Histology

Question 1

describe 3 features of skeletal muscle cells

Answer 1

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

Question 2

where do nuclei sit in skeletal muscle cells?

Answer 2

at the periphery, just under the membrane (sarcolemma)

Question 3

how big are skeletal muscle?

Answer 3

1000 - 200,000 microns

usually entire length of muscle

Question 4

how are muscle fibres grouped?

Answer 4

grouped into fascicles

a muscle contains several fascicles

Question 5

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

Answer 5

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

Question 6

breakdown of muscle structure?

Answer 6

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

Question 7

what else is contained within a muscle?

Answer 7

blood vessels, nerves, lymphatics

Question 8

myosin vs actin band?

Answer 8

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

Question 9

what causes striation in skeletal muscle?

Answer 9

optical illusion

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

Question 10

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

Answer 10

they are able to conduct action potential

Question 11

how does a motor neuron supply a motor unit?

Answer 11

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

Question 12

components of type 1 fibres?

Answer 12

lots of mitochondria and myoglobin as they are aerobic

“red fibres”

Question 13

components of type 2x fibres?

Answer 13

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

Question 14

characteristics of cartilage?

Answer 14

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

Question 15

characteristics of bone?

Answer 15

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

Question 16

what are cartilage cells?

Answer 16

chondrocytes

chondroblasts when immature/producing

Question 17

where are chondrocytes found?

Answer 17

lacuna

- maintain extra cellular matrix

Question 18

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

Answer 18

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

Question 19

what composes the organic material in ECM?

Answer 19

60% type 2 collagen

40% proteoglycan aggregates (made up of GAGs)

Question 20

what are the 3 types of cartilage?

Answer 20

hyaline (most common)
elastic (flexibility)
fibrocartilage

Question 21

what is fibrocartilage?

Answer 21

mix between type 1 and type 2 cartilage

bands of dense type 1 with small amounts of cartilaginous ECM

Question 22

where is hyaline cartilage found?

Answer 22

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

Question 23

give 5 functions of bone?

Answer 23

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

Question 24

how does cauliflower ear arise?

Answer 24

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

Question 25

how is bone involved in blood cell production?

Answer 25

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

Question 26

what makes up bone?

Answer 26

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

Question 27

cancellous/trabecular bone vs cortical bone?

Answer 27

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

Question 28

how does bone remodel?

Answer 28

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

Question 29

what makes up bone?

Answer 29

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

Question 30

what is a volkmans canal?

Answer 30

horizontally running canals with blood vessels supplying heversion canals

Question 31

what are osteons?

Answer 31

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

Question 32

how are cortical and cancellous bone different?

Answer 32

similar bone cells | main difference is presence of spaces (marrow cavities)

Question 33

what gives osteons their strength?

Answer 33

background of collagen running in different directions

Question 34

what are cannuliculi?

Answer 34

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

Question 35

what is a cement line?

Answer 35

marks boundary of osteon

Question 36

are heversion canals found in trabecular bone? why?

Answer 36

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

Question 37

name 4 cells of bone

Answer 37

osteoprogenitor cells osteoblasts osteocytes osteoclasts

Question 38

which cells lay down new bone?

Answer 38

osteoblasts

Question 39

which cells are living within the matrix in bone?

Answer 39

osteocytes

Question 40

what are osteoprogenitor cells?

Answer 40

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

Question 41

what are osteoclasts?

Answer 41

large multinucleated cells found on bone surface which reabsorb bone

Question 42

describe the cutting cone remodelling mechanism

Answer 42

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

Question 43

how do osteoblasts form new bone?

Answer 43

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

Question 44

what is the main component of bone mineral?

Answer 44

calcium phosphate

Question 45

where is bone built from?

Answer 45

can only grow at the surface | bone is added to at the surface

Question 46

what is woven bone?

Answer 46

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

Question 47

type 1 vs type 2 collagen?

Answer 47

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

Question 48

where are osteoclasts derived from?

Answer 48

macrophage lineage | can fuse to form a giant cell