ANATOMY AND PHYSIOLOGY LAB. EXERCISE

DAVAO CENTRAL COLLEGE, INC.

Juan Dela Cruz St., Toril, Davao City

ANATOMY AND PHYSIOLOGY

Name:          April G. Datahan                                  Date:  February 20, 2014

Year and Course: BSED-III                                       Rating:

Laboratory Exercise No. 1

The Integumentary System

I.            Objective:      

a.    To be able to identify the functions, parts, role, structures and layers of the skin

b.    To be able explain the development of fingerprints and the effect of excessive exposure to the sun

c.    To be able to draw and label the structure of the skin

d.    To be able to reflect on the significance of the integumentary system on the human body

II.       Introduction:

Integumentary? That's a big word to describe something as simple as your skin. First, the skin is not all that simple. Second, integumentary systems take a wide variety of forms in animals across the world. Just think about the differences in the skin of a fish, a frog, a lizard, a bird, and a mammal. Scales, slime, feathers, and hair are all parts of the integumentary systems for animals. Your parts include the basic types of skin, hair, fingernails, oil, and sweat glands. They are found in integument layers called the epidermis, dermis, and subcutaneous. 

III.       Drawing with label:

IV.        Questions and Answers:

1.   1. Explain the structure of the skin: cell types, layers of the epidermis, and zones of the dermis.

Cell Types:

Keratinocytes: The most numerous cells are the keratinocytes which produce keratin, a fibrous protein responsible for protective properties of the epidermis. They arise from the deepest part of the epidermis from cells undergoing almost continuous mitosis. The keratinocytes are organized into 4-5 cell layers depending on body location. By the time the cells reach the surface of the skin, they are dead, scale-like structures. Every 35-45 days a totally new epidermis occurs. In areas of highest friction ( hands, feet) both cell production and keratin formation is accelerated.

Melanocytes: located at the base of the epidermis. Specialized cells that synthesize the pigment melanin. Melanin protects the cell nucleus from the destructive effects of UV radiation. Since all humans have the same relative number of these cells, individual and racial differences in skin coloring are probably due to differences in melanocyte activity.

Langerhans cells: arise from the bone marrow and migrate to the epidermis and other areas of the body containing stratified squamous epithelial tissue. They are macrophages and cooperate with T helper cells to assist in the immune response.

Merkel cells: present in small numbers at the epidermal-dermal junction. Associated with a disc-like ending of a sensory nerve fiber, called a Merkel disc, which functions as a sensory receptor.

Layers of the Epidermis:

          In thick skin (palms, fingertips, soles of feet) the epidermis consists of five layers or strata: (from deep to superficial) stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, stratum corneum. Thin skin, which covers the rest of the body has only 4 layers, with the stratum lucidum absent.

Stratum basale: single layer of cuboidal to columnar shaped cells. It is separated from the dermis by the basement membrane. Some cells move toward the surface while others migrate into the dermis and gives rise to sweat and oil glands. Many mitotic cells are seen. About 25% of the cells in this layer are melanocytes.

Stratum spinosum: contains 5-10 rows of cells fitted closely together. The surface of the cells display minute spiney projections. Mitosis occurs here but not as frequently. Langerhans cells are scattered among the keratinocytes. Because cells superficial to this layer do not receive adequate nutrients, they become less viable and finally begin to die.

Stratum granulosum: thin zone consisting of 3-5 layers of flattened cells. Keratinization begins in this third epidermal layer. The plasma membranes of these cells also thicken so that they become more resistant to destruction. Langerhans cells are also found in this layer. At the upper border of this layer, the cells die and lysosomes begin to digest their organelles.

Stratum lucidum (clear layer): translucent band just above the S. granulosum. Consists of a few rows of flattened dead keratinocytes with indistinct boundaries. Present only in thick skin.

Stratum corneum: outermost layer; a broad zone 20-30 cell layers thick. Accounts for about 3/4 of the epidermal thickness. The shingle-like dead cells are remnants, completely filled with keratin fibrils, and are referred to as cornified or horny cells. Keratin provides a durable abrasion resistant and water-repellent "overcoat" protecting deeper cells from the environment.

