Lab5 - Muscle

Question 1

What are the 3 types of muscle?

Answer 1

• Skeletal
• Cardiac
• Smooth

Question 2

What are myoblasts?

Answer 2

Myoblasts have a single nucleus, they fuse to form a muscle cell/muscle fiber

Question 3

What are the characteristics of muscle fibers?

Answer 3

Muscle fibers = muscle cells
- Multinucleated
- Peripherally located nuclei
- Composed of multiple myofibrils (~1500)
- Surrounded by CT called endomysium
- Striated (striations on the myofibrils)
- Multiple mitochondrias

Question 4

What is the smallest functional unit of muscle?

Answer 4

Sarcomere → delimited by 2 adjacent Z-lines
- Composed of myosin (thick) filaments + actin (thin) filaments

Question 5

What is the sarcolemma?
What is it surrounded by?

Answer 5

Sarcolemma = PM for muscle cells
Surrounded by a basement membrane and a layer of thin CT called endomysium

Endomysium = reticular fiber (Collagen Type III) + fibrocytes

Question 6

What is the perimysium?

Answer 6

Dense irregular CT that surrounds a bundle/fascicle
(Collagen type I and III)

Question 7

What is the Epimysium?

Answer 7

Dense CT that surrounds an entire muscle

Question 8

What are the characteristics of cardiac muscle cells?

Answer 8

• Cardiac muscle cells are shorts, branched cells
• Has 1-2 centrally located nuclei
• Cardiac muscle cells are connected by intercalated disks
• Intercalated disks have gap junctions → allows ion flow throughout the cardiac tissue → cooridnated contraction → heart can work as a pump
• Contraction in Involuntary
• Striated/stirped → comprised of myofibrils and sarcomeres for contractility

Question 9

What are the characteristics of smooth muscle cells?

Answer 9

• NOT striated
• Movement is involuntary
• 1 centrally located nucleus
• No intercalated disks
• In longitudinal section, the nucleus appears as wide as the fiber

Question 10

Where are smooth muscles found?

Answer 10

• Blood vessel walls
• Airways
• Digestive wall
• Bladder
• Reproductive system