Skin-Csoka Flashcards
List the constituents of the following:
Papillary Dermis
Reticular Dermis
Hypodermis
Papillary Dermis: loose connective tissue
Reticular Dermis : DICT, type I collagen, elastic fibers
Hypodermis: adipose tissue, loose connective tissue
What type of tissue is present in the epidermis and dermis?
Epidermis: epithelial
Dermis: connective tissue
Vitamin D is produced by the penetrance of UV light.
UV light is involved in several other regulatory function
Epidermis is keratinized stratified squamous epithelium with what 5 layers?
basement membrane
stratum basale: keratinocyte cells are generated here
stratum spinosum
stratum granulosum
stratum lucidum: thin layer of clear cells
stratum corneum: the keratinized thick layer
Melanin is less abundant in thick skin. True or false?
True
Thick skin (palms, soles of feet) lack hair and sebaceous glands.
As you move up from the _______________, the cells are essentially differentiating as you’re moving upwards. The keratin is synthesized as you’re moving upwards coinciding with differentiation.
stratum basale
Keratinocytes in skin undergo distinct stages of differentiation that are found in distinct layers of the skin
What is the epithelium of epidermis?
keratinized stratified squamous epithelium
What is another term for skin?
integument= cutaneous layer
The skin is the largest organ in the body. True or false?
True!!
What is the difference between thick and thin skin?
The layers of the epidermis of thin skin are not defined as in the thick skin. Thick skin has a thicker S. corneum and pronounced S. granulosum. Thick skin also has sweat glands.
Thick skin has no hair follicles or sebaceous (oil) glands and is less pigmented. Ridges that hold epidermis to dermis are higher to resist shear.
What are the type of cells in thick skin for the following?
- S. Basale
- S. spinosum
- S. Granulosum
- S. lucidum
- S. Corneum
- S. Basale: stem cells; attached to the basement membrane
- S. spinosum: spiny (due to desmosomes)- keratinization begins
- S. Granulosum: hydrophobic lipid envelope
- S. lucidum: translucent appearance
- S. Corneum: dead cells
What attached keratinocytes to each other and to the basement membrane?
desmosomes
hemidesmosomes
What warps around the type IV collagen and hooks it to the dermis?
anchoring fibrils
What type of collagen is present in the dermis?
Type I and III
What is responsible for the spiny characteristic of stratum spinosum?
desmosomes
its appearance enhanced by dehydration and fixing as compared to in vivo; visible with both light and electron microscopes
The cells of S. granulosum stain darker due to the presence of granules which contain what? What is its function?
filaggrin which links tonofibrils together to form dense bundles of keratin that fill the cell
What is the function of keratohyaline granules?
dehydration of the cell and promotion of crosslinking of keratin fibers
How is fillaggrin made?
profilaggrin is first highly phosphorylated by kinases; when it is cleaved into filaggrin, phosphate groups are removed by phosphates
the filaggrin will then crosslink the keratin to get the layer of the S. corneum
S. Granulosum also contain this which allows for a semi-permeable barrier?
lamellar bodies with the lipid rich secretion
S. Granulosum also contain this which contains a lipid-rich secretion that is expelled into extracellular space and waterproofs the skin. Barrier is semi-permeable which is very important in pharmacology.
lamellar bodies
Stratum corneum contains this which helps to stabilize the cell membrane of the dead keratinocyte.
involucrin helps to stabilize the cell membrane in the absence of the nucleus
Stratum corneum contains this which helps to stabilize the cell membrane of the dead keratinocyte.
involucrin which helps to stabilize the cell membrane in the absence of the nucleus
This abnormality of epidermal keratinocytes generates abnormal keratinocytes and differentiation.
psoriasis
- keratinocytes reach the surface in 3-5 days instead of 30 (normal)
- thickening of the S. corneum –> microabscess in the epidermis
- influx of lymphocytes into the dermis
- angiogenesis like phenomenon occurring as well
This class of abnormality of epidermal keratinocytes is an autoimmune disease or keratin mutations. Give examples.
blistering diseases:
- bullous pemphigoid: autoimmune attack to hemidesmosomes
- pemphigus vulagaris: autoimmune attack to desmosomes; prominent in the oral cavity
- epidermolysis diseases: mutation of keratin or hemidesmosome structures; defect in anchoring between epidermis and dermis
This abnormality of epidermal keratinocytes is due to the lack of sun, high latitudes, winter, and poor diet. Give examples.
vitamin D deficiencies:
- osteomalacia: lack of bone mineralization in ADULTHOOD; softened bones
- Rickets: lack of bone mineralization in CHILDHOOD
What systems does vitamin D deficiency affect?
brain: depression, schizophrenia
Respiratory: asthma, wheezing
Circulatory: high BP, coronary heart disease
Muscle: aches, weakness, Crohn’s dz, multiple sclerosis, rheumatoid arthritis
Bone: rickets, osteomalacia, cancer, influenza, tuberculosis
Pancreas: Type I diabetes
What are the 3 main types of non-keratinocytes found in the epidermis and are of importance?
