The Functions of the Skeletal System Bone Classification Bone Structure Bone Formation and Development Fractures: Bone Repair Exercise, Nutrition, Hormones,

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The Functions of the Skeletal SystemBone ClassificationBone StructureBone Formation and DevelopmentFractures: Bone RepairExercise, Nutrition, Hormones, and Bone TissueCalcium Homeostasis: Interactions of the Skeletal System and Other Organ SystemsSKELETAL SYSTEM


Im all about the osseous tissues.

Thats why I play the Trom-bone.3

Osseous Tissue and the Skeletal StructureThe skeletal system includes:Bones of the skeleton and associated cartilagesLigaments and other connective tissues that stabilize and/or connect them

4Primary Functions

Framework: support the bodys muscle fat, and skin (soft tissues). Protection: Surround vital organs to protect themExamplesSkull that surrounds brain Ribs that protect heart and lungs. Levers: attach to muscles to help provide movement Produce blood cells: produce red and white blood cells and platelets.Storage: store most of bodys calcium, supply blood 5

Structure of boneMatrix of Bone:

-Combination of the two provides strong bones which are somewhat flexible and resistant to shattering.2/3 of bone weightis calcium phosphate 1/3 of bone weight is collagen fibers

6Cells in BonesTermschondro refers to cartilagechondrocyteendochondralperichondriumosteo refers to boneosteogenesisosteocyteperiostiumblast refers to precursor cell or one that produces somethingosteoblastcyte refers to cellosteocyteOsteocytes= mature bone cellsrecycle the calcium salts in the matrix around themparticipate in the repair of damaged bone

9Osteoblasts= responsible for the production of new bone. (osteogenesis) Elevated local concentrations of calcium phosphate favorable for calcification

Osteoclasts= giant cells with 50 or more nuclei. Derived from circulating monocytes (phoagocytic white blood cells) Important in the regulation of calcium and phosphate concentrations in body fluids

Osteoclast dissolving boneOsteoprogenitor= mesenchymal cells that maintain populations of osteoblasts and play an important role in fracture repair


Classification of Bones By ShapeLong Bones- A long bone is one that is cylindrical in shape, being longer than it is wide. Long bones function as levers; they move when muscles contract.Examples: humerus, ulna, radius, femur, tibia, fibula).Keep in mind, however, that the term describes the shape of a bone, not its size.

Flat Bones- typically thin and often curved. Serve as points of attachment for muscles and often protect internal organs.Examples include the cranial (skull) bones, the scapulae (shoulder blades), the sternum (breastbone), and the ribs. Flat bones

Short Bones- Short bones areapproximately equal in length, width, and thicknessExamples:The bones in thewristandankle

Irregular Bones- Bones that do not fall into the category of long, short, or flat are considered irregular bones. Examples:Thevertebraeand some of theskullbones are irregular.

Sesamoid bones- are small and round, and are located in tendons.Examples: patellae

How Many Bones Does an Adult Have?1920620How Many Bones Does a New Born Baby Have?2127022Divisions of the skeletal system24Creates the central axis of the body

Includes:SkullThoraxVertebral column

Contains 80 bones (~40% of skeleton)Axial Skeleton(Anterior)


Skull, Pelvis, and Vertebral columns are STRUCTURESNOT BONES!

Appendicular Skeleton26

126 bonesThe bones of the limbs The pectoral girdle The pelvic girdle2627Vertebral ColumnBackboneCentral axis of skeleton5 regions:Cervical vertebrae (C1-C7)Thoracic vertebrae (T1-T12)Lumbar vertebrae (L1-L5)Sacral (S)Coccygeal bone (CO)Different regions have special characteristics however all have common features*NOTE THE vertebrae numbering/identification!**HINT! HINT!**


2829Ribs & Costal Cartilages12 pairs (24 total)One pair articulated with each thoracic vertebrae7 True ribs (T1-T7) Attach to sternum via cartilage (vertebrosternal ribs)5 False ribs (T8-T12) Do not directly attach to sternum (vertebrocondial ribs)2 Floating ribs (T11-T12) SUB-TYPE OF FALSE RIBNot attached to sternum at all (vertebral ribs)2930

Upper Limb: Wrist & HandWrist region between forearm and hand8 carpalsHand attached to carpals5 metacarpals5 digitsNumbered 1-5 starting with thumb3 phalanges per finger (2 on thumb)Proximal; Medial; Distal


Sutures- Immovable joints which tie bones firmly together with denser fibrous connective tissue

3132SuturesLamboidal ()- Joins Parietal to OccipitalCoronal(crown)-Joins Parietal to frontalSagittal- joins the two parietal platesSquamosal (scale-like)- Joins temporal to occipital and parietal

32Bone MarkingsBulges, depressions, and holes that serve as sites of attachment for muscles, ligaments, and tendons, joint surfaces, conduits for blood vessels and nerves.

