Exam 3: skin Flashcards
What are exocrine glands composed of?
Epithelial tissue
Types of skin glands
Sebaceous gland
Sudoriferous gland
Ceruminous gland
Mammary gland
Which gland typically release oil into the hair follicle?
Sebaceous gland (sebace=greasy)
This substance prevents dehydration and inhibits bacterial growth. It is made mainly of triglycerides and cholesterol.
Sebum
Which gland releases sweat to surface (via pore) or into hair follicles and regulates body temperature via homeostasis?
Sudoriferous glands (sudori = sweat; ferous = bearing)
Deep layer of the skin and have mainly connective tissue, with embedded blood vessels,nerve glands and hair follicles.
Dermis
Two main regions of the dermis
Papillary region and reticular region
Papillary region
Superficial
Thin (relative to reticular region)
Dermal papillae (papillae = nipple) project into epidermis, supplying it with blood vessels and nerves
Reticular region
Deep
Thick (relative to papillary region)
Many collagen and elastic fibers for extensibility and elasticity
Location of thick skin
Palms, fingertips, and soles
Structure of thick skin
5 layers in epidermis
Hair absent
Many sensory receptors
Epidermal ridges present
Location and structure of thin skin
Everywhere else
4 layers of epidermis
Few sensory receptors
Epidermal ridges absent
Increase surface area of epidermis for better grip, reflect contours of underlying dermal papillae, and are the basis for fingerprints (and footprints)
Epidermal ridges
What are the pigments that produce skin color?
Melanin
Hemoglobin
Carotenes
Pigment that is synthesized by melanocytes in epidermis and transferred to keratinocytes
Melanin
Why is melanin transferred to keratinocytes?
It accumulates above nucleus to shield nucleus from UV radiation in sunlight
Two forms of melanin
Pheomelanin (yellow to red)
Eumelanin (brown to black)
Pigment found within red blood cells in capillaries of dermis that shows through if there is little melanin; red-colored
Hemoglobin
A dietary pigment that can accumulate in stratum corneum and subcutaneous adipose tissue; orange colored
Carotenes
Accessory structures of the skin
Hair
Nails
Skin glands
Also called pilus/pili
Hair
Structure of hair
- Columns of dead keratinizes cells held together by extracellular proteins
- Shaft extends above surface of skin
- Root penetrates epidermis and dermis
Base of the hair follicle
Bulb
Bulb consists of:
Epithelial root sheath
Dermal root sheath
Epidermal tissue around hair root
Epidermal root sheath
Dermal tissue around hair root
Dermal root sheath
Structures associated with hair follicle
Papilla of hair Hair matrix Sebaceous glands Arrector pili Hair root plexuses (branching network of nerves)
Supplies hair follicle with blood vesicles
Papilla of the hair
Layer of epithelial stem cells that give rise to the hair and are derived from stratum basale. It is responsible for growth of existing hair and production of new hair
Hair matrix
Produces and secrete oil
Sebaceous glands
Smooth muscle associated with follicle and pulls hair upright
Arrector pili
Neurons sensitive to tactile stimuli (ex: feeling slight brush on arm hair)
Hair root plexuses
Where does the melanocytes occur?
Hair matrix
Hair color depends on what?
Amount and type of melanin in keratinized cells
Composed of tightly packed, dead, keratinized epidermal cells
Nails
Responsible for nail growth
Nail matrix
Two types of sudoriferous glands
Eccrine sweat glands
Apocrine sweat glands
Eccrine sweat glands
Located across body surface
Help to cool the body
Apocrine sweat gland
Located in axilla (armpit), groin, areolae, and bearded facial regions
Secrete sweat during emotional stress or sexual excitement (haha..)
Modified sweat glands that are located in external ear and produces a waxy secretion
Ceruminous glands
Combined secretions of ceruminous and sebaceous glands in ears
Cerumen (earwax)
Functions of the skin
Thermoregulation Protection Cutaneous sensations Excretion and absorption Synthesis of vitamin D
What are the two mechanisms of thermoregulation?
- Secreting sweat
- Adjusting blood flow to dermal capillaries by dilation and constriction of capillaries
The skin protects by:
Physical barrier to invasion by pathogens
Physical protection from abrasion, heat, and some toxic chemicals
Lipids in epidermis retard dehydration
Protection from UV radiation (melanins)
What are the cutaneous sensations?
Tactile sensation
Thermal sensation
Pain
How is water lost in skin?
By evaporation of water across skin and via sweat
What are excreted along with water by skin?
Sal amounts of salts, CO2, ammonia, and urea and some lipid-soluble substances
Describe the synthesis of vitamin D
Precursor molecule of vitamin D activated by exposure to UV radiation in skin
Precursor molecule then modified in liver and kidneys to produce calcitriol (a form of vitamin D)
