A&P Accessory Structures of the Skin
Functions of the skin: Excretion and absorption
- Excretion: elimination of substances from the body - Absorption: passage of materials from the external environment into body cells - Transdermal drug administration
Functions of the skin: Protection
- Keratin - physical barrier - Lipids released by lamellar granules - prevent water loss and prevent water damage - Sebum - lubricate skin and hairs and antimicrobial action - Acidic sweat - reduces bacterial growth - Melanin - absorbs damaging UV - Macrophages - detect and fight invading organisms
Functions of the skin: Thermoregulation
- Regulating the production of sweat; sweat reduces body temperature via conduction - Regulating blood flow; blood flow to the dermis changes body temperature by changing heat conduction from blood to skin tissues
Eccrine Sweat Glands: Functions
- Regulation of body temperature - waste removal - stimulated during emotional stress
Functions of the skin: cutaneous sensations
- Tactile sensations: touch, pressure, vibrations, tickle - Thermal sensations: warm, cool - Pain
Functions of the skin: Synthesis of Vitamin D
- Ultraviolet rays activate the precursor molecule (calcitriol) that allows vitamin D to be made - Vitamin D aids in the absorption of calcium from foods in the gastrointestinal tract
Hair Growth: Growth Stage
- about 85% of hair is in this stage at any one point - cells in the hair matrix are dividing adding cells the hair medulla - 2-6 years
Hair Growth: Regression Stage
- cells in the hair matrix stop dividing - hair follicle atrophies and the hair stops growing - 2-3 weeks
Hair Growth: Resting Stage
- hair loss; ie hair falls out - the follicle (matrix) prepares to enter growth stage - 3 months
Sebaceous (Oil) Glands: Distribution
- largely in lips, glans penis, labia minora, and tarsal glands - small in trunk and limbs - absent in palms and soles
Types of hairs: Terminal
- long, coarse, heavily pigmented hairs - replaces lanugo hair after birth in eyelashes, eyebrows, and scalp
Epidermal wound healing
- occurs when superficial wounds affect only the epidermis
Hair color: Coloration
- permanency of stain depends on how deep the dye penetrates the hair shaft - does not change the melanin produced by melanocytes
Hair
- present in most body surfaces EXCEPT the palms and palmar surfaces of fingers as well as the soles and plantar surfaces of the feet - composed of dead, keratinized epidermal cells - genetic and hormonal influences determine the thickness and distribution of hair
Sebaceous (Oil) Glands: Functions
- prevents hairs from drying out - prevent water loss from skin - keep skin soft - inhibit growth of some bacteria
Hair color
- primarily due to the amount and type of melanin present in the keratinized cells of the hair - Eumelanin: brown to black - Phomelanin: yellow to red - loss of pigment production with age - grey hair: partial loss of melanin - white hair: full loss of melanin
Types of hairs: Vellus
- short, fine, pale hairs - Replace lanugo everywhere else in the body after birth - at puberty the surge of androgens changes vellus hairs into terminal hairs - pubic hair - axillary hair - facial hair - other parts of the body
The layers of the hair include:
- the cuticle - the cortex - the medulla
The parts of the hair include:
- the shaft (above the skin surface) - the follicle (below the level of the skin) - a root that penetrates into the dermis
This structure located in the epidermis serves as a tactile (touch) receptor.
Merkel cell (CORRECT) root hair plexus lamellar corpuscle Langerhans cell
Eccrine Sweat Glands: Location
Mostly in deep dermis (sometimes in upper subcutaneous layer) - excretes in the surface of the epidermis
Apocrine Sweat Glands: Location
Mostly in deep dermis and upper subcutaneous layer
Dermal wound healing
Occurs when an injury extends into the dermis and subcutaneous layer
Apocrine Sweat Glands: Secretion
Perspiration
Eccrine Sweat Glands: Secretion
Perspiration
Apocrine Sweat Glands: Onset of function
Puberty
Sebaceous (Oil) Glands: Onset of function
Relatively inactive during childhood; activated during puberty
Apocrine Sweat Glands: Distribution
Skin of axillae, groin, areolae, bearded regions of face, clitoris, and labia minora
Eccrine Sweat Glands: Onset of function
Soon after birth
Apocrine Sweat Glands: Functions
Stimulated during emotional stress and sexual excitement
Which of the statements below is true for both eccrine and apocrine glands?
Their sweat contains water, salts, proteins, and fats. They are involved in temperature regulation. They produce sweat. (CORRECT) They may have a pheromone-producing function.
What is TRUE about apocrine sweat glands?
They are distributed all over the body. They produce clear perspiration consisting primarily of water and salts. They are located predominantly in axillary and genital areas. (CORRECT) They are important in temperature regulation.
Eccrine Sweat Glands: Distribution
Throughout the skin of most regions of the body, especially skin of forehead, palms, and soles
Thinner hair may be lacking what structural component of a typical hair?
a) MEDULLA b) cortex c) cuticle d) root e) follicle
A skin graft would be needed if a person damaged the upper layers of the skin down to the stratum granulosum.
a) true b) FALSE
Types of hairs: Lanugo
covers the fetus
Sebaceous (Oil) Glands: Location
dermis, mostly connected to hair follicle
This accessory organ of the skin is composed primarily of dead, keratinized cells.
hair
The region beneath the free edge of the nail is called the ________.
hyponychium (CORRECT) nail bed eponychium lunule
This region of the nail is responsible for nail growth.
nail matrix (CORRECT) nail bed nail body nail root
The ducts of __________ glands usually empty into a hair follicle but may also open directly on the skin surface.
sebaceous
Sebaceous (Oil) Glands: Secretion
sebum - oily, waxy substance - waterproofs and lubricates the skin and hair of mammals
Functions of the skin: Blood reservoir
the dermis has so many blood vessels that it can hold about 8-10% of total blood flow while an adult is at rest
