Explanation: Humans have two lungs; a right lung and a left lung. They are situated within the thoracic cavity of the chest.

Explanation: The heart has two sides: the left side and the right side. Each side of the heart is divided into two parts; called the atrium and the ventricle.

Explanation: The heart has two sides: the left side and the right side. Each side of the heart is divided into two parts; called the atrium and the ventricle. The atrium is the top part. The ventricle is on the bottom.

Explanation: A baby’s body has about 300 bones at birth. These eventually fuse (grow together) to form the 206 bones that adults have.

Explanation: Adults have 32 teeth. You should have this full set of adult teeth by your late teens.

Explanation: The epidermis is composed of 4 or 5 layers; depending on the region of skin being considered. Those layers in descending order are: cornified layer (stratum corneum).

Explanation: Up to 60% of the human adult body is water.

Explanation: The femur is your thigh bone. It's the longest; strongest bone in your body.

Explanation: Cerebrum is the largest part of the brain and is composed of right and left hemispheres.

Explanation: As the heart beats; it pumps blood through a system of blood vessels; called the circulatory system. The vessels are elastic tubes that carry blood to every part of the body.

Explanation: The stapes is the third bone of the three ossicles in the middle ear. The stapes is a stirrup-shaped bone; and the smallest in the human body.

Explanation: Human teeth are made up of four different types of tissue: pulp; dentin; enamel and cementum.

Explanation: The double helix is a description of the molecular shape of a double-stranded DNA molecule.

Explanation: Fingernails and toenails are made of a tough protective protein called alpha-keratin. This protein is also found in the hooves and horns of different animals.

Explanation: Femur; or thighbone; is the largest bone in our body. By most measures the femur is the strongest bone in the body.

Explanation: The gluteus maximus is not only one of the strongest muscles in the body; it is also the largest. It’s main function is hip extension

Explanation: The cornea contains no blood vessels and is extremely sensitive to pain.

Explanation: Ligaments connect the ends of bones together in order to form a joint.

Explanation: The largest external organ; which is also the largest organ in general; is the skin.

Explanation: The largest internal organ is the liver. It is also the heaviest organ; with an average of 1.6 kilograms

Explanation: Red blood cells; most white blood cells and platelets are produced in the bone marrow; the soft fatty tissue inside bone cavities.

Explanation: The lymphatic system is a network of very small tubes (or vessels) that drain lymph fluid from all over the body.

Explanation: The bones of the chest and upper back combine to form the strong; protective rib cage around the vital thoracic organs such as the heart and lungs.

Explanation: Teeth cannot regenerate or repair themselves after damage because they lack living cells in their enamel and dentin.

Explanation: The weakest bone in the human body is the spine or spinal cord or sometimes it can be nose as well. We can call it weakest because of sheer smallness.

Explanation: The smallest and weakest muscle of the body is the stapedius and is located in the middle ear.