Microanatomy Flashcards
what type of tissue is bone
- it is a connective tissue
what is the role of bone
- It provides a protective framework for the body
- permits locomotion
- acts as a store for minerals
- in a dynamic state of reabsorption and growth throughout life in order to accommodate changing mechanical stresses and demands of calcium homeostasis
what is the ECM called in bone
osteoid
what is the ECM (osteoid) made by
osteoblasts
what collagen is in bone
collagen type 1
what makes up the ECM in bone
- collagen type 1
- ground substance
- structural glycoproteins
what happens to the osteoid
- it is mineralised this makes sure that the bone is rigid and strong
what is the first bone produced by osteoblasts
the woven bone
what do osteoblasts become
- osteoblasts become osteocytes when they become more impeded int he matrix
what is the role of osteocytes
- they maintain the structural integrity of the matrix
- they respond to immediate blood calcium requirements by releasing and depositing calcium
- they create tunnels through the bone called resorption canals
how is the bone broken down
carried out by multinucleate macrophage like osteoclasts
what is the production of new one by osteoblasts called
it is called remodelling
what is lamellar bone
- highly ordered layered pattern of collagen
- remodelled bone
what is stronger, lamellar bone or woven bone
lamellar bone
what are the two types of bone
lamellar bone and woven bone
describe the structure of long bones
- have thick layers of compact bone on their shafts for strength
- at centres and at their ends the bone is cancellous (spongy)
- at the ends there is a thinner layer of compact bone this covers the cancellous bone
- articular cartilage is located at the joint
describe cancellous bone
- beams of bone are separated by spaces filled with bone marrow
- this maximises strength while reducing the overall weight
- when cancellous bone is in the shaft it is completely replaced by a large space filled with bone marrow called the medullary or marrow cavity
how does cancellous/tracecular bone appear in x rays
appears less dense
describe the structure of short flat and irregular bone
- outer bone is made up of compact bone and the inner bone is cancellous
- most of blood cell production in adults occurs in flat bones
- have a greater proton of red marrow
what are the two types of marrow
red marrow and yellow marrow
what is the difference between red marrow and yellow marrow
red marrow is where haematopoiesis takes place where as yellow bone marrow is comprised of adipose tissue
what bones make up flat bones
- scapular
- boens in cranial valut
- sternum
- ribs
what does decalficiation allow
this allows staining with normal H and E stain
why does the bone stain pink
the bone stains pink due to the high content of collagen type 1
what lines the surface of the trabecular
delicate layer of the endosteum which is made of a layer of osteoprogenitor cells, these are stem cells that are derived from mesenchymal cells
what do osteoprogneitor cells do
- these cells can differentiated into osteoblasts
- these are important for bone remodelling as well as repair following damage
what is compact bone organised into
compact bone is organised into lengthwise bone columns called haversian systems
what is a Haversian system
- this is a column, concerti bony lamellae surround a neuromuscular channel called haversian canal
- several layers of circumferential lamellae form the most outer surface of the bone
what do. volkmanns canals do
they run perpendicular to the haversain canals and bring the neruovascular supply into the compact bone and distribute it to haversian systems
what is the haversain canal and volkmanns canal lined with
endosteum
how are the osteocytes arranged in compact bone
- they are arranged in rows which delineate the layers or lamellae of the bone
why are the osteons not complete in compact bone
- this is because there is constant remodelling of the bone
what are osteoclasts
- these are multinucleate macrophage like cells
what is the role of osteoclasts in compact bone
- reabsorbing bone in the long term to blood calcium required
- change mechanical stresses
- create tunnel through the bone called resorption channels
what happens to resorption channels in compact bone
- osteocytes creates resorption channels
- osteoblasts then build a new osteon int he resorption canal
how do osteocytes get nutrients
- get it from canliculi
describe the structure of canlicuil
- these are fine tiny canals running through the bones
- appear in ground bone
- extend from the capillaries to the osteocytes in the matrix
how are the osteocytes interconnected
- they are interconnected by the cancliculi through which they send fine cytoplasmic processes and communicate via gap junctions
what is the outer surface of the bone surrounded by
surrounded by a fibrous capsule called the periosteum
what does the periosteum supply the bone with
- blood and neural supplyy
what is the inner layer of the periosteum lined by
