LESSON 3: MUSCLE TISSUES LBBBIO7
FIRST TRIMESTER | 2025-2026
■ Regulatory proteins: tropomyosin and
SYNCHRONOUS MEETING NOTES troponin (thin)
● Striations (Skeletal Muscle)
○ The sarcomere contains the A bands and l
3rd Group - The Muscle Tissues
bands.
■ It is surrounded by the sarcoplasmic
● Highly specialized tissue reticulum
● Functions: ○ A band (Anisotropic): dark, contains myosin
○ Movement filaments
○ Transport of substances ■ Composed of :
● Examples: Smooth muscle in the alimentary tract ● H band (lighter and on the
sides)
Laboratory Materials ● M band (darker and on the
middle)
● Striated Muscle Tissue ○ I band (Isotropic): light, contains actin filaments
○ 2 types: Skeletal and Cardiac only
○ In the laboratory, slides labeled as "striated" ■ Thin actin filaments are bound to the
usually refer to skeletal muscle protein α-acitin, which binds the, to
● Non-striated Muscle Tissue the dense Z-line
○ Smooth muscle ● The Z line crosses the central
region of the I band
Study Guide vertically
■ Titin for the myosin filaments
■ Nebulin extends the length of actin
● Types of Muscle Tissue filaments
1. Skeletal Muscle ■ Desmin extends from the Z line of one
○ Striated (dark and light bands) myofibril to another and attaches
○ Voluntary them to the sarcolemma
○ Provides framework for the body ○ T Tubules and Triads
2. Cardiac Muscle ■ T tubules = invaginations of
○ Striated sarcolemma that penetrate myofibrils
○ Involuntary at A–I junctions.
○ Found only in the heart ■ Each T tubule + 2 terminal cisternae of
○ Distinguishing feature: intercalated discs – allow SR = triad.
fast transmission of impulses ■ Function: Carries nerve impulse deep
3. Smooth Muscle into fiber → triggers calcium release
○ Non-striated → synchronous contraction of all
○ Involuntary sarcomeres.
○ Arranged in sheets ○ During muscle contraction, the length of the
○ Function: Peristaltic movement (e.g., intestinal filaments remain unchanged but the size of the
motility) sarcomere decreases.
● Structural Organization ■ Z lines are drawn closer together
○ Myofibrils → grouped together form muscle ■ Thick and thin filaments slide past
fibers → grouped into fascicles each other
○ Myofibrils: most basic anatomical unit, ■ I bands and H bands are narrowed
composed of the myofilaments that make up the ■ A bands remain the same
sarcomere ○ Triad (skeletal muscle): 1 T tubule + 2 terminal
○ Sarcomere: basic functional unit of a muscle cisternae of sarcoplasmic reticulum, located at
■ Contains myofilaments: A–I junctions.
● Actin (thin) ○ Dyad (cardiac muscle): 1 T tubule + 1 terminal
● Myosin (thick) cisterna of sarcoplasmic reticulum, usually at Z
line.
LBBBIO7: Histology Laboratory LESSON 3 1
FIRST TRIMESTER | 2025-2026
■ Regulatory proteins: tropomyosin and
SYNCHRONOUS MEETING NOTES troponin (thin)
● Striations (Skeletal Muscle)
○ The sarcomere contains the A bands and l
3rd Group - The Muscle Tissues
bands.
■ It is surrounded by the sarcoplasmic
● Highly specialized tissue reticulum
● Functions: ○ A band (Anisotropic): dark, contains myosin
○ Movement filaments
○ Transport of substances ■ Composed of :
● Examples: Smooth muscle in the alimentary tract ● H band (lighter and on the
sides)
Laboratory Materials ● M band (darker and on the
middle)
● Striated Muscle Tissue ○ I band (Isotropic): light, contains actin filaments
○ 2 types: Skeletal and Cardiac only
○ In the laboratory, slides labeled as "striated" ■ Thin actin filaments are bound to the
usually refer to skeletal muscle protein α-acitin, which binds the, to
● Non-striated Muscle Tissue the dense Z-line
○ Smooth muscle ● The Z line crosses the central
region of the I band
Study Guide vertically
■ Titin for the myosin filaments
■ Nebulin extends the length of actin
● Types of Muscle Tissue filaments
1. Skeletal Muscle ■ Desmin extends from the Z line of one
○ Striated (dark and light bands) myofibril to another and attaches
○ Voluntary them to the sarcolemma
○ Provides framework for the body ○ T Tubules and Triads
2. Cardiac Muscle ■ T tubules = invaginations of
○ Striated sarcolemma that penetrate myofibrils
○ Involuntary at A–I junctions.
○ Found only in the heart ■ Each T tubule + 2 terminal cisternae of
○ Distinguishing feature: intercalated discs – allow SR = triad.
fast transmission of impulses ■ Function: Carries nerve impulse deep
3. Smooth Muscle into fiber → triggers calcium release
○ Non-striated → synchronous contraction of all
○ Involuntary sarcomeres.
○ Arranged in sheets ○ During muscle contraction, the length of the
○ Function: Peristaltic movement (e.g., intestinal filaments remain unchanged but the size of the
motility) sarcomere decreases.
● Structural Organization ■ Z lines are drawn closer together
○ Myofibrils → grouped together form muscle ■ Thick and thin filaments slide past
fibers → grouped into fascicles each other
○ Myofibrils: most basic anatomical unit, ■ I bands and H bands are narrowed
composed of the myofilaments that make up the ■ A bands remain the same
sarcomere ○ Triad (skeletal muscle): 1 T tubule + 2 terminal
○ Sarcomere: basic functional unit of a muscle cisternae of sarcoplasmic reticulum, located at
■ Contains myofilaments: A–I junctions.
● Actin (thin) ○ Dyad (cardiac muscle): 1 T tubule + 1 terminal
● Myosin (thick) cisterna of sarcoplasmic reticulum, usually at Z
line.
LBBBIO7: Histology Laboratory LESSON 3 1
