Lab 2 BIO104

Muscles of the Face, Head, and Neck

• Masseter

  • Origin: Zygomatic arch

  • Insertion: Mandibular ramus

  • Action: Closes jaw

• Temporalis

  • Origin: Temporal bone

  • Insertion: Mandible

  • Action: Closes jaw

• Sternocleidomastoid

  • Origin: Sternum & clavicle

  • Insertion: Mastoid process

  • Action: Flexes neck forward (if both contract)

Muscles of the Anterior Torso and Abdominal Wall

• Pectoralis major

  • Origin: Clavicle, sternum

  • Insertion: Greater tubercle (humerus)

  • Action: Flexion, adduction, and medial rotation of the arm

• External Intercostals

  • Origin: Lower border of each rib

  • Insertion: Upper border of the next rib

  • Action: Elevate the ribcage; used in inspiration

• Internal Intercostals

  • Origin: Upper border of the rib below

  • Insertion: Lower border of the rib above

  • Action: Depress the ribcage; used in expiration

• Rectus abdominis

  • Origin: Pubic symphysis

  • Insertion: Xiphoid process and the $5^{th}-7^{th}$ costal cartilages

  • Action: Flexes the vertebral column and provides abdominal compression

• External oblique

  • Origin: Lower $8$ ribs

  • Insertion: Linea alba and the iliac crest

  • Action: Flexes the vertebral column, provides abdominal compression, and assists in lateral flexion

Muscles of the Posterior Torso, Shoulders, and Back

• Deltoid

  • Origin: Acromion and spine of the scapula, along with the clavicle

  • Insertion: Deltoid tuberosity (humerus)

  • Action: Abducts the arm

• Trapezius

  • Origin: Occipital bone and the spines of the thoracic vertebrae

  • Insertion: Clavicle, spine of the scapula, and acromion of the scapula

  • Action: Extends the head; also adducts, elevates, or depresses the scapula

• Latissimus dorsi

  • Origin: Lower thoracic and lumbar vertebrae

  • Insertion: Humerus

  • Action: Extension, adduction, and medial rotation of the humerus

• Teres major

  • Origin: Inferior angle of the scapula

  • Insertion: Intertubercular groove (humerus)

  • Action: Medially rotates and adducts the humerus

• Rhomboids (Major and Minor)

  • Origin: Spinous processes of the upper thoracic vertebrae

  • Insertion: Vertebral border of the scapula

  • Action: Adducts and rotates the scapula

Muscles of the Upper Limb

• Biceps brachii

  • Origin:

    • Short head: Coracoid process (scapula)

    • Long head: Tubercle above the glenoid cavity

  • Insertion: Radial tuberosity

  • Action: Flexion of the forearm

• Triceps brachii

  • Origin:

    • Long head: Glenoid cavity

    • Lateral head: Humerus (posterior)

    • Medial head: Humerus

  • Insertion: Ulna (olecranon process)

  • Action: Extension of the forearm

Muscles of the Lower Limb

• Gluteus maximus

  • Origin: Ilium, sacrum, and coccyx

  • Insertion: Fascia lata (iliotibial tract)

  • Action: Extension of the hip (e.g., utilized when climbing stairs)

• Sartorius

  • Origin: ASIS (Anterior Superior Iliac Spine)

  • Insertion: Medial aspect of the proximal tibia

  • Action: Flexes the leg and laterally rotates the thigh

• Quadriceps femoris (Rectus femoris, Vastus intermedius, Vastus lateralis, Vastus medialis)

  • Origin: Arises by $4$ heads from the ilium and the femur

  • Insertion: Tibial tuberosity

  • Action: Leg extension and flexion of the thigh

• Biceps femoris

  • Origin: Ischial tuberosity and the linea aspera (femur)

  • Insertion: Fibula and tibia

  • Action: Flexes the leg; also extends and adducts the thigh

• Gastrocnemius

  • Origin: Condyles of the femur

  • Insertion: Calcaneus via the calcaneal tendon

  • Action: Plantar flexion