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BL - SEM1 > Session 7: Bones, bone marrow, blood & blood vessels > Flashcards

Session 7: Bones, bone marrow, blood & blood vessels Flashcards

1
Q

Describe the bones of the axial and appendicular skeleton

A
  • 206 bones in total => 80 are axial and 126 are appendicular
  • axial = skull, laryngeal skeleton, vertebral column & thoracic cage.
  • appendicular = bones that attach to axial skeleton eg bones of shoulder, pelvis & limbs
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2
Q

What are the 2 types of bones?

A

Cancellous and compact/cortical bone

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3
Q

What is cancellous bone?

A
  • Sponge-like tissue inside bones
  • Forms networks of trabeculae (fine bony columns/plates)
  • Spaces between trabeculae are filled with bone marrow
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4
Q

What is compact/cortical bone?

A

Hard outer bone

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5
Q

What are osteoblasts, and what do they do?

A

Cells derived from mesenchymal stem cells.
They form new bone by laying bone tissue.

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6
Q

How do osteoblasts turn into osteocytes?

A

Once the osteblasts has surrounded itself with bone matrix, it becomes trapped in lacuna and becomes and osteocyte.

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7
Q

What are osteocytes and what do they do?

A

They are mature bone cells formed from osteoblasts that maintain bone.
Due to restrictive space, they cannot produce bone tissue

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8
Q

What are the types of cells found in bone?

A

Osteoblasts, osteocytes, osteoblasts and haematopoietic cells in bone marrow that produce RBCs

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9
Q

What are osteoclasts? What do they do?

A
  • Originate from haematopoietic stem cells
  • They break down bone tissue through the release of acid to release hydroxyapatite crystals and collagenase.
  • Remodel bone & regulate Ca2+ in blood
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10
Q

What processes is bone formed?

A

Endochondral ossification and intramembranous ossification

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11
Q

Describe the process of endochondral ossification.

A
  • Produces long bones from a cartilage template
  • Continued lengthening is by ossification at epiphyseal plates
  • Appositional growth => growth at edges, increases bone width
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12
Q

How do long bones develop?

A

Long bones require cartilage template to develop by endochondral ossification

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13
Q

Describe the process of intra-membranous ossification.

A
  • Formation of bone from clusters of mesenchymal stem cells in the centre of bone (trabecular of cancellous bone)
  • Interstitial growth = growth in the middle, outwards which increases bone length
  • Flat bone develops directly from mesenchymal tissue.
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14
Q

What is appositional growth?

A

Growing at the edges to increase bone width

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15
Q

What is interstitial growth?

A

Growth in the middle, outwards to increase bone length

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16
Q

Describe in 5 steps how bone trabeculae is formed.

A
  1. Osteoblast lays down bone tissue around itself
  2. Once surrounded by bone tissue, it becomes trapped within bone tissue and turns into osteocyte.
  3. Cement line = where new bone meets existing bone, more mineral is added so becomes bone and cement line moves
  4. Hydroxyapatite is deposited
    - Osteoclasts resorbs (break down)
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17
Q

What are calcium crystals called?

A

Hydroxyapatite crystals

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18
Q

Describe the conversion of cancellous bone to cortical bone in 5 steps.

A
  1. Mesenchymal cells convert osteoblast that line recently formed trabeculae
  2. Lay down bone tissue that is mineralised
  3. Osteoblats trapped => forms into osteocytes
  4. Steps 1-3 are repeated
  5. Central mesenchymal cells convert into blood, & lymph vessels and nerves
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19
Q

What is ECM made up of?

A

Collagen 1, proteoglycans and glycoprotiens

20
Q

What is the difference in structure between cancellous/cortical bone and cancellous bone?

A

Cortical/compact bone has Haversian and Volkmann’s canals whilst cancellous does not.

21
Q

Describe the structure of cortical/compact bone.

A

Made up of packed osteons which are made up of Haversian canal and Volkmann’sc canal.
Carry blood vessels, lymphatic vells and nerves

22
Q

What is the active form of Vitamin D called?

A

Calcitriol

23
Q

What does Vitamin D3 (calcitriol) deficiency lead to?

A

Less calcium is absorbed in the small intestine.
Less calcium absorbed means bones are less dense & strong

24
Q

How does reduced Ca2+ absorption lead to increased bone resorption and decreased bone mass?

