BIOLOGY 173 Lecture Notes - Lecture 13: Dense Irregular Connective Tissue, Loose Connective Tissue, Stratified Squamous Epithelium
1 Oct 2016
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If you didn"t cut your hair for 70 years how long would it be and how much would it. Hypodermis / subcutaneous / superficial fascia: not skin, anchors skin to underlying organs, adipose and areolar connective tissue. Palms of hands and soles of feet: thin. 15-30-rows of dead flat cells that are interlocked. Water resistant (not waterproof: stratum lucidum - clear. Flat, packed keratinocytes filled with keratin: stratum granulosum. Darkly stained layer containing 3-5 rows of keratinocytes that have stopped dividing. Synthesis begins of keratohyalin and keratin, the waterproofing proteins. Keratinocytes begin to die and dehydrate: stratum spinosum. 8-10 rows of spiny shaped keratinocytes held together by desmosomes. Protects against cancer and bacteria: stratum germinativum or basale. Single layer of stem cells capable of cell division. Attached to basement membrane (bm) that separates epidermis from dermis. Forms epidermal ridges that extend into dermis: timeframe: 7-10 days to go from germinativum to corneum.
