Term
| What comprises the integument system? |
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Definition
| -the skin and all of its derivatives (including hair, nails, claws, feathers, horns, antlers, combs, wattles, sweat glands, mammary glands, and hooves) |
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Term
| What are the main functions of skin? |
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Definition
-protection: against desiccation, noxiuous agents (UV light, microorganisms), mechanical trauma
-thermoregulation
-sensory receptors to inform animal about is environment |
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Term
| What are the three layers of the skin? Describe the histologically. |
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Definition
1)Epidermis: stratified squamous epithelium
2)Dermis (aka corium): loos CT or dense irregular CT
3)Hypodermis (aka subcutis): loos CT that binds skin to deeper structures (like perichondrium, periosteum, or fascia) |
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Term
| Definition: Panniculus adipossu |
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Definition
-concentrations of adipose tissue found in the hypodermis
-often found in regions that receive mechanical trauma like the carnivore's digital pad |
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Term
| True or False: The epidermis is never replenished by cell division and/or cell differentiation. |
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Definition
FALSE, constantly replenished
-deepest layer has stem cells that move outward as they mature (2-4 wks) |
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Term
| Name and describe the 5 layers of the epidermis |
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Definition
1)Stratum basale (basal layer): deepest, on the basal lamina, cuboidal/low cuboidal cells
2)Stratum spinosum (spinous layer): cells joined together by desmosomes, cells look spin, cells are superficially squamous
3)Stratum granulosum (granular layer): cells are flattened and contain basophilic keratohyalin aggregates
4)Stratum lucidum: ONLY IN VERY THICK EPIDERMAL REGIONS; poorly stained cells
5) Stratum corneum: anucleate, keratinized cells (squames) |
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Term
| What is the function of the desmosomes found in the stratum spinosum of the epidermis? |
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Definition
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Term
| How does the stratum spinosum of the epidermis differ in regions of the body? |
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Definition
-thick in hairless regions
-thin in regions with hair |
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Term
| What gives the stratum granulosum of the epidermis its bluish look? |
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Definition
| -basophilic keratohyalin aggregates (complex of te protein filaggrin) |
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Term
| What is the function of the cells of the stratum granulosum of the epidermis? |
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Definition
| -secrete a glycolipid that seals the space b/n the cells, preventing the passage of water |
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Term
| Outline the mechanism by which the epidermis keratinizes. |
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Definition
| keratohyalin aggregates dispers to liberate filaggrin=> filaggrin aggregates the keratin-containing intermediate filaments=> which are then covalently cross-linked into stable bundles=> cells die and nucleus degenerates=> dead cells slough off from the surface |
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Term
| What are the 4 types of cells in the epidermis? What layer ar they found in and what do they do? |
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Definition
1)Keratinocytes: about 95% of cells in epidermis; cells that differentiate into squames
2)Melanocytes: neural crest derivatives; found in stratum basale; do not keratinize; clear cells with dark-staining nuclei; synthesize melanin and pass it to keratinocytes
3)Langerhans cells: dendritic cells in the stratum spinosusm, derived from bone marrow precursors and function as antigen-presenting cells
4)Merkel cells: in stratum basale of hairless skin; associated with a nerve fiber, touch receptor |
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Term
| What comprises the dermis? |
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Definition
-collagen fibers: makes it resistant to shear and tearing
-elastic fibers
-basal portions of eccrine sweat glands, apocrine glands, hari follicles, and sebaceous glands |
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Term
| What are the two zones of the dermis? |
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Definition
1)Papillary zone: loose CT
2)(deeper)Reticular zone: dense irregular CT |
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Term
| Describe the interdigitating projections of the epidermis/dermis. |
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Definition
-Dermal papillae: project upward
-Epidermal pegs: project downward
-Epidermal ridges (rete ridges): same as pegs |
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Term
| What are the 3 types of glands in the skin? Which is the most common? |
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Definition
1)Epitrichial/apocrine sweat glands: MOST COMMON
2) Atrichial (merocrine or eccrine) seat glands
