Module 4 - Integument and Somatosensation Flashcards
These unencapsulated tactile receptors are specialized epithelial cells in the stratum basale which release chemicals to stimulate sensory nerve endings:
tactile (Merkel) cells
Which cells play a role in initiating immune responses to pathogens that invade the skin?
dendritic (Langerhans) cells
What can be found at the base of hair follicles?
Unencapsulated tactile receptors
Tactile (Meissner’s) corpuscles provide sensory information about
Light touch
Which sensory receptors respond to continuous deep pressure and skin distortion?
bulbous (Ruffini) corpuscles
Which sensory receptor is responsible for providing information about pain and temperature?
Free nerve endings
Hypodermis (Subcutaneous Layer)
-Not part of the integument
-Composed of vascularized areolar and adipose connective tissues
-Functions to protect underlying structures, stores energy, thermal insulation
-directly below dermis
Epidermis
-outermost/top layer of skin
-Comprised of 4-5 sub-layers
Keratinocytes
-a cell that manufactures and stores the protein keratin
-waterproof the skin
-Vitamin D synthesis
-Production of antibiotics and enzymes to detoxify skin
-Joined by desmosomes
Keratin
intracellular fibrous protein that gives hair, nails, and skin their hardness and water-resistant properties
How many layers does “thin skin” have as opposed to “thick skin”?
Thin: skin that has four layers, most of our skin is classified as this
Thick: has a fifth layer, the stratum lucidum, only found in palms of hand and soles of feet
Melanocytes
-Produce melanin (skin pigment)
-Absorption of UV light
-Transfer melanin to keratinocytes via cell processes
-scattered in stratum basale and taken up by keratinocytes
Melanin
gives hair and skin its color and helps protect the epidermis’ living cells from ultraviolet (UV) radiation damage.
Melanosome
Cellular vesicle that transports melanin produced by melanocytes into keratinocytes
Tactile Cells
-Found in stratum basale
-Specialized mechanoreceptor that senses light touch
-Will send signal to sensory neuron at the epidermal-dermal junction
Tactile (Merkel) disc
-junction between tactile cell and neuron
-Associated with tactile cells in stratum basale of epidermis
-Light touch
Epidermal dendritic (Langerhan’s) cells
-Part of the immune system
-Take up foreign proteins via endocytosis & transport to nearby lymph nodes to begin an immune response
-engulf bacteria, foreign particles, and damaged cells that occur in this layer.
Stratum basale
the deepest layer of the epidermis consisting of stem cells capable of undergoing cell division to form new cells
Stratum spinosum
-a layer of the epidermis that provides strength and flexibility to the skin
-spiny due to the protruding cell processes that join the cells via a structure called a desmosome.
-composed of eight to 10 layers of keratinocytes, formed as a result of cell division in the stratum basale
-protects body from foreign substances
Stratum granulosum
-Keratinocytes are becoming flattened
-Serves as waterproof layer
-cells generate large amounts of the proteins keratin and keratohyalin, which accumulates lamellar granules within the cells.
Stratum lucidum
-Thin layer found only in thick skin (palms, finger tips, soles of feet)
-Additional water barrier
-smooth, seemingly translucent layer of the epidermis located just above the stratum granulosum and below the stratum corneum
Stratum corneum
- most superficial layer comprised of 15-30 layers of dead, flat keratinocytes
-cells in this layer are shed periodically and are replaced by cells pushed up from the stratum granulosum
-entire layer is replaced during a period of about 4 weeks.
Nails
-Modification of the stratum corneum
-Protect the distal dorsal fingertips
Hair
-Columns of keratinocytes
-protection, heat retention, and sensory reception
-Arrector pili muscles attach to hair root
-Sebaceous glands secrete oily sebum: softens and lubricates hair and skin
-originate in an epidermal penetration of the dermis called the hair follicle.
Arrector pili
-smooth muscle
-contracts in response to nerve signals from the sympathetic nervous system, making the external hair shaft “stand up.” (gives goosebumps)
Sebaceous glands
- type of oil gland found all over the body and helps to lubricate and waterproof the skin and hair
- generate and excrete sebum, a mixture of lipids, onto the skin surface, thereby naturally lubricating the dry and dead layer of keratinized cells of the stratum corneum, keeping it pliable.
Sweat glands
-widely distributed exocrine glands in dermal layer of skin
-thermoregulation, secretion, protection
Dermis
-thickest layer comprised of 2 sub layers
-contains blood and lymph vessels, nerves, and other structures, such as hair follicles and sweat glands
Papillary layer
-Composed of areolar CT
-Dermal papillae and epidermal ridges interlock for increased surface area
-projects into the stratum basale of the epidermis to form finger-like dermal papillae
-layer contains phagocytes, lymphatic capillaries, nerve fibers, and touch receptors called the tactile (Meissner) corpuscles.
Dermal papillae
-a fingerlike projection of the dermis that may contain blood capillaries or Meissner corpuscles (of touch)
-Found in the upper layers of the dermis, they create your fingerprint pattern
Friction ridges
Folds of epidermis and dermis on fingers, palms, soles, and toes
Reticular layer
-Underlying the papillary layer; is much thicker; composed of dense, irregular connective tissue
–> W/ bundles of collagen fibers, blood vessels, glands, hair
follicles, and nerves
-supplies the skin with oxygen and nutrients
Lines of cleavage (Langer’s lines)
Collagen and elastin fibers organized thin parallel bundles to resist
stresses
Receptive fields
Extoreceptors: receptors under the skin that responds to stimuli such as touch, temperature and pain (Found in skin or mucous membranes)
Interoceptors: Found in the walls of viscera; detect stretching, oxygen,
temperature, and pressure
Proprioceptors: Found in muscles, tendons and joints; detect body and limb movement
Tactile receptors
provide sensations of touch, pressure, and vibration
Unencapsulated tactile receptors
not wrapped in myelin or a modified myelin sheath: free nerve endings, tactile (merkel) discs, root hair plexus
Free nerve endings
-Found in papillary layer of dermis and deep epidermis
-Pain, Temperature, (also light touch)
Root hair plexuses
-Surround hair follicles in dermis
-Movement of hairs – light touch
Encapsulated tactile receptors
are wrapped in a modified myelin sheath: tactile (Meissner) corpuscles, Lamellated (Pacinian) corpuscles, Bulbous (Ruffini) corpuscles
Lamellated (Pascinian) corpuscles
-In dermis, subcutaneous tissue, synovial membranes, and some viscera
-responds to deep pressure & high-frequency vibration
Bulbous (Ruffini) corpuscles
-In dermis and subcutaneous layer
-Continuous deep pressure, force/motion and skin distortion
Tactile (Meissner) corpuscles
-In tips of some dermal papillae
-Light touch, texture, shape, low frequency vibration
Eccrine sweat gland
produces a hypotonic sweat for thermoregulation. These glands are found all over the skin’s surface but are especially abundant on the palms of the hand, the soles of the feet, and the forehead.
Apocrine sweat gland
-usually associated with hair follicles in densely hairy areas, such as armpits and genital regions
-larger than eccrine sweat glands and lie deeper in the dermis, sometimes even reaching the hypodermis
Why do we have fingerprints?
Results of dermal & epidermal ridges (Friction ridges) formed in part by the dermal papilla; increases friction for grasping
When skin is overstretched, collagen fibers may tear to form:
striae (stretch marks)
Basal Cell Carcinoma
cancerous growth in the stratum basale
Squamous Cell Carcinoma
cancerous growth in the stratum spinosum
Malignant Melanoma
cancerous growth of melanocytes
