Lecture 8: The Integument Flashcards
The skin creates what vitamin?
Vit D3
What are the layers of the skin?
Epidermis
Dermis
Hypodermis is subcutaneous fascia
What is the hypodermis?
Subcutaneous fascia
What kind of cells is the epidermis?
Keratonized stratified squamous epithelium
How many layers does the epidermis have?
The epidermis will have 4-5 layers of stratum, depending on if we are talking about thin or thick skin.
What are the layers of the epidermis?
- Stratum corneus- most superficial
- Stratum lucidum (only seen in thick skin)
- Stratum granulosum
- Stratum spinosum
- Stratum basale (deepest layer)
What layer of the skin is only found in THICK skin?
Stratum lucidum
What layer of the skin is the most superficial?
Stratum corneum.
The epidermis is made up of what cells?
- Keratinocytes
- Melanocytes
- Merkel cells
- Langerhan cells
What are the two types of skin?
- Thick skin
2. Thin skin
Thick skin
Thick skin is found on your palms and soles. It has 5 layers (includes the stratum lucidum).
Has fingerprints
Thin skin
Thin skin is found everywhere on your body except the palms and soles. It has 4 layers (not the stratum lucidum).
Instead of fingerprints, it has glands and hair follicles.
How many uM is thick skin?
400-1400uM
How many uM is thin skin?
75-150uM
Stratum Basale
Stratum basale is a single layer of mitotically active keratinocytes with stem cells interspred. Thus, the cells we lose are replaced by cells from here.
Cells are a single layer of cuboidal/columnar and bound apically by desmosomes. Basally, they are bound by hemidesmosomes.
What cell type is the stratum basale?
A single layer of cuboidal/columnar with keratinocytes & stem cells that are mitotically active
How is the stratum basale bound apically?
Desmosomes
How is the stratum basale bound basally?
Hemidesmosomes.
Stratum spinosum
Above the stratum basale.
The stratum spinosum is several layers thick with [polyhedral keratinocytes with spiny processes].
The stratum spinosum is the layer that thickens to form calluses and corns
What layer thickens to form calluses and corns?
Stratum spinosum
Stratum granulosum
The stratum granulosum is the thickest layer of the NON-KERATINIZED portion of the epidermis. It is irregularly shaped and can vary in size.
In this layer, the keratinocytes have keratohyalin granules.
What are keratohyalin granules
Granules released from the keratinocytes in the stratum granulosum layer.
They are [basophillic, histidine and cystine-rich] and the precursor to filigrin.
Stratum corneum
The most superficial layer of the epithelium. Keratinocytes here are anucleate and lost organelles so that they can fill up with MATURE keratin and form a water barrier.
This is the layer of cells we lose.
How many layers is the stratum corneum in THICK skin?
15-40.
How many layers is the stratum corneum in THIN skin?
10-20
Stratum lucidum
Stratum lucidum is a subdivision of the stratum corneum. and is only seen in thick skin. It has no organelles or nuclei because keratinocytes have shed them.
It stains poorly; looking translucent.
What are keratinocytes?
Keratinocytes are the main cell in the epidermis (85%).
They make keratin and form a water barrier by expelling all of their contents and filling with keratin. This processes is called cornification.
They also undergo desquamation.
When are keratinocytes fully cornified?
at the stratum corneum
What is desquamation
When keratinocytes are lost or shed.
Do keratinocytes change as we move up through the layers?
Yes.
As we become more superficial, there is an increase in keratin as a whole.
Keratinocytes in the basal cell
Keratinocytes in the basal layer begin to make keratin and group them into bundles called tonofibrils
Keratinocytes in the spinous cells
Keratinocytes in the spinal layer continue to make keratin and begin to make
[keratohyalin granules and glycolipid-containing lamellar bodies]
Importance of the glycolipid-containing lamellae bodies.
They help form the water barrier.
Keratinocytes in the granular layer
- Keratinocytes will then expel the lamellar bodies to help create a water barrier between the [stratum corneum and stratum granulosum].
- Keratinocytes have keratohyalin granules with filaggrin..
- Keratinocytes now become cornified (losing nucleus and organelles)
What is filiaggrin?
Filaggrin promotes the aggregation of tonofibrils to begin to make keratin filaments.
Keratination and desquamation are ____ dependent
pH. Thus, as the layers become more superficial they become more ACIDIC.
How do we replace epidermal cells?
Stem cells in stratum basale will divide and move upwards into keratinized cells.
Melanocytes
- Where are they derived from?
- Where are they located?
- What do they do?
Neural crest
Stratum basale
ONE melanocyte will create melanin and transfer it to 36 keratinocytes
What is melanin
a pigment protein that protects the nuclei from UV radiation
Melanocytes
One melanocytes will create melanin and transfer it to 36 keratinocytes. They are derived from neural crest and located in the stratum basale layer of the epidermis.
How is melanin made?
[Tyrosine] is oxidized into [DOPA] via tyrosinase, an enzyme that is sensitive to UV.
[DOPA] is then polymerized into [melanin].
How is tyrosinase activated?
UV.
Thus, in sunlight; Tyrosine–> DOPA and then DOPA is polymerized into melanin.
Where is melanin made?
The reactions begin in premelanosomes.
As more melanin is made, they will become melanosomes. Melanosomes will extend into cells and transfer the melanin to keratinocytes in a process called pigment donation.
