Pavel Novotny

What constitutes a hand?

Many mammals and other animals have grasping appendages similar in form to a hand such as paws, claws, and talons, but these are not scientifically considered to be hands. The scientific use of the term hand to distinguish the terminations of the front paws from the hind ones is an example of anthropomorphism. The only true hands appear in the mammalian order of primates. Hands must also have opposable thumbs, as described later in the text.

Humans have only two hands (except in cases of polymelia), which are attached to the arms. Apes and monkeys are sometimes described as having four hands, because the toes are long and the hallux is opposable and looks more like a thumb, thus enabling the feet to be used as hands. Also, some apes have toes that are longer than human fingers.

In vertebrates such as mammals the abdomen (belly) constitutes the part of the body between the thorax (chest) and pelvis. The region enclosed by the abdomen is termed the abdominal cavity. In arthropods it is the most distal section of the body which lies behind the thorax or cephalothorax.

Abdominal organs
Digestive tract: Stomach, small intestine, large intestine with cecum and appendix
Accessory organs of the digestive tract: Liver, gallbladder and pancreas
Urinary system: Kidneys and ureters
Other organs: Spleen