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MSK > Histology > Flashcards

Histology Flashcards

1
Q

describe 3 features of skeletal muscle cells

A

striated
unbranched (long tubes)
Multinucleate (forms a syncytium - several cells loose membranes between them to form one giant cell)

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2
Q

where do nuclei sit in skeletal muscle cells?

A

at the periphery, just under the membrane (sarcolemma)

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3
Q

how big are skeletal muscle?

A

1000 - 200,000 microns

usually entire length of muscle

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4
Q

how are muscle fibres grouped?

A

grouped into fascicles

a muscle contains several fascicles

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5
Q

what are the 3 types of connective tissue in a muscle?

A

each muscle cell surrounded by endomysium
each fascicle surrounded by perimysium
whole muscle body surrounded by epimysium

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6
Q

breakdown of muscle structure?

A

muscle > muscle fascicle > muscle fibre > myofibrils > sarcomeres > actin and myosin

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7
Q

what else is contained within a muscle?

A

blood vessels, nerves, lymphatics

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8
Q

myosin vs actin band?

A 
myosin = A band (thicker/darker)
actin = I band (lighter)
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9
Q

what causes striation in skeletal muscle?

A

optical illusion

regular arrangement of sarcomeres (myosin and actin bands) means dark and light bands line up (z lines in registry)

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10
Q

how can a whole muscle cell (very long) be supplied via one neuromuscular junction?

A

they are able to conduct action potential

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11
Q

how does a motor neuron supply a motor unit?

A

branches near its termination and each branch ends in a neuromuscular junction at a muscle cell

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12
Q

components of type 1 fibres?

A

lots of mitochondria and myoglobin as they are aerobic

“red fibres”

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13
Q

components of type 2x fibres?

A

few mitochondria and less myoglobin as they don’t need as much oxygen bc they are anaerobic
“white fibres”

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14
Q

characteristics of cartilage?

A

semi-rigid and deformable
permeable
avascular (nourished by diffusion through ECM)

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15
Q

characteristics of bone?

A

rigid
not permeable
nourished by blood vessels that pervade the tissue (highly vascular)

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16
Q

what are cartilage cells?

A

chondrocytes

chondroblasts when immature/producing

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17
Q

where are chondrocytes found?

A

lacuna

- maintain extra cellular matrix

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18
Q

what are the components of the extra cellular matrix (ECM)?

A

most common form of cartilage (hyaline)
75% water
25% organic material

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19
Q

what composes the organic material in ECM?

A

60% type 2 collagen

40% proteoglycan aggregates (made up of GAGs)

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20
Q

what are the 3 types of cartilage?

A

hyaline (most common)
elastic (flexibility)
fibrocartilage

21
Q

what is fibrocartilage?

A

mix between type 1 and type 2 cartilage

bands of dense type 1 with small amounts of cartilaginous ECM

22
Q

where is hyaline cartilage found?

A 
articular surfaces
tracheal rings
costal cartilage
epiphyseal growth plates
precursor to bones in foetus
23
Q

give 5 functions of bone?

A 
support
levers for movement
protection of organs
calcium store (95% of calcium)
Haemopoiesis (blood cell production)
24
Q

how does cauliflower ear arise?

A

damage to vasculature in ear due to repeated trauma which is replaced with scar tissue

25
Q

how is bone involved in blood cell production?

A

in utero blood production begins in bone marrow before birth and by time of birth, bone marrow (red) is the site of haemopoiesis
By early twenties - only the axial skeleton and limb girdle is involved in blood production

26
Q

what makes up bone?

A

65% bioapatitie (calcium phosphate)
23% collagen
10% water
2% non-collagen protein

27
Q

cancellous/trabecular bone vs cortical bone?

A 
cancellous = at epiphyses of bone, fine meshwork
cortical = outer dense shell, makes up diaphysis (shaft)
28
Q

how does bone remodel?

A

throughout life at different rates throughout body (except from cochlear area)

29
Q

what makes up bone?

A

round groupings of lamellar bone called osteons
canal in the middle (heversion canal) containing blood vessel
larger spaces between the osteons in trabecular bone

30
Q

what is a volkmans canal?

A

horizontally running canals with blood vessels supplying heversion canals

31
Q

what are osteons?

A

groups of lamellar bodies
usually product of later bone remodelling
forms layers in bone

32
Q

how are cortical and cancellous bone different?

A

similar bone cells

main difference is presence of spaces (marrow cavities)

33
Q

what gives osteons their strength?

A

background of collagen running in different directions

34
Q

what are cannuliculi?

A

little cell processes (like dendrites) that cross the osteon and allow communication with other cells and connection to blood vessels in heversion canal
keeps the cells alive within a solid matrix

35
Q

what is a cement line?

A

marks boundary of osteon

36
Q

are heversion canals found in trabecular bone? why?

A

no
cells are close enough to vessels etc as the struts of bone are thin and close enough to the marrow spaces that they don’t need a separate blood supply

37
Q

name 4 cells of bone

A

osteoprogenitor cells
osteoblasts
osteocytes
osteoclasts

38
Q

which cells lay down new bone?

A

osteoblasts

39
Q

which cells are living within the matrix in bone?

A

osteocytes

40
Q

what are osteoprogenitor cells?

A

serve as a pool of reserve osteoblasts on bone surfaces (e.g under periosteum)

41
Q

what are osteoclasts?

A

large multinucleated cells found on bone surface which reabsorb bone

42
Q

describe the cutting cone remodelling mechanism

A

osteoclasts group together and drill down into bone forming a large tunnel
blood vessel grows into the tunnel, bringing with it osteoblasts which line the tunnel and lay down new lamellar bone
heversion canal is formed

43
Q

how do osteoblasts form new bone?

A

they secrete Osteoid (collection of organic compounds of bone matrix - collagen, GAGs, proteoglycans etc)
Osteoid is mineralized over time in extracellular space

44
Q

what is the main component of bone mineral?

A

calcium phosphate

45
Q

where is bone built from?

A

can only grow at the surface

bone is added to at the surface

46
Q

what is woven bone?

A

initial layed down bone either during development or fracture healing
chaotic organisation of collagen fibres - no lamellar structure
later destroyed by osteoclasts and replaced by lamellar bone

47
Q

type 1 vs type 2 collagen?

A

type 1 = most common, found in most connective tissues (e.g - tendon)
type 2 = finer, forms a 3D meshwork instead of aggregating into linear bundles like type 1

48
Q

where are osteoclasts derived from?

A

macrophage lineage

can fuse to form a giant cell

MSK (66 decks)

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