Skeletal Anatomy

Components (Type of Connective Tissue)
1. Cells (osteocytes) located in lacunae
  1. Osteoblasts = build bone
  2. Osteocytes = mature bone cells
  3. Osteoclasts = breakdown bone
  4. “Blasts build, Clasts kill”
2. Intercellular substance
  1. Fibers → collagenous
  2. Matrix
    1. Organic matrix → Carbon-based
      1. Glycoproteins & Proteoglycans
    2. Inorganic matrix (hardness)
      1. Crystals attach to fibers
        
        Calcium phosphate
        
        Calcium hydroxide

Nursing Points

General

Structural Types of Bone
1. Type determined by lamellar organization
2. Trabecular (aka “Spongy”)
  1. Trabeculae → Lamellae in multiple linear layers with slight curvatures
  2. Spaces contain Red Bone Marrow
3. Compact Bone
  1. Lamellae in concentric circles
  2. Osteon or haversian system
    1. Basic unit of compact bone
Microscopic Structure of Compact Bone
1. Haversian Canal (center of Osteon)
  1. Contains blood vessels, lymph vessels, and nerves
2. Alternating layers of lamellae and lacunae with osteocytes
3. Canaliculi = cross-canals in lamellae
  1. 1st layer directly connect to Haversian Canal
  2. Interconnect lacunae
  3. Nutrients go from blood vessels to canaliculi to lacunae to osteocytes
  4. Wastes go the opposite direction
Functions of Bone
1. Site of attachment
  1. Ligaments
  2. Tendons
  3. Soft tissues other than skeletal muscle
2. Mechanical leverage system
  1. With skeletal muscle
3. Protection for organs in body cavities:
  1. Cranial
  2. Spinal
  3. Thoracic
  4. Pelvic
4. Calcium and phosphate reservoir
5. Hematopoiesis
  1. Creation of RBC’s, WBC’s, and platelets
  2. Red bone marrow

References
Betts, J.G., et al. (2017). Anatomy and physiology. Houston, TX: OpenStax, Rice University. Retrieved from https://openstax.org/details/books/anatomy-and-physiology?Book%20details

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Transcript

Okay guys in this lesson we’re going to talk about skeletal anatomy and the structure and function of basically how bones work.

So before we get started, the first thing that we need to know about are the different components of bone. You’re going to see this term throughout all of anatomy and physiology but the word is osteo, and it comes to the Greek osteon which means bone. Also, you have different types of bone cells, so you have osteoblasts, osteocytes, and osteoclasts.

Osteoblast are the bone cells that actually construct or build bones. Osteocytes are the actual bone cells, and osteoclasts are cell that break down cells. The easiest way to remember this or that “blasts build, clasts kill”

Now in the bone we have these things called matrices or the intercellular substances. Now these matrices are made up of different things. You have two different types of matrices, give an organic matrix and an inorganic matrix. The organic matrix is carbon-based and it contains glycoproteins and proteoglycans. There’s a lesson on all the different types of cellular components, so I encourage you to check those out. But with the inorganic matrix, this is the part of the intercellular substance that really makes the bones hard. You also have different types of salt crystals that create the hardness within the bone. These are really important for storing different types of minerals, in particular calcium phosphate and calcium hydroxide.

Let’s look at how the bones and all the cells within the bone work together.

There’s really two different types of bone. You have compact bone, and you have trabecular or spongy bone. The difference between the two is it compact bone is dense and spongy is actually porous. Compact bone is made up of all of these different types of units called osteons and they formed the really hard exterior part of the bone.

Trabecular or spongy bone, is porous, and it’s found near the joints and in long bone. The lamela are made in multiple layers. You’re going to see this term lamella, but what you need to know about lamella is its how different types of layers are arranged. But within spongy bone, they’re made linearly, and the spaces in between actually contain red bone marrow.

All right so let’s look at an osteon.

Osteons are cylinder like structures of the bone. If you look at them they are made up of the osteocytes, and they’re formed in these layers. These layers are called lacunae and what they are are concentric circles of osteocytes and they go in the circle. Inside the middle of each osteon is a canal and this is called a haversian canal, and it houses all the nerves and blood vessels. As each blood vessel goes up and down the haversian canal, the blood and all the nutrients need to go to the osteocytes, they also need to remove waste from the osteocytes. In the way they do this is through something called canaliculi. The canaliculi traverse across all of the blood vessels away from the Haversian Canal, and they provide all of the nutrients to the osteons and bring all the wastes away.

So you have the cylinders and they have all the osteocytes that make up the compact bone, so how do they actually make a long bone?. Well all of these osteons together are in bundles. So you how these concentric circles and then they’re put into cylinders, and then those cylinders are actually bundled all together. And as they build and build and build, they actually create this really strong network together, which creates bone. So now it’s look at the functions of bone.

This seems like a silly question, but what are the functions of the bone?

Well first of the site of attachment for ligaments and tendons, which help muscles and bones to attach to each other. Remember ligaments attach bone to bone, and tendons attach bone to muscle. There’s got to be a way for the ligaments, bones and muscles to all work together. And that’s one of the functions. Another thing that bone does is that it works with muscles to create a mechanical leverage system, which actually creates movement. It allows you to lift your arm and to take steps into bend over. All of these systems work together cohesively, and that’s what allows the body to utilize the bone.

Another thing that bones do are that they offer protection. The cranium protects the brain, the vertebrae protect the spinal cord, the thorax protects the heart and lungs, and in the pelvis protects some of the internal organs. Another thing that bones do is that there a reservoir for minerals, particularly calcium and phosphorus. Another important thing that bugs you are that they are responsible for hematopoiesis. And what hematopoiesis is, is it it’s the generation of different types of cells. In particular it’s the responsible for the creation of red blood cells, white blood cells, and platelets. The other thing that bones do are that they are the site of bone marrow where all this hemopoiesis occurs.

Okay so let’s recap.

Any timer talking about in anatomy and physiology we are looking at structure and function. In terms of structure, there are two different types of bone which are spongy and compact.

Compact bone is made of osteons, which of the cylinders of osteocytes and those things are bundled together and they reinforce the strength of the bone.

The haversian canal is really important because it houses the nerves in the blood vessels, and the canaliculi that reach out from that haversian canal into the osteocytes away from them to bring them nutrients and remove waste.

Spongy bone is the type of bone that is responsible for containing red bone marrow.

And finally lets up its function. The bone is responsible for movement, mineral Reservoir, and the creation of blood cells.

That’s it for a lesson on skeletal anatomy and the function of the bone. Make sure you check out all the resources attached to this lesson, now go out and be your best self today and as always. Happy nursing

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