Human A&PBIO 304 · American River College ← Week 2 pre-work

BIO 304 · Week 2 · Interactive Workbook

Skin Structure and Layers

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Part 1 of 4 · Recall

Fill in the blanks

Type the term that completes each statement, using the word bank. Pull it from memory first.

Word bank

Stratum corneumStratum lucidumStratum granulosumStratum spinosumStratum basalePapillary dermis (superficial)Reticular dermis (deep)Hypodermis (subcutaneous)

  1. Anucleate keratin sheets: dead keratinocytes packed with keratin. Waterproof barrier.
  2. Thick skin only: palms and soles. Translucent dead cells.
  3. Keratohyalin granules: keratinocytes start dying here, releasing lipids that seal the barrier.
  4. “Prickly” desmosomes: keratinocyte cohesion plus dendritic cells (immune surveillance).
  5. Mitotic engine: new keratinocytes born here. Melanocytes (pigment) and Merkel cells (touch) sit at this layer.
  6. Loose areolar tissue: dermal papillae interlock with epidermis. Holds the capillary network that feeds the epidermis (which has no blood vessels of its own). · Meissner corpuscles: light touch receptors.
  7. Dense irregular connective tissue: collagen and elastin web that gives skin its strength and rebound. · Hair follicles, sebaceous glands, sweat glands all live here. · Pacinian corpuscles: deep pressure and vibration receptors.
  8. Adipose + loose connective tissue: anchors skin to underlying fascia. Insulation, energy reserve, shock absorption. · Not technically part of skin but everything in skin attaches to it.

Define it: high-yield vocabulary

Write a clear definition in your own words for each term.

  1. Epidermis
  2. Dermis
  3. Hypodermis (subcutaneous)
  4. Keratinocyte
  5. Melanocyte
  6. Stratum basale
  7. Stratum corneum
  8. Papillary layer
  9. Reticular layer

Part 2 of 4 · Anatomy lab

Draw and label

Box A. Skin in cross-section (three layers)

Directions

  1. Draw a vertical rectangle representing a piece of skin in cross-section. The TOP is the surface; the BOTTOM is deep tissue.
  2. Top third: draw the epidermis. Make it relatively thin. Shade it differently from the layers below.
  3. Middle third: draw the dermis. Inside, sketch one hair follicle (extending from epidermis down into dermis), one sebaceous gland (attached to the hair follicle), one sweat gland (coiled at the deep end of a duct), and a blood vessel.
  4. Bottom third: draw the hypodermis (subcutaneous layer). Show large round adipocytes (fat cells).
  5. Label all three layers and every structure you drew.
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Box B. Epidermal strata close-up (thick skin)

Directions

  1. Draw a tall vertical rectangle representing the epidermis at high magnification.
  2. From DEEP to SUPERFICIAL, label five strata: Stratum basale, Stratum spinosum, Stratum granulosum, Stratum lucidum (thick skin only), Stratum corneum.
  3. In stratum basale, draw a row of cuboidal cells with mitotic figures (cells dividing).
  4. In stratum spinosum, draw polygonal cells with visible cell junctions (desmosomes).
  5. In stratum granulosum, draw flattening cells with dark granules inside.
  6. In stratum lucidum, draw a thin clear band (transparent).
  7. In stratum corneum, draw many thin flat dead cells stacked, with the topmost ones sloughing off.
  8. On the side, draw an arrow showing the keratinocyte migration: from basale up to corneum, taking 2 to 4 weeks.
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Structures to label

Label each on your drawing.

  1. Epidermis
  2. Dermis
  3. Hypodermis (subcutaneous)
  4. Stratum basale
  5. Stratum spinosum
  6. Stratum granulosum
  7. Stratum lucidum
  8. Stratum corneum
  9. Hair follicle
  10. Sebaceous gland
  11. Sweat gland
  12. Blood vessel
  13. Adipocyte
  14. Keratinocyte

Part 3 of 4 · Physiology lab

Reason it through

A. Trace a keratinocyte from birth to death

Explain the main idea of this topic.

B. Synthesis

1. A patient has a second-degree burn that extends into the upper dermis. Predict whether this will heal by regeneration or by scarring, and explain why.
2. A patient with extensive third-degree burns (full thickness) loses large patches of skin. Predict the two MOST immediate life-threatening consequences and explain the physiology behind each.
3. Stratum corneum is constantly shed. Calculate roughly how much skin a person sheds in a year if the turnover time is about 4 weeks and the epidermis is about 0.1 mm thick. (You don't need exact numbers; reason in orders of magnitude.)

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