Exam1Lec7Bone Flashcards
What type of cartilage is needed in order to form bone?
Hyanline cartilage
forms the precursoe skeleton for the formation of bone, endochondral bone formation
As the bone grows, the chondrocytes undergo ____ and then die.
Hypertrophy.
How are long bone and flat bones formed?
said we wont be tested on, but still talked aboujt it
Long bone formed via endochonral bone formation
Flat bone formed via intramembranous bone formation
What is the diaphysis of bone?
Compact bone
Bone is a ____ tissue with a ____ matrix, made up of calcium phosphate in the form of hydroxyapatite crystals.
connective, minerlized (calcified)
calcium phosphate gives strength/hardness to bone
4 fxns of bone
- Structural support
- Anchoring muscle for movement
- Protection of underlying organs
- Storage site for calcium
bone has 99% of calcium
What is contained in the bone matrix?
- Calcium phosphate
- Type 1 coll
- GAGs
- Glycoproteins
fibrocart also have type 1 coll
The matrix spaces of the bone have lacunae similar to cartilage. What does the lacunae house?
Osteocytes
What is the epiphyseal plate?
This the the growth plate: a plate of compact bone that formed by replacing the final hyaline cartilage during growth.
when growing, it is made of hyaline cartilage
What is the epiphyses?:
The end of long bones. It contains red marrow , this is the production site for red and white blood cells
spongy bone
What is the diaphysis?
Shaft of the long bone and containds the meduallry cavity
compact bone
What is the medullary cavity?
Site of bone marrow
contains red marrow when young
What is the periosteum?
Double layer of DENSE IRREG CT covering the entire bone except for joints
like periochondrium of cartilage
also has osteoprogenitor cells
tendons attach here
For the diaphysis, ____bone surrounds it and we see ____ bone in the interior/
compact, spongy
Is bone vascularized?
Yes, highly vascularized. Bone is able to repair due to blood supply
When cartilage (vascular) becomes vascularized it begins to calcify (cartilage dies & bone replaces it)
The layers of the diaphysis of compact bone from outside to inside
finish this fc, confused slode 30 and 31
- Periosteum
- Outer circumferential lamellae
- Haversian (central) canals
- Inner circumferential lamellae
- Endosteum (lines bone marrow cavity)
- Bone marrow with either red or yellow
mesenchyme> osteoprog>osteoblasts>osteocytes
What is contained within periosteum?
Outer: dense irreg CT
Inner: periosteal osteoprogenitor cells that can develop into osteoblasts
What is the Haversian (osteon) system?
The basic unit of compact bone, has cyclinder running parallel to the long axis of the bone.
Lamella, Haversion (central) canal, and Volkmann’s (perforating) canals
What is lamella?
Concentric rings of the bony matrix forming the tubes.
What is the Haversian (central) canal?
Canal running through the middle of the Haversian system. Containing blood vessels and nerve fibers
What is the volkmanns’ (perforating) canals?
Run perpendicular to the long axis and provide channels for blood vessels and nerve fibers to connect adjacent Haversian systems.
bone maturation
As bone remodels what happens?
Haversian system may be reabsorbed and replaced by new system resulting in areas of partial lamellae ( not a full osteon, so looks like a 1/2 circle)
bone gets broken down, body gets Ca2+ from storage; bone gets rebuilt
What makes up the bulk of the mature bone?
Osteons. This consists of concentric rings of lamellae around a central Haversian canal.
osteon=concentric lamellae + central haversian canal
What are the cells of the Haversian canal?
- Osteoprogenioter cells
- Osteoblasts (secrete bony matric and differentiate into osteocytes)
- If the bone is remodeling: osteoclasts (break down bone to reabsorb Ca2+ into body)
osteo blasts, clasts, and cyte
For the diaphysis, ____bone surrounds it and we see ____ bone in the interior/
compact, spongy
Where do osteocytes (mature bone cells) site and how are they arranged?
Sit in lacunae and are arranged in the concnetric patterns resulting in the lamellar pattern( thin layers of compact bone)
osteocytes sit in lacinae (ECM) of lamellae (bone)
Ostoecytes have processes what are contained within what? What is the importance of this strucure?
Canaliculi. This allows cells to communicate and nutrients can diffuse from cell to cell. The ends of the processes contain gap jxns (made of connexin proteins)
canaliculi are small tunners that connect lacunae
Ostoecytes have processes what are contained within what? What is the importance of this strucure?
