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The upper limbs or upper extremities are the forelimbs of an upright-postured tetrapod vertebrate, extending from the scapulae and clavicles down to and including the digits, including all the musculatures and ligaments involved with the shoulder, elbow, wrist and knuckle joints. [1]
A forelimb or front limb is one of the paired articulated appendages attached on the cranial end of a terrestrial tetrapod vertebrate's torso. With reference to quadrupeds, the term foreleg or front leg is often used instead. In bipedal animals with an upright posture (e.g. humans and some other primates), the term upper limb is often used.
The distal half of the limb proper has two long bones, together termed the zeugopodium (plural: zeugopodia). These may be radius and ulna of the forearm, or the tibia and fibula of the shin. The distalmost portion or extremity of the limb, i.e. the hand or foot, is known as the autopodium (plural: autopodia).
This cladistic approach defines "tetrapods" as the nearest common ancestor of all living amphibians (the lissamphibians) and all living amniotes (reptiles, birds, and mammals), along with all of the descendants of that ancestor. In effect, "tetrapod" is a name reserved solely for animals which lie among living tetrapods, so-called crown tetrapods.
Polydactyly in early tetrapod aquatic animals, such as in Acanthostega gunnari (Jarvik 1952), one of an increasing number of genera of stem-tetrapods known from the Upper Devonian, which are providing insights into the appearance of tetrapods and the origin of limbs with digits. It also occurs secondarily in some later tetrapods, such as ...
The tetrapod torso — including that of a human — is usually divided into the thoracic segment (also known as the upper torso, where the forelimbs extend), the abdominal segment (also known as the "mid-section" or "midriff"), and the pelvic and perineal segments (sometimes known together with the abdomen as the lower torso, where the ...
There are 126 bones in the human appendicular skeleton, includes the skeletal elements within the shoulder and pelvic girdles, upper and lower limbs, and hands and feet. [1] These bones have shared ancestry (are homologous) to those in the forelimbs and hindlimbs of all other tetrapods, which are in turn homologous to the pectoral and pelvic ...
The pectoral girdles are to the upper limbs as the pelvic girdle is to the lower limbs; the girdles are the part of the appendicular skeleton that anchor the appendages to the axial skeleton. In humans, the only true anatomical joints between the shoulder girdle and the axial skeleton are the sternoclavicular joints on each side.