Embryology

The Roanoke Colony, established in 1585, faced significant challenges with its food supply. Initially, the settlers relied on supplies brought from England, including provisions like corn, beans, and preserved foods. However, due to difficulties in securing regular resupply and poor relations with local Indigenous tribes, the colony experienced food shortages. Ultimately, these challenges contributed to the mysterious disappearance of the Roanoke settlers by 1590.

The blastopore is located at the site of the invagination during the early stages of embryonic development in organisms that undergo gastrulation. In protostomes, it typically develops into the mouth, while in deuterostomes, it usually becomes the anus. The position of the blastopore is crucial for determining the body plan of the developing organism.

In the embryo, the bones of the arms and legs are initially formed from a cartilage model, primarily made of hyaline cartilage. This cartilaginous structure provides a template for future bone development through a process called endochondral ossification, where the cartilage gradually transforms into bone. This process allows for growth and development of the limbs during fetal development.

The discovery of the embryo can be traced back to the early studies of embryology in the 17th century. Notably, the first detailed observations of embryos were made by scientists like Marcello Malpighi and Antonie van Leeuwenhoek in the 17th century, who used early microscopes to examine developing embryos in various species. However, the understanding of the embryo's development progressed significantly throughout the 18th and 19th centuries, culminating in more comprehensive theories of embryogenesis.

The developing embryo is connected to the placenta through the umbilical cord. This cord contains blood vessels that transport nutrients, oxygen, and waste products between the embryo and the placenta, facilitating crucial exchanges for fetal development. The placenta itself acts as an interface, allowing maternal blood to nourish the embryo while protecting it from certain substances. This connection is vital for the embryo’s growth and overall health during pregnancy.

The yolk provides essential nutrients and energy for the developing embryo, serving as a food source during the early stages of development. It contains proteins, fats, vitamins, and minerals that support growth and cell division. Additionally, the yolk contributes to the formation of various tissues and organs in the embryo, facilitating overall development until it can obtain nourishment independently.

When prospective neuroectoderm from an early amphibian gastrula is transplanted into the prospective epidermal region of a recipient early gastrula embryo, the donor tissue will still differentiate into neural tissue rather than epidermis. This is due to the intrinsic properties of the neuroectoderm, which are determined by its origin and developmental signals, overriding the surrounding epidermal signals. Thus, the transplanted neuroectoderm will contribute to the formation of neural structures in the recipient embryo.

In a human embryo, structures such as pharyngeal arches, a tail, and a yolk sac are present, which are also found in the embryos of other vertebrate species. These features reflect shared evolutionary ancestry and developmental processes. For example, pharyngeal arches can develop into structures like gills in fish and parts of the jaw and ear in mammals. The presence of these common embryonic structures highlights the similarities across different species during early development.

The part of the seed that protects the embryo and cotyledons is called the seed coat. This outer layer acts as a barrier, shielding the embryo and stored nutrients from physical damage, pathogens, and adverse environmental conditions. It plays a crucial role in the seed's overall survival and viability until conditions are favorable for germination.

The question of whether an embryo or fetus should have rights is a complex ethical and legal issue that varies by cultural, religious, and philosophical beliefs. Some argue that embryos and fetuses have a right to life and should be protected, while others believe that a woman's autonomy and right to make decisions about her own body take precedence. Ultimately, the rights of an embryo or fetus may depend on the legal framework of a given jurisdiction and the societal values at play. Balancing these competing interests remains a contentious debate.

Dolphin embryos and human embryos share several similarities due to their common mammalian ancestry. Both undergo similar stages of development, including the formation of major organs and body structures during gestation. Additionally, they exhibit similar genetic and cellular processes, such as the development of a neural tube and the presence of limb buds. These similarities highlight the shared evolutionary traits among mammals, despite the significant differences in their adult forms and habitats.

A key adaptation common to all embryos is the presence of a protective structure, such as the amniotic sac in mammals or the egg membrane in reptiles and birds, which provides a controlled environment for development. This adaptation helps to safeguard the developing embryo from physical damage and desiccation, while also allowing for the exchange of gases and nutrients. Additionally, the ability to undergo cellular differentiation enables embryos to develop specialized tissues and organs necessary for survival after birth or hatching.

