17

Muscle Identification, Origin, Insertion, and Action

Groups 7-12

Topic # 17
Chapter 11

Muscle Group #7: Muscles of Abdominal Wall

  • Muscles:
      - External Oblique
      - Internal Oblique
      - Transversus Abdominis
      - Rectus Abdominis

  • Fiber Direction and Layers:
      - External Oblique
          - Fiber Direction: Anteroinferior (Superficial - 1)
      - Internal Oblique
          - Fiber Direction: Anterosuperior (Middle - 2)
      - Transversus Abdominis
          - Fiber Direction: Horizontal (Deep - 3)
      - Rectus Abdominis
          - Fiber Direction: Vertical (Middle - 2)

  • Functional Overview:
      - Four paired and layered muscles constitute the abdominal wall.
      - Anterior and lateral abdominal wall consists of three layers of muscle fibers oriented in varying directions, enhancing strength like plywood.
      - From superficial to deep:
        - External Oblique
        - Internal Oblique
        - Transversus Abdominis
      - These three muscles conclude in a sheet-like tendon (aponeurosis) encompassing the Rectus Abdominis.
      - The Rectus Abdominis stretches vertically from the pubic symphysis to costal cartilages, instrumental in flexion of the vertebral column. This muscle contributes to the aesthetic appearance of the abdominal "six-pack".

  • Functions:
      - All four muscles compress the abdomen, vital for various physiological activities including:
        - Squeezing abdominal contents
        - Counteracting diaphragm's action
        - Facilitating forceful exhalation
        - Promoting urination, defecation, childbirth, coughing, laughing, burping, screaming, sneezing, and nose blowing.

Muscle Origin, Insertion, Action (OIA)

  • External Oblique:
      - Origin (O): Ribs 5-12, inguinal ligament, lumbar fascia, and iliac crest.
      - Insertion (I): Various sites inserting with aponeuroses at linea alba.
      - Action (A): Compression of abdominal wall, supporting it, assisting forced respiration, elevating intra-abdominal pressure.
      - Role in flexion and lateral flexion of the vertebral column.

  • Rectus Abdominis:
      - Origin (O): Pubic crest and pubic symphysis.
      - Insertion (I): Costal cartilages of ribs 5-7 and xiphoid process.
      - Action (A): Flexion of the vertebral column and compression of the abdominal wall.

Layers of Abdominal Wall

  1. External Oblique – Superficial Layer
  2. Internal Oblique – Middle Layer
  3. Transversus Abdominis – Deep Layer
Note on Fiber Direction for Identification
  • Recognition of muscle fiber direction aids in identification.

Muscles of Respiration

Muscle Group #8

  • Diaphragm:
      - Muscle separating thoracic and abdominal cavities.
      - Significant increase in thoracic cavity volume during inhalation.
      - Inhalation: Active process requiring energy expenditure.
      - Exhalation: Typically passive, requiring no muscle contraction—merely muscle relaxation.
  • External Intercostals:
      - Increases the thoracic cavity horizontally during inhalation.
  • Internal Intercostals:
      - Key role in forced exhalation (coughing, sneezing) and reducing thoracic cavity size.
Muscles Action Overview
  • Diaphragm: Increases thorax volume.
  • External Intercostals: Increases thorax volume.
  • Internal Intercostals: Decreases thorax volume.

Diaphragm Details

  • Description: Broad, thin muscle across the thoracoabdominal cavity, crucial for breathing.
  • Origin (O): Vertebral column (lumbar), ribs, xiphoid process.
  • Insertion (I): Central tendon.
  • Action (A): Increases size of thoracic cavity; naturally dome-shaped, flat during contraction for inhalation.

Intercostal Muscles

External & Internal Intercostals

  • External Intercostals:
      - Origin (O): Inferior border of rib above.
      - Insertion (I): Superior border of rib below.
      - Action (A): Elevates ribs, aiding in inspiration by increasing thoracic cavity size.

  • Internal Intercostals:
      - Origin (O): Superior border of rib below.
      - Insertion (I): Inferior border of rib above.
      - Action (A): Decreases thorax volume, necessary for forced exhalation.

Muscle Group #9: Muscles Moving Hip Joint (Femur)

  • Overview: Shorter muscles of the hip, crossing only the hip joint.
  • Actions at the hip joint: Flexion, Extension, Abduction, Adduction, Medial Rotation, Lateral Rotation (similar range of motion to shoulder due to ball-and-socket joint).
  • Muscles:
      - Psoas Major
      - Iliacus
      - Gluteus Maximus
      - Gluteus Medius
      - Tensor Fasciae Latae
      - Adductor group (Longus, Brevis, Magnus)
Actions Overview
  • Key Actions: Flexion and Extension at the hip, with associated actions listed.

Iliopsoas Group

  • Psoas Major:
      - Origin (O): Transverse processes and bodies of lumbar vertebrae.
      - Insertion (I): Lesser trochanter of femur.
      - Action (A): Flexion and lateral rotation of hip.

  • Iliacus:
      - Origin (O): Iliac fossa.
      - Insertion (I): Lesser trochanter of femur.
      - Action (A): Flexion and lateral rotation of hip.

Note: "Filet Mignon" is a reference made regarding muscle naming or local dialect.

