Table 10.2 Model Inventory For Skeletal Muscles

The skeletal muscle system, a marvel of biological engineering, allows us to move, maintain posture, and perform a myriad of tasks that define our interaction with the world. Understanding the intricate inventory of skeletal muscles—their names, locations, actions, innervations, and unique characteristics—is essential for students of anatomy, physical therapists, athletes, and anyone interested in the mechanics of the human body. Table 10.2, a comprehensive model inventory for skeletal muscles, provides a structured approach to learning and referencing this complex information.

Introduction to Skeletal Muscle Inventory

Skeletal muscles, attached to bones via tendons, work in coordinated groups to produce movement. Each muscle has a specific name, often derived from its shape, size, location, or function. For example, the biceps brachii (meaning "two-headed muscle of the arm") is named for its two origins and location in the upper arm.

Key components of a skeletal muscle inventory typically include:

• Muscle Name: The standard anatomical name of the muscle.
• Origin: The fixed or less movable attachment point of the muscle.
• Insertion: The movable attachment point of the muscle.
• Action: The primary movement(s) the muscle produces.
• Innervation: The nerve(s) that supply the muscle, controlling its contraction.
• Location: The region of the body where the muscle is found.

Table 10.2 serves as a structured reference for this information, organizing it by body region (e.g., head and neck, trunk, upper limb, lower limb). This organization allows for a systematic study of muscles and their functions.

Importance of a Detailed Muscle Inventory

A detailed muscle inventory, such as Table 10.2, is crucial for several reasons:

• Anatomical Education: Provides a structured framework for learning the names, locations, and functions of muscles.
• Clinical Practice: Essential for diagnosing and treating musculoskeletal conditions.
• Physical Therapy: Guides rehabilitation programs by targeting specific muscles for strengthening and stretching.
• Athletic Training: Helps in designing training regimens to improve performance and prevent injuries.
• Research: Serves as a reference for studies on muscle physiology and biomechanics.

Head and Neck Muscles

The head and neck region contains a complex array of muscles responsible for facial expressions, chewing, swallowing, and head movements. Table 10.2 typically categorizes these muscles into groups such as facial expression muscles, mastication muscles, and neck muscles.

Facial Expression Muscles

These muscles are unique because they insert into the skin rather than bones, allowing for a wide range of expressions.

• Occipitofrontalis:
  • Origin: Occipital bone and frontal bone
  • Insertion: Skin of eyebrows and forehead
  • Action: Raises eyebrows, wrinkles forehead
  • Innervation: Facial nerve (CN VII)
• Orbicularis Oculi:
  • Origin: Medial orbital margin
  • Insertion: Skin around eyelids
  • Action: Closes eyelids, squints eyes
  • Innervation: Facial nerve (CN VII)
• Orbicularis Oris:
  • Origin: Mandible and maxilla
  • Insertion: Skin around mouth
  • Action: Closes lips, purses lips
  • Innervation: Facial nerve (CN VII)
• Zygomaticus Major:
  • Origin: Zygomatic bone
  • Insertion: Angle of mouth
  • Action: Elevates and retracts corner of mouth (smiling)
  • Innervation: Facial nerve (CN VII)
• Buccinator:
  • Origin: Maxilla and mandible
  • Insertion: Orbicularis oris
  • Action: Compresses cheek, holds food between teeth during chewing
  • Innervation: Facial nerve (CN VII)

Mastication Muscles

These muscles are responsible for the movements involved in chewing.

• Masseter:
  • Origin: Zygomatic arch
  • Insertion: Mandible
  • Action: Elevates mandible (closes jaw)
  • Innervation: Trigeminal nerve (CN V)
• Temporalis:
  • Origin: Temporal fossa
  • Insertion: Coronoid process of mandible
  • Action: Elevates and retracts mandible
  • Innervation: Trigeminal nerve (CN V)
• Medial Pterygoid:
  • Origin: Pterygoid plate of sphenoid bone
  • Insertion: Mandible
  • Action: Elevates mandible, protracts mandible
  • Innervation: Trigeminal nerve (CN V)
• Lateral Pterygoid:
  • Origin: Pterygoid plate of sphenoid bone
  • Insertion: Mandibular condyle
  • Action: Depresses and protracts mandible, moves mandible side to side
  • Innervation: Trigeminal nerve (CN V)

Neck Muscles

These muscles control head and neck movements.

