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Skeletal System1. Honors Anatomy c opy version. Bone . a combination of CT, epithelial & nervous tissues 18% of weight of human body Skeletal System includes bones & cartilage Part 1: Bone Part 2: Axial Skeleton Part 3: Appendicular Skeleton Part 4: Joints . FUNCTIONS. SUPPORT - PowerPoint PPT Presentation
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Skeletal System1
Honors Anatomycopy version
• a combination of CT, epithelial & nervous tissues
• 18% of weight of human body• Skeletal System includes bones &
cartilage• Part 1: Bone• Part 2: Axial Skeleton• Part 3: Appendicular Skeleton• Part 4: Joints
Bone
FUNCTIONS1. SUPPORT• skeleton serves
as structural framework by supporting soft tissues & providing attachments for tendons of muscle
2. PROTECTION• Protects most
important soft tissue organs from injury
FUNCTIONS3. MOVEMENT• Skeletal 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
Parts of a long bone1. Diaphysis:
shaft or body; the long cylindrical portion of the bone
2. Epiphysis:distal & proximal ends of bone
Parts of a long bone3. Metaphysis:• region between
diaphysis & epiphysis
• in growing bone includes metaphyseal plate (hyaline cart. that allows bone to lengthen
4. Articular Cartilage:
• layer of hyaline cartilage covering part of epiphysis where bone forms a joint with articulating bone
metaphysis
Structure of Long Bones
7. ENDOSTEUM• thin membrane
that lines marrow cavity
• contains 1 layer of bone-forming cells and CT
Histology of bone• bone consists of widely
separated cells surrounded by large amts extracellular matrix
• *bone is hard due to crystallized inorganic mineral salts
• *bone is flexible due to collagen
1. OSTEOGENIC CELLS• Stem cells from mesenchyme (origin
of all CT)• only bone cells to divide
Types of Bone Cells
2. OSTEOBLASTS• bone-building cells• synthesize & secrete collagen fibers• initiate calcification
Types of Bone Cells
3. OSTEOCYTES• mature bone cells• main cells in bone• maintain exchange of nutrients &
wastes with blood
Types of Bone Cells
4. OSTEOCLASTS• huge cells that form by merging of
many (50)monocytes• in endosteum• ruffled 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
Types of bone (2)1. Compact bone– few open spaces – outer bone layer of all bones
2. Spongy bone– inside bones
• strongest form of bone• beneath periosteum of all bone• functions: – protection & support – resists stresses produced by
weight & movement
COMPACT BONE
• OSTEON:– aka Haversian Systems– repeating units thru out compact
bone– each one has central canal with
concentrically arranged lamellae (rings), lacunae (filled with 1 osteocyte)
– aligned in same direction along lines of stress
– space between osteon filled with interstial lamellae
Parts of Compact Bone
Compact bone
• absence of osteons• made of lamellae arranged in
irregular columns called trabeculae• makes up most of inside of short, flat,
or irregular bones & epiphysis of long bones
• lighter than compact bone• Function: – support & protect red bone marrow
Spongy Bone
Spongy bone
Bone growth1. longer:• @ epiphyseal plate1. wider:• called appositional growth• periosteal osteoblasts on outer
surface of bone• osteoclast remove compact
bone inner border
Bone growth: longer
Bone growth: wider
• 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 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 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
• Fracture: any break in a bone• Fractures named by:– severity– shape or position of fracture line– person who 1st described it
Fracture & Repair of Bone
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 contraction–Nerve impulses– Blood clotting–Many 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 bone2. 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
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