Chapter 7 Skeletal System

Functions of Skeletal System: 1. Support 2. Protection 3 Functions of Skeletal System: 1. Support 2. Protection 3. Produces blood cells 4. Stores inorganic materials

Classification – bones classified by shape: 1. Long 2. Short 3. Flat 4. Irregular 5. Sesamoid

Structure of Long Bone Epiphysis- expanded portion at end, forms joint. Epiphyseal disk (line)-growth plate Diaphysis- shaft of bone Medullary cavity-hollow chamber in center Spongy bone- cancellous bone, found mainly in epiphysis Compact bone-tightly packed tissue Periosteum-tough, vascular covering Endosteum- membrane of bone forming cells Articular cartilage-layer of hyaline cartilage on epiphysis of bone

Structure of a Long Bone Red marrow- formation of red blood cells, white blood cells and platelets. Found in flat bones and epiphysis Yellow marrow- stores fats, no blood cell production. Found in diaphysis

Compact vs. Spongy Bone Perforating(Volkmann’s) canal- Connects central canals Trabeculae-bony plates of spongy bone Canaliculi- canals btwn osteocytes Osteocyte-Bone cells Lacunae- space in bone containing osteocytes

Compact vs. Spongy Bone

Bone Structure Animation structure of bone animation

Osteoblast vs. Osteoclast Osteoblast- bone forming cells which deposit Calcium and Phosphorous into the dense collagen framework. Osteoclast- Large multinucleated cells formed from fusing white blood cells. Secrete an acid which breaks down the bony matrix Both work together over a person’s lifetime to remodel bone and allow for resorption on minerals.

Osteoblast vs osteoclast osteoblast osteoclast animation

Homeostasis of Bone Tissue

Bone Development – 2 Types: 1. Intramembranous ossification (changing cartilage to bone) (ex. - skull) layers of undifferentiated connective tissue appear at sites of future bone connective tissue cells differentiate into osteoblasts (cells that build bone) around blood vessels 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 form bone over cartilage osteoblasts become osteocytes when completely surrounded by a bony matrix

Ossification Animation

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 Secondary ossification centers appear in the epiphysis last.

Bone Development

Growth of Bones 1. Epiphyseal disk – area of growth; separates epiphysis from diaphysis; 4 layers: 1. Resting cells – closest to end; do not add length but act as anchor 2. Reproducing cells - as they reproduce, they lengthen the bone 1.

Growth of Bones 3. Mature cells – growing and accumulating Ca 4. Degenerating cells & osteoblasts depositing bony tissue

Epiphyseal Plate Video http://www.youtube.com/watch?v=RTx-Z0a9wvM

Epiphyseal disk Bones continue to lengthen until epi. disks are ossified (approx. 21 yrs. of age) Bones thicken through- out life as compact bone is added under peri- osteum Hyaline cartilage on ends remains

Bone Growth Video http://app.discoveryeducation.com/player/view/assetGuid/39B53919-B11C-4D2C-A92C-E030DF639351

Epiphyseal disk 1. Radial growth plate→ 2. Fracture – distal end of radius → Digital growth plate (in fingers) (2 ½ yr. old)→

Fractures Greenstick- incomplete break in convex surface Fissured- incomplete longitudinal break Comminuted-complete, fragments bone Transverse- complete break at right angle Oblique- complete at angle other than right angle Spiral- complete, caused by twisting of bone

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

Bone Fracture Video https://www.youtube.com/watch?v=MNkI6Of2PRs

Factors Affecting Bone Growth (Nutrients) Deficiency Effect Vit D (for Ca absorption) dehydrocholesterol soft bones (rickets/osteomalacia) Vit A (for osteoblast & osteoclast activity) slow bone development Vit C (for collagen synthesis) fragile bones

Rickets/Osteomalacia

Factors Affecting Bone Growth (Hormones) Deficiency Effect Pituitary growth Pituitary dwarfism hormone (excess – pituitary (stimulates cell division gigantism/acro- in the epi. disks) megaly) Thyroid hormone premature disk (stimulates cartilage ossification-growth replacement in disk) stunt ed

Pituitary dwarfism

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

Factors Affecting Bone Growth (Hormones & Exercise) Deficiency Effect Sex hormones stimulate ossifi- (cause growth of cation of disks; long bones; estrogen stop bone length stronger than androgen) Physical stress bone thins & weak- (stimulates bone width; ens; atrophy hypertrophy)

2 divisions of skeleton: Axial – skull, vertebrae, sternum, ribs (thorax), hyoid bone 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: Foramen Meatus Sinus

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)