TOPIC: Epidermal Skin Layers OBJ: 1-4

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HW:5.2 Epidermal Identification Poster DUE: Friday

DO NOW: 10- What are the two layers of skin?

HANDOUTS to PICK-UP:

-Poster

-Divider/Objectives

-Notes: 5.1-5.2

-Epidermal cell worksheet

-5.2 Epidermis PosterREMINDER(s)-Job Shadow/Volunteer Deadline 10/14-Permission slip & Blue pamphlet Due 9/20

Add on to each QUESTION every night as REVIEW

5.1- LAYERS of the SKIN

1-Po -DISCUSS the basic structure and characteristics of the skin.

2-Po -EXPLAIN the role of the subcutaneous layer.

5.2- EPIDERMIS

3-Po -DESCRIBE the functions and composition of the layers of the epidermis.

4-Po -SKETCH and DISCUSS the 4 types of cells in the epidermis.

Why This Matters

• Understanding the integumentary system will help you evaluate

and treat injuries to the skin such as burns

© 2016 Pearson Education, Inc.

Integumentary System

• Integumentary system consists of:

– Skin

– Hair

– Nails

– Sweat glands

– Sebaceous (oil) glands

© 2016 Pearson Education, Inc.

Functions of Integumentary System

1. Protection

2. Defense/immunity

3. Insulation

4. Receptor

5. Homeostasis

6. Excretes waste

7. Vitamin D synthesis

© 2016 Pearson Education, Inc.

5.1 Structure of skin

• Skin consists of two distinct regions:

– Epidermis: superficial region

•Consists of epithelial tissue and is avascular

– Dermis: underlies epidermis

•Mostly fibrous connective tissue, vascular

– Hypodermis (superficial fascia)

• Subcutaneous layer deep to skin

•Not part of skin but shares some functions

•Mostly adipose tissue that absorbs shock and insulates

•Anchors skin to underlying structures: mostly muscles

© 2016 Pearson Education, Inc.

Figure 5.1 Skin structure.

© 2016 Pearson Education, Inc.

Hair shaft

Dermal papillaeEpidermis

Papillarylayer

SubpapillaryplexusSweat pore

Appendages of skin• Eccrine sweat gland• Arrector pili muscle• Sebaceous (oil) gland• Hair follicle• Hair root

Dermis Reticularlayer

Hypodermis(subcutaneoustissue; not partof skin)

Cutaneous plexusNervous structures• Sensory nerve fiber

with free nerve endings• Lamellar corpuscle• Hair follicle receptor

(root hair plexus)

Adipose tissue

5.2 Cells of the Epidermis

• Epidermis consists mostly of keratinized stratified squamous

epithelium

• Four cell types found in epidermis:

1. Keratinocytes

2. Melanocytes

3. Dendritic (Langerhans) Cells

4. Tactile (Merkel) Cells

© 2016 Pearson Education, Inc.

You don’t have to write these down-I will give you a chart with this

information!

5.2 CHART-Highlighting

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5.2 CHART

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Layers of the Epidermis

• Epidermis is made up of four or five distinct layers

– Thick skin - five layers

– Thin skin - four layers

• Five layers of skin

1. Stratum basale

2. Stratum spinosum

3. Stratum granulosum

4. Stratum lucidum (only in thick skin)

5. Stratum corneum

© 2016 Pearson Education, Inc.

5.2 Layers of Epidermis

Layers of the Epidermis (cont.)

1. Stratum basale (basal layer)

– Deepest of all epidermal layers (base layer)

– Layer that is firmly attached to dermis

– Consists of a single row of stem cells producing two daughter cells each

time

• One daughter cell journeys from basal layer to surface, taking 25–45 days to reach

surface

– Cell dies as it moves toward surface

• Other daughter cell remains in stratum basale as stem cells

– Layer also known as stratum germinativum because of active mitosis

– 10–25% of layer also composed of melanocytes

© 2016 Pearson Education, Inc.

5.2 Layers of Epidermis-Stratum Basale

Layers of the Epidermis (cont.)

