Skeletal Tissue (Microscopic Anatomy)

Name the Main Types of Bone Cells

Osteogenic cells

Osteoblasts

Osteocytes

Osteoclasts

Describe Osteogenic Cells

Stem cells found in the periosteum and endosteum.

Give rise to osteoblasts

Describe Osteoblasts

Secretes osteoid (organic bone matrix), which later hardens

What is Osteocalcin

It is a secretion produced by osteoblasts that helps regulate insulin

Describe Osteocytes

Former osteoblasts live inside lacunae (matrix they produced). Reabsorb/deposit bone matrix.

What Connects Lacunae

Canaliculi

Describe Osteoclasts

Formed from stem cells, breakdown bone

Why do Osteoclasts Have a Ruffled Border

To increase the surface area for the secretion of enzymes that break down bone

Where do Osteoclasts Breakdown Bone

Resorption bay

What are the Inorganic/Organic Components of Bone Matrix

Inorganic: Hydroxyapatites (calcium phosphates)- give bone exceptional hardness

Organic: Osteoid (collagen fibers and ground substance)

Approximately how Much of the Matrix does Each Component Take up

Osteiod: 1/3

Hydroxyapatites: 2/3

What is Found in Compact Bone

Osteon

Central canal

Perforating canals

Lamellae

Osteocytes (occupy lacunae at junctions of the lamellae)

Canaliculi (connect osteocytes to each other and to central canals)

Describe an Osteon

An elongated cylinder that runs parallel to the long axis of the bone. (weight bearing pillars)

What are Lamella

provide structural strength to bones (growth rings)

Describe the Central Canal

Runs through the osteon and contains small blood vessels

Describe Perforating Canals

Run perpendicular to and interconnect the central canal

Name 3 Types of Lamellae and Residing Locations

Concentric: layers of matrix around the central canal

Interstitial: incomplete lamellae lying between osteons

Circumferential: surrounds the entire bone shaft just deep to the periosteum

Describe Trabeculae

Found only in spongy bone, contains irregularly arranged lamellae and osteocytes interconnected by canaliculi

Where do Trabeculae Align

They align along stress lines

What are Spicules

Needle-like pieces of bone found in spongy bone. (rods or spines)