Integumentary System
I. Functions
1. Protection: Skin gives an anatomical barrier between the internal and external
environment in bodily defense; Langerhans cells in the skin are part of the immune
system; Protection of organs and tissues
2. Sensation: Skin contains a variety of nerve endings that react to heat, cold, touch,
pressure, vibration, and tissue injury
3. Heat regulation: The skin contains a blood supply far greater than its requirements
which allows precise control of energy loss by radiation, convection and conduction.
Dilated blood vessels increase perfusion and heat loss while constricted vessels
greatly reduce cutaneous blood flow and conserve heat. Erector pili muscles are
significant in animals; Regulation of body temperature
- muscle contraction
- movement of blood vessels
4. Sweat Excretion: Removal of waste products, water and organic compounds
5. Production of vitamin D (ergoesterol)
- happens in the kidney
- UV light stimulates production
Skin
- made up of a layer of tissues that guard underlying muscles and0 organs
- plays the most important role in protecting against pathogens
- insulation and temperature regulation, sensation and vitamin D and B synthesis
- weighs approximately 9lbs 0147
- Used to determine body fat
- normal skin cell cycle takes up around 40-56 days
- the stratum corneum 25 or more layers
I. Major layers of skin and its structures
The skin has two major layers which are made of different tissues and have very
different functions.
Skin is composed of the
a) epidermis
b) the dermis.
c) hypodermis - deeper subcutaneous tissue
note: Below these layers lies the hypodermis or subcutaneous adipose layer, which is not
usually classified as a layer of skin.
A. The OUTERMOST EPIDERMIS
- consists of stratified squamous keratinizing epithelium with an underlying
basement membrane
- has all of the shapes of the epithelial cell
- This layer of skin is responsible for keeping water in the body and keeping other
harmful chemicals and pathogens out.
, - The main type of cells which make up the epidermis are
keratinocytes,
melanocytes
Langerhans cells
- Cells are formed through mitosis at the innermost layers.
Note: They move up the strata changing shape and composition as they
differentiate, inducing expression of new types of keratin genes. They eventually
reach the corneum and become sloughed off (desquamation), this process is called
keratinization and takes place within about 30 days.
SPECIAL EPIDERMAL CELLS & STRUCTURES in the EPIDERMIS
keratinocytes (as they move up, they take in keratin)
- produce keratin
- taken by endocytosis
melanocytes
- produce melanin: pigment (big cells between epidermal cells)
hair
nail
Note:
Thick skin: no hair, sole, palm (all layers of epidermis is present here)
Thin skin: hairy part anything that is not the sole or palm (absent of lucidum)
can be further subdivided into the following strata (beginning with the outermost layer):
(a) Corneum
Lucidum -
Granulosum - (b) transition layers
Spinosum -
(c) Basale
a) CORNEUM (mostly dead cells)
- The stratum corneum is the most superficial layer of the epidermis
- the layer exposed to the outside environment
- 20-30 layers of dead squamous cells filled with keratin
- accounts for 75% of epidermal thickness
- This dry, dead layer helps prevent the penetration of microbes and the
dehydration of underlying tissues, and provides a mechanical protection against
abrasion for the more delicate, underlying layers.
- The entire layer is replaced during a period of about 4 weeks.
- dandruff is this later flaking off from scalp
- callus forms when stratum corneum has frequent friction
b) LUCIDUM (clear layer) dead cell
- The stratum lucidum is a smooth, seemingly translucent layer of the epidermis
located just above the stratum granulosum and below the stratum corneum.
- This thin layer of cells is found only in the thick skin of the palms, soles, and digits.
I. Functions
1. Protection: Skin gives an anatomical barrier between the internal and external
environment in bodily defense; Langerhans cells in the skin are part of the immune
system; Protection of organs and tissues
2. Sensation: Skin contains a variety of nerve endings that react to heat, cold, touch,
pressure, vibration, and tissue injury
3. Heat regulation: The skin contains a blood supply far greater than its requirements
which allows precise control of energy loss by radiation, convection and conduction.
Dilated blood vessels increase perfusion and heat loss while constricted vessels
greatly reduce cutaneous blood flow and conserve heat. Erector pili muscles are
significant in animals; Regulation of body temperature
- muscle contraction
- movement of blood vessels
4. Sweat Excretion: Removal of waste products, water and organic compounds
5. Production of vitamin D (ergoesterol)
- happens in the kidney
- UV light stimulates production
Skin
- made up of a layer of tissues that guard underlying muscles and0 organs
- plays the most important role in protecting against pathogens
- insulation and temperature regulation, sensation and vitamin D and B synthesis
- weighs approximately 9lbs 0147
- Used to determine body fat
- normal skin cell cycle takes up around 40-56 days
- the stratum corneum 25 or more layers
I. Major layers of skin and its structures
The skin has two major layers which are made of different tissues and have very
different functions.
Skin is composed of the
a) epidermis
b) the dermis.
c) hypodermis - deeper subcutaneous tissue
note: Below these layers lies the hypodermis or subcutaneous adipose layer, which is not
usually classified as a layer of skin.
A. The OUTERMOST EPIDERMIS
- consists of stratified squamous keratinizing epithelium with an underlying
basement membrane
- has all of the shapes of the epithelial cell
- This layer of skin is responsible for keeping water in the body and keeping other
harmful chemicals and pathogens out.
, - The main type of cells which make up the epidermis are
keratinocytes,
melanocytes
Langerhans cells
- Cells are formed through mitosis at the innermost layers.
Note: They move up the strata changing shape and composition as they
differentiate, inducing expression of new types of keratin genes. They eventually
reach the corneum and become sloughed off (desquamation), this process is called
keratinization and takes place within about 30 days.
SPECIAL EPIDERMAL CELLS & STRUCTURES in the EPIDERMIS
keratinocytes (as they move up, they take in keratin)
- produce keratin
- taken by endocytosis
melanocytes
- produce melanin: pigment (big cells between epidermal cells)
hair
nail
Note:
Thick skin: no hair, sole, palm (all layers of epidermis is present here)
Thin skin: hairy part anything that is not the sole or palm (absent of lucidum)
can be further subdivided into the following strata (beginning with the outermost layer):
(a) Corneum
Lucidum -
Granulosum - (b) transition layers
Spinosum -
(c) Basale
a) CORNEUM (mostly dead cells)
- The stratum corneum is the most superficial layer of the epidermis
- the layer exposed to the outside environment
- 20-30 layers of dead squamous cells filled with keratin
- accounts for 75% of epidermal thickness
- This dry, dead layer helps prevent the penetration of microbes and the
dehydration of underlying tissues, and provides a mechanical protection against
abrasion for the more delicate, underlying layers.
- The entire layer is replaced during a period of about 4 weeks.
- dandruff is this later flaking off from scalp
- callus forms when stratum corneum has frequent friction
b) LUCIDUM (clear layer) dead cell
- The stratum lucidum is a smooth, seemingly translucent layer of the epidermis
located just above the stratum granulosum and below the stratum corneum.
- This thin layer of cells is found only in the thick skin of the palms, soles, and digits.
