A slice of real skin under a microscope, stained pink and purple: a dark purple band of epidermis on top and pink dermis below

ANATOMY AND PHYSIOLOGY · CHAPTER 6

Skin Under the Microscope

Follow along with your worksheet, one question at a time.

mrsajdak.com/skin-layers

Photo: Kilbad, public domain

BEFORE YOU START

Skin wears away. A tattoo stays.

A rock climber in a helmet rubbing white chalk onto his hands beside a boulder

Rubbed all day

Hands grip, rub and scrape. The top of your skin wears off. New skin takes its place.

A sailor holding up his forearm to show a rose tattoo

Still there

Tattoo ink does not wash off. It does not wear off. It stays for life.

The layers

1. Epidermis, on top

2. Dermis, below it

3. Subcutaneous layer, beneath the skin

Skin is the first two. Each layer is built for a different job.

If skin keeps wearing away, how can a tattoo last for life?

Photos: Emily Hassell, National Park Service · Brandon Richardson, U.S. Navy

BEFORE YOU START

Get set up

1

Open mrsajdak.com/skin-layers on your device.

2

Write your name, the date and your period on the worksheet.

3

Find the four tabs at the top of the lab. Each tab goes with one part of the worksheet.

4

Day 1 is the front of the worksheet. Day 2 is the back.

5

Start on Tab 1. Do not skip ahead.

The top of the lab page, showing the title and four tabs: Virtual microscope, Body map, Inside the epidermis, Inside the dermis
Tab in the labWorksheetQuestions
1. Virtual microscopeDay 1 · Part 11 to 6
2. Body mapDay 1 · Part 27 to 10
3. Inside the epidermisDay 2 · Part 311 to 15
4. Inside the dermisDay 2 · Part 4, Wrap it up16 to 20

Screenshot: mrsajdak.com/skin-layers

Students in a science classroom leaning over a table to look through microscopes

DAY 1 · TAB 1 · QUESTIONS 1 TO 6

Part 1. Virtual microscope

A thin slice of skin sits on a slide. Stain makes its parts show up.

You will find the three layers. Then you will measure them and test three injuries.

Photo: Hennepin County Library, public domain

PART 1 · QUESTION 1

Focus, then find the layers

1

Pick a slide. Start with Thin skin · forearm.

2

Move the Focus slider until the lab says sharp.

3

Click a spot inside the circle. A yellow marker shows up.

4

Name the layer under the marker. A wrong pick gets crossed out.

5

Find all three layers on both slides. Then tick the clues in Question 1.

The Microscope box in the lab: buttons for the slide and the objective lens, a focus slider, arrow buttons to move the slide, and three buttons to name a layer
The view down the lab microscope: a round view of pink and purple skin with a scale down the middle and a yellow marker with a question mark

Drag the slide to move it. Or use the arrow buttons.

Pink stain shows proteins. Purple stain shows nuclei.

Screenshots: mrsajdak.com/skin-layers, Tab 1

PART 1 · QUESTION 2

Read the eyepiece scale

1

Find the scale in the middle of the circle. It has 50 divisions.

2

Pick the 4× objective lens. Look to the left of the circle. The lab says what 1 division is worth.

3

Write that number. Do the same for 10× and 40×.

4

Focus again after each change. Each lens has its own sharp spot.

The view down the lab microscope at thick skin, with the eyepiece scale numbered 0 to 50 running down the middle of the circle

Words to know

Objective lens
The lens near the slide.

Division
One small step on the scale.

µm
A micrometer. 1,000 µm = 1 mm.

Screenshot: mrsajdak.com/skin-layers, Tab 1

PART 1 · QUESTION 3

Measure a layer

1

Press Centre. Your worksheet uses the middle of the slide.

2

Move the slide up or down. Put 0 on the top edge of the layer.

3

Count the divisions down to the bottom edge of the layer.

4

In Measure a layer, pick the layer. Type your count. Press Check.

5

Fill in the row. Do both layers on both slides.

The Measure a layer box in the lab: a menu to pick the layer, a box to type the divisions, and a Check button

Layer longer than the scale? Try a weaker lens.

Layer only a division or two? Try a stronger lens.

The lab keeps your checked rows in Your results.

Example

You count 9 divisions.

One division is worth 25 µm.

9 × 25 = 225 µm

225 µm ÷ 1,000 = 0.225 mm

These are not your numbers. Use your own.

Screenshot: mrsajdak.com/skin-layers, Tab 1

PART 1 · QUESTIONS 3 AND 4

Pick the lens that fits the layer

TOO BIG

50

The scale ends

The scale has only 50 divisions.

