Summary
chapter 18 skin Junqueira's Basic Histology summary
chapter 18 skin Junqueira's Basic Histology summary
[Show more]
Connected book
Book Title:
Author(s):
- Edition:
- ISBN:
- Edition:
Content preview
Skin Epidermis:
o Mainly stratified squamous keratinized epithelium composed of cells called keratinocytes
o Less abundant cells: melanocytes, antigen-presenting Langerhans cells, and Merkel cells.
o Receives oxygen by diffusion from dermis
o From the dermis, the epidermis consists of 4 layers of keratinocytes (5 in thick skin):
Basal layer (Stratum basale):
Single layer of basophilic cuboidal or columnar cells
Joined by hemidesmosomes to the basal lamina and desmosomes bind them to
lateral and upper surfaces.
Intense mitotic activity
Human epidermis is renewed every 15 to 30 days
Has cytoskeletal keratin which are intermediate filaments where cells move
upward on
Spinous layer (stratum spinosum)
Thickest layer
Synthesizes keratins
Keratins assemble to form bundles called tonofibrils that converge and terminate
at the desmosomes holding the cell layers together.
Granular layer (stratum granulosum)
3 to 5 layers of flattened cells undergoing terminal differentiation process of
keratinization.
Cytoplasm is filled with basophilic masses called keratohyaline granules.
o These are dense masses of filaggrin and other proteins associated with
keratins of tonofibrils.
Lamellar granules (derived from Golgi) have various lipids that exocytose these
lipids producing a lipid-rich impermeable layer around the cells.
Stratum Lucidium:
Found ONLY in thick skin
Contains thin layer of eosinophilic keratinocytes held together by desmosomes.
No nuclei or cytoplasm. Just keratin filaments in cytoplasm.
, Stratum Corneum:
15 to 20 layers of squamous keratinized cells filled with keratin filaments.
Has squames which are fully keratinized cells which are continuously shed at the
epidermal surface.
Melanocytes:
o Skin color depends on keratinocytes’ content of melanin and carotene and the number of blood
vessels in the dermis.
o Eumelanins are brown or black pigments produced by the melanocyte.
Melanocytes are found in basal layer and in hair follicles.
o Pheomelanin is a similar pigment found in red hair
o First step in melanin synthesis is catalyzed by tyrosinase, a transmembrane enzyme in golgi-
derived vesicles.
Tyrosinase converts tyrosine into 3,4-dihydroxyphenylalanine (DOPA), which is then
further transformed into the different forms of melanin.
o Melanosomes (granules of accumulated melanin pigments) are transported via kinesin to the
tips of cytoplasmic extensions.
Neighboring keratinocytes phagocytose the tips of these extensions, take in the
melanosomes and transport them by dynein toward their nuclei.
Melanocytes produce melanosomes but the keratinocytes are the melanin depot and
contain more of this pigment than the cells that make it.
o Epidermal-melanin unit = 1 melanocyte + the keratinocytes into which it transfers
melanosomes.
Langerhans cells:
o They are antigen-presenting cells
o Represent 2% to 8% of epidermal cells
Merkel cells:
o Also called epithelial tactile cells
o They are sensitive mechanoreceptors essential for light touch sensation
o Abundant in highly sensitive skin like fingertips and bases of hair follicles
o Has no melanosomes
Dermis:
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller OGN. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for CA$11.12. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
50843 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy study notes for 14 years now