Term
| What are the functions of skin? |
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Definition
-Protection, prevents water evaporation; also from physical, chemical and biological insults and ultraviolet radiation.
-Vitamin D manufacture in the skin
- Absorption - toxins and medication can be absorbed by the skin.
-Secretion, sweat and sebum
-Organ of the sense
-Thermo-regulation |
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Term
| Where is thick skin found? |
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Definition
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Term
| Where is thin skin found? |
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Definition
| found on eyelid, medial side of arm and almost rest of the body |
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Term
| What is the basic structure of the skin? |
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Definition
-Epidermis = Outer surface
- Dermis = Corium
-The undersurface of dermis is attached to subcutaneous tissue - AKA Hypodermis or Superficial Fascia which is often being infiltrated with fat cells.
-Deep fascia - epimysium (underneath the superficial fascia).
-The epidermis is separated from dermis by a layer of basal lamina and basement membrane |
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Term
| What are the basics of the epidermis? |
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Definition
-Keratinized stratified squamous epithelium. Can be either thick or thin. Outer surface.
-Takes 25 days to 4 weeks to renew
-No vascular supply
-If too much keratin, you have dry, flaky skin (no itching, no redness)
-Bordered by basal lamina and basement membrane.
-The stratum malphigi -> spinosum + basale = mitotically active. |
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Term
| What are the five layers of the epidermis? |
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Definition
Stratum Basale
Stratum Spinosum
Stratum Granulosum
Stratum Lucidum
Stratum Corneum |
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Term
| What are the characteristics of the stratum basale? |
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Definition
-This is the only layer of the epidermis that is rapidly dividing. As the basale continues to divide, it will push older keratinocytes further up into the following layers.
-These cells are making keratin, and in form of vesicles (granules), they then pass granules to Stratum Spinosum.
-The majority of the cells in this layer are keratinocytes (i.e. cells that make and store keratin). This layer is attached to the basal lamina by hemidesmosomes.
-In this layer, the vesicles that contain keratin are laminated (or lamellate), meaning that they appear to be in concentric circles, similar to the lamellae of the osteon.
-This layer also contains melanocytes. (Only attached to the basal layer via Hemidesmosomes) |
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Term
| What are the characteristics of the stratum spinosum? |
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Definition
-This layer is called spinosum because the keratinocytes have intercellular junctions like spines. These intercellular junctions are made from the tonofibrils of desmosomes (which attach cells to cells)
-Langerhans (dendritic cells) are present in this layer as well (antigen presenting cells).
-Keratin is so hard that it must be lysed, and will not readily dissolve. Any of these layers can be diseased |
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Term
| What are the characteristics of the stratum granulosum? |
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Definition
-The keratinocytes in this layer have such dense granules that the cells look granular. In this layer the keratin is located in keratohyalin, vesicles called granules that have no limiting membrane.
-This layer is particularly impenetrable by water. The keratinocytes have desmosomes junctions and the extra cellular space contains lipids -> water proof.
-Water barrier -> lamellar granular + phospholipids + glycosamines - Keeps the humidity of the environment |
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Term
| What are the characteristics of the stratum lucidum? |
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Definition
| Keratinhyalin will be exported out of the keratinocytes in the granulosum layer;the intermediate filaments and cellular matrix form an immature keratin caled eleidin, and form of shiny layer of lucidum. The cells are dead and do not see nuclei. Thick skin has better lucidum |
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Term
| What are the characteristics of the stratum corneum? |
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Definition
| Several layers of dead flat cells w/o nuclei, filled with soft keratin; constantly sheds. The cells here are dead. (Cornocytes) |
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Term
| What are the characteristics of the basal lamina in the skin? |
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Definition
Epidermis lies on extracellular structure called basal lamina. This consists of Lamina Densa & Lamina Lucida
-Both Laminas are formed by Type IV collagen & a Glycoprotein called laminin & proteoglycan (dermatan & heparin sulfate)
-Keratinocytes and Melanocytes of the stratum basale are attached to the basal lamina by hemidesmosomes junctions |
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Term
| What are the characteristics of the basement membrane in the skin? |
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Definition
Basement Membrane - visible by light microscope by PAS (stains carbohydrates)
-Consists of two basal laminas + reticular lamina
if the basal lamina is mixed with the first layer of the dermis (loose connective tissue), it is called basement membrane.
