Integumentary System I

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What is the mucocutaneous junction? Describe it.: Where the skin meets the mucous membranes, it is reddish due to blood in capillaries, you can see blood due to a lack of keratin in cells.
What are the appendages of the skin?: These are structures derived from epidermis and associated with the skin. They include nails, hair, and glands (sweat, sebaceous ceruminous).
Desribe the Epidermis, what type of epithelium is it? What is it derived from? How many layers does it have?: It is stratisfied squamous keratinized type epithelium. It is derived from ectoderm, it is avascular and consists of 5 well defined layers.
Describe the dermis. What type of tissue is it? What is it derived from?: The dermis is the thickest layer of skin, it consists of dense irregular connective tissue. It is derived from mesenchyme and is vascular (supplies nutrients to the epidermis).
What is the papillary layer? Where does it lie? What does it contain?: Part of the dermis. The Papillary layer is superficial, and is immediately underneath the epidermis, it contains the dermal papille which are finger like projections.
What is the Reticular layer? What does it contain? Describe it.: The reticular layer is the deepest and thickest layero f the dermis, it contains appendages.
What is the Hypodermis? Describe it. What are some other names for it?: The lowest layer. NOT part of the skin. It is made up of areolar connective tissue. It is a layer of underlying loose CT. It is also called the subcutaneous fascia or superficial fascia.
What does the hypodermis consist of?: Primarily fat and is called the panniculus adiposus in the region of the abdomen.
What are dimples?: Where the dermis is tightly attached to the underlying deep fascia or bone.
List 8 functions of the skin.: Mechanical protection, Maintenance of body fluids, maintenance of body temperature, synthesis of vitamin D, immunity, reception of sensory stimuli, organ of communication, repair
Describe specifics of the mechanical protection that skin provides.: Physically protects against mechanical trauma, creates a physical barrier to bacteria etc., blocks U.V. rays.
Describe the specifics of maintenance of body fluids.: Prevents dessication (prevents body from losing or gaining fluids), carries out excretion (sweat glands excrete water, ions, urea, and ammonia)
Describe the specifics of the synthesis of vitamin D.: Works with 4 other organs to produce vitamin D. Precursor of vitamin D is converted by UV rays to cholecalciferol (another precursor. Liver further processes it to 25-hydroxy cholecalciferol. Kidney converts this to vitamin D.
Describe the maintenance of body temperature.: Sweat glands secrete serous fluid that cools the body. Blood vessels bring heat to the surface via vascular plexuses. Adipose serves as insulation.
Describe the specifics of immunity and skin's role.: Skin contains wandering cells of immunity system.
Describe the specifics of reception of sensory stimuli.: Lots of sensory receptors are found in the skin. pain, touch, pressure, temperature
Describe the organ of communication function of the skin.: Can tell when someone is embarrassed or nervous. Can tell about the functioning of the body via skin appearance. Cyanosis (blue), jaundice, age, nerve damage (due to loss in dermatome patterns).
Describe the specifics of the skin repair function of skin.: Skin repairs itself to prevent loss of functions. It also forms scars.
Describe the structure of the epidermis. What kind of tissue is it made of? Where does it get its nurients from?: It is composed of stratified squamous keratinized epithelium. It is avascular so all nutrients must diffuse up from dermis.
List the 5 layers of the epidermis starting from deepest toward most superficial.: Stratum Basale (Germinativum)
Stratum Spinosum
Stratum Granulosum
Stratum Lucidum
Stratum Corneum
What is the Stratum Malphigi? What does it consist of?: It consists of two layers the stratum basale and spinosum.
Describe the stratum basale (germinativum) what is its diagnostic characteristic? Describe the morphology of the cells. What processes go on here?: Deepest layer, diagnostic is a single layer of cells that sit on basement membrane. Cells are cuboidal and columnar in shape. Serves as a site for germinitivum (makes more epidermis cells via mitosis).
Describe the Stratum Spinosum. What do its cells look like? What is its diagnostic characteristic? Why does this diagnostic characteristic form?: Stratum Spinosum consists of several layers of cells. The cells are irregulary shaped. The diagnostic characteristic of this layer is that the cells are separated by narrow space or cleft which is crossed by intercellular bridges or spins (hence spiny appearance). The spines are where desmosomes attach and hold the cells together. The gaps form due to shrinkage during tissue processing.