3)Sebaceous glands |
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Term
| Describe Epitrichial (apocrine) sweat glands |
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Definition
-simple tubular, coiled gland
-duct opens into the hair follicle just below epidermal surface
-located throughout skin |
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Term
| Describe Atrichial (merocrine or eccrine) sweat glands |
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Definition
-simple coiled tubular glands, open directly onto surface of the skin, not into follicle
-have a restricted distribution: footpads of the dog and cat, hairless skin in pig and ruminants |
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Term
| Describe Sebaceous glands |
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Definition
-simple branched acinar glands, open into hair follicles
-cells degenerate and material is secreted through duct of gland
-secretes Sebum: pdt rich in lipids; helps prevent entry of microorganisms into the skin |
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Term
| Describe the general structural features of hair (5) |
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Definition
-Hair shaft: the part of the hair above the surface of the skin
-Hair root: the part of the hair below the surface
-Bulb: an enlarged hollow portion at the base of the root
-Hair papilla: projection of dermis into center of the bulb
-Follicle: the indentation in the skin within which the root lies |
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Term
| What are the 3 layers of hair? |
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Definition
1)Cuticle: outermost layer, single layer of flattened keratinized cells, difficult to see b/c it is thin and transperant
2)Cortex: thickest intermediate layer, several layers of keratinized cells containing hard keratin, if hair is colored then will have pigment, cells held together by desmosomes
3)Medulla: central core, loose cuboidal cells, not always present |
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Term
Definition: Arrector pili m
-how is it innervated |
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Definition
-the bundle of smooth muscle cells that runs from CT sheath of hair follicle to papillary zone of the skin
-autonomic NS: makes hair stand up |
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Term
| What are the 2 types of hair follicles according to diameter? |
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Definition
1)Primary follicle: large diameter, goes deep into dermic, has sebaceous gland, sweat gland, and arrector muscle (hair= primary/overcoat/guard hair)
2)Secondary follicle: smaller in diameter, root too close to surface, lacks sweat glands/arrector m (hair= secondary/underhair) |
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Term
| What are the 2 types of follicles according to organization? |
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Definition
1)Simple follicle: follicles with a single hair emerging
2)Compound follicle: cluster of several follicles whose hairs emerge from a single opening, usually have one primary and seceral secondary follicles |
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Term
| Definition: Sinus follicles |
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Definition
-specialized follicles that produce sensory hairs (tactile hairs, sinus haris)
-specialized for touch sensations and are found on the face region
-larger, single follicles that have a blood-filled sinus in the CT sheath surrounding the follicle
-skeletal mm attached to follicle
-some voluntary control of movement of these hairs |
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Term
| What are the components of the Integumentary System? |
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Definition
| -skin, hair, nails, claws, feathers, horns, antlers, combs, wattles, sweat glands, mammary glands, and hooves |
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Term
| What are the functions of the integumentary system? |
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Definition
-protection against desiccation, UV light and microorganisms, mechanical trauma
-thermoregulation: blood flow regulation, sweating, hair and fur
-Sensory organ: touch and temperature
-mechanical support |
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Term
| ______ is the largest organ in the body. |
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Definition
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Term
| Where are the thicker regions of the skin? Thinner? |
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Definition
-Thicker: exposed to abrasion; footpads, hairless part of the nose in some species (palms and soles in people)
-Thinner: on ventral body surface than dorsal body surface (also thinner on medial than lateral surfaces) |
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Term
| What are the two layers of the skin? Describe the epi. |
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Definition
-Epidermis: outermost layer with stratified squamous epi
-Dermis (column): beneath the epidermis, loose or dense irregular CT |
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Term
| What layer is below the dermis? Describe it. Function? |
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Definition
-Hypodermis or subcutis
-composed of collagenous CT and adipose tissue
-binds skin to underlying structures (perichondrium, periosteum, or faascia) |
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Term
