N3 Anatomy and Physiology AY 2023-2024

1. Throwing a baseball overhead
   1. Pectoralis major
      • Action: As a whole, adducts and medially rotates arm at shoulder joint; clavicular head flexes arm, and sternocostal head flexes the extended arm to side of trunk.
      • Innervation: Medial and lateral pectoral nerves.
   2. Deltoid
      • Action: Lateral fibers abduct arm at shoulder joint; anterior fibers flex and medially rotate arm at shoulder joint; posterior fibers extend and laterally rotate arm at shoulder joint.
      • Innervation: Axillary nerve.
   3. Subscapularis
      • Action: Medially rotates arm at shoulder joint.
      • Innervation: Upper and lower subscapular nerve.
2. Kicking a ball
   1. Rectus femoris, Vastus lateralis, Vastus medialis, and Vastus intermedius
      • Action: All four heads extend leg at knee joint; rectus femoris muscle acting alone also flexes thigh at hip joint.
      • Innervation: Femoral nerve.
   2. Biceps femoris
      
      • Action: Extends thigh at hip joint.
      • Innervation: Tibial and fibular nerves from sciatic nerve.
   3. Semitendinosus
      
      • Action: Extends thigh at hip joint.
      • Innervation: Tibial nerve.
   4. Semimembranosus
      
      • Action: Flexes leg at knee joint and extends thigh at hip joint.
      • Innervation: Tibial nerve from sciatic nerve.
3. Doing sit-ups
   1. Rectus abdominis
      • Action: Flexes vertebral column, especially lumbar portion, and compresses abdomen to aid in defecation, urination, forced exhalation, and childbirth. RMA: Flexes pelvis on the vertebral column.
      • Innervation: Thoracic spinal nerves T7–T12.
   2. Transversus abdominis
      • Action: Compresses abdomen.
      • Innervation: Thoracic spinal nerves T8–T12,iliohypogastric nerve, and ilioinguinal nerve.
   3. Internal abdominal oblique
      • Action: Acting together, compress abdomen and flex vertebral column; acting singly, laterally flex vertebral column, especially lumbar portion, and rotate vertebral column.
      • Innervation: Thoracic spinal nerves T8–T12, the iliohypogastric nerve, and ilioinguinal nerve.
4. Breathing
   1. Diaphragm
      • Action: Contraction of diaphragm causes it to flatten and increases vertical dimension of thoracic cavity, resulting in inhalation; relaxation of diaphragm causes it to move superiorly and decreases vertical dimension of thoracic cavity, resulting in exhalation.
      • Innervation: Phrenic nerve, which contains axons from cervical spinal nerves (C3–C5).
   2. External intercostals
      • Action: Contraction elevates ribs and increases anteroposterior and lateral dimensions of thoracic cavity, resulting in inhalation; relaxation depresses ribs and decreases anteroposterior and lateral dimensions of thoracic cavity, resulting in exhalation.
      • Innervation: Thoracic spinal nerves T2–T12.
   3. Internal intercostals
      • Action: Contraction draws adjacent ribs together to further decrease anteroposterior and lateral dimensions of thoracic cavity during forced exhalation.
      • Innervation: Thoracic spinal nerves T2–T12.

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