Question

What is the only body part that grows back?

Answer 1

1. Hair
 Hair is a unique organ that grows back after being cut off. It is composed of protein called keratin, which is what makes hair strong and resilient. When hair is cut, the follicle goes dormant until it receives enough blood supply to trigger its growth again. In humans, hair grows about 1-2cm per month.
 2. Skin
 Skin is the largest organ in our bodies. It is composed of three layers: epidermis, dermis, and hypodermis. The outermost layer, the epidermis, is the thinnest skin layer. It consists of dead cells that protect the inner layers of the skin. The dermis is the middle layer of the skin and contains collagen and elastin fibers. Elastin helps keep skin elastic and firm while collagen gives skin structure. The hypodermis is the deepest layer of skin and is where fat cells reside.
 3. Nails
 Nails are extensions of bone covered in keratin. Keratin is the same material that forms hair and fingernails. Nail growth occurs at the end of each finger and toe. Each nail has a root that anchors it into the underlying bone. Nails grow approximately 2mm per month.
 4. Teeth
 Teeth are made up of enamel, dentin, cementum, and pulp. Enamel is the hardest substance in the human body. It covers the outside of teeth and protects them from damage. Dentine is the soft tissue inside the tooth that provides support and nourishment. Cementum is the thin coating around the roots of the teeth that help anchor them into place. Pulp is the soft center of the tooth that produces nerves and blood vessels.
 5. Tongue
 The tongue is a muscular organ located in the mouth. It is responsible for tasting food and determining if it is safe to swallow. The tongue is also responsible for speaking and swallowing saliva. The tongue is composed of muscle, mucous membrane, and connective tissue.
 6. Ears
 Ears are two small organs located near the top of the head. They are made up of cartilage and have openings for sound waves to enter and exit. Ears are sensitive to temperature changes and vibrations.
 7. Nose
 The nose is a hollow tube located between the eyes and upper lip. It is used to smell things and identify odors. The nose is made up of bones, cartilage, and mucus membranes.

Answer 2

The only body part that grows back is the skin which can regenerate although the liver is also an organ and body part that can also grow back.

Other parts of the body that can grow back are fat, brain tissue, fingernails, toenails,

Regeneration means the regrowth of a damaged or missing organ part from the remaining tissue.

As adults, humans can regenerate some organs, such as the liver.

If part of the liver is lost by disease or injury, the liver grows back to its original size, though not its original shape.

Although some people who have a diseased portion of their liver removed are unable to regrow the tissue and end up needing a transplant.

Researchers from Michigan State University believe blood clotting factor fibrinogen may be responsible.

While some brain tissue can sometimes regenerate the brain actually can't regenerate itself well because when the brain is damaged its cells find it harder to make new ones.

This is because the brain has very few of the special cells, or stem cells.

Humans can't regenerate body parts other than skin and tissue or nails because mammals have more complex biological structures; limb regeneration would require sophisticated controls to ensure that limbs and organs don't grow out of control.

Humans, for example, are already equipped with safety mechanisms to ensure that individual cells don't grow uncontrollably.