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 Skeleton1. Axial skeleton (body’s central frame)2. Appendicular skeleton (body’s lateral frame)

Axial (forms the midline of the body)Includes the following partscranium, 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 organsa) Skull protectsprotects brain.b) Rib cage protects heart and lungsc) Pelvis protects reproductive organs.

2. [Support] provides framework for tissues to hang on.

3. [Movement] muscles attached via tendons.4. [Storage] of minerals like calcium (Ca) and

phosphorous (P)5. [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. Epiphysis = ends of bone (covered in hyaline cart) Epiphyses form RBC’s

2. Diaphysis = narrow shaft of bone3. Periosteum = layer of connective tissue

outside of bone. Contains blood vessels and nerves.

4. Medullary Cavity = Hollow center of the bone. Contains major blood vessels and marrow.

ANATOMY OF BONE

COMPACT BONE

1. Calcified matrix ( Canaliculi ) contain lacunae which hold osteocytes.

2. Osteocytes are connected to each other by canaliculi.

Receive nutrients Get rid of wastes

3. 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) Joints bear greater amounts of stress from many directions.

b) 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. Enlarged pelvic outlet / inlet2. Less curvature of the sacrum and coccyx.3. Broader = Iliac bones stick out more laterally but

not as high as in males.

MALE VSFEMALE