Lab exam 2: axial miscles

Overview of Muscular Anatomy Check-off Procedures

  • Task: Label all axial muscles on torso models (either large or small).
  • Setting: Groups of students at tables for collaboration and instruction.
  • Microscope Observation: Importance of observing muscle structures under a microscope also highlighted.

Muscles of the Head, Neck, and Face

  • Visual Representation: Photos representing superficial (left side) and deep (right side) muscles.
  • Superficial: Outermost muscles visible; Deep: Muscles visible after superficial layers are removed.
  • Functions: Control head movement, mastication (chewing), facial expressions, and speech.

Key Muscles and Their Descriptions

  • Epicraneous (Frontal Belly):

    • Location: Forehead region.
    • Meaning: "Epicraneous" from Greek, meaning above or in front of the skull.

  • Temporalis Muscle:

    • Function: Covers the temporal bone; involved in mastication.

  • Orbicularis Oculi:

    • Location: Circular muscle around the eye.
    • Function: Closing eyelids.

  • Zygomaticus Major and Minor:

    • Minor Muscles: Located above major; involved in facial expression.
    • Major Muscles: Positioned below; contributes to smiling.

  • Orbicularis Oris:

    • Function: Circular muscle around the mouth, facilitates oral movements.

  • Masseter:

    • Function: Primary muscle for mastication, significant for grinding food.

  • Buccinator:

    • Description: Positioned deep to other facial muscles.
    • Function: Assists in chewing by keeping food between teeth.

  • Sternocleidomastoid Muscle:

    • Function: Flexes and rotates the head and neck.
    • Anatomical Breakdown:
    • Origin: Manubrium of sternum and medial clavicle.
    • Insertion: Mastoid process of the temporal bone.
    • Action: Flexion of the neck.

Muscles of the Trunk

Superficial and Deep Muscles Description

  • Pectoralis Major:

    • Location: Superficial chest muscle.
    • Origin: Clavicle, sternum, costal cartilage of ribs 1-7.
    • Insertion: Intertubercular sulcus of the humerus.
    • Action: Flexes, adducts, and medially rotates the arm.

  • Pectoralis Minor:

    • Location: Below the pectoralis major.
    • Action: Stabilizes the scapula.

  • Latissimus Dorsi:

    • Location: Large back muscle; visible from the front.
    • Origin: Spinous processes of T7-T12, iliac crest, and ribs 8-12.
    • Insertion: Intertubercular sulcus of the humerus.
    • Action: Extends, adducts, and medially rotates the arm.

Muscles of Respiration

  • Intercostal Muscles:

    • Classification:
    • Internal Intercostals: Between costal cartilage, facilitate robust inhalation.
    • External Intercostals: Between the ribs, assist in normal breathing.

  • Diaphragm:

    • Function: Primary muscle in breathing; flattens during inhalation to increase thoracic cavity volume.

Muscles of the Abdominal Wall

  • Rectus Abdominis:

    • Location: Medial abdominal region; straight muscle fibers.
    • Origin: Pubic crest and pubic symphysis.
    • Insertion: Xiphoid process and costal cartilages of ribs 5-7.
    • Action: Flexes the vertebral column and compresses abdominal contents.

  • Muscle Layers:

    • External Oblique: Most superficial; wraps around the abdomen.
    • Internal Oblique: Middle layer; also spans the abdomen laterally.
    • Transversus Abdominis: Deepest layer, helping to compress abdominal contents.

Muscles of the Back

Erector Spinae Muscle Group

  • Overall Function: Keeps spine erect; assists in extension and lateral flexion of the spine.
  • Components:
    • Iliocostalis: Most lateral; connects ribs to iliac crest.
    • Longissimus: Middle group; spans across the back.
    • Spinalis: Most medial; adjacent to the spine.

Trapezius Muscle

  • Location: Diamond shape on the upper back.
  • Origin: Occipital bone, and spinous processes of C7 through T12.
  • Insertion: Clavicle, acromion, and spine of the scapula.
  • Action: Elevates, retracts, and rotates the scapula and extends the neck.

Summary

  • Comprehensive knowledge of the axial muscles, including names, locations, origins, insertions, and main actions is crucial for understanding human anatomy related to movement and functionality in daily tasks. Each muscle has specific contributions to physiological processes such as respiration, posture, and mastication.