Unit 1 Topic 3

Question 1

Epidermis Description

Answer 1

top layer of skin composed of simple squamous epithelium

Question 2

Epidermis features

Answer 2

-5 layers: Stratum Basale, Stratum Spinosum, Stratum Granulosum, Stratum Lucidieum, Stratum Corneum
-contains keratinocytes, melanocytes, langerhans cells and merkel cells

Question 3

Dermis Description and Features

Answer 3

-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

Question 4

Hypodermis Description and Features

Answer 4

deep to dermis; contains adipose tissue

Question 5

Stratum Basale Features

Answer 5

-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

Question 6

Stratum Spinosum Description

Answer 6

-several layers thick
-cytoplasmic processes (spines) composed of desmosomes
-As cells move to the surface they increase in size and flatten

Question 7

Stratum Granulosum Features

Answer 7

-most superficial nonkeratinized layer
-contains basophillic keratohyalin granules in lamellar bodies that are exocytosed to create a barrier to water

Question 8

Stratum Lucidum Features

Answer 8

-Normally only seen in thick skin
-advanced keratinization of cells leads to difficulty staining
-considered a subdivision of corneum by some

Question 9

Stratum Conreum Features

Answer 9

-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

Question 10

Keratinocytes Functions

Answer 10

-primary cell type of epidermis
-creation of extracellular water barrier between the stratum granulosum and corneum

Question 11

Keratinocytes Features

Answer 11

-desmosomal attachments to neighboring keratinocytes throughout the epidermis
-continuously being lost and replaced by stem cells within the stratum basale

Question 12

Melanocytes Functions

Answer 12

-present in the stratum basale and hair follicles
-produce melanin pigment from tyrosine that offers protection to the basal cells from UV radiation

Question 13

Melanocytes Features

Answer 13

-melanin is internalized by keratinocytes
-attached to basal lamina, but not neighboring keratinocytes
-determines skin color

Question 14

Langerhans Cells Functions

Answer 14

-phagocytic immune cells that serve as antigen presenting cells

Question 15

Langerhans Cells Features

Answer 15

-found in the stratum spinosum
-continuously being replaced by monocytes
-cannot be distinguished by H and E

Question 16

Merkel Cells Functions

Answer 16

-modified epidermal cells
-associated with free nerve endings-sensory mechanoreceptors and may secrete local neuroendocrine secretions

Question 17

Merkel Cells Features

Answer 17

-found in basal layer, but prevalent in thick skin
-modified epidermal cells

Question 18

Sweat Glands Description

Answer 18

-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

Question 19

Sebaceous Glands Description

Answer 19

-holocrine secretion of sebum into the canal associated with the hair follicle
-Appear clear due to the high lipid content

Question 20

Sebaceous Glands Functions

Answer 20

-dead cells are replaced by the proliferation of basal cells
-secretions are bacteriostatic and may act as an emollient, lubricant, barrier, and pheromone

Question 21

Nails Description

Answer 21

-keratinized cells containing hard keratin
-Eponychium (cuticle): skin covering over the root
-Hyponychium (quick): secured free edge of nail at the fingertips

Question 22

Hair Description

Answer 22

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

Question 23

Hair Follicles Description

Answer 23

invaginations of epithelium into dermis; responsible for production/growth of hair; living cells that contribute to hair from the proximal attachment

Question 24

Layers of the Hair Follicles

Answer 24

internal root sheath (innermost), external root sheath, glassy membrane, outermost CT root sheath
-hair bulb: proximal expansion

Question 25

Dermal Papilla

Answer 25

invagination of bulbs by vascularized loose CT

Question 26

Free Nerve Endings

Answer 26

epidermis and dermis; pain and temperature

Question 27

Messiner's Corpuscles

Answer 27

dermis only; tactile

Question 28

Pacinian Corpuscles

Answer 28

dermis and hair suit; pressure

Question 29

Ruffini's Corpuscles

Answer 29

dermis only; mechanical displacement and stretching

Question 30

Merkel Cell

Answer 30

epidermis only; tactile

Question 31

What is the method of apocrine swat gland secretion?

Answer 31

simple coiled glands composed of secretory and myoepithelial cells → Merocrine secretions into ducts → secretions function as pheromones

Question 32

What are the steps of skin regeneration?

Answer 32

-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

Question 33

What is the difference between light and dark skin structure?

Answer 33

the only difference in light and dark skin is the type/amount of melanin that is produced by melanocytes