L22. Skin

Question 1

Name characteristics of the skin

Answer 1

1. largest organ in the body
2. waterproof and protective
3. regulates body temperature
4. sensory receptors for pain, pressure and touch

Question 2

What are the 2 layers of the skin

Answer 2

1. epidermis

2. dermis

Question 3

Describe the epidermis

Answer 3

1. stratified squamous keratinized epithelium
2. contains specialized cell types
   - Merkel cell
   - Langerhan cells
   - melanocytes
3. gives rise to specialized skin appendages
   - sebacous and sweat glands
   - hair follicles

Question 4

Where is the epidermis derived from ( which germ layer)

Answer 4

ectoderm

Question 5

Which germ layer is the dermis derived from

Answer 5

mesoderm

Question 6

Describe the dermis

Answer 6

1. underlying layer of dense irregular connective tissue
2. blood vessels
3. sensory nerves
   - temperature, pain, touch ( Meisner’s corpuscles)
   - deep pressure sensors ( Pacinian corpuscles)

Question 7

What are Pacininan Corpuscles , and where are they found

Answer 7

deep, reticular layer of the dermis

Question 8

What are the Meisner corpuscles, where are they located

Answer 8

pain, temperature and touch receptors, located at dermal ridges which are the papillae

Question 9

What is the hypodermis

Answer 9

loose Connective tissue and adipose tissue

Question 10

What is the function of the hypodermis

Answer 10

connects skin to underlying tissue and organs

Question 11

Identify all structures on page 3 of L21. ( draw the stratum corneum , stratum spinosum and stratum basale)

Answer 11

pg 3 L 21

Question 12

Identify all features of the epidermis

Answer 12

pg 4 L 21

Question 13

What are the 5 layers of the epidermis ( name from outer to inner)

Answer 13

1. stratum coneum
2. stratum lucidum
3. stratum granulosum
4. stratum spinosum
5. stratum basale

Question 14

Describe the stratum basale

Answer 14

1. stem cells that are undifferentiated
2. high mitotic activity
3. cell-cell adhesions with desomosomes
4. cubodial to low columnar epithelial cells/keratinocytes
5. hemidesmosomes at cell-basement membrane interface of the stem cell phenotype
6. as the basal keratinocytes move up the stratum layer they begin to differentiate
7. contains melanocytes and merkel cells

Question 15

Why are hemisdesmosomes important in the stratum basale

Answer 15

1. needed for attachment of epidermis to dermis layer

2. maintain stem cell phenotype

Question 16

What is the function of melanocytes? Describe the melanocytes

Answer 16

• produce skin pigments
• are neural crest derived
• migrate into epidermis where they reside in the basale

Question 17

What are the functions of the Merkel cell? Describe their function

Answer 17

mechno/touch receptors, are neural-crest derived. migrate into the epidermis and reside in the stratum basale

Question 18

Describe the stratum spinosum

Answer 18

1. are differentiated epithelial keratinocytes
2. cells begin to produce large numbers of tonofilaments
3. desmosomes are prominent in the cell-cell interaction points at the end of the small keratinocyte cell-processes

Question 19

What are tonofilaments

Answer 19

keratin intermediate fibers

Question 20

What are lagerhan cells

Answer 20

1. antigen producing cells
2. migrate into the epidermis , reside in the stratum spinosum layer
3. hematopoietic stem cell derived

Question 21

Describe the stratum granulosum

Answer 21

1. cells begin to fully differentiate and become squamous
2. lipid rich vesicles/granules are made and secreted between s. granulosum and s. lucidum
3. produce proteinacious ‘keratohyaline’ that forms cytoplasmic ‘granules’ (not membrane-bound/vesicular) cross links the tonofilament

Question 22

Describe the stratum lucidum

Answer 22

1. last layer of living cells
2. above the water proof layer this cells fully differentiate to produce ‘eleidin’ a protein that aligns cross-linked keratin tonofilaments in // arrays
3. cells above water proof layer begin to die and lose their nuclei

Question 23

Describe the stratum corneum

Answer 23

1. enucleate flat cells that are already dead
2. filled with protective cross-linked and bundled keratinized filaments =squames
3. desmosomes deteriorate ; squames are slough-off/released =desquamated

Question 24

What ar squames?

Answer 24

protective cross linked and bundled keratinized filaments

Question 25

Where is the S. Cornuem and S. Lucidum most prominent ?

Answer 25

In soles of feet and palms ( no hair follicles)

Question 26

Describe the hair follicle

Answer 26

1. invagination of the epidermis that pushes down into the dermis 2. follicle terminates at the hair root which is indented by the dermal papilla which supplies blood vessels and nerves to the area of the hair root. 3. the outer external root sheath of the hair follicle consists of a modified stratum basale and stratum spinosum 4. inner internal root sheath of hair follicle consists of differentiating stratum grnulosum-like cells ( they are orderly arranged , move inwards and die to produce the hair shaft )

Question 27

Describe the sebacous gland

Answer 27

1. forms as an outpouching of the hair follicle epidermis above the hair bulb. 2. secretory portion is alveolar 3. secretes sebum ( pale staining on HE) 4. mode of secretion is by necrosis ( death of cell to release all contents) 5. ducts may branch slightly and empty into the hair canal

Question 28

How does acne form?

Answer 28

obstruction of sebacous glands' ducts leads to bacteria infection -> acne

Question 29

Where is the hair canal?

Answer 29

small space between the fully formed hair shaft and follicular epithelium

Question 30

What are arrector pilli

Answer 30

smooth muscle fibers that anchor to the dermal connective tissue that surrounds the hair follicle - under autonomic control - generate raised hair

Question 31

Draw the structure of the hair ( pg14 L 22)

Answer 31

pg 14 L22

Question 32

Describe the eccrine sweat glands

Answer 32

1. simple coiled tubular glands that form as invaginations of the epidermis 2. widely distributed in the skin; secrete sweat with a slight mucous content by regular polarized , exocytosis based secretion 3. secretory portion of tubules, have contractile cells which are ectodermally derived 4. contractile cells help to expel secretory products into ducts efficiently

Question 33

Where are myoepithelial cells found

Answer 33

present in mammary gland