Integumentary System

In general, burns are considered critical if any of the following conditions exists:

1. over 25% of the body has second degree burns 2. over 10% of the body has third degree burns or 3. there are third degree burns of the face, hands, or feet. Facial burns are dangerous because of the possibility of burned respiratory passageways, which can swell and cause suffocation. Joint injuries are troublesome because the scar tissue that eventually forms can severely limit joint mobility.

Malignant Melanoma

A cancer of melanocytes It accounts for only about 5% of skin cancers, and often deadly. Melanoma can begin wherever there is pigment; most such cancers appear spontaneously, but some develop from pigmented moles. It arises from accumulated DNA damage in a skin cell and usually appears as a spreading brown to black patch that metastasizes rapidly surrounding lymph and blood vessels. The chance for survival is about 50%

Cytoskeleton

A network of fibers that holds the cell together, helps the cell to keep its shape, and aids in movement a network of proteins inside a cell.

integrin

A receptor protein built into the plasma membrane that interconnects the extracellular matrix and the cytoskeleton

Merkel cells

Act as receptor cells found in the basal surface of the epidermis that have synaptic contacts with afferent nerves May be involved with light pressure detection

Sweat Glands

Also called sudoriferous glands, are widely distributed in the skin. Their number is staggering- more than 2.5 million per person. There are two types of sweat glands: apocrine and eccrine

Infections and Allergies

Athlete's Foot: an itchy, red, peeling condition of the skin between the toes, resulting from fungus infection. Also called tinea pedis Boils and carbuncles: Inflammation of hair follicles and sebaceous glands, common on the dorsal neck. Carbuncles are composite boils typically caused by bacterial infection Cold sores (fever blisters): Small fluid filled blisters that itch and sting, caused by a herpes simplex infection. The virus localizes in a cutaneous nerve, where it remains dormant until activated by emotional upset, fever, or UV radiation. Cold sores usually occur around the lips and in the oral mucosa of the mouth. Contact dermatitis: itching, redness, and swelling of the skin, progressing to blistering. Caused by exposure of the skin to chemicals (such as those in poison ivy) that provoke allergic responses in sensitive individuals. Impetigo: Pink, water filled, raised lesions (commonly around the mouth and nose) that develop a yellow crust and eventually rupture. Caused by a highly contagious staphylococcus infection; common in elementary school children Psoriasis: a chronic condition, characterized by overproduction of skin cells that results in reddened epidermal lesions covered with dry, silvery, scales. When severe, may be disfiguring. It is believed to be an autoimmune disorder which the immune system attacks a persons own tissues. Attacks often triggered by trauma, infection, hormonal changes, and stress.

Proximal

Closer to the point of attachment

Protects deeper tissues from: Desiccation (drying out)

Contains a waterproofing glycolipid and keratin.

Epithelial membranes

Covering and lining membranes; include cutaneous membrane (skin), mucous membranes and serous membranes. They all contain an epithelial sheet, and is always combined with an underlying layer of connective tissue. Simple organs.

Alpha and beta cells

DNA in alpha and beta cells are identical alpha cells make glucagon beta cells make insulin DNA is like a cookbook.

Developmental Aspects of Skin and Body Membranes

During the 5th and 6th months of fetal development, the soon to be born infant is covered with a downy type of hair called lanugo. When a baby is born, its skin is covered with vernix caseosa. This white, cheesy, looking substance produce by sebaceous glands protects the baby's skin while floating in its water filled sac inside the mother. The newborns skin is very thin, and blood vessels can easily be seen through it. Commonly, there are accumulations in the sebaceous glands, which appear as small white spots called milia, on the baby's nose and forehead. These normally disappear by the third week after birth. As the baby grows, its skin becomes thicker and moist, and more subcutaneous fat is deposited. During adolescence, the skin and hair become more oily as sebaceous glands are activated, and acne may appear. Acne usually subsides in early adulthood, and the skin reaches its optimal appearance when we are in our 20s and 30s. Then visible changes in the skin begin to appear as it is continually assaulted by abrasion, chemicals, wind, sun, and other irritants and as its pores become clogged with air pollutants and bacteria. As a result, pimples, scales, and various kinds of dermatitis or skin inflammation, become more common. During old age, the amount of subcutaneous tissue decreases, leading to the intolerance to cold so common in the elderly. The skin also becomes drier because of decreased oil production and declining numbers of collagen fibers, and as a result it may become itchy and bothersome. Thinning of the skin, another result of the aging process, makes it more susceptible to bruising and other types of injuries. The decreasing elasticity along with the loss of subcutaneous fat, allows bags to form under our eyes and our jowls begin to sag. By age 50 the number of hair follicles has dropped by 1/3 and continues to decline, resulting in hair thinning and some degree of baldness.

