Category Archives: Embryology

Embryology

Duke Embryology – Craniofacial Development

Click here to launch the Simbryo Head & Neck Development animation (and some really trippy music -you'll understand once the window opens...)

I. Pharyngeal apparatus

A. Fates of pharyngeal clefts

The pharyngeal clefts are ectodermal-lined recesses that appear on the OUTSIDE of the pharnyx between the arches; cleft 1 is between arch 1 and 2, cleft 2 is between arches 2 and 3, etc.

1. pharyngeal cleft 1: develops into the external auditory meatus (the corresponding 1st pharyngeal pouch develops into the auditory (or Eustacian) tube, and the intervening membrane develops into the tympanic membrane).

Defects in the development of pharyngeal cleft 1 can result in preauricular (i.e. in front of the pinna of the ear) cysts and/or fistulas.

2. pharyngeal clefts 2, 3, and 4 are overgrown by expansion of the 2nd pharyngeal arch and usually obliterated

Remnants of pharyngeal clefts 2-4 can appear in the form of cervical cysts or fistulas found along the anterior border of the sternocleidomastoid muscle.

B. Fates of pharyngeal arches

1. Pharyngeal Arch 1 (mandibular arch)

2. Pharyngeal Arch 2 (hyoid arch)

3. Pharyngeal Arch 3

4. Pharyngeal Arch 4

5. Pharyngeal Arch 6

The fates of the pharyngeal arches and their derivative structures can be summarized by the two figures below:

C. Fates of pharyngeal pouches

The pharyngeal pouches are endodermal-lined pockets that form on the INSIDE of the pharynx between the arches; pouch 1 forms between arch 1 and arch 2, pouch 2 forms between arch 2 and arch 3, etc.

1. Pharyngeal Pouch 1 develops into the auditory tube and middle ear cavity

2. Pharyngeal Pouch 2 forms numerous infoldings that become the crypts of the palatine tonsil; later, lymphocytes (from the thymus and bone marrow) infiltrate the underlying lamina propria to establish the definitive palatine tonsil.

3. Pharyngeal Pouch 3 divides into a superior (or dorsal) and inferior (or ventral) portion:

dorsal portion of pouch 3: forms the inferior parathyroid glands the chief (or principal) and oxyphil cells are derived from the endodermal lining of the pouch ventral portion of pouch 3: forms the thymus the epithelial reticular cells (including those that comprise the thymic or Hassall's corpuscles) are derived from the endodermal lining of the pouch. T-cell progenitors from the bone marrow infiltrate the cortex to establish the definitive thymus.

4. Pharyngeal Pouch 4 also divides into a superior (or dorsal) and inferior (or ventral) portion:

dorsal portion of pouch 4: forms the superior parathyroid glands the chief (or principal) and oxyphil cells are derived from the endodermal lining of the pouch

ventral portion of pouch 4: forms a diverticulum called the ultimobranchial body, the cells of which migrate into the thyroid gland and differentiate into parafollicular (C) cells of the thyroid gland.

Anomalous development of the derivatives of pouches 3 and/or 4 can result in ectopic or absent parathyroid, thymic, or parafollicular thyroid tissue. The most common disorder in which this occurs is DiGeorge syndrome, caused by a deletion in the long (or "q") arm of chromosome 22, leading to a hypoplasia of 2nd and 3rd pharyngeal pouch derivatives. Symptoms and signs of DiGeorge often include:

Interestingly, the hypoplasia of the 2nd and 3rd arches can also disrupt the 1st and arch, leading to the following additional findings:

II. Development of the tongue

A. Anterior 2/3 of the tongue:

1. Formation: the anterior 2/3 of the tongue is derived from median and lateral tongue buds that arise from the floor of the 1st pharyngeal arch and then grow rostrally. The tongue buds are then invaded by occipital myoblasts that form the intrinsic muscles of the tongue.

2. Innervation of the anterior 2/3 of the tongue:

B. Posterior 1/3 of the tongue:

1. Formation: swellings from the floor of the 3rd and 4th pharyngeal arches overgrow the 2nd arch and fuse with the anterior 2/3 of the tongue. Thus, the posterior 1/3 of the tongue is derived from the 3rd and 4th arches and there is NO contribution of the 2nd pharyngeal arch in the adult tongue. Intrinsic musculature is also derived from occipital myoblasts. The line of fusion of the anterior 2/3 and posterior 1/3 of the tongue is indicated by the terminal sulcus.

