Term
| Largest/Heaviest organ in the body? |
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Definition
Skin, constituting approximately 16% of
total body mass and is 18 ft2 in size |
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Term
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Definition
| Epidermis (superficial) and dermis (deep); hypodermis is not considered part of the skin -- it's loose connective tissue |
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Term
| Characterisics of thick skin |
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Definition
-has an epidermis that is 400 – 600 μm thick
-prominent stratum corneum, robust stratum granulosum, and distinct stratum lucidum
-found on palms of hands & soles of feet
-lacks hair follicles, sebaceous glands, and arrector pili muscles |
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Term
| Characteristics of thin skin |
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Definition
-has an epidermis that is 75 – 150 μm thick
-less prominent stratum corneum, poorly developed to absent stratum granulosum, no obvious stratum lucidum
-covers most of the body surface
-contains hair follicles, sebaceous glands, and arrector pili muscles |
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Term
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Definition
- Serves as physical, chemical, and biological barrier
- provides immunological info
- maintains homestasis
- conveys sensory info to CNS
- synthesizes Vitamin D (endocrine)
- excretion via sweat, sebum, and apocrine glands |
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Term
| Which embryonic tissue layer is epidermis derived from? |
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Definition
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Term
| What type of epithelium is epidermis? |
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Definition
| Stratified squamous keratinized epithelium |
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Term
| How often is epidermis replaced? |
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Definition
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Term
| Why do we have fingerprints? |
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Definition
| Epidermal ridges that are formed by dermal papillae of the dermis |
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Term
| Predominant cell type of epidermis? |
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Definition
| Keratinocytes (90% of epidermal cells) |
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Term
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Definition
From deep to superficial:
1) Stratum basale (germinativum)
2) Stratum spinosum
3) Stratum granulosum
4) Stratum lucidum
5) Stratum corneum |
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Term
| Most mitotically active layer of epidermis? |
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Definition
| Stratum basale (germinativum) |
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Term
| Type of epithelium in stratum basale (germinativum) |
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Definition
| Single layer of cuboidal cells resting upon a basal lamina |
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Term
| Types of cells found in stratum basale (germinativum)? |
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Definition
- Keratinocytes
- Melanocytes
- Merkel's cells |
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Term
| Layer of epidermis containing stem cells? |
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Definition
| Stratum basale (germinativum); stem cells differentiate into new keratinocytes |
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Term
| Another name for stratum spinosum? |
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Definition
| Spinous or prickle cell layer, due to "prickly" appearance of intercellular junctions |
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Term
| How does the appearance of epithelial cells in stratum spinosum change as they move toward the surface? |
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Definition
| Cytoplasmic volume increases, and they become more flattened |
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Term
| Most superficial epidermal layer in which cells are nucleated? |
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Definition
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Term
| Thickness of stratum spinosum? |
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Definition
| Several cell layers thick |
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Term
| Thickness of stratum granulosum? |
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Definition
| Varies -- from one to a few cell layers |
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Term
| Proteins found in stratum granulosum? |
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Definition
| Keratohyalin (granules) and keratin (filaments) |
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Term
| Location of stratum lucidum? |
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Definition
| Between stratum granulosum and stratum spinosum of epidermis in THICK SKIN only |
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Term
| Metabolite of keratohyalin? |
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Definition
| Eleidin, which is found in the stratum lucidum |
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Term
| Most superficial layer of epidermis? |
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Definition
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Term
| Thickness of stratum corneum? |
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Definition
| 15-20 layers in thick skin, less in thin skin |
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Term
| Process by which filamentous keratin structures are shed? |
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Definition
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Term
|
Definition
- Keratinocytes
- Melanocytes
- Langerhan's cells
- Merkel's cells |
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Term
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Definition
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Term
| Characteristics of stratum basale (germinativum) keratinocytes? |
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Definition
- Basophilic due to free ribosomes
- long axis is perpendicular to stratum basale (germinativum)
- large amount of tonofilaments (keratin filaments) |
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Term
| Characteristics of stratum spinosum keratinocytes? |
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Definition
- large number of tonofilaments makes cytoplasm eosinophilic
- cells are cuboidal to polgondal with centrally located nucleus
- keratohyalin granule and Lamellar body (membrane coating granules) synthesis begins in upper stratum spinosum |
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Term
| Characteristics of stratum granulosum keratinocytes? |
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Definition
- can see basophilic granular cytoplasm featuring non-membrane-bound keratohyalin granules