Describe the Stratum Granulusom. What do its cells look like? What is its diagnostic characteristic?: Stratum Granulosum consists of a narrow layer that is 3-5 layers thick. The cells are flattened and nuclei are disappearing. Its diagnostic is darker staining due to prescence of numerous keratohyalin granules.
Describe the stratum lucidum. What is its diagnostic characteristic? What other layer is it considered part of?: Stratum lucidum is thin layer 2-3 cells thick. The cells and nuclei are not visible (diagnostic characteristic) b/c the cells are dead. It is considered part of the stratum corneum.
Describe the stratum corneum. What do its cells look like? What is in the cells? What is the most superfical part of this laye called?: The stratum corneum has numerous layers of dead cells, it has no nuclei visible (diagnostic characteristic) and its cells are filled with keratin (membrane bound bags called squames). Most superficial cells sloughing off that is called stratum disjunctivum.
Describe thick skin. What is another name for it? What layer is it actually the thickening of? What is its diagnostic characteristic? Where is the skin thickest?: Thick skin also known as glabrous skin. It lacks hair and sebaceous glands (diagnostic). IT is the thickening of the epidermis only. The skin is thickest on the soles of the feet and on the palms. 1 mm thick
Describe the thin skin. What is it also known as? What are its diagnostic characteristics? (2) What layer is lacking? Where on the body is it located?: Thin skin is also known as hairy or nonglabrous skin. It has the diagnostic characteristics of presence of hair and sebaceous glands and has a reduced thickness of stratum corneum, granulosum spinosum. The stratum lucidum is absent. It is located on the rest of the body that does not have thick skin. (Eyelids are thinnest)
What are the 4 types of cells found in the epidermis?: Keratinocyte, Melanocytes, Langerhans cells, and Merkel cells.
What do Langerhans cells do? Where are they found? What do they look like? How does their morpholgy help in their function? What is their origin?: Langerhans cells are cells of the immune system. They are found scattered throughout the stratum spinosum. They are stellate shaped with many branches and hence are also called dendritic cells. Their cytoplasm is clear or light staining. They DO not have desmosomes so they can move. They arise from monocytes or macrophages.
Give a short description of Keratinocytes. What do they do? What are they derived from?: Keratinocytes are the principal cell type of the epidermis. They are mostly all cells of the epidermis. They produce keratin and are derived from ectoderm.
How do Langerhan's cells participate in the immune response? What is an example of such a reaction?: Langerhan's cells participate in immune responses by presenting antigens to T-helper cells during hypersensitivity reactions such as contact dermatitis.
Give a short description of Melanocytes. What is their function? What layer are they found in? What is their origin?: Melanocytes are pigmented cells of the epidermis. They give skin part of its color. They are found in the stratum basale and are neural crest in origin.
What are Merkel cells? Where are they found? What do they look like? What do they contain? What function do they serve?: Merkel cells are a small clear cell in the stratum basale they contain dense core vesicles like cells in the adrenal medulla. They do NOT contain catecholamines. Each cell is innervated by a single axon. They are slow adapting cutaneous mechanoreceptors. They are responsible for light touch and constancy of it (still know somthing is there).
How does the epidermis create a protective barrier?: It does this by producing a layer of dense impenetrable, dead cells. This layer of dense cells prevents the passage of substances through epidermis.
What is the process whereby cells undergo differentiation and maturation as they migrate to the surface? How long does this take?: The process is called cytomprphosis. This takes approximately 3-4 weeks for cells to migrate from bottom to top.
What is Keratin made up of?: A family of fibrous proteins that make up intermediate filaments. (40-70,000 mw protein)
What are the two different phases cells can be in? What layers are undergoing what phase?: Degeneration phase (stratum corneum, stratum lucidum, stratum granulosum) or degeneration phase (Stratum spinosum, stratum basale)
How does stratum basale participate in the process of keratinization? Describe its morphology.: It is where keratin first appears. There are numerous desmosomes for mechanical attachement to adjacent cells and hemidesmosomes for attachement to the extracellular matrix. IT principal function is proliferation.
