SKELETAL SYSTEM

PART 1: BONE Honors Anatomy & Physiology

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

FUNCTIONS5. BLOOD CELL

PRODUCTION red bone marrow

produces RBCs, WBCs, & platelets

6. TRIGLYCERIDE STORAGE

yellow bone marrow stores triglycerides (chemical energy reserve)

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

ARTICULAR CARTILAGE

STRUCTURE OF LONG BONES

5. PERIOSTEUM tough , 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

MEDULLARY CAVITY

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

OSTEOCLASTS

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 Systemsrepeating 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:

severityshape or position of fracture line

person 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 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