Human Anatomy and Physiology - Integumentary System
The Integumentary system functions in protection, in the regulation of body temperature, in the
excretion of waste materials, in the synthesis of vitamin D3 with the help of sun rays, and in the
reception of various stimuli perceived as pain, pressure and temperature.
The system consists of the skin and its derivatives, including hair, nails, and several types of
glands.
Skin
Skin is the largest organ in the body occupying almost 2m2 of surface area thickens of 2mm.
Functions of Skin
1. Protection against harmful microorganisms, foreign materials and it prevents excessive loss
of body fluid.
2. Temperature regulation with the sweat, heat leaves the body.
3. Excretion of small amounts of waste products from the body such as urea.
4. Synthesize Vitamin D (sunshine vitamin) by the action of UltraViolet.
5. Sensory reception - it contains sensory receptors of heat, cold, touch, pressure, and pain.
Main Parts of Skin
a. Epidermis is the outer layer of the skin that is made of stratified squamous epithelium. It has
no blood supply.
Epidermis contains 4-5 strata.
1. Stratum corneum - is the outer, dead, flat, Keratinized and thicker layer.
2. Stratum lucidum - is next to stratum corneum. It consists of flat, translucent layers of
cells. This stratum is found in thick skin only.
3. Stratum granulosum - lies just below stratum lucidum. The cells in this layer are in the
process of keratinization.
4. Stratum spinosum - next down to stratum granulosum. The cells in this stratum have a
poly-hydral shape and they are in the process of protein synthesis.
5. Stratum basale - rests on the basement membrane, and it is the last layer of epidermis
next to stratum spinosum. Stratum basale together with stratum spinosum constitute
stratum germinativum.
, b. Dermis (true skin) - a strong, flexible, connective tissue mesh work of collagen, reticular and
elastic fibers. Most of the skin is composed of dermis.
Dermis contains papillary and reticular layers.
1. Papillary layer - is next to the stratum basale of the epidermis.
It contains loose connective tissue within the bundles of collagenous fibers.
It also contains loose capillaries that nourish the epidermis.
In some areas papillary layers have special nerve endings that serve as touch receptors
(meissner’s corpuscles).
Indentations of the papillary layer in the palms and soles reflected over the epidermis to
create ridges.
2. Reticular layer - next to papillary layer. It is made of dense connective tissue with a
course of collagenous fiber bundles that crisscross to form a stoma of elastic networks.
In the reticular layer many blood and lymphatic vessels, nerves, fat cell, sebaceous (oil)
glands and hair roots are embedded.
Receptors of deep pressure (pacinian corpuscles) - are distributed throughout the dermis.
c. Hypodermis or subcutaneous layer (under the skin) - it is found beneath the dermis.
Hypodermis is composed of loose, fibrous connective tissue, which is richly supplied with
lymphatic and blood vessels and nerves.
Hypodermis is much thicker than dermis, within it coils of ducts of sudoriferous (sweat) glands,
and the base of hair follicles.
Color of the skin is determined by 3 factors
1. The presence of melanin, a dark pigment produced by a specialized cell called melanocyte.
2. The accumulation of yellow pigment carotene.
3. The color of blood reflected through the epidermis.
The main function of melanin is to screen out excessive ultraviolet rays.
All races have some melanin in their skins although the darker races have slightly more
melanocytes.
Albinism is an inherited condition that leads to someone having very light skin, hair, and
eyes. (The person who is genetically unable to produce any melanin is an albino.)
2 Kinds of Glands of the skin
1. Sudoriferous (sweat) glands - secrete sweat.
The Integumentary system functions in protection, in the regulation of body temperature, in the
excretion of waste materials, in the synthesis of vitamin D3 with the help of sun rays, and in the
reception of various stimuli perceived as pain, pressure and temperature.
The system consists of the skin and its derivatives, including hair, nails, and several types of
glands.
Skin
Skin is the largest organ in the body occupying almost 2m2 of surface area thickens of 2mm.
Functions of Skin
1. Protection against harmful microorganisms, foreign materials and it prevents excessive loss
of body fluid.
2. Temperature regulation with the sweat, heat leaves the body.
3. Excretion of small amounts of waste products from the body such as urea.
4. Synthesize Vitamin D (sunshine vitamin) by the action of UltraViolet.
5. Sensory reception - it contains sensory receptors of heat, cold, touch, pressure, and pain.
Main Parts of Skin
a. Epidermis is the outer layer of the skin that is made of stratified squamous epithelium. It has
no blood supply.
Epidermis contains 4-5 strata.
1. Stratum corneum - is the outer, dead, flat, Keratinized and thicker layer.
2. Stratum lucidum - is next to stratum corneum. It consists of flat, translucent layers of
cells. This stratum is found in thick skin only.
3. Stratum granulosum - lies just below stratum lucidum. The cells in this layer are in the
process of keratinization.
4. Stratum spinosum - next down to stratum granulosum. The cells in this stratum have a
poly-hydral shape and they are in the process of protein synthesis.
5. Stratum basale - rests on the basement membrane, and it is the last layer of epidermis
next to stratum spinosum. Stratum basale together with stratum spinosum constitute
stratum germinativum.
, b. Dermis (true skin) - a strong, flexible, connective tissue mesh work of collagen, reticular and
elastic fibers. Most of the skin is composed of dermis.
Dermis contains papillary and reticular layers.
1. Papillary layer - is next to the stratum basale of the epidermis.
It contains loose connective tissue within the bundles of collagenous fibers.
It also contains loose capillaries that nourish the epidermis.
In some areas papillary layers have special nerve endings that serve as touch receptors
(meissner’s corpuscles).
Indentations of the papillary layer in the palms and soles reflected over the epidermis to
create ridges.
2. Reticular layer - next to papillary layer. It is made of dense connective tissue with a
course of collagenous fiber bundles that crisscross to form a stoma of elastic networks.
In the reticular layer many blood and lymphatic vessels, nerves, fat cell, sebaceous (oil)
glands and hair roots are embedded.
Receptors of deep pressure (pacinian corpuscles) - are distributed throughout the dermis.
c. Hypodermis or subcutaneous layer (under the skin) - it is found beneath the dermis.
Hypodermis is composed of loose, fibrous connective tissue, which is richly supplied with
lymphatic and blood vessels and nerves.
Hypodermis is much thicker than dermis, within it coils of ducts of sudoriferous (sweat) glands,
and the base of hair follicles.
Color of the skin is determined by 3 factors
1. The presence of melanin, a dark pigment produced by a specialized cell called melanocyte.
2. The accumulation of yellow pigment carotene.
3. The color of blood reflected through the epidermis.
The main function of melanin is to screen out excessive ultraviolet rays.
All races have some melanin in their skins although the darker races have slightly more
melanocytes.
Albinism is an inherited condition that leads to someone having very light skin, hair, and
eyes. (The person who is genetically unable to produce any melanin is an albino.)
2 Kinds of Glands of the skin
1. Sudoriferous (sweat) glands - secrete sweat.
