4 - Developmental Biology Flashcards
Central cells of the epidermis
Keratinocytes
Provides structural resiliency
Intermediate filament keratins
Central cells of the dermis
Fibroblasts
Extracellular secreted proteins; activate the frizzled receptors to eventually stabilize B-catenin
Wnt ligands
Transcription factor; central regulator of epithelial identity
p63
Extracellular secreted proteins; bind the smoothened receptor and eventually the Gli family of transcription factors
Shh ligands
Bind the receptor Notch which initiates transcription and epidermal differentiation
Ligands Delta or Jagged
Important in large-scale body patterning
HOX (homeobox) transcription factor family
Protein most abundant in the epidermis
Keratin
Most abundant protein in the dermis
Collagens
When organogenesis has mostly completed
First trimester
Weeks 0-12
Appearance of downy hair
Second trimester
Weeks 12-26
When most development completes
Third trimester
Weeks 26-40
Formation of the vernix caseosa
Third trimester
Initial unstructured multiplication of cells
Morula
Morula divides to form a
Blastula
2 main parts of a blastula
Trophoblast
Inner cell mass
Trophoblast becomes the
Placenta of fetal origin
Inner cell mass becomes the
Embryo
Inner cell mass differentiates into this 3-layered structure
Gastrula
First stage where skin development separate from the development of other organs
Gastrula
Ectoderm forms the
Epidermis
Melanocytes
Nervous system
Mesoderm forms the
Fibroblasts
Blood vessels
Muscles
Bone
Y/N: Endoderm contributes to skin development
No
Neural crest development initiates during
Third week
Initial stage of neural crest development
When the ectoderm forms the neural plate within it
Differentiates into the future central nervous system
Neural plate
Part of the ectoderm that remains free in the mesoderm
Neural crest
Neural crest migration in the head vs trunk
Head: neural crest migrate before neural tube closure
Trunk: neural crest migration is the last event
Persistent neural crests cells that do not complete migration and differentiates into melanocytes are hypothesized to contribute to
Common blue nevi
Mesoderm condenses into regular-spaced cuboidal segments which are lateral to the neural tube
Somites
Somite formation during
Third week
Somites contribute to
Axial skeleton and muscles
Dermal fibroblasts
First step in skin formation
Ectoderm converts to a single later known as the germinativum
Germinativum expresses the gene
p63
p63 gene corrupted in
EEC syndrome (ectrodactyly-ectodermal dysplasia-cleft syndrome)
Flattened cells with tight junctions and polarized cytoskeletal adhesions that form above the germinativum
Periderm
Periderm forms at
15 days
Lack of periderm formation leads to
Human cocoon syndrome
Formed between the periderm on the outside and the germinativum layer
Intermediate layer
Intermediate layer forms at
60 days
Barrier formation initiating at the
Dorsum and head
Most common defect in cornification
Ichthyosis vulgaris
Ichthyosis vulgaris caused by defects in
Filaggrin protein
Surface ectoderm/periderm keratins
K8/K18
Intermediate layer keratins
K1/K10
Basal layer keratins
K5/K14
Fibroblasts derivation:
Ventral body -
Head -
Back skin -
Ventral body - lateral plate mesoderm
Head - neural crest precursors
Back skin - somites
Upper dermal fibroblast progenitor become
Dermal papillae
Arrector pili muscle
Papillary fibroblasts
Lower dermal fibroblast progenitor become
Adipocytes
Reticular fibroblasts
Differentiates to myofibroblasts during wounding
Reticular fibroblasts
Upper vs lower dermal fibroblast progenitor collagen synthesis
Upper: collagen 3 > collagen 1
Lower: collagen 1 > collagen 3
Upper vs lower dermal fibroblast progenitor markers
Upper: PDGFRa+, Blimp1+, Dlk-, Irig+
Lower: PDGFRa+, Blimp-, Dlk+
Type of adipose thats stores energy as lipid
White adipose
Type of adipose thats burns energy through the uncoupling of oxidative phosphorylation to generate heat
Brown adipose
Brown adipose cells located in
Paracervical/interscapular
Supraclavicular areas
Transcription factor important for both white and brown adipose development
Peroxisome-proliferator-activated receptor gamma (PPAR gamma)
Transcription factor uniquely important food brown adipose development
Prdm16
Manifested as herniations appearing a soft yellow to red noodles appearing in Blaschko lines and ulcers at sites of absent skin
Focal dermal hypoplasia or Goltz syndrome
Goltz syndrome caused by mutations in the
PORC gene
Berardinelli-Seip caused by
Defects in the lipid synthesizing AGPAT2 gene
Melanocytes by be detected by the _____ week EGA in human epidermis
8th
_____-positive progenitor can differentiate into glial cells in addition to melanocytes
SOX10
When differentiating into melanocytes, SOX10-positive progenitors begin to express the critical transcription factor
Micropththalmia-associated transcription factor (MITF)
DCT and KIT proteins
Dermal melanocytes are thought to persist after birth in several locations
Dorsa of the hands and feet
Sacrum/buttocks
Scalp
*clinically important because they are also common sites for blue nevi
Defective melanocyte development where disrupted melanocyte migration occurs due to defects in, for example, c-kit growth factor
Piebaldism
Sensory neurons develop from the _____ (head) or _____ (elsewhere)
Trigeminal
Dorsal root ganglia
Merkel cells are found as early as _____ weeks EGA
12
Merkel cells highest density at
Volar sites
Appendages
Nerves
Stages of hair follicle development
Hair placode (75 days)
Hair germ/bud (80 days)
Peg (100 days)
Bulbous peg (13-14 weeks)
Earliest morphologic change in hair formation
Hair placode
Keratinocytes become thinner, columnar, tightly packed, and is accompanied by accumulation of congregated or condensed fibroblasts beneath the dermis
Hair placode
Downward movement of epithelium forming a clear nubbin
Hair germ/bud phase
Epithelium begins to wrap around and encompass the associated inductive fibroblast population, which is now called the dermal papillae
Peg stage
Sebaceous glands are formed
Bulbous peg stage
First wave of hair production
Lanugo hair (130 days)
Y/N: Most lanugo hair is shed before birth
Yes
Hair follicle stem cell compartment
Bulge
Activity of _____ is perhaps the most important for appendage development
Beta-catenin
Sebaceous glands more active during _____ and ______
Embryogenesis (production of vernix caseosa)
Puberty
Sebaceous glands not associated with hair follicles
Orphan sebaceous glands
Orphan sebaceous glands locations
Meibomian gland of the eye
Fordyce spots of the mouth
Tyson glands of the prepuce
Montgomery glands of the female areola
Sweat glands in the volar skin develop around _____ weeks EGA, and the rest of the body at _____ weeks
12-13
20
Volar dermatoglyphics development begins around
Week 7
Required for the recruitment of angiogenesis-associated cells such as pericytes
Angiopoietin-1
_____ released by arteries as a ligand for _____on veins is important to maintain the AV plexus
EphrinB2
EphB4 receptor
Lymphatic development occurs through the maturation of established venous endothelial cells that express
PROX1
Sturge-Weber caused by defects in
GNAQ gene
Hematopoietic cell development occurs in the following organs (in chronological order)
Yolk sac
Dorsal aorta
Liver
Bone marrow
Langerhans cells are detectable by
10 weeks EGA
Impaired TH17 development and excessive TH2 profile odds eosinophilia and hyper-IgE characterized by chronic eczema and recurrent skin Staphylococcus aureus infections
Hyper-IgE syndrome or Job syndrome
Hyper-IgE syndrome or Job syndrome mutation
Signal transducer and activator is transcription 3 (STAT3)