Embryology Flashcards
What is the zona pellicuda?
The ECM of the egg essential for sperm binding. When the embryo reaches the uteris it hatches from the zona pellicuda which was intially preventing it from binding to the uterine wall
What is the blastocoel
It is the fluid within the blastocyst
What process is necessary to form the blastocyst from the morula?
Cavitation which results in the production of the trophoblast (outer cell layer) and the ICM (inner cell mass)
What is the endomertrium?
It is the epithelium of the uterus and is the site of implantation of the embryo
L-selectins are involved in what?
Blastocyst attachment to the endometrium
What is an ectopic pregnancy?
It is an abnormal implantation of the blastocyst not in the uterus
What are the two cellular layers that the trophoblast forms?
The cytotrophoblast (an inner layer of mononucleated cells) and the **syncytiotrophoblast **an outer multinucleated layer that lacks distinct cell boundaries and invades the uterine tissue
What are the two layers of tissue that the ICM differentiates into?
Hypoblast (supportive) and the Epiblast (main embryo)
Gastrulation results in what?
The formation of the endoderm, mesoderm and ectoderm
The endoderm gives rise to which tissues?
The inner lining of the get and other internal organs
The ectoderm gives rise to which tissues?
The skin, nervous system and other external tissues
The mesoderm gives rise to what?
Muscle, skeletal system, and circulatory system
What are the steps of neurulation?
- formation and folding of the neural plate
- Elevation of the neural crest
- Convergence of the neural folds
- Closure of the neural tube
What are the three major divisions formed during neuralation?
- Neural tube: forms brain and spinal cord
- External surface ectoderm: forms skin
- Neural Crest Cells: gives rise to many cell types
What are the four main derivatives of neural crest cells?
- Cranial: craniofacial cartilage, bone, neurons, glia and connective tissue
- Cardiac neural crest: malenocytes, neurons, cartilage and connective tissue. And septum
- Trunk neural crest: dorsal root ganglia (sensory) or sympathetic ganglia and adrenal medulla
- Enteric (vagal and savral) neural crest: parasympathetic ganglia of gut
What is a homologous gene?
A gene similar in structure and evolutionary origin (and likely function) toa gene in another species
Explain genetic equivalence?
All cells contain the same genetic material, but the expression pattern is different within each.
Explain differential gene expression
The cells contain the same genetic material, but different cell types express different sets of genes
What are the various levels at which genetic expression is regulated?
Transcription, nuclear RNA processing, selective mRNA translation, differential protein modification
Explain induction
one group of cells changes the behavior of an adjacent set of cells
What does it mean to have a competent cell?
That the responder cell can effectively change its behavior for a particular inducer. For example, Pax6 is required for to form the optic cup
What’s the difference between juxtacrine and paracine signaling?
A juxtacrine signal exists when two cells are in direct contact with one another, a paracrine signal can diffuse throughout the extracellular space
What is a morphogen?
It is a special type of paracrine signaling molecule whose effect depends on concentation
What is volvulus?
Twisted bowel that causes obstruction
What is heterotaxy?
Also known as situs ambiguus is a congenital deformity resulting in nonuniform left right assymmetry where certain organs are reversed in their left-right orientation
Difference between situs solitus and situs inversus?
Situs solitus: when the body is in the normal orientation
situs inversus: a total flip flop of left right symmetry
What is aneuploidy?
An abnormal number of chromosomes
What is axenfeld-reiger syndrome?
It is primarily an eye disorder, but can affect other parts of the body. It is inherited in an autosomal dominant pattern.
2 known genes: PITX2, FOXC1
caused by a single mutation
Children usually have microdontia, olidgodontia, hypertelorism, redundant periumbilical skin
What is multifactorial inheritance?
Meaning both genetic and environmental factors are important.
What is holoprosencephaly (HPE)?
It is the most common malformation of the brain, can result from chromosomal abnormalities or environmental factors: results in incomplete forebrain division in the 3rd-4th weeks of gestation.
Associate with SHH
What is phocomelia?
A limb defect: a consequence of thalidomide use during pregnancy
What is a teratogen?
An agent which causes birth defects
e.g. thalidomide
Which embryonic period is most susceptible to birth defects?
Weeks 3-8
Which organ has the most common birth defects?
The heart.
What is dextrocardia
When the heart is formed on the right side ofhte thorax instead of left
What is double outlet right ventricle?
When the aorta rises out of the right ventricle instead of the left ventricle.
What is transposition of the great arteries?
When the aorta and the pulmonary artery switch positions
Oxygen poor blood enters the right side of the heart, then instead of being oxygenated, gets pumped through the rest of the body.
What is truncus arteriosus (22q11.2Syndrome)?
When the main pulmonary artery (MPA) and the aorta fail to separate, so you have a single large valve coming out of the heart
What are the four defects involved with the Teratology of Fallot (22q11.2 syndrome)?
- Ventricular septal defect (VSD)
- Pulmonary Stenosis
- Overriding aorta (increases flow)
- Ventricular Hypertrophy
Cardiac neural crest cells contribute to what in development?
Separation of the cardiac outflow tract
