First Three Weeks Of Development – Practice Questions

The given information suggests that the woman is experiencing severe abdominal pain on the right side, signs of abdominal bleeding, and missed her last menstrual period. These symptoms are indicative of a possible ectopic tubal pregnancy. In an ectopic pregnancy, the fertilized egg implants outside of the uterus, most commonly in the fallopian tube. This can cause severe abdominal pain and bleeding. Therefore, ectopic tubal pregnancy must be included as an option in the diagnosis.

The inner cell mass of the blastocyst will give rise to the embryo. This is because the inner cell mass contains pluripotent cells, which have the ability to differentiate into all three germ layers (ectoderm, endoderm, and mesoderm) that form the various tissues and organs of the developing embryo. The outer cell mass, or trophoblast, will give rise to the placenta and other supporting structures. Therefore, the correct answer is d) inner cell mass.

The zona pellucida is not necessary for blastocyst implantation. The zona pellucida is a glycoprotein layer that surrounds the oocyte and early embryo. It plays a role in fertilization by preventing polyspermy, but once the blastocyst reaches the uterus, it needs to hatch out of the zona pellucida in order to implant into the endometrium. Therefore, the zona pellucida is not necessary for blastocyst implantation.

The correct answer is d) Epiblast cells. During embryonic development, the mesoderm layer is formed from the epiblast cells. These cells undergo a process called gastrulation, where they migrate and differentiate into the mesoderm layer. The mesoderm gives rise to various structures in the body such as muscles, bones, connective tissues, and the circulatory system.

The formation of the primitive streak is the first indication of gastrulation. Gastrulation is a crucial process in embryonic development where the single-layered blastula is transformed into a three-layered structure called the gastrula. The primitive streak is a groove that forms on the surface of the blastula and serves as the site of cell migration and differentiation. It is responsible for the establishment of the three germ layers - ectoderm, mesoderm, and endoderm - which give rise to different tissues and organs in the developing embryo. Therefore, the formation of the primitive streak marks the beginning of gastrulation.

Vaginal bleeding after 20 weeks of pregnancy is the primary symptom of placenta previa.

The placenta normally attaches to the upper portion of the uterus which is more muscular and stronger to support the placenta. However, in placenta previa the placenta attaches to the lower portion of the uterus which is weaker, thinner, and more vascular. As you enter your second and third trimester, the cervix begins to thin and stretch in preparation for labor. As this area stretches it can cause the villi (blood vessels) to break therefore causing bleeding.

Placenta previa can lead to complications for both mother and baby. Complications that may arise include placenta abruption, hemorrhaging, preterm labor, anemia for either mother or baby.

Rubella virus infection during pregnancy can cause congenital rubella syndrome (CRS) in the baby. The timing of the infection is crucial because it determines the severity of the syndrome. The highest risk of CRS occurs when the mother is infected during the first trimester of pregnancy, specifically between weeks 1-5 after fertilization. This is when the baby's organs and systems are developing, including the heart. Therefore, the mother is most likely to have contracted the acute viral infection during weeks 1-5 after fertilization.

Ectopic pregnancies most often occur in the ampullae region of the uterine tube. This is because the fertilized egg typically implants and grows in the fallopian tube instead of the uterus. This can be a dangerous condition as the fallopian tube is not designed to support the growth of a pregnancy, which can lead to complications such as rupture and internal bleeding.

The epiblast is a layer of cells in the blastocyst that gives rise to the three primary germ layers of the embryo. The primitive streak is a structure that forms during gastrulation, which is the process by which the three germ layers are established. Therefore, the correct statement is that the epiblast forms the primitive streak.

The lens of the eye is formed from the ectoderm. During embryonic development, a structure called the optic vesicle invaginates to form the optic cup, which eventually gives rise to various structures of the eye, including the lens. The lens placode, which is a thickening of the ectoderm, invaginates to form the lens vesicle, which then differentiates into the lens. Therefore, the correct answer is b) ectoderm.

The correct answer is c) It is established during the second week of development. During the second week of development, the uteroplacental circulation is established as the cytotrophoblast differentiates into syncytiotrophoblast and forms lacunae. These lacunae then merge to form the intervillous spaces, which allow for the exchange of nutrients and waste products between the maternal blood and the developing embryo. This circulation is crucial for the proper development and nourishment of the embryo.

The correct answer is False. The intraembryonic mesoderm is located between the endoderm and ectoderm at both the buccopharyngeal membrane and the cloacal membrane.

The amniotic cavity appears on the eighth day as a slit-like space between the trophoblast and the embryoblast. This means that the correct answer is b) embryoblast. The embryoblast is the inner cell mass of the blastocyst, which gives rise to the embryo. The amniotic cavity is formed within the embryoblast and eventually becomes the amniotic sac, which surrounds and protects the developing embryo.

If an embryo fails to form the mesoderm germ layer, the aorta would not develop. The mesoderm germ layer is responsible for the development of various structures including the cardiovascular system. The aorta is a major blood vessel that arises from the embryonic mesoderm and is essential for transporting oxygenated blood from the heart to the rest of the body. Without the mesoderm germ layer, the development of the aorta would be impaired, leading to potential cardiovascular abnormalities.

Neural crest cells are a migratory population of cells that play a crucial role in the development of both the craniofacial region and the cardiac outflow tract. They contribute to the formation of various structures in these areas, including the bones and cartilage of the face, as well as the smooth muscle cells and connective tissue of the heart. Therefore, it is not surprising to see craniofacial abnormalities and cardiac defects in a newborn when neural crest cell development is affected.

The extraembryonic mesoderm is located between the exocoelomic membrane and the cytotrophoblast.

The dermis of the skin is derived from the mesoderm, not the ectoderm. The ectoderm gives rise to the epidermis, which is the outermost layer of the skin, as well as structures such as the enamel of teeth, the forebrain, and the mammary gland. The dermis, on the other hand, is a connective tissue layer that lies beneath the epidermis and is derived from the mesoderm.

The primitive streak is the correct answer because a sacrococcygeal teratoma is a tumor that arises from remnants of the primitive streak. The primitive streak is a structure that forms during early embryonic development and gives rise to the three germ layers (ectoderm, mesoderm, and endoderm). It is located on the dorsal surface of the embryo and is involved in establishing the body plan. In some cases, cells from the primitive streak can become displaced and form a tumor, such as a sacrococcygeal teratoma.

Melanocytes are derived from neural crest cells. During embryonic development, neural crest cells migrate from the neural tube and give rise to various cell types, including melanocytes. These cells eventually settle in the skin, hair follicles, and other parts of the body where they produce the pigment melanin. This pigment is responsible for the coloration of the skin, hair, and eyes.

The excretory units of the urinary system, which include the kidneys and the ureters, are derived from the intermediate mesoderm. This germ layer gives rise to the urogenital system, which includes both the urinary and reproductive systems. The intermediate mesoderm undergoes further differentiation and development to form the structures of the urinary system.

The splitting of the lateral plate mesoderm forms the intraembryonic cavity. This cavity is formed during the process of gastrulation, where the mesoderm layer splits into two layers - the parietal layer and the visceral layer. The space between these two layers forms the intraembryonic cavity, which will later give rise to various structures such as the cardiovascular system, respiratory system, and digestive system.