Skin System Flashcards
Approximately how much of total body weight does skin comprise?
15 to 20%
What are some functions of skin?
(1) Protection against external threats (2) Provision of moisture control (3) Protection against UV radiation (4) Metabolism (synthesis of D3) (5) Thermoregulation (sweating, body hair, adipose) (6) Sensation
What is produced in the skin in response to UV exposure?
Melanin
The skin is composed of the ______________, an epithelial layer of ectodermal origin, and the _____________, a layer of mesodermal connective tissue
- Epidermis
- Dermis
At the irregular junction between the dermis and epidermis, projections called ________ ______________ interdigitate with invaginating ________ ____________ to strengthen adhesion of the two layers
Dermal papillae
Epidermal ridges
Beneath the dermis lies the _________________ tissue or ______________, a loose connective tissue layer that usually contains pads of adipocytes
Subcutaneous
Hypodermis
What type of tissue is skin primarily composed of?
Stratified squamous keratinized epithelium
What does the stratified squamous keratinized epithelium of skin primarily consist of?
Keratinocytes
Other than keratinocytes, what are three other epidermal cell types?
(1) Melanocytes, which produce pigments
(2) Langerhans cells, which present antigens
(3) Merkel cells, which provide tactile sensation
The epidermis forms the major distinction between thick skin found on the ___________ and ___________ and thin skin found elsewhere on the body
Palms
Soles
To what do the designations thick and thin refer?
The thickness of the epidermal layer
How many layers of keratinocytes are found in thin skin?
Four
How many layers of keratinocytes are found in thick skin?
Five
The _________________ layer or ____________ ______________ is a single layer of basophilic cuboidal or columnar cells on the basement membrane at the dermal-epidermal junction; it proliferates continuously with repeated mitotic divisions, where cells move upwards as they mature
Basal layer
Stratum basale
The _______________ layer or ________________ ________________ is normally the thickest epidermal layer and generally consists of polyhedral cells with central nuclei and nucleoli and active cytoplasm (producing keratins)
Spinous layer
Stratum spinosum
Which layer of the epidermis is also known as the prickle cell layer? What causes these prickles?
Spinous layer or stratum spinosum
Desmosomes
To what cytoskeletal elements do desmosomes connect?
Intermediate filaments
The ________________ layer or _____________ _________________ consists of three to five layers of flattened cells undergoing terminal differentiation of __________________; their cytoplasm is filled with intensely basophilic masses called ________________ _______________
Granular layer
Stratum granulosum
Keratinization
Keratohyaline granules
To what layer of epidermis do keratinocytes mature?
Granular layer
Stratum granulosum
Which epidermal layer is seen only in thick skin?
Stratum lucidum
Only found in thick skin, the stratum lucidum is a thin, translucent layer of extremely flattened ___________________ cells
Eosinophilic
The _______________ ________________ consists of 15 to 20 layers of flattened nonnucleated keratinized cells
Stratum corneum
What occurs to cells after they’ve undergone keratinization?
Lose their nuclei, fill their cytoplasm with filamentous keratins, and thicken their plasma membranes
Cornified cells are also called ________________
Squames
These cells are continously shed at the surface of the stratum corneum
Squames or nonnucleated keratinized cells
The designations “thick” and “thin” refer to the thickness of the epidermal layer, which varies from ___ to ___ micrometers in thin skin and ___ to _____ micrometers in thick skin
75 to 150
400 to 1400
What’s the order of epidermal layers from top to bottom?
Statum corneum
Stratum lucidum (thick skin only)
Stratum granulosum
Stratum spinosum
Stratum basale
The color of the skin is the result of several factors, the most important of which are the keratinocytes’ content of _____________ and ________________ and the number of blood vessels in the dermis
Melanin
Carotene
_____________ are brown or black pigments produced by the melanocyte, a specialized cell of the epidermis found among the cells of the ___________ layer and in hair follicles
Eumelanins
Basal layer
_________________ is produced in red hair
Pheomelanin
What are the histological features of melanocytes?