- melanocytes: pigment producing cells from neural crest
- langerhans cells: antigen presenting dendritic cells from bone marrow
- merkel cells: mechanoreceptors, from neural crest
Melanocytes and merkel cells indistinguishable in an H& E slide (Both are found in the S. basale)
Langerhans cells are found in the S. spinosum or higher
What are the two types of pigment produced in melanocytes?
eumelanin= brown/black pheomelanin= red
Melanosomes are primarily taken up by what?
keratinocytes as opposed to melanocytes
-melanocyte synthesize the melanosomes which are transported on dendrites and phagocytosed by keratinocytes
What is significant about melanin?
-protection against UV light
What amino acid is converted to melanin?
tyrosine
Where are melanosomes degraded?
in the upper layers of the skin within lysosomes
UV light_________ the production of melanin by the secretion of melanocyte stimulating hormone (MSH) in the pituitary gland.
increases
How are melanocytes connected to the basement membrane and to each other?
hemidesmosome
melanocytes are NOT connected to each other
Why does the melanocytes look light under a light microscope?
melanocytes do not take up the melanosomes, they just synthesize it
This is depigmentation caused by auto-immune attack.
vitiligo
This is a defect in melanin synthesis.
albinism
This is caused by a deficiency in adrenal gland causing a bronzing of the skin (ACTH activation of melanocytes).
Addison disease
This is due to the defect of neural crest migration and has the characteristics of patches of white skin or hair, wideset eyes of blue or different colors, and deafness.
Waardenburg syndrome
How can we differentiate between melanoma and normal moles?
melanoma: asymmetrical, borders are uneven, multiple colors, larger than 1/4 inch, changing in size, shape, and color
How can you distinguish Langherhans cells and melanocytes if they looks very similar in an H&E stain?
they are in different layers of the epidermis
Langerhans cells contain this which are specialized endosomes for phagocytosis.
Birbeck granunles that are shaped like a tennis racket and for the epidermis.
What is the role of Langerhans cells in the immune system?
They breach the basement membrane, enter lymph vessels, and are transported to lymph nodes to activate T -cells. T lymphocytes then migrate back to skin to neutralize antigen.
important in HIV pathogenesis as langerhans cells of vaginal mucosa and foreskin take up the virus
What is Hansen’s disease?
Langerhans cells pick up the bacterium. Activated T cells then mistakenly target Schwann cells that surround peripheral nerves
Where in the epidermis are Merkel cells found?
S. basale
What is squamous cell carcinoma?
abnormal prilferation of squamous cells (keratinocytes of the S. spinosum and granulosum
the SECOND most common: significantly harder to treat
What is the most common type of skin cancer?
basal cell carcinoma: most treatable
The epidermal peg and dermal papilla (prominent in thick skin where the shear forces are the greatest) is separated by what?
basement membrane
What type of collagen is present in reticular dermis?
collagen type I
The epidermis is avascular. True or false?
True!!!
The papillary dermis compensates for this by having a rich blood supply of arteries and arterioles.
Under cold conditions, blood is sent through the arteriovenous shunt so less blood reaches the4 surface and heat is retained. Especially common in extremities.
What is anhidrotic ectodermal dysplasia?
individuals have no active sweat glands and are vulnerable to overheating, delirium, and death
Naturally aged skin loses what part of the dermis?
dermal papillae, collagen, and elastin
What is photoaged skin?
solar elastosis, thicker than aging skin but has defective collagen and elastin, promoting wrinkles and fragility, loss of suppleness.
Sun exposure greatly accelerates aging of skin.
What is the difference between UVA and UVB?
UVA penetrates into the dermis (most common in tanning places) and plays a role in graying and whitening of hair. UVB only goes through the epidermis.
