Week 2: Making Babies

LH (luteinizing hormone) is responsible for causing follicular rupture and ovulation. It is a hormone released by the pituitary gland and plays a crucial role in the menstrual cycle. LH surge triggers the release of a mature egg from the ovary, which is essential for fertilization and conception to occur. Therefore, an increase in LH levels leads to follicular rupture and ovulation.

The future somite is derived from paraxial mesoderm formed to the side of the notochord.

A teratogen is an environmental agent that can cause developmental disruptions when a pregnant woman is exposed to it. These disruptions can result in birth defects or other abnormalities in the developing fetus. Teratogens can include substances such as drugs, chemicals, infections, or radiation. Maternal exposure to teratogens during critical periods of fetal development can have long-lasting effects on the child's health and development. It is important for pregnant women to be aware of potential teratogens and take necessary precautions to avoid exposure.

The number of ultrasounds taken does not affect fetal growth. Ultrasounds are a diagnostic tool used to monitor the development and health of the baby during pregnancy, but they do not directly impact fetal growth. Factors such as glucose and insulin availability, amino acids, alcohol consumption and smoking, and the genetic makeup of the baby can all have significant effects on fetal growth and development.

Babies born around the 26th week of pregnancy have a higher chance of survival compared to those born earlier. At this stage, the baby's vital organs are more developed, allowing them to breathe on their own with medical assistance. They may still require intensive care and support, but their chances of survival and long-term health outcomes are significantly improved compared to babies born earlier in the pregnancy.

At the end of the second week of development, both the epiblast and hypoblast layers are present in the embryonic disc. The epiblast is the upper layer of the disc and gives rise to the three primary germ layers: ectoderm, mesoderm, and endoderm. The hypoblast is the lower layer and contributes to the formation of the extraembryonic structures. These two layers play crucial roles in the early development of the embryo.

Sacroccoygeal teratomas are caused by posterior remnants of the primitive streak. The primitive streak is a structure that forms during embryonic development and is involved in the formation of the body's midline structures. When remnants of the primitive streak persist in the sacroccoygeal region, it can lead to the development of sacroccoygeal teratomas, which are tumors that contain tissues from all three germ layers. These tumors typically occur at the base of the tailbone and can vary in size and severity.

During embryonic development, the bones of the face are formed by neural crest cells from the 1st and 2nd pharyngeal arches. These neural crest cells migrate and differentiate into various types of cells, including osteoblasts, which are responsible for bone formation. The neural crest cells from these specific arches give rise to the bones of the face, such as the maxilla, mandible, and zygomatic bones. This process is crucial for the proper development and structure of the facial bones.

The syncytiotrophoblast is responsible for invading the uterus during pregnancy. It forms the outer layer of the blastocyst and plays a crucial role in implantation. This specialized layer of cells secretes enzymes that help to break down the uterine lining, allowing the blastocyst to attach and establish a connection with the mother's blood supply. The syncytiotrophoblast also forms the outer layer of the placenta and is involved in nutrient and gas exchange between the mother and the developing fetus.

Based on the given information, the woman is at high risk due to a family history of neural tube defect. Therefore, it is recommended that she undergo prenatal screening techniques to evaluate the baby's condition and take appropriate measures if necessary.

HOX genes are responsible for the regulation of body segment development during embryogenesis. Abnormal expression of HOX genes can lead to developmental abnormalities, including the shifting of the forelimb one segment cranially. Therefore, the abnormal expression of HOX genes is likely the cause of this abnormality. BMPs, sonic hedgehog, TGF-Beta, and FGFs are also involved in limb development, but they are not specifically associated with the shifting of the forelimb segment.

The formation of the primitive streak is the initial morphological change that occurs prior to gastrulation. The primitive streak is a structure that forms in the early embryo and serves as the site of cell migration and differentiation during gastrulation. It marks the beginning of the process where the three germ layers (ectoderm, mesoderm, and endoderm) form, which is a crucial step in embryonic development.

During the first 1-5 weeks after fertilization, the woman most likely contracted rubella. This is because rubella infection during this early stage of pregnancy is known to cause cardiac defects in the baby.