• Sternocleidomastoid:
  • Origin: Sternum and clavicle
  • Insertion: Mastoid process of temporal bone
  • Action: Flexes neck, rotates head
  • Innervation: Accessory nerve (CN XI)
• Trapezius:
  • Origin: Occipital bone, spinous processes of cervical and thoracic vertebrae
  • Insertion: Clavicle and scapula
  • Action: Elevates, depresses, retracts, and rotates scapula; extends neck
  • Innervation: Accessory nerve (CN XI)
• Scalenes (Anterior, Middle, Posterior):
  • Origin: Cervical vertebrae
  • Insertion: Ribs 1 and 2
  • Action: Flexes and laterally bends neck, elevates ribs during forced inspiration
  • Innervation: Cervical spinal nerves

Trunk Muscles

The trunk muscles support the spine, enable respiration, and contribute to movements of the torso. Table 10.2 typically divides these muscles into groups such as back muscles, abdominal muscles, and muscles of respiration.

Back Muscles

These muscles support the spine and control its movements.

• Erector Spinae (Iliocostalis, Longissimus, Spinalis):
  • Origin: Sacrum, iliac crest, spinous processes of lumbar and lower thoracic vertebrae
  • Insertion: Ribs, transverse processes, and spinous processes of vertebrae
  • Action: Extends vertebral column, maintains posture
  • Innervation: Spinal nerves
• Quadratus Lumborum:
  • Origin: Iliac crest and lumbar vertebrae
  • Insertion: 12th rib and lumbar vertebrae
  • Action: Laterally flexes vertebral column, stabilizes 12th rib during respiration
  • Innervation: Lumbar spinal nerves
• Multifidus:
  • Origin: Sacrum, ilium, transverse processes of vertebrae
  • Insertion: Spinous processes of vertebrae
  • Action: Extends and rotates vertebral column
  • Innervation: Spinal nerves

Abdominal Muscles

These muscles protect abdominal organs, flex and rotate the trunk, and assist in respiration.

• Rectus Abdominis:
  • Origin: Pubic crest and symphysis
  • Insertion: Xiphoid process and costal cartilages of ribs 5-7
  • Action: Flexes vertebral column, compresses abdomen
  • Innervation: Thoracoabdominal nerves
• External Oblique:
  • Origin: Ribs 5-12
  • Insertion: Iliac crest, linea alba
  • Action: Flexes and rotates vertebral column, compresses abdomen
  • Innervation: Thoracoabdominal nerves
• Internal Oblique:
  • Origin: Iliac crest, inguinal ligament, thoracolumbar fascia
  • Insertion: Ribs 10-12, linea alba
  • Action: Flexes and rotates vertebral column, compresses abdomen
  • Innervation: Thoracoabdominal nerves
• Transversus Abdominis:
  • Origin: Ribs 7-12, iliac crest, inguinal ligament, thoracolumbar fascia
  • Insertion: Linea alba
  • Action: Compresses abdomen
  • Innervation: Thoracoabdominal nerves

Muscles of Respiration

These muscles assist in breathing.

• Diaphragm:
  • Origin: Xiphoid process, costal cartilages of ribs 7-12, lumbar vertebrae
  • Insertion: Central tendon
  • Action: Primary muscle of inspiration, increases volume of thoracic cavity
  • Innervation: Phrenic nerve
• External Intercostals:
  • Origin: Inferior border of rib above
  • Insertion: Superior border of rib below
  • Action: Elevates ribs during inspiration
  • Innervation: Intercostal nerves
• Internal Intercostals:
  • Origin: Superior border of rib below
  • Insertion: Inferior border of rib above
  • Action: Depresses ribs during expiration
  • Innervation: Intercostal nerves

Upper Limb Muscles

The upper limb muscles enable a wide range of movements in the shoulder, arm, forearm, and hand. Table 10.2 typically categorizes these muscles into groups such as shoulder muscles, arm muscles, forearm muscles, and hand muscles.

Shoulder Muscles

These muscles stabilize the shoulder joint and control movements of the humerus.

