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Body Logs > Bones > Flashcards

Bones Flashcards

1
Q

Bone functions

A

Mechanical
-protect tissues/organs; provide framework; form bases of levers

Synthetic
-haemopoiesis

Metabolic
-mineral storage (calcium and phosphorus); fat storage (yellow bone marrow); acid-base homeostasis (absorbs or releases alkaline salts)

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2
Q

Cancellous bone

A

Network of fine bony columns or plates called trabeculae, spaces are filled by bone marrow.

Aka spongy bone.

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3
Q

Compact bone

A

Forms the external surfaces of names bones and comprises 80% of body’s skeletal mass.

Aka cortical bone.

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4
Q

Endochondral ossification

A

Formation of long bones from cartilage template; continued lengthening is by ossification of at epiphyseal plates.

Appositional growth (growth from middle to edges).

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5
Q

Intra-membranous ossification

A

Formation of bone from clusters of mesenchymal stem cells in the centre of bone.

Interstitial growth (growth in middle).

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6
Q

Appositional growth

A

Growth from middle to edges

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7
Q

Interstitial growth

A

Growth in the middle

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8
Q

Epiphyseal plates

A

Boundary between bone and cartilage

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9
Q

Osteoblasts

A

Cells that form new bone tissue. They synthesise and secrete bone matrix - collagen and ground substance

They are involved in bone formation and bone remodelling.

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10
Q

Osteoclasts

A

They break down bone using acid and lysosomes for bone remodelling. They absorb what they remove.

They are bigger, multinucleated and are usually found near a depression of bone.

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11
Q

Osteocytes

A

Former osteoblasts that have been trapped in bone matrix. They sit in lacunae.

When 2 osteocytes meet they form gap junctions.

They are involved in the regulation of bone remodelling and regulate mineral homeostasis.

They can act like osteoclasts and degrade the bone a little - called osteocytic osteolysis.

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12
Q

Lacunae

A

The extra-cellular matrix that surrounds a cell (eg osteocytes, chondrocytes).

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13
Q

Periosteum

A

Membrane outside the bone.

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14
Q

Mesenchymal tissue

A

Undifferentiated connective tissue in the bone marrow. They can differentiate into cells such as osteoblasts.

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15
Q

Osteoid

A

Made of mainly collagen 1 as well as hydroxyapatite. Secreted by osteoblasts.

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16
Q

Hydroxyapatite

A

Part of osteoid laid down by osteoblasts; contains the minerals calcium and phosphate.

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17
Q

Spicules

A

Bony spurs.

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18
Q

Trabeculae

A

Form when spicules join up. Rod-like structures making up bone.

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19
Q

Endostium

A

Where the bone touches the edge of periosteum.

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20
Q

Osteoprogenitor cells

A

Stem cells in bone that are precursors to more specialised cells, osteoblasts and osteoclasts.

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21
Q

Cement line

A

Where osteoid meets existing bone.

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22
Q

How is cancellous bone converted to cortical bone?

A
  1. Mesenchymal stem cells —> osteoblasts that line recently formed trabecuae.
  2. They lay down osteoid that is mineralised.
  3. Osteoblasts become trapped and turn into osteocytes.
  4. This repeats as concentric lamellae are laid down by osteoblasts.
  5. Central MSC convert into blood vessels, lymph vessels and nerves.

This occurs from the inside of bone and grows further inwards.

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23
Q

Lamellae

A

Lamellae laid down at 45 degrees to each other - strengthens.

24
Q

Volkmann’s canals

A

The small channels in bone that transmit blood vessels from the periosteum into the bone and that lie perpendicular to and communicate with the Haversian canals.

25
Q

Arrangement of osteocytes in mature bone

A

Osteocytes are arranged in concentric lamellae of osteons.

26
Q

Structure of mature bone

A

Compact bone:
- Contains Haversian canals (blood, nerves and lymph vessels)
- Concentric lamellae of osteons

Cancellous bone:
- No Haversian or Volkmann’s canals present.
- Teardrop shape due to gravity.

27
Q

Osteon

A

Cylindrical vascular tunnels in bone.

28
Q

Haversian canals

A

Narrow tubes in bone formed by lamellae. They contain blood vessels, lymph vessels and nerves.

They run parallel to the bone.

The canals and surrounding lamellae are called a Haversian system (or an osteon).

29
Q

Volkmann’s canals

A

Any of the small channels in bones that transmit blood vessels from periosteum into bone. They lie perpendicular to and communicate with the Haversian canals.

30
Q

Bone remodelling

A

The process of breaking down and reforming bone.

Two steps:
1. Osteoclasts make a wide tunnel in the bone (cutting cone)
2. Osteoblasts make a smaller tunnel of cortical bone (closing cone)

31
Q

Osteocytic osteolysis
*

A

Osteocytes act like osteoclasts and the degrade the bone a little. This is increased by PTH (parathyroid hormone).

