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Questions and Answers
What is the primary focus of teratology within embryology?
What is the primary focus of teratology within embryology?
- Examining malformations that occur during embryonic development (correct)
- Analyzing postnatal development of infants
- Investigating environmental factors leading to birth defects
- Studying the genetic factors of embryonic development
Which historical view of malformations was prevalent in pre-medieval times?
Which historical view of malformations was prevalent in pre-medieval times?
- Monsters were thought to be products of environmental factors.
- Birth defects were considered a positive sign of happiness. (correct)
- Congenital defects were associated with divine punishment.
- Malformations were seen as evidence of genetic mutations.
What is the term used to describe the phenomenon of light marks of peculiar development in embryology?
What is the term used to describe the phenomenon of light marks of peculiar development in embryology?
- Stigma (correct)
- Malformation
- Teratogen
- Mutation
Which drug is associated with causing malformations of the ears?
Which drug is associated with causing malformations of the ears?
Which of the following congenital malformations is linked to maternal diabetes?
Which of the following congenital malformations is linked to maternal diabetes?
What growth condition can result from maternal alcoholism during pregnancy?
What growth condition can result from maternal alcoholism during pregnancy?
Which environmental factor can lead to fetal stress that may cause malformations?
Which environmental factor can lead to fetal stress that may cause malformations?
What is indicated by the incidence range of 2.0-5.6% of all births?
What is indicated by the incidence range of 2.0-5.6% of all births?
At what stage is the conceptus referred to as a morula after fertilization?
At what stage is the conceptus referred to as a morula after fertilization?
What structure develops from the trophoblasts around the dark cells in the morula stage?
What structure develops from the trophoblasts around the dark cells in the morula stage?
What is the primary purpose of the syncytiotrophoblast layer during implantation?
What is the primary purpose of the syncytiotrophoblast layer during implantation?
What role do sodium/potassium ATPases play in the formation of the blastocyst?
What role do sodium/potassium ATPases play in the formation of the blastocyst?
What is the significance of the three different decidua during pregnancy?
What is the significance of the three different decidua during pregnancy?
When does the zona pellucida typically rupture during embryo development?
When does the zona pellucida typically rupture during embryo development?
Where should implantation ideally occur in the uterus?
Where should implantation ideally occur in the uterus?
What is the decidua basalis associated with during pregnancy?
What is the decidua basalis associated with during pregnancy?
What differentiates the timing of meiosis initiation between oogenesis and spermatogenesis?
What differentiates the timing of meiosis initiation between oogenesis and spermatogenesis?
How do gamete differentiation processes differ in oogenesis and spermatogenesis?
How do gamete differentiation processes differ in oogenesis and spermatogenesis?
Which of the following statements about the outcome of meiotic divisions in oogenesis and spermatogenesis is correct?
Which of the following statements about the outcome of meiotic divisions in oogenesis and spermatogenesis is correct?
What is true about the cell cycle and meiosis completion in oogenesis and spermatogenesis?
What is true about the cell cycle and meiosis completion in oogenesis and spermatogenesis?
Which temperature is optimal for the processes of oogenesis and spermatogenesis?
Which temperature is optimal for the processes of oogenesis and spermatogenesis?
In what manner do the chromosomes behave during the meiotic prophase in oogenesis compared to spermatogenesis?
In what manner do the chromosomes behave during the meiotic prophase in oogenesis compared to spermatogenesis?
Which of the following statements about the initiation and development of oocytes and spermatozoa is true?
Which of the following statements about the initiation and development of oocytes and spermatozoa is true?
What is the role of Sertoli cells in the process of spermiohistogenesis?
What is the role of Sertoli cells in the process of spermiohistogenesis?
At which embryonic month does the neurocranium begin its development?
At which embryonic month does the neurocranium begin its development?
Which of the following bones is NOT formed by endochondral ossification?
Which of the following bones is NOT formed by endochondral ossification?
What is the fate of the anterior fontanelle?
What is the fate of the anterior fontanelle?
Which of the following bones is specifically formed through intermembranous ossification in the viscerocranium?
Which of the following bones is specifically formed through intermembranous ossification in the viscerocranium?
What is the typical characteristic of the ossification process of the limb bones?
What is the typical characteristic of the ossification process of the limb bones?
At what age does the posterior fontanelle typically ossify?
At what age does the posterior fontanelle typically ossify?
Which ossification type is characteristic for ossicles such as malleus, incus, and stapes?
Which ossification type is characteristic for ossicles such as malleus, incus, and stapes?
Which bones are formed by desmogenic processes?
Which bones are formed by desmogenic processes?
What is the role of prostaglandin E2 and prostaglandin I2 in the fetal circulation?
What is the role of prostaglandin E2 and prostaglandin I2 in the fetal circulation?
At what embryonic week does the lymphatic system begin to develop?
At what embryonic week does the lymphatic system begin to develop?
Which of the following structures does not change in postnatal life?
Which of the following structures does not change in postnatal life?
What is the outcome of improper septation during heart development?
What is the outcome of improper septation during heart development?
Which factor is NOT typically associated with heart development?
Which factor is NOT typically associated with heart development?
Which congenital anomaly involves the presence of an open ventricular septum?
Which congenital anomaly involves the presence of an open ventricular septum?
Which stage of heart development includes the folding of the embryo?
Which stage of heart development includes the folding of the embryo?
What does the umbilical vein become after birth?
What does the umbilical vein become after birth?
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Study Notes
Teratology and Embryology
- Teratology is the study of birth defects.
- Ontogenesis refers to the development of an organism from fertilization to adulthood.
- Experimental embryology involves manipulating embryos to study development.