What happens in the stratum spinosum during keratinziation and cytomorphisis? What two types of structures appear within the cell.: In the stratum spinosum more keratin is produced and fills the cytoplasm. Tonofilaments increase in quantity as cells move toward the stratum granulosum. As the cell moves upward keratin formes bundles called tonofibrils. Lamellar granules appear in the cytoplasm.
WHat is a bundle of keratin called? What type of filament is it?: tonofilaments of cytokeratin. It is intermediate filament.
What are lamellar granules? What are they rich in?: First found in the stratum spinosum, they are membrane bound packets of light and dark bands that are extruded as the cells move toward the stratum granulosum. They are rich in glycolipids.
How does the stratum granulosum participate in cytomorphisis? What type of granules appear in this layer? What do these granules do?: Keratohalin granules appear in this layer. Also secretes lamellar granules (rich in glycolipids) that form a waterproof substance between the cells. Also intercellular space increases 30x. Cells also begin to die in this layer.
What are keratohyalin granules?: Dark irregular shaped granules/cytoplasmic inclusions that are not membrane bound and are found in the stratum granulosum.
What is Filaggrin?: A protein that cross links tonofilaments, first found in the stratum granulosum.
What is involucrin? What does it do? Where is it found? What other protein is it associated with?: A protein first produced in the stratum spinosum. It is associated with increased levelss of tranglutaminase (creates cross linking of involucrin onto cell mebrane). This creates a water impermeable cell membrane that causes cell death.
How is the stratum lucidum associated with cytomorphosis? What are its characteristics? What do its cells look like?: In the stratum lucidum the keratinocytes are dead, there are no nuclei present and losts of waterproofing. Cells are also full of keratin in more complex forms.
What is eliden? Where is it found?: Eliden is a transformed keratohyalin granule found in the stratum lucidum.
How does the stratum corneum participate in cytomorphisis? What do the cells of this layer look like? What about granules?: The stratum corneum consists of flattened squamous cells called squames. The nuclei of the cells are gone and all the cells are dead. The cells must be dead to form a proper watertight barrier. The plasma membrane is packed with keratin. The plasma membrane is thickened with non-keratinous material. NO keratohalin granules or lamellar granules are remaining.
What is an epidermal proliferation unit (EPU)? Why does it exist?: Vertical stacks of cells that interlock with adjacent squames. It is the most efficient way to pack cells together.
Describe the process of how an EPU (epidermal proliferation unit) is formed and how long this process takes.: In an EPU a single stem cell is located in the center. This stem cell gives rise to 10-11 basal cells that migrate to the periphery. They differentiate as they move laterally. As the proliferation occurs, cells move upward as a group. They move up about one cell a day. It takes 1 month to move from bottom to top of the epidermis.
What is fibronectin? Where is it found?: Fibronectin is an adhesion glycoprotein in the basement membrane that regulates the rate of keratinization.
What is Epidermal growth factor?: Epidermal growth factor stimulates the proliferation of keratinocytes.
Describe Psoriasis. What is its cause? How does it occur? What are the characteristics of the epidermis of a person with psoriasis?: Psoriasis is a chronic skin condition characterized by patches of red-brown area with whitish scales. It is due to excessive proliferation of keratinocytes. It is caused because it takes cells 1 week to reach th surface instead of 4 weeks. The epidermis is not fully differentiated: cells not fully keratinized, large spaces between cells because lamellar granules are not secreted, the integrity of the epidermis is compromised.
Describe eczema. What layers does it affect? What is it characterized by? What is the origin of the disease?: Eczema effects the epidermis and the dermis. It is characerized by edema, exudation, crusting and severe itching (pruritus). Dermis also affected: edema and infiltration of lymphocytes moncytes and eosinophils. Cause thought to be immunological in origin.
What is Phemphigus? How serious is it? What is its cause? What sort of symptoms does it display?: Phemphigus is a potentially fatal skin disease that is an autoimmune disease against desmosome proteins (cadherins) in epidermis. It causes severe blistering and loss of fluids, as well as entrance of infections.
Describe basal cell carcinoma. How common is it? What cells in what layer does it effect? What does it do? Does it metastasize often?: Basal cell carcinoma is the most common of all skin cancers, it affects the keratinocytes in the basal layer. It destoys local tissue but does not metastasize readily.