- cells are flattened, polygonal, and 3-5 layers thick
- lots of lamellar granules, which contain glycolipids that are extruded by exocytosis into the intercellular space |
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Term
| Characteristics of stratum lucidum keratinocytes? |
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Definition
- weakly eosinophilic
- few, extremely flat cell layers
- lots of densely-packed filaments embedded in electron-dense matrix |
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Term
| Characteristics of stratum corneum keratinocytes? |
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Definition
- eosinophilic due to large amounts of keratin
- 15-20 layers of very flat cells, no nucleus
- keratinization takes 2-6 hours |
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Term
| How do melanocytes stain? |
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Definition
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Term
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Definition
| Neural crest, epithelial in origin |
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Term
| Where are melanocytes found? |
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Definition
| Stratum basale (germinativum) of epidermis |
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Term
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Definition
| A UV-sensitive enzyme involved in melanin synthesis |
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Term
| Does the number of melanocytes differ from race to race? |
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Definition
| NO; ratio of melanocytes:keratinocytes is from 1:4 to 1:10 in ALL RACES; difference in skin color is due to varying rates of melanin degradation |
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Term
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Definition
Eumelanin - brownish-black pigment
Pheomelanin - reddish-yellow pigment |
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Term
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Definition
1) A vesicle is surrounded by a membrane (premelanosome), and tyrosinase activity begins.
2) Vesicle becomes ovoid, shows cross-striations of melanin deposit, and is now called a melanosome.
3) Increased melanin structure obscures striations
4) Mature melanin granule migrates into cytoplasmic extension of melanocyte and is "injected" into keratinocytes via cytocrine secretion. |
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Term
| What is cytocrine secretion? |
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Definition
Transfer of mature melanin granules to keratinocytes
- exocytosis with concomitant endocytosis
- very little cytoplasm transfer occurs |
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Term
| Role of Langerhan's cells? |
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Definition
| Immune response (delayed hypersensitivity reactions) |
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Term
| Location of Langerhan's cells? |
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Definition
| Stratum spinosum of epidermis |
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Term
| Origin of Langerhan's cells? |
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Definition
| Bone marrow -- Langerhan's cells are NOT epithelial in origin, and as such, they do not feature desmosomal connection |
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Term
| Another name for Langerhan's cells? |
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Definition
| Dendritic cells, due to their long processes |
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Term
| Component in Langerhan's cells responsible for immune response? |
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Definition
| Birbeck granules -- paddle-shaped granules involved in T-lymphocytes activation |
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Term
| Function of Merkel's cells? |
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Definition
| Perception and locale endocrine control |
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Term
| Location of Merkel's cells? |
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Definition
| Stratum basale (germinativum), near areas of well-vascularized, richly-innervated connective tissue |
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Term
| Where on the body are Merkel's cells concentrated? |
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Definition
| Fingertips (requires acute sensory perception) |
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Term
| Origin of Merkel's cells? |
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Definition
| Epithelial (contains desmosomes and tonofilaments) |
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Term
| What is a Merkel's corpuscle? |
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Definition
| A Merkel cell + the neuron that receives its afferent sensory information |
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Term
| Another name for the dermis? |
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Definition
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Term
| Embryological origin of dermis? |
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Definition
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Term
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Definition
Papillary layer (superficial)
Reticular layer (deep)
-- no obvious demarcation between the two |
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Term
| What interdigitates with the stratum basale of the epidermis? |
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Definition
| Dermal papillae, formed from the papillary layer of the dermis |
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Term
| Which is the thicker layer of the dermis? |
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Definition
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Term
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Definition
| Bundles of Type I collagen fibers and thick elastic fibers, oriented into regular lines of tension |
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Term
| Where are glands and hair follicles found? |
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Definition
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Term
| What are Krause's end-bulbs? |
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Definition
| Cold and pressure receptors found in the reticular dermis |
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Term
| What causes "puckering" of areolae, penis, scrotum, etc? |
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Definition
| Contraction of smooth muscle in deepest portions of reticular dermis |
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Term
| Types of nerve endings in skin? |
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Definition
Free - lack connective tissue or Schwann cell investment; relay info about fine touch, heat, and cold; surrounds most hair follicles and attach to outer root sheath; have representation in cerebral cortex
