TISSUES, SKIN, MEMBRANES LAB (Online)

Tissues, Skin, and Membranes Lab

Part 1. Tissue Identification and Characterization

View these slides of epithelial tissue:

·         Stratified squamous Plate 2.22

·         Cuboidal Plate 2.17

·         Simple columnar Plate 2.18

1.       Name two distinguishing microscopic characteristics of epithelial tissue.  The two distinguishing characteristics are Epithelial tissue are separated from the underlying tissue by a basement membrane and also by the number of cell layers in the tissue.

2.       How does the structure of epithelial tissue match its function? Epitheliums are thin layers of tissue that provides a smooth surface so fluids can easily move.

View these slides of connective tissue:

·         Loose (areolar) Plate 3.27

·         Adipose Plate 3.39

·         Hyaline cartilage Plate 3.41

1.       Name two distinguishing microscopic characteristics of connective tissue. Characteristics are physical features that tell you, “This is connective tissue.”  Connective tissue has very few living cells and the strength of tissue comes from the matrix not from the living cells themselves.

2.       How does the structure of connective tissue match its function? As it is a strong tissue it supports and helps connect the body together

View these slides of muscle tissue:

·         Skeletal (striated) Plate 5.66

·         Smooth Plate 5.81

·         Cardiac Plate 5.76

1.       Name two distinguishing microscopic characteristics of muscle tissue. Characteristics are physical features that tell you, “This is muscle tissue.” Characteristics are not locations or functions.  Muscle tissue consists of specialized cells to shorten or contract and is composed of tightly packed cells called muscle fibers.

2.       How does the structure of muscle tissue match its function?  Having specialized cells that contract and shorten it helps with movement of the body and especially the heart.

View this slide of nervous tissue:

·         Motor neuron Plate 6.89

1.       Name two distinguishing microscopic characteristics of nervous tissue. Characteristics are physical features that tell you, “This is nervous tissue.” Characteristics are not locations or functions.  The nervous tissue consists of neurons and glial cells.

2.       How does the structure of nervous tissue match its function?  The cells within the tissues generate and transmit electrical impulses.

Part 2. Tissue Membranes

o   Photos of sketches of membranes

1.       Sketch a serous membrane showing 4 details.

2.       Sketch a mucous membrane showing 4 details. 

3.       Sketch a synovial membrane showing 4 details. 

4.       Sketch a cutaneous membrane showing 4 details. 

Part 3. Body Position and Directional Planes

1.       A friend tells you she has a blister on the inferior surface of her foot. She adds that it is posterior, not anterior. Where is her blister?  A posterior and inferior blister would be located near the back and inside of her foot.

2.       Label the planes on Figure 1.

 

Figure 1

Part 4. Skin Structure and Function

o   One photo of Testing Tactile Localization and Adaptation

o   Labeled Figure 2

o   Answers to video questions 2 and 3

The skin is an organ system called the integumentary system. It does much more than cover the body exterior. The skin has several functions related to homeostasis. The skin has two distinct regions firmly cemented together along a wavy border.

Visualizing Changes in Skin Color

1. What would happen if in this area the pressure continued for an extended period? Why?

     After pressing the plate on my palm it started to turn white. If I continued to press the plate on my hand 

     For longer I believe the circulation would be cut off because it would stop blood flow to the area.

Testing Tactile Localization and Adaptation

The density of the touch receptors in the epidermis varies significantly in different areas of the body. In general, areas having the greatest density of tactile receptors have a heightened ability to “feel.” These areas are typically areas of fine motor control. Tactile localization is the ability to determine which portion of the skin has been touched. Each receptor has a corresponding touch field in the brain.

Procedure:

1.       A person designated as “subject” closes her or his eyes. A person designated as  “experimenter” touches the palm of the subject’s hand with the open end of a Sharpie marker. The subject then attempts to touch the exact point with her or his own marker of a different color.

2.       The experimenter measures the discrepancy of localization in millimeters.

3.       Wash ink off area and repeat the procedure in a different area of the palm.

4.       Average the results, and record in Table 1.

5.       Repeat the procedure on a fingertip, the ventral forearm, and the back of the hand.

6.       Record the averaged results in Table 1.

Table 1. Average Discrepancy Between

Subject and Experimenter Touch Points

Palm	Fingertip	Forearm	Back of Hand
Average Discrepancy 3 mm	Average Discrepancy .5 mm	Average Discrepancy 6mm	Average Discrepancy 2mm

7.       In the tactile location exercise, which area had the smallest error of localization (is most sensitive to touch)? Give a possible explanation for this. The area which had the smallest error was the fingertip, I believe it is because of the fingertips have more nerve endings. It seems that the fingertips have more feeling than most parts of the body.

The dermis has a rich nerve supply. Many of the nerve endings bear specialized receptor organs that respond to pain, pressure, or temperature extremes and transmit messages to the central nervous system for interpretation.