Eccrine Glands-Description

Eccrine sweat glands are coiled tubular glands The coiled tubular secretory portion of the gland, along with the coiled beginning of the duct, is located deep in the dermis, near the hypodermis. Secretory portion- simple cuboidal epithelium proximal duct- stratified cuboidal epithelium The uncoiled portion of the duct extends upward from its coiled base in a spiraled fashion and opens directly on the surface of the skin. -Distal duct- stratified cuboidal epithelium

Eccrine Glands

Far more numerous and found all over the body. They produce sweat, a clear secretion that is primarily water plus some salts (sodium chloride), vitamin C, traces of metabolic wastes (ammonia, urea, uric acid), and lactic acid (a chemical that accumulates during vigorous muscle activity). Sweat is acidic (pH from 4-6), a characteristic that inhibits the growth of bacteria, which are always present on the skin surface via a duct that opens externally as a funnel shaped pore. The eccrine glands are an important and highly efficient part of the body's heat-regulating equipment. They are supplied with nerve endings that cause them to secrete sweat when the external temperature or body temperature is high. When sweat evaporates off the skin surface, it carries large amounts of body heat with it. If internal temperature changes more than a few degrees from the normal 37 C (98.2), life threatening changes occur in the body.

Fibers of cytoskeleton

Intermediate filaments Microtubules microfilaments (made of actine) (micro) fibers allow cell to move or change shape and provide structure

collagen is

extracelular

distal

farther from the origin of a body part or the point of attachment of a limb to the body trunk

Apocrine Glands Overview

Lined by cuboidal epithelial cells that surround a central lumen. Apocrine glands secrete their products as packets of cytoplasm that bleb off of the apical surface. Apocrine sweat glands typically are larger and more productive than eccrine glands. They are characterized by a simple cuboidal epithelium and widely dilated lumen that stores the secretory product. Secretion from aprocrine glands contains protein, lipid, carbohydrate, ammonium, and other organic compounds. The ducts of the glands empty into an adjacent hair follicle. The bleb on the apical surface of the secretory cells suggested that the cell underwent apocrine secretion, but recent electron micrographs indicate that the cells use merocrine secretion.

synthesizes vitamin d

Modified cholesterol molecules in skin converted to vitamin D by sunlight

Skin Cancer

Numerous types of neoplasms (tumors) arise in the skin. Most skin neoplasms are benign and do not spread to other body areas. However, some skin neoplasms are malignant or cancerous and they tend to invade other body areas. Skin cancer is the single most common type of cancer in humans. 1 in 5 Americans now develops skin cancer at some point in their lives.

Exocytosis

Process by which a cell releases large amounts of material

Cells of dermis that produce protein (collagen) fibers of the dermis

fibroblasts

If a sebaceous gland's duct becomes blocked by sebum...

a whitehead appears on the skin surface. If the accumulated material oxidizes and dries, it darkens, forming a blackhead. Acne is an active infection of the sebaceous glands accompanied by pimples on the skin. It can be mild or extremely severe, leading to permanent scarring.

Dense Irregular Connective tissue (Dermis)

Support and connection of epidermis made of large protein fibers that connect one tissue with another

basal surface

The bottom layer of epithelial tissue that attaches to the basement membrane

Cutaneous Glands

The cutaneous glands are all exocrine glands that release their secretion to the skin surface via ducts. They fall into two groups: sebaceous glands and sweat glands. As these glands are formed by the cells of the stratum basale, they push into the deeper skin regions and ultimately reside almost entirely in the dermis.

Structure of the Skin

The skin is composed of two kinds of tissue. The outer epidermis is made up of stratified epithelium that is capable of keratinizing or becoming hard and tough. The underlying dermis is mostly made up of dense connective tissue. The epidermis and dermis are firmly connected. A burn or friction (such as the rubbing of a poorly fitting shoe) may cause them to separate, allowing interstitial fluid to accumulate in the cavity between the layers, which results in a blister. Deep to the dermis is the subcutaneous tissue, or hypodermis, which essentially is adipose tissue. It is not considered part of the skin but it does anchor the skin to underlying organs. Subcutaneous tissue serves as a shock absorber and insulates deeper tissues from extreme temperature changes occurring outside the body. It is also responsible for the curves that are more a part of a woman's anatomy than a man's.

