In this video we discuss the structure of bone tissue and the components of bones. We also discuss what are osteons, what are canaliculi, what are trabeculae, and the components of bone matrix.


Transcript/notes

Structure of bone tissue
The bones in your body are made up of an extraordinarily complex connective tissue that’s structure matches its function. It is comprised of cells, fibers and extracellular material or matrix.
The bones in your body have 3 major types of bone cells.

Let’s start by looking at a diagram of bone tissue. There are 2 main types of bone tissue, compact bone and cancellous bone or spongy bone. Compact bone surrounds the spongy bone tissue and it has a unique appearance. These cylinder shaped structures are called osteons or Haversian systems. In the middle of these osteons is a central Haversian canal that runs lengthwise through the bone and it houses nerves and blood vessels that supply the bone.

The cylinder shaped layers of the osteons are called concentric lamellae. The lamellae are composed of calcified matrix. The matrix of the bones in your body is composed of inorganic salts and organic material. The inorganic matrix is made up of rocklike crystals of calcium and phosphate called hydroxyapatite crystals, calcium carbonate and magnesium, sodium, sulfate and fluoride are also found in bone material.

The organic material is comprised of collagenous fibers and a gel like ground substance containing protein and polysaccharides. The ground substance is important in providing support and adhesion between cellular and fibrous elements.

There is also circumferential lamellae that runs along the periosteum, which covers the outside of bones, and along the endosteum which lines the inner spongy bone tissue. Interstitial lamellae are located between osteons.

Lacunae are the small spaces in bone tissue where mature bone cells called osteocytes are imprisoned. These cells are responsible for maintaining the bone matrix.

Canaliculi are small canals that extend in many directions from the lacunae connecting to other lacunae and the central canal. They provide for intercellular communication and passageway for the delivery of nutrients to the osteocyte cells.
There are also transverse canals which connect central canals to one another and these canals also house nerves and blood vessels.

Now for spongy bone tissue. Spongy bone has no osteons as it has a lattice like appearance of crisscrossing branches called trabeculae. The trabeculae are comprised of endosteum surrounding parallel lamellae composed of bone matrix, and osteocytes in lacunae with canaliculi extending out from the lacunae.
Some of the canaliculi open onto the surface of the trabeculae. Like in compact bone tissue, the canaliculi provide a passageway for nutrients to reach the osteocyte cells.

The formation or lattice like look of spongy bone allows it to distribute any stress or pressure applied to it throughout the entire framework.

Timestamps
0:00 Overview of the structure of bones
0:11 Structure of compact bone tissue
0:25 Osteons
1:22 Circumferential lamellae
2:10 Spongy bone tissue

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