Lab Worksheet:  The Integument

Introduction

This week's lab will focus on the integument system including the anatomy and physiology of the skin and accessory glands.

Objectives

Objectives for this week's lab include:  1) Label the anatomy of the skin, 2) Analyze the health of the skin, 3) Demonstrate the effects of various sensory organs within the integument, and 4) Analyze an integumentary case study.

Overview

The integumentary system consists of the skin (epidermis and dermis) along with the accessory organs including the hair, nails and various glands.  The skin is composed of the epidermis and dermis.  The hypodermis is technically not part of the integument but is typically studied because of its close association with the skin.

The epidermis is composed of stratified epithelial tissue and contains five distinct layers with the stratum basale being the most diverse.  Melanocytes are found within the stratum basale and secrete a pigment called melanin that determines our skin color and protects us from the harmful effects of UV radiation.  The main cell of the epidermis is the keratinocyte, which secretes keratin.  Keratin providesprotective properties to the skin, including 'waterproofing'; hair and nails are composed of compacted keratin. Keratinocytes have a life cycle of about 30-45 days before they are scraped and flaked off the body.

The dermis is deep to the thin layer of the epidermis, is much thicker in size and is largely composed of connective tissue but also contains muscle and nerve tissue.  Unlike the epidermis, the dermis contains a rich supply of blood and lymphatic vessels along with nerve fibers.  The dermis also contains collagen fibers (provides structural support), elastic fibers (provides elasticity), sensory organs along with the origins of the hair follicles and glands.

The skin contains two types of glands:  Sweat and sebaceous glands.  There are two classifications of sweat glands, which include eccrine and apocrine sweat glands.  Both produce various forms of sweat secretions.  Sebaceous glands produce sebum, which is an oily secretion that prevents the skin from drying out.

It is vital to understand that the epidermis is continuously going through a regeneration process as new keratinocytes are produced, old ones are flaked off. 

The dermis on the other hand doesn't go through a regenerative, it's cells and structures are permanent.  Any permanent damage to the skin will be a result of damage to the dermis.  Permanent tattoos are a result of changes to the dermis; any changes to the epidermis are temporarily with the exception of skin cancer.  

Skin cancer is prevalent within the United States and will affect one of three cells found in the epidermis:  Basal cells, keratinocytes, and/or melanocytes.  Examination of various skin lesions commonly utilizes the ABCDE rule.  There are three degrees or classifications to the types burns that can occur, 1st, 2nd or 3rd.  The evaluation of burns, include determining the layers of skin affected and utilizing the "rule of nines" to determine the percentage of body surface burned.   

Materials

• Anatomical models of the skin and histology slides of the integument
• Woods lamp
• Magnifying glass
• Index cards, toothpicks and pennies

Pre-Lab Evaluation Questions

The pre-lab evaluation questions must be answered prior to lab and demonstrated to your lab instructor.  You must read through the assigned chapter readings, lab introduction, objectives, overview and procedure to answer these questions.

Please cite your work for any reference source you utilize in answering these questions. 

1. Explain the difference between the epidermis and dermis with a minimum of three characteristic differences.

2. What role does collagen and elastic fibers have within the skin?

3. What sensory receptors are found within the skin? Describe the variance with the concentration of these receptors in different regions of the body?

4. Compare and contrast the three types of skin cancer including thecell affected, most common type, most 'dangerous' typeand their overall prognosis?  How does the ABCDE rule apply to these conditions?

5. In your own words, describe the function of a Wood's lamp examination and its significance?

Part 01 Procedure: Anatomy and Histology of the Skin

1. Utilizing the anatomical models, differentiate the characteristic differences between the epidermis and dermis.

2. Locate the histological slides of the skin and utilizing a microscope, differentiate the characteristic differences between the epidermis and dermis.

Part 02 Procedure: Integument Sensory Receptors

1. There will be a number of work stations set up for this portion of the lab.  Please circulate through the lab stations as they are open and record your results.

A) Two Point Threshold

a. The density and concentration of sensory perception varies immensely according to region of body.  Test the sensitivity of touch between one point and two point threshold utilizing the 2mm, 3mm, 5mm and 10mm index cards on various regions of the body.  There will be two sets of index cards with toothpicks on them; one set with two toothpicks at the distances mentioned above and an index card with one toothpick on it. 

b. Have your lab partner close his/her eyes.  Randomly choosing the index card with toothpicks of various distances and the index card with one toothpick, test your lab partner's sensitivity by determining if they can sense if there is one or two points of contact on the various regions of the body listed below. 

c. For example, first take the index card that has two toothpicks 3mm apart and gently touch it to the neck region of the body.  Ask your lab partner if they sensed 1 or 2 toothpicks. Write Yes if they are able to distinguish two points at that specific distance and location on the body; Write No if they were not able to.  Remember, you have to mix up the order in which the index cards are tested; for example, test the 3mm index card, then maybe the 10mm card and then the index card with 1 toothpick on it.

