection
Our bones surround and support the body’s delicate internal organs. E.X. the ribs protect the heart and lungs in the thoracic cavity.
Movement
When muscles contract or shorten, they pull on the attached bones causing movement.
Storage
Bones also serve as a storage repository for minerals, such as phosphorous and calcium.
Blood cell formation (hematopoiesis)
Occurs in the red bone marrow in medullary cavity

4. Structures and Classifications of Bones
Composition of bones
Osteocytes mature bone cells
60–70% of bone weight comes from its mineral content; Calcium Carbonate and Calcium Phosphate.
30–40% of bone weight comes from collagen, (protein that provides bone’s flexibility) and water.
Organization of bones
Bone is structurally organized into two different types of tissue
Cortical: relatively dense
Trabecular: also known as spongy bone, is relatively porous, with a honeycomb structure

5. Shape Categories of Bones
Bones are traditionally divided into four categories:
Long bones
Long, round shaft, with bulbous knobs at both ends.
Shafts enclose the central hollow medullary cavity or canal.
Major bones of the arms and legs.
Short bones
Shaped like a cube.
Bones of the wrists and ankles.
Flat bones
Thin, large in surface area, and generally curved
The scapula and bones of the skull
Irregular bones
All other bones
Bones of the spinal column and hip girdle

6. Anatomical Structure of Long Bones
Diaphysis of a long bone, the hollow shaft, is composed of cortical bone. A fibrous connective, periosteum, surrounds and protects the diaphysis.
Periosteum contains blood and lymph vessels, as well as nerves. It is involved in bone growth, repair, and nutrition.
The hollow center of the diaphysis, is filled with yellow bone marrow, (from the age of 5) with a rich supply of blood vessels and is a storehouse for fat.

7. Anatomical Structure of Long Bones
The bulbous endings of the long bones are known as epiphyses.
contain red marrow, which participates in the formation of red blood cells, and some white blood cells
Each epiphysis is surrounded by a protective covering of articular cartilage.
Canaliculi and lacunae provide a matrix for the supply of nutrients and the removal of waste products.

8. Growth and Development of Bones
Osteoblasts
build new bone tissue
Osteoclasts
break down weakened or damaged bone tissue
Bone formation
Skeleton of early-developing embryos is composed mainly of a flexible tissue called hyaline cartilage.
This cartilage is replaced by bone as the fetus develops by a process called ossification.
As an adult, cartilage still forms parts of the nose, ribs and some joints.

9. Growth and Development of Bones
Longitudinal growth
Bones grow in length at the epiphyseal plates, located close to the ends of long bones
Circumferential growth
Most bone growth occurs during childhood, bones actually grow in diameter throughout most of life
Adult bone development
Aging results in a progressive loss of collagen (which provides elasticity) and increase in bone brittleness
Bone mineral normally peaks
In women at about 25 to 28 years of age
In men at about 30 to 35 years of age. Thereafter, bone mass is progressively lost

10. Review and Assessment
Match these words with 1–4 below: flat, osteocytes, osteoblasts, storage.
1. Build bone tissue
2. One example of bone shape
3. A function of the skeletal system
4. Mature bone cells
Osteoblasts
Flat
Storage
Osteocytes

11. Common Injuries and Disorders of the Skeletal System
Chapter 4: The Skeletal System
Lesson 4.5
Common Injuries and Disorders of the Skeletal System

12. Fractures A fracture is a break or a crack in a bone Greenstick Stress
Comminuted
Spiral

13. Epiphyseal Injuries These are injuries to the
Epiphyseal plate ( growth plate)
Articular cartilage (covers the ends of bones)
Apophysis (site where tendon attaches to bone)

14. Osteoporosis
This is a condition in which bone mineralization and strength are so abnormally low that regular, daily activities can result in painful fractures.
Age-related osteoporosis
Osteoporosis occurs in most elderly individuals, with earlier onset in women.
The female athlete triad
Occurs in female athletes at the high school and collegiate levels who strive to maintain an excessively low body weight.
Disordered eating
Amenorrhea (no menses)
Osteoporosis

15. Common Joint Injuries Sprains Dislocations Bursitis
Caused by abnormal motion of the articulating bones that result in overstretching or tearing of ligaments, tendons, or other connective tissues crossing a joint.
Most common site of a sprain is the ankle.
Dislocations
When one of the articulating bones is displaced from the joint socket.
Common dislocation sites are: shoulders, fingers, knees, elbows, and jaw
Bursitis
Inflammation of bursae (fluid-filled sacs that provide cushioning) due to overuse leading to irritation.
Most commonly experienced by runners between the Achilles tendon and the calcaneus

16. Arthritis
Commonly associated with aging and is characterized by joint inflammation accompanied by pain, stiffness, and sometimes swelling.
Over one hundred different types of arthritis have been identified
Rheumatoid arthritis
Autoimmune disorder in which the body’s own immune system attacks healthy joint tissues.
It is the most debilitating and painful form of arthritis.
Osteoarthritis
Non-inflammatory, degenerative disease of articular cartilage

17. Review and Assessment True True True True True or False?
1. A torn ligament causes a sprain.
2. Low strength bones easily break.
3. Immune system attack causes amenorrhea.
4. Greenstick is a type of fracture.
5. Bursitis is an inflammation of bursae.
True
True
False
True
True