Myotomes, Dermatomes, and Muscle Contractions

Myotomes and Dermatomes

• Myotome: A group of muscles controlled by a single spinal nerve.
• C5 myotome involves muscles in the upper arm, controlled by the C5 spinal nerve.
• These muscles include deltoids, infraspinatus, biceps brachii, and brachioradialis.
• The C5 myotome is responsible for shoulder abduction, external rotation, and elbow flexion.

Isometric and Isotonic Contractions

• Isometric Contraction: Muscle length remains constant while tension increases. No movement occurs.
• Concentric Contraction: Muscle shortens during contraction, such as lifting a weight.
• Eccentric Contraction: Muscle lengthens under tension, such as lowering a weight.

Intervertebral Foramina

• The superior margin of an intervertebral foramen is formed by the inferior vertebral notch of the vertebra above.
• The anterior margin is formed by the intervertebral disc between vertebral bodies.
• The inferior margin is the superior vertebral notch of the vertebra below.
• The posterior margin is the zygapophysial (facet) joint of the adjacent vertebrae.
• Each pedicle contains superior and inferior vertebral notches.

Planes of the Body

• Sagittal Plane: Divides the body into left and right halves.
• Midsagittal (Median) Plane: Divides the body into equal left and right halves.
• Frontal (Coronal) Plane: Divides the body into front and back parts.
• Transverse (Horizontal) Plane: Divides the body into upper and lower parts.

Types of Joints

• Fibrous Joints: Connected by dense connective tissue; little to no movement (skull sutures).
• Cartilaginous Joints: Connected by cartilage; limited movement (symphyses, synchondroses).
• Synovial Joints: Freely movable joints with a synovial cavity; six types.

Six Types of Synovial Joints

• Plane (Gliding) Joints: Allow sliding movements (intercarpal joints).
• Hinge Joints: Permit flexion and extension (elbow, knee).
• Pivot Joints: Allow rotational movement (atlantoaxial joint).
• Condyloid (Ellipsoidal) Joints: Permit movement in two planes (wrist joint).
• Saddle Joints: Allow movement in two planes with greater freedom (thumb carpometacarpal joint).
• Ball-and-Socket Joints: Permit movement in multiple planes (shoulder and hip joints).

Ligaments of the Vertebral Column

• Anterior Longitudinal Ligament: Prevents hyper-extension.
• Posterior Longitudinal Ligament: Prevents hyper-flexion.
• Ligamenta Flava: Connects laminae; maintains upright posture.
• Interspinous Ligaments: Connect spinous processes; limit flexion.
• Supraspinous Ligament: Connects tips of spinous processes; limits flexion.
• Intertransverse Ligaments: Connect transverse processes; limit lateral flexion.

Spinal Cord

• The spinal cord ends at the L1-L2 vertebrae in adults.

• The dorsal root contains sensory fibers.

• The ventral root contains motor fibers.

• Spinal nerves exiting the spinal column branch out into rami.

  • Dorsal rami: innervate deep back muscle and skin on the back.
  • Ventral rami: form plexuses that innervate limbs and the anterior trunk.

Spinal Tap (Lumbar Puncture)

• Position: Between L3-L4 or L4-L5 vertebrae.
• Landmark: Iliac crest aligns with L4 vertebra.

Spinal Nerves and Intervertebral Foramina

• Spinal nerves exit the spinal cord, branching into anterior and posterior rami.
• The anterior rami enter the intervertebral foramina.

Characteristic Features of Vertebrae

• The vertebral column has 33 vertebrae (7 cervical, 12 thoracic, 5 lumbar, 5 sacral, 4 coccygeal).
• The cervical vertebrae are the smallest and possess transverse foramina.
• Thoracic vertebrae have facets for the ribs.
• Lumbar vertebrae have large, kidney-shaped bodies.
• Sacrum and coccyx are formed by fused vertebrae.

Myotomes and Dermatomes: One Below Rule

• A herniation at a disc typically affects the nerve root below the herniated disc.

Specific Muscles, Bones, and Injuries

• Information about specific muscles, spinal nerves, or injuries (e.g., nursemaid's elbow, brachial plexus injury) is dispersed throughout the notes and needs further investigation.