Elephants are the largest of all land mammals. Males (bulls) weigh 11,000 to 13,200 pounds and reach heights of 9 to 11 feet, while females (cows) weigh 6,600 to 9,000 pounds and reach heights over 8 feet. Their trunks, containing the nostrils, are muscular extensions of the upper lip equipped with two fingerlike projections for handling small objects. Elephants have six sets of cheek teeth, two upper and two lower, which move into place as they outgrow or wear out the previous set. The upper incisors grow continuously, creating the tusks. African elephants have four toes on each of their front feet and three toes on each of their hind feet. Their skin is gray and wrinkled with scattered bristles and sensory hairs. Their ears are large, with a network of veins and capillaries to help dissipate heat, and are, curiously, shaped very much like the continent of Africa.