• Deltoid:
  • Origin: Clavicle and scapula
  • Insertion: Deltoid tuberosity of humerus
  • Action: Abducts, flexes, and extends arm
  • Innervation: Axillary nerve
• Pectoralis Major:
  • Origin: Clavicle, sternum, and costal cartilages of ribs 1-6
  • Insertion: Intertubercular groove of humerus
  • Action: Adducts, flexes, and medially rotates arm
  • Innervation: Pectoral nerves
• Latissimus Dorsi:
  • Origin: Spinous processes of thoracic and lumbar vertebrae, iliac crest, ribs 9-12
  • Insertion: Intertubercular groove of humerus
  • Action: Adducts, extends, and medially rotates arm
  • Innervation: Thoracodorsal nerve
• Rotator Cuff Muscles (Supraspinatus, Infraspinatus, Teres Minor, Subscapularis):
  • Origin: Scapula
  • Insertion: Greater and lesser tubercles of humerus
  • Action: Stabilize shoulder joint, rotate arm
  • Innervation: Suprascapular nerve, Axillary nerve, Subscapular nerves

Arm Muscles

These muscles flex and extend the elbow joint.

• Biceps Brachii:
  • Origin: Scapula (two heads)
  • Insertion: Radial tuberosity
  • Action: Flexes elbow, supinates forearm
  • Innervation: Musculocutaneous nerve
• Brachialis:
  • Origin: Humerus
  • Insertion: Ulna
  • Action: Flexes elbow
  • Innervation: Musculocutaneous nerve
• Triceps Brachii:
  • Origin: Scapula and humerus (three heads)
  • Insertion: Olecranon process of ulna
  • Action: Extends elbow
  • Innervation: Radial nerve

Forearm Muscles

These muscles control movements of the wrist, hand, and fingers. They are often divided into anterior (flexor) and posterior (extensor) compartments.

• Anterior Compartment (Examples):
  • Flexor Carpi Radialis: Flexes and abducts wrist (Median nerve)
  • Flexor Carpi Ulnaris: Flexes and adducts wrist (Ulnar nerve)
  • Palmaris Longus: Flexes wrist (Median nerve)
  • Pronator Teres: Pronates forearm (Median nerve)
• Posterior Compartment (Examples):
  • Extensor Carpi Radialis Longus: Extends and abducts wrist (Radial nerve)
  • Extensor Carpi Ulnaris: Extends and adducts wrist (Radial nerve)
  • Extensor Digitorum: Extends fingers (Radial nerve)
  • Supinator: Supinates forearm (Radial nerve)

Hand Muscles

These intrinsic muscles control fine movements of the fingers and thumb.

• Thenar Muscles (Thumb):
  • Abductor Pollicis Brevis, Flexor Pollicis Brevis, Opponens Pollicis, Adductor Pollicis
  • Action: Control thumb movements (abduction, flexion, opposition, adduction)
  • Innervation: Median and Ulnar nerves
• Hypothenar Muscles (Little Finger):
  • Abductor Digiti Minimi, Flexor Digiti Minimi Brevis, Opponens Digiti Minimi
  • Action: Control little finger movements
  • Innervation: Ulnar nerve
• Midpalmar Muscles (Lumbricals, Interossei):
  • Action: Flex MCP joints, extend PIP and DIP joints (Lumbricals); abduct and adduct fingers (Interossei)
  • Innervation: Median and Ulnar nerves

Lower Limb Muscles

The lower limb muscles support the body's weight, enable locomotion, and maintain balance. Table 10.2 typically categorizes these muscles into groups such as hip muscles, thigh muscles, leg muscles, and foot muscles.

Hip Muscles

These muscles control movements of the hip joint.

