SKELETAL UNIT
BONE INTRODUCTION NOTES
MMHS Anatomy and Physiology
SKELETON DESIGN
Human Skeleton has 206 Bones.
 Humans have endoskeletons (=internal)
 Arthropods have exoskeletons (=external)

Humans must rely on nervous system and
sensory organs for protection

*oncoming car

*hot stove

SKELETAL DIVISIONS
2 Main Divisions of the Skeleton
1.
2.

Axial skeleton (body’s central frame)
Appendicular skeleton (body’s lateral frame)
Axial (forms the midline of the body)
Includes the following parts
cranium, rib cage, vertebral column,
sacrum, coccyx

Appendicular (think “appendages”)
Includes the following parts
 pectoral girdle (shoulder), pelvic girdle
(hips), arms to hands, legs to feet.
AXIAL VS APPENDICULAR SKELETON
FUNCTION OF SKELETON
1.
[Protection] of vital internal organs
a)
b)
c)
2.
3.
4.
5.
Skull
Rib cage
Pelvis
protects
protects
protects
brain.
heart and lungs
reproductive organs.
[Support] provides framework for tissues to
hang on.
[Movement] muscles attached via tendons.
[Storage] of minerals like calcium (Ca) and
phosphorous (P)
[Production] of Erythrocytes (RBC’s) from red
marrow.
BONE CLASSIFICATION BY SHAPE
Bone Shape
Location in Body
1. Long Bones
Femur, humerus, tibia, fibula
2. Short Bones
Carpals and tarsal
3. Flat Bones
Clavicle, ribs, cranial plates, scapula
4. Irregular Bones
Vertebrae
BONE CLASSIFICATION
a. long
b. irregular
c. flat
d. irregular
e. short
BONE ANATOMY
1.
2.
3.
4.
Epiphysis = ends of bone (covered in hyaline cart)

Epiphyses form RBC’s
Diaphysis = narrow shaft of bone
Periosteum = layer of connective tissue outside of
bone.

Contains blood vessels and nerves.
Medullary Cavity = Hollow center of the bone.

Contains major blood vessels and marrow.
ANATOMY OF BONE
COMPACT BONE
1.
Calcified matrix ( Canaliculi
lacunae which hold osteocytes.
2.
Osteocytes are connected to each other by
canaliculi.


3.
) contain
Receive nutrients
Get rid of wastes
Blood vessels and nerves that travel the length
of the bone do so through Haversian Canals.
CANCELLOUS “SPONGY” BONE
1.
Trabeculae (interconnecting rods of bone) create
the “spongy” appearance.
2.
Located in epiphyses of bones (close to joints)
a)
b)
Joints bear greater amounts of stress from many
directions.
Cancellous bone channels stress into direction of
compact bone (= more strength)
CANCELLOUS BONE
GENDER DIFFERENCES IN SKELETONS
Male skeletons tend to be heavier to bear greater
muscle attachment.
 Coxa bones (hips) are narrower and more upright

Female skeletons have fewer markings on the
skeleton
 Female skeletons are better designed for
childbirth.

1.
2.
3.
Enlarged pelvic outlet / inlet
Less curvature of the sacrum and coccyx.
Broader = Iliac bones stick out more laterally but
not as high as in males.
MALE
VS
FEMALE