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MSK > MSK Histology > Flashcards

MSK Histology Flashcards

1
Q

Give three characteristics of a muscle cell (or fibre)

A
  • striated
  • unbranched
  • multinucleate
    • nuclei are at periphery of the fibre but like not at the end like the periphery if you’re looking into the muscle fibres at a transverse cross-section
    • the nuclei sit just under the sarcolemma (the cell membrane)
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2
Q

Give the special name for the muscle cell membrane

A

The sarcolemma

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3
Q

Describe the relationship between muscles and fascicles

A

Muscle fibres are grouped into bundles called fascicles

A muscle typically contains several fascicles

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4
Q

Name the three connective tissues seen in a muscle fibre

A
  1. Epimysium
  2. Perimysium
  3. Endomysium
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5
Q

Where are the three connective tissues in muscle fibres found?

A
  1. Epimysium
    • the connective tissue that surrounds the muscle as a whole
  2. Perimysium
    • the connective tissue around a single fascicle
  3. Endomysium
    • the connective tissue around a single muscle fibre

EPE

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6
Q

Define a sarcomere

A

The sarcomere extends from one Z line to the next

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7
Q

Define a motor unit

A

A motor unit consists of one motor neurone and all of the muscle fibres that it innervates

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8
Q

“An organ of fine control will have more muscle fibres per motor unit than an organ of power”

T/F?

A

False

The fewer the number of musle fibres in a motor unit, the finer the control of movement

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9
Q

Name the three types of skeletal muscle fibre

A

Type I

Type IIA

Type IIB

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10
Q

Describe skeletal muscle fibre Type I

A
  • relatively slowly contracting fibres that depend on oxidative metabolism
  • have abundant mitochondria and myoglobin
  • resistant to fatigue
  • produce relatively less force
  • “red” fibres
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11
Q

Describe skeletal muscle fibre Type IIA

A
  • intermediate between Type I and Type IIB
  • relatively fast contracting
  • reasonably resistant to fatigue
  • relatively uncommon
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12
Q

Describe skeletal muscle fibre Type IIB

A
  • fast contracting fibres
  • depend on anaerobic metabolism
  • few mitochondria
  • less myoglobin than Type I fibres
  • fatigue relatively easily
  • produce relatively greater force
  • “white” fibres
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13
Q

Contrast cartilage and bone

A

Cartilage

  • semi-rigid and deformable
  • permeable
  • avascular
  • cells nourished by diffusion through the extracellular matrix

Bone

  • rigid
  • not permeable
  • cells within the bone must be nourished by blood vessels that pervade the tissue
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14
Q

What cells are found in cartilage? What is their name when immature?

A

Cells found in cartilage are called chondrocytes

Chondrocytes are called chondroblasts when immature

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15
Q

Where are chondrocytes found (specifically)?

What is the role of chondrocytes?

A

Chondrocytes live within a space in the extracellular matrix termed a lacuna

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

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16
Q

What are the three types of cartilage found in the body and which is most common?

A
  • Hyaline (most common)
  • Elastic cartilage
  • Fibrocartilage
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17
Q

What is hyaline cartilage made of?

A
  1. 75% water
  2. 25% organic material
    • 60% Type II collagen
    • 40% proteoglycan aggregates
18
Q

Briefly discuss the difference between Type I and Type II collagen

A
  • Type II collagen is finer
  • and instead of aggregating into linear bundles it forms a 3D meshwork

Type I collagen is most form found in most connective tissues e.g. tendon

19
Q

What are proteoglycan aggregates?

A

Proteoglycan aggregates are made up of GAGs (most commonly keratan sulfate and chondroitin sulfate) bound to a core protein and often linked to hyaluronan

20
Q

Describe hyaline cartilage

A
  • grossly, blue & white in colour and translucent
  • most common form of cartilage
21
Q

Describe elastic cartilage

A
  • grossly it is light yellow in colour
  • the addition of elastic fibres make it quite flexible
22
Q

Describe 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 cartilagenous ECM
    • ECM= extracellular matrix
  • grossly, it appears white
23
Q

Where can hyaline cartilage be found?

