Session 16: Tissue movement - muscular tissue

Question 1

Describe the histological construction of the skeletal muscle from the smallest to the largest unit.

Answer 1

• Actin and myosin filaments create myofibrils
• The myofibrils are surrounded by sarcoplasmic
  reticulum and T-tubules
• This creates a muscle fiber
• The muscle fiber is surrounded by the sarcolemma,
  external lamina and endomysium
• The different muscle cells create a group known as a
  fascicle
• The fascicle is surrounded by perimysium
• The fascicles create the muscle
• The muscle is surrounded by epimysium
• The CT components are there for force conduction

Question 2

Name and describe the different cross-striations on skeletal muscles.

Answer 2

A-band:

• Full length of myosin filaments
• stays the same length during contraction

I-band:

• Part of actin filaments not overlapping myosin filaments
• shortens during contraction

H-band:
- Part of myosin filaments not overlapping actin filaments

M-line:

• Connections between myosin filaments
• Middle of H-band

Z-line:

• Connections between actin filaments
• Middle of I-band

Question 3

Name the two structures involved in the calcium conducting system of the skeletal muscle.

Answer 3

T-tubules

Sarcoplasmic reticulum

Question 4

Describe the T-tubules of the skeletal muscle cells.

Answer 4

• Invaginations of sarcolemma
• On A-I band junctions
• Surround myofibrils

Question 5

Describe the sarcoplasmic reticulum of the skeletal muscle cells.

Answer 5

• Repeating tubular networks of the surrounding
  myofibrils
• From A-I band junction to A-I band junction
• One network surrounding A- band
• One network surrounding I- band
• Terminal cisternae on A-I band junctions

Question 6

Discuss the regeneration of skeletal muscle.

Answer 6

• Limited
• Nuclei in syncytium are incapable of undergoing
  mitosis

IF EXTERNAL LAMINA IS DISRUPTED:
- Tissue recover w/ scar formation by fibroblasts

IF EXTERNAL LAMINA IS INTACT:

• Satellite cells in basal lamina are activated after injury
• They proliferate and differentiate into myoblasts
• Myoblasts fuse and form myotube
• Myotube mature to muscle fiber

Question 7

Describe the histological construction of the cardiac muscle from the smallest unit to the largest unit.

Answer 7

• Actin and myosin filaments create myofibrils
• Myofibrils are surrounded by sarcoplasmic reticulum
  and T-tubules
• This creates a muscle fiber which is surrounded by
  endomysium
• The muscle fiber forms a muscle
• Subendocardial and sub-epicardial CT surround the
  muscle

Question 8

Describe the T-tubules of the cardiac muscles.

Answer 8

• Invagination of sarcolemma
• On Z-line
• Surround myofibrils
• Diameter is larger than in skeletal muscle

Question 9

Describe the sarcoplasmic reticulum of the cardiac muscle.

Answer 9

• Not as well developed as in the skeletal muscle
• Repeating tubular networks surrounding myofibrils
  incompletely
• From Z-line to Z-line
• One network surrounding entire sarcomere
• Small terminal cisternae on Z-line

Question 10

Describe the regeneration of cardiac muscle.

Answer 10

• Mitosis possible during first year and limited ability
  later on
• Repair dead cells by scar formation

Question 11

Describe the histological construction of smooth muscle from the smallest unit to the biggest unit.

Answer 11

• Actin and myosin filaments form a single muscle cell
• Muscle cells form bundles
• CT surround cells and bundles
• Bundles form muscle

Question 12

Describe the calcium conducting system of the smooth muscle.

Answer 12

• No T-tubules
• Caveolae
• Sarcoplasmic reticulum

Question 13

Describe the regeneration of smooth muscle.

Answer 13

• Divide mitotically
• Continuous growthy and replacement of muscle cells
• Differentiate from mesenchymal cells, endothelial
  cells and pericytes