Encapsulated - enclosed in connective tissue capsule; include Pacinian, Meissner, and Ruffini corpuscles |
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Term
| What kind of nerve ending do cat whiskers rely on? |
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Definition
| Free nerve endings; whiskers used for mechanoreception |
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Term
| Where do free nerve endings terminate? |
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Definition
| Stratum granulosum of epidermis |
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Term
| Where are Pacinian corpuscles found? |
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Definition
| The deeper areas of the reticular dermis (especially in the fingertips); in connective tissue associated with joints, periosteum, and internal organs |
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Term
| What do Pacinian corpuscles look like? |
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Definition
| Concentric layers of an onion; these things are BIG (can be larger than 1 mm) |
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Term
| Where are Meissner's corpuscles located? |
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Definition
| The papillary dermis in hairless skin |
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Term
| What makes up a Pacinian corpuscle? |
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Definition
| A MYELINATED nerve ending surrounded by a capsule |
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Term
| What makes up a Meissner's corpuscle? |
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Definition
| 1 or 2 UNmyelinated nerve endings of myelinated fibers, following spiral paths within a capsule |
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Term
| What does a Meissner's corpuscle look like? |
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Definition
| Tapered cylinders with spiraling nerve fibers and a sustentacular component of flattened Schwann cells forming irregular lamellae |
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Term
| What do Meissner's corpuscles do? |
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Definition
| Convey touch reception, particularly low frequency vibratory stimuli |
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Term
| Where are Ruffini's corpuscles located? |
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Definition
| The reticular dermis, hypodermis, and connective tissue of mesenteries and joints; especially abundant in digits and breasts |
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Term
| What makes up a Ruffini's corpuscle? |
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Definition
| 1 or 2 BRANCHED terminals of UNmyelinated endings of myelinated fibers that spiral within the capsule |
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Term
| What are epidermal skin appendages? |
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Definition
Structures derived from downgrowths of epidermal epithelium during development. Include:
Hair follicles and hair
Sebaceous glands
Sweat glands |
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Term
| What forms the pilosebaceous apparatus? |
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Definition
| The hair follicle and its associated sebaceous and apocrine sweat glands |
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Term
| Where are hair follicles absent? |
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Definition
Sides and palmar surfaces of hands and feet
Lips
Region around urogenital orifices |
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Term
| T/F: Men have more hair follicles than women. |
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Definition
| False. Men and women have approx the same number of hair follicles, but distribution differs. |
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Term
| Segments of hair follicles? |
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Definition
3 segments:
1) Infundibulum
2)Isthmus
3)Inferior Segment |
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Term
| What is included in the infundibulum of the hair follicle? |
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Definition
| The area between the surface opening of the follicle to the opening of the sebaceous gland; it's part of the pilosebaceous canal |
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Term
| What is the pilosebaceous canal? |
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Definition
| The route for the discharge of sebum; infundibulum of hair follicle is part of this |
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Term
| What is included in the isthmus of the hair follicle? |
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Definition
| The area between the infundibulum to the level of insertion of the arrector pili muscle |
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Term
| What is the arrector pili muscle? |
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Definition
| A smooth muscle that attaches at an oblique angle to the dermal sheath surrounding the hair follicle and elevating the hair to trap warm air close to the body; inserts into the papillary layer of the dermis |
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Term
| What makes up the dermal papilla of the hair follicle? |
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Definition
| Highly vascularized loose connective tissue; found at the base of the inferior segment of the hair follicle |
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Term
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Definition
| The germinative layer of the hair follicle, accounting for hair growth. Differentiate into keratin-producing cells of the hair and the internal root sheath. |
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Term
| What are the layers of the internal root sheath of the inferior segment of the hair follicle? |
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Definition
Internal to external:
1) Cuticle - squamous cells facing the hair shaft
2) Huxley's layer - middle plate
3) Henle's layer - also called external root sheath |
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Term
| What are the layers in hair? |
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Definition
Inner to Outer
1) medulla - only in thick hairs
2) cortex - contains cuboidal cells
3) cuticle - contains squamous cells; contiguous with the cuticle of the internal root sheat |
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Term
| What types of glands are associated with hair follicles? |
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Definition
| Sebaceous glands and apocrine sweat glands |
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Term
| What is the structure of sebaceous glands? |
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Definition
| Branched acinar glands with a short ductal portion; usually exist as several glands associated with a single hair follicle |
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Term
| Where are sebaceous glands located? |
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Definition
