The Skin, parts and functions

The skin is the largest organ of the human body and is responsible for protecting our internal organs from external factors such as the sun, bacteria, and other environmental toxins. In this blog post, we will discuss the anatomy and function of the skin, common skin conditions, and tips for maintaining healthy skin.

Anatomy and Function of the Skin

The skin is composed of three main layers: the epidermis, dermis, and subcutaneous tissue. The epidermis is the outermost layer and is responsible for protecting the body from external factors. It is composed of several layers of cells, including the stratum corneum, which is the outermost layer and is composed of dead skin cells. The dermis is the middle layer of the skin and is composed of connective tissue, hair follicles, and sweat glands. The subcutaneous tissue is the deepest layer is composed of fat and connective tissue.

The skin has several important functions, including protection from the sun\’s harmful UV rays, regulation of body temperature, and production of vitamin D. This also contains sensory receptors that allow us to feel touch, heat, and cold.

Common Skin Conditions

  1. Acne

Acne is a common skin condition that occurs when hair follicles become clogged with oil and dead cells. This can lead to the formation of pimples, blackheads, and whiteheads. Acne is most common in teenagers but can affect people of all ages. Treatment options for acne include topical and oral medications, such as antibiotics and retinoids.

  1. Eczema

Eczema, also known as atopic dermatitis, is a chronic sk condition characterized by dry, itchy, and inflamed skin. Eczema is most common in children but can affect people of all ages. Treatment options for eczema include moisturizers, topical steroids, and oral medications.

  1. Psoriasis

Psoriasis is a chronic skin condition characterized by thick, scaly patches of skin that are often red and inflamed. Psoriasis is caused by an overactive immune system and can be triggered by stress, infections, and certain medications. Treatment options for psoriasis include topical medications, light therapy, and oral medications.

  1. Rosacea

Rosacea is a chronic skin condition that causes redness and swelling on the face, particularly on the cheeks, nose, chin, and forehead. Rosacea is most common in people with fair skin and can be triggered by sun exposure, alcohol, and spicy foods. Treatment options for rosacea include topical medications, oral antibiotics, and laser therapy.

  1. Skin Cancer

Skin cancer is a serious condition that occurs when abnormal cells grow and multiply uncontrollably on the skin. The most common types of skin cancer are basal cell carcinoma, squamous cell carcinoma, and melanoma. Treatment options for skin cancer include surgery, radiation therapy, and chemotherapy.

Tips for Maintaining Healthy Skin

  1. Protect Your Skin from the Sun

Exposure to the sun\’s harmful UV rays can cause skin damage and increase the risk of skin cancer. To protect your skin from the sun, wear protective clothing, such as long-sleeved shirts and hats, and use a broad-spectrum sunscreen with an SPF of at least 30.

  1. Moisturize Your Skin

Dry skin can lead to itching, flaking, and cracking, which can increase the risk of infection. To keep your skin moisturized, use a fragrance-free moisturizer daily, particularly after showering or bathing.

  1. Practice Good Hygiene

Practicing good hygiene can help prevent skin infections and other skin conditions. To maintain good hygiene, wash your hands regularly, bathe or shower daily, and avoid sharing personal items, such as towels and razors

Epidermis part of the skin

The epidermis is the outermost layer and it is made up of three layers: (i) cornified layer (ii) granular layer (iii) malpighian layer.

The cornify layer of the skin:

It is the outermost layer of the epidermis. It is made up of flat, hard and scaly cells. The cells of cornified layer are dead.

The granular layer of the skin:

This contains the living cells where the active division of cells takes place. These cells replace the cells of the granular layer which in turn are replacing the cells of the cornified layer which are constantly being worn-out.


The Malpighian layer of the skin:

This contains granules of a pigment called melanin. This hair pigment is responsible for skin colour. Melanin also prevents the penetration of a lot of violet rays of sunlight.

The Malpighian layer also contains another pigment called keratin which is responsible for the toughness and flexibility of the skin.

Dermis: fibrous collective tissues. The dermis contains nerves which enable the skin to be sensitive to changes in its environment such as pain, heat, temperature, touch, cold, etc.. The blood and lymph vessels supply materials to the skin, remove wastes from the skin cells and carry out temperature regulation. The sweat glands which consist of a coiled tubular gland opening into the epidermis excrete water and salts as sweat, sebaceous or oil gland which produces an oily substance called sebum. This helps to lubricate the hair and make it waterproof, while the erector muscle controls the erection of the hairs on the skin surface by its contraction and relaxation. Underneath the skin is a layer of fat called subcutaneous fatty tissue. This fat layer varies in thickness, depending on the part of the body.


