The GLUTEALS (MAXIMUS, MINIMUS, and MEDIUS) are the large muscles of the buttocks, which extend and laterally rotate the thigh, as well as abduct and medially rotate it. They arise from the ilium, the posterior surface of the lower sacrum, and the side of the coccyx. Their points of insertion include the greater trochanter and the gluteal tuberosity of the femur. The gluteus maximus is the site of choice for massive intramuscular injections.
The QUADRICEPS is a group of four muscles that make up the anterior portion of the thigh. The rectus femoris originates at the ilium; the vastus femoris, v. lateralis, and v. intermedius originate along the femur. All four are inserted into the tuberosity of the tibia through a tendon passing over the knee joint. The quadriceps serves as a strong extensor of the leg at the knee and flexes the thigh.
The SARTORIUS is the longest muscle in the body. It extends diagonally across the front of the thigh from its origin at the ilium, down to its insertion near the tuberosity of the tibia. Its function is to flex the thigh and rotate it laterally, and to flex the leg and rotate it slightly medially. The GRACILIS is a long slender muscle located on the inner aspect of the thigh. It adducts the thigh and flexes and medially rotates the leg. Its origin is in the symphysis pubis, and its insertion is in the medial surface of the tibia, below the condyle.
The BICEPS FEMORIS (often called the hamstring muscle) originates at the tuberosity of the ischium and the middle third of the femur. It is inserted on the head of the fibula and the lateral condyle of the tibia. It acts, along with other related muscles, to flex the leg at the knee and to extend the thigh at the hip joint.
The GASTROCNEMIUS and SOLEUS (calf muscles) extend the foot at the ankle. The gastrocnemius originates at two points on the femur; the soleus originates at the head of the fibula and the medial border of the tibia. Both are inserted in a common tendon called the calcaneus, or Achilles tendon.
The TIBIALIS ANTERIOR originates at the upper half of the tibia and inserts at the first metatarsal and cuneiform bones. It flexes the foot.
The skin, or integument, is the outer covering of the body. It consists of two layers, the epidermis and the dermis, and supporting structures and appendages (fig. 3-29).
Figure 3-29.The skin.
The skin covers almost every visible part of the human body. Even the hair and nails are outgrowths from it. It protects the underlying structures from injury, drying, and invasion by foreign organisms; it contains the peripheral endings of many sensory nerves; and it has limited excretory and absorbing powers. It also plays an important part in regulating body temperature. In addition, the skin is a waterproof covering that prevents excessive water loss, even in very dry climates. 3-18 . .