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PART 1: BONESChapter 6
THE SKELETAL SYSTEM
a connective tissue18% of weight of human bodySkeletal System includes bones &
cartilagePart 1: BonePart 2: Axial SkeletonPart 3: Appendicular SkeletonPart 4: Joints
Bone
FUNCTIONS1. SUPPORT skeleton serves
as structural framework by supporting soft tissues & providing attachments for tendons of muscle
2. PROTECTIONProtects most
important soft tissue organs from injury
FUNCTIONS3. MOVEMENTSkeletal muscles
attach to bones, when the muscle contract the bones move
4. MINERAL HOMEOSTASIS
Bone stores calcium, phosphorus which both help make bone strong
If body needs these minerals bone releases them
FUNCTIONS5. BLOOD CELL
PRODUCTIONred bone marrow
produces RBCs, WBCs, & platelets
6. TRIGLYCERIDE STORAGE
yellow bone marrow stores triglycerides (chemical energy reserve)
Axial Skeletonskullvertebral columnrib cagehyoid
Bones that make up the limbs and their girdles (bones that hold limbs to trunk)
Classification of the Skeletal System
Appendicular Skeleton
Classification of the Skeletal System
Long Boneslonger than they are
wideshaft with expanded
endsbone(s ) of upper
arm, lower arm, digits, thigh, lower leg
roughly cubitalbones on ankle and
wrist
Classification of Bones
Short Bones
Flat Bonesthin, flat bones with
bit of a curvesternumscapularibsmost skull bones
do not fit into other categories
vertebraehip bones
Classification of Bones
Irregular Bones
Classification of Bone TissueCompact Bone
outside layer of all bones
Spongy Boneinside certain bones
has few spaces strongest form of bonebeneath periosteum of all boneprovides protection & support and
resists stresses produced by weight & movement
TYPES of BONE: COMPACT BONE
OSTEON:aka Haversian Systemsrepeating units thru out compact boneeach one has central canal with
concentrically arranged lamellae, lacunae (filled with 1 osteocyte)
aligned in same direction along lines of stress
space between osteon filled with interstial lamellae
Parts of Compact Bone
absence of osteonsmade of lamellae arranged in
irregular columns called trabeculaeappears spongy but hardmakes up most of inside of short, flat,
or irregular bones & epiphysis of long bones
lighter than compact boneFunction: support & protect red bone
marrow
Spongy Bone Tissue
Spongy Bone
Structure of Bone: Long Bones1. DIAPHYSIS: bone’s shaft or
body: the long cylindrical, main portion of the bone
2. EPIPHYSIS:distal & proximal
ends of the bone
Structure of Long Bones3. METAPHYSIS:Region in mature
bone where diaphysis meets epiphysis
in growing bone include metaphyseal plate (hyaline cartilage that allows bone to grow in length)
4. ARTICULAR CARTILAGE
hyaline cartilage covering part of epiphysis involved in joint
reduces friction & absorbs shock @ freely movable joints
Metaphysis
Structure of Long Bones5. PERIOSTEUMtough , dense,
irregular CT surrounds bone wherever it is not covered by hyaline cartilage
helps in repair of fractures
attachment pt for ligaments
6. MEDULLARY CAVITY
aka Marrow Cavity
space w/in diaphysis that contains yellow bone marrow in adults
Periosteum & Marrow Cavity
Structure of Long Bones7. ENDOSTEUMthin membrane
that lines marrow cavity
contains 1 layer of bone-forming cells and CT
red bone marrowfound :newborns: in all areas of spongy boneadults: most long bones medullary cavity with
yellow marrow (fat) extends through diaphysisblood cell production only in head of femur &
humerusyellow marrow to hematopoietic marrow if
person becomes very anemic and needs more blood cells than can make in head of femur & humerus
Hematopoietic Tissue in Bone
Table
6.1
Bone Markings
Bones are hard due to calcification: calcium carbonate & other minerals (Mg, F, K, S) form crystals around collagen fibers
bone hardness depends on crystallized inorganic mineral salts
bone flexibility depends on collagen fibers
HISTOLOGY of BONE
1. OSTEOGENIC CELLS Stem cells from mesenchyme (origin
of all CT) only bone cells to divide
Types of Bone Cells
2. OSTEOBLASTSbone-building cellssynthesize & secrete collagen fibersinitiate calcification
Types of Bone Cells
3. OSTEOCYTESmature bone cellsmain cells in bonemaintain exchange of nutrients &
wastes with blood
Types of Bone Cells
4. OSTEOCLASTShuge cells that form by merging of
many (50)monocytesin endosteumruffled border faces bone surface:
releases lysosomal enzymes & acids that digest underlying bone (bone resorption): part of normal maintenance, growth, development, & repair of bone
Types of Bone Cells
Osteoclasts
Most bones are formed b/4 birth but each one continually renews itself for rest of life
~5% of bone being remodeled @ any given time
Bone Remodeling is the ongoing replacement of old bone tissue by new bone tissue1. Bone Resorption2. Bone Deposition
Bone Remodeling
Removal of minerals & collagen fibers from bone by osteoclasts
Results in destruction of bone extracellular matrix
Bone Resorption
Addition of minerals & collagen fibers to bone by osteoblasts
Bone Deposition
1. Minerals Ca, P, F, Mg, Fe, Mn
2. Vitamins C needed to make collagen fibers & for
differentiation osteoblast osteocyte E & B12 needed for protein synthesis
3. Hormones IGF’s in childhood (insulin-like growth
factors) estrogens & androgens important in
puberty
Factors Affecting Bone Growth &
Remodeling
https://www.youtube.com/watch?v=0dV1Bwe2v6c
https://www.youtube.com/watch?v=5gpysdG1HoE
Bone Remodeling
Fracture: any break in a boneFractures named by:
severityshape or position of fracture lineperson who 1st described it
Fracture & Repair of Bone
Types of Fractures of Bone
Types of Bone Fractures
Types of Bone Fractures
Types of Bone Fractures
Fracture Repair
Bone is body’s main reservoir for calcium (stores 99% of total body Ca)
Normal blood level Ca 9 -11 mg/100mL
Calcium important for:Muscle contractionNerve impulsesBlood clottingMany enzymes require Ca++ as
cofactor
Calcium Homeostasis
2 hormones control Ca in/out bone:1. Calcitonin
Decreases blood Ca levels by putting more Ca into bone
2. Parathyroid Hormone (PTH) Increases blood Ca levels by taking
Ca out of bone (increasing osteoclast resorption)
Control of Calcium
1. Osteoporosis Condition of porous bones
(resorption > deposition) Causes: deficient Ca in diet USA: > 1 million fractures (hip,
wrist, vertebrae) & afflicts 30 million Americans
Decreased stature, hunched back, bone pain
Homeostatic Imbalances in Bone
traditionally tx’d with:weight-bearing exercisecalcium & Vit Destrogen replacement
Treatment of Osteoporosis
Biphosphonates : decrease osteoclast activity & partially reverse
osteoporosis in the spineSERMS:
“selective estrogen receptor modulators “ mimic estrogen’s beneficial bone-sparing properties without targeting the uterus or breasts
Statins: (lower serum cholesterol) have been found to
also increase bone mineral density (up to 8% over 4 yrs)
Denosubmab: (monoclonal aby drug)↓ fractures& improves bone density
Treatment of Osteoporosis
http://highered.mheducation.com/sites/0072495855/student_view0/chapter6/animation__osteoporosis.html
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