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Questions and Answers
What is the definition of 'Aplasia'?
What is the definition of 'Aplasia'?
Which of the following is an example of a gonosomal chromosomal aberration?
Which of the following is an example of a gonosomal chromosomal aberration?
What process allows the blastocyst to leave the zona pellucida?
What process allows the blastocyst to leave the zona pellucida?
What term describes the underdevelopment of fetal mass?
What term describes the underdevelopment of fetal mass?
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Which genetic factor can lead to malformations in subsequent generations?
Which genetic factor can lead to malformations in subsequent generations?
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Where does implantation primarily occur within the uterus?
Where does implantation primarily occur within the uterus?
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What condition develops if implantation occurs close to the cervix?
What condition develops if implantation occurs close to the cervix?
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Trisomy 18 is commonly associated with which condition?
Trisomy 18 is commonly associated with which condition?
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What is the primary role of the digestion enzymes released during implantation?
What is the primary role of the digestion enzymes released during implantation?
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What is the characteristic feature of 'Hypoplasia'?
What is the characteristic feature of 'Hypoplasia'?
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At what point does implantation typically conclude?
At what point does implantation typically conclude?
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Which of the following best describes 'Ectopia'?
Which of the following best describes 'Ectopia'?
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What is referred to as the functional layer of the endometrium during pregnancy?
What is referred to as the functional layer of the endometrium during pregnancy?
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What classification do teratogens belong to in terms of environmental factors?
What classification do teratogens belong to in terms of environmental factors?
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What type of decidua is located between the conceptus and the uterine cavity?
What type of decidua is located between the conceptus and the uterine cavity?
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What is the term for implantation of an embryo outside the uterus?
What is the term for implantation of an embryo outside the uterus?
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What regulates the formation of actin and myosin in muscle development?
What regulates the formation of actin and myosin in muscle development?
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What is the primary function of primary chorionic villi?
What is the primary function of primary chorionic villi?
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Which type of muscle fibers can change in response to plasticity?
Which type of muscle fibers can change in response to plasticity?
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When does the development of chorionic villi begin during embryonic development?
When does the development of chorionic villi begin during embryonic development?
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What structures develop into the hypaxial muscles of the trunk?
What structures develop into the hypaxial muscles of the trunk?
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What type of tissue is added to secondary chorionic villi?
What type of tissue is added to secondary chorionic villi?
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Which embryonic source does cardiac muscle primarily derive from?
Which embryonic source does cardiac muscle primarily derive from?
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What characterizes tertiary chorionic villi?
What characterizes tertiary chorionic villi?
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Which of the following is NOT one of the sources that contribute to the development of the diaphragm?
Which of the following is NOT one of the sources that contribute to the development of the diaphragm?
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What is the chorion leave?
What is the chorion leave?
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Which muscle is innervated by the dorsal branches of spinal nerves?
Which muscle is innervated by the dorsal branches of spinal nerves?
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What role does the cytotrophoblastic cell column play in placental development?
What role does the cytotrophoblastic cell column play in placental development?
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How is the allantochorion formed?
How is the allantochorion formed?
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What are the specialized muscle cells that form the conducting system of the heart characterized by?
What are the specialized muscle cells that form the conducting system of the heart characterized by?
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What is the condition of chorionic villi by week 8 of development?
What is the condition of chorionic villi by week 8 of development?
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Which type of muscle fibers is primarily influenced by the migrating neural crest cells during development?
Which type of muscle fibers is primarily influenced by the migrating neural crest cells during development?
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What directs the development of angioblasts from mesoderm?
What directs the development of angioblasts from mesoderm?
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Which process involves the growth of new blood vessels after the formation of a primary capillary plexus?
Which process involves the growth of new blood vessels after the formation of a primary capillary plexus?
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What is the primary role of platelet-derived growth factors (PDGF) in embryonic development?
What is the primary role of platelet-derived growth factors (PDGF) in embryonic development?
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What structures return blood to the embryo's heart?
What structures return blood to the embryo's heart?
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Which factors are essential for both vasculogenesis and angiogenesis?
Which factors are essential for both vasculogenesis and angiogenesis?
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When does the intraembryonic blood circulation begin?
When does the intraembryonic blood circulation begin?
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What is the contribution of neural crest cells in heart development?
What is the contribution of neural crest cells in heart development?
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Which structure remains attached to the posterior wall of the pericardial cavity via dorsal mesocardium?
Which structure remains attached to the posterior wall of the pericardial cavity via dorsal mesocardium?
