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Body Logistics SEM1 YR 1 > Session 12 Body Logistics BONE > Flashcards

Session 12 Body Logistics BONE Flashcards

1
Q

Name the two types of ossification

A
  • ENDOCHONRAL Ossifcation

- INTRAMEMBRANOUS Ossification

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2
Q

WHAT ARE THE DIFFERENCES BETWEEN THE TWO TYPES OF OSSIFICATION?

A

-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

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3
Q

DESCRIBE THE TWO DIFFERENCES BETWEEN THE TWO TYPES OF OSSIFICATION

A
  • 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 )
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4
Q

GIVE EXAMPLES OF FLAT BONE FORMED BY INTRAMEMBRANOUS OSSIFICATION

A
  • 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)
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5
Q

WHAT IS THE FIRST BONE TO BEGIN OSSIFCATION AND THE LAST TO FINISH OSSIFYING?

A
  • Clavicle

- Growing up to age 25 in some males.

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6
Q

DESCRIBE THE 5 STAGES OF INTRAMEMBRANOUS OSSIFICATION

A
    1. Small cluster of MSCs form a NIDUS (Tight cluster of cells)
    1. 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
    1. SPICULES join to form TRABECULAE which is finally replaced by lamellae of mature spongy bone
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7
Q

WHAT HAPPENS WHEN A SPICULE IS FORMED?

A

OSTEOCYTES, OSTEOBLASTS AND OSTEOCLASTS remodel i in the same way regardless if the initial ossification was endochondral or intramembranous

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8
Q

Name and state the function of the three specialised bone cells

A
  • Osteocytes - Osteoblasts trapped in new osteoid - still living
  • Osteoblasts- Deposit new osteoid
  • Osteoclasts- Resorb bone and sit in the resulting depression
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9
Q

THE PRESENCE OF WHAT MAKES BONE ARISING FROM ENDOCHONDRAL ADN INTRAMEMBRANOUS OSSIFICATION INDISTINGUISHABLE

A
  • PRESENCE OF : -OSTEOCYTES
  • OSTEONS
  • HAVERSIAN CANNALS
  • VOLKMANN’S CANNALS
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10
Q

WHAT ARE THE TWO TYPES OF BONES WE SEE IN A BONE

EG. A DRIED FEMUR

A
  • 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
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11
Q

WHICH BONE CONTRIBUTES MOST TO THE BODY’S SKELETAL MASS?

A
  • COMPACT (CORTICAL) BONE -80% OF BODY’s skeletal mass
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12
Q

WHAT DO HAVERSIAN AND VOLKMANNS CANALS CARRY?

A
  • Blood vessels
  • Lymphatics
  • Nerves
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13
Q

WHAT IS THE DIFFERENCE BETWEEN VOLKMANN’S AND HAVERSIAN CANNALS?

A
  • 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!

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14
Q

Describe the difference between immature and mature bone

A
  • 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)
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15
Q

Describe the osteocytes in lacunae between lamellae ( in cortical bone)

A
  • 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
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16
Q

DIFFERENCE BETWEEN CORTICAL AND SPONGY BONE

A
  • 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
17
Q

Spongy bone structure

A
  • 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
18
Q

What is a cutting cone?

A
  • 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
19
Q

WHAT IS OSTEOID?-

A
  • ORGANIC CONTENT OF BONE
  • UNMINERALISED
  • 90% COLLAGEN
  • 10% GROUND SUBSTANCE
20
Q

WITH THE BONE REMODELING WHAT DO WE SEE IN TERMS OF HAVERSIAN SYSTEMS?

A

You have first, second, third generation Haversian system

  • Can see remnants of old Haversian systems
  • (have movement of osteons)
21
Q

What is the ability of osteons?

A
  • Ability to branch and terminate
22
Q

WHAT IS THE STRUCTURE OF CORTICAL (compact) BONE?

A
  • 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
23
Q

What are the Layers of Long bone from exterior - in?

A
  1. PERIOSTEUM - surface of cortical bone
  2. Outer circumferential lamellae
  3. Compact bone- Haversian system
  4. Inner circumferential lamellae
  5. ENDOSTEUM ( Endosteal surface of trebacullar bone)
24
Q

WHAT IS THE COMPOSITION OF BONE?

A
  • 65% Mineral ( calcium hydroxyapatite crystals)- contributes to hardness of bone
  • 23%- TYPE 1 COLLAGEN
  • 10% Water
  • 2% non-collagen proteins
25
Q

HOW CAN BONE RESIST FRACTURE?

A
  • 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
26
Q

DESCRIBE THE FRACTURE REPAIR OVERVIEW

A
  1. HAEMATOMA FORMAATION- blood clot formed in which granulation tissue forms
  2. Fibrocartilaginous callus formed - Pro callus of granulation tissue replaced by fibrocartilaginous callus in which bony trabeculae develop
  3. Bony callus formation- Endochondral and intramembranous ossification have a bony callus of spongy bone
  4. Bone Remodelling- Spongy bone replaced by CORTICAL bone until remodelling complete.
27
Q

In detail describe the first stage of fracture repair

*periosteum can stay intact unless you have a really bad fracture.

A
  1. Haematoma formation because blood vessels in bone and periosteum break *
  2. Bone cells at edge of fracture die - lack of blood supplying
  3. Inflammation and swelling
  4. PHAGOCYTIC AND OSTEOCLASTS cells begin the remove the dead and damaged tissue
  5. Macrophages will eventually remove the blood clot.
28
Q

Describe the second stage of fracture repair

A
  1. 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
29
Q

Describe the Third stage of Fracture Repair

A
  1. 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
30
Q

Describe the final stage of fracture repair in detail

A
  1. 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.
31
Q

What are bone banks and what they used for?

A
  • 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)
32
Q

WHAT IS OSTEOPOROSIS?

A
  • 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)
33
Q

What exactly happens in osteoporosis?

A
  • 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
34
Q

How does osteoporosis alter our shape?

A
  • 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.
35
Q

WHY IS OSTEOPOROSIS A RISK FACTOR FOR THE ELDERLY?

A
  • 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
36
Q

WHAT ARE THE TWO TYPES OF PRIMARY OSTEOPOROSIS

A
  • 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
37
Q

What are the 4 risk factors of osteoporosis?

A
  1. Genetic peak one mass higher in blacks than whites and asians
  2. Insufficient Caclium intake - recommended caclium intake potmenopausal women 800mg/day
  3. 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
  4. Cigarette smoking- women increased correlation with OP
38
Q

OSTEOMALACIA VERSUS OSTEOPOROSIS

A
  • Osteomalacia - you have mineral deficiency - vitamin D ca2+ levels decreased- Soft bones
  • Osteoporosis -hard bone lots of holes - trabeculae decrease in mass decreased strenght.

Body Logistics SEM1 YR 1 (2 decks)

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