Jain Chapter 1 - Basic Science Flashcards
(56 cards)
What has developed by 3-4 weeks gestational age?
Single layer of ectoderm
What has developed by 6 weeks gestational age?
Outer flattened periderm and inner, cuboidal germinal (basal) layer
Germinal layer in contact w/ underlying mesenchyme (germinal layer produces entire epidermis)
What has developed by 7 weeks gestational age?
*Fetal basement membrane
Tooth primordia
What has developed by 8-12 weeks gestational age?
Epidermal stratification begins ~8 weeks (Completed by 2nd trimester)
*Appearance of Melanocytes, Langerhans cells, Merkel cells
Dermal-subcutaneous boundary distinct
What has developed by 9-12 weeks gestational age?
Appearance of anchoring filaments/hemidesmosomes
Hair follicle and nail primordia seen
What has developed by 12 weeks gestational age?
- Formation of dermoepidermal junction (DEJ)
- Nail bed starts to keratinize, proximal nail fold forms
Type III collagen appears
What has developed by 12-14 weeks gestational age?
Parallel ectodermal ridges (fingerprints)
Eccrine and sebaceous gland primordia seen
Fibroblasts actively synthesizing collagen and elastin in dermis
What has developed by 12-24 weeks gestational age?
Melanin production (12–16 wks), melanosome transfer (20 wks)
Hair follicles differentiate during 2 nd trimester (7 concentric layers present)
What has developed by 15-20 weeks gestational age?
Periderm is shed (periderm is part of vernix caseosa) [20–21 weeks]
*Follicular keratinization, nail plate completely covers nail bed
Papillary/reticular boundary distinct, dermal ridges appear
What has developed by 22 weeks gestational age?
Trunk eccrine gland primordia
Elastic fiber seen
What has developed by 22-24 weeks gestational age?
*Mature epidermis complete (w/ interfollicular keratinization)
Adipocytes appear under dermis
How thick is:
- eyelid skin
- palmoplantar skin
eyelid = 0.04 mm
palmoplantar skin = 1.5
Keratinocytes comprise approximately ___ of epidermal cells
80–85%
Total epidermal turnover time
Average 45–60 days (30–50 days from stratum basale to stratum corneum and approximately 14 days from stratum corneum to desquamation)
Epidermal self-renewal maintained via stem cells in basal layer of ___ epithelium and the bulge region of hair follicles (latter location only activated with epidermal injury)
interfollicular
Keratinocytes produce ___
keratin filaments (syn: intermediate filaments or tonofilaments), which form the cell’s cytoskeletal network; this provides resilience, structural integrity, along with serving as a marker for differentiation (ie. basal layer: K5/14)
Type I (acidic) epithelial keratins
K9–28, chromosome 17
Type I (acidic) hair keratins
K31–40 (old nomenclature: hHa1–hHa8, Ka35, Ka36)
Type II (basic) epithelial keratins
K1–8 and K71–80, chromosome 12
Type II (basic) hair keratins
K81–86 (old nomenclature: hHb1–hHb6)
Location of expression and disease: 1 & 10
Suprabasal keratinocytes
Epidermolytic hyperkeratosis, UnnaThost PPK
Location of expression and disease: 1 & 9
Palmoplantar suprabasal keratinocytes
Vorner PPK
Location of expression and disease: 2e & 10
Granular and upper spinous layer
Ichthyosis bullosa of Siemens
Location of expression and disease: 3 & 12
Cornea
Meesman corneal dystrophy
