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Musculoskeletal > Bone Structure and Core MSK Histology > Flashcards

Bone Structure and Core MSK Histology Flashcards

1
Q

How does skeletal muscle appear?

A

Cells are striated, unbranched and multinucleate (forms a syncytium)

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2
Q

What shape are skeletal muscle fibres and how are they grouped?

A

Fibres are long cylinders 10-100 micrometers in diameter and 1000-200000 micrometers in length; grouped into bundles called fascicles (each muscle contains several fascicles)

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3
Q

Where are the nuclei of skeletal muscle cells located?

A

At the periphery of the fibre, just under the cell membrane (called the sarcolemma in muscle cells)

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4
Q

What is the epimysium?

A

Connective tissue that surrounds the muscle as a whole

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5
Q

What is the perimysium?

A

Connective tissue that surrounds a single fasicle

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6
Q

What is the endomysium?

A

Connective tissue that surrounds a single muscle fibre

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7
Q

How is muscle organised?

A

Each muscle fibre contains many myofibrils, with each myofibril consisting of many sarcomeres placed end to end

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8
Q

What are sarcomeres?

A

Unit of contraction of muscle cell, smallest contractile elements in the straited muscle cell

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9
Q

Where do sarcomeres extend to?

A

From one Z-line to the next

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10
Q

Why do striated fibres have a regular pattern of bands running across the fibres?

A

Sarcomeres in the myofibrils have alternating light and dark bands, and are held in registry with one another across the fibre

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11
Q

How are striations organised in a fibre?

A

They run across the fibre at right angles to the long axis

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12
Q

How do sarcomeres align with each other in a fibre?

A

The Z-disks in the sarcomere in one myofibril will be aligned with the Z-disks of the sarcomeres in the surrounding myofibrils

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13
Q

What does the motor unit of a skeletal muscle consist of?

A

One motor neuron and all of the muscle fibres that it innervates

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14
Q

What does having fewer muscle fibres attached to a motor neuron allow?

A

Finer control of movement

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15
Q

What is the neuromuscular junction?

A

Special type of synapse at the end of each branch of the motor neuron axon

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16
Q

How are the fibres of each motor unit organised in the skeletal muscle?

A

Scattered throughout the muscle and are all the same fibre type

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17
Q

What is type I skeletal muscle?

A

Relatively slow contracting fibres that depend on oxidative metabolism, abundant mitochondria and myoglobin, resistant to fatigue, produce less force, often called “red fibres”

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18
Q

What is type IIa skeletal muscle?

A

Relatively fast contracting but also reasonably resistant to fatigue, relatively uncommon

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19
Q

What is type IIb skeletal muscle?

A

Fast contracting fibres that depend on anaerobic metabolism, few mitochondria and less myoglobin, fatigue relatively easily, produce relatively greater force, often called “white fibres”

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20
Q

What are some features of cartilage?

A

Semi-rigid, deformable, permeable, avascular, cells nourished by diffusion through the extracellular matrix

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21
Q

What are some features of bone?

A

Rigid, not permeable, cells within the bone must be nourished by blood vessels that pervade the tissue

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22
Q

What are chondrocytes?

A

Cells found in cartilage (chondroblasts when immature), active cells that both secrete and maintain the extracellular matrix around them

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23
Q

Where are chondrocytes located in cartilage?

A

Live within a space in the extracellular matrix termed the lucuna

24
Q

What is the confirmation of the extracellular matrix in hyaline cartilage?

A

75% water, 25% organic material

25
Q

What is the organic material that makes up the extracellular matrix?

A

60% type II collagen = finer (15-45 micrometers), forms 3D network
40% proteoglycan aggregates = made up of GAGs (most commonly keratin sulphate and chondroitin suphate) bound to a core protein and often linked to hyaluronan

26
Q

What are the types of cartilage?

A

Hyaline, elastic, fibrocartilage

27
Q

What are some features of hyaline cartilage?

