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Dermis/Skin

Skin Study Guide

QuestionAnswer
Describe the epidermis, dermis and hypodermis Epidermis: Most superficial. Dermis: Connective with hair follicles, blood vessels etc Mostly eosinophillic because of collagen. hypodermis: Adipose tissue, blood supply and certain immune components
What are the two main elements of the dermis? Collagen and elastic fibers
Describe the structure of the collagen Series of interlinked strands that have no particular orientation that we can crosslink by enzymes and create what is effectively and insoluble matrix. This matrix gives the skin most of its strength and toughness
What is Cutis Laxis? The elastic fibers do not form correctly and you can pull the skin to extreme regions and it won't retract back to its normal fashion
Name the layers of the skin The basal layer, spinous layer, granular layer, cornified layer on top
Describe the basal epithelium Mixture of basal keratinocytes and melanocytes. Germinal layer of skin. They are epithelial cells, stuck together, they form junctions
Describe how the cells of the basal epithelium are self-regulating? Respond to transforming growth factor alpha (TGF-a) that are autocrine factors. Also respond to factors made by fibroblasts such as keratinocyte growth factor (KGF)
Describe IGF-1 receptor This is a receptor that is absolutely necessary for the growth of keratinocyte
What are the main functions of basal keratinocytes? Capacity for growth and for setting up an adhesion interface between the cells on top of the dermis
What are keratin filaments composed of? Make up keratinocytes. Composed of 2 different polypeptide chains. (Acidic and basic). The acidic and basic chains come together and make helical structures (characteristic 10nm filaments)
Describe spinous keratinocyte At the transition from basal keratinocytes, Spinous are made in much higher abundance
Name the two keratins made in the basal layer K5 and K14
What are the high molecular keratins? K1 and K10. Tranisition to the synthesis of K1 or K10 in spinous keratinocytes and no synthesis at all by basal keratinocytes
What do desmoglein and desmocollin do? Form heterodimers that set up adhesion between cells
What is pemphigus? Autoimmune disease that makes antibodies to desmosomes and skin blisters appear and fall apart.
Describe Dsg 3 and Dsg 1 Dsg 3: More heavily synthesized by basal keratinocytes and becomes less expressed as differentiation occurs. Dsg 1: Increase in expression as differentiation occurs.
What antibody tends to produce pemphigus vulgaris? Antibody to Dsg3
What antibody tends to produce pemphigus foliaceus? Antibody to Dsg 1
Which pemphigus is more lethal? Vulgaris
What series does desmoglein and desmocollin connect to? Plakoglobin and plakophilin which are connected together by desmoplakin
Describe the structure of plakophilin Has a globular head and a linear tail
True or False: Desmoplakin is the most abundant protein in the desmosome True
Describe the granular layer Next to spinous layer, granular structure is caused by the induced synthesis of a protein called filaggrin that happens at the level of granular keratinocytes
Describe filaggrin Molecule that is synthesized as a profilaggrin molecule but contains multpile repeating subunits which is then degreade by a protease into 2 and 3 subunit pieces then into the molecule filaggrin
Describe the inactive form of filaggrin heavily phosphorylated to neutralize histindine
What happens when filaggrin is activated/dephosphorylated? Keratin filaments aggregate into clumps.
What happens at the level of the granular layer in terms of the cytoplasm? Turn the living cytoplasm of the cell into a brick
How is the vapor barrier formed? Stacks of neutral lipids that are secreted between keratinocytes. Lipids secreted are synthesized in organelles in the keratinocyte that are called lamellar bodies or membrane coating granules
What does the cornified envelope of the skin allow you to do? To protect the blood. You can use soap and rub it on your skin without the cells lysing.
What is the process of terminal differentiation? Formation of lamellar bodies that makes the secretion of the lipids just before the other membrane turns into the cornified envelope
Icthyosis Vulgaris Caused by a filaggrin mutation which disrupts terminal differentiation so you don't get normal lipid depostion. Keratinocytes on the outer surface are no longer smooth. (Alligator like)
Psoriasis Very rapid cell growth program. Instead of 4 weeks to go to terminal cell it can be 4 days to make an immature cell before it gets sloughed off. No lipids=defective barrier
Wound healing Keratinocytes make new keratin (K16)
What 2 parts make up the basement membrane that keratinocytes sit on? Lamina densa and lamina lucida (Collagen fibers are present)
Epidermolysis bullosa Caused by defective adhesion function for either the keratin filaments, connecting fibrils or anchoring fibrils
Junctional epidermolysis bullosa Anchoring filaments within the lamina lucida are defective. Constant injury and blistering to the skin
Dystrophic epidermolysis bullosa Break in the anchoring fibrils that loop structures that are connecting to collagen fibers
What are melanocytes? Pigmented granules called melanin granules and they are transferred to the cytoplasm of keratinocytes through a process called apocopation
What is Vitelligo? Where melanocytes are killed off by an immune attack process
What are Merkel cells? A neuroendocrine cell, has pre-synaptic granules that contain neurotransmitters.
What do Langerhan cells do? They can stimulate the activation of T cells. Has an organelle called Birbeck granule
What is aptopic dermatitis? Disease of overreactive Langerhans cells which can be caused by drug allergies
Describe erythema multiforme Blistering that occurs in the skin triggered by underlying T cell activation
Describe epidermal necrolysis loss of entire skin surface and death
Name the hair growth phases Anagen: Growth phase, Catagen: Growth ceases, Telogen: Extended growing hair shaft falls out
How is the induction of hair growth controlled? By the dermal papilla
What is androgenic alopecia? Male pattern baldness
Describe telogen effluvium Stress or another factor causes hair to fall out but it usually grows back
Describe alopecia areata Autoimmune condition where T cells inhibit growth of hair