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AoL > Limbs 1: Development & Growth of Bone > Flashcards

Limbs 1: Development & Growth of Bone Flashcards

1
Q

Function of bone

A 
Support of the body shape
System of levers for muscle action
Protection of internal organs
Site of blood cell formation
Mineral storage pool
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2
Q

What are the 2 mechanical properties of bone

A

Cable-like flexibility/resistance to TENSION

Pillar-like stiffness/resistance to COMPRESSION

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3
Q

What allows for cable-like flexibility in bone

A

collagen + other bone proteins (= osteoid)…. resistant to tension

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4
Q

What allows for pillar like stiffness in bone

A

by impregnation of collagen with crystalline mineral… allowing resistance to COMPRESSION

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5
Q

Which mineral is collage impregnated with in bone

A

(hydroxyapatite – a complex calcium hydroxyphosphate)… it’s crystalline

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6
Q

Types of bone tissue

A

Lamellar (=mature bone)

Woven (=immature bone)

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7
Q

T/f woven bone is commonly found in adult bone

A

F In adults woven bone is only found in repairing fractures… and pagets

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8
Q

What are the ends of bone called, and what is between this and the shaft

A

Ephiphysis (PROXIMAL= nearer to trunk, DISTAL=further)

metaphysis separates epiphysis from the shaft (diaphysis)

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9
Q

What is the name of the shaft

A

Diaphysis

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10
Q

What is the name of the hollow part inside bone

A

Medullary cavity

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11
Q

What is the name of the arteries that enter the epiphysis, metaphysis and diaphysis

A

Epi- eiphysial artery
Meta- metapyseal artery
Diaphysis - nutrient arteries which go through a nutrient foramen into the medullary cavity, then branch to supply the bone, and even back out to the periosteum

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12
Q

T/f periosteum is purely fibrous

A

F. it also is cellular

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13
Q

Role of periosteum

A

Key roles in bone growth and repair

Vascular

Sensory nerve supply is good

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14
Q

T/f periosteum is vascularised, but with poor sensory nerve supply

A

F… both vasuclarised and good sensory supply

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15
Q

What is an osteogenic cell

A

A cell which develops into an osteoblast (precurosr)

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16
Q

What is osteoblast a precursor to

A

osteocyte

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17
Q

What is the function of an osteoblast

A

forms bone marrix (i.e. secretes the collagen fibrils)

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18
Q

What is the function of osteocyte

A

Maintains bone tissue

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19
Q

T/F an osteocyte differentiates into an osteoclast

A

F, osteoblast forms osteocyte, but osteoclast separate

20
Q

Function of osteoclast

A

Resoprtion (breakdown of bone matrix using lysosomal enzymes)… they have ruffled border

21
Q

When does skeleton begin to form, when does growth stop

A

The skeleton starts to form at 6 weeks of fetal life and growth continues in some bones until 25 years of age.

22
Q

How is lamellar bone arranged

A

CORTICAL (Outer hard layer of compact lamellar bone)

TRABECULAR/CANCELLOUS/SPONGY (Inner layer of interlacing struts of lamellar bone)

23
Q

T/f spongy bone is woven as it is immature

A

FALSE!!! the spongy bone is lamellar…. woven is immature bone, which spongy bone is not

24
Q

Structure of cortical bone

A

Osteon, the chief structural unit of compact (cortical) bone, consisting of concentric bone layers called lamellae, which surround a long hollow passageway, the Haversian canal. Made up of osteocytes with lots of processes

As well as instersitital lamellae

25
Q

What is contained within the harvesian canal

A

neurovascular bundle

26
Q

Structure of trabecular bone

A

Trabeculae are the spikes, and there are spaces between them which bone marrow fits into

Also in concentric circles but not called osteons…. it’s all interstital lameallae. No harvesian canals running inside. Osteoblasts are aligned along trabeulae of new bone (underneath is the osteocyte network)

27
Q

State the 2 tpes of ossification and when each happens.. both in developng foetus

A

Intramembranous (in existing vascular connective tissue) –> FLAT BONES

endochondral (within existing foeatal cartilage models) –> OTHER BONES

28
Q

In which type of ossification is ostein deposited around collagen

A

Intramembranous

29
Q

What happens in intramembronous ossification

A

Mesenchymal stem cells within fibrous connective tissue (vascular connective tissue) differentiate into osteoblasts. These form ossification centres

Osteoid laid down (collagen). Osteoblasts which get trapped in the bone matrix called osteocytes

Mineralises to form spicules then trabeculae. This is woven bone

It then remodels further to form lamellar bone.