Zones of the Dermis:

Papillary: Thin superficial layer of loose connective tissue fibers. Forms a loosely woven mat that is heavily invested with blood vessels. Its superior surface is thrown into nipple-like projections called dermal papillae, that indent the epidermis above. Many dermal papillae contain capillary loops; others house free nerve endings and touch receptors (Meissner's corpuscles). On the ventral aspect of the hands and feet, the papillae are arranged in definite patterns that are reflected in the conspicuous looped and whorled ridges which enhance the gripping ability of the fingers and feet.

Reticular: accounts for about 80% of the dermis and is a typical dense irregular connective tissue. It contains bundles of interlocking collagen fibers that run in various planes parallel to the skin surface. The fibers interlace in a netlike manner with the spaces between the fibers occupied by a small amount of adipose tissue, hair follicles, nerves, oil glands and ducts of sweat glands. The connective tissue fibers of the dermis give skin its strength and resiliency. Collagen binds water, thus helping to maintain the hydration of the skin. The reticular region is attached to underlying organs (bones, muscles) by the subcutaneous layer.

2.    Explain each of the functions of the skin

The integumentary system has many functions, most of which are involved in protecting you and regulating your body’s internal functions in a variety of ways:

·         Protects the body's internal living tissues and organs

·         Protects against invasion by infectious organisms

·         Protects the body from dehydration

·         Protects the body against abrupt changes in temperature

·         Helps dispose of waste materials

·         Acts as a receptor for touch, pressure, pain, heat, and cold

·         Stores water and fat

In summary, our skin provides sensation, protection, thermoregulation and secretion of wastes.

3.    List the organs/derivatives of the integumentary system

Hair: functions include protection & sensing light touch.
Hair is composed of columns of dead, keratinized cells bound together by extracellular proteins. Hair has two main sections: The shaft- superficial portion that extends out of the skin and the root- portion that penetrates into the dermis. Surrounding the root of the hair is the hair follicle. At the base of the hair follicle is an onion-shaped structure called the bulb Papilla of the hair and the matrix within the bulb produce new hair.

Nails: participate in the grasp & handling of small things.
Nails are plates of tightly packed, hard, keratinized epidermal cells. 

The nail consists of:

• nail root: -the portion of the nail under the skin,
• nail body: -the visible pink portion of the nail, the white crescent at the base of the nail is the lunula, the hyponychium secures the nail to the finger, the cuticle or eponychium is a narrow band around the proximal edge of the nail and
• free edge: -the white end that may extend past the finger.

Glands: participate in regulating body temperature.
There are three main types of glands associated with the integument:

• Sebaceous - Oil glands. Located in the dermis, and secrete sebum.
• Sudoriferous - Sweat glands. Divided into two main types:
• Eccrine - Most common, main function is regulation of body temperature by evaporation, and
• Apocrine - Responsible for “cold sweat” associated with stress.
• Ceruminous – Lie in subcutaneous tissue below the dermis, secrete cerumen (ear wax) into ear canal or sebaceous glands.

4.   Explain the role of dermis in relation to the epidermis

The dermis is a layer of skin between the epidermis (with which it makes up the cutis) and subcutaneous tissues, that consists of connective tissue and cushions the body from stress and strain. It is divided into two layers, the superficial area adjacent to the epidermis called the papillary region and a deep thicker area known as the reticular dermis. The dermis is tightly connected to the epidermis through a basement membrane. Structural components of the dermis are collagen, elastic fibers, and extra fibrillar matrix. It also contains Mechanoreceptors that provide the sense of touch and heat, hair follicles, sweat glands, sebaceous glands, apocrine glands, lymphatic vessels and blood vessels. Those blood vessels provide nourishment and waste removal for both dermal and epidermal cells.

