Chapter 7Chapter 7Skeletal SystemSkeletal System

Functions of Skeletal Functions of Skeletal System: System:11. . Support Support 2. 2. ProtectionProtection3.3.4. 4. Stores inorganic Stores inorganic materialsmaterials

Classification – bones Classification – bones classified by shape:classified by shape:

1. Long1. Long 2. 2. 3. 3. Flat Flat 4. 4. 5. Sesamoid5. Sesamoid

Structure of Long BoneStructure of Long Bone

Epiphysis- Epiphysis- Epiphyseal disk (line)-growth plateEpiphyseal disk (line)-growth plateDiaphysis- Diaphysis- Medullary cavity-hollow chamber in centerMedullary cavity-hollow chamber in centerSpongy bone- cancellous bone, found Spongy bone- cancellous bone, found mainly in epiphysismainly in epiphysisCompact bone-Compact bone-Periosteum-tough, vascular coveringPeriosteum-tough, vascular coveringEndosteum- membrance of bone forming Endosteum- membrance of bone forming cellscellsArticular cartilage-Articular cartilage-

Structure of a Long Bone

• Red marrow-

• Yellow marrow- stores

fats, no blood cell

production.

Compact vs. Spongy Bone

• Perforating(Volkmann’s)

canal- Connects central

canals• Trabeculae-

• Canaliculi- canals btwn

osteocytes• Osteocyte-Bone cells• Lacunae-

Compact vs. Spongy Bone

Bone Development – 2 Types:

1. Intramembranous ossification (changing cartilage to bone) (ex. - skull)

• layers of undifferentiated connective tissue appear at sites of future bone

•

• osteoblasts become osteocytes (mature bone cells) when completely surrounded by a bony matrix

• Connective tissue on surface forms the periosteum

•

Intramembranous Ossification

Intramembranous Ossifiction

2. Endochondral ossification (remainder of skeleton)

• Hyaline cartilage models form at sites of future bone

• Cartilage cells degenerate over time

•

• osteoblasts become osteocytes when completely surrounded by a bony matrix

Endochondral Ossification

Bone Development

• In a long bone, hyaline cartilage is replaced by bony tissue in the center of the diaphysis first (primary ossification center)

• Bone develops from this point towards the end of the bone

•

Bone Development

Growth of Bones• Epiphyseal disk – area of

growth; separates epiphysisfrom diaphysis; 4 layers:1. Resting cells –

2. Reproducing cells - as they reproduce, they lengthen the bone

1.

Growth of Bones

3. Mature cells –

4. Degenerating cells &

osteoblasts depositing

bony tissue

Epiphyseal disk

1. Radial growth plate→

2. Fracture – distal

end of radius →

Digital growth

plate (in fingers)

(2 ½ yr. old)→

Fractures

• Greenstick-

• Fissuered- inc. longitudinal break

• Comminuted-complete, fragments bone

• Transverse-• • Oblique- complete at angle

other than right angle• Spiral-

Fracture Repair

• 4 stages– Blood escapes from blood

vessels and from hematoma.

– Spongy bone forms near blood vessels, fibrocartilage forms in distant regions (within days to weeks)

– Bony callus forms from cartilaginous callus similar to bone formation

– Osteoclasts remove excess bone to restore to original

Factors Affecting Bone Growth(Nutrients)

Deficiency Effect

Vit D (for Ca absorption)

Vit A (for osteoblast &osteoclast activity)

Vit C (for collagensynthesis)

Rickets/Osteomalacia

Homeostasis of Bone Tissue

Factors Affecting Bone Growth(Hormones)

Deficiency EffectPituitary growth Pituitary dwarfism hormone (excess – pituitary (stimulates cell division gigantism/acro-in the epi. disks) megaly)Thyroid hormone premature disk(stimulates cartilage ossification-growthreplacement in disk) stunted

Pituitary dwarfism

Acromegaly

Yao Defen is 34 yrs. old &The world’s tallestfemale at 7ft. 8 in!!

Factors Affecting Bone Growth(Hormones & Exercise)

Deficiency EffectSex hormones stimulate ossifi-(cause growth of cation of disks;long bones; estrogen stop bone lengthstronger than androgen)Physical stress bone thins &

weak-(stimulates bone width; ens; atrophyhypertrophy)

2 divisions of skeleton:

1. Axial –

2. Appendicular –

pectoral & pelvic girdles, upper & lower limbs

Human Skeleton – composed of 206 bones (extra – sutural)

Axial vs. Appendicular Skeleton

Surface Markings on Bone

• Surface of bones have various structural features for specific functions

• Depressions & Openings:ForamenMeatusSinus

Foramen

Opening for b.v., nerves, ligaments (ex.-foramen magnum)

Meatus

Tubelike passageway (ex.-external auditory

meatus)

Sinus

Cavity within a bone

(ex.-frontal sinus)

Surface Markings on Bone

• Processes that Form Joints:

Condyle

Head

Facet

Condyle

Rounded process for

articulation w/another

bone (ex. – mandibular

condyle)

Head

An enlargement at the end of a bone (ex.-head of femur)

Facet

Small, nearly flat surface where 2 bones articulate (ex.-vertebral facet)

Surface Markings on Bone

• Processes that Connective Tissue Attaches To:

Tuberosity

Spine

Trochanter

Crest

Process

Tuberosity

Knoblike process (ex.-ischial tuberosity)

Spine

Thornlike ridge or projection (ex.-spine of scapula)

Trochanter

Large process or projection (ex.-trochanter of femur)

Crest

Ridgelike projection (ex.-iliac crest)

Process

Prominent projection on a bone

(ex.-spinous process)

Surface Markings – Misc.

Suture - Interlocking lines where bones meet (ex.-coronal suture)