Sesamoid bone in the context of "Long bones"

The red panda (Ailurus fulgens), also known as the lesser panda, is a small mammal native to the eastern Himalayas and southwestern China. It has dense reddish-brown fur with a black belly and legs, white-lined ears, a mostly white muzzle and a ringed tail. Its head-to-body length is 51–63.5 cm (20.1–25.0 in) with a 28–48.5 cm (11.0–19.1 in) tail, and it weighs between 3.2 and 15 kg (7.1 and 33.1 lb). It is well adapted to climbing due to its flexible joints and curved semi-retractile claws.

The red panda was formally described in 1825. The two recognised subspecies, the Himalayan and the Chinese red panda, genetically diverged about 250,000 years ago. The red panda's place on the evolutionary tree has been debated, but modern genetic evidence places it in close affinity with raccoons, weasels, and skunks. It is not closely related to the giant panda, which is a bear, though both possess elongated wrist bones or "false thumbs" used for grasping bamboo. The evolutionary lineage of the red panda (Ailuridae) stretches back around 25 to 18 million years ago, as indicated by extinct fossil relatives found in Eurasia and North America.

The irregular bones are bones which, from their peculiar form, cannot be grouped as long, short, flat or sesamoid bones. Irregular bones serve various purposes in the body, such as protection of nervous tissue (such as the vertebrae protect the spinal cord), affording multiple anchor points for skeletal muscle attachment (as with the sacrum), and maintaining pharynx and trachea support, and tongue attachment (such as the hyoid bone). They consist of cancellous tissue enclosed within a thin layer of compact bone. Irregular bones can also be used for joining all parts of the spinal column together. The spine is the place in the human body where the most irregular bones can be found. There are, in all, 33 irregular bones found here.

The irregular bones are: the vertebrae, sacrum, coccyx, temporal, sphenoid, ethmoid, zygomatic, maxilla, mandible, palatine, inferior nasal concha, and hyoid.

The long bones are those that are longer than they are wide. They are one of five types of bones: long, short, flat, irregular and sesamoid. Long bones, especially the femur and tibia, are subjected to most of the load during daily activities and they are crucial for skeletal mobility. They grow primarily by elongation of the diaphysis, with an epiphysis at each end of the growing bone. The ends of epiphyses are covered with hyaline cartilage ("articular cartilage"). The longitudinal growth of long bones is a result of endochondral ossification at the epiphyseal plate. Bone growth in length is stimulated by the production of growth hormone (GH), a secretion of the anterior lobe of the pituitary gland.

The long bone category includes the femora, tibiae, and fibulae of the legs; the humeri, radii, and ulnae of the arms; metacarpals and metatarsals of the hands and feet, the phalanges of the fingers and toes, and the clavicles or collar bones. The long bones of the human leg make up nearly half of adult height. The other primary skeletal component of height are the vertebrae and skull.

The patella (pl.: patellae or patellas), also known as the kneecap, is a flat, rounded triangular bone which articulates with the femur (thigh bone) and covers and protects the anterior articular surface of the knee joint. The patella is found in many tetrapods, such as mice, cats, birds, and dogs, but not in whales, or most reptiles.

In humans, the patella is the largest sesamoid bone (i.e., embedded within a tendon or a muscle) in the body. Babies are born with a patella of soft cartilage which begins to ossify into bone at about four years of age.