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Study Notes
Development Malformations
- Agenesis - Total absence of an organ or structure
- Aplasia - Failure to develop a functioning organ
- Atresia - Absence of an opening
- Dyschromia - Disorders in developmental time
- Ectopia - Atypical localization of organs
- Heterotrophia - Presence of an organ in an atypical position
- Hypoplasia - Underdeveloped organ or structure in size and mass
- Hypotrophia - Underdeveloped fetal mass
- Macrosomia - Increase in body length
Ethological Factors for Developmental Malformations
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Malformations result when disturbing factors exceed the threshold of ontogenic adaptation.
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Genetic factors:
- Mutagens affecting fetal germ cells cause congenital malformations in future generations.
- Examples include ionized radiation (X-rays) and many chemicals.
- Mutations of somatic cells may result in malformations or tumors, not inherited.
- Chromosomal abnormalities:
- Occur in numerical or structural aberrations, causing severe malformations.
- Often result in spontaneous abortion or death after birth.
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Numerical:
- Human karyotype: 46XX (female) or 46XY (male)
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Gonosomal aberrations (sex chromosome abnormalities):
- Monosomy: One sex chromosome, most aborted. Vital forms are females with Turner's syndrome.
- XXY-trisomy: Klinefelter syndrome - male with small testes, azoospermia, defective masculinity.
- XYY-trisomy: "Supermen," aggressive behavior, lesser intelligence.
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Autosomal aberrations (number of autosomes):
- Some forms of trisomy (2n+1) result in different syndromes:
- Trisomy 21: Down syndrome (1/1000 births)
- Trisomy 18: Edwards syndrome (abortion; mean survival 2 months)
- Some forms of trisomy (2n+1) result in different syndromes:
- Occur in numerical or structural aberrations, causing severe malformations.
- Mutagens affecting fetal germ cells cause congenital malformations in future generations.
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Environmental factors:
- All spaces outside the chromosomes (intercellular, extracellular, placenta, maternal, external environment)
- Human teratogens: Substances causing congenital malformations, divided into biological, chemical, and physical factors.
Implantation and Early Embryonic Development
- Blastocyst leaves the zona pellucida by digesting a hole with a trypsin-like enzyme on the 5th day after fertilization.
- Implantation occurs in the anterior or posterior wall of the uterus.
- Placenta previa: Implantation near the cervix uteri, requiring monitoring with ultrasound and potential intervention.
- Trophoblast attaches to the endometrium, and implantation begins approximately 5-6 days after fertilization.
- Digestive enzymes are crucial for forming a niche in the endometrium, replacing it with digested maternal tissue and blood, providing nutrients for the embryo.
- Implantation ends around the 13.5th day, with the conceptus fully covered by the endometrium.
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Functional layer of the endometrium during pregnancy is called decidua, with three types:
- Decidua capsularis: Endometrial tissue between the conceptus and the uterine cavity.
- Decidua basalis: Endometrial tissue between the conceptus and the basal part of the functional endometrium (placental site).
- Decidua parietalis: All other layers of the functional endometrium.
- Decidua cells initially provide trophic function for the embryo.
- Peripheral trophoblasts invade the basal decidua.
- Ectopic pregnancy: Embryo implants outside the uterus, often in the fallopian tubes, abdominal cavity, ovaries, or cervix.
Bilaminar Embryo, Extraembryonic Mesoderm, and Chorion
- Bilaminar embryo: Consists of the epiblast and hypoblast.
- Extraembryonic mesoderm: Connects bilaminar embryo to chorion.
- Chorion (fetal membrane): Formed from syncytiotrophoblasts during implantation.
- Chorion cavity surrounds the bilaminar embryo, amnion, and yolk sac.
- Chorio-amniotic membrane: Fusion of amnion and chorion around the 6th week.
- Placentation starts on day 13, with villus development beginning in the second week.
Chorionic Villi
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Primary chorionic villi: Consists of syncytiotrophoblast and cytotrophoblast, migrating into the endometrium. Maternal blood flows in lacunae (spaces in the endometrium).
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Secondary chorionic villi: Contain extraembryonic mesoderm of the chorion.
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Tertiary chorionic villi: Developed when mesenchymal cells differentiate into blood capillaries.
- These capillaries connect with the blood vessels in the allantois, joining the intraembryonic blood vessels.
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Chorionic villi covering: Until the 8th week, villi cover the entire surface of the chorion. Later they become atrophic on the side towards the uterine lumen, becoming the chorion leave (smooth chorion).
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Chorion frondosum (villous chorion): Villi at the embryonic pole increase rapidly in size.