2. Innervation of the posterior 1/3 of the tongue:

III. Development of the thyroid gland

Anomalies in thyroid development can result in ectopic thyroid tissue and/or cysts present along the course of the thyroglossal duct, which is a midline structure (as opposed to cervical cysts, which are remnants of pharyngeal clefts 2-4 and are found lateral to the sternocleidomastoid muscles).

IV. Development of the skull

Because the brain continues to grow in size up until 6-7 years of age, premature fusion of the sutures or fontanelles will result in abnormal shaping of the head as the brain will cause displacement of the bones that remain unfused.

V. Development of the face

Below is a summary of the contributions of the prominences to the adult face:

Disruption of the development of any of the facial prominences can result in a variety of facial anomalies, such as (from left to right in figures below):

VI. Development of the palate

A. Primary palate

B. Secondary palate

Complete fusion of the primary and secondary palate is a complex process involving growth of the component tissues, epithelial to mesenchymal transformation, cell migration, and programmed cell death at fusion sites disruption of any part of this process can result in cleft palate. Given the involvement of the maxillary and nasal prominences, cleft palate is often (but NOT always) accompanied by cleft lip.

Practice Questions

1. In craniofacial development, paraxial mesoderm contributes to which of the following?

A. occipital bone B. muscles of the tongue C. extraocular muscles D. NONE of the above E. ALL of the above

ANSWER

2. The craniofacial defect illustrated in the figure below was most likely caused by which of the following?

ANSWER

3. The condition shown in the figure below was most likely caused by:

A. failure of the medial and lateral nasal processes to fuse with the maxillary process. B. incomplete merging of the maxillary and mandibular processes. C. incomplete fusion of the medial nasal processes. D. overgrowth of the frontonasal process. E. incomplete growth of the mandibular process.

ANSWER

4. The thyroid gland is derived primarily from the:

A. 1st pharyngeal pouch. B. 2nd pharngeal pouch. C. ventral portion of the 3rd pharyngeal pouch. D. dorsal portion of the 4th pharyngeal pouch. E. foramen cecum at the base of the tongue.

Read more:
Duke Embryology - Craniofacial Development

Embryology

Embryology – San Antonio Fertility

Behind the scenes at San Antonio IVF, our embryologists maintain the highest level of IVF lab quality, and perform the procedures that lead to the optimal fertilization of eggs, the healthy growth of embryos and the development of successful pregnancies. We are fortunate to have on staff sought-after clinical embryologists and an IVF lab director who are each committed to safeguard the eggs, embryos, and sperm that you entrust to their care.

Our San Antonio IVF embryologists have years of experience performing complex IVF procedures. In addition to conventional insemination in a petri dish, we specialize in advanced services such as laser assisted hatching, intracytoplasmic sperm injection (ICSI), egg and embryo vitrification (ultra-rapid freezing), and embryo biopsy for genetic testing. Our embryologists focus on procedures that affect both male and female infertility, using the latest technologies, including time-lapse photography to assess embryonic development.

Our advanced reproductive technology (ART) laboratory was designed to exact standards, and outfitted with incubators, micromanipulators, and micro-surgical lasers to create the optimal environment for embryonic growth and development. When genetic materials pass through the doors of San Antonio IVF, our embryologists become their caretakers.

The IVF lab, located in the Stone Oak area of San Antonio, consists of over 4000 square feet of customized air filtration systems, microscopes, high definition video systems, and state-of-the-art incubators, each unique to our purpose of sustaining new life.

Our embryologists job starts with an assessment of the male partners sperm. We evaluate every specimen for concentration (the number of sperm present in each cc of semen), motility (the percentage of sperm that are alive and swimming), and normal morphology (the percentage of sperm that have a normal shape). We then choose the best sperm preparation technique to use so that we can get the greatest number of normally shaped, motile sperm to add to the eggs.

Once the eggs have been retrieved, they must be identified, removed from their surrounding cells, and placed into culture so that they can continue to mature in the laboratory. Approximately 5-6 hours after retrieval, several thousand moving sperm are either added to a droplet of culture media containing each egg (insemination), or in cases where the sperm specimen is not of very good quality a single sperm is actually injected directly into each egg by our embryologists using a tiny needle directed by robotically controlled instruments (ICSI). These eggs are then returned to their incubator for 18 hours of development, during which time fertilization hopefully occurs.

Over the course of the following week, while our embryologists monitor and maintain the culture media, gas atmosphere, humidity and temperature levels in the incubators that house the embryos, the embryos begin to divide and develop. They regularly assess embryonic growth checking often enough to make sure the embryos are meeting their developmental milestones, while not checking too often so that the environment within each incubator remains optimal.

