Question

Why do legs and arms have large tube-like bones?

Answer 1

The limbs of the human beings have large tube-like bones. The hollow tubes like bones are lightweight which helps in movements. Bones make human body skeleton. Limbs help in the movement of the body. The bones contain calcium and collagen fibers which makes them stronger.

Complete answer:
The legs and arms are the limbs of the human body. They help in the movement of the body. Human beings have hollow tubes like bones in their legs and arms. These bones are needed to be strong and moveable because they are continuously required to do all the activities. The hollow bones provide free space for the blood vessels and the nerves to pass through tube-like bones.
These hollow bones are composed of a shaft (diaphysis) and two flared ends (epiphyses). Diaphysis is the mid section of the long bones. This type of structure of the limbs provides strong support to the body weight and help in rigorous activities. The long bones must be strong and lightweight. It is most important in legs, arms and wings.
The bone structure is composed of the collagen (flexible fibrous materials) and minerals (mainly calcium and phosphate). Calcium makes the bones stronger. Without calcium it becomes soft and flexible. Calcium and collagen together play a very important role in making the bones strong.

Note: Bones can repair itself when broken with the help of osteoblasts (bone forming cells) and osteoclasts (bone digesting cells). The inner cavity of diaphysis contains yellow marrow that stores fats. The longest bone in the body is the femur which is the thigh bone. The smallest and the lightest bone in the body is the stapes which is found in ears. The human wrist contains 52 bones.