This is characterized by inelastic skin which hangs in loose folds. There is excessive mobility of joints.
cutis laxia (elastolysis)
This is characterized by excessive stretching of skin and joints.
Ehlers-Danlos (hypermobility) syndrome
The hypodermis is also known as?
subcutaneous layer or superficial fascia with a rich supply of blood vessels as well and fat depositon for thermoregulation, energy storage
This causes autoimmune enlarged collagen fibers that results in hardening of skin and loss of circulation.
scleroderma
What are examples of epidermal appendages?
- eccrine sweat glands: thermoregulation
- apocrine glands
- hair follicles: sebaceous glands, arrector pili muscles (bulb of the hair follicle)
- nails
What is the function of eccrine sweat glands and where are they located?
They are located in the dermis (highest density in the palms and soles) and are activated by sympathetic nerves that secrete acetylcholine (rather than the usual norepinephrine).
What are the two types of secretory cells in eccrine sweat glands and what are their functions?
clear cells: secrete fluid sweat by transporting NaCl and water
dark cells: secrete antibacterial glycoproteins (dermicidin, defensin)
ONLY in the EM are the dark and light cells easily distinguishe; clear cells have intercellular canaliculi and contain abundant mitochondria
What is the significance of chloride channels in cystic fibrosis?
the chloride channel that should transport Cl back into the body is defective resulting in hypertonic, saltier sweat (sweat is normally hypotonic)
What is the function of the ducts in the epidermis?
- sweat is carried from eccrine gands into the epidermis where it is transported in a spiraling cavity between the keratinocytes that terminates upon the surface
- within the epidermis, the duct lose its walls and becomes a pore
THIS IS VITAL TO THERMOREGULATION
What is the function of apocrine glands and where are they found?
axillae (armpits), areola and nipples of the breast, ear canal, eyelids, some parts of the external genitalia
they are activated by sympathetic nerves that secrete norepinephrine (unlike eccrine glands) usually directly into the hair follicle
Compare eccrine and apocrine glands.
Apocrine:
- larger lumen
- smaller layer of acinar cells
- open structure generally
Eccrine:
- smaller lumen
- stratified
If apocrine glands were renamed, what should it be?
Apocrine glands release small granules into the EC space= merocrine secretion, thus they should be rename merocrine glands.
What do the secretory cells of apocrine glands become?
pheromones
Hairs are only produced in what type of skin?
THIN skin
Hair develops from the epidermis but involute into the dermis, carrying stem cell keratinocytes with them. Hair are made of keratin.
What are the two things adjacent to hair follicle?
sebaceous gland that secretes sebum and arrector pili muscles that allows the hair follicle to be raised
The hair itself is just like which layer of the epidermis, that contains virtually all keratin?
S. corneum
Dihydrotestosterone causes the involution of hair loss. True or false?
FACTS
some hair growth drugs block the conversion of testosterone to dihydrotestosterone
What is the function of sebaceous glands?
secretes sebum directly into the hair follicle (to lubricate and waterproof the skin) and is a classic example of holocrine secretion
found in the greatest number on the face and scalp
What is acne?
infected obstructed sebaceous gland
When are sebaceous glands most active?
during fetal time and puberty
What is vernix caseosa?
sebaceous glands are highly active in the fetus, and under the influence of maternal androgenic hormones form the vernix caseosa, a cheesy waterproof covering that protects the skin from amniotic fluid. After birth, the glands subside until puberty hormones activate them
What is the function of the arrector pili muscle?
they are bundles of smooth muscle associated with the hair follicle and sebaceous gland; they help expel sebum; they make hair stand on end (piloerection) under sympathetic innervation (fear, goose bumps)
Where do epidermal appendages derive from?
hair, nails, sweat glands, mammary glands derive from the epithelial-mesenchymal interactions
What are the epithelial-mesenchymal interactions?
- epidermis secretes signals that cause condensations in underlying dermis
- condensed dermis mesenchyme responds by secreting factors that cause epidermis to form regionally specific cutaneous structures
Epithelium can only make structures coded for its own species. Give an example.
Chicken epithelium can only make feathers, not fur
What are critical in establishing new epithelium (wound healing)?
keratinocyte stem cells from stratum basale and the hair root
Merkel cells have sensory receptors on them that function to do what?
appose an axon terminal that pierces the basement membrane
-signal travels along an axon back to the spinal cord
What is the functional significance of the many capillaries located immediately under the epidermis?
Thermoregulation
What is the hair shaft made up of?
keratin
