Skeletal System

Appositional Growth

Cartilage-forming cells in perichondrium secrete new matrix against external face of existing tissue

Interstitial Growth

Lacunae-bound chondrocytes divide and secret new matrix, expanding cartilage from within. Typically ends during adolescence, when skeleton stops growing.

Hyaline Cartilage

Most abdundant, support, flexibility, and resilience. Fine collagen fibers.

Elastic Cartilages

Only found in two locations (external ear, epiglottis). Stretchy, withstand repeated bending.

Fibrocartilage

Parallel rows of chondrocytes alternative with thick collagen fibers. Occur in areas subject to both pressure and stretch (menisci of knee, discs between vertebrae).

Function of Skeleton

Support, framework, protection, mineral storage, blood formation.A

Axial Skeleton

Skull, vertebral column, rib cage. Support and protect.

Appendicualr Skeleton

Upper, lower limbs, and girdles. Allow for movement and manipulation of environment.

Long bone

Most limb bones, longer than they are wide. Humerus, Tibia, Fibula, Femur, etc.

Short bone

Roughly cube shaped, wrist and ankle.

Flat bone

Thin, flattened, a bit curved. Sternum, scapulae, ribs, cranial bones.

Irregular bone

Doesn’t fit any previous category. Vertebrae, hip bones.

Endochondral Ossification Steps

All bones below base of skull form by endochondral ossification (besides clavicles).

1. Bone collar forms around disphysis of hyaline cartliage model. Consists of bone collar, primary ossification center.

2. Cartilage calcifies in center of diaphysis and developes cavities. Consists of deteriorating cartilage matrix.

3. Periosteal bud invades internal cavities, spongy bone forms. Blood vessel and spongy bone formation. Osteoprogenitor cells become osteoblasts, secrete osteoid around remaining calcified fragments of hyaline cartilage.

4. Diaphysis elongates, medullary cavity forms. Secondary ossification centers form in epiphyses.'

   1. Epiphyses ossifies. Once ossification is complete, hyaline cartilage only remains in epiphyseal plates and articular cartilages.

Intramembranous Ossification

Forms cranial bones and clavicles. Most bones are flat bones.

1. Ossification centers develop in fibrous connective tissue membrane. Mesenchymal cells.

2. Osteoid is secreted and calcifies, trapped osteoblasts becomes osteocytes.

3. Immature spongy bone and periosteum form.

   1. Compact bone replaces immature spongy bone, deep to periosteum. Red marrow developes.

Fracture repair

1. Hematoma forms. Blood vessels in bone and periosteum are torn, causing hemorrhaged blood clots and forms a hematoma.

2. Fibrocartilaginous callus forms

3. Bony callus forms (spongy bone, trabeculae)

4. Bone remodeling occurs (compact bone)

Comminuted Fracture

Three or more pieces

Spiral Fracture

Twisting forces applied to a bone, fractures.

Depressed Fracture

Broken bone portion pressed inward

Compression

Bone is crushed

Epiphyseal

Seperates from diaphysis along epiphyseal plate

Greenstick

Bone breaks incompletely, only one side of shaft breaks while other side bends.

Fibrous joints

Suture - Held together with short interconnecting fibers, only found in skull. No movement.

Syndesmosis - Joint held together by ligament. Little to no movement, can be found in distal ends of tibia and fibula.

Gomphoses - Peg-in-socket, tooth.S

Synovial Joint

Bones seperated by fluid-containing joint cavity, most joints of the body. Has articular cartilage, joint cavity, articular capsule, synovial fluid, reinforcing ligaments, and nerves and blood vessels. Plane, hinge, pivot, condylar, saddle, ball-and-socket.

study

Flexion/Extension

decreasing/increasing angle between two bones in sagittal plane

Abduction/Adduction

Moving a limb away/towards body midline in frontal plane

Circumduction

Cone movement

Medial/lateral rotation

rotating toward/away from median plane (like twisting your leg from the hip inward or outward)

Inversion/eversion

Sole of foot twisting towards/away from medial

Elevation/depression

Up and down (movement of mandible elevation and depression, like chewing).

Opposite/reposition

Doing the “ok” symbol with your thumb and index finger, pinching them together is opposition.