Rib
Ribs are classed as flat bones which usually have a protective role in the body. Humans have 24 ribs, in 12 pairs. All are attached at the back to the thoracic vertebrae, and are numbered from 1–12 according to the vertebrae they attach to. The first rib is attached to thoracic vertebra 1 (T1). At the front of the body most of the ribs are joined by costal cartilages to the sternum. The ribs connect to the vertebrae with two joints, the costovertebral joints.
Crab louse
It has been suggested that an increasing percentage of humans removing their pubic hair has led to reduced crab louse populations in some parts of the world. Other lice that infest humans are the body louse and the head louse. The claws of these three species are adapted to attachment to specific hair diameters.
Pubic lice are not known to transmit disease. Adult pubic lice are 1.1–1.8 mm in length. The pubic hair can typically host up to a dozen on average. Pubic lice typically are found attached to hair in the pubic area but sometimes are found on coarse hair elsewhere on the body (for example, eyebrows, eyelashes, beard, mustache, chest, armpits, etc.). Crab lice attach to pubic hair that is thicker than other body hair because their claws are adapted to the specific diameter of pubic hair. Pubic lice infestations (pthiriasis) are usually spread through sexual contact. The crab louse can travel up to 10 inches on the body. Pubic lice infestation is found worldwide and occurs in all races and ethnic groups and in all economic levels. Pubic lice usually are spread through sexual contact and are most common in adults. Occasionally pubic lice may be spread by close personal contact or contact with articles such as clothing, bed linens, and towels that have been used by an infested person. Pubic lice found on the head or eyelashes of children may be an indication of sexual exposure or abuse. Pubic lice do not transmit disease; however, secondary bacterial infection can occur from scratching of the skin. They are much broader in comparison to head and body lice. Adults are found only on the human host and require human blood to survive. If adults are forced off the host, they will die within 24–48 hours without a blood feeding.