First Three Weeks Of Development – Practice Quiz Questions

During gastrulation, the primitive streak is formed, which is the first indication of this process. The primitive streak is a structure that forms in the early embryo and marks the beginning of gastrulation. It is a groove-like structure that forms on the surface of the embryo and serves as a site for cell migration and differentiation. The cells that move through the primitive streak give rise to the three germ layers - ectoderm, mesoderm, and endoderm - which eventually give rise to all the tissues and organs of the body. Therefore, the formation of the primitive streak is a crucial step in the process of gastrulation.

The inner cell mass of the blastocyst will give rise to the embryo. This inner cell mass contains pluripotent cells that have the ability to differentiate into the three primary germ layers: ectoderm, endoderm, and mesoderm. These germ layers will eventually give rise to all the different tissues and organs of the developing embryo. The outer cell mass, known as the trophoblast, will differentiate into the placenta and other supporting structures.

Based on the given information, the woman is experiencing severe abdominal pain on the right side with signs of abdominal bleeding. She has also mentioned that she has been sexually active without contraception and missed her last menstrual period. These symptoms and risk factors are highly suggestive of an ectopic tubal pregnancy, where the fertilized egg implants outside of the uterus, usually in the fallopian tube. This condition can cause severe abdominal pain and bleeding, and it is important to consider it as a possible diagnosis in this case.

The zona pellucida is not necessary for blastocyst implantation. It is a glycoprotein layer surrounding the oocyte and early embryo, which helps protect and maintain the structure of the developing embryo. However, during implantation, the zona pellucida must be shed in order for the blastocyst to make direct contact with the endometrium and establish a connection for implantation to occur. Therefore, the presence of the zona pellucida would actually hinder rather than facilitate blastocyst implantation.

The correct answer is Epiblast cells. During early embryonic development, the epiblast cells give rise to all three germ layers, including the mesoderm. The epiblast cells are located on the inner cell mass of the blastocyst and differentiate into different cell types to form the various tissues and organs of the body. The mesoderm is one of the germ layers and gives rise to structures such as muscles, bones, blood vessels, and connective tissues. Therefore, the mesoderm is formed from epiblast cells.

The epiblast is a layer of cells in the early embryo that gives rise to the three primary germ layers (ectoderm, mesoderm, and endoderm). During gastrulation, the epiblast cells migrate and form a structure called the primitive streak, which is essential for establishing the body plan of the developing embryo. Therefore, the statement "It forms the primitive streak" is correct.

The correct diagnosis in this case is placenta previa. Placenta previa occurs when the placenta is located in the lower portion of the uterus, covering or partially covering the cervix. This can cause episodes of bright red vaginal bleeding, especially in the third trimester of pregnancy. The fact that the bleeding subsided each time indicates that it was not due to a hydatidiform mole or premature rupture of the amniotic membrane. Toxemia of pregnancy, also known as preeclampsia, is characterized by high blood pressure and organ damage, and is not related to vaginal bleeding. Vasa previa is a condition where fetal blood vessels cross or run near the cervix, but it does not involve the location of the placenta.

The mother is most likely to have contracted the acute viral infection during weeks 1-5 after fertilization because this is the period when the baby's major organs, including the heart, are forming. Rubella virus can cause congenital defects, including ventriculoseptal cardiac defect, if the mother is infected during this critical period of organ development.

Ectopic pregnancies most often occur in the ampullae region of the uterine tube. This is because the ampullae region is the widest and longest part of the uterine tube, providing enough space for the fertilized egg to implant and grow. Ectopic pregnancies occur when the fertilized egg implants outside of the uterus, and the ampullae region is a common site for this to happen.

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

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

The amniotic cavity appears on the eighth day as a slit-like space between the trophoblast and the embryoblast. The embryoblast is the inner cell mass of the blastocyst that will develop into the embryo. It is surrounded by the trophoblast, which will give rise to the placenta. The amniotic cavity is a fluid-filled space that forms within the embryoblast and eventually becomes the protective amniotic sac surrounding the developing embryo.

The correct answer is that the uteroplacental circulation is established during the second week of development. This means that the circulation between the mother and the developing embryo is not present immediately after fertilization, but rather takes some time to develop. This is important because it allows for the proper exchange of nutrients and waste products between the mother and the embryo, supporting its growth and development.

If an embryo failed to form the mesoderm germ layer, the aorta would not develop. The mesoderm germ layer gives rise to various structures including the cardiovascular system, which includes the aorta. Therefore, without the mesoderm germ layer, the development of the aorta would be affected.

The lens of the eye is formed from the ectoderm. During embryonic development, a portion of the ectoderm called the lens placode invaginates to form the lens vesicle. This vesicle then differentiates into the lens of the eye. The other options listed do not contribute to the formation of the lens.

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 plays a crucial role in organizing the cells that will give rise to the different tissues and organs of the body. In some cases, cells from the primitive streak can become displaced and form a tumor, which is known as a sacrococcygeal teratoma.

The dermis of the skin is derived from the mesoderm, not the ectoderm. The ectoderm gives rise to the epidermis, enamel of teeth, forebrain, and mammary gland. The dermis is the layer of skin beneath the epidermis, and it is derived from the mesoderm during embryonic development.

Neural crest cells are a type of embryonic cells that migrate and contribute to the development of various structures in the body, including both the craniofacial region and the outflow tract of the heart. Therefore, it is not surprising to see craniofacial abnormalities and a cardiac defect involving the outflow tract of the heart in a newborn when neural crest cells are involved in their development.

The excretory units of the urinary system, which include the kidneys and the ureters, are derived from the intermediate mesoderm. During embryonic development, the intermediate mesoderm gives rise to the urogenital system, which includes the urinary system. This process involves the formation of the nephrogenic cord, which later differentiates into the nephrons, the functional units of the kidneys. Therefore, the correct answer is intermediate mesoderm.

During embryonic development, the lateral plate mesoderm splits into two layers, forming the intraembryonic cavity. This cavity is located between the ectoderm and endoderm and eventually gives rise to various structures such as the cardiovascular system, connective tissues, and the lining of the body cavities. The splitting of the lateral plate mesoderm is a crucial step in the formation of the embryo and allows for the proper development and differentiation of different tissues and organs.

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 are responsible for producing and distributing the pigment melanin, which gives color to the skin, hair, and eyes. The other options, mesoderm, mesenchyme, ectoderm, and dermis, are not the direct sources of melanocytes.