A
  • Due to low levels of Ca2+ parathyroid hormone (PTH) will continue to be released (until [Ca2+] is high again).
  • PTH stimulates bone resorption.
  • Increased and continuous PTH production and release increases bone resorption which leads to decrease bone mass and increased risk of fracture & breakage.
25
Q

What occurs in osteogenesis imperfecta?

A
  • Mutation in COL1A gene
  • Incorrect synthesis of collagen 1 fibres during ossification
  • Bones are weak and brittle and are at high risk of fracture.
26
Q

Which age range does osteogenesis imperfecta occur in? How does it present

A

Mainly affects neonates & children
Presents as shortened height and stature

27
Q

What is the difference between rickets and osteomalacia?

A

Rickets affects children whilst osteomalacia affects adults.

28
Q

What causes rickets?

A

Vitamin D deficiency causing weakened bone development

29
Q

How do patients with rickets present?

A
  • Soft bones
  • Shortened height stature
  • Painful to walk
  • Bowed legs
30
Q

What causes osteomalacia?

A

Vitamin D deficiency => lower mineralisation (no or little hydroxyapatite => increased osteoid

31
Q

What causes increased calcium resorption in osteomalacia?

A
  • Kidney disease (kidney activates vitamin D so disease impairs ability)
  • Protection from sunlight (reduced sunlight uptake = less vitamin D)
  • Surgery of stomach or intestines (where Vitamin D is absorbed)
  • Drugs - phenytoin prevents vitamin D absorption
  • Low vitamin D/calcium-rich foods uptake in the diet => less Ca2+ absorbed -> increased bone resoption = weak & damaged bones
32
Q

What is osteoporosis?

A
  • Loss of bone matrix/tissue
  • Loss of structural density & mineralisation
  • Compression fractures
  • Shortened stature
  • Incomplete filling of osteoclasts resorption bays
33
Q

What are the RFs for Type 1 primary osteoporosis?

A
  • Postmenopausal women - reduced oestrogen causes increased osteoclast activity
34
Q

What are the RFs for Type 2 osteoporosis?

A
  • older men and women due to loss of osteoblasts function
  • loss of oestrogen AND androgen
35
Q

What are general RFs for osteoporosis?

A
  • Insufficient calcium intake
  • Lack of exercise - immobilisation of bone leads to accelerate bone loss, exercise maintains bone mass
  • Smoking
36
Q

What is achondroplasia?

A
  • An inherited mutation in FGF3 receptor gene.
  • FGF3 promotes collagen formation from cartilage => endochondral ossification is affected bu intra-membranous ossification is not affected
37
Q

How does achondroplasia present?

A
  • Short stature but normal-sized head & torso (flat bones unaffected)
  • Long bones cannot lengthen properly due to impaired endochondral ossification
38
Q

What are the 5 types of bones?

A

Long, short, flat, irregular and sesamoid

39
Q

Describe long bones. What is their function?

A
  • Longer than wide, appendicular skeleton including the femur and smaller bones of the finger.
  • Function: support the weight of the body and facilitate movement
40
Q

Describe short bones and their function.

A

As long as they are wide. Eg wrist and ankle joints
Function: provide stability and some movement\

41
Q

Describe flat bones and their function.

A

Flattened and roughly parallel opposite edges. Eg in skull, thoracic cage (sternum and ribs) and pelvis (ilium)
Function = protects internal organs and provides large areas of attachment for muscles

42
Q

Describe irregular bones and their function.

A

Vary in shape and structure, complex shape.
Functions = Protect internal organs, vertebrae, vertebral column, protect spinal cord, protects pelvis & important anchor points for muscle groups

43
Q

Describe sesamoid bones and their function.

A
  • Small, round bones in tendons, knees and feet eg patella
    Function: Protects tendons from stress and damage from repeated wear and tear
44
Q

Where is bone marrow found?

A

Between trabeculae in cancellous bone

45
Q

Describe red marrow.

A
  • Rich blood supply
  • Full of developing blood cells
  • Only found in spongy bone
    Function is to replenish cells in the blood (haemopoiesis)
46
Q

Describe yellow marrow.

A
  • Full of adipocytes
  • Poor blood supply
    Function is to act as shock absorber & energy source. It can convert to red marrow.
47
Q

Where is bone marrow found?

A

Ribs, vertebrae, sternum and bones of pelvis

BL - SEM1 (7 decks)

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