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Body Logistics > Lecture 13: Bone, BM, vessels & blood > Flashcards

Lecture 13: Bone, BM, vessels & blood Flashcards

1
Q

Name the bone functions.

A

-Mechanical: protect tiss/organs
framework for overall body shape
levers for movement

-Synthetic: haemopoiesis

-Metabolic: mineral storage (Ca2+, P)
Fat storage (yellow BM)
Acid-base homeostasis (regulate blood pH)

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2
Q

What are the 2 types of bone called and where can you find them?

A

Cancellous/Trabecular bone: spongey, fine trabeculae with many spaces filled with BM; found in the internal spaces.

Compact/Cortical bone: mineralised hard bone making up 80% skeletal mass; forms the external surfaces.

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3
Q

Describe the 2 types of ossification.

A

Endochondral: forms the long bones of the body from a cartilage template.

Intra-membranous: forms flat bones from mesenchymal stem cells in the cancellous bone: interstitial growth (centre –> out)

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4
Q

Briefly describe what you would see in a histogram of intramembranous ossification.

A

Most likely a histogram of flat bone growth.

  • periosteum surrounding the newly formed bone
  • osteoblasts lining the mesenchymal tiss. (almost like epithelia)
  • osteocytes embedded within the newly formed bone
  • multinucleated osteoclasts on the edge of mesenchymal tiss.
  • might find new bone spicule in the middle of mesenchymal tiss, as interstitial growth
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5
Q

What is an osteocyte?

A

A bone cell (osteoblast) surrounded by new osteoid (bone substance).

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6
Q

What is an osteoblast?

A

A cell that secretes osteoid so is responsible for new bone formation.

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7
Q

What is an osteoclast?

A

A large multinucleated bone cell which remodels bone by releasing enzymes.

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8
Q

How is cancellous bone converted into cortical bone?

A
  1. MSC develop into osteoblasts that form trabeculae.
  2. They lay down osteoid that is mineralised.
  3. Osteoblasts within osteoid become osteocytes
  4. Steps 1-3 are repeated to form non-parallel lamellae (rings)
  5. Central MSC are converted into Haversian & Volkmann’s canals.
  6. This forms an osteon.
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9
Q

Structurally, what is the difference between immature and mature bone?

A

Immature bone has osteocytes in random arrangements.

Mature bone has osteocytes arranged in concentric lamellae in osteons.

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10
Q

Describe the reabsorption canals in mature bone.

A

They run parallel to the osteon long axes and act as the starting point of bone remodelling.

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11
Q

Describe the structure of compact bone.

A

Concentric lamellae in osteons
Haversian and Volkmann’s canals
Periosteum membrane surrounding bone

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12
Q

Describe the structure of trabecular bone.

A

Spaces filled with BM
Osteocytes lie between lamellae
No Haversian or Volkmann’s canals
Osteoblasts/clasts peripheral to lamellae

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13
Q

What do the Haversian and Volkmann’s canals carry?

A

Blood, lymph vessels and nerves.

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14
Q

Describe the composition of bone.

A

65% minerals
23% collagen 1
10% water
2% other proteins

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15
Q

How can bone resist relatively great tension and fractures?

A

Bones have high tensile, compressive strength and is quite flexible: water between the lamellae so the lamellae can slip over each other. Reduces excessive force so bone more resistant.

Epiphysis (end of long bone) is larger than the shaft (diaphysis) so applied force is spread out at the opposite end.

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16
Q

How do bones get thicker?

A

Bone is constantly (re)modelling itself.

  1. Osteoclasts form a cutting cone in the cortical bone.
  2. They create an acidic environment and release enzymes that resorb bone.
  3. Then osteoblasts form a closing cone which deposits osteoid which is mineralised.
  4. Some osteoblasts are embedded within the osteoid so they become osteocytes.

Hence bone gets thicker.

17
Q

What is osteoid?

A

Non-mineralised bone matrix (collagen and GS) that is secreted by the osteoblast.

18
Q

What are some factors affecting bone stability?

