Chapter 11: Naming Muscles and Muscles of the Head and Neck and Vertebral Column

Divisions of the Skeletal System:
- Axial Skeleton:
- Muscles have origins and insertions on the axial skeleton.
- Function to:
  - Support and move the head and vertebral column.
  - Facilitate nonverbal communication.
  - Move the mandible during chewing.
  - Aid in breathing.
  - Support and protect abdominal and pelvic organs.
- Appendicular Skeleton:
- Muscles control movements of the upper and lower limbs.
- Muscles also control movements of the pectoral and pelvic girdles.
- Organized into groups based on location.

Organizational Patterns of Skeletal Muscle Fibers:
- Fascicle Arrangement:
- Circular:
- Parallel:
- Convergent:
  - Broad origin and fibers converge toward a single insertion point, typically a tendon.
- Pennate:
  - Fibers attach obliquely (at an angle) to a central tendon.

Classification of Muscle Actions:
- Agonist:
- The primary muscle responsible for generating movement at a joint.
- Antagonist:
- A muscle that opposes the action of another muscle.
- Synergist:
- Assists the agonist for a specific action at a joint.

Based on Action:
- Indication of primary function (e.g., flexor, extensor, pronator).
- Example: Flexor digitorum longus muscle for flexing the digits.
Based on Specific Body Regions:
- Example: Tibialis anterior located on the anterior surface of the tibia.
- Muscles close to the surface identified as superficialis or externus.
- Deeper muscles identified as profundus or internus.
Based on Muscle Attachment:
- Often identify origins, insertions, and attachments.
- Example: Sternocleidomastoid muscle, with origins on sternum and clavicle, and insertion on mastoid process.
Based on Fiber Orientation:
- Rectus: Lengthwise fibers.
- Oblique: Fibers extending at an angle.
- Example: Internal oblique muscles.
Based on Muscle Shape:
- Deltoid: Triangle shape; rhomboid: rhombus shape.
- Orbicularis: Circular shape; trapezius: trapezoid shape.
- Terms for size include brevis (short), longus (long), magnus (big), maximus (largest), minor (small), minimus (smallest).
Based on Muscle Heads/Tendons of Origin:
- Names indicate number of origins or muscle heads.
- Example: Biceps muscle has two tendons of origin; quadriceps muscle has four heads.

Characteristics:
- Originate in the superficial fascia or skull bones.
- Insert into the superficial fascia of skin, causing the skin to move during contraction.
- Most are innervated by the facial nerve (CN VII).
List of Muscles (anterior and lateral view):
- Epicranius (Frontal and Occipital bellies).
- Orbicularis oculi.
- Zygomaticus major & minor.
- Risorius.
- Depressor anguli oris.
- Depressor labii inferioris.
- Platysma.
- Buccinator.
- Orbicularis oris.
- Mentalis.

Extraocular Muscles:
- Function to move the eyes and insert on the sclera (outer surface of the eye).
- Comprised of six muscles:
- Four rectus muscles (medial, lateral, inferior, and superior).
- Two oblique muscles (inferior and superior).
- Occupational Actions:
- Inferior oblique: Moves the eye superiorly and laterally.
- Superior oblique: Moves the eye inferiorly and laterally.

Definition: Refers to the process of chewing, moving the mandible at the temporomandibular joint (TMJ).
Four paired muscles involved:
- Temporalis:
- Broad fan-shaped muscle.
- Origin: Temporal lines of the skull.
- Insertion: Coronoid process of the mandible.
- Action: Elevates and retracts the mandible.
- Masseter: Elevates and protracts the mandible; most powerful muscle for jaw movement.
- Medial and Lateral Pterygoids:
- Medial Pterygoid:
  - Arises from pterygoid process of sphenoid bone; inserts on mandible; moves mandible side to side during chewing.
- Lateral Pterygoid: Also involved in lateral movement and efficiency while chewing.

Intrinsic Muscles: Responsible for the precise movements of the tongue.
Extrinsic Muscles:
- Originate on head and neck structures.
- Insert on the tongue.
- Named with the suffix -glossus.
- Responsible for movements such as speech and food manipulation.
- Most are innervated by the hypoglossal nerve (CN XII).

Pharynx:
- A funnel-shaped tube posterior to oral and nasal cavities.
- Formed by several muscles that aid in swallowing.

Anteriolateral Muscles

Sternocleidomastoid:
- Origin: Manubrium and sternal end of clavicle.
- Insertion: Mastoid process.
- Action: Flexion and rotation of the head to the opposite side.
Scalenes Muscles (anterior, middle, posterior):
- Origin: Cervical vertebrae.
- Insertion: 1st and 2nd ribs.
- Action: Flex neck; elevate 1st and 2nd ribs during forced inspiration.

Posteriolateral Muscles

Condition in newborns characterized by shortened sternocleidomastoid.
Can arise from birth trauma or prenatal positioning.
Results in head tilting to the affected side and chin towards the unaffected side.
Treatments Include:
- Physical therapy.
- Botulinum toxin to impair contraction of the affected muscle.

Complex Muscles with Multiple Origins and Insertions:
Erector Spinae:
- Vital for maintaining posture and standing erect:
- When contracted together, they extend the vertebral column.
- When contracted unilaterally, they facilitate lateral flexion toward that side.
Three Groups of Erector Spinae Muscles:
- Iliocostalis Group:
- Most laterally placed; contains cervical, thoracic, and lumbar parts.
- Longissimus Group:
- Located medial to iliocostalis; composed of capitis, cervical, and thoracic parts; inserts on vertebral transverse processes.
- Spinalis Group:
- Most medial group; contains cervical and thoracic parts.
Other Muscles:
- Transversospinalis Muscles:
- Connect and stabilize the vertebrae; located deep to the erector spinae.
- Quadratus Lumborum:
- Primarily located in the lumbar region; extends the vertebral column when contracted bilaterally; laterally flexes the column unilaterally.