| What is the function of adipose tissue? |
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Definition
| -mechanical protection, thermal insulation and E storage |
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Term
| Describe the epi of the Epidermis. Is it regenerated? |
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Definition
-keratinized stratified squamous epi
-constantly replenished by cell division (shed from surface), cells undergo orderly proliferation, differentiation and keratinization): 2-4 wks to progress from basal layer to shedding, keratinized layer, four distinguishable layers are typically seen |
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Term
| What are the 5 layers of the Epidermis? Do they contain living or apoptotic cells? |
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Definition
-Stratum basale: basal layer, living cells
-Stratum spinosum: spinous layer, living cells
-Stratum granulosum: granular layer, living cells
-Stratum lucidum: (only present in very thick epidermis like footpad) apoptotic cells
-Stratum corneum: keratinized stratified squamous epi, apoptotic cells |
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Term
| Describe the contents/structural components of the Stratum Basale of the Epidermis |
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Definition
-basal layer
-single layer of columnar or cuboidal cells on basal lamina
-stem cells that make cells of overlying layers |
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Term
| What specialized structural connections in the Stratum Basale of the Epidermis? |
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Definition
-Desmosomes: lateral surfaces of cells are attached to each other and cells are attached to overlying stratum spinosum
-Hemidesmosomes: attach cells to underlying basal lamina |
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Term
| Describe the cells of the Stratum Spinosum (spinous layer) of the Epidermis |
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Definition
-cells are irregularly polyhedral and several layers thich
-cells attached by desmosomes |
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Term
| Describe the contents of the cytoplasm of Stratum Spinosum of the Epidermis |
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Definition
| -cytoplasm contains intermediate filaments: cytokeratin (forms tonofibrils) + tonofibrils (affrefates of cytokeratin) + extend into desmosomes that link keratinocytes |
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Term
| What is the function of the Desmosome and Hemidesmosomes? |
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Definition
-give strength to epi by linking cytoskeletons of adjacent cells: strong attachment b/n adjacent cells (link intermediate filaments)
-Desmosomes aka macula adherens
-Hemidesmosomes bind base of cell to underlying basement membrane |
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Term
| What are the 3 components of Adhering Junctions? |
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Definition
-transmembrane proteins
-anchoring proteins (sytoplasmic side)
-cytoskeleton |
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Term
| Describe the cells/contents of te Stratum Granulosum of the Epidermis |
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Definition
-cells are flattened and contain basophilic keratohyaline aggregates/granules (for maturation of cells)
-also contain lamellar granules/ membrane-coating granules that are emptied into intercellular space of stratum corneum (contain lipids and hydrolytic enzymes) |
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Term
| What is the function of the Keratohyaline Aggregates found in the Stratum Granulosum of the Epidermis? |
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Definition
| -contain profilaggrin and other proteins that combine with tonofibrils to produce keratin |
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Term
| What is the function of the Lamellar Granules/membrane-coating granules found in the Stratum Granulosum of the Epidermis? |
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Definition
| -contain lipids and hydrolytic enzymes that coat the skin and make it resistant to water |
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Term
| Definition: Keratinization |
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Definition
| -the process by which epidermal cells differentiate |
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Term
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Definition
-as keratinocytes differentiate, large amounts of tonofibrils, keratohyaline granules and lamellar granules are formed in the cytoplasm
-tonofibrils and keratohyalin forms a meshwork
-lamellar granules discharge contents b/n cells
-nuclei and organelles disintegrate
-cells are filled with bundled formed of tonofibrils and keratoyaline
-produces stratum corneum |
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Term
| The cells of the stratum corneum are surrounded by ________ |
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Definition
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Term
| __________ + __________ = Keratin |
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Definition
-filaggrin (in keratohyaline granules)
-cytokeratin bundles (tonofibrils) |
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Term
| Describe the cells of the Stratum Corneum (keratinized layer) of the Epidermis |
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Definition
