Highison: Integument Flashcards
The skin makes up (blank)% of total body weight
16%
The skin is a window to disease states. List three.
Jaundice
Cyanosis
Measles and chicken pox
Functions of the skin: protection, (blank) receptor, role in (blank), metabolism of (blank), and regulation of (blank x2)
sensory; excretion; VitD; blood pressure and body temperature
General organization of the skin: two parts. What lies beneath these two parts?
epidermis and dermis; hypodermis
What is the epithelium of the epidermis?
keratinized stratified squamous epithelium
What is the epidermis derived from? How often is it regenerated?
derived from surface ectoderm; regenerates every 30 days
When do keratinocytes divide?
at night - get your beauty sleep ;)
The epidermis overlies projections of the (blank) forming a series of epidermal ridges, or (blank)
dermis; fingerprints
How many layers in the epidermis? List them from deep to superficial
5 layers
basement membrane 1. stratum basale 2. statum spinosum 3. stratum granulosum 4. stratum lucidum 5. stratum corneum layers of thick skin
These cells make up most of epidermis and display continuous turnover
keratinocytes
Describe the process of cell turnover
cell renewal (mitosis)
differentiation (keratinization)
cell death
exfoliation
The stratum basale is a layer of the epidermis. It rests on a (blank). It has these cells which divide continuously. It also contains these two cell types
basal lamina; keratinocytes; melanocytes; Merkel’s cells
What do keratinocytes possess? What increases as these cells approach the surface?
desmosomes, hemidesmosomes, cytokeratin; cytokeratin increases as these cells approach the surface
This layer of the epidermis is several layers thick.
It has tonofibrils and desmosomes which create spiny processes.
Characteristic cell of this layer = prickle cells with intercellular bridges.
Keratinocytes in deepest layers are mitotically active.
Also contains melanocytes and Langerhans cells.
Stratum spinosum
Spiny processes of the stratum spinosum are made up of these two things
tonofibrils (bundles of cytokeratin) and desmosomes
These cells are characteristic of the stratum spinosum
prickle cells with intercellular bridges
These cells in the deeper layers of the stratum spinosum are mitotically active
keratinocytes
Stratum spinosum also contains these cell types
melanocytes
Langerhans cells
These two layers together are known as the Malpighian layer, they are the mitotically active layers of the epidermis
stratum basale
stratum spinosum
This layer of the epidermis contains lamellar bodies, membrane-less keratohyalin granules, and bundles of tonofilaments (cytokeratin).
Contains membrane coated lamellar bodies that fuse with the plasma membrane and release GAGs and phospholipids into the intercellular spaces. This is important in sealing the deeper layers and water proofing.
stratum granulosum
3 components of stratum granulosum
- lamellar bodies
- membrane-less keratohyalin granules
- bundles of tonofilaments
The stratum granulosum contains membrane coated lamellar bodies that fuse with the plasma membrane. What two things do they release into the intercellular spaces? Why is this important?
GAGs and phospholipids
This is important in sealing the deepest layers and water proofing the skin
What do the keratohyaline granules of the stratum granulosum contain to bind the tonofilaments together to form keratin? This marks the first step in what process?
keratohyalin granules contain HISTADINE and CYSTINE rich proteins which bind to tonofilaments together to form keratin; this is the first step in keratinization
What is keratinization?
the conversion of granular cells to cornified cells
3 features of keratinized cells
- loss of organelles
- thickened plasma membrane
- bundles of tonofilaments
This layer of the epidermis is seen only in thick skin. It is acidophilic, and contains immature keratin which is called eleidin.
stratum lucidum
What does the stratum lucidum contain?
immature keratin, called eleidin
Where is stratum lucidum found?
thick skin –> palmar and plantar skin
This is the most superficial layer of the epidermis. It contains dead, plate-like enucleated keratinocytes containing mature keratin. The keratin birefringement scleroprotein has at least 6 polypeptides + tonofilaments.
stratum corneum
Disease state: accelerated keratinocyte mitosis in stratum basale and spinosum. Turnover (1 week instead of 4 weeks) leads to thickening of epidermis.
psoriasis
Psoriasis is a chronic epidermal-dermal disease. What are two characteristics of this disease?
- persistent hyperplasia of the epidermis by abnormal cell proliferation
- abnormal microcirculation in the dermis capillary plexus
2 nonkeratinocytes in the epidermis
- Langerhan’s Cells
2. Merkel’s cells
Where do Langerhans’ cells originate? What system are they a part of? What do they contain? What’s on their surface?
originate in bone marrow, part of MNP system, contain Birbeck’s Granules (rod like or racket shaped), have cell surface antibody and compliment receptors
Langerhans’ cells are capable of (blank). In which layer are they primarily located? Other places they might be found? What’s their function?
phagocytosis; primarily located in the stratum spinosum; also found in oral, esophageal, rectal, vaginal epithelium and thymus; antigen presenting cells though to initiate allergic contact dermatitis reaction
Where are Merkel’s cells found? What are they derived from? What two things do they possess? Where are they most numerous and when do they appear there? What are they considered?
stratum basale; derived from neural crest; possess desmosomes and tonofilaments; most numerous in thick skin (plantar and palmar epidermis) and appear there at about 8-12 weeks gestation; they are sensory/tactile mechanoreceptors
Merkel cells are associated with the (blank). The cytoplasm contains (blank). A small nerve plate is connected to a (blank)
basal lamina; granules; myelinated axon
Melanins contribute to pigmentation of these three things
skin
eyes
hair
patches of epidermal melanin
freckles
What are melanins synthesized by?
melanocytes
What are melanocytes derived from? When are they visible? Where are their cell bodies found? Do they have desmosomes? Melanocytes have cytoplasmic extensions that make contact with about 36 keratinocytes and form this.
derived from neural crest; 8th embryonic week; in stratum basale; NO desmosomes; epidermal-melanin unit
Where is the site of melanin granule synthesis?
melanosomes
Melanosomes contain this UV-sensitive enzyme involved in melanin synthesis
tyrosinase
What accounts for the differences in color in different races?
NOT a difference in number of melanocytes per unit area. Rather, differences in the rates of melanin synthesis, accumulation, and degradation.
Where do mature melanin granules from the Golgi move to? Where are they injected into?
tips of melanocytes; injected into keratinocytes of basale and spinosum via cytocrine secretion
Most melanin is found in (blank) rather than melanocytes
keratinocytes
Melanin granules accumulate over the nuclei of diving keratinocytes. What does this do?
protects the DNA from damaging effects of the sun’s rays