Integumentary Flashcards
largest single organ of the body ; 15%-20% of total body weight
Skin
two major layers of skin
Epidermis and Dermis
an epithelial layer of ectodermal
origin ; the one directly observed physically
Epidermis
a layer of mesodermal connective
tissue ; the thickest layer, divided into the
papillary layer and reticular layer
Dermis
Structures that are embedded in the skin but
otherwise considered as a separate organ/tissue
Epidermal derivatives of the skin
The four epidermal layers of the skin
Hair follicles and hair
Sweat (sudoriferous) glands
Sebaceous glands
Nails
Functions of the Skin
Protective
Sensory
Thermoregulatory
Metabolic
Sexual signaling
provides a physical barrier against thermal
and mechanical insults
Protective
allow skin to
constantly monitor the environment
Sensory
skin’s insulating components and its
mechanisms for accelerating heat loss
Thermoregulatory
Cells of skin synthesize vitamin D3, needed in
calcium metabolism and proper bone
formation
Metabolic
effects of sex pheromones produced by
the apocrine sweat glands
Sexual signaling
consist mainly of a stratified squamous
keratinized epithelium composed of cells called keratinocytes
Epidermis
Cells in Epidermis
Keratinocytes
Langerhan cells
Melanocytes
Merkel cells
production of the protein
keratin ; Predominant cell type of the epidermis
Keratinocytes
skin macrophage ; It possesses characteristic, tennis racquet-shaped Birbeck granules ; Most clearly seen in the spinous layer
Langerhan cells
produces melanin ; Neural crest-derived ; dendritic cell that is scattered among the
basal cells of the stratum basale
Melanocytes
granules that contain melanin
Melanosomes
precursor of melanin
Tyrosine
Epithelial tactile cells ; Function in cutaneous sensation ; Abundant in highly sensitive skin like that of fingertips and at the bases of some hair follicles ; Located in the stratum basale
Merkel cells
Thick skin
Palms and soles
Thin skin
Elsewhere on the body
─stratum basale
─stratum spinosum
─stratum granulosum
─stratum lucidum
─stratum corneum
Layers of Epidermis
Basal layer (stratum basale)
Spinous layer (stratum spinosum)
Granular layer (stratum granulosum)
Stratum lucidum
Stratum corneum
single layer of basophilic cuboidal or
columnar cells ; Characterized by intense mitotic activity and contains ; Important feature – cytoskeletal keratins
Basal layer (stratum basale)
Thickest layer, especially in the epidermal
ridges ; Synthesis of much keratin and other proteins takes place ; exhibit spinous processes
Spinous layer (stratum spinosum)
Keratinocytes in this layer contain numerous
keratohyalin granules
Granular layer (stratum granulosum)
important in the aggregation of the keratin
filaments ; cysteine rich and histidine rich proteins considered as the precursors of the protein filaggrin ; when released by exocytosis would usually
produce a layer that is lipid rich around the cell
Lamellar granules
Consists of a thin, translucent layer of
flattened eosinophilic keratinocytes held
together by desmosomes ; a subdivision of the stratum corneum ; Only well seen in thick skin
Stratum lucidum
Most differentiated cells in the skin; Layers of squamous, keratinized cells filled with birefringent filamentous keratins ; Squames- Layers of dead skin cells
Stratum corneum
layer of connective tissue that supports the
epidermis and binds it to the subcutaneous tissue (hypodermis)
Dermis
Layer of the Dermis
Papillary layer
Reticular layer
what lies between the papillary and reticular dermal layers
microvascular subpapillary plexus
are the extension of the
epidermis to the dermis
Epidermal ridges
are projections of the dermis
unto the epidermis
Dermal papillae
Thin ; Topmost layer of the dermis ; Includes the dermal papillae ; Consists of loose connective tissue ; Types I and III collagen fibers, fibroblasts and scattered mast cells, macrophages, and other leukocytes
Papillary layer
Much thicker ; Consists of dense irregular connective tissue ; More fibers and fewer cells than the papillary layer ; A network of elastic fibers is also present
Reticular layer
Consists of loose connective tissue that binds
the skin loosely to the subjacent organs,
making it possible for the skin to slide over
