Unit 1 Topic 3 Flashcards
Epidermis Description
top layer of skin composed of simple squamous epithelium
Epidermis features
-5 layers: Stratum Basale, Stratum Spinosum, Stratum Granulosum, Stratum Lucidieum, Stratum Corneum
-contains keratinocytes, melanocytes, langerhans cells and merkel cells
Dermis Description and Features
-2 layers: Papillary and Reticular
-Papillary: loose CT; contain dermal papillae with BVs that support the epidermis; includes type I and II collagen and some elastic fivers
-Reticular: DICT with net like fibers; contains elastic for flexibility and more type I collagen for strength
Hypodermis Description and Features
deep to dermis; contains adipose tissue
Stratum Basale Features
-single layer that rests on the basal lamina
-only mitotically active epidermal layer
-contains stem cells that give rise to keratinocytes
-anchored to the basal lamina by hemidesmosomes and to the other cells by desmosomes
Stratum Spinosum Description
-several layers thick
-cytoplasmic processes (spines) composed of desmosomes
-As cells move to the surface they increase in size and flatten
Stratum Granulosum Features
-most superficial nonkeratinized layer
-contains basophillic keratohyalin granules in lamellar bodies that are exocytosed to create a barrier to water
Stratum Lucidum Features
-Normally only seen in thick skin
-advanced keratinization of cells leads to difficulty staining
-considered a subdivision of corneum by some
Stratum Conreum Features
-Stratum granulosum cells flatten (desquamate), desiccate (dry out), and undergo apoptosis as they reach the stratum corneum
-Loss of nucleus and cytoplasmic organelles and almost entirely composed of keratin filaments
-contain most mature keratinocytes
Keratinocytes Functions
-primary cell type of epidermis
-creation of extracellular water barrier between the stratum granulosum and corneum
Keratinocytes Features
-desmosomal attachments to neighboring keratinocytes throughout the epidermis
-continuously being lost and replaced by stem cells within the stratum basale
Melanocytes Functions
-present in the stratum basale and hair follicles
-produce melanin pigment from tyrosine that offers protection to the basal cells from UV radiation
Melanocytes Features
-melanin is internalized by keratinocytes
-attached to basal lamina, but not neighboring keratinocytes
-determines skin color
Langerhans Cells Functions
-phagocytic immune cells that serve as antigen presenting cells
Langerhans Cells Features
-found in the stratum spinosum
-continuously being replaced by monocytes
-cannot be distinguished by H and E
Merkel Cells Functions
-modified epidermal cells
-associated with free nerve endings-sensory mechanoreceptors and may secrete local neuroendocrine secretions
Merkel Cells Features
-found in basal layer, but prevalent in thick skin
-modified epidermal cells
Sweat Glands Description
-2 Types: Eccrine and Apocrine
-Eccrine: distributed across the entire body, except lips and external genitalia
-Apocrine: distribution limited to the axilla, areola/nipple of mammary glands, the skin surrounding the anogenital region, and eyelashes
Sebaceous Glands Description
-holocrine secretion of sebum into the canal associated with the hair follicle
-Appear clear due to the high lipid content
Sebaceous Glands Functions
-dead cells are replaced by the proliferation of basal cells
-secretions are bacteriostatic and may act as an emollient, lubricant, barrier, and pheromone
Nails Description
-keratinized cells containing hard keratin
-Eponychium (cuticle): skin covering over the root
-Hyponychium (quick): secured free edge of nail at the fingertips
Hair Description
present all over body except for sides and palmar surface of hand, sides and plantar surfaces of foot, lips and region around urogenital orifces, but distribution depends on hormones/genetics; color is determined by melanin content
Hair Follicles Description
invaginations of epithelium into dermis; responsible for production/growth of hair; living cells that contribute to hair from the proximal attachment
Layers of the Hair Follicles
internal root sheath (innermost), external root sheath, glassy membrane, outermost CT root sheath
-hair bulb: proximal expansion
Dermal Papilla
invagination of bulbs by vascularized loose CT
Free Nerve Endings
epidermis and dermis; pain and temperature
Messiner’s Corpuscles
dermis only; tactile
Pacinian Corpuscles
dermis and hair suit; pressure
Ruffini’s Corpuscles
dermis only; mechanical displacement and stretching
Merkel Cell
epidermis only; tactile
What is the method of apocrine swat gland secretion?
simple coiled glands composed of secretory and myoepithelial cells → Merocrine secretions into ducts → secretions function as pheromones
What are the steps of skin regeneration?
-Coagulation/Inflammation: scab forms
-Granulation Stage: collagen and ECM are deposited to stabilize wound; reestablisment of blood vessels
-Remodeling Stage: type III collagen is replaced with stronger type I collagen to form a scar
Fibroblasts and inflammatory cells are degraded
Myofibroblasts allow contraction of wound
Epidermis is replenished
What is the difference between light and dark skin structure?
the only difference in light and dark skin is the type/amount of melanin that is produced by melanocytes