A Week in the Life of an Embryo

Day 1: After documenting fertilization, each embryo is placed in culture media that mimics the environment normally found in the fallopian tube.

Day 2: Embryos are allowed to continue growing without being disturbed.

Day 3: Embryonic development is assessed and a decision is made about next steps. In most cases, we will return the embryos to the incubator where they will continue to grow. In rare cases, we consider embryo transfer, or even embryo biopsy on day 3. If we are going to do your embryo biopsy on day 3, an embryologist will remove a single cell from each viable embryo for preimplantation genetic screening (PGS) or diagnosis (PGD) at this time.

Day 4: Embryos are allowed to continue growing without being disturbed.

Day 5: Aside from Day 1 when we confirm fertilization, Day 5 is perhaps the most important day in an IVF cycle. Day 5 is the first day that embryos reach the critical blastocyst stage. If we are planning on doing a fresh embryo transfer, this is the day that it most often occurs. If, on the other hand, we are planning on freezing all embryos, this is the first day that we start this process. In addition, for those patients who desire genetic testing of their embryos, this is the first day that we start to perform embryo biopsies as well.

Days 6 and 7: Embryos are reassessed for vitrification (freezing) and biopsy (if indicated).

An Embryologists Role in Female infertility

An Embryologists Role in Male infertility

Embryologists at San Antonio IVF play a significant role in increasing the chance for successful conception despite male or female infertility factors. Your embryology team at our San Antonio IVF facility treats each specimen as they would a patientwith care, concern and the highest level of professionalism.

Contact San Antonio IVF for more information regarding our laboratory procedures, personnel, and latest successes. We are committed to providing the highest quality, evidence-based IVF lab services by our world class embryologists and andrologists.

See the original post here:
Embryology - San Antonio Fertility

Embryology

Embryology – Biology Dictionary

Embryology Definition

Embryology is the branch of biology concerned with the development of new organisms. Embryologists track reproductive cells (gametes) as they progress through fertilization, become a single-celled zygote, then an embryo, all the way to a fully functioning organism. There are many subdivisions of embryology, some scientist focusing on human embryos, while others study animals and plants. Evolutionary biologists often use embryology as a means of comparing species, as the development of an organism can give many clues to its evolutionary history. Still other scientists use embryology as a tool to better understand the system or organism they are dealing with, be it conservation of an endangered species or the reproductive disruption of a pest species. Scientists studying human embryology assist with womens reproductive health, and understand the broad scope of issues which can lead to developmental defects and malformations.

Early scientists and philosophers were not ignorant, and were aware of sperm as soon as the microscope was invented. However, there have been competing theories in early embryology. The first notions of embryology are as old as the classical philosophers. Aristotle first proposed the correct mechanism for the development of an embryo, without having a microscope to observe his theory. Aristotle suggested that animals form through the process of epigenesis, in which a single cell divides and differentiates into the many tissues and organs of an animal. However, without evidence, a theory is really only a guess.

A second theory, preformation, gained much traction before the invention of microscopes and more advanced imaging techniques. This idea suggested that the embryo was contained, small but fully formed, inside the sperm. An image of this theory can be seen above. This theory also suggested women were simply vessels to carry the growing child, and that girls came from the left testicle, while boys came from the right. Knowing modern biology, it is obvious that this theory is incorrect. At the time, though, lack of proof and religious overtones into science pushed this rather sexist and equally unproven idea. When the microscope finally was invented, one of the first things people looked at was sperm. The sperm were magnified to the limits of early microscopes, and no fully formed small babies were ever found. But, this failed to fully convince the preformation supporters that epigenesis was the right answer.

It wasnt until 1827 that clear evidence was obtained that female mammals also produce a sex cell, the ovum. The discovery of a female sex cell directly contradicted many aspects of the preformation theory, and led to wider acceptance of the epigenesis theory. Karl Ernst von Baer, discoverer of the ovum, and Heinz Christian Pander then proposed the theory which is still at the heart of embryology today. That theory is the germ layer theory, which postulates that a single cell becomes separate layers of cells as the early organism divides. These germ layers then give rise to the rest of the organism by growing and folding into organs, vessels, and other complex tissues and the cells within differentiate accordingly.

