Human Anatomy - Zynoviy Myrchuk, Maryna Myrchuk 2007

Muscles of the Body Regions
Muscles of the Lower Limb

Just as in the upper limb, the Muscles of the Lower Limb are divided into the Pelvic Girdle muscles and the free lower limb muscles (Figs. 49, 50)—those of the thigh, leg, and FOOT. The pelvic girdle muscles are categorized into internal and external groups. The internal muscles include the iliopsoas, internal obturator, and piriformis, which attach to the Femur and perform various movements at the hip joint. The largest of these is the iliopsoas, which originates from the bodies and transverse processes of the 12th thoracic and 1st–5th lumbar vertebrae and inserts into the lesser trochanter of the femur. Its primary function is flexion of the thigh at the hip joint.

The external Muscle group comprises the gluteus maximus, gluteus medius, gluteus minimus, quadratus femoris, and obturator externus. The gluteal muscles originate from the ilium and insert into the femur. When contracting, they extend the thigh; with a fixed lower limb, they maintain the pelvis and trunk in an upright position, and they also abduct the thigh. The gluteus maximus is the strongest of these, standing out prominently due to its large mass.

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Fig. 49. G. Bammes. Muscles of the lower limb:

1 - gluteus medius; 2 - tensor fasciae latae;

3 - fascia lata; 4 - quadriceps femoris;

5 - biceps femoris; 6 - tendon of biceps femoris;

7 - triceps surae; 8 - soleus;

9 - peroneus longus (fibularis longus); 10 - calcaneal (Achilles) tendon;

11 - peroneus brevis (fibularis brevis); 12 - sartorius;

13 - semimembranosus; 14 - gracilis;

15 - semimembranosus; 16 - semitendinosus;

17 - adductor magnus; 18 - gluteus maximus;

19 - tibialis anterior;

20 - extensor digitorum longus.

Thigh muscles. The intrinsic muscles of the thigh are divided into three groups: anterior (flexors), medial (adductors), and posterior (extensors), which surround the femur on all sides.

The anterior group is represented by the sartorius and the quadriceps femoris. The sartorius is the longest muscle in The Human Body. It originates from the ilium, crosses the entire anterior surface of the thigh from top to bottom and medially, and inserts into the Tibia. The quadriceps femoris, which has the largest mass of all muscles, originates with one HEAD from the ilium and three heads from the femur, inserting via a common tendon into the tibial tuberosity. Upon contraction, these muscles flex the thigh at the hip joint and extend the leg at the knee joint. When the thigh is flexed, it rotates outward, while the leg rotates inward.

The medial group includes the pectineus, gracilis, and adductor muscles (adductor longus, adductor brevis, adductor magnus). When contracting, they adduct the thigh and flex the leg at the knee joint. These muscles originate on the external surfaces of the ischium and pubis and insert into the linea aspera of the femur.

The posterior group of thigh muscles consists of the semitendinosus, semimembranosus, and biceps femoris. Upon contraction, they flex the leg at the knee joint, extend the thigh, and—when the leg is flexed at the knee—rotate it inward or outward.

All thigh muscles are encased on all sides by the fascia lata, resembling a tight sheath. Superiorly, it attaches to the inguinal ligament, iliac crest, Pubic Symphysis, and ischium. In the upper third of the anterior thigh, the fascia consists of superficial and deep layers. Just below the inguinal ligament, the superficial layer features an oval-shaped opening—the saphenous opening (hiatus saphenus). Deep within this opening runs the great saphenous vein, which empties into the femoral vein. Inferiorly, the fascia lata covers the knee joint anteriorly and laterally, continuing into the crural fascia (Fascia of the leg).

Fig. 50. G. Bammes. Muscles of the lower limb:

1 - iliopsoas; 2 - pectineus; 3 - adductor longus; 4 - gracilis; 5 - triceps surae; 6 - soleus; 7 - abductor hallucis; 8 — tibialis anterior; 9 - quadriceps femoris; 10 - sartorius; 11- tensor fasciae latae; 12 - fascia lata; 13 — extensor digitorum longus; 14 - extensor hallucis longus; 15 - flexor digitorum longus; 16 - peroneus longus (fibularis longus).

Fig. 51. Plastic Anatomy of the leg muscles

The muscles of the lower leg are divided into three groups: anterior, lateral, and posterior. They surround the BONES OF THE lower leg. The muscles of the anterior group extend the foot and toes, while the muscles of the lateral group raise the lateral margin and lower the medial margin of the foot. The largest muscle is the triceps surae. It originates with two heads from the lateral and medial condyles of the femur. This part of the triceps muscle is called the gastrocnemius. In the middle of the lower leg, both heads of the gastrocnemius transition into a thick common tendon that narrows downwards and merges with the tendon of the soleus muscle, forming the calcaneal (Achilles) tendon, which attaches to the calcaneal tuberosity. The triceps muscle flexes the lower leg and the foot.

Fig. 52. G. Bammes. Muscles of the foot

The muscles of the foot (Fig. 52) are located on the dorsum of the foot and the sole. The muscles of the dorsal foot are represented by the extensor digitorum brevis and the extensor hallucis brevis. On the sole, the medial (on the side of the big toe), lateral (on the side of the little toe), and middle muscle groups are distinguished. The plantar muscles are strong and play a crucial role in maintaining the arches of the foot. Weakness in these muscles leads to flat feet.

Fig. 53. Foot sketches