Session 12 Body Logistics BONE Flashcards
Name the two types of ossification
- ENDOCHONRAL Ossifcation
- INTRAMEMBRANOUS Ossification
WHAT ARE THE DIFFERENCES BETWEEN THE TWO TYPES OF OSSIFICATION?
-ENDOCHONDRAL OSSIFICATION- the formation of bone from a cartilage template
-Lengthening of bones via further ossification at their EPIPHYSEAL GROWTH planes
- Involves LONG bones of the body eg ribs and limbs ( most bones of the body)
INTRAMEMBRANOUS OSSIFICATION- Directly from MESENCHYMAL TISSUE ( condensations of mesenchymal tissue)
- You also have intramembranous ossification occuring at the long bones - contributes to thickening of long bone at periosteal surface (appositional growth)
- Involves Flat bones - eg Skull, Scapula, Pelvis and Clavicle
DESCRIBE THE TWO DIFFERENCES BETWEEN THE TWO TYPES OF OSSIFICATION
- Endochondral ossification-hyaline cartilage template for ossifcation (long bones- ribs, limbs
- Intramembranous ossification-condensation of mesenchymal tissue no cartilage (flat bones- clavicle, scapula, skull, pelvis -seen in long bones for thickening )
GIVE EXAMPLES OF FLAT BONE FORMED BY INTRAMEMBRANOUS OSSIFICATION
- Skull ( temporal, mandible, maxilla, parietal , occipital, frontal)
- Clavicle ( medial end - endochondral and lateral -intramembranous)
- Scapula ( have some peripheral cartilage therefore some E.oss)
- Pelvis ( have some E.oss possibly)
WHAT IS THE FIRST BONE TO BEGIN OSSIFCATION AND THE LAST TO FINISH OSSIFYING?
- Clavicle
- Growing up to age 25 in some males.
DESCRIBE THE 5 STAGES OF INTRAMEMBRANOUS OSSIFICATION
- Small cluster of MSCs form a NIDUS (Tight cluster of cells)
- MSCs become Osteoprogenitor cell ( each cell increase develop GA and RER)
- 3.Osteoprogenitor cell—> Osteoblasts and lay down ECM with T1 Coll
- 4.Osteoid mineralised form rudimentary bone tissue SPICULES - that are surrounded by osteoblasts and contain OSTEOCYTES
- SPICULES join to form TRABECULAE which is finally replaced by lamellae of mature spongy bone
WHAT HAPPENS WHEN A SPICULE IS FORMED?
OSTEOCYTES, OSTEOBLASTS AND OSTEOCLASTS remodel i in the same way regardless if the initial ossification was endochondral or intramembranous
Name and state the function of the three specialised bone cells
- Osteocytes - Osteoblasts trapped in new osteoid - still living
- Osteoblasts- Deposit new osteoid
- Osteoclasts- Resorb bone and sit in the resulting depression
THE PRESENCE OF WHAT MAKES BONE ARISING FROM ENDOCHONDRAL ADN INTRAMEMBRANOUS OSSIFICATION INDISTINGUISHABLE
- PRESENCE OF : -OSTEOCYTES
- OSTEONS
- HAVERSIAN CANNALS
- VOLKMANN’S CANNALS
WHAT ARE THE TWO TYPES OF BONES WE SEE IN A BONE
EG. A DRIED FEMUR
- Cancellous ( spongy / trabecular bone)- forms network of fine bonds columns which combine STRENGTH AND LIGHTNESS
- Spaces filled with bone marrow
- Compact bone (cortical) - forms EXTERNAL surfaces of bone
- Contributes to 80% of skeletal mass
WHICH BONE CONTRIBUTES MOST TO THE BODY’S SKELETAL MASS?
- COMPACT (CORTICAL) BONE -80% OF BODY’s skeletal mass
WHAT DO HAVERSIAN AND VOLKMANNS CANALS CARRY?
- Blood vessels
- Lymphatics
- Nerves
WHAT IS THE DIFFERENCE BETWEEN VOLKMANN’S AND HAVERSIAN CANNALS?
