Bone Flashcards

1
Q

What are the cells which are found in bone

A

Osteoprogenitor cells

Osteoblasts

Osteoclasts

Osteocytes

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2
Q

What is contained in the extracellular matrix

A

Collagen

Calcium hydroxyapatite

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3
Q

What makes up bone

A

Cells

Extracellular matrix

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4
Q

What are osteoblasts and osteoclasts derived from

A

Embryonic mesenchyme - osteoprogenitor cells - form a stem cell population within bones

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5
Q

What do osteoblasts secrete

A

Osteoid

Unmineralized bone

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6
Q

Define osteocytes

A

Osteoblasts which have become trapped within mineralised (within there own matrix) bone

Function unknown - suspected to do with calcium

Connect to surrounding cells via canaliculi - oxygen

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7
Q

Describe osteoclasts

A

Derived from monocytes

Multinucleated cells

Absorb bone - as they do become dropped which they sit in Howship’s lacunae

Activity is linked to that of osteoblasts - coordinated such as RANK-L

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8
Q

What is bone

A

A dynamic living tissue

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9
Q

What are the ways in which bone can be typed

A

Origin

Mode of formation

Gross appearance

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10
Q

What are the types of origin

A

Primary (woven)

Secondary (lamellar)

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11
Q

What are the types of mode of formations

A

Membranous

Endochondrial

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12
Q

What are the divisions by gross appearance

A

Spongy/cancellous
Compact

Osteons
Appositional

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13
Q

What is osteoid

A

Osteoblasts extracellular matrix created

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14
Q

Describe secondary bone

A

Also called lamellar bone

Stronger than primary (woven) bone

Forms osteons

Central haversian canal containing blood vessels

Surrounding concentric rings of lamellar bone with osteocytes

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15
Q

What are the two ways in which bone can form

A

Intramembranous

Endochondrial

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16
Q

What bones are formed from intramembranous formation

A

Flat bones of the skull

Some cortical bone shafts

17
Q

What bones are formed from endochondrial formation

A

All other bones

(expect those formed by intramembranous)

18
Q

Describe intramembranous ossification

A

Formation of bone from a membrane precursor

Bone is deposited directly in a primitive embryonic mesoderm without a cartilaginous proforma

Starts in 2nd trimester of embryonic life

Small clusters of progenitor cells within a primitive mesenchyme transform into osteoblasts and deposit isolated islands of bone

The islands enlarge creating a meshwork of bone

Osteoblasts will continue to deposit until all holes are filled in - create primary plate of bone

Overtime woven bone will be remodelled to lamellar bone

19
Q

Describe endochondrial ossification

A

Hyaline cartilaginous template into bone

Cartilaginous proformas form during 2nd trimester of intrauterine life

Shaft/diaphysis becomes calcified and blood vessels grow into the developing bone

osteoprogenitor cells differentiate into osteoblasts, lay down bone to form primary centre of ossification

Profomer cartilage is eroded away as new bone forms

Later secondary centres of ossification form in the heads/epiphysis of bones

By birth most bones have primary centre of ossification and some have secondary

As ossification centre expand cartilage becomes restricted to epiphyseal growth plates that separate epiphysis from diaphysis

Cartilage remains on articular surface

20
Q

Describe synovium

A

Lines the inside of the joint capsule

1-4 layers of synovial cells

Type A - phagocytes
Type B - rich in rER

Variable shapes - squamous to cuboidal

Richly vascular, highly innervated

21
Q

Describe the hyaline cartilage of the proformers

A

Synthesised by chondroblasts that differentiate from progenitor cells within the embryonic connective tissue (mesenchynme)

Produce a glassy amorphous looking matrix within which the cells become trapped causing them to transform into less synthetically active chondrocytes

Cartilage is encapsulated by a fibrous perichondrium that contains both progenitor cells and differentiated chondroblasts

22
Q

What are the features of osteoclasts

A

Occur frequently in developing bone even from the outset

Multi-nucleate cells digest bone

Play a significant part in the remodelling of bone during growth phase

23
Q

What is the first type of bone to be produced

A

Primary bone

24
Q

How can secondary bone occur as

A

Open framework (woven bone)

Compact lamellae

Osteons

25
Q

How does long bone increase in length

A

By adding new bone at the epiphyseal plates

Heads are re-sculpted and additional bone is added to the outside of the shaft