skeletal

   In embryos, the skeleton is primarily made of (hyaline cartilage).

2.        Most bones develop using (hyaline cartilage) structures as their “models”.  This process of bone formation is called          (Ossification).

3.       First , the hyaline cartilage model is completely covered with (Bone matrix) by bone building cells called (Osteoblasts).

4.       Then, the enclosed hyaline cartilage model is replaced by (bone), and the center is (digested away), opening up a         (medullary cavity) within the newly formed bone.

5.       Bones grow in length at the (Epiphysial plate).

6.       How do bones widen?  (2 pts)

Osteoblasts in the periosteum add bone matrix to the outside of the diaphysis as cells called osteoclasts in the endosteum remove bone from the inner face of the diaphysis wall, enlarging the medullary cavity

Bones are remodeled continually in response to changes in two factors:

1.        The calcium level in the blood

2.         The pull of the gravity and muscles on the skeleton

14. Giant bone-destroying cells in bones; they function to break down bone matrix and release calcium ions into the blood.  They are called (Osteoclasts).

15.  These cells lay down new matrix and become trapped within it to build new bone (Osteoblasts).

The repair of bone fractures involves four major events.  List them below:

1.        Hematoma (blood-filling, swelling, or bruise) is formed

2.         Fibrocartilage callous forms (Cartilage matrix, bony matrix, collagen fibers)

3.         Bony callus replaces the fibrocartilage callus (osteoblasts and osteoclasts migrate in)

4.         Bone remodeling occurs in response to mechanical stress

List three types of factures below and describe them:  (6 pts)

1.        Depressed, bone is pressed inward

2.         Spiral, break occurs when twisting forces are applied

3.         Communicated, bone breaks into three or more fragments

Structure of Bone

1.       Bone is relatively lightweight and resists tension and other forces

2.       Organic parts (collagen fibers) of the bone make bone flexible and have great tensile strength

a.        Tensile strength – the maximum stress that a material can bear before breaking when it is allowed to be stretched or pulled.

b.      Are your bones as strong as steel? Yes

3.      Calcium salts deposited in the bone make it hard to resist compression

B.      Bone Formation and Growth

1.       Ossification is the process of bone formation

2.      Occurs on hyaline cartilage models or fibrous membranes

3.      Long bone growth involves two major phases

a.        Osteoblasts (bone-forming cells) cover hyaline cartilage with bone matrix, long bones

b.      In a fetus, the enclosed cartilage is replaced by bone and the center is digested away, opening up a medullary cavity

4.       By birth, most cartilage is converted to bone except two regions in a long bone (articular cartilage and epiphyseal plates)

5.      New cartilage is formed continuously on the external face of these two cartilages

6.      Old cartilage is broken down and replaced by a bony matrix

7.      Appositional Growth

a.        Bones grows in width

b.      Osteoblasts in the periosteum addbone matrix to the outside of the diaphysis

c.       Osteoclasts in the endosteum removebone from the inner surface of the diaphysis

8.       Bone growth is controlled by hormones, such as growth hormones and sex hormones.

C.      Bone Remodeling

1.       Bones are remodeled throughout life in response to two factors:

a.        Calcium ion level in the blood determines when bone matrix is broken down or formed

b.      Pull of gravity and muscles on the skeleton determines where bone matrix is to be broken down or formed

D.     Calcium ion Regulation

1.       PTH (parathyroid hormone)

a.        Released when calcium ion levels in blood are low

b.      Activates osteoclasts (bone-destroying cells)

c.       Osteoclasts break down bones and release calcium ions into the blood

2.       Hypercalcemia (high blood calcium levels) prompts calcium storage to bones by osteoblasts

Intramembranous Ossification/Bones

1.       Flat bones of the skill, clavicles, sternum, and some facial bones.

2.      Refers to the formation of bone directly on or withing the fibrous connective tissue membranes

3.      No cartilage is present

4.      First bone to start, one of the last to finish

B.      Endochondral Ossification/Bones

1.       Most of the bones of the skeleton are endochondral bones

2.      Develop from masses of hyaline cartilage shaped like future bony structures

3.      Stages 1-3 during fetal week 9 through 9th month

Compact bone is also called  - Cortical Bone

2.  Perpendicular to the Haversian canals are (Volkmann’s canal).

3.  Between the lamellae are small spaces known as (Lacunae).

4.  These are layers of bony matrix that encircle the entire outer and inner surfaces of the bone – Circumferential Lamellae

5.  The fundamental functional unit of compact bone is the (Osteon).

6.  The center of each osteon is the (Haversian Canal).

7.  The (Canaliculi) are microscopic canals that connect the lacunae to each other and to the (Haversian Canal).

8.  These concentric rings of calcified matrix surround the Haversian canal -Lamellae

9.  Lacunae house (Osteocytes), which are mature bone cells that maintain the (Bone Matrix).

10.  Lamellae are composed of (Collagen fibers) and (Mineral Salts) primarily (Calcium Phosphate) which provide the bone with (Tensile Strength) and resistance to (Bending).