skin histology module Flashcards
thick skin does not have
hair follicles, sebaceous glands, arrector pili muscles
where is thick skin
what does it lack
palms and plantar
lacks hair follicles, sebaceous glands
what is thin skin
what does it lack
lacks a stratum lucidum
most superficial layer of skin
epidermis
shape of cells in epidermis
stratified squamous keratinized epithelium
also melanocytes, langerhans and merkel cells
regeneration of epidermis
constant - about every 30 days
carried out by mitotic keratinocytes
cells normally divide at night
desmosomes
connect kerotinocytes together
hemidesmosomes
connect keratinocyte to basement membrane
where are melanocytes?
stratum basale
function of melanocytes
synthesize melanin in melanosomes
what does melanin do
protect against tissue damage and degradation patters
_____ increases production and changes of melanocytes
sunlight
where are langerhans cells located
primarily in the stratum spinosum
shape of langerhans cells
comma like appearance, appears pale
function of langerhans cells
antigen presenting cells in immune responses to contact antigens/allergies and some skin grafts
birbeck granules
inside langerhans cells - cytoplasmic organelles that look like tennis racket
where are merkel cells
stratum basale enar areas of well vascularized, richly innervated connective tissue
function of merkel cells
receive afferent nerve terminals and are believed to function as sensory mechanoreceptors
stratum basale
deepest layer of the epidermis
composition of stratum basale
keratinocytes, melanoyctes, langerhans, merkel
stratum spinosum
- keratinocytes connected by desmosomes
- mitotically active in deeper region
keratinocytes membrane coating granules
in the superficial regions of the stratum spinosum, the contents of the granules are released into the intercellular spaces in the form of lipid-containing sheets that are impermeable to water and many foreign substances
stratum granulosum
most superficial layer in which nuclei are still present
3-5 (10-12 nm thick) layers of flattened keratonocytes with keratohyalin granules
keratohyalin granules
- in stratum granulosum
- contain histidine and cystine rich proteins which bind the keratin filaments together
- not membrane bound
stratum lucidum
- clear homogenous layer just superficial to stratum granulosum
- found only in thick skin - palmar and plantar
cells if stratum lucidum
consists of keratinocytes that have neither nuclei nor organelles but have keratin filaments and eleidin
eleidin
transformation product of keratohyaline
stratum corneum
- most superficial layer
- 15-20 layers of flattened, non nucleated “dead cells”
- squames that are 14 polygon shaped
outermost layer of stratum corneum
squames that are continuously shed by desquamation
layers of the epidermis
corneum lucidum granulosum spinosum basale
come lets get some beer
layers of the dermis
papillary and reticular
what beer? PbR
the dermis is composed of dense, irregular connective tissue with _________ and ______
type 1 collagen fibers and elastic fibers
papillary layer
- superficial thin layer of connective tissue that interdigitates with epidermal ridges of the epidermis
- forms dermal papillae where meissner corpuscles and capillary loops may be found
- contains delicate collage fibers (type 1 and III_
- contains anchoring fibrils (type VII collagen), microfibrils (fibrillin) and elastic fibers
meissner corpuscles
fine touch receptors
reticular layer
- deep layer of dermis
- major portion of dermis
- dense bundles of collagen fibers (type 1) and thick elastic fibers
- arteries, veins, and lymphatics are present
- location of sweat glands and their ducts
- pacinian corpuscles and nerves
- in thin skin, contains hair follicles, sebaceous glands and arrector pili muscles
corpuscles of papillary layer
- contains capillary loops and meissner corpuscles (fine touch)
corpuscles of reticular layer
pacinian corpuscles (pressure receptors) and kraus end bulbs
arrector pili muscle
- smooth muscle
- under sympathetic control
- contracts to elevate hair - goose bumps
name for sweat gland
eccrine
eccrine sweat gland
- simple coiled tubular glands present in skin throughout the body
shape of sebaceous gland
acinar
stratified cuboidal
secretory unit of eccrine sweat gland
- embedded in dermis:
- dark cells contain mucinogen rich secretory granules
- clear cells secrete a watery electrolyte rich material
- myoepithelial cells are scattered in beneath clear cells, they contract and aid in expressing the glands secretions into the duct
how do sweat glands secrete sweat?
contraction of myoepithelial cells
dark cells
line the lumen of the gland in eccrine sweat unit
clear cells
rich in mitochondria and glycogen, contain intercellular canaliculi that extend to lumen of gland
location of apocrine sweat gland
anus, axilla, areola, cerumen of external ear
function of apocrine sweat gland
- empty viscous odorless secretions into hair follicles near sebaceous gland ducts
- bacteria act on these secretions to produce odors unique to a person
what makes apocrine glands smell
not secretions, but bacteria that digest secretions
structure of sebaceous gland
secretory unit - branched acinar
duct - empties into neck of a hair follicle
location of sebaceous gland
face, forehead, scalp
absent in thick skin (palms and soles)
function of sebaceous gland
holocrine glands that release sebum - oily secretion and degenerating epithelial cells
types of secretion mechanisms
holocrine - sebaceous
merocrine - eccrine and salivary
apocrine - lactating mammary
holocrine secretion
release entire secretory cell and its contents
merocrine secretion
exocytosis
apocrine secretion
release part of apical cytoplasm
myofibroblast
contains high amounts of actin and myosin for contraction
contracts during wound healing
meissners corpuscles
- in dermal papillae of thick skin, eyelids, lips, and nipples
- function in fine touch perception
pacinian corpuscles
- in dermis and hypodermis and in the connective tissue of the mesenteries and joints, especially being abundant in the digits and breasts
- perceive pressure, touch, and vibration
shape of cells in dermis
stratified cuboidal epithelium in sweat glands