Homeobox genes are a group of genes that play a crucial role in the development of organisms. They are not expressed in flies or humans exclusively, nor do they cause epithelial to mesenchymal transitions. However, homeobox genes do regulate the migration of neural crest cells and are involved in the patterning of the cranial-caudal axis, including segmentation. This means that they are responsible for organizing the body plan and determining the placement of different body segments during embryonic development.

Melanocytes are pigment-producing cells that are responsible for the coloration of the skin, hair, and eyes. These cells are derived from neural crest cells, which are a group of cells that originate from the embryonic ectoderm. During development, neural crest cells migrate and differentiate into various cell types, including melanocytes. This explains why melanocytes are derived from neural crest cells rather than mesoderm, endoderm, ectoderm, or dermis.

The urogenital system is formed from the intermediate mesoderm. This layer of mesoderm gives rise to the kidneys, gonads, and reproductive ducts. These structures are essential for the formation and function of the urinary and reproductive systems in the body. The other options, such as endoderm, lateral plate mesoderm, splachnic layer, and axial mesoderm, do not directly contribute to the formation of the urogenital system.

Genomic imprinting refers to the phenomenon where certain genes are expressed differently depending on whether they are inherited from the mother or the father. This is due to epigenetic modifications, such as DNA methylation, that occur during gametogenesis. These modifications result in the silencing or activation of specific genes in a parent-of-origin specific manner. Genomic imprinting plays a crucial role in development and can lead to diseases when disrupted. Therefore, the correct answer is genomic imprinting.

False, this results in 2 placentas and 2 amniotic cavities almost never seen in identical twins; this pattern is diagnostic of fraternal twins.

The splitting of the lateral plate mesoderm forms the intraembryonic cavity. This cavity is located within the developing embryo and is surrounded by the layers of the lateral plate mesoderm. It is an important space where various organs and tissues will develop during embryogenesis. The formation of the intraembryonic cavity is a crucial step in the early development of the embryo, allowing for the proper organization and differentiation of cells and tissues.

Between weeks 14-16 of pregnancy, a fetus can be determined to be male or female via ultrasound. During this time, the external genitalia of the fetus has developed enough to be visible on the ultrasound image, allowing the healthcare provider to identify the gender. This is a common milestone in prenatal care and can be an exciting moment for expectant parents.

During fetal development, erythropoiesis, the production of red blood cells, occurs in different organs. Initially, erythropoiesis takes place in the liver, where the fetus produces red blood cells. As the fetus continues to develop, the spleen becomes the primary site of erythropoiesis. Finally, towards the end of fetal development and after birth, erythropoiesis shifts to the bone marrow, which becomes the main site of red blood cell production in adults. Therefore, the correct sequence of erythropoiesis sites in a fetus is liver to spleen to bone marrow.

The cytoplasm of the egg has the ability to reprogram genes, which means it can change the expression of certain genes in a way that allows the development of pluripotent stem cells. Pluripotent stem cells have the potential to differentiate into any type of cell in the body, making them highly valuable for medical research and potential therapies. This reprogramming ability is unique to the cytoplasm of the egg and is not found in nuclei derived from adult tissues.

During weeks 17-20 of pregnancy, brown fat, quickening (the first fetal movements felt by the mother), and vernix caseosa (a protective coating on the baby's skin) start to appear. These developments indicate the progression of the pregnancy and the growth and development of the fetus.

Congenital megacolon, also known as Hirschsprung's disease, is caused by abnormal neural crest cell migration. Neural crest cells are responsible for the formation of the enteric nervous system, which controls the movement of the intestines. In individuals with Hirschsprung's disease, these cells fail to migrate properly, leading to a lack of innervation in certain segments of the bowel. This results in a functional obstruction and the accumulation of stool, leading to the enlargement of the colon (megacolon).

The pons and cerebellum are derivatives of the metencephalon. The metencephalon is one of the five major divisions of the developing brain, and it is responsible for the development of structures such as the pons and cerebellum. The pons is a structure located in the brainstem that helps to relay signals between different parts of the brain, while the cerebellum is involved in motor control, coordination, and balance.