2. Bones: Tissue and Organ -Bones can be referred to as either a tissue (osseous) or an organ –Bone referred to as a connective tissue consists of: cells extracellular matrix (ground substance + fibers) this living/dynamic tissue is capable of growth and repair –Bone referred to as an organ (particular bones of the body) consists of: osseous tissue nervous tissue epithelial and muscle tissue (blood vessels) Ex. femur, humerus, clavicle, sternum…

3. Function of Bones Support –form the framework that supports the body Protection –provide a protective cavity for the brain (skull), spinal cord (vertebrae), and vital organs (rib cage) Movement –provide attachment points for skeletal muscles and are used as levers Mineral storage –reservoir for calcium and phosphorus Blood cell formation (hemopoiesis) –occurs within the red bone marrow of bones

4. Shapes of Bones

5. Gross Anatomy of Bones: Bone Textures Compact bone –dense and heavy bone Spongy bone –porous and light bone -formed by rods and plates of bone called trabeculae -spaces filled with red bone marrow –provides strength with little weight trabeculae develop along bone’s lines of stress The bones of the body contain both bone textures –the outer layer is made of compact bone –the inner portion of bones is made of spongy bone

6. Compact and Spongy bone

7. Structure of Long Bones Diaphysis –tubular shaft that forms the long axis of long bones -composed only of compact bone that surrounds the medullary cavity during growth periods contains red bone marrow in adults, contains yellow bone marrow (fat) Epiphyses –expanded ends of long bones -exterior is compact bone, and the interior is spongy bone –superficial surface covered in articular (joint) cartilage –epiphyseal line separates the diaphysis from the epiphyses and represents location of bone lengthening

8. Structure of Long Bones

9. Epiphyseal Plates

10. Coverings of Bone There are 2 surfaces of a bone that are covered with a thin layer of connective tissue –The most superficial surface is covered by the periosteum -The surface of the medullary cavity of long bones is covered with endosteum Both the periosteum and the endosteum contain cells that are capable of increasing and decreasing the amount of bone tissue –bone remodeling

11. Composition of Bone (Extracellular) Matrix Inorganic components –hydroxyapatites calcium and phosphate mineral deposits 65% of bone by mass responsible for bone hardness Fibers –collagen provides an ability of bone to flex slightly without fracture

12. Cells of Osseous Tissue Osteoblasts –cells that make (deposit) the matrix of osseous tissue –increase bone density Osteoclasts –cells that break down (resorb) the matrix of osseous tissue –decrease bone density Osteocytes –cells that are surrounded by matrix (located in a lacunae) that are not depositing or resorbing matrix

13. Bone Dynamics The osteoblasts and osteoclasts in the periosteum and endosteum are responsible for the process of bone development, growth and remodeling The remodeling of bone refers to the increase or decrease in the density of bone in response to: –changes in blood calcium levels related to diet and metabolism –levels of circulating hormones -changes in the stress level put on the bones

14. Bone Remodeling The stimulation of osteoclasts result in the resorption of bone matrix which: –decreases bone density –releases the calcium and phosphate into the blood increasing their levels The stimulation of osteoblasts result in the deposition of bone matrix which: –increases bone density –removes calcium and phosphate from the blood decreasing their levels

15. Bone Histology The basic structural unit of bone is called the osteon (haversian system) -cylinders of matrix (lamellae) that form from layers arranged around central canal holding blood vessels and nerves that are parallel to the longest dimension of the bone (- the rings) –osteocytes (within lacunae) are connected to each other and to a blood supply by tiny cracks in the lamellae called canaliculi Lamellae are rings of extracellular matrix (like the growth rings on a tree) -transverse (blood vessels) (- the cracks)

16. –Volkmann canals - canals that are perpendicular to the central canals joining them to the blood and nerve supply at the superficial surface of the bone

18. Osteon of Compact Bone

20. Joints (Articulations) Site where two or more bones meet Weakest (structurally) parts of the skeleton Functions include: –provide mobility for the skeleton bones move in relation to one another where the joints serve as a fulcrum (pivot point) and the associated bones serve as levers –hold the skeleton together

21. Functional Classification of Joints -The three functional classes of joints are: –Synarthroses Immovable (head) –Amphiarthroses slightly movable (vertebrae) –Diarthroses freely movable

22. Range of Motion -Varies greatly from one type of joint to another -Factors affecting range of motion –structure of the bones that make up joint –strength and tautness of tendons and ligaments -gradual stretching of ligaments increases range of motion -”double-jointed” people have unusually long ligaments Tendons = tough inelastic material that joins muscles to bones Ligaments = elastic material that joins bones to bones -crack when crack knuckles e.g. Achilles tendon

23. Structural Classification of Joints The three structural classifications are: –Synovial –Fibrous –Cartilaginous Synovial Joints -Those joints in which the articulating bones are separated by a joint capsule filled with synovial fluid –all are freely movable –include all limb joints

24. Synovial Joints

25. Fibrous Joints The bones are joined by dense connective tissue containing a high amount of collagen –there is no joint capsule –most are immovable –include the bones of the skull

26. Fibrous Joints

27. Sutures

28. Cartilaginous Joints -Articulating bones are united by cartilage –there is no joint cavity –most are slightly movable (amphiarthroses) –include intervertebral discs

29. Cartilaginous Joints

30. Components of a Lever A lever is a rigid object that rotates around a fixed point called a fulcrum (joint) –A lever is divided into 2 lengths (arms) the resistance arm -the distance between the load that is to be moved and the fulcrum the effort arm –the distance between the muscle attachment point and the fulcrum

31. Elbow Joint

32. Mechanical Advantage of a Lever -Ratio of output force to input force Calculated from the length of the effort arm of the lever divided by the length of the resistance arm of the lever – E/R– E/R Most levers in the body have a small mechanical advantage: -due to the anatomy of the bones and the muscles that are attached to them –have large range of motion an advantage to move body parts –require a large effort to move a small load disadvantage for muscles