A cell is the smallest structural and functional unit of an organism, typically microscopic and consisting of cytoplasm and a nucleus enclosed in a membrane.

The difference between plant and animal cells is that although, the overall function of the cell is the same, there are some important differences between animal and plant cells. The first difference is that plant cells have an organelle called chloroplast.

Bone cells: There are two categories of bone cells. Osteoclasts are in the first category. They resorb (dissolve) the bone. The other category is the osteoblast family, which consists of osteoblasts that form bone, osteocytes that help maintain bone, and lining cells that cover the surface of the bone.

Muscle cells: Muscle Cell Types. Muscle tissue, one of the four major tissue types, plays the vital role of providing movement and heat generation to the organs of the body. Within muscle tissue are three distinct groups of tissues: skeletal muscle, cardiac muscle, and smooth muscle.

Blood cells: Transporting oxygen and nutrients to the lungs and tissues. Forming blood clots to prevent excess blood loss. Carrying cells and antibodies that fight infection. Bringing waste products to the kidneys and liver, which filter and clean the blood. Regulating body temperature.

Our skin is made of hair tissue, oil and sweat gland tissues, nervetissue, blood tissue, and many other tissues to make the organ calledskin. Our eyes are made of nerve tissue, blood vessel tissue, muscletissue, lens tissue, pupil tissue, and many more types of tissue to make the organ called eyes. Organs have many different purposes.

The digestive system: The organs and glands in the body that are responsible for digestion. The digestive system begins with the mouth and extends through the esophagus, stomach, small intestine, and large intestine, ending with the rectum and anus.

Circulatory system: The system that circulates blood and lymph through the body, consisting of the heart, blood vessels, blood, lymph, and the lymphatic vessels and glands.

Respiratory system: a system of organs functioning in respiration and in humans consisting especially of the nose, nasal passages, pharynx, larynx, trachea, bronchi, and lungs.