Layers and Cells of the Skin Flashcards
(43 cards)
what are the 4 layers of the epidermis (and the 5th layer that is sometimes found)?
(external -> internal)
1 - stratum basale (basal cell layer)
2 - stratum spinosum (prickle cell layer)
3 - stratum granulosum (granular cell layer)
( stratum lucidum - clear layer)
4 - stratum corneum
what type of epithelium is found in the skin epidermis
stratified squamous epithelium
what is the structure of the basal cell layer? (2)
- row of columnar keratinocytes
* attached to the basement membrane by hemidesmosomes
why is the basal cell layer very mitotically active?
small proportion of keratinocytes are stem cells that continuously divide
what cytoplasmic structure is found in basal cells? where do they converge?
- tonofilaments
* hemidesmosomes
what 3 cells are found in the basal layer?
- keratinocytes
- melanocytes
- Merkel cells
what is the structure of the prickle cell layer? (3)
- polyhedral keratinocytes
- interconnected with desmosomes
- give cells a spiny appearance (ie. prickle)
what cytoplasmic structure is found in cells of the prickle layer? where do they converge?
- tonofilaments bundled together forming supportive tonofibres
- desmosomes
what 2 cells are found in the prickle layer?
- keratinocytes
* Langerhans cell
what is the structure of the granular layer?
flattened cells containing important granular structures
what 2 cell processes begin to happen in the granular layer?
- removal of nuclei
* expulsion of lipids and liquid from the cytoplasm
what is the structure of the horny layer?
sheets of cornified cells with no nuclei, stuck together by lipid glue
where on the body is the horny layer thickest? - these areas also have a stratum lucidium
palms of hands and soles of feet
what is the cytoplasm replaced with in the cells of the horny layer?
keratin fibrils
why are cells of the horny layer stuck together with lipids?
makes the skin surface water tight
what is the top layer of their dermis and what are 2 of its features?
• papillary layer
- interdiginates with epidermis
- composed of of loosely woven collagen
what is the lower layer of the dermis and what is a feature of it?
- reticular layer
* coarse, horizontally running bundles of collagen
what material makes up 70% of the dermis, and what quality does this provide the dermis?
- collagen
* toughness and strength
what fibre is incorporated into the collagen network in the dermis? what quality does this provide?
- elastin
* elasticity
what is the ground substance in the dermis and what is its purpose?
- semi-solid matrix
* allows dermal structures some movement
what cells are present in the dermis?
- fibroblasts
- dermal dendritic cells
- mast cells
- lymphocytes
- macrophages
what it is the structure of the hypodermis?
adipose tissue with supporting fibrous bands
why is skin regenerating important? (2)
- horny layer is important for preventing microorganisms, water etc. from entering the skin
- epidermis prevents fluids from getting out
what is the keratinocyte maturation sequence? (7)
1 - stem cells continuously divide into 1 new stem cell and a transit amplifying cell
2 - transit amplifying cells proliferate briefly before progressing upwards for terminal differentiation
3 - in prickle cell layer, cell changes shape from columnar to polygonal
4 - differentiating keratinocytes synthesise keratins
5 - in granular layer, enzymes induce degradation of nuclei and organelles
6 - in horny layer, dead and flattened corneocytes have developed cornified envelopes
7 - corneocytes eventually shed from skin surface after degradation of the lipid glue and loss of desmosomes intercellular connections