2. Stratum spinosum (prickly layer)

– Several [8-12] cell layers thick

– Cells contain weblike system of intermediate prekeratin filaments

attached to desmosomes

•Allows them to resist tension and pulling

– Keratinocytes in this layer appear spikey, so they are called prickle cells

– Scattered among keratinocytes are abundant melanosomes and dendritic

cells

© 2016 Pearson Education, Inc.

5.2 Layers of Epidermis-Stratum Spinosum

Layers of the Epidermis (cont.)

3. Stratum granulosum (granular layer)

– Four to six cells thick, but cells are flattened, so layer is thin

– Cell appearance changes

•Cells flatten, nuclei and organelles disintegrate

•Keratinization begins

– Cells above this layer die

•Too far from dermal capillaries to survive

© 2016 Pearson Education, Inc.

5.2 Layers of Epidermis-Stratum Granulosum

Layers of the Epidermis (cont.)

4. Stratum lucidum (clear layer)

– Found only in thick skin

– Consists of thin, translucent band of two to three rows of clear, flat,

dead keratinocytes

– Lies superficial to the stratum granulosum

© 2016 Pearson Education, Inc.

5.2 Layers of Epidermis-Stratum Lucidum

Layers of the Epidermis (cont.)

5. Stratum corneum (horny layer)

– 20–30 rows of flat, anucleated, keratinized dead cells

– Accounts for three-quarters of epidermal thickness

– Though dead, cells still function to:

•Protect deeper cells from the environment

•Prevent water loss

•Protect from abrasion and penetration

•Act as a barrier against biological, chemical, and physical assaults

© 2016 Pearson Education, Inc.

5.2 Layers of Epidermis-Stratum Corneum

Figure 5.2 Epidermal cells and layers of the epidermis.

© 2016 Pearson Education, Inc.

Keratinocytes

Stratum corneum

Most superficial layer; 20–30 layers of deadcells, essentially flat membranous sacsfilled with keratin. Glycolipids inextracellular space.

Stratum granulosumTypically one to five layers of flattenedcells, organelles deteriorating; cytoplasmfull of lamellar granules (release lipids) andkeratohyaline granules.

Stratum spinosumSeveral layers of keratinocytes unified bydesmosomes. Cells contain thick bundlesof intermediate filaments made ofpre-keratin.

Stratum basaleDeepest epidermal layer; one row of activelymitotic stem cells; some newly formed cellsbecome part of the more superficial layers.See occasional melanocytes and dendriticcells.

Dermis Melanin

granule

Dermis

Sensorynerveending

Tactile

(Merkel)

cell

Desmosomes Dendritic cellMelanocyte

Layers of the Epidermis (cont.)

1-Which layer of the skin-dermis or epidermis-is better

nourished? Why?

-dermis

CHECKING FOR UNDERSTANDING

Layers of the Epidermis (cont.)

2-Which epidermal cell is more numerous?

a. Keratinocyte

b. Melanocyte

c. Dendritic cell

d. Tactile cell

-keratinocyte

CHECKING FOR UNDERSTANDING

Layers of the Epidermis (cont.)

3-The stratum basale is also called the stratum

germinativum, a name that refers to its major function.

What is that function?

-continuous mitosis to replace cells lost due to abrasion

CHECKING FOR UNDERSTANDING

Layers of the Epidermis (cont.)

4-Why are the desmosomes connecting the keratinocytes so

important?

-The skin is subjected to a lot of abrasion and physical

trauma. The desmosomes, which are connecting junctions,

help to hold the cells together during such stress.

CHECKING FOR UNDERSTANDING

Layers of the Epidermis (cont.)

Directions

-Must use Crayons or Colored Pencils ONLY

-Color AND Label any necessary parts [include corresponding number]

-be sure to answer questions with written answer when necessary

-reference your notes to locate various cells

5.2 Epidermis Identification Poster

Layers of the Epidermis (cont.)

EX: Let’s do one together-you pick!