2 Functions of the System: ProtectionSupportAllows for body movementProduces blood cellsStores minerals
3 Introduction to the Skeletal System Components of the Skeletal System= bones, cartilage, ligaments, and tendonsSome definitions:Cartilage= somewhat rigid, covers the surfaces of bones in/near jointsTendons= band of strong tissue that connects bones to muscleLigaments= band of strong tissue that connects bone to boneAxial Skeleton=Head to pelvis, main bodyAppendicular Skeleton= Everything else
4 Introduction to BONEA. Bones are very active tissuesB. Each bone is made up of several types of tissues and so is an organ.C. Bone functions reflect the system
5 A. Support and Protection Bone Functions (the organ)A. Support and Protection1. Bones give shape to the head, thorax, and limbs.2. Bones such as the pelvis and lower limbs provide support for the body.3. Bones of the skull protect the brain, ears, and eyes.B. Body Movement1. Bones can act as levers.a. A lever has four components: a rigid bar, a pivot or fulcrum an object that is moved against resistance, and a force that supplies energy.C. Blood Cell Formation1. Blood cells begin to form through hematopoieses in the yolk sac; they are later manufactured in bone marrow.2. Two kinds of marrow occupy the medullary cavities of bone.a.Red marrow functions in the formation of red blood cells, white blood cells, and platelets,and is found in the spongy bone of the skull, ribs, sternum, clavicles, vertebrae, and pelvis.b. Yellow marrow, occupying the cavities of most bones, stores fat.D. Storage of Inorganic Salts1. The inorganic matrix of bone stores inorganic mineral salts in the form of calcium phosphate that is important in many metabolic processes.2. Calcium in bone is a reservoir for body calcium; when blood levels are low, osteoclasts release calcium from bone.3. Calcium is stored in bone under the influence of calcitonin when blood levels of calcium are high.4. Bone also stores magnesium, sodium, potassium, and carbonate ions.5. Bones can also accumulate harmful elements, such as lead, radium, and strontium.
6 General Bone Structure= Types of Bone Bones differ in size and shape, yet are similar in several ways.Long = longer than it is wideEpiphysis= end of a long bone; separated from the main part of the bone from immature cartilageDiaphysis= shaft of a long boneMedullary Cavity= hollow space running the length of the diaphysis; has blood, nerves, and marrowEpiphyseal Line= “Growth Plate”; Where the cartilage is converted to bone as it grows in lengthExamples: Upper and lower limbsShort = same length and widthCarpals tarsalsFlat = not wide; flat like a plateRibs, sternum, skull, scapulaeIrregular = not distinct shapeVertebrae, facial
7 More Bone Structure.. Long Bone in depth Parts 1. Expanded ends of bones that form joints with adjacent bones are called epiphyses.2. Articular cartilages (hyaline cartilage) cover the epiphyses.3. The shaft of the bone is the diaphysis.4. A tough layer of vascular connective tissue, called the periosteum, covers the bone and is continuous with ligamentsand tendons.5. A bone's shape makes possible its function; bony processes or grooves indicate places of attachment for muscles.6. Compact bone makes up the wall of the diaphysis; the epiphyses are filled with spongy bone to reduce the weight of the skeleton.7. The diaphysis contains a hollow medullary cavity that is lined with endosteum and filled with marrow.
9 More Bone Structure.. Flat, Short, Irregular Bones Flat bones No diaphyses, epiphysesSandwich of cancellous (spongy bone tissue) between compact bone tissueShort and Irregular boneCompact bone that surrounds cancellous bone tissue centerNo diaphyses and not elongated
10 Microscopic Structure of Bone Bone matrix (chemical components): non-living component of boneOrganic: collagen and proteoglycansInorganic: Calcium & PhosphateBone Tissue:Compact bone tissue: dense/hardSpongy bone tissue: porous ‘like a sponge’Bone cells= living part of boneStem cells or osteoprogenitor cellsOsteoblasts- make new bone; immature bone cellOsteocyte- mature bone cell; maintains tissueOsteoclasts- breaks down and re-absorbs of old, damaged, or diseased tissue boneUnlike compact bone, the osteocytes and intercellular material in spongy bone are not arranged around osteonic canals.
11 Microscopic Structure of Bone Compact bone tissueHaversian system—osteons (functional unit of tissue)Contain living bone cellsDelivery of nutrients & removal of wasteLamellaeLacunaeCanaliculiHaversian canalVolkmann’s canals
13 Microscopic Structure of Bone Spongy (Cancellous) BoneConsists of trabeculae (bony plates)Oriented along lines of stress
14 Bone Growth & Development CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.Bone Growth & DevelopmentA. Bones form by replacing connectivetissues in the fetus.B. Some form within sheetlike layers of connective tissue (intramembranous bones), while others replace masses of cartilage (endochondral bones).Intramembranous Bone Development1.The flat bones of the skull form as intramembranous bones that develop from layers of connective tissue.2.Osteoblasts deposit bony tissue around themselves.3. Once osteoblasts deposit bone are located in lacunae, they are called osteocytes.4. Cells of the membranous connective tissue that lie outside the developing bone give rise to the periosteum.*Basically it is when matrix gets deposited on the surface of existing bone, this causes a growth in diameter
15 Endochondral Bone Development 1. Most of the bones of the skeleton fall into this category.2. They first develop as hyaline cartilage models and are then replaced with bone.3. Cartilage is broken down in the diaphysis and progressively replaced with bone while the periosteum develops on the outside.4. Cartilage tissue is invaded by blood vessels and osteoblasts that first form spongy bone at the primary ossification center in the diaphysis.5.Osteoblasts beneath the periosteum lay down compact bone outside the spongy bone.6.Secondary ossification centers appear later in the epiphyses.7. A band of hyaline cartilage,the epiphyseal plate,forms between the two ossification centers.8.Layers of cartilage cells undergoing mitosis make up the epiphyseal plate.9.Osteoclasts break down the calcified matrix and are replaced with bone building osteoblasts that deposit bone in place of calcified cartilage.10. Epiphyseal plates are responsible for lengthening bones while increases in thickness are due to intramembranous ossification underneath the periosteum.11. A medullary cavity forms in the region of the diaphysis due to the activity of osteoclasts.* Basically, occurs in the epiphyseal plates, the cartilage is covered to bone as the cartilage becomes calcified (filled with calcium) causing it to get hard. The growth occurs from the middle outward to increase length (growth in height)
18 Factors Affecting Bone Growth NutritionVitamin DNecessary for absorption of Ca from intestinesInsufficient causes rickets and osteomalaciaVitamin CNecessary for collagen synthesis by osteoblastsDeficiency results in scurvyHormonesGrowth hormone from anterior pituitaryThyroid hormone required for growth of all tissuesSex hormones as estrogen and testosterone
19 Homeostasis of Bone ‘Remodeling Bone’ REQUIRES only certain bone cell Review of Types of Bone Cells:Process: Osteoclasts tear down and osteoblasts build bone throughout the lifespan with the processes of resorption and deposition, with an average of 3% to 5% of bone calcium exchanged annually.OsteoblastOsteoclastOsteocyte
20 How does bone repair from injury? Day of AccidentBroken Bone2-3 DaysA clot forms in the damaged area4 to 6 WeeksBlood Vessels and cells invade the clot and produce a fibrous network between the broken bones which is a callusAfter 6 WeeksOsteoblasts enter callus and begin to form spongy bone or cancellous boneWeeks to MonthsSpongy bone is slowly remodeled to form compact boneBone RepairedBone healed stronger around the surrounding area