A

Most common form, found at articular surfaces, tracheal rings, costal cartilage, epiphyseal growth plates and in fetus as precursor to many bones, blue-white and translucent

28
Q

What are some features of elastic cartilage?

A

Light yellow, addition of elastic fibres make it quite flexible

29
Q

What are some features of fibrocartilage?

A

Hybrid between tendon and hyaline cartilage, bands of densely packed type I collagen interleaved with rows of chondrocytes surrounded by small amounts of cartilaginous ECM, appears white

30
Q

What are some function of bone?

A

Support and lever for movement, protects internal organs, calcium store, haemopoiesis

31
Q

How does bone act as a calcium store?

A

More than 95% of the total calcium in the body is stored in the bones and there is constant exchange of calcium between bone and the blood

32
Q

Where does haemopoiesis begin, and where are the main sites in adults?

A

Begins in bone marrow before birth; by early twenties typically only the axial and limb girdle skeleton is involved in blood production

33
Q

What is the composition of bone?

A

23% collagen, 65% bioapatite (form of calcium phosphate, mostly hydroxyapatite), 10% water, 2% non-collagen proteins

34
Q

What kind of bone makes up the outer shell (diaphysis)?

A

Dense cortical bone

35
Q

What kind of bone makes up the ends of the bones (epiphyses)?

A

Cancellous/trabecular bone (fine meshwork)

36
Q

When does bone undergo remodelling?

A

Throughout life

37
Q

What are some similarities between compact and trabecular bone?

A

Similar bone cells and matrix, both lamellar (made of layers)

38
Q

Where are the marrow cavities in relation to trabecular bone?

A

Adjacent to the bone

39
Q

How do blood vessels and nerves penetrate the bone?

A

Through small canals

40
Q

What are the living cells found in bone called?

A

Osteocytes

41
Q

What are cement lines?

A

Visible lines around osteons that have formed during remodelling

42
Q

Does trabecular bone have Haversian canals?

A

No = struts are thin so osteocytes survive from contact with marrow spaces

43
Q

What are the different types of bone cells?

A

Osteoprogenitor cells, osteoblasts, osteocytes, osteoclasts

44
Q

What are osteoprogenitor cells?

A

Serve as pool of reserve osteocytes, found on bone surfaces

45
Q

What are osteoblasts?

A

Bone forming cells found on the surface of developing bone, have plentiful RER and prominent mitochondria

46
Q

Where are osteocytes located?

A

Trapped within the bone matrix

47
Q

What are osteoclasts?

A

Large (>40 micrometers) multinucleated cells, found on bone surface and are responsible for bone resorption, several cells fuse to form single giant cell, thought to be derived from macrophage lineage

48
Q

How does bone remodelling begin?

A

Number of osteoclasts will congregate and begin to “drill” into the bone forming a tunnel

49
Q

How are blood vessels involved in bone remodelling?

A

Blood vessels grow into the tunnel created by osteoclasts, bringing with them osteoblasts which then line the tunnel and begin laying down new lamellar bone

50
Q

When does bone remodelling stop?

A

Until only the space of a Haversian canal remains

51
Q

What is osteoid?

A

The collagen, glycosaminoglycans (GAGs), proteoglycans and other organic compounds secreted by osteoblasts

52
Q

What happens to osteoid over time?

A

It becomes mineralised in the extracellular space

53
Q

What is the main mineral of bone?

A

Calcium phosphate crystals, particularly hydroxyapatite (Ca10(PO4)6(OH)2)

54
Q

How does woven bone differ from normal lamellar bone?

A

Collagen fibres are orientated haphazardly, isn’t as strong as lamellar bone, and is subsequently remodelled into lamellar bone by being broken down by osteoclasts and reformed by new osteoclasts

55
Q

When is woven bone laid down?

A

During development of after a bone is broken

Musculoskeletal (57 decks)

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