·         A Meissner’s corpuscle responds to light touch and is composed of connective tissue located in a dermal papilla.

·         The much larger Pacinian corpuscle responds to deep pressure and resembles a tiny onion.

In many cases, when a stimulus is applied for a prolonged period of time, the rate of receptor response slows, and our conscious awareness of the stimulus declines. This phenomenon is called adaptation. Touch receptors adapt rapidly so that we are not aware of our clothing rubbing against our skin, for example.

1.       A person designated as “subject” closes her or his eyes. The experimenter places a coin on the

anterior surface of the subject’s forearm and determines how long the sensation persists for the subject.

Duration of sensation: 10 seconds

2.       Repeat the test, placing the coin at a different location on the forearm. How many seconds does the sensation persist?

Duration of sensation: 8 seconds

3.       After awareness of the sensation has been lost at the second site, stack three more coins on top of the first one.

4.       Does the pressure sensation return? If so, for how many seconds is the subject aware of the pressure in this instance?  The pressure sensation did return for a short period of time.

Duration of sensation: 11 seconds

5.       Do a bit of research to learn if the same receptors being stimulated when the four coins, rather than one coin is used. What is your conclusion?  When the sensory receptors are stimulated with the four coins it does adapt to the pressure but it seems to take a little longer than the single coin.

Appendages of the Skin

Appendages of the skin include hair, nails, and cutaneous glands. These are all derived from the epidermis but reside in the dermis.

A hair is also an epithelial structure. The part of the hair enclosed within the follicle is called the root. The portion of the hair projecting from the skin is called the shaft. Hair is formed by mitosis of the cluster epithelial cells at the base of the follicle. This cluster is called the hair bulb. As the daughter cells are pushed away from the growing region, they become keratinized and die. The bulk of the hair shaft is dead material.

1.       Label Figure 2. (.5 point)

Figure 3. Skin Cross Section

The Action of UV Light

From The Skin Cancer Foundation, http://www.skincancer.org/prevention/uva-and-uvb/understanding-uva-and-uvb

By damaging the skin's cellular DNA, excessive UV radiation produces genetic mutations that can lead to skin cancer. Both the U.S. Department of Health and Human Services and the World Health Organization have identified UV as a proven human carcinogen. UV radiation frequently plays a key role in melanoma, the deadliest form of skin cancer, which kills more than 8,000 Americans each year.

Most of us are exposed to large amounts of UVA throughout our lifetime. UVA rays account for up to 95 percent of the UV radiation reaching the Earth's surface. Although they are less intense than UVB, UVA rays are 30 to 50 times more prevalent. They are present with relatively equal intensity during all daylight hours throughout the year, and can penetrate clouds and glass.

Studies over the past two decades, however, show that UVA damages skin cells called keratinocytes in the basal layer of the epidermis, where most skin cancers occur. (Basal and squamous cells are types of keratinocytes.) UVA contributes to and may even initiate the development of skin cancers.

UVA is the dominant tanning ray, and we now know that tanning, whether outdoors or in a salon, causes cumulative damage over time. A tan results from injury to the skin's DNA; the skin darkens in an imperfect attempt to prevent further DNA damage. These imperfections, or mutations, can lead to skin cancer. The high-pressure sunlamps used in tanning salons emit doses of UVA as much as 12 times that of the sun. According to recent research, first exposure to tanning beds in youth increases melanoma risk by 75 percent.

UVB, the chief cause of skin reddening and sunburn, tends to damage the skin's more superficial epidermal layers. It plays a key role in the development of skin cancer and a contributory role in tanning and photo aging. Its intensity varies by season, location, and time of day. The most significant amount of UVB hits the U.S. between 10 AM and 4 PM from April to October. However, UVB rays can burn and damage your skin year-round, especially at high altitudes and on reflective surfaces such as snow or ice, which bounce back up to 80 percent of the rays so that they hit the skin twice.

UVB penetrates cells and damages and fragments them. As the skin tries to heal, swelling and increased blood flow results. This is called erythema (sunburn). A secondary effect of an encounter with UV-B light is that melanocytes emit a dark brown pigment called melanin into the surrounding keratinocytes. Melanin absorbs UV light and serves to protect these cells from further damage. Melanin-containing keratinocytes migrate to the skin’s surface.

UVC is the highest energy light in the UV range breaking and fragmenting protein molecules and DNA

.

1.       Watch this video to learn more about UV light and your skin. http://youtu.be/o9BqrSAHbTc.

2.       What kind of sunscreen or sunblock to you use and how frequently? I personally do not use sun block as I do not go out in the sun for long periods of time. I use SPF 40 on my son when he goes outside during the summer.

3.       What does the production of more melanin (tanning) mean?  Excess exposure to the sun creates more melanin as a way to protect our skin