Histology II: integumentary system, sense perspective Flashcards
Give a couple examples of skins’ exocrine function.
secretion of sweat and sebum excretion through sebaceous glands
2 main layers of the skin
epidermis and dermis
What cell type does the epidermis consist of?
keratinized stratified epithelium
What does the dermis consist of?
a dense connective tissue (collagen, elastic tissue, reticular fibers)
What process allows skin to retain its usual thickness?
desquamation
Describe the hypodermis.
also referred to as subcutaneous tissue, can be rich in adipose tissue and loose connective tissue
serves to anchor the skin to adjacent structures.
Name the 5 layers of the epidermis from outside in.
stratum corneum stratum lucidum stratum granulosum stratum spinosum stratum basale
What is stratum basale?
the innermost layer of the epidermis, which continuously produces new cells, comprised of a single layer of stem cells
What is stratum spinosum?
the 2nd to deepest layer of the epidermis
its at least several cells thick and these cells characteristically exhibit spinous processes.
What is stratum granulosum?
the very middle layer (3rd) of the epidermis
the cells contain keratohyalin granules.
What is stratum lucidum?
the 2nd layer of the epidermis but only in thick epidermis
is considered a subdivision of the stratum corneum.
What is stratum corneum?
the outermost layer of the epidermis
consists of anucleate squamous cells largely filled with keratin filaments.
Gross division for distinguishing thick and thin skin.
Thick is hairless (glabrous), thin contains hair follicles.
Name 4 cell types found in the epidermis.
keratinocytes
melanocytes
langerhans’ cells (APC cells of skin)
merkel’s cells (sensoryreceptors)
What is a keratinocyte?
is the predominate cell type in the epidermis.
originate in the basal epidermal layer.
Two essential functions of keratinocytes?
produce keratin, the major structural protein of the epidermis.
participate in the formation of the epidermal water barrier.
What are melanocytes?
cells of the epidermis that produce and secrete the pigment melanin into keratinocytes.
What are langerhans’ cells?
antigen-presenting cells in the epidermis.
What are Merkel’s cells?
modified epidermal cells located in the stratum basale and are mechanoreceptors.
What structures help secure the epidermis to the dermis?
dermal papillae and epidermal ridges
The dermis is composed of what 2 layers?
The papillary layer
The reticular layer
What is the papillary layer?
is the most superficial layer of the dermis
consists of loose connective tissue which contains blood vessels and nerve endings
What is the reticular layer?
lies deep to the dermal papillary layer
is characterized by thick, irregular bundles of collagen and by coarser elastic fibers.
Name the layers of the epidermis by their english, colloquial names.
horny layer clear layer granular layer prickle layer basal layer
In which layer of the epidermis do the neuronal receptors terminate?
stratum granulosum or granular layer (3rd)
Why are the free nerve endings of the skin referred to as “free”?
in that they lack a connective tissue or glia cells.
Name 4 types of nerve endings found in skin.
free nerve endings (eg. merkel’s discs)
Pacinian corpuscles
Meissner’s corpuscles
Ruffini’s corpuscles
Name the 3 types of encapsulated nerve endings found in skin.
Pacinian corpuscles
Meissner’s corpuscles
Ruffini’s corpuscles
Describe Pacinian corpuscles.
large ovoid structures composed of myelinated, encapsulated nerve endings
What makes a nerve ending encapsulated?
encapsulated- do not contain an open end for nerve transmission making the sensitivity low in comparison to free nerve endings.
encaps. can have a brush border of fluid filled sac
Meissner’s corpuscles found where?
are localized within dermal papillae
Ruffini’s corpuscles do what?
they respond to mechanical displacement of adjacent collagen fibers.
Pacinian corpuscles found where?
found in the deeper dermis and hypodermis.
Pacinian corpuscle function?
receptors for mechanical and vibratory pressure
Meissner’s corpuscle function?
serve as touch receptors
The hair follicle is divided into what three segments.
infundibulum
isthmus
hair bulb
What is the infundibulum of a hair follicle?
is the upper portion of the hair follicle, above the entry of the sebaceous duct
What is the isthmus of a hair follicle?
is the area between the sebaceous duct opening and the bulge which is the area of the follicle marked by the insertion of the arrector pili muscle.
What is the hair bulb of a hair follicle?
The terminal expansion of the follicle
What can be found on the underside of the hair bulb?
a deep recess occupied by dermal papilla consisting of connective tissue.
What is hair composed of
and what 3 layers make it up?
keratin
layers:
medulla
cortex
cuticle
What is the medulla of hair?
the central part of the shaft and contains large vacuolated cells
What is the cortex of hair?
is located peripheral to the medulla and contains cuboidal cells which undergo differentiation into keratin-filled cells.
What is the cuticle of hair?
the outermost layer of the hair which contains squamous cells
What is a sebaceous gland?
a simple, branched alveolar gland that secretes an oily material – sebum
What is holocrine secretion?
a mode of secretion in exocrine glands
are produced in the cytoplasm of the cell and released by the rupture of the plasma membrane, which destroys the cell and results in the secretion of the product into the lumen.
Describe sweat glands.
simple coiled glands that regulate body temperature
independent structures, not associated with hair follicles
consist of 2 segments:
a secretory segment located deep in the dermis containing secretory and myoepithelial cells,
duct segment that leads to the epidermal surface.
What are nails?
plates of keratinized cells containing hard keratin.
Describe the nail bed.
consists of epithelial cells that are continuous with the stratum basale and stratum spinosum of the epidermis.
What are claws?
are extensively developed portions of the epidermis and dermis that extends from the distal phalanges.
very prominent and hard cornified stratum.
What are hooves composed of?
Like the claw, the hoof formed in horses is composed largely of cornified epidermal tissue.
What are horns composed of?
horns possess a papillated corium covered externally by a hard cornified epidermis
Another word for dermis.
corium
