Summary
Highlights
The right leg is divided into three compartments: anterior, lateral, and posterior (with deep and superficial planes). The anterior compartment includes muscles like the extensor hallucis longus, tibialis anterior, and extensor digitorum longus, primarily involved in toe and foot extension/dorsiflexion. The lateral compartment contains the fibularis brevis and longus, which support the arch of the foot. The deep posterior compartment features the flexor hallucis longus, tibialis posterior, flexor digitorum longus, and popliteus, responsible for toe flexion, foot inversion, and initial knee flexion. The superficial posterior compartment, known as the triceps surae (calf muscle), consists of the soleus and two gastrocnemius muscles, facilitating plantar flexion and ankle extension.
The thigh muscles are organized into anterior, medial, and posterior compartments. The anterior compartment houses the quadriceps and sartorius. The quadriceps, composed of four heads (vastus intermedius, vastus lateralis, vastus medialis, and rectus femoris), is a primary knee extensor, with the rectus femoris also acting as a hip flexor. The sartorius is a hip flexor and aids in external rotation. The tensor fasciae lata stabilizes the hip. The medial compartment contains five adductor muscles (pectineus, adductor brevis, adductor longus, adductor magnus, and gracilis) responsible for hip adduction. The posterior compartment includes the hamstrings (biceps femoris, semimembranosus, and semitendinosus), which flex the knee and extend the hip, with specific muscles also involved in internal and external rotation of the knee.
The hip region includes six deep inner muscles (quadratus femoris, obturator externus, obturator internus, piriformis, gemelli superior, gemelli inferior) that reinforce the hip joint and contribute to external rotation of the femur. Additionally, there are three gluteal muscles: the gluteus minimus (a hip flexor), the gluteus medius (the main hip abductor and pelvis stabilizer), and the gluteus maximus (a hip extensor and external rotator of the thigh). The tensor fasciae lata also acts as a hip flexor.
The iliopsoas muscle, comprising the iliacus and psoas major, is the primary hip flexor. The perineum forms the pelvic floor, supporting viscera and aiding in micturition, defecation, and sexual intercourse. The diaphragm is a crucial muscle for breathing, separating the rib cage from the abdomen and contracting during inhalation. Intercostal muscles between the ribs assist in breathing and resist intrathoracic pressure.
The anterior trunk features five abdominal muscles: the quadratus lumborum (stabilizes the trunk), the transverse abdominis (contracts during drawing in the abdomen, aiding respiration), the rectus abdominis (flexes the trunk), and the internal and external obliques (rotate and incline the trunk). The posterior trunk muscles include the multifidus, longissimus, and iliocostalis, collectively known as spinal erector muscles, which extend the trunk and contribute to height.
The upper limb muscles are divided into anterior, posterior, and lateral groups. The deep anterior plane includes the serratus anterior (stabilizes the scapula, boxer's muscle), subclavius (lowers clavicle, raises first rib), and pectoralis minor (tilts scapula, lifts ribs). The superficial anterior plane has the pectoralis major, performing adduction, medial rotation, and antipulsion of the arm. The 10 posterior muscles include the rotator cuff (subscapularis, supraspinatus, infraspinatus, teres minor) which reinforce and stabilize the shoulder joint, along with the levator scapulae, rhomboid minor, rhomboid major, trapezius, teres major, and latissimus dorsi, performing various actions like scapula elevation, rotation, adduction, and shoulder movements.
The upper arm has anterior and posterior compartments. The anterior compartment contains the brachialis (elbow flexion) and the biceps brachii (elbow flexion and supination). The posterior compartment houses the triceps brachii, composed of three heads (medial, lateral, and long), which is the main extensor of the arm, enabling elbow extension.
The forearm muscles are divided into three compartments: the anterior compartment containing flexor muscles of the wrist and fingers, the lateral compartment housing extensor and supinator muscles, and the posterior compartment consisting of wrist and finger extensor muscles.
Key neck muscles discussed are the sternocleidomastoid and the scalene muscles. These muscles are responsible for movements such as rotation, extension, and tilting of the head.