Histology

Question 1

what is a eukaryotic cell?

Answer 1

a cell with a true nucleus

Question 2

what are the 3 principal types of muscle?

Answer 2

• skeletal (voluntary)
• cardiac
• smooth

Question 3

what do skeletal muscle cells look like?

Answer 3

• striated
• unbranched
• multi-nucleated

Question 4

where are nuclei found in a muscle fibre & why?

Answer 4

at the periphery of the fibres just under the cep membrane because cells are so stuffed with contractile fibres, the nuclei are pushed to the side

Question 5

what’s the cell membrane called in a muscle fibre?

Answer 5

sarcolemma

Question 6

what groups are muscle fibres put into?

Answer 6

fascicles

Question 7

what is the connective tissue that surrounds the muscle as a whole called?

Answer 7

epimysium

Question 8

what is the connective tissue around a single fascicle called?

Answer 8

perimysium

Question 9

what is the connective tissue around a single muscle fibre called?

Answer 9

endomysium

Question 10

what are sarcomeres?

Answer 10

the unit of contraction of the muscle cell i.e. the smallest contractile elements in the striated muscle cell

Question 11

how are sarcomeres normally placed in a typical muscle cell?

Answer 11

end-to-end to form a myofibril

Question 12

how are the myofibrils packed into a muscle fibre?

Answer 12

dozens to hundred are packed in like cigarettes in a pack

Question 13

which is the thick protein filament?

Answer 13

myosin

Question 14

which is the thin protein filament?

Answer 14

actin

Question 15

what does a Z disk do?

Answer 15

anchors actin filaments from adjacent sarcomeres to bind two sarcomeres together

Question 16

what is the A band?

Answer 16

the length of a myosin filament, darker

Question 17

what is the I line?

Answer 17

actin by itself, contraction causes it to get smaller due to sliding action of actin & myosin

Question 18

why is skeletal muscle striated?

Answer 18

each sarcomere of a myofibril is held in close registry to the next one so the A, I & Z lines line up & look like stripes across the myofibrils

Question 19

what does a motor unit consist of?

Answer 19

one motor neurone & all of the muscle fibres it innervates

Question 20

what does fewer muscle fibres in a motor unit mean?

Answer 20

finer control of movement

Question 21

what is the neuromuscular junction?

Answer 21

a special type of synapse where the axon of the motor neurone branches as it nears its termination

Question 22

how are the fibres of a motor unit organised in the muscle?

Answer 22

scatters but all of the same fibre type

Question 23

where is the finest control found in the body?

Answer 23

in the oculomotor nuerones

Question 24

how many times does each muscle fibre meet the motor neurone controlling it?

Answer 24

once

Question 25

what is type 1 skeletal muscle fibre?

Answer 25

relatively slowly contracting fibres that depend on oxidative metabolism. Have abundant mitochondria & are resistant to fatigue and produce relatively less force

Question 26

what are type 1 muscle fibres also often called & why?

Answer 26

"red" fibres due to lots of myoglobin in the cells

Question 27

give an example of where type 1 muscle fibres may be found in the body

Answer 27

the back

Question 28

what are type 2a skeletal muscle fibres?

Answer 28

intermediated between types 1 & 2. Relatively fast contracting but also reasonably resistant to fatigue.

Question 29

how common are type 2a skeletal muscle fibres?

Answer 29

relatively uncommon

Question 30

what are type 2b skeletal muscle fibres?

Answer 30

fast contracting fibres that depend on aerobic metabolism. Have few mitochondria so fatigue relatively easily & produce greater force.

Question 31

what are type 2b skeletal muscle fibres sometimes called?

Answer 31

"white" fibres

Question 32

where may you find type 2b skeletal muscle fibres in the body?

Answer 32

the fingers

Question 33

what is cartilage?

Answer 33

Semi-rigid and Deformable Permeable Avascular (no blood vessels)

Question 34

how are cartilage cells nourished?

Answer 34

by diffusion through the extracellular matrix (outer perichondrium)

Question 35

what is bone?

Answer 35

rigid | not permeable

Question 36

how are cells in bone nourished?

Answer 36

must be nourished by blood vessels that pervade the tissue

Question 37

what are the cells found in cartilage called?

Answer 37

chondrocytes (chondroblasts when immature)

Question 38

where are chondrocytes found?

Answer 38

live within a space in the extracellular matrix termed a lacuna

Question 39

what are chondrocytes & what do they do?

Answer 39

active cells which not only secrete, but also maintain the extracellular matrix around them

Question 40

what is the most common form of cartilage?

Answer 40

hyaline

Question 41

what is the composition of the extracellular matrix of hyaline cartilage?

Answer 41

- 75% water | - 25% organic material

Question 42

what is the organic material found in the ECM of hyaline cartilage made up of?