5.   Differentiate between the structure and function of each of the following types of glands in the skin:

Eccrine sweat glands are coiled tubular glands derived leading directly to the most superficial layer of the epidermis (out layer of skin) but extending into the inner layer of the skin (dermis layer). They are distributed over almost the entire surface of the body in humans and many other species, but are lacking in some marine and fur-bearing species. The sweat glands are controlled by sympathetic cholinergic nerves which are controlled by a center in the hypothalamus. The hypothalamus senses core temperature directly, and also has input from temperature receptors in the skin and modifies the sweat output, along with other thermoregulatory processes.

On the other hand, Apocrine sweat glands only develop during early- to mid-puberty (approximately age 15) and release more than normal amounts of sweat for approximately a month and subsequently regulate and release normal amounts of sweat after a certain period of time. Apocrine sweat glands produce sweat that contains fatty materials. These glands are mainly present in the armpits and around the genital area and their activity is the main cause of sweat odor, due to the bacteria that break down the organic compounds in the sweat from these glands. Emotional stress increases the production of sweat from the apocrine glands, or more precisely: the sweat already present in the tubule is squeezed out. Apocrine sweat glands essentially serve as scent glands.

The sebaceous glands are glands found in the skin of mammals. They secrete an oily substance called sebum (Latin, meaning fat or tallow) that is made of fat (lipids) and the debris of dead fat-producing cells. These glands exist in humans throughout the skin except in the palms of the hands and soles of the feet. Sebum acts to protect and waterproof hair and skin, and keep them from becoming dry, brittle, and cracked. It can also inhibit the growth of microorganisms on skin. It can usually be found in hair-covered areas where they are connected to hair follicles to deposit sebum on the hairs, and bring it to the skin surface along the hair shaft. The structure consisting of hair, hair follicle and sebaceous gland is also known as pilosebaceous unit. Sebaceous glands are also found in non haired areas of lips, eyelids, penis, labia minora and nipples; here the sebum reaches the surface through ducts. In the glands, sebum is produced within specialized cells and is released as these cells burst; sebaceous glands are thus classified as holocrine glands, while the earwax, also known by the medical term cerumen or the cerumen gland, is a yellowish, waxy substance secreted in the ear canal of humans and many other mammals. It plays a vital role in the human ear canal, assisting in cleaning and lubrication, and also provides some protection from bacteria, fungus, and insects. A comprehensive review of the physiology and pathophysiology of cerumen can be found in Roeser and Ballachanda. Excess or impacted cerumen can press against the eardrum and/or occlude the external auditory canal and impair hearing.

And lastly the mammary glands are the organs that, in the female mammal, produce milk for the sustenance of the young. These exocrine glands are enlarged and modified sweat glands and are the characteristic of mammals which gave the class its name. The basic components of the mammary gland are the alveoli (hollow cavities, a few millimetres large) lined with milk-secreting epithelial cells and surrounded by myoepithelial cells. These alveoli join up to form groups known as lobules, and each lobule has a lactiferous duct that drains into openings in the nipple. The myoepithelial cells can contract, similar to muscle cells, and thereby push the milk from the alveoli through the lactiferous ducts towards the nipple, where it collects in widenings (sinuses) of the ducts. A suckling baby essentially squeezes the milk out of these sinuses.

6.    Name the layers of the skin where most of the accessory glands are located in adult.

Glands in the Skin – The skin contains a number of exocrine glands

1.  Sebaceous glands

a.    Holocrine glands which discharge an oily secretion called sebum.

b.    The gland cells originate in the periphery of the gland. As they mature, the cells manufacture sebum, a mixture of triglycerides, cholesterol, proteins and electrolytes.

c.    As the cells reach the opening or lumen of the gland, they rupture releasing their product (holocrine secretion).

d.    There are two types of sebaceous glands:
i.  Simple branched alveolar glands – empty their secretion into the follicle of a hair.
ii.  Sebaceous follicles – large sebaceous glands that are connected directly to the epidermis and are not associated with a hair. They are found in the skin of the face, back, chest and nipples.

e.    Sebum functions by lubricating the skin and retarding the growth of bacteria.