Gluteus Maximus

  • Origin (O): Iliac crest, sacrum, coccyx.
  • Insertion (I): Posterior femur & fascia lata.
  • Action (A): Extends and laterally rotates hip.
  • Fascia Lata: Deep fascia of thigh, enclosing thigh muscles, attached to various bony landmarks including the sacrum and coccyx.
Iliotibial Tract
  • Thickened lateral portion of fascia lata known as the Iliotibial band (IT Band).

Gluteus Medius

  • Origin (O): Ilium.
  • Insertion (I): Greater trochanter of femur.
  • Action (A): Abduction and medial rotation of hip; largely covered by gluteus maximus.

Tensor Fascia Latae

  • Origin (O): Iliac Crest.
  • Insertion (I): Iliotibial tract to tibia.
  • Action (A): Flexion and abduction at hip; enhances steadiness of trunk on thigh by tensing iliotibial tract.

Adductors of the Hip (Brevis, Longus, Magnus)

  • Origin (O): Inferior ramus, ischiopubic ramus, posterior surface of ischial tuberosity and body of pubis.
  • Insertion (I): Linea aspera.
  • Action (A): Adduction, medial rotation, lateral rotation. Identification as adductors collectively, rather than individually.

Muscle Group #10: Muscles that Move Knee Joint Only

  • Knee Joint Characteristics: Hinge joint, allowing only flexion and extension.
  • Key Muscles:
      - Vastus Lateralis
      - Vastus Medialis
      - Vastus Intermedius
      - Rectus Femoris (crosses hip and knee).
  • Function: Quadriceps group serves to climb, run, jump, rise from sitting, noteworthy for their strength.
Actions Overview
  • Insertion (I): All quadriceps converge into a common tendon inserting at patella and extend to tibial tuberosity.
  • Action (A): Extension at knee.

Quadriceps Femoris Details

  • Common Insertions Action:
      - Patella to tibial tuberosity (common function).
  • Vastus Lateralis:
      - Origin (O): Greater trochanter, linea aspera.
  • Vastus Medialis:
      - Origin (O): Linea aspera.
  • Vastus Intermedius:
      - Origin (O): Anterior and lateral surface of femur.
  • Rectus Femoris:
      - Origin (O): Anterior inferior iliac spine. Additional function: Flexion at hip due to crossing hip joint.

Muscle Group #11: Muscles Moving Both Hip and Knee Joints

  • Functional Overview: Actions involve adduction, abduction, flexion, and extension at the hip; flexion and extension at the knee.
  • Primary Group: Hamstrings (biceps femoris, semitendinosus, semimembranosus)
      - Prime movers in hip extension and knee flexion.
  • Muscles Origin: Common origin on ischial tuberosity for all three.
Actions Overview
  • Common action: Extension at hip, flexion at the knee.

Hamstring Group Details

  • Biceps Femoris:
      - Insertion (I): Head of fibula, lateral condyle of tibia.
  • Semitendinosus:
      - Insertion (I): Upper medial surface of tibia.
  • Semimembranosus:
      - Insertion (I): Medial condyle of tibia.

Muscle Group #12: Muscles that Move Foot and Toes

  • Ankle Actions: Dorsiflexion, plantarflexion, inversion, eversion.
  • Toe Actions: Flexion, extension.
  • Dorsiflexors: Only three muscles anterior to the ankle joint.
  • Plantar Flexors: Majority support body weight, provide thrust in walking and running.
Key Muscles Overview
  • Muscle Actions at Ankle and Toes:
  • Gastrocnemius: Plantar flexion.
  • Soleus: Plantar flexion.
  • Tibialis Posterior: Plantarflexion and inversion.
  • Flexor Hallucis Longus: Flexion at big toe, plantarflexion at ankle.
  • Tibialis Anterior: Dorsiflexion and inversion.
  • Extensor variations extending to individual digits.

Muscle Insertion Details

  • Gastrocnemius:
      - Origin (O): Condyles of femur.
      - Insertion (I): Achilles tendon to calcaneus.
      - Action (A): Primary mover of plantarflexion.

  • Soleus:
      - Origin (O): Posterior tibia and fibula.
      - Insertion (I): Achilles tendon to calcaneus.

Common Tendon Insertion Information
  • Achilles Tendon: Standout feature of gastrocnemius and soleus, noted as strongest tendon in the body and commonly ruptured in individuals over 40.

Tibialis Posterior

  • Origin (O): Posterior shaft of tibia and upper half of fibula.
  • Insertion (I): Tuberosity of navicular bone; affects all three cuneiforms.
  • Action (A): Plantarflexion and inversion at ankle.

Extensor Muscles Overview

  • Tibialis Anterior:
      - Origin (O): Upper lateral tibia.
      - Insertion (I): Underside of 1st cuneiform and 1st metatarsal.
      - Action (A): Dorsiflexion and inversion at ankle.

Conclusion: General Rules Learning Actions

  • Flexion: Caused by muscles crossing joints anteriorly (exception noted for knee).
  • Extension: Caused by posterior crossing muscles (knee exceptions noted).
  • Dorsiflexion: Caused by anterior joint crossing muscle activity.
  • Plantarflexion: Caused by posterior activity at the ankle.
  • Adduction: Caused by muscles medial to the moved bone.
  • Abduction: Caused by muscles lateral to the moved bone.
Additional Note
  • Reminder to review lecture notes, outline, and focus questions for better preparation for next session.