Answer 42

- 60% type 2 collagen | - 40% proteoglycan aggregates

Question 43

what is type 2 collagen?

Answer 43

finer than type 1 collagen & forms a 3-D meshowrok

Question 44

what is type 1 collagen?

Answer 44

common form found in most connective tissues (e.g. tendon) which aggregates into linear bundles

Question 45

what are proteoglycans made up of?

Answer 45

GAGs bound to a core protein & often linked to hyaluronan

Question 46

what are GAGs?

Answer 46

most commonly keratin sulfate & chondroitin sulfate

Question 47

what does hyaline cartilage look like?

Answer 47

blue-white colour & transluscent

Question 48

what does elastic cartilage?

Answer 48

light yellow in colour

Question 49

what gives elastic cartilage it's flexibility?

Answer 49

the addition of elastic fibres

Question 50

what is fibrocartilage?

Answer 50

hybrid between tendon & hyaline cartilage

Question 51

what is fibrocartilage made up of?

Answer 51

bands of densely packed type 1 collagen interleaved with rows of chondrocytes surrounded by small amounts of cartilaginous ECM

Question 52

what does fibrocartilage look like?

Answer 52

white

Question 53

what are the functions of bone?

Answer 53

- support - levers for movement - protection - Ca++ storage - Haemopoiesis

Question 54

what is haemopoiesis?

Answer 54

blood cell production

Question 55

what are the two types of bone identifiable with the naked eye in a long bone?

Answer 55

cortical & cancellous/trabecular bone

Question 56

what is cortical bone?

Answer 56

an outer dense shell which makes up the shaft of a long bone

Question 57

where is cancellous bone found?

Answer 57

occupies the ends of the bone (epiphyses)

Question 58

what does cancellous bone look like?

Answer 58

fine meshwork of bone

Question 59

what is a aversion canal?

Answer 59

canal running along long axis of the bone for blood vessels surround by layer upon layer of bone

Question 60

what are the outer layers of the bone called?

Answer 60

outer circumferential lamellae

Question 61

what do the layers of bone represent?

Answer 61

changes in the collagen that's laid down and the way it's orientated (laid down similarly to plywood)

Question 62

what are the living cells found in bone?

Answer 62

osteocytes

Question 63

what are volkman's canals?

Answer 63

run horizontally to deliver blood between the aversion canals

Question 64

how do osteocytes get nutrients & O2?

Answer 64

through their dendrites which run in canaliculi & can get O2 & nutrients by being in contact with a blood vessel or another osteocyte's dendrites

Question 65

what are the lines that are often visible surrounding an osteon called?

Answer 65

cement lines

Question 66

what is an osteon?

Answer 66

the tree ring ling structures with the aversion canals running in them

Question 67

what are osteoprogenitor cells & where are they found?

Answer 67

located on bone surfaces, for example under the periosteum, these cells serve as a pool of reserve osteoblasts (precursors of osteoblasts)

Question 68

what are osteoblasts & where are they found?

Answer 68

bone forming cells found the surface of developing bone. Have plentiful RER & prominent mitochondria

Question 69

what are osteocytes & where are they found?

Answer 69

a bone cell trapped within the bone matrix

Question 70

what are osteoclasts & where are they found?

Answer 70

large multinucleate cells found on the surface of bone, responsible for bone resorption

Question 71

how is a bone remodelled?

Answer 71

a number of osteoclasts will congregate & will begin to drill into the bone forming a tunnel where a blood vessel will grow into, bringing with it osteoblasts. Osteoblasts line the tunnel & begin laying down new lamellar bone.

Question 72

what is the collection of osteoclasts & osteoblasts that participate in bone remodelling called?

Answer 72

basic multicellular unit (BMU)

Question 73

what are osteoclasts believed to be derived from?

Answer 73

the macrophage lineage of cells. Several of these cells will fuse and form a single giant cell.

Question 74

what do osteoclasts secrete to eat away at bone?

Answer 74

acids & enzymes

Question 75

what do osteoblasts secrete?

Answer 75

a type of organic material, an osteoid, which will attract collagen & minerals to it so it will mineralise & harden over time

Question 76

what can younger osteons do to older osteons?

Answer 76

partially obliterate them when they're forming

Question 77

what bone is found in growing children or following a break?

Answer 77

woven bone which will then be remodelled into lamellar bone

Question 78

what is the advantage of woven bone?

Answer 78

can be made quickly

Question 79

what is the disadvantage of woven bone?

Answer 79

not as strong as lamellar bone

Question 80

how are the collagen fibres arranged in woven bone compared to lamellar bone?

Answer 80

woven - haphazard nests | lamellar - carefully designed layers