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Are bones organs?
Yes, because they contain several different tissues.
What are some functions of bones?
- Support - holds everything up and gives body shape.
- Movement - connects bones to bones and muscles to bones, allowing the body to move around.
- Protection - skull bones protect brain, vertebrae protect spinal cord.
- Mineral storage - bones store minerals which are later released into the bloodstream.
- Blood cell formation - red bone marrow makes red blood cells.
- Energy storage - yellow bone marrow stores fat cells.
Bones that are longer than they are wide. Femur? Long bone. Metacarpals? Long bones.
Short bones are kind of cube shaped, they are not somehow longer in one dimmension. Carpal bones ( wrist bones ) are short bones. Knee cap is a short bone.
Sesamoids are bones that grow within a tendon, like the kneecap.
Bones that are flat. Sternum is flat, ribs are mostly flat, scapula and cranial bones are flat.
Bones that aren't one general shape. Like vertebrae - kind of a circle with a spike coming off of it, hip bones, too.
What is compact bone, spongy bone?
The smooth, hard, dense outer layer of bone, deep to this is the spongy bone which is full of holes.
The spongy bone would be filled with marrow in life which would produce RBCs.
What is epiphyses, diaphysis?
Epiphysis / epiphyses ( pl. ) are the ends of a long bone.
Diaphysis is the shaft of the long bone.
What is the epiphyseal line?
A line of what looks like dense bone between the epiphyses and diaphysis.
This is where the epiphyseal plate was during the period of growth of a human. Epiphyseal plate was a plate of cartilage between the epiphyses and diaphysis.
What is the nutrient artery, nutrient vein?
An artery and a vein that brings blood supply to the diaphysis of the bone. They enter the diaphysis of the bone through a hole called the nutrient foramen.
What are epiphyseal arteries, veins?
Arteries and veins that supply blood to the epiphyses of long bones.
What is the Medularry cavity?
A canal through the center of a long bone that has no bone tissue at all and is filled with yellow marrow.
What is periosteum?
A connective tissue that covers the entire outer surface of the bone except epiphyses and articular surfaces.
Perisosteum has two layers - the deep layer which lies against the bone tissue is the osteogenic layer. It has osteoblasts ( which build up bone ) and osteoclasts ( which break down bone ) within it.
Periosteum has a lot of blood vessels and nerves throughout it which supply it with blood.
Periosteum also provides points that tendons and ligaments can attach to. Sharpey's fibers are very dense here.
Sharpey's fibers are thick bundles of collagen that attach the periosteum to the bone matrix. They are also called perforating fibers.
What is endosteum.
Endosteum ( endo = inside ) is a thin connective tissue that lines the medullary cavity, deep to spongy bone and superficial to yellow marrow.
Endosteum is osteogenic, it has osteoblasts and osteoclasts which can reshape and reform bone.
What is diploe?
Diploe is what the spongy bone in flat bones is called.
What is an osteon?
On a cross-section of a long bone osteons look like concentric rings, like on a cross section of a tree. These rings run the length of the bone and are actually more like groups of concentric tubes.
Down through the osteon, collagen fibers and mineral crystals kind of wind their way around the lamellae. The collagen fibers will run in opposite directions on adjacent lamellae.
Each of the individual tubes is a lamela.
The central tube down the center of the osteon is the central canal.
What are lamellae?
Lamellae are the individual, concentric tubes that make up the osteon.
What is a central canal / Haversian canal?
It is the canal that runs down the center of an osteon through which runs a blood vessel.
What are perforating canals / Volkmann's canals?
Perforating canals are canals that run between central canals.
What are lacunae in compact bone?
They are small spaces that osteocytes inhabit.
What are canaliculae?
Narrow spaces extending from the lacunae that connect with other lacunae.
These finger-like spaces extending from lacuna to lacuna form a kind of network that moves nutrients through the bone.
What are interstitial lamellae?
Interstitial lamellae are the bits that fill in the spaces between the osteons. They are actually left over bits of old osteons that have been broken down during bone reformation.
If you set up a bunch of soda cans to represent osteons you will end up with empty spaces in between them. The interstitial ( in between ) lamellae are sort of like partial rings or partial tubes that fill in these spaces.
What are circumferential lamellae?
Lamellae that wrap around the external and internal surfaces of compact bone.
What are trebuclae?
Trebuclae are sort of the arches that make up spongy bone. They are made of layers of lamellae and osteocytes but are not large enough to have osteons.
What are hydroxyapitites?
Mineral salts that make up much of bone tissue, much of it is calcium phosphate.
What are osteoclasts?
Osteoclasts break down bone. They are very large, multinucleated cells that move along the periosteum and endosteum, secreting HCl to remove calcium and phosphate ions, breaking the bone down. Lysozomes are also released to remove the organic material.
What are osteoblasts?
Osteoblasts make bone. They lay down organic osteoid ( don't know exactly what osteoid is ) which is later calcified by calcium ions.
Basic bone formation process, 5 steps...
- 1. Mesenchymal cells differentiate to osteoblasts.
- 2. Osteoblasts secrete organc matrix ( GAGs, osteoid tissue, collagen fibers, glycoproteins...
- 3. Osteoblasts are surrounded by organic matrix.
- 4. Tissue fluids bring in inorganic matrix ( calcium salts, phosphates ) bone calcifies and hardens.
- 5. Osteoblast becomes osteocyte, retires to it's lacuna.
Intramembranous Bone Formation - membrane bone.
- 1. Mesenchymal cells become osteoblasts.
- 2. Osteoblasts become osteoid tissue.
- 3. Calcium salts are deposited in osteoid tissue, calcifying and hardening it.
- 4. Bone matrix with trapped osteocytes becomes plate of woven bone.
- 5. Osteoblasts lay down more bone around initial plate of woven bone.
Endochondral Bone Formation - cartilage replacement bone...
- 1. Hyaline cartilage cells hypertrophy and release chemicals.
- 2. Cartilage matrix calcifies and cartilage cells die.
- 3. Empty lacunae surrounded by calicified cartilage is left behind.
- 4. Blood vessels, osteoblasts, and bone marrow cells move into empty lacunae.
- 5. Osteoblasts start laying down new bone, replacing old, calcified cartilage.