1. The Skeleton System Chapter 8/ Part I Joe Pistack MS/ED

2. The Skeletal System

3.  Consists of:  Bones  Joints  Cartilage  Ligaments The skeletal system consists of 206 bones.

4. The Skeletal System  Functions:  Bones of the lower extremities support the weight of the body.  Support and protect the soft body organs.  Enables the body to move about.  Store a number of minerals, calcium and phosphorus are most important.  Red bone marrow produces blood cells.

5. Classification of Bones Bones are classified as follows:  Long bones-longer than they are wide. Found in the arms and legs.

6. Classification of Bones  Short Bones-shaped like cubes and are found primarily in the wrists and ankles.

7. Classification of Bones  Flat Bones-thin, flat, curved. Form the ribs, breastbone and skull.

8. Classification of Bones  Irregular Bones-differently shaped, not classified as long, short, or flat. Include hip bones, vertebrae, and various bones in the skull.

9. Tissue and Bone Formation  Osseous tissue-another word for bone.  Osteocytes-bone cells. - secrete an intercellular matrix. -contain calcium, minerals and protein fibers.

10.  Compact Bone-  Dense hard bone.  Found in shafts of long bones and outer surfaces of other bones. Two Types of Bone

11.  Spongy Bone-  Also called cancellous bone.  Less dense  Found at the ends of long bones and in the center of other bones.

12. Compact Bone  Microscopically-compact bone and spongy bone look different.  Compact bone is tightly packed, density gives it strength.  Osteon or haversion system-microscopic unit of compact bone.  Each haversion system consists of mature osteocytes arranged in concentric circles around large blood vessels.

13. Compact Bone  Area surrounding the osteocytes is filled with protein fibers, calcium and other minerals.  Protein fibers provide elasticity.  Minerals make bone tissue hard and strong.  Compact bone consists of many haversian systems running parallel to each other, system looks like a long cylinder.  Blood vessels run laterally to the haversian system, this ensures adequate blood supply to the bone tissue.

14. Compact Bone

15. Spongy Bone  Also called cancellous bone.  Does not have a haversian canal.  Bone tissue is arranged in plates called trabeculae.  Bony plates are separated by holes that give it a punched- out “swiss cheese” appearance.  Holes are important for: (1)decrease the weight of bone, make it lighter, and (2)contain red bone marrow.

16. Spongy Bone  Red bone marrow richly supplies the spongy bone with blood cells for use throughout the body.  Spongy bone is located in short, flat, and irregular bones.  Spongy bone is found in the ends of long bones.

17. Long Bone  Made up of an arrangement of compact and spongy tissue, which accounts for its strength.  Contains sites of growth and reshaping and structures associated with joints.

18. Long Bone Parts of a long bone:  Diaphysis-long shaft of the bone, composed primarily of compact bone, therefore it provides strength.  Epiphysis-enlarged ends of the long bone. Articulates or meets with a second bone at a joint. Consists of a thin layer of compact bone overlying spongy bone. Epiphysis are covered with cartilage.

19. Long Bone  Epiphyseal disc-band of hyaline cartilage located at each end, between the epiphysis and the diaphysis in a growing bone. This band of cartilage is the epiphyseal disc or growth plate.  Medullary cavity-hollow center of the diaphysis. The inside is lined with connective tissue called the endosteum.

20. Long bone  Periosteum-tough, fibrous connective tissue membrane that covers the outside of the diaphysis.  Anchored firmly to the outside of bone on all surfaces except articular cartilage.  Periosteum protects bone, serves as a point of attachment for muscle, contains blood vessels that nourish underlying bone.

21. Long Bone  Injury to the periosteum may have serious consequences to the health of the bone since this structure carries the blood supply.  Articular Cartilage-found on the outer surface of the epiphysis, forms a smooth shiny surface that decreases friction within a joint.

22. Ossification  Ossification-the formation of bone.  Occurs differently in flat and long bones.  In the fetus, flat bones in the skull consist of thin connective tissue membrane.  Ossification begins when the osteoblasts (bone forming cells), migrate to the region of the flat bones.  The osteoblasts secrete calcium and other minerals into the spaces between the membranes, thereby forming bone.  This process involves the replacement of thin membrane with bone.