The functions of the skin include the following:
(1) Protection: The skin protects the inner skin or tissue from mechanical injuries, bacterial infection, and ultraviolet rays of the sunlight and against desiccation.

(2) Excretion: The skin excretes excess water, mineral salts and nitrogenous wastes through the sweat glands as sweat
(3) Sensitivity: The skin is sensitive to its environment through the specialized sensory nerve endings scattered in the dermis. The skin is sensitive to such stimuli as changes in temperature, pressure, pain and cold.
(4) Production of vitamin D: The skin manufactures Vitamin D by using infra-red rays from sunlight
(5) Production of milk in females: The mammary gland which is a modification of the skin produces milk which is used for feeding the young one.
(6) Storage of preserved foods: Fats are stored under the dermis of mammals, especially those of pigs. Fats also form an insulating layer.

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(7) Regulation of body temperature: when an animal is hot, blood vessels under the epidermis of the skin dilate (vasodilation) and more blood is brought to the surface to be cooled through the process of convection and radiation. On the other hand, the blood vessels of the skin constrict (vasoconstriction) in cold weather, thereby conserving heat.

Facts about the skin

The skin is the body\’s largest organ, covering the entire body. In addition to serving as a protective shield against heat, light, injury, and infection, the skin also:

Regulates body temperature

Stores water and fat

Is a sensory organ

Prevents water loss

Prevents entry of bacteria

Throughout the body, the skin\’s characteristics vary (for example, thickness, colour, and texture). For instance, the head contains more hair follicles than anywhere else, while the soles of the feet contain none. In addition, the soles of the feet and the palms of the hands are much thicker than the skin on other areas of the body.

The skin is made up of the following layers, with each layer performing specific functions:



Subcutaneous fat layer


The human skin is the outer covering of the body and is the largest organ of the integumentary system. The skin has up to seven layers of ectodermal tissue and guards the underlying muscles, bones, ligaments and internal organs.[1] Human skin is similar to most other mammals\’ skin, and human skin is very similar to that of a pig. Though nearly all human skin is covered with hair follicles, it can appear hairless. There are two general types of skin, hairy and glabrous skin (hairless).[4] The adjective is cutaneous literally means \”of the skin\” (from the Latin cutis, skin).

Because it interfaces with the environment, it plays an important immunity role in protecting the body against pathogens[5] and excessive water loss.[6] Its other functions are insulation, temperature regulation, sensation, synthesis of vitamin D, and the protection of vitamin B folates. Severely damaged skin will try to heal by forming scar tissue. This is often discoloured and depigmented.

In humans, pigmentation varies among populations, and skin types can range from dry to oily. Such variety provides a rich and diverse habitat for bacteria that number roughly 1000 species from 19 phyla, present on the human skin.

The epidermis is the thin outer layer that consists of three types of cells:

Squamous cells. The outermost layer is continuously shed.

Basal cells. Basal cells are found just under the squamous cells.

Melanocytes. Melanocytes are found in every layer of the epidermis and make melanin, which gives the skin its colour.


The dermis is the middle layer of the skin. The dermis contains the following:

Blood vessels

Lymph vessels

Hair follicles

Sweat glands

Collagen bundles



The dermis is held together by a protein called collagen, which is made by fibroblasts. This layer gives skin flexibility and strength. It also contains pain and touch receptors.

Subcutaneous fat layer

The subcutaneous fat layer is the deepest layer of skin and consists of a network of collagen and fat cells. It helps conserve the body\’s heat and protects the body from injury by acting as a shock absorber.

Structure of the skin

Skin has mesodermal cells, pigmentation, such as melanin provided by melanocytes, which absorb some of the potentially dangerous ultraviolet radiation (UV) in sunlight.

It also contains DNA repair enzymes that help reverse UV damage, such that people lacking the genes for these enzymes suffer high rates of skin cancer.

One form predominantly produced by UV light, malignant melanoma, is particularly invasive, causing it to spread quickly, and can often be deadly. Human skin pigmentation varies among populations in a striking manner. This has led to the classification of people(s) on the basis of skin colour.

In terms of surface area, the skin is the second largest organ in the human body (the inside of the small intestine is 15 to 20 times larger). For the average adult human, the skin has a surface area of between 1.5-2.0 square meters (16.1-21.5 sq ft.). The thickness varies considerably over all parts of the body and between men and women and the young and the old. An example is the skin on the forearm which is on average 1.3 mm in the male and 1.26 mm in the female.

