5 Functions of the Skeleton Support for the bodyour internal frameworkProtection of soft organsex. skull brainrib cage lungs & heartvertebrae spinal cord
6 Functions of the Skeleton Movementskeletal muscles use the bones as levers to move the body & its partsStorageBone tissue stores minerals, such as calcium and phosphorusFat is stored in yellow marrow
7 Functions of the Skeleton 5) Blood Cell Formation Hematopoiesis occurs in red marrowThe adult skeleton iscomposed of 206 bones!
8 Classification of Bones Bones can be classified based on their SHAPE or HISTOLOGICAL ORGANIZATION (STRUCTURE)
9 Classification of Bones: Shape Long bonesTypically long & slenderShaft with heads at both endsMostly compact boneExamples: arms, legs, fingers, toes
10 Classification of Bones: Shape 2) Short bonesTypically box- or cube-shapedMostly spongy boneExamples:wrists & ankles
11 Classification of Bones: Shape 3) Flat bonesthin, flattenedusually curvedthin layers of compact bone surrounding spongy boneribs
12 Classification of Bones: Shape 4) Irregular bonesDo not fit in other categoriesExamples:VertebraeHip bones
15 Types of Bone (Osseous) Tissue All bones contain both types of bone tissue. Their relationship & proportions vary depending on bone shape.Compact Bonedense, smooth & homogenousSpongy Boneopen network of struts & plates
16 Gross Anatomy of a Long Bone diaphysisa) tubular shaftb) compact boneepiphysisa) ends of the boneb) mostly spongy bone
19 Structures of a Long Bone periosteuma) outside covering ofthe diaphysisb) fibrous connectivetissue membraneSharpey’s fibersconnect periosteum tothe underlying bone
20 Structures of a Long Bone 3) Arteriessupply the osteocytes w/nutrients & oxygenArticular Cartilagea) covers the epiphysesb) made of hyalinecartilagec) decreases friction atthe joints
21 Structures of a Long Bone Medullary Cavitya) Cavity of the shaftb) bone marrow consists ofloose connective tissue- yellow marrow(fat storage) in adults- Contains red marrow(for blood cell formation)in infantsc) endosteumlayer of cells lining the cavity
23 Bone Histology Osseous tissue (bone) is a type of connective tissue Four Characteristics of Bone1) bone matrix is very dense & contains calciumsalts2) contains bone cells (osteocytes) in pocketscalled lacunae
24 Let’s take a look at each characteristic… Bone HistologyFour Characteristics of Bone cont…3) Canaliculi allow for gas exchange and diffusionof nutrients and waste products4) except at joints, bones are covered by thea periosteumLet’s take a look at each characteristic…
25 Bone Histology: Matrix 2/3 of bone matrix is calcium phosphate,Ca3(PO4)2 w/ calcium hydroxide, forms crystals of hydroxyapatite, which incorporate other calcium salts & minerals into the matrix1/3 of bone matrix is collagen fibersOnly 2% of bone mass comes from cells
26 Bone Histology: Cells There are 4 types of bone cells osteocytes are the most commonOsteocytes sit in a pocket-like structure called a lacuna (lacunae, plural)Lacunae are arranged in concentric rings, or layers of matrix, called lamellae (lamella, singular)
27 Bone Histology: Canaliculi Canaliculi (tiny canals)Radiate from the central canal (blood vessels) to lacunaeForm a transport system between osteocytes and between the central canal & osteocytes
32 Compact Bone Osteon (Haversian System) osteon – the basic unit of compact boneOrganization of an Osteona) Osteocytes are arranged in concentriclamellae around a central (Haversian)canal containing blood vessels
33 Compact Bone Organization of an Osteon cont… b) Central (Haversian) canalopening in the center of an osteoncontaining blood vessels and nervesc) Perforating (Volkman’s) canalperpendicular to the central canal alsocontaining blood vessels and nerves
39 Spongy Bone: Yellow Marrow In some bones,spongy boneholds yellowbone marrowwhich is used tostore fat
40 Spongy Bone: Red Marrow The space betweentrabeculae is filled withred bone marrow. Redmarrow forms red bloodcells and suppliesnutrients to osteocytes.
