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Muscle Anatomy and Physiology Review

Muscle Anatomy and Physiology Study Notes

  • Skeletal Muscles: Responsible for voluntary movements and are attached to bones via tendons, playing a crucial role in locomotion and posture.

Axial Muscles

  • Temporomandibular Joint (TMJ) Muscles

    • Temporalis

    • Origin: Temporal fossa, temporal fascia

    • Insertion: Apex and medial surface of coronoid process of mandible

    • Masseter

    • Origin: Maxillary process of zygomatic bone, inferior border of zygomatic arch

    • Insertion: Lateral surface of ramus and angle of mandible

    • Medial Pterygoid

    • Origin: Tuberosity of maxilla; medial surface of lateral pterygoid plate of sphenoid bone

    • Insertion: Medial surface of ramus and angle of mandible

    • Lateral Pterygoid

    • Superior head: Infratemporal crest of greater wing of sphenoid bone

    • Inferior head: Lateral surface of lateral pterygoid fovea on neck of condyloid process of mandible

    • Role: Stabilizes condylar head during closure; medial movement of mandible

Neck Muscles

  • Sternocleidomastoid

    • Sternal head: Superior part of anterior surface of manubrium sterni

    • Clavicular head: Superior surface of medial third of the clavicle

    • Insertion: Lateral surface of mastoid process of temporal bone; lateral half of superior nuchal line of occipital bone

  • Scalenes

    • Origin: Transverse processes of cervical vertebrae

    • Insertion: First rib

  • Splenius Capitis

    • Origin: Spinous processes of vertebrae C7-T3, nuchal ligament

    • Insertion: Lateral superior nuchal line of occipital bone, mastoid process of temporal bone

  • Splenius Cervicis

    • Origin: Spinous processes of T3-T6

    • Insertion: Transverse processes of C1-C3 vertebrae

  • Suboccipitals

    • Muscles: Rectus Capitis Posterior Major & Minor, Oblique Capitis Superior & Inferior

    • Role: Inserts on lateral/medial part of inferior nuchal line of the occipital bone

  • Prevertebral Muscles

    • Types: Longus Capitis, Longus Colli, Rectus Capitis Anterior, Rectus Capitis Lateralis

    • Role: Insertion on basilar part of occipital bone and the anterior arch of atlas

Anterior Trunk Muscles

  • Rectus Abdominis

    • Origin: Pubic symphysis, pubic crest

    • Insertion: Xiphoid process, costal cartilages of ribs 5-7

  • External Oblique

    • Origin: External surfaces of ribs 5-12

    • Insertion: Linea alba, pubic tubercle, anterior half of iliac crest

  • Internal Oblique

    • Origin: Anterior two thirds of iliac crest, iliopectineal arch, thoracolumbar fascia

    • Insertion: Inferior borders of ribs 10-12, linea alba, pubic crest & pectin pubis

  • Transverse Abdominis

    • Origin: Internal surfaces of costal cartilages of ribs 7-12, thoracolumbar fascia, anterior two thirds of iliac crest, iliopectineal arch

    • Insertion: Linea alba, aponeurosis of internal abdominal oblique muscle; pubic crest, pectineal line of pubis

  • Diaphragm

    • Origin: Posterior aspect of xiphoid process, internal surfaces of lower costal cartilages and ribs 7-12, medial/lateral arcuate ligaments

    • Insertion: Central tendon of diaphragm

Posterior Trunk Muscles

  • Iliocostalis

    • Iliocostalis Cervicis: Angle of ribs 3-6 to transverse process of vertebrae C4-C6

    • Iliocostalis Thoracis: Angle of ribs 7-12 to angles of ribs 1-6, transverse process of vertebrae C7

    • Iliocostalis Lumborum: Lateral crest of sacrum, medial end of iliac crest, thoracolumbar fascia to angles of ribs 5-12, transverse process of vertebrae L1-L4

  • Longissimus

    • Longissimus Capitis: Transverse process of vertebrae C4-T5 to mastoid process of temporal bone

    • Longissimus Cervicis: Transverse process of vertebrae T1-T5 to transverse process of vertebrae C2-C6

    • Longissimus Thoracis: Lumbar part (lumbar intermuscular aponeurosis, medial part of sacropelvic surface of ilium, posterior sacroiliac ligament) and thoracic part (spinous/transverse processes of vertebrae L1-L5)

  • Spinalis

    • Spinalis Capitis: Spinous process of C7-T1 vertebrae to occipital bone

    • Spinalis Cervicis: Spinous process of C7-T1 vertebrae; nuchal ligament to spinous process of C2-C4 vertebrae