Describe Squamous cell carcinoma. How common is it? What are some of its causes? Does it metastasize often?: Squamous cell carcinoma is the 2nd most common skin cancer. IT has avariety of causes such as UV, X-rays, chemical agents, and arsenic
What is DMSO? WHat does it do? What is it used as an unofficail remedy for?: Dimethyl sulfoxide is a penetrating agent of skin, it carries other substances with it. The elderly use it as an unofficial remedy for arthritis because it soothes pain.
What 3 pigments are responsible for skin color?: Melanin, Carotene, and oxyhemaglobin.
Describe melanin. What color is it? What is it produced by?: It is a brown pigment produced by the skin.
Describe carotene. Where is it deposited? What is it obtained from?: Carotene is an exogenous plant pigment depositited in stratum corneum or adipose cells. (yellow). Eat lots of carrots and you will turn orange.
Describe oxyhemaglobin. WHat color is it?: Oxyhemaglobin is located in RBC's of blood vessels of the dermis (red).
What cells produce melanin pigment? Where are they located?: Melanocytes are the only cell in the epidermis that produces melanin pigment and it is located in the stratum basale.
What are melanocytes also known as? Why? What are they derived from? Describe their morphology.: Melanocytes are also known as clear cells because they have no desmosomes attaching it to surrounding cells so it is able to shrink and form a clear region around it. It is highly branched. It is derived from the neural crest.
What is melanocyte's distribution in normal and pigmented skin? What about ratio of melanocyte/epidermal cell? Where is pigmented skin located?: In normal skin there are about 1000 melanocytes per square mm. 1/every 10 epidermal cells. In pigmented skin there are 2000 melanocytes/square mm and 1/every 4 epidermal cells. Pigmented skin is located on the face, forhead, areolae of the nipple and genital skin.
What is the difference in skin color based on?: The difference in skin color is due to the rate and number of melanin granules produced and transferred to the keratinocytes.
What is a melanin epidermal unit composed of? Where is it located?: A melanin epidermal unit is composed of melanocyte and associated keratinocytes. It is located in the stratum basale and spinosum.
What is tyrosinase? Where is it located? What does it do?: Tyrosinase is in melanocytes and converts tyrosine into melanin within vesicles.
How do melanocytes produce melanin? What kind of secretion is it?: They use tyrosinase to convert tyrosine into melanin within vesicles. The vesicles first form premelanosomes in the melanocyte(elongated particles with fibrillar substructure that arise from golgi). Next, melanosomes are formed by producing more melanin. This continues until melanin granules are formed. Thes migrate lout to the ends of branches, the end of the process in pinched off into the cytoplasm of keratinocytes. (cytocrine secretion)
What happens to melanin granules in keratinocytes? What do darker skinned races have that others do not?: The melanin granules fuse with lysosomes to form a melanosome complex which forms a cap of complexes over the nucleus. The complexes slowly degenerate. The dark skinned races have increased number of melanosomes, longer lasting melanosomes, and granules in all layers.
What is the purpose of melanin?: Protection against UV rays from reaching and damaging chromosomes in keratinocytes undergoing mitosis.
What two types of ultraviolet light are people commonly exposed to? What effects do these have?: UVA (320 nm) causes wrinkling and sagging of skin, also increases cancer risk, it does not burn the skin, and is most used by tanning salons.

UVB (370 nm)
Induces inflammation of BV's in dermis, casue of sunburning and most block this wavelength.
What is tanning and what is it due to?: It is due to immediate darkening of melanin. It as also an increase in tyrosinase activity over several days of continued exposure.
What is wrong with albino's?: They have no tyrosinase but same number of melanocytes.
What is Vitiligo? What symptoms does it have? What sort of treatment can one recieve?: Vitiligo is a depigmentation disorder which is a genetically inherited defect in skin and hair. It is characterized by scattered patches of white skin and white hair where the melanocytes have been destroyed. Treatment is cosmetic or hydroquione treatment to reduce the formation of melanin in normal areas of skin.
What is a freckle due to?: Slightly higher concentration of melanin granules.
What is a nevus?: A mole or benign localized overgrowth of melanocytes arising during early life.