-Basement membrane is more thick. |
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Term
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Definition
-Patches of Silvery scales of epidermis due to ↑ in proliferation of cells of stratum basale & ↓ of cycle time of epidermal cells
-Results in epidermal thickness & epidermal renewal changes to 7-10 days (opposed to 20-30 days)
-Patches occur in joints, lower part of back
-Papillomatosis = psoriasis |
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Term
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Definition
Icthyosis
↑ keratinization & causes the epidermis to be rough |
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Term
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Definition
Autoimmune disease where body forms antibodies against its own desmosomes
-Characterized by development of group of vesicles & bullae
-If in any patients the basement membrane is destroyed, there is Bullous Pemphigoid
-If the basement membrane is dissociated, the entire epidermis will be lifted up. (blisters form between epidermis and dermis)
-If the intercellular bridges between keratinocytes are destroyed, it is called pemphigus bulgaris.
-These are both autoimmune diseases. Body forms defense against its own body
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Ex: desmosome. Therefore, cells don’t stick together |
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Term
| What is the structure of the dermis? |
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Definition
-The upper part of dermis is called Papillary layer (dermal papilla) and is formed by loose connective tissue containing type III collagen.
-The lower part of dermis is called Reticular layer and is formed by dense irregular connective tissue containing type I collagen.
-These two layers can be distinguished but they blend without distinguished demarcation |
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Term
| How is the dermis vascularized? |
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Definition
Dermis has rich vascular supply
-Superficial plexus is responsible for nourishment of avascular epidermis
-Venous plexus makes numerous arteriovenous anastomoses consisting of several sphincters (metarteriols) which play a major part in thermoregulatory part of skin
-Blood is affected by ambient temperature
-If cold, metarterioles will constrict to restrict the blood flow to heart & other organs |
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Term
| Explain the CT of the dermis |
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Definition
Connective Tissue of dermis contains fibroblasts
-Direction of fibrous elements play a major role in the production of Langer or Tension line of the skin
-This is important for surgical skin incisions & for wound healing of skin |
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Term
| How is the dermis innervated? |
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Definition
Dermis is penetrated by sensory nerve fibers which lose myelin & become capsulated
-Nerve endings become capsulated at the Meissner, Pacinian, & Ruffini corpuscles
-Meissner = typically for touch; silver stain, encapsulated by Connective Tissue
-Pacinian = for pressure & vibration; located in tips of finger, around lips |
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Term
| What are the layers below the dermis? |
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Definition
A subcutaneous layer deeper to reticular dermis is hypodermis (superficial fascia)
-Loose CT with different amount of fat
-Below hypodermis is deep fascia (epimysium) |
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Term
| Whats the function of the dermis? |
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Definition
The dermis is the layer that contains the sweat glands, sebaceous glands, capsulated nerve endings, and capillary beds.
-It provides the epidermis with the nutrients and waste exchange necessary for function |
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Term
| What are the different syndromes that affect the dermis? |
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Definition
Cellulitid: dermis could be affected by all inflammatory & infective agents
Hunter’s and Hurler’s syndrome, the mucopolysaccharidosis, will affect the dermis
Ehler’s Danlos: a defect in various types of collagen, causes laxity & hyperextensibility of skin & ligament
Cutis Laxa: laxitiy of dermis |
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Term
| What are the characteristics of keratinocytes? |
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Definition
Most prevalent cells of epidermis; layers of keratinocytes are the major factor for thickness of skin.
Keratinocytes are connected by desmosomes, and attach to the basal lamina by hemidesmosomes.
Keratinocytes in the Stratum Spinosum are also connected by intercellular bridges in addition to desmosomes.
Stains basophilic because of the number and activity of ribosomes |
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Term
| What are the characteristics of melanocytes? |
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Definition
Only located on the basal layer. Will sometimes move to the dermis. If it is in the upper region above stratum basale it is not a melanocyte.
In slides, appears to have lacunae, that is sometimes filled with melanin.