| In the dermis all over the body except palms and soles; abundant on face, forehead, and scalp |
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Term
| What secretory method do sebaceous glands use? |
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Definition
| Holocrine secretion - daughter cells synthesize lipid-rich product into cytoplasm, and then release the entire cytoplasm into pilosebaceous canal |
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Term
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Definition
Lipid-rich secretory product that coats hair follicles and surface of skin. Functions:
Bacteriostatic
Emollient
Barrier
Phermonal |
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Term
| What is the function of sweat? |
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Definition
| Regulation of body temperature, rids body of waste by secretion of hypotonic water solution with salts |
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Term
|
Definition
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Term
| Where are eccrine sweat glands found? |
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Definition
| Entire surface of body except lips and external genitalia; embedded in reticular dermis |
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Term
| What is the structure of an eccrine sweat gland? |
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Definition
| Coiled, simple tubular glands consisting of a secretory unit and duct |
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Term
| What are the cell types in the secretory unit of eccrine sweat glands? |
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Definition
1) dark cells - line lumen, secrete mucous
2) clear cells - beneath dark cells; contain intercellular canaliculi that extend to lumen; secrete watery product
3) Myoepithelial cells - form incomplete layer between clear cells and basal lamina |
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Term
| What epithelial cells form the duct of eccrine sweat glands? |
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Definition
| Stratified cuboidal epithelial cells |
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Term
| What is the function of the duct of eccrine sweat glands? |
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Definition
| To modify the secretory product by absorbing electrolytes and excreting ions, urea, lactic acid, etc. |
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Term
| Where are apocrine sweat glands located? |
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Definition
| Hair follicles, and especially in axilla, areola, perianal region, and cerumious (wax) glands of external auditory canal; secretory unit located in reticular dermis or hypodermis |
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Term
| When does apocrine sweat gland function begin? |
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Definition
| Puberty - glands are responsive to hormonal influences, emotion (not hyperthermia) |
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Term
| What is the method of secretion employed by apocrine sweat glands? |
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Definition
| MEROCRINE (not apocrine) - no loss of cytoplasm associated with secretion |
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Term
| What is continuous with the nail bed? |
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Definition
| Stratum basale (germinativum) and stratum spinosum of epidermis |
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Term
| What folds of skin are associated with the nail? |
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Definition
| Eponychium (cuticle) at the proximal end, hyponychium at distal end. Both are continuous with stratum corneum |
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Term
| What is the mitotically active region of the nail called? |
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Definition
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Term
| Description of Addison's disease? |
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Definition
| Overproduction of ACTH increases pigmentation of the skin; JFK was most famous |
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Term
|
Definition
| Inability of melanocytes to synthesize melanin; lack of pigmentation in skin leads to increased exposure to solar radiation |
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Term
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Definition
| Degeneration and disappearance of entire melanocytes results in spotty pigmentation (Michael Jackson) |
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Term
| Description of cutis laxa? |
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Definition
| Skin hangs in loose folds due to loss of elasticity caused by defective collagen-fibril processing |
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Term
| Description of Ehler-Danlos? |
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Definition
| Increase in ligament extensibility, bending of joints caused by defective collagen-fibril processing |
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Term
| Description of epidermolysis bullosa? |
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Definition
| Blistering of skin in response to minor injury caused by defect of intermediate filaments anchoring epidermis to papillary dermis |
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Term
| Types of epidermolysis bullosa? |
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Definition
Epidermolysis bullosa simplex - intercellular separation of basal epidermal cells with no scarring
Junctional epidermolysis bullosa - separation within basal lamina, results in scarring
Distrophic epidermolysis bullosa - most serious, results in separation in the upper dermis and scarring |
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Term
|
Definition
| Also called verrucae; common skin lesions following viral infection |
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Term
| Most common types of skin cancers? |
|
Definition
Basal cell carcinoma - arise from keratinocytes in stratum basale
Squamous cell carcinoma - arise from keratinocytes in stratum spinosum |
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Term
| Description of malignant melanoma? |
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Definition
| Serious form of cancer originating from melanocytes in stratum basale (3% of all cancers) |
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Term
| Description of psoriasis? |
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Definition
| Decrease in regeneration time of keratinocytes and increased number of mitotic cells in stratum basale and spinosum results in patchy thickening of skin; managed with corticosteroids/antimitotic drugs |
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Term
| Description of dermographism? |
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Definition
| Uncommon benign skin disorder with blistering due to non-injurious stimuli; release of histamine occurs upon stimulation, so antihistamine therapy is effective |
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