Body,Bone and Cell:-

1.Body:-

         The human body consists of a number of interacting 'systems'.The skeleton forms a rigid framework,Which,attached system responsible for the body's reaction to stimuli. Hormones, produced by the endocrine system,control many functions,including growth and developmental changes such as puberty. The cardiovascular system circulates blood around the body,delivering oxygen and nutrients and collecting carbon dioxide and waste,while the respiratory system fights infection.The digestive system derives energy and nutrients for growth and repair from food,and with the urinary system eliminates waster;the urinary system also helps to regulate chemicals in the body. The reproductive system is concerned with producing offspring. 

2.Cell:-

        The cell is the basic structural unit of every living things,and most plants and animals are composed of millions of them.cells work in unison to perform the tasks necessary to keep an organism alive.They vary is shape according to function;a human red blood cell is disk-shaped,while a nerve cell is thread like and ma
y be a matre long.Unlike animal cells,plants cells can produce their own food through photosynthesis.  

3.Bone:-

       Each layer of a bone is composed of specialized cells,protein fibres, and minerals. The medullary cavity contains bone marrow, and is enclosed in a spongy cancellous layer.This is surrounded by hard cortical bone,with an outer covering of periostium. This cobinataion of layers make bones strong and light.