A
  • articular surfaces
  • tracheal rings
  • costal cartilage
  • epiphyseal growth plates
  • precursor in fetus to many bones
24
Q

What is the function of bone?

A

To provide:

  • Support
  • Levers for effective movement
  • Protection of internal organs (e.g. cranium, ribs)
  • Calcium store
    • >95% of total calcium in the body is found in bone and there is constant exchange of calcium between bone and the blood
  • Haemopoiessis (blood cell production)
    • in utero blood is produced in the liver and spleen
    • BUT well before birth it begins in the bone marrow
    • by birth bone marrow is the site of haemopoiesis
    • by early 20s typically only the axial and limb girdle skeleton is involved in blood production
25
Q

What is the composition of bone?

A
  1. 65% bioapatitie (a form of calcium phosphate, mostly hydroxyapatite)
  2. 23% collagen
  3. 10% water
  4. 2% non-collagen proteins
26
Q

Is cortical bone found at the epiphyses?

A

Nope don’t think so

27
Q

What are the living cells that make bone called?

A

Osteocytes

28
Q

How can you tell this osteon has formed during remodelling and not in original development?

A

The lines that are often visible surrounding the osteon are termed cement lines and are only found in osteons that have formed during remodelling

29
Q

Does trabecular bone have as many Haversian canals as cortical bone?

Why?

A
  • Trabecular bone generally lacks Haversian canals because the struts are think so osteocytes can survive from contact with the marrow spaces
30
Q

Name the cells of the bone

A
  1. Osteoprogenitor cells
  2. Osteoblasts
  3. Osteocytes
  4. Osteoclasts
31
Q

What is the role of osteoprogenitor cells?

A

Osteoprogenitor cells are located on bone surfaces e.g. under the periosteum

Osteoprogenitor cells serve as a pool of reserve osteoblasts

32
Q

What is the role of osteoblasts?

A

Osteoblasts are bone forming cells found on the surface of developing bone

They have plentiful RER and prominent mitochondria

33
Q

What are the role of osteocytes?

A

An osteocyte is a bone cell trapped within the bone matrix

34
Q

What is the role of osteoclasts?

A

Osteoclasts are large multinucleated cells

They are found on the surface of bone and are responsible for bone resorption

35
Q

Describe bone remodelling

A

Bone is constantly undergoing remodelling

  1. a number of osteoclasts will congregate and begin to “srill” into the bone, forming a tunnel
  2. a blood vessel will grow into the tunnel
  3. bringing with it osteoblasts which line the tunnel
  4. osteoblasts begin laying laying down new lamerllar bone
  5. this process continues until only the space of Haversian canal remains
36
Q

What is the basic multicellular unit/BMU?

A

The collection of osteoclasts and osteoblasts that participate in this process at a site is called the BMU

37
Q

What do osteoblasts secrete?

(think about what you know about osteoblasts role and about the makeup of bone)

A

Osteoblasts secrete:

  • collagen,
  • glycosaminoglycans (GAGs),
  • proteoglycans
  • and other organic components of the matrix

which is collectively termed osteoid.

This then becomes mineralised over time in the extracellular space.

38
Q

What is the mineral of bone principally made up of?

A

Calcium phosphate crystals, particularly hydroxyapatite

39
Q

What do we belive the lineage of osteoclasts to be?

A

It is thought that osteoclasts are derived from macrophage lineage of cells

Several of these cells will fuse and form a single giant cell

40
Q

During bone remodelling, where can

a) osteocytes
b) osteoblasts

be found?

A

Osteoblasts are actively secreting matrix that will become bone. Note that because bone is a solid matrix, it can only be added at a surface.

41
Q

What are the important differences between lamellar and woven bone?

A

During development/following a break, the bone laid down differs from normal lamellar bone, because rather than having collagen fibres orientated all in one direction the collagen fibres are laid down in a haphazard fashion

Woven bone is not as strong as lamellar bone and is subsequently remodelled into lamellar bone by being broken down by osteoclasts and reformed by new osteoblasts.

MSK (7 decks)

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