Question

What are limbs? What are their functions?

Answer 1

Limb creation occurs in the morphogenetic limb field, when lateral plate mesoderm mesenchymal cells proliferate to the point where the ectoderm above bulges out, generating a limb bud. The apical ectodermal ridge (AER), which regulates subsequent development and controls cell death, is formed when fibroblast growth factor (FGF) is induced at the end of the limb bud. To reduce webbing between digits, programmed cell death is required. Retinoic acid signalling in the developing trunk of the embryo, from which the limb buds originate, is required for the establishment of the forelimb field.

Complete answer:
Part A: A limb, often known as an extremity, is a jointed or prehensile appendage of the human or other animal body. The upper and lower limbs of the human body, which include parts of the shoulder and hip girdles, are frequently referred to as upper and lower limbs, respectively. The torso or trunk connects the arms and legs.
Many animals utilise their limbs to move around, such as walking, running, climbing, or swimming. Some animals can carry and operate objects with their forelimbs (which are similar to arms in humans), while others can fly with them. Some animals can also manipulate their environment with their hind limbs.
Most other mammals walk and run on all four limbs, however human legs and feet are designed for two-legged mobility. Human arms are weaker but more mobile, allowing them to span a wide range of distances and angles before terminating in specialised hands capable of grabbing and precision item manipulation. Grasping behaviour is common among tetrapods, despite the fact that human dexterity is somewhat unusual.
Part B: Humans use their forelimbs (upper limbs) for gripping, holding, writing, and eating, while their hind limbs (lower limbs) are employed for running, walking, and other activities. Animals, too, use their limbs for climbing, feeding, walking, running, and jumping.

Note:
The upper limb, which is divided into the arm between shoulder and elbow, the forearm between elbow and wrist, and the hand below the wrist, and the lower limb, which is divided into the thigh between hip and knee, the leg between knee and ankle, and the foot below the ankle, are referred to as 'the limbs'.
Hox genes are in charge of limb development. So far, all jawed vertebrates studied have organised their growing limb buds in the same way. The limb grows from the proximal to the distal end. An apical ectodermal ridge on the distal end is where skeletal elements are differentiated.