Melanocytes have hemidesmosomes that anchor them to the basal lamina
They are not attached to adjacent keratinocytes by desmosomes
Melanocytes come from neural crest cells
Melanocytes produce and secrete a pigment called melanin. Certain parts of the body have more Melanocytes (eg Scrotum, skin of the forehead and cheeks). There are melanocytes in every race, the melanocytes just make more melanin in darker skin colors.
They have processes that pass over the neighboring keratinocytes.
If melanocytes become tiny, hypofunction occurs. Will have a white blotchy area of the skin. |
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Term
| What are the characteristics of melanin? |
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Definition
Melanin is derived from Tyrosine. Formed through packaging process of the ER and Golgi. Will see that Tyrosine, under Tyrosinase, will break down into DOPA. Will change into Melanin through other biochemical changes.
Melanin granules are called melanosomes. It is like a laminated structure, which has black granule, and should be oval
Melanosomes are secreted through cytocrine secretion. The melanin pigments will enter the keratinocytes and occupy their supranuclear region. This is to protect the DNA and cell from UV radiation, which causes mutation in DNA.
-In red-haired the pigment is called pheomelanin, and the melanosomes are round.
-In porphyria, the granules will be in different colors and shapes |
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Term
| What are the clinical diseases assoc.with melanocytes and melanin? |
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Definition
ADDISON DISEASE, a hypofunction of adrenal gland and increase ACTH and causes hyperpigmentation of the skin. This might very well be due to stimulation of melanocyte stimulating factor
Tanning: due to rapid production of melanin in the melanocytes. Chronic exposure causes tumors to skin
Albinism: the absence of Tyrosinase activity & melanin can not be found in melanocytes
Vitiligo: depigmented skin, due to absence or hypofunction of melanocytes
Melasma or Chloasma: hyperpigmentation of skin; specially face, during pregnancy due to hormonal changes |
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Term
| What are the characteristics of langerhans cells? |
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Definition
Also called dendritic cells due to their dendritic like processes. Are a part of the immune system
Have rod like membrane limited granules called Birbeck or Vermiform in the cytoplasm
When a toxin enters the body, Dendritic cells will present the toxin to the T-Cells. It is an antigen recognizing cell (APC), a type of lymphocyte.
Processes are similar in structure to the melanocytes but in a different location.
Langerhans cells are in the stratum spinosum |
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Term
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Definition
Mechanoreceptors
Serve as a touch receptor, located in the epidermal layer.
Contains free nerve endings that are unmyelinated axons that serve as the transporter of the sensory stimulus |
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Term
| What's the cell composition of the epidermis and dermis? |
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Definition
96% Keratinocytes
2-3% Melanocytes
1% Langerhans Cells/Merkel Cells |
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Term
| What is the location of hair? |
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Definition
| Whole body surface is covered by hair except thick skin of palm & sole, lateral part of feet, glans of penis & clitoris, inner surface of prepuce & labia minoria |
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Term
| What are the types of hair? |
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Definition
Lanugo Hair - last two or three months of fetal life, the fetus is covered by fine hairs called languo hair
Terminal Hair - languo hair is replaced by a rather coarser hair |
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Term
| What's the structure of a hair cell? |
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Definition
Made up of three components: Follicles, Bulb, and Papillae
Follicle
-Sensitive to Pull
-Hair follicle causes an invagination of the epidermal layer into the dermal layer. There is a layer of epidermal cells and basement membrane that will follow the hair follicle (i.e. papillae) along invagination into the dermal layer.
-Keratin of hair is Trichohyalin & is a hard keratin, its production is intermittent & its production is by cells of hair follicle
Bulb
-Bulb is the lower part of the hair follicle.
-Bulb will invaginate upon itself and is called hair papilla.
Papilla
-The part of the hair bulb that invaginates into itself is termed the papilla.
-The cells on the top of the papilla will form the hair cells.
-The papilla layer is germinating. This part of the hair cell contains the blood vessels and nerve endings. Hair is sensitive to pulling out, but not cutting because there are only nerve endings in the root |
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Term
| What are the layers of hair? |
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Definition
Medulla
-Inner layer of cells that make up the hair follicles.
-The medulla layer is pale and contains vacuolated cells. These cells contain very little keratin.
Cortex
-The next layer of cells, limited by one layer of cuticle cells.
-synthesize most of trachohyalin
Cuticle
-This is the part of the hair that erupts from the epidermis.
