EX7: Skin and Membranes

I. Introduction/Background Information

        Refer to the Lab worksheet : https://sites.google.com/site/physiolablist/

There are several sections to this lab, generally designed to assist students in understanding the structures & functions of skin & other body membranes. The objectives of this lab are:

1. to recount important functions of the skin/integumentary system
2. to recognize and name the following structures from a slide, model or diagram
• epidermis (including strata), 
• dermis (papillary & reticular layers
• hair follicles & hair
• sebaceous glands & sweat glands
3. to compare the properties of the dermis & epidermis
4. to describe the distribution and function of the sebaceous glands, sweat glands, and hair 
5. to differentiate between eccrine & apocrine sweat glands
6. to ennumerate the factors determining skin color
7. to describe the function of melanin
8. to compare the structure and function of the major membrane types
9. to list the general functions of each membrane type and note its location in the body
10. to recognize by microscopic examination epidermal, mucous, and serous membranes

II. Hypothesis

Part 1: Basic structure of the skin: If students read about structures as they locate them on a skin model then they will be able to write out a response to each objective
Part 2: Appendages of the Skin: If students examine a prepared slide of human skin then they will be able to identify skin structures on a drawing.
Part 3: Plotting the Distribution of sweat glands: If bond paper is taped to skin coated with iodine and left for 20 minutes, then a distribution of sweat glands will be mapped out because the sweat glands will dissolve the iodine, which will then be absorbed by the paper.  As it reacts with the starch in the bond paper each sweat gland will produce a blue/black dot.
Part 4: Classification of Membranes: If students examine slides from trachea and small intestine, heart, as well as a freshly cut joint, then they can compare mucous, serous and synovial membranes.

III. Materials

    “See Lab instructions”

IV. Procedure

“See Lab Instructions” (you may include pictures of procedure)

Part 1: Basic structure of the skin:

Skin slide

Human Skin Slide

Part 2: Appendages of the Skin:
Part 3: Plotting the Distribution of sweat glands:
Part 4: Classification of Membranes:

pseudostratified ciliated columnar epithelium

mucosa of trachea

mucosa of small intestine

drawing of one villus

pericardium (around the heart)

V. Results/Observation/Data

List answers to questions from each section of the lab
Part 1: Basic structure of the skin:
1.

epithelial tissue
keratin
carotene
freckle/mole
2. insulates, cushions, keeps water in/out, and protects from damage (mechanical, chemical, thermal, bacterial)
3. DIAGRAM
4. cyanosis is a condition of the skin in which it appears blue due to a lack of oxygenated blood.

5.  translucent cells containing keratin fibrils: D. stratum lucidum
dead cells: D. A. stratum lucidum, stratum corneun
dermis layer responsible for fingerprints: E. papillary layer
major skin area where derivatives arise: G. epidermis as a whole
epidermal region exhibiting rapid cell division: B. stratum germanitivum
scalelike dead cells, full of keratin, that constantly slough off: A. statum corneum
composed of two strata, the basale and the spinosum: G. epidermis as a whole
site of elastic and collagen fibers: H. dermis as a whole
site of melanin formation: B. stratum germanitivum
Part 2: Appendages of the Skin:

e. sebaceous glands
a. arrector pili
g. eccrine
d. hair folllicle
f. apocrine
e. sebaceous glands
c. hair
b. cutaneous receptors
e. sebaceous glands, f.
g. eccrine
Part 3: Plotting the Distribution of sweat glands:
1. sweat
2. the palm
armpit, soles of the feet, groin
3. the excretory system


Labeled Pictures:

Part 4: Classification of Membranes:
1. cutaneous; epithelial; skin; outermost protective layer
mucous; epithelial; all body cavities that open to the exterior; absorption and secretion
serous; epithelial; all body cavities closed to the exterior; secrete fluid
synovial; connective; joints; lines fibrous capsules surrounding joints
2. associated with skeletal system structures: D. synovial
formed of simple squamous epithelium: A. cutaneous
not found in the ventral body cavity: D. synovial, A. cutaneous
goblet cells: B. mucous
external membranes: A. cutaneous
wet membranes: B. mucous
adapted for absorption and secretion: B. mucous
has paretial and visceral layers: C. serous

VI. Conclusion: Respond to each objective. What did you learn?

1.  What are the important functions of the skin/integumentary system?      Its functions are to protect the body's internal organs, protect against infectious organisms, help prevent dehydration, regulate body temperature, help to dispose of waste, and to store water and fat.
2. Can you recognize and name the following structures from a slide, model or diagram?
• epidermis (including strata),   yes
• dermis (papillary & reticular layers   yes
• hair follicles & hair   yes
• sebaceous glands & sweat glands   yes
3. Compare the properties of the dermis & epidermis.    The dermis is the layer of skin under the epidermis, it is composed of a papillary layer and a reticular layer.  It contains collagen, elastic fibers, and extrafibrillar matrix.  The epidermis is made up of stratified squamous epithelium and is the outermost layer of the skin that helps to protect the body from foreign objects.
4. Describe the distribution and function of the sebaceous glands, sweat glands, and hair. 
   Sebaceous glands: Secrete sebum that lubricates the skin and hair, they are located in abundance on the face and scalp, but can be found everywhere except the soles of the feet and palms of the hand.
   Sweat glands: They are exocrine glands and they help to regulate body temperature.  They are located all throughout the integumentary system.
   Hair: The function of hair is to help protect the body, it reduces the radiation absorbed by the sun, and in the eye brows and eye lashes helps prevent things from getting into the body, and nose hairs help humans to not inhale foreign objects.  They are located on the entire body for most mammals.
5. Differentiate between eccrine & apocrine sweat glands.  Eccrine glands are located all over the body, but in higher concentrations in the armpits, palms and sole of the feet.  They do not use a hair follicle to secrete to the surface of the skin, but rather they each have their own pore.  Apocrine glands are located in the armpit and pubic region of the body.  They do use a hair follicle in order to secrete and this is the type of sweat that causes odor.
6. Ennumerate the factors determining skin color.  Three factors affect skin color, and they are melonin, hemoglobin, and carotene.  These factors are determined by genetics.
7. Describe the function of melanin.  It is a dark cell, therefore the more a person has the darker they will be.  It is the cell that causes freckles.  It is used to help protect against UVB radiation.
8. Compare the structure and function of the major membrane types.  Mucous is meant for absorption and secretion, it lines the body cavities that open to the exterior of the body.  Serous membranes provide a layer of fat for lubrication and a connective tissue layer with blood vessels and nerves.  Cutaneous is meant to be water proof.
9. List the general functions of each membrane type and note its location in the body.  Functions listed in the above question.  Cutaneous are located on the outer layer of the skin, mucous line the body cavities that open to the exterior of the body, and serous line the body cavities that are closed to the exterior of the skin.
10. Can you recognize by microscopic examination epidermal, mucous, and serous membranes?  Yes.