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Chorionic plate: Connects both chorions, consisting of amniotic columnar epithelium, extraembryonic mesoderm, blood vessels, cyto- and syncytiotrophoblast (or fibrinoid after the 4th embryonic month).
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Cytotrophoblastic cell column: Terminal portion of villi remains trophoblastic, with proliferation buds that spread across the placenta. These buds can detach and enter maternal blood, often reaching the lungs before expiring.
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Anchor villi: Attachment of tertiary villi by growing cytotrophoblasts at the decidua basalis.
Allantochorion and Umbilical Cord Development
- Allantochorion: Compound membrane formed by fusion of the allantois and chorion.
- Allantois: Used for waste products.
- Chorion: Forms villi/placenta.
- Insulin-related growth factor: Regulates the formation of actin and myosin in muscles.
- Myotubes: Form from primary myotubes during fetal development. Secondary myotubes differentiate around the primary ones.
- Muscle fibers: Phenotypes depend on specific proteins, including light and heavy myosin chains.
- Plasticity: Phenotypes are not fixed and can change (hypertrophy, atrophy, and denervation).
Muscle Development in Different Regions
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Trunk muscles: Develop from myotomes, divided into epimers and hypomers.
- Epimers: Produce epaxial muscles (extensors of the vertebral column)
- Hypomers: Produce hypaxial muscles (flexors of the trunk), forming three layers.
- Dorsal branches of spinal nerves: Innervate epimer muscles.
- Ventral branches of spinal nerves: Innervate hypomer-derived muscles.
- Head muscles: Develop from cranial somites (tongue muscles), prechordal mesoderm (external eyeball muscles), and branchial arches 1-4 (masticatory, facial, and pharyngeal muscles).
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Smooth muscles: Derive from lateral mesoderm (except for the sphincter and dilatator pupillae muscles).
- Splanchnopleura: Mesenchymal cells form smooth musculature of the intestine.
- Local mesoderm: Differentiates into smooth musculature of blood vessels.
- Heart musculature: Derives from splanchnopleura.
Development of Muscles in Inner Organs, Heart, Body, Viscera, Limbs, and Diaphragm
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Cardiac muscle: Develops from splanchnic mesoderm that envelops the endothelial heart tube.
- Myoblasts adhere, forming intercalated discs at their junctions.
- Conducting system: Formed by special muscle cells with irregular distribution of myofibrils.
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Diaphragm: Develops from four sources:
- Septum transversum: Central tendon
- Mesentery of the esophagus: Crura of the diaphragm
- Pleuroperitoneal membranes: Lateral parts of the diaphragm
- Separate blood vessels in the embryo join those in the extraembryonic mesenchyme.
Angiogenesis and Vasculogenesis
- Angioblasts: Vascular precursors that organize the primary capillary plexus via vasculogenesis.
- Angiogenesis: Growth of new blood vessels, continuing into postnatal life.
- Vascular endothelial growth factor 2 (VEGF-2): Important for angioblast development from mesoderm, under the influence of VEGF-A.
- Angiopoietin 1: Key for angiogenesis.
- Platelet-derived growth factors (PDGF): Released by endothelial cells, stimulating mesenchymal cell migration near vascular walls.
- Transforming growth factor beta: Stimulates mesenchymal cells to become smooth muscle cells or pericytes.
Early Embryonic Circulation
- Precardinal veins and postcardinal veins: Return blood to the embryo's heart.
- Vitelline veins: Transport blood from the yolk sac.
- Umbilical veins: Transport blood from the placenta.
- Dorsal arteries: Two appear initially, but fuse in the caudal half of the embryo to form a single dorsal aorta.
- Intraembryonic blood circulation: Starts with the first heart pulsation on day 22.
Heart Development
- Cardiogenic area: Mesenchyme cells form this area in front of the prechordal plate on day 17, 18, and 19.
- Endocardial tubes: Cords of cells spread out from the splanchnomesoderm and become canalized, producing two endocardial tubes.
- Single endothelial tube: The two endocardial tubes fuse with the transversal folding of the embryonic disc.
- Pericardial cavity: Cephalocaudal flexion incorporates the endothelial tube into the pericardial cavity, but the tube remains attached to the posterior wall by the dorsal mesocardium.
- Outflow tract: Major components derive from neural crest, but endothelial components arise from paraxial and lateral mesoderm.
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Description
Test your knowledge on the various types of developmental malformations, including agenesis, aplasia, and others. Also, explore the etiology behind these conditions, focusing on genetic factors and environmental influences. This quiz is ideal for students studying developmental biology or medicine.
