C5 1-6 Flashcards
Stratum Basale/germanitivum
- layer of cuboidal/columnar cells - high metabolic needs and most dependent on blood supply from dermis.
- Basal cells (which supply all new keratinocytes) dominate this stratum. Also contains Merkel cells (touch) and melanocytes.
- Germanitivum interlocks with the underlying dermis
Stratum Corneum
- 15-30 layers of keratinized cells create a barrier (prevent water loss and pathogen/chemical entry, desmosomes also key to barrier)
- Dead cells of corneum remain here for about two weeks before they are shed.
- corneum is water resistant
What factors contribute to skin color?
Melanin, Carotene, hemoglobin, illnesses
How does melanin affect skin color?
Granules of melanin are packed into melanocytes and are transferred to surrounding keratinocytes where they act as umbrellas to protect the nucleus of cells. It is the type and amount of melanin that account for the majority of skin color variation. Eumelanin/pheomelanin - brown/black-reddish
How does carotene affect skin color?
A yellow/orange pigment found in certain plants, carotene can accumulate in the stratum corneum and fatty tissue of the hypodermis.
How does hemoglobin affect skin color?
In caucasians, the epidermis is nearly transparent so hemoglobin’s color can show through. (crimson)
How does illness affect skin color?
Cyanosis/poorly oxygenated blood = blue, Erythema = red, Anemia/low bp/fear = pallor, Jaundice = yellow Bruise = black/blue
- Describe the importance and the process of keratinzation. Where does it occur?
In the stratum granulosum. Cells get pushed up and as they get further from their nutrient source they die. The maturing cells undergo a hardening process (keratinization) during which the cytoplasm develops strands of tough, fibrous, waterproof proteins called keratin. These dead cells form many tough, waterproof layers.
- Describe the importance of keratinzation.
The importance of keratinization is the protective property it gives skin.
Keratinization - Where does it occur?
In the epidermis
Papillary layer of dermis
Tissue type: areolar ct.
Structures: lots of small blood vessels, dermal papillae indenting into the epidermis, sweat and oil glands, hair follicles lymph vessels, sensory nerves
Reticular layer of dermis
Tissue type: dense irregular ct.
Structures: collagen/elastin, accessory structures start here: hair, nails, glands
- Describe how dermal blood vessels function in temperature regulation.
Vasoconstriction constricts blood vessels and slows passive heat loss, vasodilation widens blood vessels increasing passive heat loss.
Papilla
Small, nipple-like projection; dermal papillae are projections of dermal tissue into the epidermis
Structure of Dermis
Layer of skin deep to the epidermis; STRUCTURE: papillary layer (areolar ct) and reticular layer (dense irregular, 80%) Vascular and innervated. 4mm
Function of Dermis
mechanical strength (but also elastic)
reservoir for water and minerals,
supplies itself and epidermis with blood,
temperature regulation,
houses: blood vessels/sweatglands/sebaceous glands/hair follicles/nail roots
Keratin
Tough, fibrous protein found in the epidermis, hair, and nails that makes those structures hard and water resistant; precursor is keratohyaline
Melanin
Dark pigment formed by cells called melanocytes; imparts color to skin and hair
integumentary system
Skin and its derivatives; provides the external protective covering of the body
Epidermis
Superficial layer of the skin; composed of keratinized stratified squamous epithelium. Avascular but innervated.
Cutaneous membrane
Epidermis and dermis, Skin. (cutaneous = pertaining to the skin)
Subcutaneous tissue/layer structure/function
(tissue beneath the skin) aka hypodermis/superficial fascia. FUNCTION: Forms a connection between skin and underlying structures. STRUCTURE: Mostly loose areolar and adipose, also blood vessels and nerves.
Fascia/deep fascia
General term for the fibrous ct masses in different locations in the body. Fascia binds together the structures of the body with many collagenous fibers arranged irregularly (fascia under the skin is mostly adipose)
Deep fascia: dense reg that wraps around blood vessels, muscles, organs
What cells are associated with the epidermis?
Keratinocytes, melanocytes, merkel cells, langerhan’s cells
Keratinocytes
- Epidermis,
- function in protection,
- 90% of epidermal cells filled with keratin,
- keratinocytes secrete interleukin (influence t cells), first three layers of epidermis are living
- keratinocytes/2 superficial layers are dead keratinocytes
- FUNCTION: protection
Melanocytes
5% of epidermal cells, FUNCTION: protect by absorbing UV light b4 it hits the nucleus of keratinocytes
Merkel cells
Tactile cell associated with a nerve ending. FUNCTION: protect by sensing environment
Langerhan’s cells
Ingest foreign substances/activate immune system FUNCTION: protect by looking for foreign protein
Discuss the evolution of skin color.
Darker skin at equator where more protection from sun is needed/lighter skin further from equator where less protection is needed. Melanocytes protect and give skin color, darker skin has produced and retained more melanin.