What is a malignant melanoma?: Carcinoma of melanocytes. Extremely malignant.
What two layers does the dermis have?: The papillary and reticular layers.
Describe the papillary layer. Where is it located? What type of tissue does it contain? What type of structures does it contain?: The papillary layer is the thinner of the 2 layers and is located subjacent to the epidermis. It is composed of modified areolar CT> IT contains dermal papillae which are finger like projections of connective tissue.
Describe the epidermal-dermal junction. What is its purpose?: The epidermal dermal junction is irregular due to dermal papillae, the dermal papillae interdigitate with the epidermal pegs or ridges and it helps to prevent shearing forces from seperating the two layers.
Describe the shape of papille in thick skin. How do these features help in function?: In thick skin the interpapillary peg of the epidermis divides primary dermal ridge into 2 secondary ridges, the primary dermal ridges correspond to the epidermal ridge (friction ridges). These ridges improve grip.
Describe the papille of thin skin.: Thin skin simply has rounded bumps or mounts of connective tissue.
Describe the reticular layer, what kind of tissue is it composed of? What types of fibers is it rich in?: The reticular layer is the thickest layer of the dermis, it is composed of dense irregular irregular CT. It is rich in collagen and elastic fibers.
What are the cleavage Lines of Langer? Why are they important?: The cleavage lines of langer are the predominant direction of bundles of collagen fibers in a region of the body. They are important for surgery so that incisions made parallel to the the LL do not gape open. If you cut across them, a large scar will form.
What are striae? Why do they occur?: Straie are stretch marks where the skin is pulled too tight and the dermis slowly tears but the epidermis is not broken. The gap is repaired with scar tissue. It occurs in pregnancy, obesity and weight lifters.
Where is the blood supply of the skin derived from?: IT is derived from the subcutaneous plexus and from arteries in subcutaneous fascia.
WHat are the 3 layers or plexuses of vessels associated with the skin in order of deepest to most superficial?: The subcutaeneous plexus, the cutaneous plexus, and the subpapillary plexus.
Describe the subcutaneous plexus. Where is it located?: Subcutaneous plexus is the deepest plexus and is located in the hypodermis (subcutaneous fascia).
Where is the cutaneous plexus located?: It is located at the dermal-subcutaneous or dermal-hypodermal junction.
WHere is the subpapilary plexus located?: It is located in the papillary layer and capillaries loops run up into the dermal papillae.
Why is vasculature uniquely important in the skin?: It plays a key role in temperature regulation of the body.
What are AV shunts?: Glomulos or a bunch of small blood cells that run parrallel to the skin and are a coil of small vessels that run from the arteriol to the vein.
What is the state of AV shunts during normal temperature?: They are partially closed so blood runs to the surface.
What is the state of AV shunts during high temperatures?: Passive dialation of arterioles and veins allows blood to flow to surface and irradiate heat.
What happens during low temperature to AV shunts?: AV shunts are clamped closed and blood is kept from heading towards the surface.
Are there AV shunts in Apical skin? (Finger/toe tips, nail beds, nose, lips eyses): Yes but not in the rest of the body. They regulate via sympathetic release of norepinephrine that causes vasoconstriction of arterioles. It also releases acetylcholene which usually causes vasodilatation.
What are decubitus ulcers and what are they caused by?: They are bedsores caused by compromised circulation to an area of skin.
WHat is a contusion?: A bruise.
What is an erythema?: A redness of the skin due to engorged capillaries.
What is capillary hemangioma? WHen does it appear?: Capillary hemangioma is a benign vascular tumor of dermal capillaries. It appears soon after birth as a "strawberry mark" or "port wine stain".
Describe what hair is made of.: IT is a hard keratinous epithelial fiber that is composed of keratinocytes.
Describe hair follicle. What layers is it in? What is its structure?: This is a tubular invagination of the epidermis. It extends down through the dermis into the hypodermis. Each follicle is surrounded by connective tissue called the dermal sheath.
What two types of sheaths does the hair follicle contain? Where are they located?: The external root sheath is an extension of strata basale and spinosum downward. The internal root sheath goes halfway up follicle from root of hair.
