Histology - MSK

Question 1

What are the different types of muscle? Where can you find each of them?

Answer 1

• Visceral (smooth) muscle = arterial wall, wall of intestines, airways of lungs
• Voluntary (skeletal) muscle = skeletal muscles, larynx, diaphragm
• Cardiac muscle = heart, base of great vessels
• Other contractile cells = pericytes, myo-fibroblasts, myo-epithelial cells

Question 2

How are skeletal muscle cells formed?

Answer 2

Formed by the fusion of primitive cells in the developing embryo called myoblasts

Question 3

What do myoblasts fuse to form? What do sarcomeres form? What are cytoplasms filled with? What do groups of muscle fibres form? What are fascicles of muscle fibres held together to form?

Answer 3

• Multi-celled syncytium
• Sarcomeres joined end to end to form myofibrils (multiple myofibrils within each skeletal muscle cell)
• Cytoplasm filled with myofibrils to form muscle fibre
• Muscle fibres clumped together to form fascicles
• Fascicles held together to form muscles

Question 4

What are the connective tissues of skeletal muscle?

Answer 4

• Endomycium
• Perimycium
• Epimycium

Question 5

Diagram of individual myoblasts forming an individual muscle fibre.

Answer 5

Individual muscle fibres are multi-nucleated

Question 6

What does a skeletal muscle fibre/cell contain in its cell membrane?

Answer 6

• Cell membrane (sarcolemma)
• Nuclei
• Contractile proteins
• Mitochondria
• Endoplasmic reticulum (sarcoplasmic reticulum)
• Glycogen-rich cytoplasm (glycogen-rich sarcoplasm)

Question 7

Is skeletal muscle voluntary or involuntary? Is it striated? Does it have a single nucleus? Is it branching?

Answer 7

• Voluntary
• Elongated fibres with a striated cytoplasm
• Multinucleate
• Nuclei at edges
• Non-branching

Question 8

Diagram of striations under different stains.

Answer 8

Question 9

Why is skeletal muscle striated?

Answer 9

Myofibrils are in register

Question 10

What are the two types of skeletal muscle fibres? Are they distinguishable on H+E stain?

Answer 10

• Type 1 = rich in fibrillar ATPase, slow twitch
• Type 2 = rich in fibrillar ATPase, fast twitch

Question 11

How do muscles detect stretch and tension? What are these contained within?

Answer 11

• Muscle spindles
• Contained within a fibrocollagenous capsule
• Intrafusal muscle fibres (wrapped around by gamma efferent nerves)
• Detect stretch and tension

Question 12

Diagram of skeletal muscle connective tissue.

Answer 12

Question 13

How is skeletal muscle connected to bone?

Answer 13

• Sharpey’s fibres
• Bundles of collagen linking epimysium to periosteum
• Attach muscle to bone over a wide area, e.g. rotator cuff muscles attached to scapula

Question 14

How is skeletal muscle connected to bone over a short area?

Answer 14

• Tendons
• Connect muscle to bone
• Parallel bundles of collagen with intervening fibroblasts
• Attach muscle to bone over a small area, e.g. rotator cuff muscles attached to humerus

Question 15

Answer 15

E

Question 16

Answer 16

A

Question 17

Answer 17

B

Question 18

Answer 18

B

Question 19

Answer 19

A

Question 20

Answer 20

C

Question 21

Answer 21

D

Question 22

Answer 22

A

Question 23

Answer 23

D

Question 24

Answer 24

A

Question 25

Answer 25

E

Question 26

Answer 26

B

Question 27

What are the cells of bone? What makes up the extracellular matrix of bone?

Answer 27

- Cells: - osteoprogenitor cells - osteoblasts - osteocytes - osteoclasts - Extracellular matrix: - collagen - calcium hydroxyapatite

Question 28

Where are osteoblasts and osteocytes derived from? What do osteoblasts secrete? What are osteocytes? How are osteoblasts connected to their neighbours?

Answer 28

- Derived from osteoprogenitor cells - Osteoblasts secrete osteoid - Osteocytes = osteoblasts that have become trapped in their own matrix - Connect to surrounding cells via canaliculi

Question 29

What are osteoclasts? What are they derived from? What is their function? What is the activity of osteoclasts and osteoblasts coordinated by?

Answer 29

- Multinucleate cells - Derived from monocytes - Absorb bone - sit in Howship's lacunae - RANK-L

Question 30

How can describe the different types of bone?

Answer 30

- By origin: - Primary (woven) - Secondary (lamellar) - By mode of formation: - Membranous - Endochondrial - By gross appearance: - Spongy/cancellous - Compact - Osteons - Appositional

Question 31

Diagram of osteoid and primary bone.

Answer 31

Question 32

What does secondary bone form as? What do osteons contain?

Answer 32

- Secondary bone is stronger than primary bone - Forms as osteons - Osteons have a central Haversian canal donating blood vessels - Osteons have a surrounding concentric rings of lamellar bone with osteocytes

Question 33

What is secondary bone typically examined as?

Answer 33

Typically examined as a decalcified section

Question 34

What are the two types of bone formation?

Answer 34

- Intramembranous = flat bones of the skull and some cortical bone shafts - Endochondrial = all other bones

Question 35

Picture of intramembranous ossification.

Answer 35

Question 36

Picture of endochondrial ossification.

Answer 36

Question 37

What does synovium line? What are the the two types of synovial cells? What is the shape of synovial cells? Is synovium vascular and innervated?

Answer 37

- Lines the inside of the joint capsule, 1-4 layers of synovial cells - Type A = phagocytes, type B = rich in RER - Variable shapes - squamous to cuboidal - Synovium is richly vascular and highly innervated

Question 38

Answer 38

E

Question 39

Answer 39

D

Question 40

Answer 40

B

Question 41

Answer 41

E

Question 42

Question 43

Answer 43

A

Question 44

Answer 44

D