• Gluteus Maximus:
  • Origin: Ilium, sacrum, coccyx
  • Insertion: Gluteal tuberosity of femur
  • Action: Extends and laterally rotates hip
  • Innervation: Inferior gluteal nerve
• Gluteus Medius:
  • Origin: Ilium
  • Insertion: Greater trochanter of femur
  • Action: Abducts hip, medially rotates hip
  • Innervation: Superior gluteal nerve
• Gluteus Minimus:
  • Origin: Ilium
  • Insertion: Greater trochanter of femur
  • Action: Abducts hip, medially rotates hip
  • Innervation: Superior gluteal nerve
• Deep Hip Rotators (Piriformis, Obturator Internus, Obturator Externus, Quadratus Femoris, Gemellus Superior, Gemellus Inferior):
  • Origin: Pelvis
  • Insertion: Greater trochanter of femur
  • Action: Laterally rotate hip
  • Innervation: Nerves to specific muscles

Thigh Muscles

These muscles flex and extend the knee joint, as well as adduct, abduct, and rotate the hip.

• Anterior Compartment (Quadriceps Femoris: Rectus Femoris, Vastus Lateralis, Vastus Medialis, Vastus Intermedius):
  • Origin: Ilium and femur
  • Insertion: Tibial tuberosity via patellar tendon
  • Action: Extends knee, flexes hip (Rectus Femoris only)
  • Innervation: Femoral nerve
• Medial Compartment (Adductors: Adductor Longus, Adductor Magnus, Adductor Brevis, Gracilis):
  • Origin: Pubis and ischium
  • Insertion: Femur
  • Action: Adducts hip, flexes and medially rotates hip
  • Innervation: Obturator nerve
• Posterior Compartment (Hamstrings: Biceps Femoris, Semitendinosus, Semimembranosus):
  • Origin: Ischial tuberosity
  • Insertion: Tibia and fibula
  • Action: Flexes knee, extends hip
  • Innervation: Sciatic nerve

Leg Muscles

These muscles control movements of the ankle, foot, and toes. They are often divided into anterior (dorsiflexor), lateral (eversion), and posterior (plantarflexor) compartments.

• Anterior Compartment (Examples):
  • Tibialis Anterior: Dorsiflexes and inverts foot (Deep fibular nerve)
  • Extensor Hallucis Longus: Extends great toe, dorsiflexes foot (Deep fibular nerve)
  • Extensor Digitorum Longus: Extends toes, dorsiflexes foot (Deep fibular nerve)
• Lateral Compartment (Examples):
  • Fibularis (Peroneus) Longus: Everts and plantarflexes foot (Superficial fibular nerve)
  • Fibularis (Peroneus) Brevis: Everts and plantarflexes foot (Superficial fibular nerve)
• Posterior Compartment (Examples):
  • Gastrocnemius: Plantarflexes foot, flexes knee (Tibial nerve)
  • Soleus: Plantarflexes foot (Tibial nerve)
  • Tibialis Posterior: Plantarflexes and inverts foot (Tibial nerve)
  • Flexor Digitorum Longus: Flexes toes, plantarflexes foot (Tibial nerve)
  • Flexor Hallucis Longus: Flexes great toe, plantarflexes foot (Tibial nerve)

Foot Muscles

These intrinsic muscles control fine movements of the toes and support the arches of the foot.

• Dorsal Muscles (Example):
  • Extensor Digitorum Brevis: Extends toes (Deep fibular nerve)
• Plantar Muscles (Layers):
  • Complex arrangement of muscles that control toe movements and support the foot arches (Medial and Lateral plantar nerves)

Applying Table 10.2 in Practice

Table 10.2 and similar muscle inventories are invaluable tools in various fields. Here are some practical applications:

• Diagnosing Muscle Injuries: If a patient presents with weakness in a specific movement, the table can help identify the muscles responsible and guide diagnostic testing.
• Designing Exercise Programs: Physical therapists and athletic trainers use the inventory to select exercises that target specific muscles for strengthening or rehabilitation.
• Understanding Biomechanics: Researchers use the information to model and analyze human movement, optimizing performance and preventing injuries.
• Medical Education: Students use the table as a study aid to learn the complexities of the muscular system.

Conclusion

Understanding the model inventory for skeletal muscles, as exemplified by Table 10.2, is fundamental to comprehending human movement, diagnosing musculoskeletal conditions, and developing effective treatment and training strategies. This comprehensive knowledge base empowers professionals and students alike to navigate the intricate world of human anatomy and physiology. By systematically studying the names, origins, insertions, actions, and innervations of each muscle, we gain a deeper appreciation for the remarkable capabilities of the human body.