4.05 Histology of skin Flashcards by Ace Alerta

Topmost layer of the epidermis comprised of non-nucleated cells entirely filled with keratin filaments in an amorphous matrix

stratum corneum

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Spaces in between the cells in the topmost layer of the skin are filled with what? What is its purpose?

Lipids; cement cells together

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Layer of the epidermis not present in thin skin

Stratum lucidum

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Layer of epidermis with 3-5 layers of flattened polygonal cells

Stratum granulosum

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Free, non-membrane granules found in the cells of stratum granulosum

Keratohyaline granules

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Layer of skin that provides the waterproof barrier; how does it do this?

Stratum granulosum; from exocytosis of lamellar granules that discharge their lipid content

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How many layers does the stratum granulosum have in thin skin?

One

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Thickest layer of the skin consisting of polyhedral cells with central nuclei and nucleoli

Stratum spinosum

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The stratum spinosum actively synthesizes what? Bundles of this are called __.

Keratin filaments

Tonofibrils

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What gives the s. spinosum its spiny appearance?

Tonofibrils on both sides of each desmosome

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Layer of the epidermis where there is intense mitotic activity to replenish keratinocytes

Stratum basale

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Layer of the epidermis where keratin filaments start to show

Stratum basale

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Layer of the skin usually associated with skin cancers

Stratum basale

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Cells that produce melanin; what particular organelle produces it? What enzyme synthesizes it?

Melanocyte; melanosome; tyrosinase

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The color of the skin depend on what (3)? Where do these come from?

carotene - fat cells in hypodermis
red tint - oxygenated hemoglobin
brown tint/melanin - melanocytes

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T/F. Dark-skinned people have more melanocytes than fair-skinned.

False. What differs between the two are the amount of pigment produced and the distribution

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Compare the distribution of melanosomes in caucasians and dark-skinned individuals.

The former have melanosomes found on the basal layer; the latter have them on the epidermis

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Process where melanocytes move closer to keratinocytes

Cytocrine secretion

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Antigen-presenting dendritic cell to T lymphocytes that are found in the stratum spinosum

Langerhans

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Rod-like granules with terminal expansion and cross-striations that are found in Langerhans cells

Birbeck granules

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Non-epithelial cell in the sensory complex with free nerve endings for light touch

Merkel cell

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These are pale-staining non-epithelial cell keratinocytes without melanosomes

Merkel cell

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Where are Merkel cells found?

basal layer

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The dermis is thickest in the __ and thinnest in the __.

upper back

eyelids

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Irregular surfaces of the dermis

dermal papillae

T/F. Dermal papillae are more numerous in thin skin because they lack stratum lucidum.

False. Increased number is needed for areas with high friction

Oh which is the dermal papillae made up?

elastic and firbocollagenous tissues, blood vessels, nerves and skin appendages

Two layers of the dermis

Papillary dermis | Reticular dermis

Composition of the papillary dermis

loose connective tissue, fibroblasts, collagen and elastic fibers

Layer of skin that is responsible for the texture and tone of the skin

Papillary dermis

T/F. The papillary dermis contains sensory receptors and blood vessels.

True

T/F. The reticular dermis is thinner that the papillary dermis.

False

Layer of skin that allows for stretching during pregnancy, ascites and weight gain

Reticular dermis

What are ascites?

For abdominal swelling

Stretch marks are broken __

elastic fibers

Interstices between collagen and elastic fibers in the reticular dermis are filled with __, mainly __.

proteoglycans | dermatan sulfate

What causes the wrinkling in some part of the body (penis, scrotum, areola of nipple)?

Loose plexuses of smooth muscle cells

Two major vascular plexuses; where are they found?

Deep plexus - between dermis and hypodermis | Superficial or subpapillary plexus - between papillary and reticular areas

Which plexus in the dermis provides the capillary network for the epidermis?

subpapillary plexus

T/F. The vascular plexuses in the dermis allows for thermoregulation

True

Elongated keratinized structures from the invagination of the epidermis; where are they not found?