Pale staining, rounded cell bodies attached by hemisdesmosomes to the basal lamina, but lacking attachments to neighboring keratinocytes
Several long irregular cytoplasmic extensions from each melanocyte penetrate the epidermis, running between the cells of the basal and spinous layers
Antigen-presenting dendritic cells of the epidermis are called _______________ cells and are most clearly seen in the spinous layer, representing between two and eight percent of epidermal cells
Langerhans cells
______________ cells or epithelial tactile cells are sensitive mechanoreceptors essential for light tough sensation
Merkel cells
The _________________ is the layer of connective tissue that supports the epidermis and binds it to the subcutaneous tissue
Dermis
The thickness of the dermis varies according to the region of the body, but a ______________ _________________ is always found between the stratum basale of the epidermis and the _____________ layer of the dermis
Basement membrane
Papillary layer
The thin _____________ ___________ of the dermis includes the dermal papillae and consists of loose connective tissue
Papillary layer
Below the papillary layer is the ___________ ____________, which is much thicker and consists of dense irregular connective tissue with more fibers and fewer cells; a network of elastic fibers is also present
Reticular layer
In the dermis, spaces between collagen and elastic fibers are filled with proteoglycans rich in _________________ ____________
Dermatan sulfate
The ____________________ tissue refers to the loose connective tissue that binds the skin loosely to the subjacent organs, making it possible for the skin to slide over them
Subcutaneous
What layer of tissue contains many fat cells and an extensive vascular suppy and is referred to as the hypodermis?
Subcutaneous tissue
The connective tissue of the skin contains a rich network of blood and lymphatic vessels; the blood vessels that nourish the cells of the skin form two major plexuses. Where do these plexuses occur?
- Deep at the interface between the hypdermis and dermis
- Superficially between the papillary and reticular dermal layers
___________ _________________ are elongated keratinized structures derived from invaginations of the epidermal epithelium
Hair follicles
The growing hair follicle has a terminal dilation called the ____________ __________
Hair bulb
A ______________ ____________ inserts into the base of the hair bulb and contains a capillary netwro required to maintain the hair follicle
Dermal papilla
Epidermal cells covering the dermal papilla form the _____________ ___________ that produces and is continuous with the ____________ _____________
Hair root
Hair shaft
_________________ are modifications of the epidermis that are composed of keratin and contain a free edge, body, and a root
Nails
The proximal part of the nail is the ____________ ___________ and is covered by a fold of skin, from which the epidermal stratum corneum extends as the _______________
Nail root
Cuticle
The _________ ___________ is bound to a bed of epidermis, the _________ ______, which contains only the basal and spinous epidermal layers
Nail plate
Nail bed
The nail root forms from the __________ ____________ in which cells divide, move distally, and become keratinized
Nail matrix
The crescent-shapped white area of the nail is called the ________________, which derives its color from the opaque nail matrix and immature nail plate below it
Lunula
_____________ __________ are embedded in the dermis over most of the body
Sebaceous glands
________________ is a complex mixture of lipids that are secreted from sebaceous glands; it is gradually moved to the surface of the skin along the hair follicle or duct
Sebum
____________ ___________ develop as long epidermal invaginations embedded in the dermis and open to the skin surface or into hair follicle
Sweat glands
What type of sweat gland is found widely distributed in the skin and is most numerous on the soles of the feet?
Eccrine sweat glands
What type of sweat gland is confined to the axillary and perineal regions?
Apocrine sweat glands
What is the most obious histological difference between eccrine and apocrine sweat glands?
Apocrine glands have much larger lumens
The ______________ can be identified by its broad dermis and subcutaneous layers and abudant hair follicles
Scalp
What part of the skin is characterized by the lack of hair and has developed structural modifications to resist shearing and frictional forces?
Soles
What are some of the histological characteristics of soles?
A thick epidermis and prominent granular layer
A thick layer of keratin
Increased rete ridges to increase surface area
Why do the soles have increase rete ridges?
To increase surface area of epidermis attached to the dermis
