CHAPTER 5 Flashcards
Skin
body’s largest organ. 2 layers, epidermis/dermis within skin plus one nearby.
Epidermis
epithelium of skin- superficial region outtermost protective shield of body
Tissue type
keratinized stratified squamos epithelium 4 cell types 4-5 layers
Vascularity
Epidermis is avascular- nutrients diffuse from deeper connective tissue
cells of epidermis
superficial cells are dead no nuclei- sparse nerve endings
keratinocytes
(no nuclei) synthesize keratin vast majority of epidermal cells/ found in many layers
keratinocyte- function
gives epidermis its productive properties
keratinocyte- location
keratinized stratified squamos epithelium- arise stratum basale pushed up as grow due in stratus corneum
melanocytes
spider shaped epithelial cells make melanin a brown to black pigment
melanocytes- function
taken up by keratinocytes and used to protect their DNA from ultraviolet radiation
melanocytes- location
stratum basale
dendritic cells (Langerhans)
star shaped cells, immune surveilance.
dendritic cells- function
protect from microbes, toxins, and pathogens. ingest foreign substances, activate immune system
dendritic cells- location
stratum spinosum, stratum granulosum, (2 middle layers of epidermis) arise bone marrow migrate to epidermis
Tactile cells (Merkel)
touch receptors that join with nerves. shaped like spiky hemispheres
Tactile cells- function
sensory receptors for touch, associated with sensory nerve ending
Tactile cells- location
stratum basale
Layers of the Epidermis
variation in epidermal thickness determines thick or thin
Stratum basale
germinating layer- attached to dermis, single row of stem cells
Stratum basale- cells
melanocytes, keratinocytes, and tactile (merkel)
Stratum basale- function
regenerates new basal cells
Stratum spinosum
prickly layer- several layers thick
Stratum spinosum- cells
keratinocytes and Langerhans (dendritic)
Stratum spinosum- function
cells contain thick bundles of intermediate filament that are made of pre keratin
stratum granulosum
3-6 cell layers thick
stratum granulosum cells
keratinocytes (organelles deteriorating) cytoplasm full of lamellated granules and keratohyaline granules
Stratum lucidum
visible only in thick skin, thin translucent band or zone
Stratum lucidum cells
2-3 rows of clear flat dead keratinocytes
Stratum lucidum- function
stick corneum to granulosum, provide little protection
Thick skin
areas of high abrasion, epidermis 5 strata (layers) and thicker stratum corneum. palm, fingertips, soles of feet
Thin skin
rest of body, 4 strata
Stratum corneum
20-30 cell layers thick make up 3/4 epidermal thickness, outtermost layer
Stratum corneum- cells
dead keratinocytes
Stratum corneum- function
protect from abrasion, penetration, and dehydration
Dermis- beneath epithelium
second major skin region, strong flexible connective tissue contains nerve fibers, blood and lymphatic vessels, hair follicles, and oil/ sweat glands
Dermis vascularity
rich supply of blood vessels
dermal layers
further subdivided into 2 layers papillary and reticular
Papillary layer
thin superficial layer
Tissue type
areolar connective tissue contain collagen and elastic fibers
additional structures
blood vessels
Dermal papillae
peg like projections contain capillary loops, blood vessels, free nerve endings, and meisners corpuscles (tactile)
Dermal ridges
in thick skin, large mounds found under the papillae
Epidermal ridges
formed on the overlying epidermis due to the dermal ridges, referred to as friction ridges, enhance the griping ability. ridge patterns are genetically determined and unique. when sweat pores open along their crest our fingerprints leave identifying films of sweat/fingerprint
Capillary loops
blood carrying vessels allow for exchange to occur (nutrients-wastes)
Free nerve endings
serve as pain receptors
meissners corpuscles
touch receptors
reticular layer- irregular dense fibrous connective tissue
deeper/ accounts for 80percent of dermal thickness, has cutaneous plexus and flexure lines
cutaneous plexus
network of blood vessels which nourishes reticular layer
flexure lines
dermal folds that occur at or near joints allowing for flexibility
hypodermis- connective tissue (adipose)
nearby layer known as superficial fascia, connective tissue just underneath skin. mostly made up of adipose subcutaneous tissue fund just deep to skin. stores fat and anchors skin to muscle loosely so skin can move
skin color
3 major pigments determine skin color
melanin
only one made in skin by melanocytes. subtypes eumelanin- brownish/black, phemelanin- reddish/yellow skin tones vary due to distribution of melanin (not # melanocytes)
carotene
yellow to orange pigment found in certain plant foods/ carrots, concentrates in stratum corneum
hemoglobin
a pigment which contains oxygen and found in red blood cells (pale look lack of hemoglobin)
appendages of the skin
cyanosis- blueness