Bone Structure

Long BoneFlat Bone36

Bone Structures37Compact BoneOsteon = the functional unit of mature compact bone. (aka Haversian systems/canals)Within osteon, osteocytes are arranged in concentric layers around the central canal.Central Canals run parallel to the surface of the bone, contain one or more blood vessels.


Nutrients diffuse from vessels in central canalAlternating direction of collagen fibers increases resistance to twisting forces Isolated osteon:

Spongy BoneMatrix of spongy bone:Forms supportive mesh called trabeculaeSeem to align along stress linesHas no osteons or blood vessels. Nutrients reach osteocytes by diffusion40

Gross anatomy of bones

Diaphysis is the tubular shaft that runs between the proximal and distal ends of the boneMedullary cavity- The hollow region in the diaphysis, which is filled with yellow marrow. The walls of the diaphysis are composed of dense and hard compact bone.

Epiphysis (plural = epiphyses)- The wider section at each end of the bone, filled with spongy bone.Red marrow fills the spaces in the spongy bone.

Epiphyseal plate (growth plate)- narrow area where the epiphysis meets the diaphysis .Made of a layer of hyaline (transparent) cartilage in a growing bone.When the bone stops growing in early adulthood (approximately 1821 years), the cartilage is replaced by osseous tissue and the epiphyseal plate becomes an epiphyseal line.

The outer surface of the bone is covered with a fibrous membrane called the periosteum (peri- = around or surrounding). The periosteum contains blood vessels, nerves, and lymphatic vessels that nourish compact bone.


The medullary cavity has a delicate membranous lining called the endosteum where bone growth, repair, and remodeling occur. (endo- = inside; oste- = bone),

Tendons and ligaments also attach to bones at the periosteum. The periosteum covers the entire outer surface except where the epiphyses meet other bones to form joints.

In this region, the epiphyses are covered with articular cartilage, a thin layer of cartilage that reduces friction and acts as a shock absorber.

Bone Development and Growth

52Determines the size and proportions of our body

Starts @ 6weeks (cartilaginous) Ends @ ~25 years

Growth of the skeleton


Sultan Ksen2.51m (8ft 3in) He Pingping74cm (2 ft 5 in) 54Growth of the skeleton Ossification= Formation of bone

Calcification= deposition of calcium salts within a tissue

552 forms of Bone Growth

Intramenbranous Ossification deposition of bony matrix in connective tissue membranes

Endochondral Ossification replacement of cartilage by bone.56

57Endochondral Ossification

Cartilage cells become enlarged in ossification centersLong bones have three centers:1 at each end (epiphyses)1 at the midpoint of diaphysis (shaft)Enlarged cells soon break down leaving spaces filled by osteoblasts (bone forming cells)While organic components of bone are being formed, minerals are being deposited and blood vessels branch throughout the newly forming boneEventually osteoblasts become osteocytes


Endochondral ossificationStages 1-3 during fetal week 9 through 9th month Stage 4 is just before birthStage 5 is process of long bone growth during childhood & adolescence Intramembranous OssificationOsteoblasts deposit matrix materials in the form of calcium saltsOsteoblasts become osteocytes

60Dynamic Nature of BoneRemodeling- components of bone matrix are continually being recycled and renewed throughout life as part of normal bone maintenance.Young adults remodel 1/5 (20%) of the adult skeleton per year

61Dynamic Nature of BoneRemodeling- components of bone matrix are continually being recycled and renewed throughout life as part of normal bone maintenance.

Young adults remodel 1/5 (20%) of the adult skeleton per year

62Diseases and Disorders.Bones are adaptable, their shapes reflect the forces applied to themExercise Effects on Bone

Heavily stressed bones become thicker and stronger, bones not subject to ordinary stresses will become thin and brittle

64Moderate amounts of physical activity and weight bearing activities are essential to stimulate normal bone maintenance and maintain adequate bone strength.

Exercise Effects on Bone65

Bone markings reflect the stresses

Fracture repairBones may crack or break if subjected to extreme loads, sudden impacts, or stressed from unusual directions.Fracture categories:Displaced/Non-DisplacedOpen/Closed.

68Displaced/ Non-DisplacedDisplaced fracture- bone ends are not lined up straight.

Non-Displaced fracture- bone maintains its proper alignment.

69Open/ClosedClosed fracture- bone breaks but no open wound or puncture in the skin.

Open fracture- bone breaks throug