- Haversian CANNALS- tend to run longitudinally
- SURROUNDED BY CONCENTRIC LAMELLAE ( making an osteon)
-VOLKMANN’S CANNALS - tend to round horizontally between H.cannals. DO NOT HAVE CONCENTRIC LAMELLAE around them!
Describe the difference between immature and mature bone
- Immature bone- OSTEOCYTES arranged randomly
- Mature bone - OSTEOCYTES arranged in the concentric lamellae of osteons
- Resorption cannals in mature bone run parallel with the osteon’s long axes (cutting zone)
Describe the osteocytes in lacunae between lamellae ( in cortical bone)
- Osteocytes slender cytoplasmic projections which interact with adjacent osteocytes via caniculi
- Process connect with adjacent osteocytes via GAP junctions allow the transfer of nutrients
- Caniculi connect with central Haversian system
DIFFERENCE BETWEEN CORTICAL AND SPONGY BONE
- Haversian system with the concentric lamellae- osteon- cortical bone
- Spongy bone have trabeculae which have no haversian or volkmanns canal although there are osteocytes between lamellae
- have bone marrow all around the trabeculae
Spongy bone structure
- Trabecule similar to compact bone with osteocytes between lamellae
But no haversian and volkmann canals
Each trabeculae has numerous osteocytes embedded in irregular lamellae of bone ( dispose tissue and haemopoeitic cells in the cavity)
-Osteoblasts and Osteoclasts on their surface act to remodel it
What is a cutting cone?
- Is boring a tunnel brought the bone via action of osteoclasts
- Osteoclasts release H+ and lysosomal enzymes
- Minute its cut and bone is removed by Osteoclasts, osteoblasts lay down osteoid
WHAT IS OSTEOID?-
- ORGANIC CONTENT OF BONE
- UNMINERALISED
- 90% COLLAGEN
- 10% GROUND SUBSTANCE
WITH THE BONE REMODELING WHAT DO WE SEE IN TERMS OF HAVERSIAN SYSTEMS?
You have first, second, third generation Haversian system
- Can see remnants of old Haversian systems
- (have movement of osteons)
What is the ability of osteons?
- Ability to branch and terminate
WHAT IS THE STRUCTURE OF CORTICAL (compact) BONE?
- compact bone is organised into parallel columns- Haversian systems
- H.s - composed of concentric lamellae (parallel H.C and perpendicular V.C)
- Lamellae of H.S created by osteoblasts which secrete matrix and trapped in a lacunae- osteocytes
What are the Layers of Long bone from exterior - in?
- PERIOSTEUM - surface of cortical bone
- Outer circumferential lamellae
- Compact bone- Haversian system
- Inner circumferential lamellae
- ENDOSTEUM ( Endosteal surface of trebacullar bone)
WHAT IS THE COMPOSITION OF BONE?
- 65% Mineral ( calcium hydroxyapatite crystals)- contributes to hardness of bone
- 23%- TYPE 1 COLLAGEN
- 10% Water
- 2% non-collagen proteins
HOW CAN BONE RESIST FRACTURE?
- Bones - high tensile and compressive strength
But also has a DEGREE OF FLEXIBILITY
-Lamellae slid past each other before excessive load causes fracture
Bone breaks - multiple broken blood vessels - haematoma occurs
DESCRIBE THE FRACTURE REPAIR OVERVIEW
- HAEMATOMA FORMAATION- blood clot formed in which granulation tissue forms
- Fibrocartilaginous callus formed - Pro callus of granulation tissue replaced by fibrocartilaginous callus in which bony trabeculae develop
- Bony callus formation- Endochondral and intramembranous ossification have a bony callus of spongy bone
- Bone Remodelling- Spongy bone replaced by CORTICAL bone until remodelling complete.
In detail describe the first stage of fracture repair
*periosteum can stay intact unless you have a really bad fracture.
- Haematoma formation because blood vessels in bone and periosteum break *
- Bone cells at edge of fracture die - lack of blood supplying
- Inflammation and swelling
- PHAGOCYTIC AND OSTEOCLASTS cells begin the remove the dead and damaged tissue
- Macrophages will eventually remove the blood clot.