A layer that runs past the end cannot be counted in one go.

TOO SMALL

1 or 2?

Hard to count

A very thin layer covers only a sliver of the scale.

A small slip makes a big error.

QUESTION 4

Best?

Which lens for the thin epidermis?

Look at your table. Which objective did you use?

Now try it at 4×. How much of the scale does it cover?

PART 1 · QUESTIONS 5 AND 6

How deep does it go?

1

Pick a slide.

2

Under How deep is the injury?, press Scrape · 0.05 mm.

3

Find the white notch on the slide. Read Deepest layer and Bleeds?

4

Do the same for Cut · 0.3 mm and Deep cut · 2.0 mm.

5

Switch slides. Do all three again.

The How deep is the injury box in the lab, with three buttons: Scrape 0.05 mm, Cut 0.3 mm and Deep cut 2.0 mm

If the lab says Yes, a little, circle yes.

Your results keeps a list under Injuries.

QUESTION 6

Same cut, two results

Compare the 0.3 mm cut on the forearm and on the palm.

Use your epidermis numbers from Question 3.

What does the epidermis have? What does it not have?

Screenshot: mrsajdak.com/skin-layers, Tab 1

Two bare feet walking away across wet sand, one heel lifted and coated in sand

DAY 1 · TAB 2 · QUESTIONS 7 TO 10

Part 2. Body map

Skin is not the same thickness everywhere.

You will compare six places on the body. Look for a pattern.

Photo: Western Arctic National Parklands, CC BY 2.0

PART 2 · QUESTION 7

Click all six sites

1

Click each of the six dots on the body.

2

Each click adds a slice of that skin to the chart. Every slice is drawn to the same scale.

3

Find the Six sites table.

4

Copy Epidermis mm and Dermis mm for each site.

5

The Skin column says thick or thin. Copy that too.

The body map in the lab before any site is clicked: a body with six dots, and six empty columns with question marks for the eyelid, forearm, upper back, palm, fingertip and sole

Screenshot: mrsajdak.com/skin-layers, Tab 2

PART 2 · QUESTIONS 8 TO 10

Find the pattern

QUESTION 8

÷

How many times thicker?

Divide the sole epidermis by the eyelid epidermis.

Then find the forearm in your Question 3 table. Does it match the chart?

QUESTION 9

Top 3

What do they share?

Under Line the slices up by, press epidermis, thin to thick.

Click the three thickest. Read What it faces for each one.

QUESTION 10

Back

Thick dermis, thin epidermis

Press dermis, thin to thick. Find the upper back.

What is each layer built for? Use that to explain.

The surface of human skin seen with an electron microscope: flat, flaky plates with raised ridges

DAY 2 · TAB 3 · QUESTIONS 11 TO 15

Part 3. Inside the epidermis

The epidermis has layers of its own. One layer is a stratum. More than one are strata.

You will name them. Then you will follow one cell from the day it is born to the day it flakes off.

Photo: Bruce Wetzel, National Cancer Institute

PART 3 · QUESTION 11

Name the five strata

1

Stay on Thick skin · palm. Click a band in the picture.

2

Name it. A wrong pick gets crossed out. Try again.

3

Read the note that shows up. It tells what happens to cells there.

4

Find all five. Write them in order, bottom to top.

5

Switch to Thin skin · forearm. Which stratum is missing?

The Inside the epidermis box in the lab: buttons for thick skin and thin skin, a list of strata to find, five buttons to name a stratum, and two tick boxes
The thick skin epidermis in the lab, drawn as bands of pink and purple cells, with a yellow marker and a question mark on one band

The yellow marker shows where you clicked.

Found bands get a green pin with their name.

Screenshots: mrsajdak.com/skin-layers, Tab 3

PART 3 · QUESTION 12

Follow one cell

1

Switch to Thin skin · forearm.

2

Find Follow one cell. Press Play. Or press +1 day.

3

Watch The cell’s trip. It fills in the day the cell enters each stratum.

4

Copy the days. The last one is the day the cell flakes off.

5

Divide that last day by 7. That is the number of weeks.

The Follow one cell box in the lab at day 0: a day slider, buttons for Play, +1 day and Back to day 0, and a list that says where the cell is, if it is alive, its nucleus, its shape and how much keratin fills it
The thin skin epidermis in the lab on day 0, with one yellow cell marked in the bottom row

Example

42 ÷ 7 = 6

A cell that flakes off on day 42 took 6 weeks. These are not your numbers.

