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2011.10.17 - Embryo - Weeks 3-8
Terms in this set (40)
What structures arise from the ectoderm germ layer?
P 1. nervous system 2. neural crest cells 3. portions of sensory epithelium (ear, nose, eye) 4. skin and adnexal structures 5. anterior pituitary gland
What structures arise from the mesoderm germ layer during weeks 3-4 of development?
P Three types of mesoderm develop 1. Somites [a. Sclerotome b. myotome c. dermatome of vertebrae] 2. Intermediate mesoderm [kidneys and genital system] 3. Lateral Plate Mesoderm [parietal(somatic)/visceral (splanchnic) mesoderm, dermis, and limbs] IN ALL LAYERS of EXTRA and INTRAEMBRYONIC mesoderm = angiogenesis (formation of blood vessels)
What structures arise from the endoderm germ layer?
Gastrointestinal Track [thyroid, tonsils, thymus, parathyroid -pharyngeal portion- lung, liver, pancrease, and bladder]
What cells give rise to all three germ layers?
What is the origin and migration of Neural Crest Cells? And what is their purpose?
How does the embryo fold?
Umbilicus is the ventral site where the cranial, caudal, and lateral folds join!
How does the primitive gut form?
What is gastrulation?
The forming of the three germ layers (ectoderm, mesoderm, endoderm).
When is the Embryonic Period?
Weeks 3-8 of development in which organs being to form! (organogenesis)
What is Neurulation? What are the key structural features? And what does it result in?
Ectoderm folding into neural groove. First fuses at neck and migrates cranially and caudally to form neural tube (spinal cord and brain).
What results from disruption in closure of the anterior/rostral neuropore of the neural tube during the 3-4th week of development?
1. Anencephaly (opening above brain = fetus doesn't survive) 2. Encephalocele (if small = cut off bulge, if large = loss of vision[occipital lobe] or judgement[frontal lobe]) Allow child to learn (brains are plastic and can learn thing!)
What results from disruption in closure of the posterior/caudal neuropore?
P Meningomyelocele, Spina Bifida, Meningocele
Where does the anterior pituitary gland originate from in development?
Thickening of the ectodermal layer in the orapharyngeal membrane and migrates to brain.
A chemical affecting which area of the embryonic disk is most likely to cause a heart defect?
Describe Angiogenesis (HINT: from the mesoderm).
What is the difference btw endothelium and endoderm?
Endothelium arises from the mesoderm germ layer to form lining of blood vessels. Endoderm is a germ layer that forms the GI track (and assiciated structures), lungs, bladder
When do most women discover they are pregnant, and why is this of clinical interest (for prev med)?
Most women don't discover being pregnant until 2 months (missing two menstrual cycles). They then "Eat/Act healthier," but the most important development has already occurred. Therefore, drugs/alcohol have already influenced the baby.
During what period of development are organs formed?
Embryonic Period (3-8 weeks after fertilization)
What are chemicals that alter development and produce malformations of a fetus?
Explain how the placenta exchanges nutrients and wastes with maternal blood.
Maternal sinusoid = exploded pool of capillary blood that soaks around villi (with very thin syncytiotrophoblast layer around placental vessels). Allows for exchange of nutrients, and wastes
What anchors the placenta into the uterine wall?
Cytotrophoblasts from Placental Villi!
What causes a Sacrococcygeal Teratoma?
Lack of closure of primitive streak = all three germ layers within "tumor"
What cell layer is fated to become all the tissues of the embro?
Describe diaphragm formation in development during the 3-8 weeks.
Describe lung formtaion in development during the 3-4 weeks.
What disorder results from malformation of Pleuroparitoneal folds during 3-8 weeks of development?
Diaphragmatic Hernia (results in intestines going up into the pleural cavity). This inhibits right lung (hypoplasia) and heart development. = high fatality! (in utero and post birth surgeries possible)
Is herniation of intestines into the umbilical cord normal during development?
YES (if during first trimester. They will go back into abdominal cavity.) NO (if after 1st trimester. Must be fixed!)
What are the 4 structures that form the diaphragm?
What causes Clefted Sternum?
Incomplete lateral folding of epidermal layer. Associated with Ectopia Cordis (heart outside of body)
What causes Omphalocele?
Abdominal herniation into the umbilicus (covered by amnion)(after 1st trimester). Usually associated with other chromosomal/migration abnormalities (aka Pentology of Cantrell = clefted sternum, ectopia cordis, omphalocele, diaphragmatic hernia and congenital heart defects)
What causes Gastroschisis?
Disruption of (right) abdominal wall causing shortening of gut (not covered by amnion). Easily fixed
The primitive chest cavity (future plearual cavity and pericardial cavity) connects to the abdominal cavity via the...?
What are the various stages of development from fertilization to birth?
1-3 weeks = PREGERM (baby generally not affected by mom); 3-8 weeks = EMBRYO (baby most sensitive to mom since organogenesis); 9-40 weeks = FETUS (growth in size and fat)
How can the date of brith be estimated?
40 weeks from last menstrual cycle; 38 weeks of gestation (conception)
How do babies Crown-Rump-Length (CRL) change over development?
Head gets relatively smaller as baby develops.
What catagorizes a baby as Premature?
What catagorizes a baby as Postmature?
What occurs in the 3rd trimester (4)?
Fat accumulation, Respiratory maturation, Swallowing/sucking, Eye development
What occurs in the 2nd trimester?
Rapid growth of organs and body
What occurs in the 1st trimester?
Gastrulation (formation of 3 germ layers) and Organogenesis
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