Lips

Lips are lower or upper fleshy structure surrounding the opening of the mouth. It serves as an opening for the intake of food and also helps with the articulation of our voice. Lips have sensory nerve which could become sensitive when kissing another person in a sexual manner. The skin of the lips and its fewer melanocytes (responsible for the production of skin color pigments) is what gives our lips a thinner and contrasting color compare to the facial skin surrounding it. Therefore the blood vessels appear on the lips which gives it's red color. It is also worth mentioning that lips do not have sweat gland or sebaceous glands, therefore it gets drier faster that other areas of human body.

Nail

Nails are made of Keratin which is hard protein. It is an elastic structure at the end of a finger or a toe. Each nail is divided into three parts. The root of the nail fastens the nail to the finger or toe by fitting into the dermis of the skin. There are vascular ridges underneath the nail body and on the nail plate which lies under the nail body. The part of the nail bed that the behind the nail root is responsible for the production of new nail cells. Nails are similar to claws and hoofs as well.

Eustachian tube

The Eustachian tube is a tube that connects the nasopharynx with the middle ear cavity. The tube is normally closed but opens when a person is yawning, chewing or swallowing to create a balance of air pressure in the middle ear in comparison to the air pressure outside. It is approximately 3.5 centimeters long. The Eustachian tube drains the mucous from the middle ear to the pharynx but may not drain properly if it is infected which could cause a swelling of the tube.