41 Bone Markings Surface features of bones that show… 1) Sites of attachment for muscles, tendons, andligaments2) Passages for nerves and blood vesselsCategories of bone markingsprojections or processes – grow out from the bone surfacedepressions or cavities – indentations
44 Bone Formation, Growth & Remodeling The structure of bone isspecialized for flexibility andtensile strength.
45 Bone Formation In embryos, the skeleton is primarily hyaline cartilage During fetal development, much of this cartilage is replaced by boneBy the end of the toddler years, cartilage remains only in isolated areas:- bridge of the nose- parts of ribs- articular cartilage (in the joints)- epiphyseal plates
46 Bone Formation The process of “bone formation” is called ossification. 1) Unless it is a flat bone, a hyaline cartilagemodel is covered with bone matrix byosteoblasts.osteoblasts - immature, bone-forming cellsOver time, the “cartilage bone” is enclosed in alayer of real bone (kind of like an arm in acast).
47 Bone FormationThe enclosed layer of hyaline cartilage is digested away by osteoclasts.osteoclasts - bone destroying cells; breakdown bone matrix forremodeling and release ofcalciumThe breakdown of the cartilage “model”leaves a medullary cavity in the bone.
53 Bone Growth Appositional growth increases the width of the bone. Osteoblasts in the periosteum add bone tissue to the surfaceAt the same time…Osteoclasts in the endosteum remove bonematrix from the inner surface.
54 In order for bones to retain normal proportions and strength as the body changes in size and strength, bones must constantly remodel.
55 Bone Remodeling1) Bones become thicker and form larger projections to increase strength for bulky muscles. When you lift its not just the muscles that have to respond!
56 Bone Remodeling2) When bones are not subject to normal stress/exercise, they atrophy (shrink, shrivel). Bone degenerates quickly! Up to 1/3 of bone mass can be lost in a few weeks of inactivity!
57 Bone Remodeling osteocytes) and bone recycling (by osteoclasts) must Bone building (byosteocytes) and bonerecycling (byosteoclasts) mustbalance
64 Hormonal Control 3) Other Hormones - growth hormone and thyroxine stimulate bone growth- estrogens and androgens stimulateosteoblasts- calcitonin (w/ PTH and calcitriol)regulate calcium and phosphate levels
66 Nutrition & Bone 1) Minerals A dietary source of calcium and phosphate salts, plus small amounts of Mg, F, Fe andMn
67 Nutrition & Bone 2) Vitamins - vitamin C needed (collagen synthesis & osteoblast differentiation)- vitamin A stimulates osteoblast activity- Vitamin K and B12 ( protein synthesis in bone)
68 Nutrition & BoneQuestions: 1. A pregnant woman is not getting enough calcium in her diet. How will her body respond? (hormone released, response) 2. Sally has a history of osteoporosis in her family. She includes many calcium-rich foods in her diet and takes a vitamin D supplement. How will her body respond? (hormone released, response)
70 Bone Fractures Types of bone fractures Closed (simple) fracture –break that does not penetrate the skinOpen (compound) fracture –broken bone penetrates through the skinBone fractures are treated by reduction (realignment of the bone) and immobilization
74 Bone Fracture Repair Step 1: Bleeding produces a clot (fracture hematoma)establishes a fibrous networkbone cells in the area die
75 Bone Fracture Repair Step 2: Callus Formation Cells of the endosteum andperiosteum divide andmigrate into fracture zonefibrocartilage“Calluses”stabilize the break
76 Bone Fracture Repair Step 3: Bone Formation Osteoblasts and osteoclastsmigrate to the area andmultiply.Osteoclasts deteriorate thefibrocartilage callus asosteoblasts replace it w/newbone tissue.This is now called abony callus.
77 Bone Fracture Repair Step 4: Bone Remodeling Osteoblasts and osteocytes remodelthe fracture for upto a year, reducingthe bone calluses