Anatomy & Physiology: Types of Muscles

Anatomy and Physiology Text Book Information

• Book title: Seeley's Essentials of Anatomy & Physiology
• Edition: Tenth Edition
• Authors: Cinnamon Vanputte, Jennifer Regan, Andrew Russo
• Publisher: McGraw-Hill Education
• Note: Separate PowerPoint slides are available for figures and tables, pre-inserted into PowerPoint presentations.

Types of Muscles

• Skeletal Muscle:
  • Attached to bones
  • Striated
  • Voluntarily controlled
• Cardiac Muscle:
  • Located in the heart
  • Striated
  • Involuntarily controlled
• Smooth Muscle:
  • Located in blood vessels and hollow organs
  • Non-striated
  • Involuntarily controlled

Comparison of Skeletal, Cardiac, and Smooth Muscles

• Body Location: Skeletal muscles are attached to bones or, sometimes, to skin. Cardiac muscles are located in the heart. Smooth muscles are found in walls of hollow organs.
• Cell Shape and Appearance: Skeletal muscle cells are long, cylindrical, and multinucleated, with obvious striations. Cardiac cells are branched and uninucleated and have striations and intercalated discs. Smooth muscle cells are single, fusiform (spindle-shaped), and uninucleated, without striations.
• Connective Tissue Components: Skeletal muscles have epimysium, perimysium, and endomysium. Cardiac muscles have endomysium. Smooth muscles have endomysium.
• Regulation of Contraction: Skeletal muscle contraction is voluntary and controlled by the nervous system. Cardiac muscles have a pacemaker and are controlled by the nervous system, the heart's own pacemaker, and hormonal input. Smooth muscle contraction is involuntary controlled by the nervous system and hormones.
• Speed of Contraction: Skeletal muscle contraction is slow to fast, cardiac is slow, and smooth is very slow.
• Rhythmic Contraction: Skeletal muscles do not contract rhythmically, cardiac muscles do, and smooth muscles can in some cases.

Skeletal Muscle Structure

• Skeletal muscle: Approximately 40% of body weight.
• Attachment: Skeletal muscles attach to the skeletal system, some to the skin or connective tissue sheets.
• Striations: Skeletal muscle is also called striated muscle.
• Connective Tissue Coverings:
  • Epimysium: Surrounds the entire muscle.
  • Perimysium: Surrounds fascicles (groups of muscle cells).
  • Endomysium: Surrounds individual muscle cells (fibers).

Muscle Fiber Structure

• Shape: Single cylindrical cells with multiple nuclei located at the periphery.
• Size: Ranges in length from 1 cm to 30 cm and are generally 0.15 mm in diameter.
• Sarcolemma: The cell membrane (sarcolemma) has transverse tubules (T-tubules) which are inward folds.
• Sarcoplasmic Reticulum: T-tubules are associated with enlarged portions of the smooth endoplasmic reticulum called terminal cisternae.
• Muscle Triad: T-tubules connect to the terminal cisternae to form a muscle triad.
• Sarcoplasm: The cytoplasm of a muscle fiber contains protein filaments called myofibrils.
• Myofibrils: Bundles of protein filaments (myofilaments).
• Myofilaments: Actin and myosin.

Muscles of the Head and Neck

• Facial Muscles
• Mastication Muscles: Muscles involved in chewing.
• Swallowing Muscles
• Eyes Muscles
• Head and Neck Muscles

Specific Facial Muscles

• Buccinator: Wall of the cheeks; flattens the cheek (as in whistling or blowing a trumpet);  "Kissing Muscle or Trumpeter's muscle"; compresses cheek to hold food teeth
• Depressor Anguli Oris: Lower corners of the mouth; depresses the corner of the mouth
• Levator Labii Superioris: Elevates one side of the upper lip
• OccipitoFrontalis: Moves scalp, raises eyebrows, and wrinkles forehead
• Orbicularis Oris: Closes the mouth and protrudes the lips; the "kissing" muscle
• Orbicularis Oculi: Closes the eyes, squints, blinks, and winks.
• Zygomaticus: The "smiling" muscle; elevates the upper lip and corner of the mouth

Chewing Muscles

• Masseter: Closes the jaw; elevates and pushes the mandible anteriorly
• Temporalis: Elevates and draws the mandible posteriorly
• Pterygoid:
  • Lateral: Pushes the mandible anteriorly and depresses the mandible, closes the jaw
  • Medial: Pushes the mandible anteriorly and elevates the mandible, closes the jaw

Tongue and Swallowing Muscles

• Tongue Muscles:
  • Intrinsic: Change the shape of the tongue
  • Extrinsic: Move the tongue
• Hyoid Muscles:
  • Suprahyoid: Elevates or stabilizes the hyoid bone.
  • Infrahyoid: Depresses or stabilizes the hyoid bone

Deep Neck Muscles

• Neck Flexors: Originate on the anterior side of the vertebrae, flex the head and neck.
• Neck Extensors: Originate on the posterior side of the vertebrae, extend the head and neck.

Specific Neck Muscles

• Sternocleidomastoid: Individually rotates the head; together it flexes the neck
• Platysma: Pulls the corners of the mouth inferiorly
• Trapezius: Extends and laterally flexes the neck

Trunk Muscles

• Vertebral Column
• Thorax
• Abdominal Wall
• Pelvic Floor

Specific Trunk Muscles

• Erector Spinae: Extends the vertebral column and maintains posture; divides into 3 columns: iliocostalis, longissimus, spinalis
• Deep Back Muscles: Located between spinous and transverse processes; responsible for movement of the vertebral column; extension, lateral flexion, rotation
• Thoracic Muscles:
  • Scalenes: Elevates ribs during inspiration
  • External Intercostals: Elevates ribs for inspiration
  • Internal Intercostals: Depresses ribs during forced expiration
  • Diaphragm: Moves during quiet breathing
• Abdominal Wall Muscles:
  • Rectus Abdominis: Center of the abdomen; compresses abdomen
  • External Abdominal Oblique: Sides of the abdomen; compresses abdomen
  • Internal Abdominal Oblique: Compresses abdomen
  • Transverse Abdominis: Compresses abdomen