The Appendicular skeleton is comprised of long bones (humerus, radius, ulna, etc) which undergo endochondrial ossification (ossification from a cartilage model). It makes up the appendages (arms and legs)
The Axial skeleton is comprised of flat bones (ribs, vertebra, pelvis) which undergo intramembranous ossification.
Mature long bones are divided into specific anatomic regions:
Diaphysis
: the shaft of the bone
Metaphysis
: the flare of the shaft of the bone as it approaches the growth plate
Physis
: the growth plate, closes when the skeleton is mature, still evident on x-ray as a radiolucent area between the metaphysis and the epiphysis.
Epiphysis
: the end of the bone, on the other side of the physis from the metaphysis.
Apophysis
the site where major tendons attach. (pulling at this site leads to bone growth, has its own physis)
when theres a bump on a bone it is usually the result of something pulling there
Articular cartilage
(a.k.a. hyaline cartilage) covers the ends of long bones at their articular surfaces (joint surfaces)
Synovial lining
lines the inside of the joint capsule and produces synovial fluid which bathes the joint itself.
Periosteum
the layer over bone that contains bone progenitor cells but is not mineralized.
Endosteum
the lining of the inside of spongy bone that also contains bone progenitor cells.
Cortical bone
the outer shell of long bones appears solid except for microscopic spaces. Its crystalline structure gives it hardness and rigidity. Opaque to x-rays.
Cancellous bone
(spongy bone) are less dense and fill the inner portion of long bones. The trabeculae of spongy bone are oriented in response to the stress put on the bone.
Coronal plane (frontal)
a section cutting from right to left across the body, dividing the person into front and back halves.
Sagittal plane
a section that cuts front to back, dividing the person into right and left halves.
Transverse plane
(horizontal) a section cut parallel to the floor, dividing the person into a top and bottom
Proximal
closer to the body (trunk) Distal further out from the body. (e.g. the hand is distal to the shoulder)
Cephalic
closer to the head Caudal nearer to the feet.
Anterior is preferred over Ventral, Posterior is preferred over Dorsal
Adduction
motion toward the body in the sagittal plane
Abduction
motion away from the body in the sagittal plane
Raising your arm out to your side is abduction, bringing your arm back is adduction (adding it to the body). Jumping jacks
Internal rotation
- moving the distal end of the appendage towards the body in the transverse plane. (pointing your toes together while standing flat on the floor).
External rotation
moving the distal end of the appendage away from the body in the transverse plane. (weight lifters doing dumbell flys, or turning your feet o your toes point out laterally)
Flexion
decreasing the angle of a joint in the sagittal plane. (bringing your foot towards your buttock is flexion of the knee, or bending the elbow in a bicep curl is flexion of the arm)
Extension
increasing the angle of a joint in the sagittal plane. (extending the knee joint straightening the leg, or doing a tricep pulldown)
Varus
when the apex of the angle points away from the midline (e.g. bow-legged)
Valgus
when the apex of the angle points towards the midline (e.g. knock knee-ed)