The integumentary system consists of the skin, hair, nails, glands, and nerves. Its main function is to act as a barrier to protect the body from the outside world. It also functions to retain body fluids, protect against disease, eliminate waste products, and regulate body temperature
The skin consists of two layers – the dermis and the epidermis. Together, these two layers form the largest organ in the body, with a surface area of nearly 2 square meters.
The epidermis is the outer layer, resting atop the dermis. There is no direct blood supply to the epidermis and therefore, the cells of this stratified squamous tissue obtain nutrients and oxygen through diffusion. This layer also cushions underlying tissues and protects them from desiccation. In hot, dry environments, water is first lost from this layer. Similarly, extended exposure to water during baths or during swimming, crinkles the skin since water is absorbed and retained in the epidermis.
The epidermis is made of four layers – the stratum basale, stratum spinosum, stratum granulosum and stratum corneum. In each of these layers, keratinocytes undergo successive steps in differentiation beginning with the proliferative layer in the innermost stratum basale containing keratinocyte stem cells. After division, cells migrate outwards to form a layer of spiny cells called stratum spinosum. The nuclei of these cells are primarily involved in transcribing large amounts of keratin mRNA and other microfibrils that form impermeable cell junctions. The next layer of the epidermis is called stratum granulosum and contains keratinocytes with a granular cytoplasm. This stage in keratinocyte maturation is characterized by the formation of the lipid barrier of the body. The presence of keratohyalin granules is important for crosslinking keratin filaments and dehydrating cells to form tight, interlinked layers of cells that perform the barrier function of skin. The outermost layer is called the stratum corneum and is directly exposed to the external environment. It consists of multiple layers of terminally differentiated keratinocytes that are also called corneocytes. These cells do not have a nucleus and contain copious amounts of keratin filaments. This layer of the epidermis provides mechanical strength and rigidity to the structure of skin. These anucleated cells are resistant to virus attack and are replaced every 15 days, preventing them from becoming a reservoir of infection. The parts of the skin that have no hair follicles have an extra layer of epithelium called the stratum lucidum that is sandwiched between the stratum granulosum and stratum corneum. This extra layer makes the epithelium of these regions ‘thicker’ than those in other parts of the body. Usually, this is the skin on the palms of the hands and soles of the feet, and in addition to stratum lucidum, is also well supplied with nerve endings.
The second major section of the integument is the dermis, and is occasionally called the ‘true skin’ since it is supplied with blood vessels and nerve endings. Sebaceous glands and sweat glands are also present in the dermis. The closest that the dermis gets to the external environment is at structures called dermal papillae. These are finger-like projections into the epidermis and, on the palms, form fingerprints.
Sebaceous glands produce sebum – an oily, waxy secretion containing many lipids. The cells forming a sebaceous gland have extremely short lifespans – barely over a week. The soles of the feet are free from sebaceous glands, though the sections of skin between the toes is richly supplied with these structures. Sebum also forms a part of ear wax. These lipids can provide a rich environment for the growth of bacteria, and therefore contribute towards body odor, either when the glands are clogged or when the sebum is not removed periodically.
The dermis also plays host to sweat glands. Sweat, in contrast to sebum, is a water-based secretion, containing electrolytes – sodium salts, urea, and even trace amounts of uric acid. While most water soluble waste products are removed in the urine, sweat also contributes towards clearing some of the metabolic byproducts of the body. The presence of many acids, such as lactic acid and acetic acid, makes sweat mildly acidic. A subsection of sweat glands, called apocrine glands, even release proteins, carbohydrates, lipids or steroids. Sweat from these glands, along with sebum, can encourage bacterial growth, and form the site for infection, odor or rashes.
Skin
Image shows cross section of skin, with various dermal and epidermal layers, glands, nerves and blood vessels.
Functions of the Integumentary System
Each layer of the skin contributes to the overall function within the body. The most obvious role of the skin is to protect the body from external aggression.
