WORKSHEET 3: BONES INTRO!

List and describe some of the functions of bone connective tissue.

Describe the different types of cells found in bone CT

Osteocytes-

Osteoblasts-

Osteoprogenitor cells-

Osteoclasts-

Describe the composition of bone. What exactly is bone made up of?

**A Haversian system is the functional unit of compact bone tissue. It is also known as an osteon**

Draw a Haversian System and label the following parts: central canal(haversian canal), lacunae, canaliculi, concentric lamellae, osteocytes, circumferential lamellae, periosteum

What is the periosteum? What does it consist of?

How is the endosteum different from the periosteum?

Define the following terms and describe their importance: epiphysis, diaphysis, metaphysis

**The difference between ossification and calcification is that ossification refers to the process of replacing other tissues with bone, and calcification refers to the deposition of calcium salts within a tissue. ANY TISSUE CAN BE CALCIFIED BUT ONLY OSSIFICATION WILL RESULT IN THE FORMATION OF BONE**

What are the 2 major types of ossification and which bones do they involve?

What is an ossification center?

Describing intramembranous ossification (starts in utero)

Mesenchymal cells become vascularized mesenchymal cells differentiate into osteoblastsossification process beginsbone expands as a series of spicules that spread into surrounding tissue spicules become interconnect and trap blood vessels in boneover time bone turns into spongy boneareas of spongy bone may be removed (creating medullary cavities)through remodeling, spongy bone formed in this way can be converted into compact bone by deposition of osteoblasts and remodeling of osteoclastsmature bone is completed

Endochondral Ossification (begins with formation of hyaline cartilage model, starts in utero)

Chondrocytes near center of shaft enlargematrix reduced to small strutsenlarged chondrocytes die and disintegratecavities are formed within the cartilage blood vessels grow around edges of cartilagecells of perichondrium (what will be periosteum) become osteoblastsshaft of cartilage grows a superficial layer of boneblood vessels then penetrate bonefibroblasts in blood vessels become osteoblastsosteoblasts begin producing spongy bone @ primary ossification site bone formation spreads toward endsmedullary cavity is createdbone at shaft becomes thickercartilage near epiphyses is replaced by shaft of bonegrowth in length and diameter occurscapillaries and osteoblasts migrate into epiphysessecondary ossification centers are createdepiphyses are filled with spongy boneepiphyseal cartilage separates epiphyses from diaphysis at metaphysis

Appositional growth: growth in diameter

Ridges parallel to a blood vessel are formeda deep pocket is created around blood vesselridges meet and fuseblood vessel is trappedbone deposition creates an the beginning of osteoncircumferential lamellae are deposited as bone increases in diameterfull osteon complete

**As bone grows in diameter by adding new bone to the outer surface, osteoclasts resorb bone on the inside thus enlarging medullary cavity**

**Normal bone growth cannot occur without a constant dietary source of CALCIUM, PHOSPHATE SALTS, MAGNESIUM, CITRATE, CARBONATE, and SODIUM**

**Calcium and phosphorus can be taken away from the bone surface by osteoclasts in order to be supplied to the blood for other processes** (remember, bone is a storage for minerals)

** Length of a developing bone increases at the epiphyseal cartilage, which separates the epiphyses from the diaphysis. Here new cartilage is added at the epiphyseal side, while osseous tissue replaces older cartilage at the diaphyseal side** Growth plates<