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Embryo > Introduction to Embryology > Flashcards

Introduction to Embryology Flashcards

1
Q

Embryology Scope

A

Study of development of an organism from fertilization of the ovum through the period of organogenesis.

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2
Q

Embryonic period

A

From fertilization (from single cell) to 8th week of human development.
Organogenesis

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3
Q

Fetal Period

A

9th week to 38th week (Birth)

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4
Q

Karl Ernst Von Baer (XIX)

A

Father of modern embryology:
1. Described the oocyte and the cleaving zygote, blastocysts, and stages of embryonic development. “Established that mammals develop from eggs”
2. Determined that general characteristics precedes from specific ones: Phylotypic stage in embryonic development. Ancestor of vertebrates have a common basic vertebrate body

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5
Q

Hyppocrates

A

Father of medicine

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6
Q

Aristotle

A

Founder of embryology

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7
Q

Leonardo Da Vinci

A

Measurements of prenatal growth

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8
Q

Anton van Leeuwenhoek

A

Observed sperms under microscope

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9
Q

Regnier de Graaf

A

Eggs from the ovaries

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10
Q

Hans Spemann

A

Nobel Prize in Medicine 1935
Primary induction (Gastrulación)

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11
Q

Lewis, Nusslein-Volhard and Wieschaus

A

Novel Prize in Medicine 1995.
Discovery of genes that control embryonic development

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12
Q

Time line
Blastocyst

A

First two weeks.
This is a period of cell proliferation from the zygote to the morula, blastocyst, and bilaminar embryonic disc formation. Birth defects do not originate in this period because body systems and structures have not yet developed. Teratogens usually cause the loss of the entire conceptus.

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13
Q

Timeline
Embryonic Period

A

The third to Eighth week constitutes the dynamic period of gastrulation, folding of the embryo, and the formation of all the organ systems. Because this is the most active period of development and differentiation, the embryo in weeks 3 to 8 is most vulnerable to major birth defects.

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14
Q

Timeline
Fetal Period

A

The dominant theme in months 3 to 9 (full term) is growth of all major structures that have already appeared. Birth defects in this period are usually not as severe or obvious and include small size, mental retardation, and defects in the eyes, ears, teeth, and external genitalia.

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15
Q

Early Embryonic Developmental Stages
30 hours after fertilization

A

Repeated mitotic division

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16
Q

Blastomeres

A

Increased # of cells together with a decreased in size.

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17
Q

Morula

A

After the 8-cell stage, cell compactation occurs. (12-32 cells)
3 days after fertilization

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18
Q

Blastocyst

A

Fluid-filled blastula

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19
Q

Gastrula

A

Characterized by the formation of the 3 germ layers.
Ectoderm, mesoderm and endoderm
3rd week
Organizer: Primitive knot/node (Hensens node in humans)
Will induce the notochord

20
Q

Neurula

A

Stage in which neurulation occurs (development of nervous system)
Neural tube formation

21
Q

Notochord

A

Embryonic-specific structure that defines the primordial axis of the embryo.
Defines the phylum of chordates: urochordates and vertebrates
Gives some rigidity
Is the basis of the development of the axis skeleton
It disappears when the vertebral bodies form (4th week)
It degenerates and disappears, but it persists as the nucleus pulpous (NP) of each intervertebral disc.
Chardoma- tumors formed by vestigial remnants of the notochord

22
Q

Pharyngeal (Branchial arches)

A

Condensation of mesoderm in the cranial region will give rise to transient structures to develop vertebrate head structures.
Example: 1st vertebral arch gives rise to the cartilage of the mandible

23
Q

Induction

A

Process in which one group of cells or tissues causes another set of cells or tissues to change their fate.
One cell type or tissue is the inducer that produces a signal, and one is the responder to the signal.
Crosstalk between the two cell types or tissues is essential for differentiation

24
Q

Notochord induces

A

overlying ectoderm to form neural plate (neuroectoderm)

