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BIOC33H3 Study Guide - Dermis

Biological Sciences
Course Code
Stephen Reid

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Sperm-has midtail, head and tail
Mitochondria in midsection
Choleciferol –produced by epidermal cells when exposed to UV light. Calcitrol, active form
of Vit D, promotes calcium and phosphate absorption and regulation.15 min/day will
provide your body with its daily vit d requirement.
Dermis-middle layer of skin (=integument). Composed mainly of cells of connective tissue
and collagen fibers although both elastic and reticular fibers are also present
Other component of dermis are blood vessels, sweat glands, sebaceous glands, hair follicles,
nail roots and sensory nerve endings and smooth muscle tissue
Consist of 2 layers:
Papillary layer superficial, adjacent to the epidermis, composed of areolar connective
tissue and its name comes from the projections of the dermis towards the epidermis 
dermal papillae
The dermal papillae interlock with the epidermal ridges *deep projections of the epidermis )
Together the dermal papillae and the epidermal ridges increase the contact between these
Each dermal papillae contains the capillaries that supply nutrients to the cells of the
epidermis, the dermal papillae also contains the sensory receptors that continuously
monitor touch on the surface of the epidermis.
Reticular layer of the dermis
-forms the deeper and the major portion of the dermis and extends from the thin papillary
layer to the underlaying subcutaneous layer. contains dense irregular connective tissue
through which bundles of collagen fibers extend in all directions. The collagen fibers are
interwoven in a meshwork. these collagen fibers make it hard to make a distinct marcation
of the papillary layer and the reticular layer
Reticular- meshwork of collagen fibers
Epithelium of the skin
Keratinized and stratified squamous epithelium
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Avascular depends on diffusion from the underlying dermis
Epidermal strata : stratum: basale, spinosum, granulosum, lucidum and corneum
Stratum lucidum is found in thick skin only
Stratum corneum , lucidumand granulosum are composed of living keratinocytes
and the last two contain dead keratinocytes
Stratum basale layer of cuboidal cells divide rapidly to produce the cell layers
Stratum basale is the germinal layer
Keratinocyte: principal cell type
Produces keratin, toughens and waterproofs the skin so that skin is water resistant
called cytokeratins as keratinocytes are pushed upwards, they move farther away
from o2 and blood supply of the layers below
The keratins found in the epidermal cells of the skin is called cytokeratins
Stratum lucidum-clear layer
-pale and translucent regions, 2 or 3 layers thick
Found only in thick skin
Cells are pale and featureless and indistinct boundaries
Keratinocytes are flattened and filled with eleidin
Keratinisation –process where keratinocytes found in epidermal cells become filled with
keratin,the insoluble protein and the nucleus and teh organelles of the keratinocyet s start
to degenerate cells become thiner and flatter.membranes thicken and become less
permeable and cells start to die
~ a fully kearatinized cell is dead but strong and tough
Stratum corneum:
-most superficial layer of the epidermis
-U see it when u look at your skin ,20 -30 layers!!!
-dead scaly, interlocked keratinized cells called corneocyets. The dead cells are anucleate
and tightly packed together
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