HY Embryology 8 Flashcards

Terms Definitions
When is the embryonic period?
Week 3-8
Describe Spermiogenesis
1. Spermatids undergo a postmeiotic series of morphological changes (called spermiogenesis) to form sperm (23,1N)

2. Newly ejaculated sperm are incapable of fertilization until they undergo capacitation, which occurs in the female reproductive tract and involves the unmasking of sperm glycosyltransferases and removal of proteins coating the surface of the sperm
What hormone is used by the fetal testes as a precursor for testosterone synthesis?
Progesterone
Describe DiGeorge syndrome
1. DiGeorge syndrome occurs when pharyngeal pouches 3 and 4 fail to differentiate into the thymus and parathyroid glands

2. DiGeorge syndrome is usually accompanied by facial anomalies resembling first arch syndrome (micrognathia, low-set ears) due to abnormal neural crest cell migration, CV anomalies due to abnormal neural crest cell migration during formation of the aorticopulmonary septum, immunodeficiency due to absence of thymus gland, and hypocalcemia due to absence of parathyroid glands
From which germ cell layer does the epithelial lining of the lower anal canal derive?
Ectoderm
From which germ cell layer does the kidney derive?
Mesoderm
Describe tracheoesophageal fistulas
A tracheoesophageal fistula is an abnormal communication between the trachea and esophagus that results from improper division of foregut by the tracheoesophageal septum.
What adult arterial and venous structures develop from aortic arch 2?
Portion of Stapedial Artery
What is the epoophoron?
Vestigial remnants of the mesonephric tubules
What is gastrulation?
A process that establishes the three primary germ layers (ectoderm, mesoderm, and endoderm), thereby forming a trilaminar embryonic disk
Describe Hydroxyurea
1. A cytotoxic drug
2. has been shown to promote HbF production by the reactivation of ?-chain synthesis
3. Useful in treatment of sickle cell disease, in which the presence of HbF counteracts the low oxygen affinity of sickle Hb (HbS) and inhibits the sickling process
Describe Severe hemolytic disease
1. Fetus is severely anemia
2. Fetus demonstrates total body edema (ie hydrops fetalis)
3. May lead to death
Describe the mesonephros
1. Develops from an outgrowth of the mesonephric duct (called the uteric bud) and from a condensation of mesoderm within the nephrogenic cord called the metanephric mesoderm

2. The metanephros is the caudal-most nephric structure

3. The metanephros begins to form at week 5 and is functional in the fetus at about week 10. The metanephros develops into the definitive adult kidney
Describe Treacher Collins syndrome
1. A first arch syndrome

2. Also called mandibulofacial dysostosis

3. Characterized by underdevelopment of the zygomatic bones, mandibular hypoplasia, lower eyelid colobomas, downward-slanting palpebral fissures, and malformed external ears

4. An autosomal dominant genetic disorder caused by a mutation in the TCOF1 gene on chromosome 5q32.3-q33.1 for the treacle protein
From which germ cell layer do neurons within ganglia (dorsal root, cranial, autonomic) derive?
Neural crest (ectoderm)
What is Dandy-Walker syndrome associated with?
This syndrome is usually associated with:
1. Dilatation of the fourth ventricle
2. Posterior fossa cyst
3. Agenesis of the cerebellar vermis
4. Small cerebellar hemispheres
5. Occipital meningocele
6. Frequently agenesis of the splenium of the corpus callosum
Describe ureteropelvic junction obstruction (UPJ)
1. Occurs when there is an obstruction to the urine flow from the renal pelvis to the proximal ureter

2. UPJ is the most common congenital obstruction of the urinary tract

3. If there is severe uteropelvic atresia, a multicystic dysplasia kidney is found, in which the cysts are actually dilated calcyes. In this case the kidney consists of grape-like, smooth-walled cysts of variable size. Between the cysts are found dysplastic glomeruli and atrophic tubules
Describe ectopic thymus, parathyroid, or thyroid tissue?
1. Result from the abnormal migration of these glands from their embryonic position to their definitive adult location.

2. Glandular tissue may be found anywhere along their migratory path
What type of cell is responsible for providing a continuous supply of stem cells for sperm throughout the reproductive life of the male
Type A spermatogonia (46,2N)
Describe persistent truncus arteriosus (PTA)
1. Caused by abnormal neural crest cell migration such that there is only partial development of the AP septum
2. PTA results in a condition in which one large vessel leaves the heart and receives blood from both the right and left ventricles
3. PTA is usually accompanies by a membranous ventricular septal defect (VSD)
4. Is associated clinincally with marked cyanosis (right to left shunting of blood)
What are elevated AFP levels associated with?
-Neural tube defects (eg spina bifida or anencephaly)
-Omphalocele (allows fetal serum to leak into the amniotic fluid)
-Esophageal and duodenal atresia (which interfere with fetal swallowing)
Describe the development of the paramesonephric (Mullerian) ducts
1. The cranial portions of the paramesonephric ducts develop into the uterine tubes

2. The caudal portions of the paramesonephric ducts fuse in the midline to form the uterovaginal primordium and thereby bring together two peritoneal folds called the broad ligament

3. The uterovaginal primordium develops into the uterus, cervix, and superior one third of the vagina

4. The paramesonephric ducts project into the dorsal wall of the cloaca and induce the formation of the sinovaginal bulbs. The sinovaginal bulbs fuse to form the solid vaginal plate, which canalizes and develops into the inferior two thirds of the vagina

5. Vestigial remnants of the paramesonephric duct may be found in the adult female and are called the hydatid of Morgagni
What swellings form the face?
The face is formed by three swellings: the frontonasal prominence, the maxillary prominence (pharyngeal arch 1), and the mandibular prominence (pharyngeal arch 1)
Describe Gestational trophoblastic neoplasia (GTN) or Choriocarcinoma
1. GTN is a malignant tumor of the trophoblast that may occur following a normal or ectopic pregnancy, abortion, or a hydatidiform mole
2. With a high degree of suspicion, elevated hCG levels are diagnostic
3. Nonmetastatic GTN (ie, confined to the uterus) is the most common form of the neoplasia, and treatment is highly successful. However, the prognosis of metastatic GTN is poor if it spreads to the liver or brain
What is the villous chorion?
The part of the chorion where the villi persist and form the fetal part of the placenta.
Describe cranium bifida with meningoencephalocele
1. Occurs when the meninges and brain protrude through the skull defect and form a sac filled with CSF

2. This defect usually comes to medical attention within the infant's first few days or weeks of life

3. The outcome is poor (ie, 75% of the infants die or have severe retardation)
What do the muscles of the tongue derive from?
The intrinsic muscles and extrinsic muscles (styloglossus, hyoglossus, genioglossus, and palatoglossus) are derived from the myoblasts that migrate into the tongue region from occipital somites
From which germ cell layer do the pharyngeal arch bones derive?
Includes the maxila, mandible, maleus, and incus
Neural crest (ectoderm)
Why is ascend of the kidneys arrested with horseshoe kidneys?
The fused portion gets trapped behind the inferior mesenteric artery
Describe the development of the lung bud
1. The distal end of the respiratory diverticulum enlarges to form the lung bud

2. The lung bud divides into two bronchial buds that branch into the main (primary), lobar (secondary), segmental (tertiary), and subesegmental bronchi
Why is it crucial that a woman become aware of a pregnancy as soon as possible?
The embryoining period is a period of high susceptibility to teratogens
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