What are the three regions the hair follicle is subdivided into? Where are they located?: The three regions are the hair shaft (the part of the hair that protrudes above the surface), the root of hair (reaches from the centor of hte follicle down to the bulb), and the bulb (an enlargement at the deep end of the hair follicle it contains the dermal papillae composed of connective tissue)
What is the Matrix or germativum zone?: Where the proliferation of keratinocytes occurs at the base of the follicle, it is the equivalent of the stratum basale in the epidermis. The keratinocytes move upward and differentiate by keratinaization process.
What is the Keratogenous zone?: This is where the cells become fully keratinized as they move upward, in the hair hard keratin is formed (not soft keratin like in the epidermis)
What is the difference between hard and soft keratin?: Hard keritin contains more sulfer and more cross links that soft keratin and is found in hair as opposed to in the epidermis.
What is the internal root sheath? What is it derived frome? What does the layer contain?: It is derived from outside the region of the matrix as cells move upward. The layer contains soft keratin. The layer disappears halfway up the follicle near the opening of the sebaceous gland duct into the follicle.
What are the 3 layers of the hair shaft? Where are they located? What type of keratin do they contain?: Cuticle of hair- on outside of hair shaft (hard keratin)
Cortex - makes up bulk of shaft (hard keratin)
Medulla - located in the center (soft keratin)
How is pigment in hair produced?: Melanocytes in hair produce pigment which is transferred to keratinocytes.
What does hair color depend on? Match the various types of hair color with their morpholgy.: Color of hair depends on type of melanin.
Pheomelnin = yellow and develops from tryptophan.
Eumelanin = brown and black, develops from tyrosine.
Grey hair = melanocytes lack tyrosinase to produce melanin.
White hair = pigment lacking but air pockets in hair reflect white light.
What do the arrector pili muscles do? What kind of muscle are they?: They are smooth muscle that stands hair erect, creates goose bumps due to insertion on to dermal papille and dermal sheath.
What are sebacious glands? What kind of secretion do they produce? Where in the hair shaft do they produce this?: Sebacious glands are an oil gland in the angle of the hair shaft. It empties into the upper part of the follicle.
What are the 3 phases of hair growth? Does it grow continually?: 1. Growth Phase = anagen phase
2. Transitional phase = catagen phase
3. Resting phase = telogen phase

No hair growth is cyclic in that haiar is lost and replaced periodically.
What occurs during the growth or anagen phase?: Matrix proliferates (soft keratin), hair grows in length at rate of 0.4-0.5 mm/day. There is a different length of growth phase in different arease of the body. (Scalp hair has longer growth phase than eyebrow hair)
What occurs during the transitional phase or catagen phase?: Growth stops and the hair remains in the follicle (short period of time).
What occurs during the resting phase or telogen phase?: During the telogen phase the hair shaft falls out. Normally there i always some hair falling our. Approximately 100/day.
Name the 3 types of glands in skin.: Eccrine sweat glands, apocrine sweat glands and sebaceous glands.
Describe the sebaceous glands. What are they associated with? What type of morphology do they have? What do they secrete? What is their mode of secretion? What pathology do they give rise to? How does this pathology occur?: Sebaceous glands are associated with hair follicles and are simple or branched alveolar. THey have a single duct that empties into the hair follicle about mid follicle. They secrete sebum, an oily substance. The mode of secretion is holocrine (whole cell). These are the glands that give rise to acne when infected by bacteria. Sex hormones at puberty increase secretion so they bulge and become more prone to infection.
What are sudiferous glands?: They are any sweat gland.
Describe eccrine sweat gland. Where are they located on the body? What type of morphology do they have? What type of secretion do they have? Where on the body do they commonly secrete? What mode of secretion do they have?: Eccrine sweat glands are the most common type of sweat gland and are located all over the body. Morphologically they are simple coiled tublular glands. Their type of secretion is merocrine and thier ducts open at the top of friction ridges in the hands and feet.
What 3 types of cells do eccrine sweat glands contain? What is the nature/function of each?: Clear cells are serous in nature.
Dark cells are mucous.
Myoepithelial cells help expel the secretions.
What are the major functions of eccrine sweat glands?: Temperature regulation by evaporation and excretion of ions (Na, PO) water, ammonia and urea.
