BackTwo major regions of the skeleton:
The AXIAL skeleton is organized along the upright central axis (the head spine and thorax)
The APPENDICULAR skeleton, the paired long bones of the skeleton, capable of great freedom of movement
NOTE: the hipbone (Os coxae) is assigned to the appendicular skeleton by anatomists; for artists it is more useful to think of the complete pelvis as a fixed unit with the spine and thorax.
THE SPINAL COLUMN
There are 34 vertebrae in the spinal column -- 24 true vertebrae; 10 false vertebrae of the coccyx (5) and sacrum (5) which are immovable and part of the pelvic structure.
The true vertebrae are divided into 3 groups:
7 cervical - neck region
12 dorsal - region from which the ribs spring
5 lumbar - lower back
Each vertebra has three spinous processes which spring from the neural foramen (a ring of bone); the vertebrae are stacked vertically separated by pads of fibrous, elastic material (spinal discs).
The CERVICAL VERTEBRAE are relatively light and are the most flexible of all the vertebrae: can move backward, foreword and bend laterally; also some rotation.
The top vertebra, the ATLAS enables the head to rock back and forth as well as laterally. The second vertebra, the AXIS provides rotary articulation with the atlas thus allowing a swiveling movement of the head.
The first six vertebrae are buried deep beneath the surface, under the NUCHAL LIGAMENT which connects the occipital crest of the skull to the 7th cervical. The 7th cervical is an important construction point.
The THORACIC VERTEBRAE (12) give rise to the ribs. This is the least flexible region of the spine due to restraint imposed by the rib cage but is capable of all movements to some degree.
The LUMBAR VERTEBRAE are the largest; they are especially capable of forward bending (flexion); extension is limited. No rotation is possible and other movements are limited.
HUMAN ANATOMY FOR THE ARTIST: Introduction to the Skeletal System
In dealing with the human body the whole is greater than the sum of the parts. The human skeleton combines 2 opposites: STABILITY - from the front the skeleton is balanced bisymmetrically; ACTION - from the side balance is achieved by movement around a center of gravity.
The skeleton is the ARCHITECTURAL aspect of the body, the mechanical design. The individual parts can be separated from the rest without destroying the whole. The divisions between the parts are clearly defined. The proportions and actions of the figure are determined by the skeleton.
The muscles are-the ORGANIC aspect of the body. They imbricate or lace together the bony structure. Nothing can be removed from the muscular system without serious damage to adjacent parts.
The skeleton can be clearly seen in the living figure. Where bone is near the surface it is said to be SUBCUTANEOUS.
The single most important influence on the skeleton is the backbone. While the backbone is never seen in its entirety in the living body its influence is always felt.
Skeletal divisions of the trunk: the thorax (ribcage) the lumbar region (section between ribcage and pelvis) the pelvis.
GENERAL TERMS OF DESCRIPTION:
Pertaining to position:
anterior............................front
posterior......................... back
superior upper................ towards top
inferior lower.................. towards bottom
internal ............................inside
external ..........................outside
medial............................. nearer midline
lateral............................. further from midline
supine ............................forearm and hand turned palm-side upward
prone............................. forearm and hand turned palm-side downward
dorsal............................. refers to back; also back of hand, top of foot
Pertaining to bone:
cartilage ........................ substance from which bone ossifies; gristle
joint, articulation............. connection between bones
suture............................. interlocking teeth-like edges
head............................... enlarged round end of a long bone; knob
shaft............................... body of a long bone
symphysis...................... union of right and left sides in midline
eminence........................ low convexity (just perceptible)
protuberance, tubercle... bump (can be felt under finger)
tuberosity........................ large and conspicuous bump
process........................... projection (can be grasped with fingers)
spine................................ pointed projection or sharp ridge
crest................................ ridge or border
condyle........................... polished articular surface (usually a knob)
epicondyle....................... elevation near a condyle
trochlea........................... spool-shaped articular surface
ramus.............................. plate-like branch of a bone
fossa............................... shallow depression
foramen........................... hole; perforation
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