Hair | palms, soles, sides of fingers, glans penis, labia minora, clitoris

Two types of hair; compare the two of them

Vellus - short, fine, higly pigmented | Terminal - coarse, darkly pigmented

Part of the hair that has keratohyline granules

Internal root sheath

Three components of the internal root sheath

Henle's layer Huxley's layer Cuticle

Part of the hair that is continuous with the stratum basale and the stratum spinosum; does this take part in hair formation?

external root sheath; | no

What separates the external root sheath from the connective tissue sheath?

Glassy membrane

T/F. The glassy membrane is continuous with the basement membrane.

True

Hair texture and their corresponding cross-sections

Straight hair - circle Wavy hair - oval Curly hair - kidney-shaped

Three phases of hair growth

anagen catagen telogen

Phase of active growth of hair

anagen

Resting phase of hair; what does this entail?

catagen; arrested growth and regression of hair bulb

Phase of hair growth of follicular regression; period of inactivity during which hair may be shed

telogen

Part of the nail that corresponds to the stratum corneum

Nail plate

The nail bed is composed of which layers of skin

Stratum basale and spinosum

Part of the nail that is composed of actively dividing cells

Nail matrix

Also known as the cuticle

Eponychium

What is the skin fold under the free edge of the cuticle?

Hyponychium

Whitish crescent-shaped opaque nail matrix

Lunula

Highly vascular part of the nail

Nail bed dermis

T/F. Because of the degree of vascularization of the nail bed dermis, it is inevitably part of the nail formation

False. The nail bed has nothing to do with nail formation

An appendage located above the insertion of the arrector pili muscle

sebaceous gland

Morphological classification of sebaceous glands

simple branched acinar

What is the classification of sebaceous glands according to manner of secretion?

Holocrine

Morphological classification of eccrine sweat glands

simple coiled tubular

Two portions of eccrine sweat glands

Secretory and duct

Part of the secretory portion of eccrine sweat glands that have granules? that don't have granules? Which produce most of the the secretions?

Dark cells; Clear cells; Clear cells

Third cell type in the secretory portion; what does it do?

Myoepithelial cell; contracts to move the watery secretion into the duct

The duct part of the eccrine sweat glands have __ and __ layers. The __ is more heterochromatic.

outer and inner | outer

The __ layer of the ducts of eccrine sweat glands borders the lumina. The cells here are more cuboidal with __

inner | microvilli

For what are the microvilli found in the inner layer of the ducts of eccrine sweat glands?

reabsorption of sodium, water and ions

T/F. Fluid secreted by the eccrine sweat glands is viscous and not watery.

false

Composition of the fluid secreted by the eccrine sweat glands; it is known as __

sodium, uric acid, water | sweat

T/F. Apocrine sweat glands are actually merocrine glands.

True. Apocrine is a misnomer

Apocrine sweat glands are found in which regions

axilla, areola of the nipple, mons pubis and circumanal regions

Secretory portions of the apocrine sweat glands are found in which layer of the skin? What is their morphological classification?

dermis | coiled tubular

Two examples of modified apocrine glands

Glands of Moll in the eyelid | Ceruminous gland in the ear canal

T/F. Apocrine sweat glands always secerete to an adjacent hair follicle

True

T/F. Sensory receptors are strictly composed of myelinated nerves only

False. They can be non-myelinated

Two broad categories of sensory receptors

free nerve endings | encapsulated nerve endings

Free nerve endings are mainly for __ and __

itch and pain sensation | temperature changes

Disc-like endings in that may be present in free nerve endings

Merkel endings

These are known as the mechanoreceptors for touch; they are found in __

Meissner's corpuscles | dermal papillae of glabrous skin

T/F. Meissner's corpuscles are fully myelinated

False, they contain unmyelinated nerve ending surrounded by Schwann cells

These mechanoreceptors are responsible for coarse touch, pressure and vibration

Pacinian corpuscles

Mechanoreceptors to forces found in the sole or tensional forces

Ruffini's corpuscles

Resemble small Pacinian corpuscles that are found in the papillary layer of the dermis

End bulbs of Kraus

The nerves of the efferent nervous system fibers form the sympathetic component of the ANS are (myelinated/non-myelinated)

non-myelinated

The efferent nervous system supply the __ and __

blood vessels | skin appendages