Where are the highest concentrations of 7-dehydrocholesterol found in the skin?
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In the epidermal layer of skin, specifically in the stratum basale and stratum spinosum.
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Where are the highest concentrations of 7-dehydrocholesterol found in the skin?
In the epidermal layer of skin, specifically in the stratum basale and stratum spinosum.
How does the destruction of melanocytes in vitiligo typically occur?
The destruction is most likely a slow process resulting in a progressive decrease of melanocytes.
What are the cells in the stratum spinosum commonly known as, due to their appearance?
Prickle cells.
What converts 7-dehydrocholesterol to vitamin D3 (Cholecalciferol)?
Sunlight.
What is vitiligo?
Vitiligo is an acquired pigmentary disorder of the skin characterized by circumscribed, depigmented macules and patches.
Where are several nerves (N) present in relation to the Pacinian corpuscle?
Adjacent to the corpuscle.
What type of epithelium composes the epidermis?
Stratified squamous keratinized epithelium.
What are the primary protective functions of the skin?
The skin acts as a barrier that protects against physical, chemical, and biologic agents in the external environment.
What is a melanocyte and where is it located?
A melanocyte is a cell that produces melanin and is located in the stratum basale and stratum spinosum of the epidermis.
Where is the stratum lucidum typically found?
Only in thick skin.
Where are Meissner’s corpuscles located?
Residing within the dermal papillae.
Name three less abundant cell types in the epidermis.
Melanocytes, Langerhans cells, and Merkel cells.
What is the function of the cells in the nail matrix?
They function in the growth of the nail.
Which type of disorders is vitiligo frequently associated with?
Vitiligo is frequently associated with disorders of autoimmune origin, with thyroid abnormalities being the most common.
What is the main type of cell found in the epidermis?
Keratinocytes.
How are the supporting cells of Meissner’s corpuscles oriented?
Approximately at right angles to the long axis of the corpuscle.
What can cause leukoderma?
Leukoderma can be caused by absent melanocytes or melanocytes that are present but unable to synthesize melanin or transfer it to the keratinocytes.
What is the glassy membrane in a hair follicle?
A thickened basement membrane that forms the outer boundary of the external root sheath (ERS).
How do keratinocytes acquire melanosomes from melanocytes?
Keratinocytes phagocytose the tips of the melanocyte processes containing melanosomes, a process known as pigment donation.
What type of glands are apocrine glands associated with?
Hair follicles.
What are the layers of the internal root sheath of a hair follicle?
Henle’s layer, Huxley’s layer, and the cuticle of the internal root sheath.
Where are apocrine glands located?
In the axilla, areola, nipple of the mammary gland, skin around the anus, and external genitalia.
What is 7-dehydrocholesterol synthesized from?
Cholesterol.
What appearance does the stratum lucidum often have under a light microscope? why?
A refractile appearance and may stain poorly because of eleidin
What are the components of the hair shaft?
Medulla, cortex, and the cuticle of the hair shaft.
When do apocrine glands become functional?
At puberty.
How does the skin contribute to the immune system?
The skin provides immunologic information obtained during antigen processing to the appropriate effector cells in the lymphatic tissue.
What enzyme is responsible for the oxidation of tyrosine to 3,4-dihydroxyphenylalanine (DOPA)?
Tyrosinase.
What structural feature gives the stratum spinosum its name?
The numerous cytoplasmic processes or spines, which are desmosomes.
What is leukoderma?
Leukoderma is the visible result of loss of epidermal melanin.
What is found under the nail and contributes to its growth?
A layer of epithelium, the proximal portion of which is referred to as the nail matrix (NM).
What are the characteristics of thin skin?
Possesses a much thinner epidermis and contains hair follicles in most locations.
What does the 'D' in the ABCDE rule for melanoma stand for?
Diameter of skin lesion; moles greater than 6 mm are more likely to be suspicious.
What is the role of melanosomes in the epidermis?
Melanosomes, which are contained in the dendritic processes of melanocytes, are transferred to keratinocytes, providing pigment to the skin.
What type of cells primarily make up the stratum spinosum?
Keratinocytes.
What is albinism?
Albinism results in a complete lack of pigmentation in skin, hair, and eyes.
What happens to the shape of the cells in the most superficial part of the stratum spinosum?
The shape of the cells becomes squamous.
What role do Langerhans cells play in the epidermis?
Langerhans cells are antigen-presenting cells.
Why is the skin on the back classified as thin skin?
Because it has a thick dermis but a thin epidermis.
