Term
| What is the heaviest organ in the body? What percentage of its body weight does it comprise? |
|
Definition
|
|
Term
| What two layers is skin divided into? |
|
Definition
|
|
Term
| Which body surfaces does thick skin cover? |
|
Definition
| Body surfaces subject to wear and tear (soles of feet, palms of hands) |
|
|
Term
| Which body surfaces does thin skin cover? |
|
Definition
| Areas not subject to abrasion (eyelids, abdomen) |
|
|
Term
| What type of epithelium is Epidermis made of? |
|
Definition
| Stratefied squamous keratinized epithelium. |
|
|
Term
| What is the embryologic origin of Epidermis? |
|
Definition
|
|
Term
| What is the most common cell type of Epidermis? |
|
Definition
|
|
Term
| Keratinocytes are constantly being made at the _________ and shed at the ________. |
|
Definition
|
|
Term
| What is the dermis made of? |
|
Definition
|
|
Term
| What is the embryologic origin of dermis? |
|
Definition
|
|
Term
| What two layers is Dermis split up into? |
|
Definition
| Papillary and reticular layers. |
|
|
Term
| What is the Hypodermis (Subdermis)? |
|
Definition
| A layer of loose CT deep to the dermis. Although it is connected to the dermis, it is NOT part of the skin. |
|
|
Term
| What are the skin appendages? |
|
Definition
| Glands, hair follicles and nails. |
|
|
Term
| How many layers does the Epidermis have? |
|
Definition
|
|
Term
| What is the Stratum (Germinativum) Basale? |
|
Definition
| Part of the Epidermis. A single layer of basophilic cuboidal to columnar keratinocytes with elongated nuclei. |
|
|
Term
| What anchors the basal cell membranes of keratinocytes to the basal lamina? |
|
Definition
|
|
Term
| What joins the plasma membranes of adjacent keratinocytes? |
|
Definition
|
|
Term
|
Definition
| 10nm filaments made of the protein keratin. These are abundant in the keratinocytes of the Stratum Basale. |
|
|
Term
| What and where are keratinocytes derived from? |
|
Definition
| Stem cells in the bulge of hair follicles and the ridge of papillary dermis. |
|
|
Term
| How often is the entire epidermis renewed by the division of stem cells? |
|
Definition
|
|
Term
| What is the Stratum Spinosum? |
|
Definition
| Part of the Epidermis. A layer of polygonal-shaped keratinocytes that is superficial to Stratum basale. |
|
|
Term
| Describe the keratinocytes of Stratum Spinosum. |
|
Definition
| Polygonal-shaped, with round central nuclei and melanin granules. |
|
|
Term
| Why is Stratum Spinosum referred to as the "prickle-cell layer"? |
|
Definition
| Spines radiate between cells. Keratin filaments form thick bundles called tonofibrils that converge and insert into desmosomes. These "spines" are so coarse they are visible by light microscopy. |
|
|
Term
| What is the level of mitotic activity in the keratinocytes of S. Spinosum? |
|
Definition
|
|
Term
| Stratum Basale + Stratum Spinosum = ? |
|
Definition
|
|
Term
| Which two strata of the Epidermis for the Malpighian layer? |
|
Definition
|
|
Term
| Where does Stratum Spinosum lie? |
|
Definition
| In the Epidermis, between Stratum Basale and Stratum Granulosum. |
|
|
Term
| Where does Stratum Basale lie? |
|
Definition
| The deepest layer of the Epidermis, between the Papillary layer of the dermis and the Stratum Spinosum of the Epidermis. |
|
|
Term
| Where does Stratum Granulosum lie? |
|
Definition
| In the epidermis, superficial to Stratum Spinosum and deep to Stratum Lucidum |
|
|
Term
| What is Stratum Granulosum? |
|
Definition
| A layer of the Epidermis formed of 3-5 layers of flattened keratinocytes |
|
|
Term
| What do keratinocytes of Stratum Granulosum contain? |
|
Definition
| Keratohyalin granules and lamellar granules. |
|
|
Term
| What are keratohyalin granules? |
|
Definition
| Coarse basophilic densities found in the keratinocytes of Stratum Granulosum. They are non-membrane bound complexes of tonofibrils and amorphous proteins that are rich in phosphorylated histidine and cystine. Visible by LM. |
