Biology topic – “Skin (त्वचा/चर्म) of Human Body”, is important for all competitive exams like CET, SSC CGL, SSC CHSL, RRB NTPC, UPSC and other state civil services exams. In these exams, almost 4-5 questions are coming from Biology. Let’s start the topic – Skin (त्वचा/चर्म) of Human Body:-
Skin of Human Body
(मानव – त्वचा/चर्म)
Skin is an organ that covers our entire body and keeps the good stuff in and the bad stuff out. The study of skin is called dermatology and a person who studies dermatology is called a dermatologist.
Integumentary System (अध्यावरणी तंत्र)
The skin is part of an important organ system called the integumentary system. The integumentary system consists of the skin, hair, nails, and exocrine glands.
Layers of the skin
Our skin has three primary layers. Each one has its own function.
- Hypodermis (The Subcutaneous).
1. Epidermis – The epidermis is the outer layer of skin. Its main function is protection. The cells on the very outer layer of the epidermis are constantly dying and getting replaced by new cells as deep in the epidermis new cells are growing.
- These cells contain Keratin, which makes the skin waterproof and tough.
- Other cells in the epidermis produce a pigment called melanin. This darkens the skin and protects you from strong sunlight.
- The darker our skin means the more melanin we have. People with fair skin get sunburnt more quickly than people with dark skin.
2. Dermis – The dermis is a thicker and more elastic (stretchy) layer. In this layer there are:
- Hair follicles
- Blood vessels.
- Glands: We have two types of glands in skin.
- Sebaceous glands produce sebum, a kind of oil, which helps keep our skin soft and waterproof.
- Sweat glands make sweat. When our body gets hot, the sweat glands make a lot of sweat which they send up through pores (tiny holes) to the surface of our skin to cool us down.
- Hair follicles
- Hair covers most of our body (except our lips, the palms of our hands and the soles of our feet). The hair is made in the dermis in the hair follicles. Hair follicles look like tiny bulbs from which our hair grows. Most of the hair on our body is short and fine.
- Tiny networks of nerves act as sensors to let us feel the world around us. They tell us the temperature around us, make us feel pain if something hurts our skin and let us feel how smooth or rough things are and how hard our skin is being pressed.
- The nerves in our skin send a message to the hypothalamus in our brain and back comes the signal to swing into action.
- The hypothalamus is in charge of keeping our body’s core temperature at the right level (around 37°C or 98°F).
- Blood vessels
- Blood vessels carry oxygen and nutrients (food) to the cells and carry away the waste.
- Hair follicles
3. Hypodermis (The Subcutaneous) layer – The subcutaneous tissue also called the hypodermis which is the lowermost layer of the integumentary system in vertebrates.
- The hypodermis lies under the dermis and connects the skin to muscles and bone. It is mostly made up of fat. Fat acts as a cushion to protect our body if we bang into something. It also keeps us warm.
Functions of our Skin
The skin is our outermost multipurpose protection system against the outside environment, it contains one of our five senses, it absorbs sunlight for vitamin D and heat, and regulates our internal temperature.
- Protection – One of the basic functions of the skin is protection. Over the majority of our body the skin is around 2 mm thick. In some areas, like our eyelids, it’s thinner, while in other areas, like the soles of your feet, it’s much thicker. The skin helps to keep bad stuff out of our body, like germs and dirt that can cause infection. It also keeps good stuff in, like fluids such as water and blood.
- Sense of Touch – The skin also contains one of our five senses: touch. In our skin, there are thousands of sensors or receptor cells. These sensors send information to the brain about things we touch. They can tell the brain if it’s hot, cold, rough, smooth, or painful. Different areas of our body have more receptor cells than others. Our hands, feet, and lips all have extra receptors making those areas even more sensitive. There are actually different types of receptor cells for each type of sensation.
- Temperature Control– The skin plays a large role in regulating our body’s temperature. When we get too hot it sweats to help cool us off. It can also widen the skin’s blood vessels to get more blood near the skin where it can cool off. At the same time the skin can narrow the blood vessels to help us warm up. By controlling blood flow and sweat, the skin regulates our body’s temperature.
When our body gets too cold.
- Blood vessels narrow so that you keep warmer inside.
- Sweat glands don’t send sweat to the surface.
- Hairs stand up straight to trap a warm layer of air next to our skin.
Note: When we are cold (or frightened) our skin gets “goose bumps”.These are made by tiny muscles pulling our hairs to make them stand up straight.
Important Facts about Skin for Competitive Exams.
- The study of skin is called Dermatology and a person who studies dermatology is called a dermatologist.
- Skin is the soft outer tissue of the human body and is part of the integumentary system.
- Skin is an organ and is the largest organ in the human body.
- About 15% of the body weight of an average adult human is skin.
- The thickest skin on the human body is the palms and the bottom of the feet and is around 1.5 millimeters thick.
- The thinnest skin on the human body is around the eyes and the eyelids and is only 0.2 millimeters thick.
- An average adult human has around 21.5 square feet of skin.
- Human skin can regenerate itself and a new layer is replaced every 28 to 30 days.
- Human skin has three main layers and they are the epidermis, the dermis and the hypodermis.
- The epidermis is the visible part of our skin and the outermost layer and it helps protect the human body from pathogens and regulates the release of water.
- The dermis is the layer of skin underneath the epidermis and helps support the epidermis. The dermis contains nerve endings, sweat glands, hair follicles and blood vessels.
- The hypodermis is the layer of skin underneath the dermis and is what connects our skin to bones and muscles.
- The color of skin is determined by the amount of melanin produced. Heavy production of melanin will produce darker colored skin, while lighter production of melanin will produce light colored skin.
- Skin can repair itself, but if the damage is severe enough scar tissue will develop.
- Scar tissue is repaired skin that is discolored and has no sweat glands or hair follicles.
- Human skin is home to millions of beneficial bacteria known as skin microbiota.
- Sunburn is a type of skin burn that we caused from radiation from the sun and it can increase the risk of 3-types of skin cancer.
- A little of the dust in our home is dead human skin cells.
- Sunblock/Sunscreen, is a topical product used to protect our skin from ultraviolet radiation (UV).
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