Cornification Flashcards
Please match the cell cycle phase with the appropriate description:
__M phase___ Shortest phase in which daughter cells are produced
__S phase____ Phase in which DNA replication occurs
__G1 phase___ Longest stage in cell cycle
What are the 3 types of cell kinetics exhibited by tissues in the body? Which type best represents epidermal cell kinetics?
Static: Cell number is stable from birth (no mitosis) - ie CNS
Expanding: Increased mitotic activity → enlargement of tissue (liver, muscle, etc)
Renewing: Mitosis replaces lost cells. Constant turnover → no net change in cell number. (epidermis, GI mucosa)
What are the two determinants of the rate of cell proliferation? (Kw)
Static: Cell number is stable from birth (no mitosis) - ie CNS
Expanding: Increased mitotic activity → enlargement of tissue (liver, muscle, etc)
Renewing: Mitosis replaces lost cells. Constant turnover → no net change in cell number. (epidermis, GI mucosa)
What is the transit time through the normal epidermis in the horse:
A. 8 days: Seborrheic Cocker B. 15 days: Pig C. 17 days D. 22 days: Normal dog E. 26 days: Horse (Human: 26-42 days)
In the human basal layer what % of keratinocytes are stem cells, transient amplifying cells, and differentiated cells (Fitz)?
Stem cells: 10%, transient amplifying cells: 50%, differentiated cells: 40%
Define Holoclone, Meroclone, & Paraclone:
Holoclone: corresponds to stem cells; colonies of small, regular cells; give rise to many other colonies
Meroclone: correspond to transient amplifying cells; produces colonies, but fewer in number than holoclones; located in basal & suprabasal layers, provide the bulk of cell divisions needed for stable self-renewal
Paraclones: correspond to differentiated, post mititotic cells; undergo terminal differentiation; yield only very small number of colonies
What are the four major cell types of the epidermis? Give the embryological origin of each.
Keratinocyte - ectoderm; Melanocyte - neural crest ectoderm; Langerhans cell - reticulo- endothelium; Merkel cells - unknown
How is the keratin profile different in psoriatic lesions from normal skin - specifically with regards to keratins, 1, 5, 6, 10, 14 and 16?
Increase in keratins 6 and 16; decrease in keratins 1 and 10; Keratins 5 & 14 are unchanged
Epidermal layer where the metabolic barrier of the epidermis occurs:
Spinous layer
X-linked icthyosis is a defect in:
A. Rod mutation of the keratin molecule
B. Absence of steroid sulfatase
C. Defect in laminin 5
D. Mutation of transglutaminase I
B. Absence of steroid sulfatase
Epidermal layer where the metabolic barrier of the epidermis occurs:
Spinous layer
—— is a protein rich in histidine that is involved in aggregating keratin intermediate filaments into macrofibrils. Its precursor is found in ———, and later is degraded into ——- and —— which function —— radiation and ———.
Filaggrin is a protein rich in histidine that is involved in aggregating keratin intermediate filaments into macrofibrils. Its precursor is found in keratohyalin granules, and later is degraded into urocanic acid and pyrrolidone carboxylic acid, which function in filtering UV radiation and maintaining epidermal hydration.
——- is a cysteine-rich protein that forms the major protein component of the cornified envelope and accounts for —- of the cornified cell envelop mass.
Loricrin is a cysteine-rich protein that forms the major protein component of the cornified envelope and accounts for 70% of the cornified cell envelop mass.
Summarized the steps of cornification
- TG 1, 3 and 5 crosslink involucrin to desmosoma proteins (envoplakin, periplakin)
- TG 1 crosslinks involucrin to w-OH ceramamids outside of cell
- TG1 and 3 crosslink loricrin to SPR proteins
- Filaggrin binds KIFs inside cell and crosslinks to loricrin