|
|
Term
| What are lamellar granules? |
|
Definition
| Found in keratinocytes of Stratum Granulosum. They are membrane-bound, ovoid structures containing stacked discs of glycolipid bilayers. Visible by TEM. |
|
|
Term
| How is the skin "sealed", forming a barrier to foreign materials? |
|
Definition
| Lamellar granules fuse with cell membrane and discharge their contents into the extracellular space and forming sheets of lipid. |
|
|
Term
| Where does the Stratum Lucidum lie? |
|
Definition
| In the epidermis, superficial to Stratum Granulosum, deep to Stratum Corneum. |
|
|
Term
|
Definition
| A layer of the Epidermis made of dead, flat, translucent and acidophilic keratinocytes. |
|
|
Term
| Describe the keratinocytes of the Stratum Lucidum. |
|
Definition
| Dead, flat, translucent and acidophilic, with disintegrated nuclei and organelles. |
|
|
Term
| What are the keratinocytes of Stratum Lucidum filled with? |
|
Definition
| Bundles of keratohyaline bundles. |
|
|
Term
| Where would one find Stratum Lucidum? |
|
Definition
|
|
Term
| Where does the Stratum Corneum lie? |
|
Definition
| The most superficial layer of the Epidermis, lying superficial to Stratum Lucidum. |
|
|
Term
| Where is Stratum Corneum the thickest? |
|
Definition
|
|
Term
|
Definition
| The most superficial layer of epidermis, made of stacks of flattened, dessicated keratinocytes. |
|
|
Term
| What are the keratinocytes of Stratum Corneum filled with? |
|
Definition
| The hard scleroprotein, keratin. |
|
|
Term
| Are desmosomes and the extracellular glycolipid layer retained by the keratinocytes of Stratum Corneum? |
|
Definition
|
|
Term
| What happens to the superficial cells of Stratum Corneum? |
|
Definition
| Continuously shed by desquamation |
|
|
Term
|
Definition
| The process of basal keratinocytes converting into cornified cells. |
|
|
Term
| What are the keratinized cells of Stratum Corneum referred to as? |
|
Definition
|
|
Term
| What are the 5 steps of Keratinization? |
|
Definition
1. Accumulation/conversion of keratohyaline granules to amorphous scleroprotein: keratin.
2. Disintegration of nuclei and organelles
3. Secretion of and extracellular glycolipid layer to seal the cells
4. Retention of desmosomes
5. Dessication of keratin |
|
|
Term
|
Definition
| A specialized cell of neural crest origin. Round with long ctoplasmic processes that invaginate the plasma membrane of the keratinocytes of S. Basale and S. Spinosum. |
|
|
Term
| Where do melanocytes reside? |
|
Definition
| Amongst the keratinocytes of the Stratum Basale. |
|
|
Term
| What is the ratio of melanocytes to keratinocytes? What is this grouping called? |
|
Definition
| One melanocyte serves several keratinocytes. Called an Epidermal-melanin unit. |
|
|
Term
| Why are melanocytes difficult to positively identify? |
|
Definition
| Their cytoplasm does not stain with routine histologic dyes. |
|
|
Term
| How is melanin synthesized? |
|
Definition
| Tyrosinase stimulates melanocytes to synthesize melanin from tyrosine and package it into membrane-bound melanosomes. |
|
|
Term
| What happens after melanin is packages into melanosomes? |
|
Definition
| The melanosomes migrate to the melanocyte cytoplasmic processes where they are injected into the keratinocytes of both S. basale and S. spinosum. |
|
|
Term
| What is the purpose of injecting melanin into keratinocytes. |
|
Definition
| Melanin granules accumulate in a supranuclear region, providing solar protection and skin pigmentation. |
|
|
Term
| What happens to melanasomes in keratinocytes as they mature? |
|
Definition
| They fuse with lysosomes and are destroyed. |
|
|
Term
| Melanocyte numbers are constant within __________ but vary among __________. |
|
Definition
A given skin region.