(note, there is still trabcular and cortical within this)

https://www.youtube.com/watch?v=xXgZap0AvL0

30
Q

What happens in endochondral ossification

A

Within existing cartilage

There are chondrocytes which are secreting a matrix. Enclosed in a perichondrium.

Then hypertrophy of chondrocytes in the centre of the cartilage model. They resorb the surrounding matrix. The remaining cartilage matrix is calficied and the condrocytes die

Stem cells in the perichondrium divide to form osteoblasts.

Periosteal bud with capillaries and osteoblasts invade the calcified cartilage reason–> Primary ossification centre. PERIPHERAL OSTEOCLASTS CUT CHANNELS FOR SPROUTING VESSELS

Bone is built on the calficied cartilagte

Then later on, a secondary ossification centre forms in the epiphysis. This replaces calcified cartilage with mostly spongy bone.

Osteoclasts resorb bone in the diaphysis creating medullar cavity.

The gap between the primary and secondary ossification centres is the epiphyseal growth plate…. all future growth oiccutrs here

An area of cartilage remains over the epiphysis *=articular cartilage)

31
Q

How does osteoblast get into foetal calcified cartilage

A

Periosteal osteoclasts cut channels for sprouting vessels

Osteoblasts enter with vessels to build bone round them

32
Q

Stages of intramembranous ossification

A

osteoblasts secrete osteoid, which they becomeme trapped in forming ossification centre

Osteoblasts become osteocytes… as they do this, they cause osteogenic cells to convert into osteoblasts… so you get osteocytes in the cnetre and a ring of osteoblasts around outside. Calficiation occurs

Osteocytes in the centre become trabecular bone and cortical bone

The new osteoblasts on the outside become periosteum

33
Q

Why is endochondral ossficiation needed

A

in children, there are large forces on the long bones, so you can’t really get frowth from the end of the bone (as it’s being compressed by force)….

34
Q

What is the solution fo disruption of terminal appositional growth due to large forces on bone

A
  1. Shaft ossified
  2. Epiphysis ossifies
  3. The region in between the ossified shaft and epiphysis conitnues growing (growing cartilage plate)….

the bit in between ossified epiphysis and diaphysis is called epiphyseal plate… it keeps growing, and then then becomes calcified, grows some more, that bit gets calfified etc.

35
Q

When will growth cessation occur

A

Growth cessation when cartilage growth ceases and plate is over-run by ossification

36
Q

State stages of endochondral ossification

A
  1. Primary ossification centre forms in the shaft. Shaft becomes calcified. At this stage the eiphysis is still cartlage
  2. Secondary ossification centre forms in epiphysis, and ossification ocrrus here..

epiphyseal plate left in between

37
Q

When does the child’s writst ossify

A

In child’s wrist (lower) epiphyses ossify in 2nd year

38
Q

When do eiphyseal paltes remain until

A

Epiphyseal plates (dark) remain cartilaginous until growth ceases after puberty

39
Q

What is the key to growth and remodelling in bones

A

large blood supply – cells are never far from nutrients and O2

Osteocytes maintain matrix but can activate osteoblasts for new bone building

Osteoclasts are giant cells specialised for destruction of bone matrix

40
Q

What is apposition

A

Apposition – addition to exterior at periosteum

41
Q

How does apposition occur

A

Osteoblasts and osteoclasts create ridges and grooves on bone surface

Blood vessels align in grooves

Osteoblasts build new osteons round vessels
Osteoclasts remove bone from endosteal surface

42
Q

Identify different fracture types

A

…

43
Q

How do fractures heal

A
  1. Bleeding- haematoma is infiltrated with fibrous matrix and invaded by cartilage/bone progenitors

The haematoma is contained within the periosteum

44
Q

What type of bone occurs in fracture repair

A

woven

45
Q

What if high blood Ca2+ level (hypercalcaemia)

A

Calcitonin released by parafollicular thyroid cells; breakdown of bone matrix by osteoclasts inhibited; uptake of Ca2+ into bone matrix is promoted.

46
Q

What if blood Ca2+ low

A

Parathyroid Hormone (PTH) released by chief cells of parathyroid gland; osteoclast bone resorption activity promoted; increases Ca2+ re-absorption by the kidneys.

47
Q

Outline he adaptable features of bone

A

Can grow without compromising its support functions

Increases or decreases bulk and density in response to pattern of use

Can alter its external and internal shape in response to pattern of use – remodelling

Can repair when fractured

AoL (9 decks)

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