Describe apocrine sweat glands. Whare are they located on the body? Describe their morphology in relation to eccrine sweat glands. What is their secretion mode/type? When do they start functioning? What pathology are they associated with?: Apocrine sweat glands are located in axilla, mons pubis and circumanal regions. The duct opens into the hair follicle above the sebaceous gland. Morphologically they are simple coiled tubular glands. They secrete a serous product via merocrine secretion. They don't start producing untill puberty. Bacteria invades these glands to give rise to armpit odor.
What are the 3 other types of glands in the skin that are modifications of sweat glands? Describe each.: Meibomian glands (tarsal glands) are modified sebacous glands which produce an oily substance and are located on the inner surface of eyelids.

Ceruminous glands are on the external auditory canal. They are modifate apocrine sweat glands that secrete a wax (cerumen).

Mammary glands are modified apocrine sweat glands.
What is the nail plate? What type of cells compose it? What does it replace in the epidermis?: The nail plate is the main body of the nail, it is composed of keratinocytes containing hard keratin. It replaces stratum corneum of the epidermis.
What is the lunula? What does it demarkate?: The lunula is characterized as the whitich crescent at root of nail. It marks the extent of the underlying nail matrix.
What is the lateral nail groove?: It is the lateral edges of the nail plate.
What is the nail root?: It is the proximal portion where the nail starts.
What is the nail bed? What is it composed of and continuous with?: The nail bed is the portion of the epidermis over which nail plate lies. It is composed of and continuous with the strata basale and spinosum of epidermis.
What is the nail matrix? What happens here?: The portion of the nail root where keratinocytes proliferate. Proliferation in this region shoves cells outward towards the free end of the nail.
What is the eponychium?: IT is the cuticle of the nail at the root (the flap of skin that grows over the nail).
What is the hyponychium?: The excess stratum corneum under the free edge of nail.
What is a receptor?: A transducer that changes an energy stimulus into an afferent nerve impulse that the brain can interpret. Each type of receptor is basically an afferent nerve ending with associated cells of surrounding tissue.
What are the three functional classifications of receptors? What do they respond to?: Mechanoreceptor - respond to displacement by touch, pressure or stretch
Thermoreceptor - respond to temperature changes.
Nociceptor - respond to pain, itch and injurious agents
What are the two morphological general classifictions? What are they called?: Morphologically simple - free nerve endings that end without associated structures.
Morphologically complex - encapsulated receptors that have associated cells (identified by structure)
What are the six types of morphological receptors?: Free nerve endings, Merkel cell ending, pacinian corpuscle, meissner's corpuscle, ruffini corpuscle, Krause capsule.
Describe free nerve endings. What types of sensation are they usually?: Free nerve endings lack schwann cells and myelin at their terminal end. They are naked nerve fibers lying between epidermal cells. They are thought to be thermoreceptors and nociceptors.
Describe Merkel cell endings. Where are they usually found? What stimumulus do they usually respond to?: Merkel cells are located between keratinocytes in stratum basale. There is an unmyelinated nerve fiber that forms a disc terminal on the cell. It is thought to be a mechanoreceptor for touch.
Describe pacinian corpuscles. What do they appear like? What do they usually detect? Where are they located.: Pacinian corpuscles are an encapsulated receptor that appears as an onion-like oval deep in lower dermis and hypodermis. They are very large and are mechanoreceptors for pressure and vibration.
What are Meissner's corpuscles? Where are they located. What to they usually detect?: Meissner's corpuscules are an ecapsulated receptor (flattened cells with horizontal nuclei surrounding it). They are located in dermal papillae of papillary layer (thick skin). They are mechanoreceptors for light touch.
What are Ruffini corpuscles? Where are they located? What do they look like? What do they detect?: A encapsulated receptor that are elongated and lie parallel to epidermal-dermal junction. Typically they are located deep in dermis or hypodermis. They are mechanoreceptors for tension of collagen fiber that run through surrounding capsules.
What are Krause capsules? What do they look like? Where are they found in the body?: Krause capsules ahve a delicate capsule where axon branches lie within the capsule like tree branches. THey are located in a layer of the conjunctiva of the eye, oral cavity mucosa, and tongue. They have an unknown function.

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