A

Activity of osteocytes: can act as osteoblasts/clasts as well - increased by oestrogen/TH

Activity of osteoblasts: increases bone stability - oestrogen, testosterone, TH, GH, vit. A, (think puberty)

Activity of osteoclasts: increased by PTH - releases Ca2+ into blood

Nutrition: vit. D3-produces calcitriol ( Bone Ca absorption)

vit. C- collagen synthesis and stability
vit. K and B12-syn. of bone proteins

19
Q

What causes osteogenesis imperfecta (brittle bone disease)? Signs & symptoms?

A

Mutation in COL1A gene so the wrong collagen 1 fibres are produced.
Results in weak bones so more likely to have fractures.
Mostly affects neonates/children.
Tends to have shortened stature as bones don’t repair properly.

20
Q

What is rickets? What is the cause? Signs & symptoms?

A

Bone condition affecting children due to vit. D deficiency.
Poor vit D in diet means less mineralisation of osteoid - lower mineral:osteoid ratio so weak bone development.

  • Shortened height/stature
  • Painful to walk
  • Bowed legs
21
Q

What is osteomalacia? Cause, signs & symptoms?

A 
Adult rickets (essentially) caused by vit. D deficiency and higher osteoclast activity
Causes low mineralisation so low mineral:osteoid ratio
22
Q

What is osteoporosis? How is it classified?

A

Loss of overall bone mass due to higher osteoclast activity, so there are more holes in the cortical bone.

1° type 1: occurs in postmenopausal women as lack of oestrogen to inhibit osteoclasts

1° type 2: AKA senile osteoporosis. Both older sexes as decrease osteoblast activity (incomplete resorption bays) due to insufficient oestrogen and androgen.

2°: indirect effect due to drug therapy; malnutrition; prolonged immobilisation; weightlessness; metabolic bone diseases.

23
Q

Why can someone with chronic osteoporosis end up with a “widow’s hump”?

A

Osteoporosis means that there is a higher osteoclast activity. Meaning a higher risk of multiple compression fractures in the vertebrae due to bone tiss. loss. This can lead to a widow’s hump.

24
Q

What are some factors that increase the likelihood of developing osteoporosis?

A
  • insufficient Ca intake
  • lack of exercise: bone immobilisation leads to accelerated bone loss as movement maintains bone mass.
  • smoking: oestrogen affected by smoking
25
Q

What is the difference between osteomalacia and osteoporosis?

A

Osteomalacia is where there is less mineralisation in the same mass of bone hence softer bones: low minerals:osteoid ratio.

Osteoporosis is where there is less bone mass overall: same mineral:osteoid ratio.

26
Q

Describe achondroplasia.

A

An inherited mutation condition where the fibroblast GF affects collagen formation in cartilage.
This affects endochondral ossification and NOT intramembranous ossification as the latter is formed from MSC.
Results: long bones affect (so shorter limbs) but flat bones not affected so normal sized head & torso.

27
Q

What are the 5 types of bone?

A 
long bones
short bones
flat bones
irregular bones
sesamoid
28
Q

Describe and give some examples of long bones with their functions.

A

They are longer than they are wide.
They facilitate movement and support body’s weight.

tibia
fibula
humerus
radius
phalanges
femur
ulna
metacarpal
metatarsal
29
Q

Describe and give some examples of short bones with their functions

A

They are as long as they are wide. They provide stability and facilitate some movement.

Carpals (wrist joint)
Tarsals (ankle joint)

30
Q

Describe and give some examples of flat bones with their functions

A

They are somewhat flattened and have essentially parallel opposite sides. You can also see light through most of them.
They protect internal organs; provide large SA for muscle attachment.

Cranial (skull)
Sternum (breast bone)
Ribs
Ilium (pelvic)
Scapula (shoulder blade)
31
Q

Describe and give some examples of irregular bones with their functions

A

They follow no pattern of shape or structure. They protect internal organs (spinal cord, bladder, genitalia); provide anchor points for muscle groups.

Vertebrae
Sacrum

32
Q

Describe and give some examples of sesamoid bones with their functions

A

They are small, round bones found usually in tendons of hands, feet and knees. They protect tendons from stress and damage from repeated wear & tear.

Patella

33
Q

What is different about sesamoid bones compared to the other types?

A

Sesamoid bones only develop only when you begin walking; after birth. The other bones are developed prenatally.

Body Logistics (13 decks)

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