Ch. 6 and 7Skeletal System

Anatomy and Physiology

1. Support1. Not just place to hang muscles – need bones for framework2. Muscles need something to pull against3. Site for organs and soft tissues

2. Storage of minerals and lipids1. Osmotic concentration/ reaction rate/ coenzymes2. Calcium, potassium, sodium, magnesium, carbonate, phosphate3. Lipids in yellow marrow

3. Blood cell production1. Red bone marrow – inner cavity of bones2. Makes red blood cells, white blood cells and other components of blood

4. Protection1. Ribs protect heart and lungs2. Skull enclosed brain, etc

5. Leverage1. Movement of skeletal muscles depends on leverage against skeleton

6.1 Functions of the Skeletal System

1. Sutural 1. Found in skull; they look like they have been ‘sutured ‘ or

sewn together2. Irregular

1. Complex shapes; vertebrae, pelvis and skull3. Short bones

1. Small and boxy; wrist and ankle4. Flat bones

1. Flat and thin; skull, sternum, ribs, scapulae/ protection and lots of surface area to anchor muscle

5. Long bones1. Long and slender; arms, legs, fingers, toes

6. Sesamoid bones1. Vary in number, found in tendons, disc or seed shaped; knee

cap

6.2 Bone Shapes: shape or internal organization

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Figure 6-1 A Classification of Bones by Shape

Sutures

Suturalbone

Vertebra

Carpalbones

Parietal bone External table

Internaltable

Diploë(spongy

bone)

Humerus

Patella

Sutural Bones Flat Bones

Long Bones

Sesamoid Bones

Irregular Bones

Short Bones

Surface structures known as landmarks Elevations or projections

◦ These are sites for tendons and ligaments to attach and bones to articulate (joints = articulations)

Depressions, grooves and tunnels◦ Places where blood vessels or nerves ran along

side a bone Used to determine age, gender, size and

appearance of individual (skeletal remains)

Bone markings

Diaphysis – length of long bone◦ Wall is compact or dense bone; sturdy◦ Center is medullary cavity; marrow

Epiphysis – ‘end’◦ Spongy bone aka cancellous or trabecular bone ◦ Open network like lattice ◦ With thin cortex or covering

Metaphysis – ‘between’ where diaphysis meets the epiphysis

Bone structure – page 172 *

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Figure 6-2 Bone Structure

Epiphysis

Diaphysis(shaft)

Metaphysis

Medullarycavity

Compactbone

Spongybone

Epiphysis

Metaphysis

Cortex(compact bone)

Diploë(spongy bone)

The structure of a flat bone(the parietal bone)

The structure of a representativelong bone (the femur) inlongitudinal section

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Table 6-1 An Introduction to Bone Markings

SinusTrochanter

Head

Neck

Facet

Tubercle

CondyleFemur

Fissure

Ramus

Foramen

Process

Skull

Tubercle HeadSulcusNeck

Tuberosity

Fossa

Trochlea

CondyleHumerus

Crest

Fossa

Spine

Line

ForamenRamus

Pelvis

6.3 Bone or osseous tissue = supporting connective tissue; matrix, fibers and cells Matrix

◦ Dense with calcium salts Ca3(PO4)2◦ and collagen fibers (like rebar in concrete)◦ Cells are in pockets called lacunae◦ Organized around blood vessels◦ Canaliculi are passages through matrix branching

between lacunae and blood vessels◦ Periosteum – fiberous (outer) and cellular (inner)

layer that covers bone surfaces Cells

◦ Osteocytes, osteoblasts, osteoprogenitor cells and osteoclasts

Osteocytes◦ Bone cells◦ Most common◦ 1 per lacuna, surrounded by layers of lamellae◦ Can not divide◦ Neighboring osteocytes are linked by gap junctions through the canaliculi◦ Maintain mineral content and help to repair fractures◦ Can become other cell types

Osteoblasts◦ Produce new matrix

Osteoprogenitor cells◦ Produce osteoblasts that could repair a fracture

Osteoclasts ◦ Remove and recycle matrix as needed; “resorption”◦ 50 + nuclei◦ Very large◦ Come from marrow (stem cells) and not osteoprogenitor cells◦ Can make bones larger/stronger to match muscle mass or smaller

through disuse

Bone Cells

Compact bone / Spongy bone Compact bone

◦ Osteocytes are in concentric layers around a Haversian canal = osteon

◦ Lamella are in concentric layers (target like pattern)

◦ Thickest were there is stress to bear weight Femur bears 15 X body

weight before breaking – when force is end to end; breaks when force is from side

Spongy bone◦ Lamella not in osteons◦ Bundles of fibers =

trabeculae◦ Red marrow

Blood cell formation◦ Yellow marrow

Adipose/ energy reserve◦ Locations without stress;

not as dense (<weight)

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Figure 6-6 The Structure of Spongy Bone

Trabeculae ofspongy bone

Canaliculi openingon surface

Endosteum Lamellae

Figure 6-5 The Structure of Compact Bone

VenuleCapillaryPeriosteum

Circumferentiallamellae

Osteons

Perforatingfibers Interstitial

lamellae

Concentriclamellae

Trabeculae ofspongy bone(see Fig.6–6)

Vein

Artery ArterioleCentralcanal

Perforatingcanal

The organization of osteons andlamellae in compact bone

The orientation of collagenfibers in adjacent lamellae

Collagenfiberorientation

Endosteum

Centralcanal

Concentriclamellae