The average square inch (6.5 cm²) of skin holds 650 sweat glands, 20 blood vessels, 60,000 melanocytes, and more than 1,000 nerve endings.[11][better source needed] The average human skin cell is about 30 micrometres in diameter, but there are variants. A skin cell usually ranges from 25-40 micrometres (squared), depending on a variety of factors.

Skin is composed of three primary layers: the epidermis, the dermis and the hypodermis.[10]
Layers, Receptors, and Appendages of Human Skin


Epidermis, \”epi\” coming from the Greek meaning \”over\” or \”upon\”, is the outermost layer of the skin. It forms the waterproof, protective wrap over the body\’s surface which also serves as a barrier to infection and is made up of stratified squamous epithelium with an underlying basal lamina.

The epidermis contains no blood vessels, and cells in the deepest layers are nourished almost exclusively by diffused oxygen from the surrounding air and to a far lesser degree by blood capillaries extending to the outer layers of the dermis. The main type of cells which make up the epidermis are Merkel cells, and keratinocytes, with melanocytes and Langerhans cells also present. The epidermis can be further subdivided into the following strata (beginning with the outermost layer): corneum, lucidum (only in palms of hands and bottoms of feet), granulosum, spinosum, basale. Cells are formed through mitosis at the basal layer. The daughter cells (see cell division) move up the strata changing shape and composition as they die due to isolation from their blood source. The cytoplasm is released and the protein keratin is inserted. They eventually reach the corneum and slough off (desquamation).

This process is called \”keratinization\”. This keratinized layer is responsible for keeping water in the body and keeping other harmful chemicals and pathogens out, making skin a natural barrier to infection.

2D projection of a 3D OCT-tomogram of the skin at the fingertip, depicting the stratum corneum (~500 µm thick) with the stratum disjunctum on top and the stratum lucidum in the middle. At the bottom are the superficial parts of the dermis. The sweat ducts are clearly visible.

The epidermis contains no blood vessels and is nourished by diffusion from the dermis. The main type of cells which make up the epidermis are keratinocytes, melanocytes, Langerhans cells and Merkel cells. The epidermis helps to regulate body temperature.


Epidermis is divided into several layers where cells are formed through mitosis at the innermost layers. They move up the strata changing shape and composition as they differentiate and become filled with keratin. They eventually reach the top layer called the stratum corneum and are sloughed off, or desquamated. This process is called keratinization and takes place within weeks. The outermost layer of the epidermis consists of 25 to 30 layers of dead cells.

Epidermis is divided into the following 5 sublayers or strata:

Stratum corneum
Stratum lucidum
Stratum granulosum
Stratum spinosum
Stratum germinativum (also called \”stratum basale\”).

Blood capillaries are found beneath the epidermis, and are linked to an arteriole and a venule. Arterial shunt vessels may bypass the network in the ears, the nose and fingertips.

Genes and proteins expressed in the epidermis

About 70% of all human protein-coding genes are expressed in the skin.[13][14] Almost 500 genes have an elevated pattern of expression in the skin. There are less than 100 genes that are specific to the skin and these are expressed in the epidermis. An analysis of the corresponding proteins shows that these are mainly expressed in keratinocytes and have functions related to squamous differentiation and cornification.


The dermis is the layer beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbours many nerve endings that provide the sense of touch and heat. It contains the hair follicles, sweat glands, sebaceous glands, apocrine glands, lymphatic vessels and blood vessels. The blood vessels in the dermis provide nourishment and waste removal from its own cells as well as from the Stratum basale of the epidermis.

The dermis is structurally divided into two areas: a superficial area adjacent to the epidermis called the papillary region, and a deep thicker area known as the reticular region.
Papillary region

The papillary region is composed of loose areolar connective tissue. It is named for its fingerlike projections called papillae, which extend toward the epidermis. The papillae provide the dermis with a \”bumpy\” surface that interdigitates with the epidermis, strengthening the connection between the two layers

In the palms, fingers, soles, and toes, the influence of the papillae projecting into the epidermis forms contours in the skin\’s surface. These epidermal ridges occur in patterns (see: fingerprint) that are genetically and epigenetically determined and are therefore unique to the individual, making it possible to use fingerprints or footprints as a means of identification.
Reticular region

The reticular region lies deep in the papillary region and is usually much thicker. It is composed of dense irregular connective tissue and receives its name from the dense concentration of collagenous, elastic, and reticular fibres that weave throughout it. These protein fibres give the dermis its properties of strength, extensibility, and elasticity.

Also located within the reticular region are the roots of the hairs, sebaceous glands, sweat glands, receptors, nails, and blood vessels.