-Melanocytes that invaginated with the basement membrane deposit melanin granules into the cuticle cells, giving them their pigment.
-The keratin of the skin is soft keratin; the hair keratin is hard keratin. |
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Term
| What are the surrounding layers of the hair? |
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Definition
Inner Root Sheath
-This layer consists of several sub-layers which include: Huxley’s and Henle’s cells
-This layer only surrounds the bulb of the hair cell.
External Root Sheath
-This layer follows the hair follicles and is continuous with the epidermis.
Glassy Membrane (Basement Membrane)
-This layer is the invagination portion of the basement membrane that followed the follicle into the dermal layer |
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Term
| What are the types of hair growth? |
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Definition
Anagen
-900 - 1000 days
-Lots of hair growth
Catagen
-Cell will under go catagen at any given time
-100 days
Telogen
-Resting stage |
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Term
| What is telogen affluvium? |
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Definition
Telogen Affluvium, an infectious disease
-Hair will be lost due to infection
-Easiest stage to cure |
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Term
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Definition
Alopecia (Hair loss)
Hair loss in men due to androgen secretion. Male pattern alopecia |
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Term
| What are sebaceous glands? |
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Definition
Assoc. structure for hairs
Holocrine gland - completely lyses after secretion
Secretion is accompanied by protoplasmic destruction
Product is SEBUM, a mixture of lipid, cholesterol, & TG
Function not under nerve control
Sebaceous gland is inactive until puberty
Function of sebaceous gland is under hormonal influence |
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Term
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Definition
Clinical Correlate - Acne Vlugaris
Happens mostly in the face, chest, back, and exposed layers
Inflammation of sebaceous gland leads to obstruction and blockage
Gland can not be drained and will swell
Skin will be greasy
Under effect of androgens
Acne = sebaceous glands are hyperactive |
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Term
| What are the arrector pili muscles? |
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Definition
Bundle of Smooth Muscle Fibers extended between the papillary dermis & CT sheath of hair follicle
Cause erection & compression of sebaceous gland content into follicular canal
Muscles are innervated by ANS |
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Term
| What are the characteristics of sweat glands? |
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Definition
Located deep in the dermis
Coiled tubular gland, simple cuboidal
Lined by 2 layers of cuboidal epithelium called Light & Dark cells
Clear Cells: located towards the lumen on a basement membrane
Between the cells & basement membrane there are star shape cells called Myoepithelial cells that have pulsatile contraction to expel the sweat out of coiled portion
Spiral duct to the surface
The secretory cells become stratified cuboidal
Have no myoepithelial cells
two types - eccrine and apocrine |
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Term
| What are the characteristics of eccrine sweat glands? |
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Definition
Merocrine = no damage after secretion
Is on the whole surface of the body
Start function at early life
Secrete fluids (Na, Cl, K)
Does not smell
Under cholinergic effect |
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Term
| What are the characteristics of apocrine sweat glands? |
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Definition
Only on special parts
Axilla (armpits), anogenital regions, areola of the nipple
Start function at puberty
Contain phospholipids and lipids
Has smell
Under andrenergic effect
Partial destruction of cell (has some protoplasmic secretions)
Lumen will become larger, and cells will become smaller.
If skin is from palm or forearm, they are not apocrine sweat glands |
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Term
| What are characteristics of the nail? |
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Definition
The nail plate is the whole thing
The nail body is the visible portion made of keratin
The lighter, crescent shaped region of the nail body is lunula
The skin that covers the lunula is a cuticle which is a good protective agent for the nail.
Eponychium = fold of skin over the nail
Hyponychium is the part of the epithelium under the nail
If one pushes the nail, color will leave and come back - not in anemia |
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Term
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Definition
The area where the nail will be generated
If damage the matrix, the nail will not grow back
Psoriasis affects the nail very badly |
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Term
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Definition
| Paronychia: Bacteria entering & puss collection in the nail folds |
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Term
| What are the types of hair loss? |
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Definition
Male pattern alopecia is due to androgenic effects of male hormones
Alopecia areata is discoid patches of hair loss
Alopecia totalis is total loss of hair of the scalp
Trachtilomania is loss of hair due to traction or trauma |
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