Body membranes

cover surfaces, line body cavities, and form protective (and often lubricating) sheets around organs, fall into two major groups. 1. epithelial membranes (cutaneous, mucous, and serous) 2. connective tissue membranes (synovial membranes)

Dermis

The dermis is your "hide" It is a strong stretchy, envelope that helps to hold the body together. The dense (fibrous) connective tissues making up the dermis consists of two major regions- the papillary and the reticular areas. Like the epidermis, the dermis varies in thickness. The papillary layer is the upper dermal region. It is uneven and has fingerlike projections from its superior surface, called dermal papillae which indent the epidermis above. Many of the dermal papillae contain capillary loops, which furnish nutrients to the epidermis. Other house pain receptors (free nerve endings) and touch receptors called Meissners corpuscles. On the palms of the hands and soles of the feet, the papillae are arranged in definite patterns that form looped and whorled ridges on the epidermal surface that increase friction and enhance the gripping ability of the fingers and feet. Papillary patterns are genetically determined. The ridges of the fingertips are well provided with sweat pores and leave unique, identifiying films of sweat called fingerprints on almost anything they touch. The reticular layer is the deepest skin layer. It contains blood vessels, sweat and oil glands, and deep pressure receptors called Pacinian corpuscles. Phagocytes found here (throughout the dermis) act to prevent bacteria that have managed to get through the epidermis from penetrating any deeper into the body. Both collagen and elastic fibers are found throughout the dermis. Collagen fibers are responsible for the toughness of the dermis; they also attract and bind water and thus help to keep the skin hydrated. Elastic fibers give the skin its elasticity when we are young. As we age, the number of collagen and elastic fibers decreased and the subcutaneous tissue loses fat. As a result, the skin loses its elasticity and begins to sag and wrinkle. The dermis is abundantly supplied with blood vessels that play a role in maintaining body temperature homeostasis. When body temp is high the capillaries of the dermis become engorged, swollen, with heated blood and the skin becomes reddened and warm. This allows body heat to radiate from the skin surface. If the environment is cool and body heat must be conserved, blood bypasses the dermis capillaries temporarily, allowing internal body temperatures to stay high. The dermis also has a rich nerve supply. Many nerve endings have specialized receptor end organs that send messages to the central nervous system for interpretation when they are stimulated by environmental factors (pressure, temperature).

Epidermis

The epidermis is composed of up to five zones or layers called strata. from the inside out are the stratum basale, spinosum, granulosum, lucidum, and corneum. Like all epithelial tissues, the epidermis is avascular; that is, it has no blood supply of its own. Most cells of the epidermis are keratinocytes (keratin cells), which produce keratin, the fibrous protein that makes the epidermis a tough protective layer. The deepest cell layer of the epidermis, the stratum basale, lies closest to the dermis and contains epidermal cells that receive the most adequate nourishment via diffusion of nutrients from the dermis. These cells are constantly undergoing cell division, and millions of new cells are produced daily; hence its alternate name, stratum germinativum ("germinating layer"). The daughter cells are pushed upward, away from the source of nutrition to become part of the epidermal layers closer to the skin surface. They move away from the dermis and become part of the more superficial layers, the stratum spinosum and then the stratum granulosum. They then become flatter, increasingly full of keratin and finally die, forming the clear stratum lucidum. This latter epidermal layer is not seen in all skin regions; it occurs only where the skin is hairless and extra thick (palms of hands and soles of feet). The combination of accumulating keratin inside them, secreting a water repellent glycoprotein into the extra cellular space, and their increasing distance from the blood supply (in the dermis) effectively dooms the stratum lucidum cells and the more superficial epidermal cells because they are unable to get adequate nutrients and oxygen. The outermost layer, the stratum corneum is 20 to 30 cell layers thick. it accounts for about 3/4 of the epidermal thickness. the shingle like dead cell remnants, completely filled with keratin are referred to as cornfield or horny cells. Keratin is an exceptionally tough protein; its abundance in the stratum corneum allows that layer to provide a durable "overcoat" for the body , which protects deeper cells from the hostile external environment (air) and from water loss and helps the body resist biological, chemical, and physical assaults. The stratum corneum rubs and flakes off slowly and steadily and is replaced by cells produced by the division of the deeper stratum basale cells. We have a totally "new" epidermis every 25 to 45 days. Melanin, a pigment that ranges in color from yellow to brown to black, is produced by special cells called melanocytes found chiefly in the stratum basale. When the skin is exposed to sunlight, which stimulates the melanocytes to produce more of the melanin pigment, tanning occurs. The stratum basale cells phagocytize (eat) the pigment, and as it accumulates within them, the melanin forms a protective pigment umbrella over the superficial side of their nuclei that shields their genetic material (DNA) from the damaging effects of ultraviolet radiation in sunlight. Freckles and moles are seen where melanin is concentrated in one spot.