Tattoo ink is held in the dermis. Stretch marks often from pregnancy and obesity, are also located in the dermis.
Subcutaneous tissue
The subcutaneous tissue (also hypodermis and subcutis) is not part of the skin and lies below the dermis of the cutis. Its purpose is to attach the skin to underlying bone and muscle as well as supply it with blood vessels and nerves. It consists of loose connective tissue, adipose tissue and elastin. The main cell types are fibroblasts, macrophages and adipocytes (subcutaneous tissue contains 50% of body fat). Fat serves as padding and insulation for the body.

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Saprophytes, also known as saprotrophs, are organisms that obtain their nutrition by decomposing dead organic matter. They are an important part of the ecosystem, as they play a key role in breaking down dead plants and animals, and recycling nutrients back into the soil. Some examples of saprophytes include fungi, bacteria, and certain types of insects. They are essential for maintaining the balance of the ecosystem and for providing nutrients for other living organisms to grow and thrive.

types of saprophytes

There are several types of saprophytes, including:

  1. Fungi: Fungi are the most common type of saprophytes, and they are well-known for their ability to decompose dead plant and animal matter. They secrete enzymes that break down the complex molecules in dead organic matter into simpler compounds that they can absorb as nutrients.
  2. Bacteria: Many types of bacteria are saprophytic, and they play an important role in the decomposition of dead organic matter. They are responsible for breaking down complex molecules such as proteins, carbohydrates, and fats into simpler compounds that can be absorbed as nutrients.
  3. Actinomycetes: These are a group of bacteria that are commonly found in soil and are known for their ability to break down tough organic matter, such as cellulose and lignin.
  4. Myxomycetes: These are a group of slime moulds that feed on dead organic matter, including decaying leaves and wood.
  5. Insects: Some insects, such as flies and beetles, are also saprophytic and feed on dead organic matter.

Overall, saprophytes are an essential part of the ecosystem, as they play a crucial role in breaking down dead organic matter and recycling nutrients back into the soil.

Fisheries are an important component of our global food system, providing a critical source of protein and nutrients for millions of people around the world. However, overfishing and unsustainable fishing practices have led to declines in fish populations and threaten the long-term viability of this industry. In this blog post, we will explore the importance of fisheries, the challenges they face, and potential solutions for ensuring their sustainability.

Fisheries are an essential source of food and livelihood for millions of people around the world, particularly in coastal communities. In fact, over 50 million people rely on fishing and aquaculture for their livelihoods, and the industry contributes billions of dollars to the global economy each year. Fish are also a critical source of protein and other essential nutrients, particularly for communities in developing countries where access to other protein sources may be limited.

Despite the importance of fisheries, they face numerous challenges that threaten their long-term sustainability. One of the biggest challenges is overfishing, which occurs when fish populations are harvested at a rate that exceeds their ability to reproduce and replenish their numbers. Overfishing can lead to the collapse of fish populations, which not only threatens the viability of the industry but also has broader ecological impacts on marine ecosystems.

Other challenges facing fisheries include habitat destruction, pollution, and climate change. Habitat destruction, such as the destruction of coral reefs, mangrove forests, and seagrass beds, can have a significant impact on the health and abundance of fish populations. Pollution, such as plastic pollution and chemical runoff from agriculture, can also have negative impacts on fish populations and the health of marine ecosystems. Climate change is also a significant threat to fisheries, as rising temperatures and ocean acidification can disrupt the balance of marine ecosystems and alter the distribution and behavior of fish populations.

To address these challenges and ensure the sustainability of fisheries, a range of solutions are needed. One approach is to implement science-based management practices that aim to ensure the long-term sustainability of fish populations. This can include measures such as setting catch limits, establishing marine protected areas, and implementing fishing gear restrictions.

In addition, promoting sustainable aquaculture practices can provide an alternative to wild-caught fish and reduce the pressure on wild fish populations. Sustainable aquaculture practices can include using feed that is free from wild-caught fish, reducing waste and pollution from aquaculture operations, and ensuring that aquaculture facilities are located in areas that minimize their impact on the environment.

Consumers can also play an important role in promoting sustainable fisheries by making informed choices when purchasing seafood. This can include choosing seafood that is sustainably sourced, such as seafood that has been certified by programs such as the Marine Stewardship Council or the Aquaculture Stewardship Council.

In conclusion, fisheries play an important role in our global food system, providing a critical source of protein and nutrients for millions of people around the world. However, overfishing and unsustainable fishing practices threaten the long-term viability of this industry. To ensure the sustainability of fisheries, science-based management practices, sustainable aquaculture practices, and informed consumer choices are needed. By working together to address these challenges, we can ensure that fisheries continue to provide a vital source of food and livelihood for generations to come.

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