General myology - Copy_merge Copy

General Myology

  • Myology is the science that studies all types of muscles, tendons, and accessory structures in the body.

  • Muscle tissue constitutes almost fifty percent of total body weight.

Functions of Muscles

  • Movement Production: Muscles enable body movement and locomotion.

  • Restraint: They help in restraining unnecessary movement.

  • Support: Muscles support bones and other structures in the body.

  • Vital Functions: Responsible for heartbeats, sound production, peristaltic movements, vision, and speech.

  • Heat Production: Skeletal muscles generate heat through muscle tone, even at rest, thus regulating temperature in endothermic (warm-blooded) animals.

Types of Muscle

1. Cardiac Muscle

  • Striated and involuntary

  • Located in the walls of the heart

  • Characteristics: Quick and powerful contractions without long-lasting contractions; fatigue is minimal.

  • Blood supply is abundant.

2. Smooth (Visceral) Muscle

  • Non-striated and involuntary

  • Found in hollow viscera (e.g., intestines, blood vessels, bladder)

  • Characteristics: Slow and mild contractions, sustain contractions without fatigue.

  • Blood supply is scant.

3. Skeletal Muscle

  • Striated and voluntary

  • Attach to skeleton, enabling gross movements

  • Characteristics: Quick contractions; highly fatigue-prone; versatile in function.

  • Blood supply is abundant.

Muscle Cell Classification

Major Types of Muscle Cells

  • Skeletal Muscle Cells: Multinucleate, responsible for voluntary movements.

  • Cardiac Muscle Cells: Uninucleate, involuntary heart contractions.

  • Smooth Muscle Cells: Mostly uninucleate, involved in involuntary movements of internal organs.

Muscle Features and Anatomy

Muscle Structure

  • Origin: The stable attachment point of a muscle.

  • Insertion: The movable attachment point where contraction occurs.

  • Belly (Venter): The thickest part of the muscle.

Muscle Attachments

  • Tendons: Ribbon-like structures connecting muscles to bones.

  • Aponeuroses: Flattened tendon structures connecting muscles.

Muscle Shapes

  1. Fusiform: Spindle-shaped (e.g., biceps).

  2. Planus: Flat shape (e.g., abdominal muscles).

  3. Biceps: Two-head muscle (e.g., biceps brachii).

  4. Triceps: Three-head muscle (e.g., triceps brachii).

  5. Quadriceps: Four-head muscle.

  6. Digastric: Two-belly muscle.

  7. Orbicularis: Ring-shaped (e.g., sphincters).

Muscle Classification by Function

  • Uniarticular: Cross only one joint (e.g., supraspinatus).

  • Biarticular: Cross two joints (e.g., biceps brachii).

  • Polyarticular: Cross more than two joints (e.g., flexors/extensors of digits).

Muscle Actions

  • Flexors & Extensors: reduce/increase angle between body parts.

  • Adductors & Abductors: move body parts toward/away from midline.

  • Supinators & Pronators: rotate limb elements.

  • Elevators & Depressors: lift or lower body parts.

  • Rotators, Sphincters, & Dilators: vary the movement and opening of structures.

Fiber Orientation and Arrangement

  1. Parallel: fibers run the length of the muscle (e.g., Sartorius).

  2. Fusiform: converges at both ends (e.g., Biceps).

  3. Pennate: fibers attach obliquely to a central tendon.

    • Unipennate: half feather (e.g., genioglossus).

    • Bipennate: complete feather (e.g., gastrocnemius).

    • Multipennate: many tendons (e.g., deltoid).

Accessory Structures Associated with Skeletal Muscles

  1. Fascia:

    • Superficial Fascia: Fatty layer under the skin.

    • Deep Fascia: Covers muscles, providing structural integrity.

  2. Synovial Bursa: Fluid-filled structures that reduce friction between moving parts.

    • Inflammation leads to bursitis.

  3. Synovial Sheath: Encases tendons in an elongated format to prevent friction over longer distances.

Tendon Functionality

  • Connect muscles to bones, minimizing friction, and altering direction of muscle force.

  • Sesamoid Bones: Minimize friction, change direction of muscle action.

  • Ligaments: Connect bones to one another and stabilize joints.

Arthrology

Definition of Joints

  • Joints or articulations facilitate movement, provide flexibility and stability between bones, and influence bone growth.

Joint Classification

Functional Classification

  1. Synarthrosis: Immovable joints (e.g., fibrous joints).

  2. Amphiarthrosis: Slightly movable joints (e.g., cartilaginous joints).

  3. Diarthrosis: Freely movable joints (e.g., synovial joints).

Structural Classification

  1. Fibrous Joints: No movement or joint cavity (e.g., sutures).

  2. Cartilaginous Joints: Limited movement, no joint cavity (e.g., symphysis).

  3. Synovial Joints: Movable, joint cavity present, most complex.

Characteristics of Synovial Joints

  • Presence of joint cavity, movable, incorporate various structures (e.g., ligaments, articular cartilage).

  • Essential: Articular surface, articular cartilage, articular capsule, joint cavity filled with synovial fluid.

  • Accessory: Provide additional support to joint stability.

Types of Synovial Joints by Movement

  1. Hinge Joints: Allow movement around one axis (e.g., elbow).

  2. Pivot Joints: Allow rotation around a single axis (e.g., atlantoaxial joint).

  3. Ball and Socket Joints: Multiaxial joints allowing wide range of motion (e.g., hip joint).

Movements of Synovial Joints

  • Gliding: Surface slides over one another.

  • Flexion: Decrease joint angle.

  • Extension: Increase joint angle.

  • Abduction/Adduction: Moving limbs toward or away from body midline.

  • Rotation: Movement around a limb's longitudinal axis.

  • Circumduction: Circular movement combining all the above.

Questions

  • Open forum for questions and clarification.