2.  Apocrine glands

a.    Located in the armpits, groin and around the nipples.

b.    They produce a sticky, cloudy, odorous secretion into a hair follicle.

c.    These secretions become intensified at the time of puberty under the influence of the nervous and endocrine systems.

3.  Merocrine (eccrine) sweat glands

a.    Very numerous. In the adult, the skin may contain 2 to 5 million merocrine glands per square inch. Palms and the soles of the feet have the highest concentration.

b.    Merocrine glands are smaller than the apocrine glands.

c.    They produce a watery sweat containing electrolytes, lysozymes, antibodies and other ingredients.

d.    The functions of these glands include:

i.             Removing heat from body’s surface to lower body temperature. During periods of extreme sweating, the rate of perspiration may exceed 1 gallon of water / hour.
ii.  Excretion of water, electrolytes and nitrogenous wastes.
iii.  Protection from chemical and microbial

7.    Explain the role of the hypodermis/superficial fascia/ subcutaneous layer.

The hypodermis is the innermost and thickest layer of the skin. It invaginates into the dermis and is attached to the latter, immediately above it, by collagen and elastin fibres. It is essentially composed of a type of cells specialised in accumulating and storing fats, known as adipocytes. These cells are grouped together in lobules separated by connective tissue. The hypodermis acts as an energy reserve. The fats contained in the adipocytes can be put back into circulation, via the venous route, during intense effort or when there is a lack of energy providing substances, and are then transformed into energy. When we speak of "burning up calories", we are burning up fats in particular. The hypodermis participates, passively at least, in thermoregulation since fat is a heat insulator.

Superficial fascia is found in the subcutis in virtually all regions of the body, blending with the reticular layer of the dermis. It is present on the face, over the upper portion of the sternocleidomastoid, at the nape of the neck, and overlying the sternum. It is mainly loose areolar connective tissue and adipose and is the layer that primarily determines the shape of a body. In addition to its subcutaneous presence, this type of fascia surrounds organs and glands, neurovascular bundles, and is found at many other locations where it fills otherwise unoccupied space. It serves as a storage medium of fat and water; as a passageway for lymph, nerve and blood vessels; and as a protective padding to cushion and insulate.

The Subcutaneous layer is made up of subcutaneous tissue. It is the deepest layer of the skin, mainly consisting of fat cells called adipose. Loss of Subcutaneous layer causes facial sagging, leading to the formation of deep wrinkles associated with old age and the process of aging. The fat cells work as shock absorbers and they protect the body from mechanical trauma. They also act as heat insulators and help in stabilizing the body temperatures stable.

8.    Using specific examples correlate the structure of the skin with its function.

The skin helps our body moist and allows also secretion of sweat. Even though when we are in extraneous work out our skin does not become floppy because it is designed to become flexible but rigid in nature for protection. When we have cuts our skin is the one that protects our organs that is why it is the very external part of our body that protrudes various kinds of infections or diseases in air. Both the structure and function of the skin is designed to correlate and play important roles in our body. This is the very significance of the skin.

9.    List, in order from the bottom, the layers of the epidermis and distinguish each layer according to its structure and function.

Layers of the Epidermis:

          In thick skin (palms, fingertips, soles of feet) the epidermis consists of five layers or strata: (from deep to superficial) stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, stratum corneum. Thin skin, which covers the rest of the body has only 4 layers, with the stratum lucidum absent.

Stratum basale: single layer of cuboidal to columnar shaped cells. It is separated from the dermis by the basement membrane. Some cells move toward the surface while others migrate into the dermis and gives rise to sweat and oil glands. Many mitotic cells are seen. About 25% of the cells in this layer are melanocytes.

Stratum spinosum: contains 5-10 rows of cells fitted closely together. The surface of the cells display minute spiney projections. Mitosis occurs here but not as frequently. Langerhans cells are scattered among the keratinocytes. Because cells superficial to this layer do not receive adequate nutrients, they become less viable and finally begin to die.

Stratum granulosum: thin zone consisting of 3-5 layers of flattened cells. Keratinization begins in this third epidermal layer. The plasma membranes of these cells also thicken so that they become more resistant to destruction. Langerhans cells are also found in this layer. At the upper border of this layer, the cells die and lysosomes begin to digest their organelles.