them ; Contains adipocytes ; Extensive vascular supply
Hypodermis or superficial fascia (Subcutaneous Tissue)
the skin functions as an extensive receiver for various stimuli from the environment
Sensory Receptors
Unencapsulated sensory receptor
Merkel cells
Free nerve endings
Root hair plexuses
Encapsulated sensory receptor
Meissner corpuscles
Lamellated (pacinian) corpuscles
Krause end bulbs
Ruffini corpuscles
Tonic receptors for sustained light touch and
for sensing an object’s texture ; Tactile disc
Merkel cells
Most numerous neuronal receptors in the
epidermis ; Start in stratum basale ; Terminate in the stratum granulosum ; Respond primarily to high and low temperatures, pain, and itching, but also
function as tactile receptors
Free nerve endings
A web of sensory fibers surrounding the bases of hair follicles in the reticular dermis that detects movements of the hairs
Root hair plexuses
Elliptical structures, consisting of sensory
axons winding among flattened Schwann cells arranged perpendicular to the epidermis in the dermal papillae ; Touch receptors ; Responsive to low frequency stimuli in the papillary layer of hairless skin
Meissner corpuscles
large oval structures with an outer capsule
and 15-50 thin ; found deep in the reticular dermis and hypodermis ; wall of the rectum and urinary bladder ; specialized for sensing coarse touch, pressure, and vibrations
Pacinian corpuscles
Simpler encapsulated, ovoid structures, with
extremely thin, collagenous capsules
penetrated by a sensory fiber ; Found primarily in the sin of the penis and
clitoris where they sense low frequency
vibrations ; Also known as bulboid corpuscle/genital corpuscle ; Detects cold as a thermo receptor
Krause end bulbs
Collagenous, fusiform capsules anchored
firmly to the surrounding connective tissue ; Respond to stretch and torque ; Detects warm temperature
Ruffini corpuscles
elongated keratinized structures that form within epidermal invaginations, the hair follicles
Hair
growing hair follicle has a terminal dilation called a hair bulb
Hair
base of the bulb is invaginated by a tuft of vascularized loose connective tissue called a dermal papilla
Hair
these cells form the matrix of the elongating hair root ; the part of a hair extending beyond the skin surface is called the hair shaft
Hair
the part of a hair extending beyond the skin surface
hair shaft
A generally long period of mitotic activity and growth
anagen
A brief period of arrested growth and regression
of the hair bulb
catagen
A final long period of inactivity
telogen
hard plates of keratin on the dorsal surface of each distal phalanx
Nail
The proximal part of the nail
nail root
bound to a bed of epidermis, which contains only the basal and spinous epidermal layers
nail bed
forms from the nail matrix in which
cells divide, move distally, and become
keratinized in a process somewhat similar to hair formation but without keratohyaline granules
nail root
embedded in the dermis over most of the body, except in the thick, glabrous skin of the palms and soles
Sebaceous Glands
branched acinar glands with several acini
converging at a short duct that usually empties into Sebaceous Glandsthe upper portion of a hair follicle
Sebaceous Glands
a hair follicle and its associated sebaceous
glands make up a pilosebaceous unit ; holocrine secretion ; Sebocytes ; Sebum
Sebaceous Glands
a complex mixture of lipids that includes
wax esters, squalene, cholesterol, and
triglycerides that are hydrolyzed by bacterial
enzymes after secretion
Sebum
helps maintain the stratum corneum and
hair shafts and exerts weak antibacterial and
antifungal properties
Sebum
Widely distributed in the skin and are most
numerous on the foot soles ; Secretory part is stratified cuboidal epithelium
Eccrine sweat glands
A physiologic response to increased body
temperature during physical exercise or
thermal stress ; Most effective means of temperature regulation of humans
Sweating
largely confined to skin of the axillary and
perineal regions ; production of pheromones ; Merocrine secretion ; Simple cuboidal ; Larger lumen
Apocrine sweat glands
Collagen-rich, well vascularized tissue in the
dermis, which gradually replaces the blood
clot ; Undergoes remodeling
Granulation Tissue