25
Q

FGF-B up regulation…

A

promotes neural plate formation

26
Q

BMP-4 inhibition…

A

promotes epidermis formation

27
Q

Intercellular comunication

A

paracrine
juxtacrine
cell-cell

28
Q

Paracrine examples

A

morphogens, growth and differentiation factors

29
Q

Juxtacrine examples

A

Receptor/membrane-bound ligand in adjacent cell

30
Q

Cell-cell example

A

Gap junctions

31
Q

Cell differentiation

A

Cells become specialized by means of cell signaling, environmental influences

32
Q

Morphogenesis

A

Processes by which order the developing organism is created

33
Q

Major morphogenetic processes in early embryology:

A

Cell division
Condensation
Cell Death
Migration
Matrix secretion and Degradation
Growth

34
Q

Signaling pathways for differentiation of cell types during Embryogenesis

A

Transcription factors and gene expression
Morphogens
Notch/Delta

35
Q

Transcription factors

A

Hox/Homebox proteins, Pax, Basic Helix-loop-Helix

36
Q

Hox/Homebox proteins,

A

Hox genes discovered in Drosophila melanogaster.
In humans, Hox genes along the PA axis and chromosomal location are conserved as well.
Example: Defects in HOX1A impair human neural development

37
Q

Morphogens

A

Diffusible molecules that specify which cell type will be generated at a specific anatomical location.
Morphogens also direct the migration of cells and their processes to their final destination.
Many morphogens are found in concentration gradients in the embryo and expressed in opposing gradients in the dorsoventral, anteroposterior and mediolateral axes.

38
Q

Morphogens: Retinoic Acid

A

Derived from Vitamin A; important for the anteroposterior axis.
Normally acts “posteriorize” the body plan.
Insufficient RA will lead to more anteriorized structures.
Hox genes are crucial targets of RA receptors in early development.
RA are powerful teratogens, especially during the first trimester.

39
Q

Morphogens: Hedgehogs

A

Sonic Hedgehog was the first mammalian orthodox of the Drosophila gene hedgehog.
The primary receptor for Shh is Patched (PTCH)
Shh in vertebrate development has a role in patterning the ventral neural tube. Shh is secreted at high levels by the notochord, thus providing high levels in the floor of the neural tube (promoting motor neurons).

Holoprosencephaly-fused cerebral hemispheres is a congenital disorder linked to mutations in Shh or its receptor.

40
Q

Morphogens: Transforming Growth Factor

A

Important for migration and axonal guidance.
TGF-B binds to transmembrane kinase receptors to phosphorylate intracellular receptor-associated Smad Proteins. Smad complexes regulate target gene expression in the nucleus.

TGF-B signaling is a tumor suppressor factor and inhibits cell proliferation. Its dysregulation has been implicated in cancer.

41
Q

Morphogens: Fibroblast Growth Factor

A

Influence morphogenesis in embryonic development.
Roles include cell migration, differentiation, survival, apoptosis, induction etc.
Important for formation of blood vessels

42
Q

Morphogens : Wnt/B Catenin

A

Directs cell polarity, proliferation, apoptosis, cell fate and morphogenesis (patterning the CNS, the gut, the respiratory and circulatory systems)
Also play a role in tumor formation

43
Q

Notch/Delta signaling pathway

A

Pathway is integral for cell fate determination, maintenance of stem cell niches (lateral inhibition), apoptosis, and differentiation.

Lateral inhibition- cells that are in the center differentiate meanwhile lateral cells are inhibited from differentiation and remain progenitor.

44
Q

Cell Adhesion Molecules: Catherine Super Family

A

Calcium Dependent adhesion
Also involved in cell recognition, signaling, communication, morphogenesis, angiogenesis among others

45
Q

Epithelial-Mesenchymal Transition

A

Acquisition of mesenchymal features from epithelial cells.
Occur during normal embryonic development (gastrulation)
Adult tissue regeneration
Cancer progression

46
Q

Mesenchymal-Epithelial Transition

A

Metastatic tumor cells at distant sites undergo MET

47
Q

Gestational age

A

Last normal menstrual period. Two weeks longer than the fertilization age.

Embryo (8 decks)

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