32
Q

Osteogenesis imperfecta

A

Aka brittle bone disease.

Due to mutated collagen fibres that don’t knit together.

Symptoms:
- weakened bones = increased risk of fracture
- short stature
- blue sclera
- hearing loss
- hyper mobility/ flat or arched feet
- poor teeth development

33
Q

Collagen

A

Every third a.a is glycine, as it is the only one small enough to fit within the helical structure.

Faulty collagen production leads to osteogenesis imperfecta.

34
Q

Rickets

A

Vitamin D deficiency that mainly affects children. Leads to poor calcium mobilisation and ineffective mineralisation.

Symptoms:
- weakened bone development
- soft bones
- shortened height and stature
- pain when walking
- characteristic bowed legs

35
Q

Osteomalacia

A

Rickets in adults.

Vitamin D deficiency that leads to lower mineralisation (little to no hydroxyapatite deposits) and increased osteoid.

Increased calcium resorption.

Disease caused by several things; kidney disease, lack of sunlight, some surgeries and certain drugs.

36
Q

Osteoporosis; 3 types

A

Primary - Type 1:
Occurs in post menopausal women due to increase in osteoclasts, which is caused by loss of oestrogen.

Primary - Type 2:
Occurs in older men/women due to loss of osteoblast function, caused by loss of both oestrogen and androgen.
Incomplete filling of osteoclast resorption bays.

Secondary:
Result of drug therapy; processes that affect bone remodelling; or metabolic bone diseases.

37
Q

Achondroplasia

A

Inherited mutation in FGF3 gene.

FGF promotes collagen formation in cartilage => endochondrial ossification affected

Short stature as long bones cannot lengthen normally.

38
Q

Types of bone

A

Long, short, flat, irregular, and sesamoid.

39
Q

Long bones

A

Support weight of body and facilitate movement.

Femur, fibula, tibia, humerus, radius, ulnar etc

40
Q

Short bones

A

Provide stability and some movement.

Wrist and ankle joint bones etc

41
Q

Flat bones

A

Protect internal organs, provide large areas for attachment of muscles.

Skull, thoracic cage, pelvis etc

42
Q

Irregular bones

A

Protect internal organs, vertebrae protect spinal cord, provide anchor points for muscle groups.

Vertebrae, sacrum etc

43
Q

Sesamoid bones

A

Protect tendons from stress and damage from repeated wear and tear.

Small round bones eg patella

44
Q

Bone marrow

A

(Medulla ossea)

Two types - red and yellow

Found inside bones.

45
Q

Red marrow

A

Full of developing RBC; rich blood supply; only found in spongy bone.

Function: haemopoiesis.

46
Q

Yellow marrow

A

Full of adipocytes; poor blood supply (explains yellow colour).

Function: shock absorber and energy source. Can convert to red marrow and therefore carry out haemopoiesis.

47
Q

How do maturing cells leave the bone?

A
48
Q

Sinusoids

A

Irregular tubular space for the passage of blood, taking the place of capillaries and venules in the liver, spleen, and bone marrow.

Incomplete basement membrane, with intercellular gaps between endothelium. Kupffer cells and other macrophages can fit through these gaps to travel.

49
Q

Vasculogenesis

A

Formation of new blood vessels from angioblast precursors in bone marrow
eg embryo development, newly formed cancers, endometriosis

50
Q

Angiogenesis

A

Formation of new blood vessels from existing blood vessels
eg during fetal development, collateral arteries, postnatal lung development

51
Q

Collateral blood vessels

A

These are usually arterioles and provide protection for tissues that may become compromised (not enough O2).

They provide an alternate path for arterial blood flow.

  • Can be generated due to chronic disease eg ischaemia, in coronary arteries (atherosclerosis)
  • Some produced during development eg brain and joints
52
Q

Sprouting angiogenesis

A

FGF produced by mesenchymal cells; pericytes convert into smooth muscle cells.

Slow - takes hours to days

53
Q

Intussusceptive angiogenesis

A

Twinned vessels from primary vessel (splitting one into two).

Needs multiple growth factors.

Quick - takes minutes to hours.

54
Q

Pericyte

A

Immature smooth muscle-like cell.
Key component of capillaries.
Have contractile properties.
Involved in nerve cell communication.

Differentiate into endothelial cells, smooth muscle cells or fibroblasts.

Function: prevent endothelial cell proliferation; maintains tight capillaries eg blood-brain barrier, retina.

55
Q

Calcification

A

Deposition of calcium.

56
Q

Mineralisation

A

Deposition of hydroxyapatite in bone matrix.

57
Q

Bone fracture healing

A

Haematoma formation
Fibrocartilaginous (soft) callus formation
Bony callus formation
Bone remodelling

(endochondral ossification)

Body Logs (6 decks)

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