Skin Overview

Question 0

What is the dermis?

Answer 0

Under the epidermis, consisting mostly of dense connective tissue. Two sublayers.

Question 1

What is the epidermis?

Answer 1

The most superficial layer of skin and is stratified keratinized squamous epithelium. Non-vascularized.

Question 2

What is the papillary layer of dermis?

Answer 2

Just beneath the epidermis and is the interface between the dermis and epidermis. Takes the form of small bumps or papillae.

Question 3

What is the reticular layer of dermis?

Answer 3

Just below the papllilary layer and is made mostly of dense bundles of collagen fibers and vascular serving the skin. Specialized sensory cells are here, also hair cells, sebaceous glands, and sweat glands.

Question 4

What is the hypodermis?

Answer 4

Found beneath the dermis. Also known as the superficial fascia. Technically not part of the skin, but because hair follicles, sweat glands and other structures are associated with the layer it is often included in discussion. Loose connective tissue with varying amounts of fat. Major blood vessels are here

Question 5

Appearance of the epidermis

Answer 5

Very dense and composed of mostly keratinocytes and multiple epidermal sublayers. Superficial layers are less stained (missing nuclei and organelles)

Question 6

Appearance of dermis

Answer 6

Stains well with eosin because of collagen fibers.

Question 7

Appearance of the papillary dermis

Answer 7

Thin collagen and elastic fibers and fibroblasts and a dense layer of capillaries to feed the epidermis and regulate temperature.

Question 8

Appearance of reticular dermis

Answer 8

More thick collagen and elastic fibers, fibroblasts.

Contains glands, hair follicles, and smooth muscle

Question 9

Appearance of hypodermis

Answer 9

Large accumulations of adipose and some profiles of sweat glands.

Question 10

5 layers of the epidermis from bottom to superficial

Answer 10

1. Stratum basale
2. Stratum spinosum
3. Stratum granulosum
4. Stratum lucidum
5. Stratum corneum

Question 11

Describe the stratum basale

Answer 11

Single cell layer, most mitotically active
Mainly responsible for keratinocyte turn over. When new cells are formed vi mitosis, the previous layer is pushed surface ward to join the next layer
Sits on top of the basement membrane and stains dark purple (hematoxylin)

Question 12

Describe the stratum spinosum

Answer 12

Superficial to the stratum basale. Several layers thick and has many mitotically active cells. Thickest epidermal layer. Adjacent cells are connected by strong adhering junctions and when dehydrated have a somewhat spiny appearance. Keratinocytes with numerous processes are responsible for this spiny appearance.

Question 13

What is the stratum granulosum?

Answer 13

Superficial to the stratum spinosum. Usually 3-5 cell layers thick and is darkly stained with basophilic granules. These granules are secretory and contribute to the water tight features of this epithelium. Most superficial cell layer of the epidermis in which cell nuclei and organelles are found.

Question 14

What is the stratum lucidum?

Answer 14

Present only in thick skin (palms of hands and soles of feet), cells devoid of nuclei and organelles. Densely packed keratin filaments and eleidin

Question 15

What is the stratum corneum?

Answer 15

Most superficial layer which consists of essentially dead cells, but still retain their plasma lemmae with intercellular junctions and cytoplasmic keratin.
Several layers of flattened, keratinized dead cells.
Continually being sloughed off, producing dandruff, and dust

Question 16

Mitotically active layers of the epidermis

Answer 16

Stratum basale ad stratum spinosum

Question 17

What are keratinocytes?

Answer 17

Stratified squamous epithelial cells. All layers of the epidermis produce keratin, a fibrous protein. Basal layer is mostly cuboidal to columnar and become more cuboidal as they move toward the surface. Eventually become flattened to look squamous

Question 18

What is the most plentiful cell type in the epidermis?

Answer 18

Keratinocytes

Question 19

What are melanocytes?

Answer 19

Located in the basal layer and partially the spiny layer and produce and release melanin

Question 20

What are Merkel’s cells?

Answer 20

Differntiated epithelial cells that serve as sensory in sense of touch. Contacted by sensory axons known as afferent axons.

Question 21

What are Langerhans cells?

Answer 21

Located in the stratum spinosum. Mesodermally derived cells that are part of the immune system. Are mobile and serve as antigen detecting and antigen presenting cells.

Question 22

Two components of barrier function in the skin?

Answer 22

Formation of keratin

Formation of glycolipids

Question 23

What is the barrier function of skin?

Answer 23

Keratin is an intermediate intracellular tonofilament.
Start to form the precursor keratin proteins in the stratum spinosum.
In the stratum granulosum, large keratohyaline granules and membrane coating granules of glycolipids join to form hydrophobic layer.
Glycolipid is mortar between keratin structural support

Question 24

What are lamellar bodies?

Answer 24

Membrane coating glycolipid granules

Question 25

Keratohyalin granules stain?

Answer 25

Dark purple in the stratum granulosum

Question 26

Describe the formation of soft keratin in the stratum corneum

Answer 26

Formation of tonofibrils/tonofilaments in the Str. basale and spinosum
Tonofibrils (tonofilaments) in the Str. granulosum.
Formation of keratohyaline granules in the upper str. spinosum
Keratohyaline granules in the str. granulosum
Combination of the tonofibrils and keratohyaline in the Str. granulosum. Produces soft keratin int he str. corneum.

Question 27

What is thick skin?

Answer 27

Thickness of epidermis
Shows all 5 layers of the epidermis (inc. the stratum lucidum, str. corneum is much thicker)
Found on the palms of hands and soles of feet
No melanocytes
Lacks hair follicles and sebaceous glands, but has sweat glands
Also termed glaborus or non-hairy skin

Question 28

What is thin skin?

Answer 28

Lacks str. lucidum
Thinner str. corneum
May have thick dermis
Has hair follicles, arrector pili muscles, sebaceous and sweat glands
Also termed hairy skin
Covers most surfaces

Question 29

What are melanocytes?

Answer 29

Neural crest derived cells that produce melanin pigment.
Have long dendrite like structures that reach out and contact many adjacent keratinocytes.
Transfer melanin to adjacent keratinocytes.
Stimulated by UV, same numbers across all races just expressed more.

Question 30

Where are mealoncytes found?

Answer 30

Seen in the stratum basale and the deeper part of the stratum spinosum, but not more superficially.