Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
28 Cards in this Set
- Front
- Back
|
Epithelial tissue
|
Made up of epithelial and glands:
Epithelia: layers of cells that cover internal and external surfaces Glands: structures that produce fluid secretions |
|
|
Cellularity of epthelia
|
Composed of cells bound together by cell junctions (compare: other cell types separated by extracellular material)
|
|
|
Polarity of epithelia
|
Structural and functional differences between the exposed and attached surfaces. In an peithelium consisting of a single layer of cells:
- The exposed (apical) and attached (basal) surfaces differ in membrane structure and function |
|
|
Attachment of epithelium
|
The base of an epithelium is bound to a thin basement membrane or basal lamina
- BM is a complex structure produced by the basal surface of the epithelium and the underlying connective tissue |
|
|
Avascularity of epithelium
|
Lack blood vessels, are supplied by nutrients via diffusion or absorption across either the exposed or the attached epithelial surface
|
|
|
Regeneration of epithelia
|
Epithelial cells that are lost or damaged are continuously replaced through stem cell division in the epithelium.
|
|
|
Layers of epithelium
|
1. Surface film
2. Epidermis 3. Dermal-epidermal junction 4. Dermis 5. Subcutaneous tissue |
|
|
Surface film
|
Thin film coating the skin, made up of a mixture of sweat, sebum, dead cells and various chemicals
|
|
|
Layers of the epidermis
|
1. Stratum corneum
2. Stratum granulosum 3. Stratum spinosum 4. Stratum basale |
|
|
Stratum corneum
|
Several layers of flake-like dead cells (corneocytes), mostly made up of dense networks of keratin-like fibres connected together (corneodesomosomes) to form a tough, waterproof barrier
- Keratinised layer - Corneocytes are terminally differentiated keratinocytes |
|
|
Stratum lucidum
|
Only present in areas of thick skin e.g. soles of feet, palms of hands
- Thin, clear dead layer of dead, flattened keratinocytes - Keratinocytes are filled with eleidin, an intermediate form of keratin |
|
|
Stratum granulosum
|
2-5 layers of dying, somewhat flattened cells filled with darkly staining granules
- nuclei disappear in this layer |
|
|
Stratum spinosum
|
8-10 layers of cells pulled together by desmosomes into a shiny appearance
- "prickly" appearance given by desmosomes - Keratinocytes with large, pale-staining nuclei |
|
|
Stratum basale
|
Single layer of mostly columnar cells, capable of mitotic division
- from this layer all superficial cells are derived, including keratinocytes and some melanocytes - Langerhans cells, Merkel cells and melanocytes are found here |
|
|
Epidermal turnover
|
1 month: complete turnover
- 2 weeks from granular layer to stratum corneum - 2 weeks for corneocyte to move to the surface of the stratum corneum and be shed into the environment |
|
|
Keratinocytes
|
Primary function: barrier against heat, water, UV radiation and pathogens
- Can release chemokines if react with pathogen (IL-10, TGF-b) - Take up melanosomes to protect from UV |
|
|
Melanocytes
|
Found in the basal layer of the epidermis, 10% of cells
- numbers vary with UV exposure - Number doesn't vary, but in darker skin are larger and have more processes - Dendritic processes transfer melanosomes to keratinocytes |
|
|
Langerhans cells
|
Originate in bone marrow - (2-4% of epidermal cell population)
- antigen presentation/immune surveillance - numbers unaffected by UV, but increase in immune response - derive from differentiation of monocytes |
|
|
Other structures in the epidermis
|
Nerves, sweat glands, hair, blood vessels, lymph vessels and connective tissue
|
|
|
Psoriasis
|
Relapsing immune-mediated skin disease.
- excessive and abnormal growth of skin cells - premature maturation of keratinocytes due to immune response |
|
|
Icthyosis
|
- dry, cracked skin, mostly caused my genetic disorders
|
|
|
Keratoderma
|
Horn-like skin condition, associated with defects in genes for keratin
|
|
|
Eccrine glands
|
Temperature control glands that secrete sweat
- everywhere except nail beds and lips - most abundant on palms, soles and axillae |
|
|
Apocrine glands
|
- Scent glands, role unclear in humans
- Axillare and genitals |
|
|
Sebaceous glands
|
- Present everywhere except palms and soles
- Greatly enlarge at puberty in response to androgens - Main function to provide lipids to lubricate hair shaft |
|
|
Dermo-epidermal junction
|
- Complex region holding together epidermis and drmis
- Basement membrane - Keratinocytes and fibroblasts |
|
|
Epidermolysis bullosa
|
Genetic connective tissue disorder
- protein anchors of the skin affected |
|
|
Ehlers Danlos Syndrome
|
Faulty or reduced amounts of collagen, causing hypermobility of joints, hyper elasticity of skin, Osgood-Schlatter's disease etc.
|