Sebaceous (Oil) Glands

The sebaceous glands, or oil glands, are found all over the skin except on the palms of hands and soles of feet. Their ducts usually empty into a hair follicle, but some open directly onto the skin surface. The product of the sebaceous glands, sebum (grease), is a mixture of oily substances and fragmented cells. Sebum is a lubricant that keeps the skin soft and moist and prevents the hair from becoming brittle. Sebum also contains chemicals that kill bacteria present on the skin surface from invading the deeper skin regions. The sebaceous glands become very active when male sex hormones are produced in increased amounts (in both sexes) during adolescence. Thus, the skin tends to become oiler during this period of life.

Burns

The skin is only about as thick as a paper towel. Yet, when it is severely damaged, nearly every body system suffers. Metabolism accelerates or may be impaired, changes in immune system occur, and the cardiovascular system may falter. A burn is tissue damage and cell death caused by intense heat, electricity, UV radiation (sunburn), or certain chemicals (such as acids) When the skin is burned and its cells are destroyed, two life threatening problems result. First, the body loses its precious supply of fluids containing proteins and electrolytes as these seep from the burned surfaces. Dehydration and electrolyte imbalance follow and lead to a shutdown of the kidneys and circulatory shock (inadequate circulation of blood caused by low blood volume). To save the patient, the lost fluids must be replaced immediately. The volume of fluid lost can be estimated indirectly by determining how much of the body surface is burned using the rules of nines. This method divides the body into 11 areas , each accounting for 9 percent of the total body surface area, plus an additional area surrounding the genitals representing 1 percent of body surface area. later infection becomes the most important threat and is the leading cause of death in burn victims. Burned skin is sterile for 24 hours. But after that, pathogens such as bacteria and fungi easily invade areas where the skin has been destroyed and multiply rapidly in nutrient rich environment of dead tissues. In first degree burns only the epidermis is damaged. The area becomes red and swollen. Sunburn is usually first degree burns. Second degree burns involve injury to the epidermis and the upper region of the dermis. The skin is red and painful, and blisters appear. Because significant numbers of epithelial cells are still present, regrowth of the epithelium can occur. First and second degree burns are referred to as partial thickness burns Third degree burns destroy the entire thickness of the skin, so these burns are also called full thickness burns.

Hair

There are millions of hairs scattered all over the body. Other than serving a few minor protective functions- such as guarding the head against bumps, shielding the eyes via eyelashes, and helping to keep foreign particles out of the respiratory tract via nose hairs- our body hair has lost much of its usefulness A hair produced by the hair follicle is a flexible epithelial structure. That part of the hair enclosed in the follicle is called the root The part projecting from the surface of the scalp or skin is called the shaft. A hair is formed by division of well nourished stratum basale epithelial cells in the matrix (growth zone) of the hair bulb at the inferior end of the follicle. As the daughter cells are pushed farther away from the growing region, they become keratinized and die. Thus the bulk of the hair shaft is dead material and almost entirely protein. Each hair consists of a central core called the medulla surrounded by a bulky cortex layer. The cortex is enclosed by an outermost cuticle formed by a single layer of cells that overlap one another like shingles on a roof. This arrangement of the cuticle cells helps to keep the hairs apart and keeps them from matting. The cuticle is the most heavily keratinized region; it provides strength and helps keep the inner hair layers tightly compacted. The cuticle tends to wear away at the tip of the shaft, allowing the keratin fibrils in the inner hair regions to frizz. Hair pigment is made by melanocytes in the hair bulb, and varying amounts of different types of melanin (yellow, rust, brown, and black) combine to produce all varieties of hair color. When the hair shaft is oval, hair is smooth and silky and the person has wavy hair. When the shaft is flat the hair is kinky and curly. If it round the hair is straight and tends to be coarse. Hairs are found everywhere except the palms, soles of feet, nipples, and lips. Humans are born with as many hair follicles as they will ever have and hairs among the fastest growing tissues in the body. Hormones account for hairy regions-the scalp, and public and axillary areas.