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Answer:
The integumentary system consists of the skin, hair, nails, glands, and nerves. Its main function is to act as a barrier to protect the body from the outside world. It also functions to retain body fluids, protect against disease, eliminate waste products, and regulate body temperature
Answer:
The skin consists of two layers – the dermis and the epidermis. Together, these two layers form the largest organ in the body, with a surface area of nearly 2 square meters.
The epidermis is the outer layer, resting atop the dermis. There is no direct blood supply to the epidermis and therefore, the cells of this stratified squamous tissue obtain nutrients and oxygen through diffusion. This layer also cushions underlying tissues and protects them from desiccation. In hot, dry environments, water is first lost from this layer. Similarly, extended exposure to water during baths or during swimming, crinkles the skin since water is absorbed and retained in the epidermis.
The epidermis is made of four layers – the stratum basale, stratum spinosum, stratum granulosum and stratum corneum. In each of these layers, keratinocytes undergo successive steps in differentiation beginning with the proliferative layer in the innermost stratum basale containing keratinocyte stem cells. After division, cells migrate outwards to form a layer of spiny cells called stratum spinosum. The nuclei of these cells are primarily involved in transcribing large amounts of keratin mRNA and other microfibrils that form impermeable cell junctions. The next layer of the epidermis is called stratum granulosum and contains keratinocytes with a granular cytoplasm. This stage in keratinocyte maturation is characterized by the formation of the lipid barrier of the body. The presence of keratohyalin granules is important for crosslinking keratin filaments and dehydrating cells to form tight, interlinked layers of cells that perform the barrier function of skin. The outermost layer is called the stratum corneum and is directly exposed to the external environment. It consists of multiple layers of terminally differentiated keratinocytes that are also called corneocytes. These cells do not have a nucleus and contain copious amounts of keratin filaments. This layer of the epidermis provides mechanical strength and rigidity to the structure of skin. These anucleated cells are resistant to virus attack and are replaced every 15 days, preventing them from becoming a reservoir of infection. The parts of the skin that have no hair follicles have an extra layer of epithelium called the stratum lucidum that is sandwiched between the stratum granulosum and stratum corneum. This extra layer makes the epithelium of these regions ‘thicker’ than those in other parts of the body. Usually, this is the skin on the palms of the hands and soles of the feet, and in addition to stratum lucidum, is also well supplied with nerve endings.
The second major section of the integument is the dermis, and is occasionally called the ‘true skin’ since it is supplied with blood vessels and nerve endings. Sebaceous glands and sweat glands are also present in the dermis. The closest that the dermis gets to the external environment is at structures called dermal papillae. These are finger-like projections into the epidermis and, on the palms, form fingerprints.
Sebaceous glands produce sebum – an oily, waxy secretion containing many lipids. The cells forming a sebaceous gland have extremely short lifespans – barely over a week. The soles of the feet are free from sebaceous glands, though the sections of skin between the toes is richly supplied with these structures. Sebum also forms a part of ear wax. These lipids can provide a rich environment for the growth of bacteria, and therefore contribute towards body odor, either when the glands are clogged or when the sebum is not removed periodically.
The dermis also plays host to sweat glands. Sweat, in contrast to sebum, is a water-based secretion, containing electrolytes – sodium salts, urea, and even trace amounts of uric acid. While most water soluble waste products are removed in the urine, sweat also contributes towards clearing some of the metabolic byproducts of the body. The presence of many acids, such as lactic acid and acetic acid, makes sweat mildly acidic. A subsection of sweat glands, called apocrine glands, even release proteins, carbohydrates, lipids or steroids. Sweat from these glands, along with sebum, can encourage bacterial growth, and form the site for infection, odor or rashes.
Skin
Image shows cross section of skin, with various dermal and epidermal layers, glands, nerves and blood vessels.
Functions of the Integumentary System
Each layer of the skin contributes to the overall function within the body. The most obvious role of the skin is to protect the body from external aggression.