-composed of layers of anucleate, keratinized cells (squames)
-dead cells that are constantly being shed
-cells have no nuclei or cytoplasmic organells
-integrity of this layer helps prevent water loss through the epidermis: interfellular lipid from cells of granular cell layer helps compose the barrier) |
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Term
| Describe the Stratum Lucidem *clear layer( of the Epidermis |
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Definition
-NOT ONE OF THE 4 MAJOR EPIDERMAL LAYERS
-only found in exceptionally thick skin in hairless regions: footpads, planum nasale
-thin, translucent homogeneous line between stratum granulosum and stratum corneum |
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Term
| Describe the cells of the Stratum Lucidum of the Epidermis |
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Definition
-fully keratinized, closely compacted dense cells: no nuclei or cytoplasmic organells
-contain eleidin (keratin-like protein that stains differently) |
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Term
| What are the 4 most abundant cell types in the epidermis? Which is the most abundant? |
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Definition
-Keratinocytes: 85-90% of cells, start at stratum basale and eventually become squames
-Melanocytes
-Langerhans cells
-Merkel cells |
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Term
| Where are Melanocytes found? Histologically and functionally describe them. |
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Definition
-L: in the Stratum Basale of the Epidermis (derived from neural crest ectoderm)
-do not keratinize
-H: clear cells with small, dark-staining nuclei and dendritic processes, melanosomes may be visible in the cytoplasm
-F: synth melanin granules and pass them to keratinocytes |
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Term
| What is the function of Langerhans cells? Where specifically are they found? |
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Definition
-F: dendritic cells, antigen-presenting cells
-L: Stratum Spinosum of the Epidermis |
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Term
| What type of cells are Langerhans cells derived from? |
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Definition
-monocyte-macrophage
-in bone marrow |
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Term
| Where are Merkel Cells found specifically? What is their function? |
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Definition
-L: Stratum Basale of hairless skin
-F: touch receptors associated with nerve fibers (tactile corpuscles) |
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Term
| What are the two zones of the Dermis? |
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Definition
-Papillary dermis: superficial and narrow zone immediately beneath the epidermis
-Reticular dermis: deeper and thicker layer beneath the papillary dermis |
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Term
| Describe the location and contents of the Papillary Dermis |
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Definition
-superficial and narrow zone beneath the epidermis
-less dense CT
-contains small blood vessels (papillary loops) and fine nerve twigs |
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Term
| Describe the location and contents of the Reticular Dermis |
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Definition
-deeper and thicker layer beneath the papillary dermis
-dense irregular CT
-contains blood vessels, nn, and adnexa or appendages of skin (also sweat glands etc) |
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Term
| What is the visually apparent specialization of the Papillary Dermis? |
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Definition
| -has papilla that interdigitate with the epidermis |
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Term
| What are the two types of interlocking projections of the epidermis and dermis? Describe them functionally and locationally |
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Definition
-Epidermal pegs: p(aka rete ridges) projections into underlying dermis, strengthen connection between epidermis and dermis to resist frintion
-Dermal papilla: project up toward epidermis between pegs, typically looser CT, help resist friction and strengthen dermo-epidermal junction |
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Term
| What is the Hypodermis/Subcutis? what is it composed of? What is its function? |
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Definition
-layer below dermis
-composed of collagenous CT, adipose tissue (anniculus adiposus), blood vessels that supply skin, hair follicles, sebaceous glans, and sweat glands
-binds skin to underlying structures (perichondrium, periosteum, or fascia) |
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Term
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Definition
| -appendages of the skin: hair follicles, sebaceous glands, sweat glands: apocrine/epitrichial and eccrine/atrichial |
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Term
| What are the two types of exocrine glands? |
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Definition
-Simple coiled tubular glands: Eccrine/merocrine/atrichial (not assoc with hair), apocrine/epitrichial sweat glands (assoc with hair)
-Simple branched acinar glands: sebaceous glands (assoc with hair) |
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Term
Structurally describe Apocrine/Epitrichial Sweat Glands.
-are they assoc with hair follicles?
