The Skeletal System

Fun Facts• A giraffe has the same # of bones in the neck as

humans do• Bones are 14% of your body weight• Bone is 5x as strong as steel• Most women and girls have smaller and lighter

skeletons than men and boys• The female pelvis is wider than males• Male’s growth plates harden at 18-21 years of age• Female’s growth plates harden at 16-18 years of age

How many bones does an adult body have?

206How many bones are babies born with?

350

Largest bone?Femur: thigh bone

Shortest Bone?Stirrup: located in the ear

Functions of the Skeletal system

1. Support2. Protection3. Movement4. Mineral storage5. Hematopoiesis (blood cell formation)

What’s in a bone?

• Bones, Muscles, and Joints

Classification of BonesBones are identified by:

1. ShapeA. Long bonesB. Short bonesC. Flat bonesD. Irregular bones

2. Internal tissuesA. Compact B. Spongy

3. Bone markings

Spongy Bone

Compact Bone

Shape: Long Bones

• Are typically longer then they are wide

• As a rule they have a shaft with heads at both ends

• Mostly compact bone

• All of the limbs (femur, tibia, humerus), except the wrist and ankle bones.

Shape: Long Bones

Diaphysis (long part): – Covered by periosteum– Sharpey’s Fibers secure the

periosteum to the underlying bone

Epiphysis (ends): – Articulate with other bones– Covered by Articular cartilage

Metaphysis: – Location where diaphysis and

epiphysis meet

Shape: Flat Bones

• Are thin, flattened and usually curved

• Have two thin layers of compact bone sandwiching a layer of spongy bone between them

• Found in the skull, sternum, ribs, and scapula

Shape: Flat Bones

• The parietal bone of the skull Figure 6–2b

Shape: Irregular Bones • Have complex shapes • Examples: Vertebrae, Mandible, Sacrum,

Pelvis

Shape: Short Bones• Are small and thick• Cube-shaped and contain mostly spongy bone• Examples: Carpals, Tarsals,

Calcaneus

Shape: Sesamoid (ses’ah-moyd) Bones

Special type of short bone

- Form within tendons- Best known example is the patella- Develop inside tendons near joints of

knees, hands, and feet

Check Point1. Approximately how many bones are there in the human

body?

2. What is hematopoiesis?

3. What are the five functions of the bones?

4. What is the difference between compact bone and spongy bone?

5. Draw and diagram a long bone.