Screenshots: mrsajdak.com/skin-layers, Tab 3

PART 3 · QUESTIONS 13 TO 15

Alive, fed and replaced

QUESTION 13

Alive?

Where does the cell die?

Step through the days. Watch Nucleus. Where does it start to break down?

Check your notes from Question 11. Then read the last line in the box. What fills the cell?

QUESTION 14

Fed?

No blood vessels

Tick Show where food and oxygen come from. Find the yellow glow.

Where does it start? Which cells are far from it? Does that hurt a dead cell?

QUESTION 15

Steady

Lost on top, same thickness

Go back to day 0. Read the first line under Follow one cell.

Cells leave the top every day. What keeps up with the loss?

A close view of a fingertip, with fine curved ridges running across the skin

DAY 2 · TAB 4 · QUESTIONS 16 TO 19

Part 4. Inside the dermis

The dermis has two layers. The papillary layer is on top. The reticular layer is below.

You will find seven structures, pull on each layer, and count the ridges on a fingertip.

Photo: Frettie, CC BY 3.0

PART 4 · QUESTION 16

Find all seven

1

Look under Find each one. The lab names what to find next.

2

Click it inside the circle. Green words tell you when you found it.

3

Wrong spot? The lab tells you what you clicked. Keep looking.

4

Move the slide down for the deep ones. Or switch to 4×.

5

Read the note under each one you find. It says where it is. Then tick the table.

The Inside the dermis box in the lab: buttons for the view and the objective lens, a focus slider, arrow buttons, a tick box for the elastic-fiber stain, and a list of seven structures to find
The view down the lab microscope at thick skin: the wavy bottom edge of the epidermis with the pink dermis below it

You find them in order. There are seven.

Elastic-fiber stain turns the elastic fibers black.

Screenshots: mrsajdak.com/skin-layers, Tab 4

PART 4 · QUESTIONS 17 AND 18

Pull until it tears

1

Find Pull test. Pick a Sample and a Pull direction.

2

Press Skip to the end. Or press Pull until it tears and watch.

3

Read the force where it tore. It is in Your results.

4

Do all five tests in your table.

5

Question 18: divide the reticular force by the papillary force.

The Pull test box in the lab: buttons for the sample and the pull direction, a line that describes the fibers, and buttons for Pull until it tears and Skip to the end
The lab pull test part way through: a strip of tissue stretched between two clamps, beside a graph of force against stretch

This strip is still being pulled. It has not torn yet.

Read Fibers under the buttons. It says how the fibers run.

Example

60 ÷ 15 = 4

A strip that tears at 60 N is 4 times stronger than one that tears at 15 N. These are not your numbers.

Screenshots: mrsajdak.com/skin-layers, Tab 4

PART 4 · QUESTION 19

Count the ridges

1

Under View, press Fingertip surface.

2

Find the blue line inside the 5 mm box. Count the ridges that cross it.

3

Divide 5 mm by your count. That is how far apart the ridges are.

4

Read the words beside the picture. Where does the ridge pattern start?

5

The epidermis is replaced every few weeks. Why does the pattern stay?

The View buttons in the lab: Microscope slide and Fingertip surface

Example

5 mm ÷ 4 = 1.25 mm

4 ridges across 5 mm are 1.25 mm apart.

These are not your numbers.

Four fingertips lit from the side so the curved ridges of the fingerprints stand out

Screenshot: mrsajdak.com/skin-layers, Tab 4 · Photo: D. Sharon Pruitt, CC BY 2.0

WRAP IT UP · QUESTION 20

Why does a tattoo last?

The claim

“Tattoo ink lasts for life only because it is put into the dermis.”

Evidence 1

Pick one tab. Use a number or a fact from your worksheet. Tab 3 tells how long one cell lasts.

Evidence 2

Pick a different tab. Tab 1 shows how deep a cut must go. Tab 4 shows a pattern that lasts for life.

Reasoning

Compare the two layers. What happens to cells in the epidermis over time? What about the dermis?

A blue-grey tattoo covering a person's upper arm

Tattoo ink sits in the skin for many years.

Photo: Tony Alter, CC BY 2.0

Several microscopes set out on a white lab bench

LAST CHECK

Before you hand it in

Name, date and period are on top.

Every table is full, front and back.

Questions 1, 11 and 16 have their ticks.

Every measurement has a unit: µm, mm or N.

Question 20 uses evidence from two different tabs.

Photo: R G, CC BY 2.0