What type of cells arise from the stem cells in the stratum basale?
New cells arise by mitotic division.
How can melanocytes in the stratum basale be identified?
Seen as cells with clear halo.
What is the function of melanocytes in the epidermis?
Melanocytes produce pigment.
What do two keratinocytes display near the plasma membrane closest to the surface?
Lamellar bodies.
What type of cells are found in the stratum basale (stratum germinativum)?
Columnar or cuboidal cells.
What does the 'B' in the ABCDE rule for melanoma stand for?
Border of the lesion is irregular.
Where are Merkel's cells located?
In the stratum basale.
What are the two layers of the dermis?
The papillary layer (PL) and the reticular layer (RL).
What do keratinocytes in the stratum granulosum contain?
Numerous keratohyalin granules.
Where does the duct of an apocrine sweat gland open?
Into the follicle canal.
What product is secreted by eccrine sweat glands?
Sweat.
What does the hypodermis contain and where is it located?
Contains variable amounts of adipose tissue, lies deep to the dermis.
Where is the secretory segment of an eccrine sweat gland located?
Deep in the dermis or in the upper part of the hypodermis.
What type of cells are Langerhans' cells?
Antigen-presenting cells in the stratum spinosum.
What structure is exhibited by one keratinocyte in the EM image?
A keratohyalin granule (KG).
How are cells in the stratum basale attached to the basal lamina?
By hemidesmosomes.
What is the role of tyrosinase in melanin production?
Tyrosinase oxidizes tyrosine to 3,4-dihydroxyphenylalanine (DOPA), which is then transformed into melanin.
What do spinous and granular cells synthesize?
A heterogeneous mixture of probarrier lipids and lipid-processing enzymes.
From what are melanocytes derived?
Melanocytes are derived from neural crest cells.
What is the function of Langerhans’ cells in the skin?
Langerhans’ cells function as antigen-presenting cells of the immune system in the initiation of cutaneous hypersensitivity reactions.
Do melanocytes form desmosomes with neighboring keratinocytes?
No, melanocytes do not form desmosomes with neighboring keratinocytes.
What proteins are found in keratohyalin granules?
Cystine-rich and histidine-rich proteins, which are precursors of filaggrin.
What is the epidermis composed of and from what is it derived?
Keratinized stratified squamous epithelium, derived from ectoderm.
What are the epidermal derivatives (epithelial skin appendages) of the skin?
Hair follicle and hair, sweat (sudoriferous) glands, sebaceous glands, nails, and mammary glands.
What type of epithelium is found in the duct segment of an eccrine sweat gland?
Stratified cuboidal epithelium.
What happens after Langerhans' cells process and display antigens?
They migrate from the epidermis to a regional lymph node to interact with T lymphocytes.
What does the 'C' in the ABCDE rule for melanoma stand for?
Color variations; melanomas usually have multiple colors.
What does the 'E' in the ABCDE rule for melanoma stand for?
Evolving: change in mole appearance.
What type of cell is a melanocyte and where is it located?
A melanocyte is a dendritic cell scattered among the basal cells of the stratum basale.
How are the contents of lamellar bodies secreted?
By exocytosis into the intercellular spaces between the stratum granulosum and stratum corneum.
What is another name for the stratum basale and why?
Stratum germinativum, because of the presence of mitotically active cells, the stem cells of the epidermis.
What is the function of filaggrin in the stratum corneum?
Filaggrin aggregates the keratin filaments in the cells of the stratum corneum.
What is a distinctive feature of eccrine sweat glands regarding their association with hair follicles?
Eccrine sweat glands are independent structures, not associated with hair follicles.
Where does the short duct of the sebaceous gland open?
Into the infundibulum of a hair follicle canal.
What distinctive feature can be seen in the cytoplasm of Langerhans' cells under electron microscopy?
Tennis racket-shaped Birbeck granules.
What is the function of Merkel cells in the epidermis?
Merkel cells are tactile epithelial cells.
What is the primary function of the stratum basale?
Provides for epidermal cell renewal.
How are basal cells connected to each other and to the supra-basal keratinocytes?
By desmosomes.
What are the characteristics of Merkel cell carcinoma (MCC)?
It is a rare but highly aggressive type of skin cancer characterized by painless, firm, non-tender, shiny, rapidly growing nodules.
What can the destruction of the epidermal water barrier over large areas lead to?
Life-threatening loss of fluid from the body, as seen in severe burns.
What type of sensory receptor is found in the dermal papilla?
