Histology Of Muscles

Question 1

What is the main function of skeletal muscle?

Answer 1

Locomotion
Joint stability
Heat generation
Posture maintenance and muscle tone

Question 2

What is the function of smooth muscle?

Answer 2

Vasoconstriction and vasodilation
Peristalsis

Question 3

What is the function of cardiac muscle?

Answer 3

Caradiac motion and contractility

Question 4

What are transverse tubules?

Answer 4

Inward folds of the sarcolemma
Well developed in skeletal and cardiac muscle to transport calcium
Absent in smooth muscle

Question 5

What are intercalated disks?

Answer 5

Specialised intracellular junctions only present in cardiac muscle

Question 6

What are the sour different types of skeletal muscle?

Answer 6

Parallel muscle
Convergent muscles
Pennate muscles muscles
Circular muscles

Question 7

What are the different types of parallel muscle?

Answer 7

Parallel muscle e.g bíceps
Parallel with tendinous bands e.g rectus abdominus muscle
Wrapping muscle e.g supinator

Question 8

What are the different types of convergent muscle?

Answer 8

Convergent muscle is the only subgroup
For example the pectoralis major

Question 9

What are the different types of pennate muscles?

Answer 9

Unipennate muscle e.g extensor digitorum muscle
Bipennate muscle e.g rectus femoris muscle
Mutlipennate e.g deltoid muscle
In pennate muscles fibres attach obliquely to the tendon, this provides more force but less flexibility.

Question 10

What are the different types of circular muscle?

Answer 10

Circular muscle is one category
The muscle itself can be contracted or relaxed

Question 11

Give an overview of the different connective tissues in muscle?

Answer 11

Endomysium surrounds muscle fibres contains nerve axons and blood vessels
Perimysium provides Fibrocolloganous support to the muscle fascicles, contains nerves, lymphatics and blood vessels
Epimysium provides fibrocollagenous support to the whole muscle
All layers are continuous with each other and the muscle tendon, are mainly dense irregular connective tissue

Question 12

What does skeletal muscle look like in cross section?

Answer 12

Sarcoplasm is eosinophilic in appearance
Each muscle fibre is hexagonal in shape
Have many peripheral nuclei
Finrocollagenous septa between different muscle fascicles contain blood vessels

Question 13

What does skeletal muscle look like in longitudinal section?

Answer 13

Striations are visible
Flattened and elongated nuclei at the periphery of the fibres

Question 14

What is a striation?

Answer 14

Repeating dark and light bands, from the A and I band in the sarcomere
Along the length of each myofibrils, evident in longitudinal section

Question 15

What is a sarcomere?

Answer 15

The region of a myofibrils between two successive Z discs.
Average 2um long and is the smallest contractile unit of a muscle fibre

Question 16

What is shown in the image?

Answer 16

Electron microscope of longitudinal skeletal muscle
Shows sarcomere se that make up striations
The cytoplasm between each muscle fibre contains mitochondria, SR and glycogen.

Question 17

What do the cross sections of different skeletal muscle bands look like?

Answer 17

Accessory proteins include myomesin

Question 18

Where is acetylcholine esterase found?

Answer 18

In the motor endplate
Found in the junction folds of the muscle, bound to the basement membrane

Question 19

What are y efferent fibres?

Answer 19

Specialised motor axon, terminal axon in the motor endplate can innervated individual muscle spindles fibres
Spindle fibres are intramural muscle cells involved in oroprioceotion.

Question 20

What is myasthenia gravis?

Answer 20

An autoimmune disease mainly affecting voluntary muscles
Antibodies are produced, binds to nicotinic receptirs preventing ACh from causing depolarisation in the muscle
Causes muscle weakness and fatigue, often struggle to life arms and maintain posture.
Eyes are the most notably affected shown by diplopia and ptosis.

Question 21

How is myasthenia gravis often treated?

Answer 21

Administer anticholinesterases inhibitors that inhibit the action of the enzyme acetylcholineesterase This increases the action of acetylcholine by allowing it to compete better with the antibody.

Question 22

What is gowers sign?

Answer 22

Positive gowers sign indicates DMD
Shows how children with DMD get up from a supine position.
Often roll onto belly, then onto elbows and knees, to hands a knees, then uses there hands to walk up their b dog until standing.
Hypertrophy of calf is often seen. As muscle is replaced by fat

Question 23

What does the histological slide for progressed DMD look like?

Answer 23

Death of muscle cell fibres and replaced with fat cells
Muscle fibres are various diameters
Larger connective tissue between muscle fibres

Question 24

What does cardiac muscle look like in histológicas slides?

Answer 24

Striated
Single Central nuclei that are elongated
Branched muscle fibres, less organised than skeletal muscle
Capillaries are often in close proximity identified by the erythrocytes
Intercalated disks can be seen in longitudinal section
Muscles fibres are surround by supporting connective tissue septa which contains the nuclei of fibroblasts and smaller endothelial cells

Question 25

What does smooth muscle look on a histlogical slide?

Answer 25

Central elongated nuclei
No striations
Flat and organised in appearance
Often associated with serosa or adeventitia if in organs
Slender connective tissue strand supply vasculature to the smooth muscle
Second image shows longitudinal and cross sectional image.

Question 26

How does the sarcoplasmic reticulum vary between different muscle types?

Answer 26

Skeletal is highly developed with terminal cisterns
Cardiac is less developed with small cisterns
In smooth it is present but poorly developed

Question 27

What are satellites cells are where are they found.

Answer 27

Found in skeletal muscle aid regenerative function.
Adult myogenic stem cells
Produces myoblasts to regenerate damaged fibres and symmetrical division to replace their own population.