Canaliculi. This allows cells to communicate and nutrients can diffuse from cell to cell. The ends of the processes contain gap jxns (made of connexin proteins)
canaliculi are small tunners that connect lacunae
What is lacuna(lacunae)
small cavities in the boney matrix
What is an osteocyte?
Mature bone cell, support the matrix of the bone from insode
helps maintain matrix
What is canalicili?
hy
Small tunnels connecting lacunae, allow osteoytes to share transport system.
What are the precursor cells for osteocytes?
Osteoblasts. As the bone grows, they divide and some differentiate into osteocytes while other others will divide to produce more osteoblasts
What do osteoblasts secrete?
Collagen 1 and proteoglycans for bone matrix
osteoblasts secrete matric whihc surrounds the cell turning it into osteocyte. Osteoblasts lay down new bone
What are the cells surrounded by a lacunae in lamellae?
Osteocytes
What is the role of osteocytes?
Maintians bone matrix and does limited reabsorption to maintian blood calcium. They are not mitotically active
What are the major reabsoptive cells in bone?
Osteoclasts.
What do osteoclasts do?
They are active in bone remodeling and the uptake of calcium to maintian calcium balance,
Where do osteoclasts rest/sit in?
They sit in a depression called “Howships Lacunae” and they have a ruffled border. Lysosomes, hydrolytic enzymes and organic acids are released into lacuane to decalcify/break down.
Which hormone incr blood Ca2+?
Parathyroid hormone bc is stiumuates osteoclasts.
it will breakdown bone and release ca2+
What hormone decr blood Ca2+?
Calcitonon because it decr activitys of osteoclasts and incr fxn of osteoblasts to lay down new Ca2+
Osteoclasts are derived from where?
monocytic cell line
Where do osteoclasts and blasrs migrate during bone remodeling?
Clasts migrate along bone deteriorting pit into reasbsorption bays. Osteoblasts folow and lay new matrix
process is not uniform
Bones under constant ____ remodel faster than those that are not
stress
Summary of intramembranous bone formation
Mesenchymal cells differentiate into osteoblasts. Blasts secrete bony matrix called osteoid. Bone expands by appositional growth (add new bone to surface). As bony spicules enlarge they become interconnected into a trabecular arrangement.
bone matrix=osteoid
Endochondral bone formation
confusion slide 56/57
Zone of reserve
no isog groups
Zone of proliferation
isog groups formed
Zone of hypertrophy
Chondrocytes grow in size
Zone of ossification
acidophillic b/c new bone is formng.
staiened pink
What is the internal bone and what is is componsed of?
Spongy bone composed of meshed network of trabeculae.
They line up along the lines of stress and helps provide strength.
Does spongy bone have osteons?
NO, only compact does. Spongy has osetocytes connected with canaliculi and surrounded by lamellae
Process of endochondral ossification
- Perichodrium gets vascularized turning it into periosteum (bone)
- Mesenchymal cells surrounding cartilage then differentiates into osteoblasts to lay down new bone matrix
- Intramembranous bone formation (osteoblasts surround diaphysis with osteoid, when its calcifies it becomes a bony collar that surrounds hyaline)
- Chronrocyte hypertrophy: secrete alkaline phosphate which calcifies cartilage
- Chrondrocytes die and leave holes in cartilage
- Osteoclasrs break down the calcified cartilage
- More intra-membranous bone formation, leads to formation of trabeculae and meduallary cavity
Bone remodeling
Osteoblasts lay new bone and ocsteobclasts cut way bone in the cutting cone directions
Step 1 of fracture healing
Hematoma formation: blood clot forms and cells deprived of nutrients begin to die
bring in the blood
Step 2 of Fracture healing
Fibrocartilgenous callus forms
: Capillaries deliver fibroblasts to area which secrete collagen fibers to close wound and then secrete cartilage
Step 3 of fracture healing
Boneu callus forms: osteoblasts create new trabeculae that replaces cartilagenous matrix
Step 4 of fracture healing
osteoblasrs and osteoclasts appear and repair bone by adding compact bone. It looks like the orginial bc is undergoes the same streses.
What are the CT layes surrounding bone and cartilage called?
Bone: periosteum
Cartilage: perichondrium
What are the 4 cells involved in bone formation?
- Osteblasts
- Osteocytes
- Osteoclasts
- Osteoprogenitor cells
also see fibroblasrs laying collagen fibers
What type(s) of collagen arfe msot abundant in the matrix of bone and cartilage?
Bone: collag type 1
Cartilage:
-hyaline type 2
-elastic type 2
-fibrocart type 1
What hormone stimulates osteoclast activity?
PTH (parathyroid hormone)
calcitonin comes from thyroid