After fertilization, the zygote forms in the fallopian tube and begins to divide, becoming a blastocyst as it travels toward the uterus. This journey takes about 3 to 5 days, during which the cilia lining the fallopian tubes help move the developing embryo along. As it reaches the uterus, the blastocyst is ready to implant into the uterine lining, where it can begin to grow and develop further. Hormonal changes in the mother's body support this process, preparing the uterus for implantation.

Ethel Brown Harvey's experiment on sea urchins demonstrated that the cells of a developing sea urchin embryo exhibit a phenomenon known as "cell determination." She found that even when the cells were separated, they were capable of developing into specific structures, indicating that the fate of the cells is determined early in embryonic development. This work provided crucial insights into the processes of cell differentiation and the inherent potential of embryonic cells to develop into various tissues.

The theory of evolution is supported by the fossil record, which reveals a chronological progression of species and transitional forms that illustrate gradual changes over time. Comparative anatomy shows similarities in the structures of different species, indicating common ancestry; for example, the forelimbs of mammals, birds, and reptiles have similar bone structures despite differing functions. Additionally, comparative embryology demonstrates that embryos of diverse species exhibit striking similarities in early development, further suggesting a shared evolutionary origin. Together, these lines of evidence reinforce the concept that species evolve and adapt over time through common descent.

The heart begins to form in the embryo around the third week of gestation, specifically during the process known as cardiogenesis. By the end of the third week, the heart tube has typically formed and starts to beat, marking the onset of circulation. This early development is crucial for supplying oxygen and nutrients to the growing embryo.

Because the term technology is reserved for non-natural artifacts, whereas naturally evolved features are, well, natural.

The structure that connects an embryo with the organ that nourishes it is called the umbilical cord.

The umbilical cord attaches the developing fetus to the placenta, which is the organ responsible for providing nutrients and oxygen to the embryo or fetus while removing waste products. The umbilical cord contains blood vessels (two arteries and one vein) that carry deoxygenated blood and waste products away from the fetus and deliver oxygen and nutrients to the fetus from the placenta.

Posterior placenta is when the placenta is located at the back of the motherÃ?s uterus. Placenta praevia means the placenta has not moved up towards the top of the uterus to get ready for birth. Grade 2 means the placenta is near the cervix but not blocking it.

Twins can have identical chromosomes if they are monozygotic (identical twins) because they develop from a single fertilized egg that splits into two embryos. This results in both twins having the same genetic makeup and identical chromosomes.

Mammal embryos don't require a large yolk becaues they are nourished directly by the mothers body. In contrast, birds, reptiles, and other (mostly) egg layers, need a large yolk because the yolk must nourish the embryo all the way through development.

To abstract blood for DNA testing at home, you would first need to purchase a DNA extraction kit that is designed for at-home use. Follow the instructions provided with the kit to collect a small blood sample. It typically involves pricking your finger and collecting a few drops of blood onto a special collection card or tube. Ship the sample to the testing laboratory according to the kit's instructions for analysis.

because their embryos are convinient to study

- each female have millions of eggs that can be fertilized in vitro

- embryos at 48h of development forms a small larvae with all major organs formed : nerve cells, guts, mesodermal squeletton, imune cells etc ...

This is a great advantage, lots of experiments can be done in a short time

- synchronous development : each egg fertlised at a given time and at a given temperature will develop at the very same rate, so lots and lots of camprable embryos can be observed in each experiment (not the same with mouse)

- they are transparent thus easyly observable under a microscope, well suited for all forms of stainings

- Scientists have tools to perform loss and gain of function (shut down or overexpress a specific gene during development)

- Genome of an American specie (S Purpuratus)is fully sequenced, other species will soon have their genome sequenced as well

- They are non chordate deuterostomes. This makes urchins in an evolutionary point of view much closer cousins to human than drosophila (fly) which is as well extensively studied in embryology - roughly : results found in sea urchin may be more likely to reflect a situation found in vertebrates than those found in drosophila

etc etc ...

one major drawback of sea urchins is that its long life cycle (env 2 years) cannot permit the generation of mutant strains (no genetic tools like in mouse zebrafish or drosophila)

The stage of human development between zygote and fetus is the embryo stage. This stage typically lasts from the 3rd week to the 8th week after fertilization. During this time, the cells continue to divide and differentiate into the various organs and tissues of the body.