-What do they do? |
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Definition
-simple coiled tubular glands
-assoc with hair follicles (duct opens into follicle near epidermal surface)
-pheromone or scent secretion in most species and makes sweat for cooling in horses |
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Term
| Give an example of apocrine glands |
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Definition
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Term
| Are Eccrine/Atrichial Sweat Glands assoc with hair follicles? Are they widespread in the body? |
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Definition
-not assoc with hair follicles: duct opens to epidermal surface
-limited distribution in animals: footpads in dogs and cats, nose in ruminant and pigs |
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Term
| Are Sebaceous Glands assoc with hair follicles? What do they secrete and why? |
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Definition
-open into hair follicles, simple branched acinar glands: may open onto skin surface in some locations
-secretory product is high in lipid (sebum) bia holocrine secretion
-secretion prevents drying of hair and skin, helps prevent entry of microorganisms into skin and follicles, has waterproofing qualities |
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Term
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Definition
| -a refined extract of sebum from sheep's wool |
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Term
| Describe light touch dermal innervation |
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Definition
| -meissner's corpuscles (right under epidermis): encapsulated sensory receptors, loc in dermal papillae |
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Term
| Describe pressure and coarse touch dermal innervation |
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Definition
| -Pacinian corpusles: encapsulated sensory receptor, deeper skin/ligaments/joint capsules/some viscera |
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Term
| What are the divisions of hair? |
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Definition
-Shaft: portion of hair above skin surface
-Root: portion of hair below skin surface
-Bulb: expansion at base of hair
-Papilla: core that extends up into hair bulb (contains blood vessels and nerve twigs)
-Follicle: tubular structure within which hair root lies: surrounded by CT sheath |
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Term
| Where in a strand of hair do blood vessels and nerve twigs lie? |
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Definition
| -hair papilla (core that extends up into hair bulb) |
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Term
| What are the 3 layers of hair? |
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Definition
-Cuticle: thin, outermost layer of overlapping keratin plates
-Cortex: thick layer that forms bulk of hair shaft (ker cells connected by desmosomes, may be pigmented by melanin)
-Medulla: core of hair shaft, loose cuboidal cells (not always present) |
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Term
| What special structure runs alongside hair follicles? How is it innervated? What is its function? |
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Definition
-Arrector pili m: smooth m that extends from CT sheath of follicle to papillary dermis
-sympathetic innervation
-contraction cuases hair shaft to move vertically |
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Term
| What are 3 instances in which the arrector pili mm would be stimulated? |
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Definition
-behavioral display/hackles raised
-inc insulation in cold weather
-inc discharge of sebaceous gland |
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Term
| What are the 2 types of hair follicles when differentiated by size? |
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Definition
-Primary: large diameter, deep in dermis; has sebaceous gland, sweat gland, and arrector m, called "primary hair/guard hair"
-Secondary follicle: smaller in diameter, shallow in dermis, lacks sweat glands and arrector m, called "secondary hairs/underhairs" that lack a medulla |
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Term
| What are the 2 types of hair follicles when categorized by organization? |
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Definition
-Simple follicle: single hair emerging from follicle
-Compound follicle: cluster of several follicles with hairs emerging from one opening, usually one primary and several secondary follicles |
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Term
| Definition: Stiff sensory/tactile hairs |
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Definition
-vibrissai or whiskers in sinus hair follicles
-located in face region
-large, single follicles with blood-filled sinus in CT sheath surrounded follicle: skeletal mm attach to follicle (voluntary movement) and free nerve endings and Merkel cells in hair follicle |
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Term
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Definition
-specialized structures continuous with epidermis and dermis of skin
-wall of hard keratin is analogous with stratum corneum of epidermis
-dermis is dense irregular CT over dorsal surface of distal phalanx (rich in blood vessels) |
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Term
| Describe Avian Integument |
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Definition
-thinner than mammalian skin: stratum basale, stratum spinosum, stratum corneum
-aglandular except for uropygial (preen) gland |
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Term
| Definition: Uropygial/preen gland |
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Definition
-specialized sebaceous gland in avians
-well-developed in aquatic species
-located dorsally at the base of the tail: opens to skin surface thru papilla |
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