Skin Color

Three pigments contribute to skin color: 1. The amount and kind (yellow, reddish brown, or black) of melanin in the epidermis. 2. The amount of carotene deposited in the stratum corneum and subcutaneous tissue. Carotene is an orange-yellow pigment found in abundant amounts in carrots and other orange, deep yellow, or leafy green vegetables. The skin tends to take on a yellow orange cast when large amount of carotene rich foods are eaten. 3. The amount of oxygen rich hemoglobin (pigment in red blood cells) in the dermal blood vessels. People who produce a lot of melanin have brown toned skin. In Caucasian people, who have less melanin, the crimson color of oxygen rich hemoglobin in the dermal blood supply flushes through the transparent cell layer above and gives the skin a rosy glow. Skin color is also influenced by emotional stimuli, and many alterations in skin color signal certain disease states: Redness or erythema: Reddened skin may indicate embarrassment (blushing), fever, hypertension, inflammation, or allergy Pallor, or blanching: under certain types of emotional stress (fear, anger, and others), some people become pale. Pale skin may also signify anemia, low blood pressure, or impaired blood flow into the area Jaundice or a yellow cast: An abnormal yellow skin tone usually signifies a liver disorder in which excess bile pigments are absorbed into the blood, circulated throughout the body, and deposited in body tissues. Bruises or black-and-blue- marks: black and blue marks reveal sites where blood has escaped from the circulation and has clotted in the tissue spaces. Such clotted blood masses are called hematomas. An unusual tendency to bruising may signify a deficiency in vitamin C in the diet or hemophilia (bleeders disease).

Secretory cells

deep in dermis empty sweat into a duct

hemoglobin

a protein with iron core and carries oxygen

Nails

a scale like modification of the epidermis that corresponds to the hoof or claw of other animals. Each nail has a free edge, a body, and a root. the borders of the nail are overlapped by skin folds, called nail folds. The thick proximal nail fold is called the cuticle. The stratum basale of the epidermis extends beneath the nail as the nail bed. its thickened proximal area, called the nail matrix is responsible for nail growth. As the nail cells are produced by the matrix they become heavily keratinized and die. Thus, nails are mostly nonliving material. Nails are transparent and nearly colorless but look pink due to rich blood supply in the underlying dermis. The exception to this is the region over the thickened nail matrix that appears as a white crescent and is called the lunula. When the supply of oxygen in the blood is low, the nail beds take on a cyanotic (blue) cast.

Irregular connective tissue

arranged in all directions so they can resist force in all directions Skin must be this way

Proteoglycans

carb skeletons with protein attachments big molecules made of proteins and carbs

Makeup of the basement membrane

collagen, laminin, glycoproteins

Desmosomes

collection of proteins strong junction, links cytoskeletons button like protein connection

Hair follicles

compound structures. the inner epidermal sheath is composed of epithelial tissue and forms the hair. the outer dermal sheath is actually dermal connective tissue. this dermal region supplies blood vessels to the epidermal portion and reinforces it. Its nipple like papilla provides the blood supply to the matrix in the hair bulb. Small bands of smooth muscle cells-arrestor pili- connect each side of the hair follicle to the dermal tissue. When these muscles contract the hair is pulled upright (goosebumps). This is not useful to humans.

Aids in excretion of urea and uric acid

contained in perspiration produced by sweat glands

Basal lamina

contains collagen, laminin, and proteoglycans laminin is a large glycoprotein that anchors the basal cells of the epidermis to the collagen proteins of the basal lamina additional collagen proteins anchor the collagen of the basal lamina to the large collagen fibers in the dermis below.

Protects deeper tissues from: Thermal (heat or cold) damage

contains heat/cold/pain receptors

The clear area around stained collagen is

ground substance

Protects deeper tissues from: Bacterial damage

has an unbroken surface and "acid mantle" (skin secretions are acidic, and thus inhibit bacteria) Phagocytes ingest foreign substances and pathogens, preventing them from penetrating into deeper body tissues.

Protects deeper tissues from: Chemical damage (acids and bases)

has relatively impermeable keratinized cells; contains pain receptors, which alert the nervous system to possible damage.

Aids in body heat loss or heat retention (controlled by the nervous system)

heat loss: by activating sweat glands and allowing blood to flush into skin capillary beds. heat retention: by not allowing blood to flush into skin capillary beds.

diffusion

high to low concentration

how does sweat start out

hypertonic when first secreted by secretory cells of eccrine glands, then hypotonic on the surface

The skin appendages

include cutaneous glands, hair and hair follicles, and nails. Each of these appendages arises from the epidermis and plays a unique role in maintaining body homeostasis.