- Stigma in embryology indicates slight developmental abnormalities, often considered signs of unique features.
- Teratogens are substances that can induce congenital malformations.
Causes of Congenital Malformations
- Genetic factors: mutagenic responses to radiation, chemicals, and chromosomal abnormalities.
- Environmental factors:
- Drugs: thalidomide (ear malformations), warfarin (nose hypoplasia), tetracycline (enamel dysplasia)
- Maternal conditions: diabetes (heart defects), alcoholism (fetal alcohol syndrome)
- Intrauterine infections: toxoplasmosis, CMV, rubella (oligohydramnios)
- Physical factors: noise, vibration, radiation
- Hypoxia: fetal stress leading to malformations
Gametogenesis
- Oogenesis: female gamete formation.
- Meiosis initiated once in a finite population of cells.
- One gamete produced per meiosis.
- Completion of meiosis delayed for months or years.
- Differentiation occurs while diploid.
- All chromosomes exhibit equivalent transcription and recombination.
- Oogenesis occurs at normal body temperature.
- Unequal divisions, oocytes only mature after fertilization.
- Begins before birth.
- All ova are present at birth.
- Oocytes are immotile.
- Spermatogenesis: male gamete formation.
- Meiosis initiated continuously in a mitotically dividing stem cell population.
- Four gametes produced per meiosis.
- Meiosis completed in days or weeks.
- Differentiation occurs while haploid.
- Sex chromosomes excluded from recombination and transcription.
- Spermatogenesis occurs at 33.6 degrees Celsius.
- Equal divisions, spermatozoa are mature cells.
- Begins at puberty.
- Spermatozoa develop at puberty and onwards.
- Spermatozoa are motile.
Spermiohistogenesis
- Spermiogenesis occurs while cells are attached to Sertoli cells via gap junctions.
- Four phases: Golgi phase, cap phase, acrosome phase, maturation phase.
- Golgi phase: spermatids develop polarity and the Golgi apparatus forms enzymes that will become the acrosome.
Morula and Blastocyst
- Morula: a solid ball of 16-32 blastomeres formed at day 4 after fertilization.
- Trophoblast: outer cells of the morula that will develop into the placenta and membranes.
- Embryoblast: inner cells of the morula that will become the embryo.
- Blastocyst: formed as fluid enters the morula, creating a blastocoel (fluid-filled cavity).
- Embryonic pole: where the embryoblast is located.
- Aembryonic pole: the opposite side of the blastocyst.
Implantation
- Implantation typically occurs in the anterior or posterior wall of the uterus.
- Syncytiotrophoblast: a layer that develops from the trophoblast and secretes enzymes to penetrate the endometrium.
- Decidua: the functional layer of the endometrium during pregnancy.
- Decidua capsularis: closest to the uterine cavity.
- Decidua basalis: at the placental site.
Cranial Ossification
- Neurocranium: develops from three cartilaginous laminae.
- Base of the skull.
- Nasal cavity.
- Ear region.
- Forms os occipitale, os temporale, os sphenoidale.
- Some neurocranial bones incorporate membraneous elements: os parietalis, os temporalis (pars squamosa), os frontale, parts of os occipitalis.
- Viscerocranium: forms at the 3rd month of embryonic development.
- Develops from intermembraneous ossification.
- Forms os zygomaticus, nasale, vomer, maxilla, mandibula, lacrimale, palatinum, tympanic ring.
Fontanellae
- Fontanellae: unossified membranes in the cranium.
- Anterior fontanelle: between two frontal and two parietal bones, closes at 1.5 years.
- Posterior fontanelle: between the occipital bone and the two parietal bones, ossifies at 1 year.
- Lateral fontanellae: between frontal, parietal, and temporal bones, ossifies at 3 years.
Limb Skeleton Development
- Limb skeleton develops through endochondral ossification under the influence of BMP.
Newborn Circulation Changes
- Ductus venosus, ductus arteriosus: their potency is maintained by prostaglandin E2 and I2 influenced by NO.
- Changes occur after birth:
- Closing of foramen ovale.
- Closing of ductus arteriosus --> lig.arteriosus.
- Umbilical arteries form plica.
- Umbilical vein --> lig.teres uteri.
Lymphatic System Development
- Develops in the 5th week of embryonic development.
- Lymphatic capillaries: develop from anastomizing perivascular spaces under the influence of VEGF-3.
- Six lymphatic sacs develop at week 6:
- Jugular lymph sacs.
- Retroperitoneal sac.
- Cisternae chyli.
- Posterior lymph sacs (transform into sinus lymphaticus iliacus/inguinalis).
- Collecting lymph vessels: connect these sacs by week 9.
- Ductus thoracicus: connects cisternae chyli with the junction of v.subclavia and v.jugularis interna.
Lymph Nodes Development
- Develop in locations where lymph sacs fold and are infiltrated by a capillary network.
- Components:
- Vas afferentes.
- Subcapsular sinus.
- Vas efferens.
- Capsule: formed by surrounding mesenchyme.
- Germinative centers: appear after first sensitization to antigen.
Heart Development
-
Critical periods:
- Fusion of endocardial tubes.
- Folding of the embryo.
- Septation of atria and ventricles.
- Development of valves.
- Development of truncoconal region.
-
Factors influencing heart development:
- Dynamic blood pressure.
- Apoptosis.
- Migration of neural crest cells.
Heart and Circulatory Anomalies
- Open ventricular sept (foramina interventricularis).
- Arterial sept defects: open foramen ovale.
- Truncus arteriosus persistance: incomplete septation of truncus arteriosus.
- Tetralogy of Fallot: hypertrophy of left ventricle, stenosis of pulmonary arteries, ventricular sept defect, right formed aorta.
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