Difference between premelanosomes.
Melanin production begins in premelanosomes.
Once the melanin is made, it will become a melanosome, which will then extend into the cell and donate the melanin to keratinocytes in a process called pigment donation.
How is melanin transferred from melanosomes to keratinocytes?
pigment donation (PHAGOCYTosis)
Langerhan cells
Langerhan cells are antigen-presenting cells (APC) that defend against pathogens. They are derived from monocytes.
When an antigen is detected, langerhan cells will phagocytize it present it on the surface. They will then migrate to a lymph node and activate T-lymphocytes.
What part of the epithelium are langerhan cells found?
Stratum spinosum.
What are merkel cells?
Merkel cells are cells in the epidermis that give us cutaneous sensation in our fingertips and body by associating with a nerve ending.
Where are merkel cells found?
Stratum basale
Merkel cell carcinoma
MCC is rare but aggressive skin cancer where merkel cells undergo uncontrolled proliferation.
Where is the dermis-epidermal junction
Dermis is located underneath the stratum basale.
What is the dermal-epidermal junction?
Contact of the dermis and epidermis.
It is wavy, except in thin skin. These waves are due to projections called dermal papillae, which extend into the epidermis. Epidermis also sends protrusions called epidermal (rete) ridges, which tie them together
Waves of the dermal-epidermal junction are due to what?
Projections from the dermis called dermal papillae and extensions from the epidermis called epidermal (rete) ridges.
Is the dermal-epidermal junction one size?
No. It increases in size where there is mechanical stress.
What kind of junctions help the dermal-epidermal junction?
Hemidesmosomes and focal adhesions.
Will the skin have a bigger dermal-epidermal junction on your hands or back?
Hands because there is more mechanical stress there.
What kind of tissue is the dermis?
Dense- irregular CT
What are the 2 layers of the dermis?
- Papillary layer
2. Reticular layer
Papillary layer of the dermis
The papillary layer is the most superficial layer of the dermis, directly beneath the epidermis. Includes the dermal papilla and dermal ridges.
It is [loose CT] that has [thinner collagen and elastic fibers]. Also has [vasculature] and [nerve endings]
Reticular layer of the skin
Sits below the papillary layer.
- [dense irregular CT] and less cellular.
-type 1 collagen and elastic fibers
-Collagen forms regular lines of tension called
Langer lines
In the reticular layer, collagen forms regular lines of tension called what?
Langer lines.
What kind of cuts are best for c-section?
horizontal so that they can follow the langer lines.
They’re important for surgery.
Hypodermis
Hypodermis is subcutaneous fascia made up of adipose tissue (panniculus adiposus) that varies in thickness.
It stores NRG and insulates and has arrector pili muscles that help hair stand up.
Is the hypodermis all one thickness?
No, it depends on the body region
What part of the skin has errector pilli muscles that help hair stand?
Hypodermis
Meissner Corpuscle purpose
Meissner Corpuscles are touch receptors that are sensitive to low-frequency stimuli (braile)
What to meisner corpuscle look like
Tapered cylinders perpendicular to the surface of the skin
Where are meissner corpuscle located
Dermal papillae, below the epidermis
Pacinian Corpuscle purpose
detect [pressure and vibration] via a myelinated nerve ending in the middle.
Pacinian corpuscle shape
large, oval, onion
Where are pacinian corpuscles found
Deep dermis and hypodermis
What is merocrine (eccrine) secretion?
The secretion is delivered via membrane bound vesicles to the surface. Contents are released via exocytosis.
What is holocrine secretion?
Cells will fill up with secretion and then undergo apoptosis, releasing the contents
What is apocrine secretion?
The apical portion of a cell pinches off and delivers the secretion.
surrounded by cytoplasm and plasma membrane
Where are sebaceous glands found?
Sabeceous glands are found in the hair follicles on your face and scalp.
What do sebaceous glands make?
Sebum (a lipid mixture) and release it via holocrine secretion.
this lubricates and softens our skin and makes it waterpoof
How is sebum released?
Holocrine secretion. Goes into the infundibulum (hair follicle) and forms a [pilosebaceous canal].
Another word for sweat glands
sudoriferous glands
What kind of sweat glands do we have
- Eccrine (merocrine) sweat glands
2. Apocrine sweat gland
Where are (merrocrine) eccrine sweat glands found?
everywhere on the body except lips and external genitelia
Where are apocrine sweat glands found?
These are activated during puberty.
found in axilla, nipple, external genitilia
ear canal
Eccrine sweat gland purpose
thermoregulation.
____________ cells help to expel secretions in eccrine sweat glands
myoepithelial
Apocrine sweat glands use ________ secretion
merocrine secretion to secrete proteins, carbs and ammonia that is odorless until mixed with bacteria
____________ cells help to expel secretions in apocrine sweat glands
myoepithelial
Follicular bulge of hair follicle
near where the arrector pili muscle is located and contains the epidermal stem cells
hair matrix
matrix cells that divide and differential for hair to grow
infundibulum of hair
extends from the opening of the surface to opening of the sebaceous gland
lunula
white near nail matrix
nail root
most proximal region that covers the nail matrix
nail matrix
where stem cells divide and form keratinocytes.
nails are what type of cells`
highly keratininized cells on epidermis (nail bed)
what is the epidermal-melanin unit
one melanocyte associates with 36 keratinocytes
