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Human A&P BIO 304 · American River College ← Course home (Week 2)

BIO 304 . WEEK 2 . THURSDAY . LAB WORKBOOK

Skin Structure and Layers

Epidermis, dermis, and hypodermis: the largest organ of the body.

Print this page. You will draw your own diagrams from the directions below, then hand-label the structures listed. Drawing by hand is the integrity mechanism for this course.

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Part 1 of 2

Anatomy Lab

1A. What you will draw

Skin is built from three layers, each with a different tissue and a different job. Today you'll draw it twice: once as a vertical cross-section showing all three layers, and once zoomed in on the epidermal strata.

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.

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.

1C. Structures to label (14)

After you finish each drawing, label every structure below directly on your sketch.

  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 2 of 2

Physiology Lab

2A. Trace a keratinocyte from birth to death

A new keratinocyte is born in the stratum basale by mitosis. Trace its journey to the surface, including what happens at each stratum. List 5 to 7 numbered steps.

2B. Synthesis questions

Answer each in 2 to 4 sentences. Use the language from this week's lecture and your drawings as evidence.

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.)

3. What to submit

Complete both the Anatomy Lab (your own drawings, hand-labeled, plus the structures list) and the Physiology Lab (activity and synthesis questions). Photograph or scan every page and upload to Canvas before the deadline listed on the schedule. Hand-drawn, hand-labeled work is the integrity mechanism for this course. Typed or AI-generated diagrams are not accepted.