Keratin protein forms the

intermediate filaments of the cells cytoskeleton

cytoskeleton

intracellular

keratin is

intracelular

laminis

large glycoprotein

Integument

simply means "covering" The skin is essential because it keeps water and other precious molecules in the body. It also keeps water and other things out. It is pliable yet tough Without our skin, we would fall prey to bacteria and perish from water and heat loss.

Apocrine glands

largely confined to the axillary and genital area of the body. They are usually larger than eccrine glands, and their ducts empty into hair follicles. Their secretion contains fatty acids and proteins as well as all the substances found in eccrine gland secretion. It may have a milky or yellowish color. The secretion is odorless, but when bacteria that live on the skin use its proteins and fats as a source of nutrients for their growth, it takes on an unpleasant odor. Aprocrine glands begin to function during puberty under the influence of androgens (male sex hormones). Apocrine glands play a minimal role in thermoregulation. Their precise function is not yet known, but they are activated by nerve fibers during pain and stress and during foreplay.

Eccrine Sweat Glands Overview

localize to the dermis and upper region of the hypodermis. The secretory gland is coiled and consists of secretory, epithelial cells and an outer layer of myoepithelial cells that are contractile. The secretory cells are a mix of light and dark staining cells. The light staining cells produce a watery substance similar in composition to an ultra filtrate of blood, whereas the dark staining cells secrete glycoprotein. The ducts stain darker and have a double layer of cuboidal cells which reabsorb ion and water. The ducts spiral to the surface of the epidermis to release sweat. The my-epithelial cells can contract to rapidly express sweat on the surface of the skin.

Cavity within a duct is a

lume; holds a substance

Protects deeper tissues from: Ultraviolet radiation (damaging effects of sunlight)

melanin produced by melanocytes offers protection from UV damage.

The skins functions

most but not all are protective. It cushions and insulates the deeper body organs and protects the entire body from bumps and cuts, chemical damage, thermal damage, ultraviolet radiation, and bacteria. The uppermost layer of the skin is full of keratin and cornified, or hardened in order to prevent water loss from the body surface. the skins rich capillary network and sweat glands (both controlled by the nervous system) play an important role in regulating heat loss from the body surface. The skin acts as a mini excretory system; urea, salts, and water are lost when we sweat. The skin also manufactures several proteins important to immunity and synthesizes vitamin D. (Modified cholesterol molecules located in the skin are converted to vitamin D by sunlight. The cutaneous sensory receptors which are actually part of the nervous system, are located in the skin. The tiny sensors include: touch, pressure, temperature, and pain receptors, provide us with a great deal of information about our external environment. They alert us to bumps and the presence of tissue-damaging factors as well as to feel of wind in our hair and a caress.

stratified

multiple layers

Dead cells

no nuclei

simple

one layer

Regular connective tissue

parallel tendons and ligaments

cell membrane composition

phospholipids and proteins

Protects deeper tissues from: Mechanical damage (bumps)

physical barrier contains keratin, which toughens cells, and pressure receptors, which alert the nervous system to possible damage.

Collagen

predominant fiber of the dermis

Keratnocytes

produce keratin

ground substance

provide cushion and increase transport secreted by fibroblasts made of water, adhesive proteins, and proteoglycans

Cells of sebaceous gland are

simple cuboidal

Langerhans Cells

specialized cells take up foreign antigen and present it on their surface to lymphocytes (cells of the immune system)

Summary of layers from deepest to most superficial

stratum basale stratum spinosum stratum granulosum stratum lucidum (thick, hairless skin only) stratum corneum

basil lamina

supporting sheet between the epithelium and connective tissue -thin noncellular sheet consists of proteins secreted by the epithelial cells -acts as a supportive filter- it determines which molecules from capillaries in the connective tissue are allowed to enter the epithelium -also acts as scaffolding in which regenerating epithelial cells can migrate

apical surface

surface of an epithelial cell that faces away from the basement membrane

The skin and its derivatives...

sweat and oil glands, hair, and nails serve a number of functions, mostly protective. together these organs are called the integumentary system.

keratin is a protein that is part of

the cytoskeleton of all cells of the body

squamous

thin and flat

The conversion of ammonia into a less toxic substance produces

urea by the liver, flushed out by the kidney

Cutaneous membrane

your skin. its superficial epidermis is composed of a keratinizing squamous epithelium the underlying dermis is mostly dense (fibrous) connective tissue. the cutaneous membrane is exposed to air and is a dry membrane