Summary
The largest organ, forming a waterproof barrier that protects, senses and regulates temperature.
In depth
Epidermis (keratinised layers, melanocytes) and dermis (collagen, blood vessels, nerves, glands, hair follicles) and subcutaneous fat. Skin synthesises vitamin D under UV, prevents infection and loses water.
Skin has three layers. Melanin protects from UV. Sweat glands cool. Receptors give touch, temperature and pain.
Key idea: skin is the first line of defence.
Skin is the largest organ (about 1.5 to 2 square metres), making up about 15 percent of body weight. The epidermis renews every 4 to 6 weeks as keratinocytes move up from the basal layer and die, and melanocytes produce melanin, which protects against UV and sets colour. The dermis contains sensory receptors, sweat and sebaceous glands, and hair follicles. Functions: barrier, thermoregulation, sensation, vitamin D synthesis, immune defence (Langerhans cells), and excretion.
UV exposure causes sunburn, ageing and cancers (basal cell, squamous cell carcinoma and melanoma). Wounds heal through haemostasis, inflammation, proliferation and remodelling; deeper wounds scar with collagen. Fingerprints are formed by ridges in the dermis and are unique. Burns are classified by depth.
Remember: skin is the body's first barrier against infection.
Frequently asked questions
What is Skin?
The largest organ, forming a waterproof barrier that protects, senses and regulates temperature.
Which area of biology covers Skin, and how advanced is it?
Skin is one of the 51 topics in Human Physiology. It is rated Beginner, so it suits learners who are starting out in biology. Related topics in this area include Blood Components, Small Intestine Absorption, Tissues and Organs.
Can you give an example of Skin?
Burns damage barrier and cause fluid loss.
What should I learn before Skin?
Skin is a Beginner topic, so no earlier topic is required. Other Beginner topics in Human Physiology that pair well with it include Homeostasis, Tissues and Organs, Skeletal System.
What topics are related to Skin?
The closest topics to Skin are Blood Components, Small Intestine Absorption, Tissues and Organs, Diabetes Mellitus. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Skin?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Skin. To practise the whole of Human Physiology, use the Human Physiology quiz.
How is Skin different from Blood Components?
Skin: The largest organ, forming a waterproof barrier that protects, senses and regulates temperature. Blood Components: Plasma, red cells, white cells and platelets carry out transport, defence and clotting. Read both side by side and note what each one explains.
How should I study Skin step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Blood Components and explain the difference aloud. Finally, take the Human Physiology quiz and come back to this page for any question you miss.