B) Touch Receptor Adaptation

a. When a stimulus is applied for a prolonged time, the rate of the receptor input to the brain slows and the awareness of the stimulus declines or is lost; this refers to sensory adaptation and is a very common experience within our skin.  The loss of sensation continues until the stimulus changes, for example wearing glasses- eventually you lose perception that the glasses are being worn until they are moved.  This mini experiment will test the touch receptor adaptation.

b. For this portion of the lab, you will need 6 pennies.  Have your lab partner close his/her eyes.  Place one penny at the distal end of his/her forearm and record the duration of sensation in the chart.  There will be a point where your lab partner will no longer sense the penny on his/her skin. 

c. Leave the penny on the skin and place another penny on the proximal end of the forearm and record the duration of sensation in the chart.  Leave the penny on that spot.

d. Add one more penny to the distal location of the forearm and record the duration of sensation in the chart.  Do the same for the proximal location too and record the duration of sensation in the chart.  Then add a third penny to each location and record the duration of sensation in the chart.  Did you note any differences?

C) Wood's Lamp Examination

a. This mini-experiment will require the use of a Wood's lamp, which is a very expensive piece of medical equipment and should be handled and used with extreme care and caution.  This skin examination will need to be completed in a dark room; your lab instructor should designate a particular room where absolute darkness can be achieved.

b. Utilize "Appendix A" to assist your examination with the Wood's lamp.  When viewing your lab partner's skin, look for various scars, moles, skin lesions and/or any sun damage.  Normally, this examination is utilized to differentiate between bacterial and fungal skin infections and to see any underlying skin changes.  Always remember which layer of the skin is affected if there is permanent skin damage.

c. Record your results of what you observed in the space below:

D) ABCDE Rule

a. This portion of the lab will utilize the ABCDE rule to assess two different moles or abnormal skin spots on your and/or your lab partner's exposed arm/leg, face, or neck. Use a magnifying glass to assist your examination.

b. Utilizing the ABCDE rule, please make your observations on a mole or abnormal skin spot:

c. Utilizing the ABCD rule, please make your observations on a mole or abnormal skin spot:

Part 03 Procedure: Case Study Analysis

1. Please read the case study handout and work with your lab partners on answering the following questions:

Part 1

A) Why are Caucasians more at risk of skin cancer than other populations?

B) At what age does skin cancer typically occur? Is the incidence of skin cancer greater in youth or old age?

Part 2

C) Does the amount of UV light reaching the Earth vary in a predictable manner? If so, describe the pattern you observe.

D) What latitude receives the greatest amount of UV light? The least?

D) What latitude receives the greatest amount of UV light? The least?

F) Provide a rationale to your answer above (i.e., why did you think that more darkly pigmented people would be found in those areas)?

F) Provide a rationale to your answer above (i.e., why did you think that more darkly pigmented people would be found in those areas)?

Part 3

G) Is skin reflectance randomly distributed throughout the globe? If not, how would you describe the pattern?

H) How closely do these findings match the predictions of your hypothesis (Question E)?

I) Hypothesize why different skin colors have evolved. Based on what you know, what factor is most likely to exert a selective pressure on skin color?

Part 4

J) Review your answer to Question B. Keeping your answer in mind, how strong a selective pressure do you expect skin cancer (UV-induced mutations) to exert on reproductive success?

K) Based on this information, does your hypothesis about the evolution of skin color (Question I) seem likely? Why or why not? How does skin color meet, or fail to meet, the three requirements of natural selection outlined above?

Part 5

L) How is folate linked to natural selection? Folate is linked to natural selection

M) Based on this new information, revise your hypothesis to explain the evolution of human skin color.

Post-Lab Evaluation Questions

The post lab evaluation questions must be completed prior to your submission of the lab.  Answers for these questions will be derived from the lab protocol, the weekly concepts associated with the lab and possibly research content from the book and/or online resources. 

Please cite your work for any reference source you utilize in answering these questions. 

1. What aspect of this lab did you find most interesting?  Describe at least two different aspects. During this lab there was a lot of things that changed my opinion on natural selection and how UV affects generations.

2. Utilizing your knowledge of the integument system, describe why a permanent tattoo is permanent and a temporary tattoo is not.  Why do permanent tattoos tend to fade?

3. Describe the different classifications of the types of burns.  How is the percentage of the body burned measured?  What are the complications of severe burns?

4. In your own words, what is the difference between psoriasis and eczema? 

5. What are scars? Using your knowledge of the anatomy and physiology of the integument, describe how scars form and the concerns/complications of them.

Attachment:- Lab Worksheet.rar