Which of the following layers of skin lack blood vessels?
A.
Papillary
B.
Epidermis
C.
Reticular
D.
Hypodermis
The Correct answer and Explanation is:
The correct answer is B. Epidermis.
Explanation:
The skin is composed of three primary layers: the epidermis, dermis, and hypodermis (also known as the subcutaneous layer). Each of these layers plays a distinct role in protecting the body and maintaining homeostasis.
- Epidermis: The outermost layer of the skin is the epidermis. It is composed mainly of keratinocytes, which produce the protein keratin that helps protect the skin. The epidermis also contains melanocytes (which produce melanin, the pigment responsible for skin color) and Langerhans cells (which are involved in immune response). Importantly, the epidermis lacks blood vessels. Instead, it receives nutrients through diffusion from the underlying dermis. The absence of blood vessels in the epidermis helps to keep this layer lightweight and allows it to serve as an effective barrier against environmental hazards.
- Dermis: Situated beneath the epidermis, the dermis is divided into two sub-layers: the papillary dermis and the reticular dermis. The papillary dermis contains a network of capillaries that supply nutrients to the epidermis and play a role in thermoregulation. The reticular dermis, which is the thicker part of the dermis, contains larger blood vessels, sweat glands, sebaceous glands, and hair follicles. These blood vessels in the dermis help to regulate temperature and supply oxygen and nutrients to the skin.
- Hypodermis: Also known as the subcutaneous layer, the hypodermis is the deepest layer of skin. It consists of loose connective tissue and fat cells. The hypodermis contains larger blood vessels and nerves that supply the skin and underlying structures. It serves as an insulator, cushioning the body and absorbing shocks.
In summary, the epidermis is the only layer of skin that lacks blood vessels. It relies on diffusion from the dermis for its nourishment and maintains its protective role by being a robust barrier to external elements.