Flashcards
Th3L06 The epidermis
Cards in this deck (53)
- 1The skin is the largest single organ in the body making up __% of body weight?16
- 2What is the composition of the skin?Epithelial layer (epidermis) resting on connective tissue layer (dermis)
- 3What is the composition of the dermal/epidermal junction is not flat?It is not flat, it contains dermal papillae and epidermal ridges
- 4What are dermal papillae?A finger-like projection of the dermis that may contain blood capillaries or Meissner corpuscles (of touch)
- 5What are epidermal ridges?Increase friction, provide better gripping surface, causes fingerprints
- 6What is the function of the skin? (5)Protection, prevention desiccation, sensation, thermoregulation and metabolic
- 7How does the skin provide protection? (2)* Mechanical contact, abrasion
* Against water and electrolyte loss - 8What are the metabolic contributions of the skin?* Store of fat (in the hypodermis)
* Source of vitamin D synthesis (in the epidermis) - 9What are the classifications of the skin? (2)Thick and thin
- 10What are the characteristics of thick skin?Very thick, cornified (keratinised) layer that lacks hair follicles
- 11Where is thick skin found?Soles of feet and palms of hand
- 12What are the characteristics of thin skin?Thin, cornified layer, generally contains hair follicles
- 13Where is thin skin found?* Body skin (sparse, fine hairs i.e. vellus hair)
* Scalp (numerous, closely-packed coarse hairs i.e. terminal hair) - 14Describe the epithelium of the epidermis?Stratified, squamous kertanising
- 15What is the role of the epidermis?Protection
- 16What is the principal epidermal skin type of the epidermis?Keratinocyte
- 17What are the layers of the epidermis? (in order of base layer to top layer)Stratum basale, Stratum spinosumn, Stratum granulosum, Stratum corneum
- 18Describe the epithelium in Stratum basale:Cuboidal or columnar cells
- 19What is the main role of Stratum basale? (4)* Site of cell division
* Daughter cells leave this layer for the upper layers
* Cell division is mostly confined to basal layer
* Cell replacement is from of division of undifferentiated stem cells - 20Transit from basal layer to surface takes approx how long?25-50 days
- 21Describe the epithelium in Stratum spinosum:- Prickle cell layer
- Numerous spot desmosomes, enlarge and accumulate large quantities of keratin proteins (about 40% of the cell) - 22What are desmosomes?* Anchoring junctions that prevents cells subjected to mechanical stress from being pulled apart
* Button like thickenings of adjacent plasma membranes connected by fine protein filaments - 23What is pemphigus?* Blistering disease due to auto-antibodies attacking desmoglein, component of desmosomes
* Desmosomes weaken
* Autoimmune disease
- 24What is involucrin?* Protein that begins to be made in Prickle cell layer
* Becomes cross-linked to form a cornified envelope (highly resistant) - 25What is the role of keratin proteins?They are organised into 10nm intermediate filaments to form prominent bundles that converge on the desmosome
- 26Describe the epithelium in Stratum granulosum:* (granule layer)
* Flattened cells, keratohyaline granules apparent, contains profilaggrin (protein) - - 27What is the last living epidermal cell layer?Stratum granulosum
- 28Describe the epithelium in Stratum corneum:* Cells become extremely flattened (squamous)
* It is the cornified layer
* Keratins become cross-linked disulphide bridges
* Cells die, lose nuclei and other organelles, become dehydrated
* (packing the keratin filaments together) - 29Where is profilaggrin?A protein cleaved in the cornified layer which aggregates the keratin filaments, facilitating cell flattening, and contributes to the barrier function
- 30Inherited mutations in filaggrin causes what?Ichthyosis vulgaris, increased risk of eczema, allergic rhinitis and peanut allergy
- 31What is Ichthyosis vulgaris?Autosomal dominant disorder of keratinization caused by the decreased or lack of profilaggrin synthesis which affects the granular and cornified layers
- 32What is allergic rhinitis?An allergic reaction to airborne allergens that causes an increased flow of mucus
- 33Cells of the epidermis become WHAT as you move towards the surface?Flatter
- 34What is the permeability layer?Epidermal layer that makes the skin waterproof
- 35What does the permeability layer contain?Membrane coating granules (Odland bodies, lamellar bodies, keratinosomes)
- 36What are membrane coating granules?Stacks of phospholipid lamellae, released from cells into intercellular space, fuse together to form multiple lipid bilayers arranged as sheets between cells to serve a water-tight barrier
- 37What does cell renewal occur?when mature, functional cells of cornified layer are dead
- 38Where and by what is melanin produced?In the epidermis by melanocytes
- 39What is the primary role of melanin?Protection against UV
- 40Melanocytes are derived from what?The neural crest
- 41When do melanocytes migrate to the skin?During development
- 42Melanocytes are what kind of cell?Stellate
- 43Where is the epidermis are melanocytes found?Mainly in the basal layer
- 44How do melanocytes vary between races?Numbers DO NOT vary between races only the activity of them
- 45What is melanin made from?Tyrosine in melanosomes which bud from melanocytes and are endocytosed by keratinocytes
- 46What are melanomas?Tumours of melanomas
- 47What are melanomas caused by?Repeated sun-burning
- 48What causes hyperpigmented skin?When epidermal cells arrange melanin pigment in a cap over the nucleus causing melanin disappears in upper layers, but the actual cause is unclear
- 49What is human vitiligo?Autoimmune destruction of melanocytes
- 50What are Langerhans cells?Macrophage-like cells that play important role in immunological defence by processing foreign antigens
- 51Where are Langerhans cells found?Upper prickle cell layer (Stratum spinosum)
- 52What are Merkel cells?Epidermal cells with low levels of RNA that are associated with nerve endings, and as such may be involved in sensory perception
- 53Where are Merkel cells found?* Found in basal part of epidermis associated with nerve endings
* Express different types of keratins to keratinocytes
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- Medicine Y1 (Theme 3 | Tissues and systems) Flashcards on Th3L06 The epidermis , created by Emma Allde on 07/09/2016.
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