Different skin regions. |
|
|
Term
| Do ethnicity and gender influence the number of melanocytes? |
|
Definition
|
|
Term
| What are the 5 main factors that cause differences in skin tones? |
|
Definition
1. Number of melanosomes
2. The type of melanin they contain
3. The rate of melanin breakdown
4. Carotene
5. Blood supply |
|
|
Term
| What are two types of human melanin? |
|
Definition
1. Eumelanin: brown to black
2. Pheomelanin: red to yellow |
|
|
Term
| What are Langerhans cells? What are they derived from and what is there function? |
|
Definition
| Dendritic cells of the Stratum Spinosum. Bone marrow derived APCs. They bind and process antigen, migrate to lymph nodes and present to T lymphocytes. |
|
|
Term
| Where are Merkel cells found? What do they contain and what is their function? |
|
Definition
| They are found in the S. Basale of digits, lips, and hair bulbs. They contain neurosecretory granules and are associated with specialized affterent nerve endings. |
|
|
Term
| What does a Merkel cell + its nerve ending = ? |
|
Definition
| Merkel's corpuscle, a mechanoreceptor. |
|
|
Term
| Where does the dermis lie? |
|
Definition
|
|
Term
| Where is the dermis the thickest? |
|
Definition
|
|
Term
| What is dermis comprised of? What does it contain? (5 things) |
|
Definition
Connective Tissue
1.Collagen (LOTS)
2.Elastic fibers
3. Reticular fibers
4. Fibroblasts
4. Dermatin sulfate (a GAG) |
|
|
Term
| What is the papillary layer of the dermis? |
|
Definition
| A layer of LOOSE CT adjacent to the epidermis. |
|
|
Term
| What is the CT of the papillary layer of the dermis comprised of? What resides in this layer? |
|
Definition
| Type I and Type III collagen fibers and elastic fibers. Fibroblasts, mast cells, and macrophages. |
|
|
Term
| What is the major function of the papillary layer of the dermis? |
|
Definition
| Supports nerve endings and blood vessels. |
|
|
Term
| What is the reticular layer of the dermis? What is it made up of? |
|
Definition
| The thick deep layer containing coarse bundles of Type I collagen and elastic fibers. |
|
|
Term
| What is the most common cell type of the reticular layer of the dermis? |
|
Definition
|
|
Term
| What are the functions of the reticular layer of the dermis? |
|
Definition
| Binds the dermis to the hypodermis, and supports large vessels, nerves, hair follicles and glands. |
|
|
Term
| What are the layers of the skin from superficial to deep? |
|
Definition
EPIDERMIS
1. S. Corneum
2. S. Lucidum
3. S. Granulosum
4. S. Spinosum
5. S. Basale
DERMIS
6. Papillary layer
7. Reticular layer
HYPODERMIS |
|
|
Term
| What causes the "undulating" interface at the dermal-epidermal junction? |
|
Definition
| Theinterdigitation of dermal papillae (upward conical projections of the dermal surface) with the epidermal ridges (downward projections of the base of epidermis) |
|
|
Term
| Where are interdigitations of the dermal-epidermal interface the most numerous and deepest? |
|
Definition
|
|
Term
| The basal lamina of skin has an electron lucent _________ and an electron dense _________. |
|
Definition
| Lamina rara, lamina densa |
|
|
Term
| Describe the two mechanisms by which the keratinocyte membranes are anchored. |
|
Definition
1. Actin--transmembrane integrins--laminins (of BL)--type IV collagen (via nidogens)
2. Anchoring complex: keratin microfilaments--hemidesmosomes (containing plectin, type XVIII collagen & integrin)--laminin 5 in BL--type VII collagen. Type VII entraps banded collagen fibers (I, III, V), fibrillins, and type VI of the Lamina reticularis--type IV collagen |
|
|
Term
| What is the hypodermis? What does it contain? |
|
Definition
| The subcutaneous tissue layer that binds the reticular dermis to subjacent organ and fascia. Can contain fat cells and house skin appendages. (SUPERFICIAL FASCIA) |
|
|
Term
|
Definition
| Elongated keratinized structures derived from epidermis. They house hairs, which grow discontinuously from the follicle. Terminates as a bulb and papilla. |
|
|
Term
| Where on the body is hair absent? |
|
Definition
| Palms,soles, lips, glans penis, glans clitoris, and labia minora. |
|
|
Term
| Hair color, size, and distribution are dependent on what three factors? |
|
Definition
| Ethnicity, gender, and region of body. |
|
