Muscular system: Part 3

Thoracic region

• Diaphragm: Primary mover for inspiration; contraction flattens it (inspiration), relaxation raises it (expiration).

• External Intercostals: Elevate ribs during inspiration.

• Internal Intercostals: Depress ribs during expiration.

Abdominal region

• Rectus Abdominis: Flexes vertebral column.

• External Oblique: Inferomedial fibers; bilateral contraction flexes spine, unilateral causes contralateral rotation.

• Internal Oblique: Superomedial fibers; similar actions to external oblique.

Pelvic region

• Pelvic Diaphragm (Levator Ani Group): Supports pelvic organs during pressure events (e.g., coughing, urination).

• Includes Pubococcygeus, Iliococcygeus, Puborectalis, and Coccygeus.

Gluteal region posterior muscles 

• Gluteus maximum: Extends femur at hip; origin: ilium, sacrum, coccyx; insertion: gluteal tuberosity, iliotibial tract.

• Gluteus medius & minimus: medial rotation at hip joint & abduction at hip joint 

Piriformis 

Lateral rotation at hip; origin: ischium; insertion: greater trochanter.

Iliopsoas 

Flexes thigh at hip; insertion: lesser trochanter.

Thigh region: Anterior 

Quadriceps Femoris Group:

• Rectus Femoris (origin: AIIS)

• Vastus Medialis, Lateralis, Intermedius

• Sartorius: Flexes hip/knee, abducts and laterally rotates hip.

Thigh region: posterior 

Hamstrings:

• Biceps Femoris: Insertion: fibula & lateral tibia.

• Semitendinosus & Semimembranosus: Insertion: medial tibia.

Thigh region: medial 

Gracilis, Pectineus, Adductor Longus/Brevis/Magnus: Adduct hip, assist in flexion.

Leg region: anterior

• Tibialis Anterior: Dorsiflexes ankle, inverts foot.

• Extensor Hallucis Longus: Extends great toe, dorsiflexes ankle.

• Extensor Digitorum Longus: Extends toes 2–5, dorsiflexes ankle.

Leg region: lateral

Fibularis (Peroneus) Longus & Brevis: Evert foot, plantarflex ankle.

Leg region: posterior

• Superficial Layer:

  • Gastrocnemius: Plantarflexion, assists knee flexion.

  • Soleus: Plantarflexion.

• Deep Layer:

  • Flexor Hallucis Longus: Flexes great toe.

  • Flexor Digitorum Longus: Flexes toes 2–5.

  • Tibialis Posterior: Inverts foot, supports medial arch.

Foot region: dorsal 

• Extensor Digitorum Brevis

• Extensor Hallucis Brevis

Muscle conditions

• Hypertrophy: Increase in muscle size.

• Atrophy: Decrease in muscle size due to disuse or disease.

Name this compartment

Anterior compartment: Quadriceps femoris & satorius

Name these parts of the quadriceps femoris 

Blue:

Yellow: 

Green:

Name this muscle 

tibialis anterior 

Name this muscle

extensor hallucis longus

Name this muscle 

Extensor digitorum longus 

Name this muscle (compartment)

Fibularis (longus and brevis)

Name this muscle 

flexor hallucis longus 

Name this muscle

flexor digitorum longus

Name this muscle

tibialis posterior