- ## lined by osteoprogenitor cells - appear similar to fibroblasts on the surface of the adult bone
what is intramembranous ossifciation
this is the formation of bone form within a condensed layer or membrane of primitive mesenchymal tissue as occurs in flat bones
what is endchondral ossification
this is the formation of bone from a cartilage model as is typified by long bone development
what are the 4 stages of intramembranous ossification
- within the mesenchymal tissue - mesenchymal cells differntiate into osteoblasts and centres of ossification are formed
- osteoblasts secrete osteoid at the centre of ossification, mineralisation of the osteoid occurs which forms the spicules of bone
- the size of the ossification centres increases through differentiation of more osteoblasts and addition of more bone on their surfaces
- the group around fatal blood vessels in the mesenchymal membrane
- the centres meet and fuse to form a spongy bone
- mesenchyme condenses on the outer surface of the spongy bone forming a vascularised periosteum - further fusion of outer trabecular and periosteal bone formaton, the outermost bone forms into a continuous sheet of woven bone
- remodelling covnerts woven bone into lamellar compact bone with a haversian system
- the inner bone is remodelled into lamellar bone but remains trabecular
- mesenchymal cells within spaces of the tracebular bone differentiates into haemopoietic marrow cells
what bones form by intramembranous ossification
flat bones of the skull
what does the centre of the suture stain like
stains less pink due to the amount of collagen in it
what are stages 1 to 3 of endochrondral ossification
stages 1-3 is the development of the primary ossifciation centre
what bones develop via endochrondral ossification
long bones
what is covered by perichondrium in long bones
- the shaft 0 diaphysis
- future articular end portions - epiphyses
describe stages 1-3 of endochondral ossifications
- conversion of the perichondrium around the shaft of the cartilage model into a periosteum with osteogenic potential
- mesenchymal cells differentiate into osteoblasts and lay down a collar bone - the cartilage cells in the centre of the diaphysis enlarge therefor ether leave only thin intervening segments of cartilage matrix
- matrix becomes calcified and cells degenerated - a blood vessel - the nutrient artery - perforates the bony collar around the diaphysis and enters the central area of calcified cartilage
- the nutrient artery carries primitive mesenchymal cells and osteoprogenitor cells
- osteoprogenitor cells differentiate into osteoblasts and secrete osteoid and form bone on the remnants of the calcified cartilage
- trabecular bone is thus formed in the centre of the diaphysis this is called the primary ossification centre
what do stages 4-5 of endochondral ossification forms
they form the secondary ossifciation centres and the epiphyseal growth plate
describe stages 4-5 of endochondral ossification
- at the epiphyseal ends cartilage cells hypertrophy and die
- matrix becomes calcified and blood vessels carry osteoprogenitor cells into the area
- upon differentiation into osteoblasts the cells start to form trabecular bones in the centres of the epiphyses these sites are secondary ossification centres - bone continues to replace the cartilage in the epiphyses
- cartilage only remains on the articular surfaces at the joint and in a plate located between the diaphysis and epiphysis
- this plate is called the epiphyseal growth plate
- this allows the bone to continue to grow in length until the end of puberty
how does growth in width happen
appositional group
describe the process of appositional growth
- more bone is laid down by osteoblasts in the periosteum
- more cartilage is laid down on articulating surface by chondroblsats
- the remodelling of bone as a whole occurs to maintain the correct amounts of compact and trabecular bone and articular cartilage for the bone
how do bones growth in length
- long bones occurs as interstitial growth due tot eh events at the epiphyseal growth plate during endochondral ossification
what zones are from the epiphyseal side to the diaphysial side
- zone of resting or reserve cartilage
- zone of proliferation
- zone of maturation and hypertrophy
- zone of degeneration and calcification of cartilage matrix
- zone of osteogenesis
describe the zones of the epipsypehal growth plate
- the hyaline cartilage is found closest to the episypeal bone
- closer to the diaphysis the cartilage cells form columns of cells
- these cells then mature and hypertrophy
- cartilage starts to degenerate and there is death of chondrocytes
- then calcification of the intervening matrix happens
- invading capillaries from the marrow cavity of diaphysis carry osteoblasts into the spaces left by the dead chrondcocyte s
- osteoblasts produce new bone and form new trabecular bone that acts to lengthen the diaphysis
what name is given to the central shaft part of the bone
diaphysis
what are sharpers fibres
- dense collagen fibre bundles that insert into the bone matrix from the muscle