    • Spinalis Thoracis: Spinous process of T11-L2 to spinous process of T2-T8 vertebrae

  • Semispinalis

    • Origin: Articular process of vertebrae C4-C7, transverse process of vertebrae T1-T6

    • Insertion: Between superior and inferior nuchal lines of occipital bone

  • Quadratus Lumborum

    • Origin: Iliac crest, iliolumbar ligament

    • Insertion: Inferior border of rib 12, transverse processes of vertebrae L1-L4

  • Multifidus

    • Covering cervicis, thoracis, and lumborum regions through various origins and insertions

  • Interspinales

    • Cervicis: Superior aspect of spinous processes of vertebrae C3-T1

    • Thoracis: Superior aspect of spinous process of vertebrae T2, T11, and T12

    • Lumborum: Superior aspects of spinous processes of vertebrae L2-L5

  • Intertransversarii

    • Lateral: Transverse and accessory processes of vertebrae L1-L4

    • Medial: Accessory processes of vertebrae L1-L4

Actions and Nerve Supply

  • Masseter

    • Anterior fibres: Elevates mandible

    • Posterior part: Retracts mandible

    • Motor Supply: From the deep temporal nerves, branches of the third division of the trigeminal nerve

  • Medial Pterygoid

    • Actions: Elevates and protrudes mandible; medial movement (rotation) of mandible

    • Nerve Supply: Medial pterygoid nerve of mandibular nerve

  • Lateral Pterygoid

    • Actions: Protrudes and depresses mandible, stabilizes condylar head during closure; medial movement of mandible

    • Nerve Supply: Lateral pterygoid nerve of mandibular nerve

  • Sternocleidomastoid

    • Unilateral contraction: Ipsilateral flexion; contralateral rotation

    • Bilateral contraction: Extension of neck

    • Nerve Supply: Accessory nerve, branches of cervical plexus

  • Scalenes

    • Functions: Facilitates neck flexion; elevates first rib

    • Nerve Supply: Branches of anterior rami of spinal nerves

Vocabulary and Definitions

  • Muscle: A band/bundle of fibrous tissue in a human/animal body that has the ability to contract, producing movement or maintaining position.

  • Fascicle: A bundle of structures, such as nerve or muscle fibers.

  • Muscle Fiber: Elongated, cylindrical cells that make up skeletal muscles, responsible for generating force and movement in the body.

  • Myofibril: Make up muscle fibers; cylindrical structures that contain the contractile proteins actin and myosin.

  • Sarcomere: Make up myofibrils; responsible for muscle contraction.

  • Tendon: A tough, fibrous cord-like tissue that connects muscles to bones.

  • Musculotendinous Junction: Anatomical interface where muscle tissue connects with tendon tissue, forming a crucial unit for force transmission and movement.

  • Agonist: Primary muscle responsible for producing a specific movement.

  • Antagonist: A muscle that opposes the action of another muscle (agonist).

  • Co-Contraction: Simultaneous contraction of both the agonist and antagonist muscles that cross a particular joint.

  • Synergist: A muscle that assists the prime mover (agonist) in performing a specific movement.

  • Active Insufficiency: The inability of a multi-joint muscle to develop effective tension and complete its full range of motion.

  • Passive Insufficiency: The inability of a multi-joint muscle to lengthen sufficiently to allow a full range of motion simultaneously at all the joints it crosses.

Muscle Contraction Types

  • Open Kinetic Chain: A series of linked body segments/joints such as arm/leg where the end segment (hand/foot) moves freely in space without being fixed or constrained.

  • Closed Kinetic Chain: A movement where the distal (end) segment of an extremity is fixed against a stationary surface.

  • Isometric Contraction: A type of muscle contraction where the muscle length remains constant while it generates force (e.g., plank).

  • Concentric Contraction: A type of muscle contraction where the muscle shortens while generating force (e.g., bicep curl).

  • Eccentric Contraction: A type of muscle contraction where the muscle lengthens while exerting force (e.g., squat).

  • Isokinetic Contraction: Muscle contractions that occur at a constant speed (e.g., isokinetic leg press).

Muscle Tissue Properties

  • Irritability: The property of receiving and responding to a stimulus by generating an electrical signal, which leads to other muscle functions like contraction.

  • Contractility: The muscle's ability to shorten and generate force when electrically stimulated, allowing it to pull on attachment points and perform movement.

  • Extensibility: A property of muscle tissue that allows it to be stretched or elongated.

  • Elasticity: The property of a tissue to return to its original size and shape after being stretched or compressed by a force.