Stratum lucidum (clear layer): translucent band just above the S. granulosum. Consists of a few rows of flattened dead keratinocytes with indistinct boundaries. Present only in thick skin.

Stratum corneum: outermost layer; a broad zone 20-30 cell layers thick. Accounts for about 3/4 of the epidermal thickness. The shingle-like dead cells are remnants, completely filled with keratin fibrils, and are referred to as cornified or horny cells. Keratin provides a durable abrasion resistant and water-repellent "overcoat" protecting deeper cells from the environment.

10. Explain why the cells in the upper layers of the epidermis die

-The upper layers of the epidermis die because of the loss of nutrient supply as they get closer and closer to the surface of the skin, and build up keratin inside them that leaks out into the area outside the cells.

11. Explain the anatomical and physiological differences between thick and thin skin.

- The terms thick and thin refer to the thickness of the epidermis. Most of the body is covered by thin skin, which is 0.003 inches (0.08 millimeters) thick. This skin contains hair follicles, sebaceous glands, and arrector pili muscles. The epidermis in thick skin may be six times thicker than the epidermis that covers the general body surface. Thick skin does not have hair, smooth muscles, or sebaceous glands. Thick skin on the palms of the hands, the fingertips, and soles of the feet may be covered by many layers of keratinized cells that have cornified.

12. Explain why the skin is a membrane and name the type of membrane that it is.

Membranes are thin layers of epithelial tissue usually bound to an underlying layer of connective tissue. Membranes cover, protect, or separate other structures or tissues in the body. The four types of membranes are: 1) cutaneous membranes; 2) serous membranes; 3) mucous membranes; and 4) synovial membranes.

The cutaneous membrane is skin. Skin consists of a layer of stratified squamous epithelium (epidermis) firmly attached to a thick layer of dense connective tissue (dermis). It differs from other membranes because it is exposed to air and is dry.

The serous membranes (or serosae) consist of simple squamous epithelium (a mesothelium) supported by a layer of connective tissue (areolar). These moist membranes line the closed, internal divisions of the ventral body cavity. The three types of serous membranes are: 1) the pleura, lining the pleural cavities and covering the lungs; 2) the peritoneum, lining the peritoneal cavity and covering the abdominal organs; and 3) the pericardium, lining the pericardial cavity and covering the heart.

The mucous membranes (or mucosae) consist of epithelial tissue (usually stratified squamous or simple columnar epithelia) on a layer of loose connective tissue called the lamina propria (from the Latin, meaning "one's own layer"). The mucosae line the body cavities that open to the exterior, such as the digestive, respiratory, reproductive, and urinary tracts. These membranes are kept moist by bodily secretions.

Synovial membranes are composed of connective tissue. They surround the cavity of joints, filling the space with the synovial fluid that they make. The synovial fluid lubricates the ends of the bones allowing them to move freely.

13. Explain how fingertips develop.

Fingerprints follow us our entire lives. Each little smudge singles us out as distinct individuals among billions of other human beings -- or at least that's what we've always been told.

Fingerprint ridges are formed during to the third or fourth month of fetal development.  A friction ridge is a raised portion of the epidermis on the digits (fingers and toes), the palm of the hand or the sole of the foot, consisting of one or more connected ridge units of friction ridge skin. These are sometimes known as "epidermal ridges" which are caused by the underlying interface between the dermal papillae of the dermis and the inter-papillary (rete) pegs of the epidermis. These epidermal ridges serve to amplify vibrations triggered, for example, when fingertips brush across an uneven surface, better transmitting the signals to sensory nerves involved in fine texture perception. These ridges may also assist in gripping rough surfaces and may improve surface contact in wet conditions.

Impressions of fingerprints may be left behind on a surface by the natural secretions of sweat from the eccrine glands that are present in friction ridge skin, or they may be made by ink or other substances transferred from the peaks of friction ridges on the skin to a relatively smooth surface such as a fingerprint card. Fingerprint records normally contain impressions from the pad on the last joint of fingers and thumbs, although fingerprint cards also typically record portions of lower joint areas of the fingers.