|
Term
| What are arrector pili muscles? |
|
Definition
| Small bundles of smooth muscle that attach hair follicle to papillary dermis. Contraction causes hair to stand up. Sympathetic innervation. |
|
|
Term
| Where are sacculated sebaceous glands found? |
|
Definition
| Everywhere except the soles of feet and palms of hands. |
|
|
Term
| Where do sebaceous gland ducts open up into? |
|
Definition
| Mostly hair follicles. In hairless regions, ducts open directly onto skin. |
|
|
Term
| What happens to secretory cells of sebaceous glands as they migrate toward the duct and die? What type of secretion is this an example of? |
|
Definition
| They become part of the secretory product. Holocrine secretion. |
|
|
Term
| What is sebum? What does it contain? |
|
Definition
| The secretory product of sebaceous glands. Contains a mixture of lipids including waxes, triglycerides, cholesterol, etc. |
|
|
Term
| What are Eccrine (Merocrine) Sweat glands? |
|
Definition
| Simple tubular glands widely distributed in the dermis |
|
|
Term
| What are the two components of an Eccrine sweat gland? |
|
Definition
| Secretory unit and a sweat duct |
|
|
Term
| Where is the secretory unit of an Eccrine sweat gland found and what is it comprised of? |
|
Definition
| Embedded in the reticular dermis. Formed of clear, dark, and myoepithelial cells. |
|
|
Term
| Describe the Dark and Clear cells of the secretory unit of an eccrine sweat gland. |
|
Definition
Dark cells: line lumen, contain glycoprotein granules
Clear cells: have interdigitating membranes and produce ultrafiltrate of plasma |
|
|
Term
| Describe the sweat duct of an eccrine sweat gland. |
|
Definition
| Coiled and lined with stratefied cuboidal epithelium. Duct cells resorb sodium from sweat. |
|
|
Term
| What does sweat contain? What is its function? |
|
Definition
| Water, NaCl, urea, uric acid and ammonia. Cools the skin, excretes waste products. |
|
|
Term
| What innervates eccrine sweat glands? |
|
Definition
|
|
Term
| Where are apocrine sweat glands found? |
|
Definition
| Axilla, areola, perianal region |
|
|
Term
| How do Apocrine differ from Eccrine glands? |
|
Definition
| Apocrine glands are larger |
|
|
Term
| What do apocrine glands produce? |
|
Definition
| A viscous fluid that is initially odorless but becomes odorous when acted up by bacteria. |
|
|
Term
| What are apocrine glands innervated by? |
|
Definition
|
|
Term
| What secretion mechanism does Apocrine glands use for secretion? |
|
Definition
|
|
Term
|
Definition
| Extensions of the skin that lie on the nail bed. |
|
|
Term
|
Definition
| Cells in nail matrix divide and deliver cells to nail root. Keratinocytes differentiate and extend the nail plate, gliding over the nail bed. |
|
|
Term
| What layers of epidermis does the nail bed contain? Which layer is the nail equivalent to? |
|
Definition
| Stratum Basale and Stratum Spinosum. Nail is equivalent to Stratum Corneum. |
|
|
Term
| How many arterial layers does the skin have? Where are these layers? |
|
Definition
Two. Between:
Papillary dermis/Reticular dermis
Dermis/Hypodermis |
|
|
Term
| How many venous layers does the skin have? Where are these layers? |
|
Definition
Three. Between:
Papillary dermis/Reticular dermis
Dermis/Hypodermis
Within the reticular dermis |
|
|
Term
| Where within skin do capillary beds form? |
|
Definition
| Within the papillary dermis. |
|
|
Term
| How does the body conserve heat via blood supply in the skin? |
|
Definition
| Arteriovenous anastamoses that bypass capillary beds. |
|
|
Term
| Where are nerve endings that sense pain found in the skin? |
|
Definition
| Free nerve endings are found in the epidermis and around glands. |
|
|
Term
| Where are specialized nerve receptors found in the skin? |
|
Definition
| Dermis, hypodermis, especially around dermal papillae. |
|
|
Term
| What are the (7) functions of the skin? |
|
Definition
BOTSVIM
Barrier: S. Corneum + nails
Osmosis: Sweat glands
Temp: Sweat glands, hair, blood supply
Sensory: special sensory & free nerves
Vitamin D3 production: via UV
Immunity: Innate and adaptive
Microbial symbiosis |
|
|
Term
| How is Vitamin D3 made in the skin? |
|
Definition
| UV light converts 7-dehydrocalciferol in epidermis to cholecalciferol (precursor to vit D3) |
|
|