Describe the second stage of fracture repair
- FIBROCARTILAGINOUS CALLUS FORMED
- New blood vessels infiltrate the fracture haematoma
- Pro callus of granulation tissue develops (rich in capillaries and fibroblasts)
- Fibroblasts produce collagen which spans the break.
- Other (FB’s) differentiate into chondroblasts - created a sleeve of hyaline cartilage
- External fibrocartilaginous matrix splints the fracture
- Osteocytes from nearby periosteum and endosteum invade the fracture site and begin bone reconstruction forming spongy bone
Describe the Third stage of Fracture Repair
- BONY CALLUS FORMATION
- New bone trabecule appear in the fibrocartilaginous callus
-Trabeculae develop as the fibrocartilaginous callus is converted to bony callus (spongy bone)
- E.oss replaces the cartilage with spongy bone , I. Oss - new spongy bone formed in area.
These process begin in 2 days after fracture in young people
- The formation of BONY CALLUS continues for 2MONTHS until a firm union is formed
Describe the final stage of fracture repair in detail
- BONE REMODELLING
- As soon as the bony callus (spongy bone formed) is remodelled into COMPACT bone especially cortical areas
- Bone remodelling takes several months
- The material bulging from the outside inwards in to the medullary cavity removed by OSTEOCLASTS.
- FINAL shape of remodelled area = same as the original unbroken bone as it responds to the same set of mechanical stressors.
What are bone banks and what they used for?
- If a fracture involves the loss of bone fragments ( which you can see in an RTA)- bony union and callus formation can not occur
- Bone banks available for grafts- used by orthopaedic surgeons
- Autografts- donor recipient - most successful
- Homograft- donor different human- can be rejected as foreign
- Heterograft- donor =different species (calf bone loses anitgenicity in refrigeration)
WHAT IS OSTEOPOROSIS?
- Metabolic bone disease
- Mineralised bone content is decreased in mass to the point where it does not provide enough mechanical support
- Have increased bone resorption in comparison to bone formation
- loss of bone mass with in trabecular bone therefore, increased suspectibility to fracture . ( Trabeculae normally strong and thick)
What exactly happens in osteoporosis?
- Outer surfaces of bony trabecule of spongy bone are regularly remodelled via Osteoclasts resorption and osteoblasts desposition.
- *Osteoporosis is associated with ageing where you have incomplete filling of Osteoclasts resorption bays.
- have compression fracture where bone begins to break away
How does osteoporosis alter our shape?
- You have compression fracture which results in bone breaking away!
- in the voter rally body of the spine or have loss of bone tissue therefore vertebrate begins to break away - Have bending off Spine and compression of spine.
WHY IS OSTEOPOROSIS A RISK FACTOR FOR THE ELDERLY?
- Bone mass peaks between 25-35 years
- It declines in 5th and 6th decade
Amongst whites women 2x risk of hip fracture as men
8x risk of vertebral fracture as men
WHAT ARE THE TWO TYPES OF PRIMARY OSTEOPOROSIS
- Type one - occurs in post menopausal women
- Caused by an increase in Osteoclasts number - due to decrease in oestrogen
- Type two- Occurs in elderly - both women and men (senile osteoporosis)
- Generally occurs after 70 - due to attenuated osteoblasts function
What are the 4 risk factors of osteoporosis?
- Genetic peak one mass higher in blacks than whites and asians
- Insufficient Caclium intake - recommended caclium intake potmenopausal women 800mg/day
- Exercise- Imobilisation of bone ( prolonged bed rest/ application of cast)- accelerated bone loss . Physical activity needed to maintain bone mass. Weightlessness experienced by astronauts can result in osteoporosis.- therefore they have to exercise
- Cigarette smoking- women increased correlation with OP
OSTEOMALACIA VERSUS OSTEOPOROSIS
- Osteomalacia - you have mineral deficiency - vitamin D ca2+ levels decreased- Soft bones
- Osteoporosis -hard bone lots of holes - trabeculae decrease in mass decreased strenght.
