MMB (014) Muscle Histology

Question 1

Answer 1

Question 2

…..is the dense outer coat of collagenous Connective tissue in muscles

Answer 2

Epimysium dense outer coat of collagenous Connective tissue

Question 3

…..is the CT trabeculae that divide the muscle into fascicles

Answer 3

Perimysium

Question 4

……is the delicate loose CT extending between muscle fibers.

Answer 4

Endomysium

Question 5

Answer 5

Question 6

define the type of muscle fibers and explain the diiferences between the two types

Answer 6

-Green arrows point to Type I muscle fibers : Rich in myoglobin (red) and Aerobic

-Black arrows point to Type II muscle fibers : Rich in glycogen Less myoglobin ,, Anaerobic

Question 7

Type(I/II) is Related to continuous, weak contractions

While

Type(I/II) is related to intense sporadic contractions

Answer 7

I

II

Question 8

Postural muscles are rich in type… fibers

Answer 8

Type I

Question 9

Biceps, triceps and extraocular muscles are rich in Type …. fibers

Answer 9

Type II

Question 10

….. is An autoimmune disease that is usually associated with autoantibodies directed against acetylcholine “nicotinic” receptors.

Answer 10

Myasthenia gravis

Question 11

Clinical manifestations of Myasthenia gravis ?

Answer 11

-Ptosis (drooping eyelids)

-Diplopia (double vision)

Question 12

characteristic features of Myasthenia gravis ?

Answer 12

-Weakness of extraocular muscles

-Dramatic response to cholinesterase inhibitors

Question 13

Answer 13

Question 14

Answer 14

Question 15

Answer 15

.

Question 16

Answer 16

Question 17

Answer 17

Question 18

Answer 18

Question 19

Mention two types of Muscle dystrophy

Answer 19

Duchenne muscle dystrophy :
- Complete absence of dystrophin

Becker muscle dystrophy :
-Abnormal dystrophin

Question 20

Mutation in dystrophin gene located on chromosome…..

Answer 20

chromosome X

Question 21

Function of dystrophin ?

Answer 21

Connects the cytoskeleton of muscle fiber to the basal lamina&raquo_space; Mechanical stability to muscle fibers during contraction

Question 22

defects in the Dystrophin-glycoprotein complex leads to :

Answer 22

make muscle cells vulnerable to transient membrane tear during contraction&raquo_space; calcium influx&raquo_space; may disrupt intracellular signaling.

Question 23

End result of dystrophin defects ?

Answer 23

myofiber degeneration&raquo_space; exceeds capacity for repair.

Question 24

Microscopic features of Duchenne muscle dystrophy ?

Answer 24

-Segmental myofiber degeneration and regeneration with areas of atrophic myofibers

• Muscle tissue is replaced by collagen and fat cells.

-The rest of muscle tissue shows marked variation in size, from small atrophic fibers to large hypertrophied fibers.

Question 25

Immuno-histochemical examination of dystrophin shows: (in ill patients)

Answer 25

absence of the normal sarcolemmal staining in Duchenne & reduced staining in Becker muscular dystrophy.

Question 26

Answer 26

Question 27

Answer 27

Question 28

Pathogenesis of Becker muscular dystrophy (BMD) ?

Answer 28

—Abnormal but functional dystrophin may be produced, in contrast to the pathology in DMD, in which there is failure to produce dystrophin

— Dystrophin levels in BMD are generally 30-80% of normal

Question 29

This is the Clinical presentation of ?

Answer 29

Duchenne muscle dystrophy

Question 30

What exactly are Satellite cells ?

Answer 30

muscle resident myogenic stem cells

Question 31

Where are Satellite cells located in muscles ?

Answer 31

reside in a niche on the surface of the muscle fiber, beneath the basal lamina