Meissner’s corpuscle
Which layer of the epidermis is present only in thick skin?
Stratum lucidum.
What is the nature of the secretion produced by apocrine sweat glands?
A serous secretion containing pheromones.
What are mammary glands considered to be?
Modified sweat glands.
How can Langerhans' cells be identified?
Using antibody against CD1a molecules.
What does the 'A' in the ABCDE rule for melanoma stand for?
Asymmetrical shape of skin lesion.
What do keratinocytes in the stratum spinosum begin to produce?
Keratohyalin granules and membrane-bounded lamellar bodies.
What type of epithelium composes the epidermis?
Stratified squamous epithelium.
How do melanocytes appear in routine H&E slides?
Melanocytes are seen in the stratum basale with elongated nuclei surrounded by a clear cytoplasm. “halo” appearence
What is an example of a cutaneous hypersensitivity reaction involving Langerhans’ cells?
Contact allergic dermatitis, such as poison ivy.
Which sensory receptor is responsible for detecting fine touch and is found in the dermal papilla?
Meissner’s corpuscle
Where does the duct of an eccrine sweat gland open?
On the surface of the skin.
What is the dermis composed of and from what is it derived?
Connective tissue, derived from mesoderm.
What role do Langerhans' cells play in patients with HIV/AIDS?
They contain the HIV virus in their cytoplasm and may serve as a reservoir for the virus.
What endocrine functions does the skin perform?
The skin performs endocrine functions by secreting hormones, cytokines, and growth factors, and converting precursor molecules into hormonally active molecules such as vitamin D3.
What do basal cells in the stratum basale contain that is transferred from neighboring melanocytes?
Melanin.
From which cells do individual melanoma cells originate?
Melanocytes.
What are the three regions of a hair follicle?
Infundibulum, Isthmus, and Inferior segment.
Where does the infundibulum region of the hair follicle extend?
From the surface opening to the level of the opening of its sebaceous gland.
What is the function of the dermal papilla in the inferior segment of the hair follicle?
It is a tuft of vascularized loose connective tissue that invaginates the base of the bulb.
What is the association between filaggrin gene mutations and atopic dermatitis?
About 50% of all severe cases of atopic dermatitis are associated with at least one mutated filaggrin gene.
Do Langerhans' cells form desmosomes with keratinocytes?
No, they do not form desmosomes with keratinocytes.
What happens in the hereditary condition known as albinism?
In albinism, there is a lack of tyrosinase, preventing the transformation of tyrosine into DOPA and subsequently into melanin, leading to a reduction or absence of melanin pigment.
What characterizes albinism?
Albinism is characterized by a congenital reduction or absence of melanin pigment due to inherited abnormalities in melanin synthesis.
What type of tissue makes up the papillary layer?
Loose connective tissue.
What type of tissue is found in the reticular layer?
Dense irregular connective tissue.
Where is the reticular layer located?
Deep to the papillary layer.
What does the isthmus region of the hair follicle contain?
It extends from the infundibulum to the level of insertion of the arrector pili muscle and contains epidermal stem cells in the follicular bulge.
What is the role of the arrector pili muscle?
To contract and pull hair shafts to a more erect position, usually when it is cold, to trap a layer of warm air near the skin.
Which sensory receptor detects light touch and texture and is located in the basal epidermal layer?
Merkel’s corpuscles
What is the possible function of the pheromones in the secretion of apocrine sweat glands in humans?
They may act as a sex attractant.
What are the two segments of an eccrine sweat gland?
The secretory segment and the duct segment.
What is the most serious form of skin cancer?
Malignant melanoma.
Where is the papillary layer located?
Immediately underneath the epidermis.
Which sensory receptor is located in the deep layers of the dermis?
Ruffini’s corpuscle
Which sensory receptor is associated with detecting deep pressure and vibration?
Pacinian corpuscle
What type of sensory receptor is involved in detecting pain and temperature?
Epidermal free endings
What composes the stratum corneum?
Keratinized cells.
What type of gland are sebaceous glands?
Holocrine type of gland.
Where are myoepithelial cells located in the eccrine sweat gland, and what is their function?
They are located at the basal aspect of the secretory segment and are responsible for the expulsion of sweat from the gland.
what is the acronym for remembering layers of epidermis from deepest to most superficial ?
Basic Starbucks grabs ladies coins
Basale
Spinosum
granulosum
lucidum
corneum
What is the general cause of depigmentation in vitiligo?
The absence of functional melanocytes in vitiligo skin, owing to their destruction. AUTOIMMUNE
