1. Skeletal System Inside look at the BONES Image from: www.interactive-biology.com

2. Parts of the Skeletal System  Bones (Skeletal organ)  Joints  Cartilage  Ligaments  Tendons

3. Types of Bones Bones are classified by their structure each vary in proportions of compact and cancellous.  Long  Short  Flat  Irregular  Sesamoid

4. Short, Flat, Irregular, Sesamoid  Short  Cube or boxed shaped  Examples: Carpals and Tarsals  Flat  Broad and thin with flattened and curved surface  Filled with marrow  Example: Sternum  Irregular  Misshaped bones found in groups  Examples vertebral and facial bones  Sesamoid  Found in locations where a tendon passes a joint  Example: patella

5. Long Bones Known for its length and distinct structures  Diaphysis  Main shaft of a long bone  Hollow, cylindrical shape and thick compact bone  Function is to provide strong support without cumbersome weight  Epiphyses  Both ends of a long bone; made of cancellous bone filled with marrow  Function is to provide attachments for muscles and give stability to joints

6. Long Bone (continued)  Articular cartilage  Layer of hyaline cartilage that covers the articular surface of epiphyses  Function is to cushion jolts and blows  Periosteum  Dense, white fibrous membrane that covers bone  Attaches tendons firmly to bones  Contains blood vessels  essential for bone cell survival and bone formation

7. Long Bone (continued)  Medullary (or marrow) cavity  Tubelike, hollow space in the diaphysis  Filled with yellow marrow in adults  Endosteum:  Thin, fibrous membrane that lines the medullary cavity  Sharpey’s fibers  Secure periosteum to underlying bone  Arteries  Supply bone cells with nutrients

8. Distal epiphysis Proximal epiphysis diaphysis yellow marrow epiphyseal line periosteum compact bone spongy bone Endosteum hyaline cartilage Sharpey’s fibers Anatomy of the Long Bone

9. Bone Tissues  Most distinctive form of connective tissue  Composition  Inorganic salts ( calcium, phosphate, magnesium and sodium)  Organic matrix (collagenous fibers, proteins and polysaccharides, glucosamine)  Two basic types  Compact Bone  Spongy Bone

10. Compact Bone  Contains many cylinder-shaped structural units called osteons, or haversian systems  Osteons surround haversian canals that run lengthwise through bone and are connected by transverse (Volkmann) canals  Living bone cells are located in osteon  Osteons permit delivery of nutrients and removal of waste products

11. Structures of Osteon  Lamella- concentric calcified matrix  Lacunae- spaces filled with tissue fluid between lamella  Canaliculi- ultra small canals that connect lacunae and harvesian canals  Harvesian canals- contain blood vessels and lymphatic vessels Gray’s Anatomy of the Human Body from the classic 1918 publication

12. Cancellous (Spongy) Bone  No osteons in cancellous bone; it has trabeculae instead  Nutrients are delivered and waste products removed by diffusion through tiny canaliculi  Bony branches (trabeculae) are arranged along lines of stress to enhance the bone’s strength

14. Types of Bone Cells  Osteocytes  Mature bone cells  Osteoblasts  Bone-forming cells  Osteoclasts  Bone-destroying cells  Break down bone matrix for remodeling and release of calcium  Bone remodeling is a process by both osteoblasts and osteoclasts

15. Blood supply  Bone cells are metabolically active and need a blood supply  Supplied from bone marrow  Bone marrow and blood vessels penetrates the bone and then, by way of transverse (Volkmann) canals, connects with vessels in the central canals of osteons

16. Bone Marrow  Composition  Myoloid- soft connective tissue  Function  Site of for production of blood cells; hematopoises  Location  Medullary cavities of long bones  Empty spaces of spongy bone

17. Types of Marrow  Red marrow  Found in virtually all bones in an infant’s or child’s body  Produces red blood cells  Yellow marrow  As an individual ages, red marrow is replaced by yellow marrow  Marrow cells become saturated with fat and are no longer active in blood cell production

18. Bones Function  Support- form the framework that supports the body and cradles soft organs.  Protection- provides a protective case for brain, spinal cord and vital organs  Movement- provides levers for muscles  Mineral Storage- reservoir for minerals especially calcium  Blood cell formation- hematopoiesis occurs in the within the marrow cavities of the bones

19. Calcium levels  98% calcium in the body is found in bones  Calcium levels change as a result of bone remodeling.  Homeostasis of calcium ion concentration affects several functions  Bone formation, remodeling and repair  Blood clotting  Trasmission of nerve impulses  Cardiac and skeletal muscle contractions

20. Mechanism of Calcium Homeostasis  Parathyroid hormone  Primary regulator of calcium homeostasis  Calcitonin  Protein hormone produced in the thyroid gland  Produced in response to high blood calcium levels

21. Bone Development  Osteogenesis  development of bone small cartilage model to adult model  Endochondral ossification  Bone formation spreading essentially from the center to the ends  Replacement of hyaline cartilage

22. From cartilage to bone  Cartilage cells (chondrocytes) begin to die, region becomes known as the ossification center  Primary- middle of diaphysis  Secondary- epiphysis  Periosteum is forming around the outside of the cartilaginous model.  Periosteum produces osteoblast  Osteoblasts build up on the periphery of the spongy bone, they secrete their matrix and build compact bone all around the spongy bone.  This occurs simultaneously

25. The Growing Bone  Epiphyseal plate remain between diaphysis and both epiphysis.  Its is composed of 4 layers  “Resting” cartilage cells-  Zone of proliferation- cartilage cells undergoing mitosis  Zone of hypertrophy- older cells undergoing degenerative changes  Zone of Calcification- dead cartilage cells undergoing calcification  Osteoclast widen the medullary cavity  Osteoblast build new bone around existing bone

26. Cartilage  Characteristics  Avascular connective tissue  Fibers of cartilage are embedded in a firm gel  Has the flexibility of firm plastic  No canal system or blood vessels  Functions  Tough, rubberlike nature permits cartilage to sustain great weight or serve as a shock absorber  Strong yet pliable support structure  Permits growth in length of long bones

27. Types of Cartilage  Hyaline cartilage  Most common type  Covers the articular surfaces of bones  Elastic cartilage  Forms external ear, epiglottis, and eustachian tubes  Fibrocartilage  Occurs in pubic symphysis and intervertebral disks  Strong and rigid

28. Bone Fractures  Fracture—break in a bone  Types of bone fractures  Closed (simple) fracture—break that does not penetrate the skin  Open (compound) fracture—broken bone penetrates through the skin  Bone fractures are treated by reduction and immobilization

29. Common Types of Fractures Table 5.2

30. Bone repair  Healing 1. Fractures destroy blood vessels 2. Vascular damage initiates repair 3. Dead bone is removed by osteoclastic resorption 4. Fracture hematoma(blood clot cause duiring break) is reabsorbed and callus ( Specialized repair tissue) is deposited in bones