Lesson 4.1

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 • Osteocytesmature 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. 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 • 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 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