Muscle Tissue Lecture 1

Question 1

Perimysium

Answer 1

• Surrounds a group of muscle fibers (fascicle).
• Consists of dense irregular connective tissue.
• Contains collagen and elastic fibers, blood vessels, and nerves supplying muscle fibers within the fascicle.

Question 2

Epimysium

Answer 2

• Surrounds the entire skeletal muscle.
• Composed of dense irregular connective tissue.
• Separates muscle from other tissues/organs.
• Continues with tendons and deep fascia.

Question 3

Endomysium

Answer 3

• Surrounds and separates each muscle fiber (muscle cell) within a fascicle.
• Provides support and structure to muscle fibers.

Question 4

Skeletal Muscle Tissue

Answer 4

• Found in skeletal muscle.
• Elongated, cylindrical cells with multiple nuclei (multinucleate).
• Striated (striped) appearance due to arrangement of contractile proteins.
• Voluntary control.

Functions: Move and stabilize skeleton, guard entrances and exits to digestive, respiratory, urinary tracts, generate heat, protect internal organs.

Question 5

Cardiac Muscle Tissue

Answer 5

• Found only in the heart.
• Cells (cardiocytes) are short, branched, and usually have a single nucleus.
• Striated appearance.
• Involuntary control.
• Functions to move blood and maintain blood pressure.

Question 6

Smooth Muscle Tissue

Answer 6

• Found throughout the body (skin, blood vessel walls, many organs of various systems).
• Short, spindle-shaped, nonstriated, and have a single nucleus.
• Involuntary control.
• Functions: Move food, urine, and reproductive secretions, control diameter of respiratory passageways and blood vessels.

Question 7

Fascia

Answer 7

• Dense sheet or broad band of irregular connective tissue.
• Lines the body wall and limbs, supports, and surrounds muscles.

Question 8

Superficial Fascia

Answer 8

• Also known as the subcutaneous layer or hypodermis.
• Blends with the deepest part of the skin.
• Separates muscle from the skin, packed with nerves, blood vessels, adipose tissue, connective tissue, & lymphatic vessels.

Question 9

Deep Fascia

Answer 9

• Dense (fibrous) connective tissue surrounding a muscle or group of muscles.
• Allows free movement of muscles and fills the space between them.

Question 10

Tendons:

Answer 10

• Dense regular connective tissue extending from muscle to bone.
• Continuous with epimysium, perimysium, and endomysium.
• Typically long, cylindrical, and tubular.

Question 11

Aponeurosis

Answer 11

• Broad and flat tendon.
• Attaches muscles to bone or muscles to muscles.
• Examples: epicranial aponeurosis, thoracolumbar fascia.

Question 12

Synovial Tendon Sheaths

Answer 12

• Provide extra protection for tendons in high-stress areas.
• Serve as a “skin for tendons”.
• Examples: hand, wrist, foot, ankle.

Question 13

Muscle Fibers/Cells:

Answer 13

• Fundamental unit of muscles.
• Develop from myoblasts, immature muscle cells.
• Also referred to as myocytes.

Question 14

Skeletal Muscle Histology

Answer 14

• Number of muscle fibers is predetermined at birth, doesn’t undergo mitosis.
• Undergo hypertrophy (increase in size) but not hyperplasia (increase in number).

Question 15

Hypertrophy

Answer 15

• Increase in size of the muscle.

Question 16

Hyperplasia

Answer 16

• Increase in number of muscle fibers.
• Occurs during embryonic development

Question 17

Atrophy

Answer 17

• Loss of myofibrils and muscle fiber size.
• Due to lack of use or innervation.

Question 18

Sarcolemma

Answer 18

• Muscle fibre cell membrane.
• Surrounds sarcoplasm.
• Selective permeability creates resting membrane potential.
• Reversal of charge initiates muscle contraction, triggered by nerve cell impulse.

Question 19

Myofibrils

Answer 19

• Contractile organelles containing myofilaments.
• Rod-like structures within muscle fiber.
• Approximately 1 μm in diameter.
• Around 2000 myofibrils per myocyte in untrained adults.

Question 20

Myofilaments

Answer 20

• Contractile proteins within myofibrils.
• Responsible for muscle contraction

Two main types:

• Thick filaments (myosin filaments): 15 nm in diameter, made of myosin protein.
• Thin filaments (actin filaments): 7 nm in diameter, made of actin protein.

Question 21

Myoglobin

Answer 21

• Protein found only in muscle fibers.
• Binds oxygen for ATP production.

Protein for oxygen storage in muscle fibres

Question 22

Sarcoplasmic Reticulum (SR)

Answer 22

• Smooth membranous sac encircling myofibrils.
• Stores calcium ions necessary for muscle contraction.
• Release of calcium initiates muscle contraction.

Question 23

Transverse Tubules (T-tubules)

Answer 23

• Tiny invaginations of sarcolemma.
• Activate SR by transmitting nerve impulses.
• Surrounded by terminal cisternae of SR.

Question 24

Terminal Cisternae

Answer 24

• Enlargements of SR.
• Form on both sides of T-tubules.
• Store and release calcium ions.

Question 25

Triads

Answer 25

• Grouping consisting of a T-tubule and two terminal cisternae.
• Essential for excitation-contraction coupling.
• Includes T-tubules from outside muscle fiber and terminal cisternae from inside.