Bone Lecture Videos Flashcards
Structure of Bones
Two different parts
Outer layer of bone
-Compact (Cortical) Bone:Outer layer of bone
-Spongy (Cancellous/Trabecular) (interior)
Bone: Inner layer of bone (bone marrow resides) 80% of surface area is spongy bone
Functions of Skeleton
What are the five main roles of the skeleton in the body
- Protection vital organs
- Structure
- Movement
- Hematopoiesis (formation of new blood cells both red/white)
- Storage (middle of our long bones - store fat within there), calcium salts really important throughout our body. Starting alot of cell processes
- really important our level calcium regulated and if it’s low we’ll pull calcium out of our bones
What gives bones its properties?
- Hardness = due to calcium phosphate salts
- Flexibility and tensiles strength = due to collagen
- Less water content than other tissues
Structure of Bones
Diaphysis = shaft (long part of the bone) -Epiphysis = end of bones (2)
Articular cartilage = covers epiphyses
What’s kind of cartilage is articular cartilage?
-Hyaline cartilage
Within the epiphysis infants, the entire length of bone is filled with spongey bone and as we age the shaft of the bone will lose that sponginess and end up with this medullary cavity which gets filled with Yellow bone marrow = fat.
Growth plates found on either ends
Photo of Structure of Bone
Periosteum - surrounds outside the bones and heavily innervated and activity the pain sensing nerves.
Fibrous layer - superficial (dense irregular connective tissue
cellular layer - deeper - contain all cells that contribute to the growth of bones osteoblast if we want to increase thickness of bone
Endosteum - interface betwn the cortical bone and spongey bone.
Blood vessels that need to supply our blood and we’re making new cells in the bone morrow
2 main sources. of blood to our bone
-outer third are via these blood vessels within the periosteum
-inner 2/3 supplied by nutrient arteries each bone typically has two or three nutrient arteries that run through the periosteum and enter the bone through something known as the nutrients foramen. Head in to the spongey bone and radiate outwards and supply the inner two-thirds of the cortical bone and the rest of the bone
Collagen that come from the fibrous layer of the periosteum called Sharpey fibers
Microscopic Bone Structure
Types of Bone Cells
Located in the cellular layer of the periosteum, Osteogenic Cell - Stem cells when they divide they will make Osteoblast are cells that build up bone (make it bigger and stronger) they pump collagen into the extracellular matrix and fill it with calcium. They pump out so much extracellular matrix and surround themselves then they’re called Osteocytes (found throughout the corticle bone)
Osteoclast - crushed these cells break down bone causes release of calicum in the blood supply (phagocytosis secreting hydrocholic acids in the bone)
Microscopic Structure of Cortical Bone
Osteocytes sit in cavities called: Lacunae (lakes the osteocytes sit in)
Concentric (circle within a circle)
Lamellae - (ring of ostercytes + the extra cellcular matrix they’ve made)
Arteries, veins and nerves run through the central canal
Osteocytes are arranged in concentric circles around a central canal called:
As osteon consists of: central canal surrounded by multiple lamellae
Won’t find osteon in the spongibone
Microscopic Structure of Cortical Bone Fig 5.4
The blood vessels withing the central canal with link up to the spongy bone at some point through these perforating canals, sometimes called Volkman’s canals and how blood cells are able to get from here, the spongy bone, out into other areas to make sure that everything is supplied within the Osteon
Picture of Lamella Fig 6.8
One lamella all the collagen will be oriented within the same directions this helps increases the strength of bone and prevent it from getting damaged due to external forces.
Another piece
Canaliculi - little canals that are connected the osterocytes sitting in separate lamellae
Within the osteocyte - projections like dendrites and extending through the canaliculi.
How do nutrients get to Osteocytes in the outermost lamellae?
- Osteocytes will send it dendrites and send another osteocyte dendrite pass nutrients between them
- Gap junctions (channels to quickly pass nutrients)
Spongey Bone
Trabeulae- organized based on stress lines to transfer force throughout the wider structure of the bone and add more stability.
Besides serving as a site for hematopoiesis, what other functions does spongy bone serve?
-Weight, lightens the bones
Picture
We start as Cartilage and made up as hyaline cartilage
In the skull between our different bones we have Fonatanelles which connects the bone but the bones are not fused (soft spots in babies)
Why are fontanels beneficial in infants?
Birthing process some flexibility within the skull during birth
Growth Plates Epiphyseal Plates
On the edge of the epiphyseal plate and the articular cartilade that faces the ephysis faces the end of the bones, shown here with the black arrows, we’re going to be laying down new cartilage. Chondroblast, which make are a type of cell that makes new cartilage. They’ll lay down new cartilage at this edge of the epiphyseal plate and this edge of the articular cartilage.
At the same time, at the part of the epiphyseal plate and the articular cartilage that paces the diaphysis (red arrows) that’s where the cartilage will be converted to bone. (cartilage will be broken down and osteoblast will create new bones)
-bone and cartilage are being layed down at the same rate
When we stop growing we stop laying down new cartilage but continue to convert the cartilage to bone until it catches up then the growth plates are closed.
Epiphyseal Plates cause lengthwise growth of bone
During childhood, new cartilage is constantly formed
Old cartilage is broken down and replaced by bone
Appositional Bone Growth
When we are increasing the diameter of bones
Endosteal portion where we have the junction of the spongeybone and corticle bone we’re breaking down the corticle bone and being resorbed
Cortical bone and the cellular layer of the periosteum, we’re gonna be laying down new bone.
It’s important that we’re breaking down bone and adding bone in order to grow by diameter
What type of cells will be active at the black arrow?
-osteroclayst
What ype of cells will be active at the red arrow?
-osterblast at the exterior
Bone Remodeling
- Bone is responsive to the stresses put on it
- Bone is responsive to calcium needs within the body
- Osteoclasts and osteoblast are active throughout life
- lay down more cortical bone to make it stronger
- your bone can thin if you’re not putting stresses on it
- Bones responsive to chemical stresses in our bodies if we don’t have enough calcium in our body and removing the calcium from our bones.