23. Ossification of Long Bones  Ossification of long bones occurs as bone tissue replaces cartilage.  The fetal skeleton is composed largely of cartilage.  As the baby matures, osteoblasts invade the cartilage and gradually replace it with bone until all but the articular cartilage and the epiphyseal disc have been replaced by bone.  Isolated pieces of cartilage, such as the bridge of the nose and parts of the ribs remain.

24. Ossification

25. Growing Bones  Two types of bone growth occurs from infancy to adulthood. (1)Longitudinally-determines the height of an individual. (2)Thicker & wider-to support the weight of the adult.  Longitudinally-bone grows at the epiphyseal disc, (also called the growth plate).  Cartilage adjacent to the epiphysis continues to multiply and grow toward the diaphysis.  Cartilage next to the diaphysis is invaded by osteoblasts and become ossified.  As long as the cartilage continues to form within the epiphyseal disc, the bone will continue to lengthen.

26. Growing Bones  Longitudinal bone growth ceases when the epiphyseal disc becomes ossified and fused.  Growth hormone stimulates growth at the epiphyseal disc, making the child taller.  The sex hormones estrogen and testosterone cause the epiphyseal disc to fuse, inhibiting further longitudinal growth.  The epiphyseal disc is more sensitive to estrogen, this causes girls to tend to be shorter than boys.

27. Growing Bones  Longitudinal growth generally ceases after puberty.  Injury to the epiphyseal disc may impair longitudinal bone growth. Eg. Injured leg shorter than uninjured leg.  Giantism- hypersecretion of growth hormone.  Dwarfism- undersecretion of growth hormone.

28. Growth Hormone Abnormalities Giantism Dwarfism

29. Growing Thicker and Wider  After longitudinal bone growth ceases, bones continue to increase in thickness and width.  Bones are continuously being reshaped.  Bone reshaping is accomplished by a combination of the actions of osteoblasts and osteoclasts.  Osteoblasts- bone forming cells.  Osteoclasts- bone destroying cells.

30. Growing Bones  Osteoblastic Activity: While osteoblasts build new bone, osteoclasts, found on the inner bone surface break down bone tissue, thereby hollowing out the interior of the bone.  Osteoclastic Activity is like sculpting, the bricklayer lays the bricks and the sculptor will hollow out the middle so that it is not too heavy.  Bone resorption-(not reabsorption)-process whereby osteoclasts breakdown bone matrix.

31. Growing Bones  Bone resorption- widens the bone, moves calcium from the bone to the blood.  Bone resorption plays a crucial role in blood calcium levels.  Weight-bearing – factor that stimulates bone growth.  Exercise and weight bearing keep calcium in the bone and increase bone mass.  Bedridden and sedentary people tend to lose bone mass causing bones to be easily broken when stressed.

32. Surface Markings  Surface of bones appears bumpy and irregular.  Appearance is due to numerous ridges, projections, depressions, and grooves called bone surface markings.  These bone surface markings serve as points of attachment for muscles, tendons and ligaments.

33. Condyle  Condyle- large rounded knob that usually articulates with another bone.

34. Epicondyle  Epicondyle- an enlargement near or above a condyle.

35. Bone Markings  Head- an enlarged and rounded end of a bone.

36. Bone Markings  Facet- a small flattened surface.

37. Bone Markings  Crest- a ridge on a bone

38. Bone Markings Process-a prominent projection on a bone.

39. Bone Markings Spine- sharp projection.

40. Bone Markings Tubercle (tuberosity)- a knoblike projection.

41. Bone Markings Trochantor- a large (tuberosity) found only on the femur.

42. Bone Markings Depressions/Openings Foramen- an opening through a bone, usually serves as a passageway for nerves, blood vessels, and ligaments.

43. Bone Markings Fossa- a depression or groove.

44. Bone Markings Meatus-a tunnel or tubelike passageway.

45. Bone Markings  Sinus-a cavity or hollow space.

46. Fractures Fractures- break in the bone.  Simple Fracture- a break in which the overlying skin remains intact. Local tissue damage is minimal.  Compound Fracture- a broken bone that also pierced the skin. Ends of the broken bone usually cause extensive tissue damage.  Incomplete Fracture- (greenstick)-usually occurs in children, the break is incomplete because the child’s bone is still made up of some cartilaginous material.

47. Common Types of Fractures