14. Explain the effect of excessive exposure to the sun on the skin.

Skin Cancer

Each year, more new cases of skin cancer are diagnosed in the U.S. than new cases of breast, prostate, lung, and colon cancer combined. One in five Americans will develop skin cancer in their lifetime. One American dies from skin cancer every hour. Unprotected exposure to UV radiation is the most preventable risk factor for skin cancer.

 

Melanoma

Melanoma, the most serious form of skin cancer, is now one of the most common cancers among adolescents and young adults ages 15-29. While melanoma accounts for about three percent of skin cancer cases, it causes more than 75 percent of skin cancer deaths. UV exposure and sunburns, particularly during childhood, are risk factors for the disease. Not all melanomas are exclusively sun-related—other possible influences include genetic factors and immune system deficiencies.

Nonmelanoma Skin Cancers

Non-melanoma skin cancers are less deadly than melanomas. Nevertheless, they can spread if left untreated, causing disfigurement and more serious health problems. There are two primary types of non-melanoma skin cancers: basal cell and squamous cell carcinomas. If caught and treated early, these two cancers are rarely fatal. 

·         Basal cell carcinomas are the most common type of skin cancer tumors. They usually appear as small, fleshy bumps or nodules on the head and neck, but can occur on other skin areas. Basal cell carcinoma grows slowly, and it rarely spreads to other parts of the body. It can, however, penetrate to the bone and cause considerable damage.

·         Squamous cell carcinomas are tumors that may appear as nodules or as red, scaly patches. This cancer can develop into large masses, and unlike basal cell carcinoma, it can spread to other parts of the body.

Premature Aging and Other Skin Damage

Other UV-related skin disorders include actinic keratoses and premature aging of the skin. Actinic keratoses are skin growths that occur on body areas exposed to the sun. The face, hands, forearms, and the “V” of the neck are especially susceptible to this type of lesion. Although premalignant, actinic keratoses are a risk factor for squamous cell carcinoma. Look for raised, reddish, rough-textured growths and seek prompt medical attention if you discover them.

Chronic exposure to the sun also causes premature aging, which over time can make the skin become thick, wrinkled, and leathery. Since it occurs gradually, often manifesting itself many years after the majority of a person’s sun exposure, premature aging is often regarded as an unavoidable, normal part of growing older. However, up to 90 percent of the visible skin changes commonly attributed to aging are caused by the sun. With proper protection from UV radiation, most premature aging of the skin can be avoided.

Cataracts and Other Eye Damage

Cataracts are a form of eye damage in which a loss of transparency in the lens of the eye clouds vision. If left untreated, cataracts can lead to blindness. Research has shown that UV radiation increases the likelihood of certain cataracts. Although curable with modern eye surgery, cataracts diminish the eyesight of millions of Americans and cost billions of dollars in medical care each year.

Other kinds of eye damage include pterygium (tissue growth that can block vision), skin cancer around the eyes, and degeneration of the macula (the part of the retina where visual perception is most acute). All of these problems can be lessened with proper eye protection. Look for sunglasses, glasses or contact lenses if you wear them that offer 99 to 100 percent UV protection.

Immune Suppression

Scientists have found that overexposure to UV radiation may suppress proper functioning of the body’s immune system and the skin’s natural defenses. For example, the skin normally mounts a defense against foreign invaders such as cancers and infections. But overexposure to UV radiation can weaken the immune system, reducing the skin’s ability to protect against these invaders.

V.           Reference/s:

Biology4kids.com. Retrieved on February 20, 2014 from  http://www.biology4kids.com/files/systems_integument.html

Retrieved on February 20, 2014 from http://sciencenetlinks.com/student-teacher-sheets/integumentary-system/

Retrieved on February 20, 2014 from http://sciencenetlinks.com/student-teacher-sheets/integumentary-system/

Retrieved on February 20, 2014 from http://www.augustatech.edu/anatomy/chapter5.html