A few more advancements would fully establish the germ layer theory into embryology. The discovery and understanding of DNA led to a more comprehensive understanding of how sperm and egg become a zygote. The development of ultrasound greatly increased the understanding of fetus development in humans, seen in the above image. Many studies were done on simple organisms to understand basic embryology. The flat worm was cultured intensively, as it reproduces sexually and the cells are large enough to watch develop under a good microscope. The fruit fly was also observed extensively, for similar reasons. Studying a polychaete worm, E.B. Wilson developed a coding process to label and understand the movements and divisions of cells during embryogenesis. While the exact process changes depending on the species, this method greatly expedited the understanding of embryology and led to medical and evolutionary science breakthroughs.

An embryologist is a scientist who studies embryology. Any organism that reproduces sexually must create some sort of embryo as it develops into an adult form. An embryologist may study the development of animals, plants, and even fungi. Evolutionary biologists often study embryology as a means of understanding complicated lines of evolution. For instance, all vertebrates including humans go through an embryological phase in which the precursors for gills are present. In humans, these structures develop into structures of the throat. However, the similarity between all vertebrate embryos suggests that all vertebrates arose from a common ancestor which used this form of embryogenesis. A professional embryologist may remain in academia, advancing the science of embryology, or can choose to join the medical profession.

Embryologists are needed anywhere pregnancy is handled, as pregnancy is simply human embryogenesis. Some scientists specialize in disruptions to embryogenesis which result in malformations and disorders. This is called teratology, and covers everything from miscarriages to birth defects. Doctors can specialize solely in embryology and teratology or may choose to cover a broader range of womens health issues.

Many professions employ knowledge of embryology in their practices. Many pharmaceutical companies develop drugs for both fertility and sterility, and the processes of embryology are key to these efforts. Scientists developing insecticides, or ways to deal with other pests, often turn to embryology to battle the reproductive cycles of the organisms. This is often the most cost-efficient way to battle a large pest problem. Others use embryology for the advantage of a species, like the scientists trying to repopulate endangered species. For instance, researchers at several institutions across the United States are teaming up to save the Black-Footed Ferret. They must understand ferret embryology to fully be successful, as well as their behavior, diet, and mating habits. This is a good example of how embryology plays a small but very important role in a larger scientific endeavor.

Continued here:
Embryology - Biology Dictionary

Embryology

Evolution

The study of one type of evidence of evolution is called embryology, the study of embryos. An embryo is an unborn (or unhatched) animal or human young in its earliest phases. Embryos of many different kinds of animals: mammals, birds, reptiles, fish, etc. look very similar and it is often difficult to tell them apart. Many traits of one type of animal appear in the embryo of another type of animal. For example, fish embryos and human embryos both have gill slits. In fish they develop into gills, but in humans they disappear before birth.

This shows that the animals are similar and that they develop similarly, implying that they are related, have common ancestors and that they started out the same, gradually evolving different traits, but that the basic plan for a creature's beginning remains the same.

Go here to read the rest:
Evolution

Embryology

Human Fertilisation and Embryology Act 2008 – Wikipedia

The Human Fertilisation and Embryology Act 2008 (c 22) is an Act of the Parliament of the United Kingdom. The Act constitutes a major review and update of the Human Fertilisation and Embryology Act 1990.

According to the Department of Health the Act's key provisions are:[2]

The Bill's discussion in Parliament did not permit time to debate whether it should extend abortion rights under the Abortion Act 1967 to also cover Northern Ireland. The 2008 Act does not alter the status quo.[3]

The Act also repealed and replaced the Human Reproductive Cloning Act 2001.

Originally posted here:
Human Fertilisation and Embryology Act 2008 - Wikipedia

Embryology

Pharyngeal pouch (embryology) – Wikipedia

In the embryonic development of vertebrates, pharyngeal pouches form on the endodermal side between the pharyngeal arches. The pharyngeal grooves (or clefts) form the lateral ectodermal surface of the neck region to separate the arches.

The pouches line up with the clefts,[1] and these thin segments become gills in fish.

The endoderm lines the future auditory tube (Pharyngotympanic Eustachian tube), middle ear, mastoid antrum, and inner layer of the tympanic membrane. Derivatives of this pouch are supplied by Mandibular nerve.

Derivatives include:

Read the original:
Pharyngeal pouch (embryology) - Wikipedia

Embryology

Human Fertilisation and Embryology Act 1990

38 Conscientious objection.E+W+S+N.I.

(1)No person who has a conscientious objection to participating in any activity governed by this Act shall be under any duty, however arising, to do so.

(2)In any legal proceedings the burden of proof of conscientious objection shall rest on the person claiming to rely on it.

(3)In any proceedings before a court in Scotland, a statement on oath by any person to the effect that he has a conscientious objection to participating in a particular activity governed by this Act shall be sufficient evidence of that fact for the purpose of discharging the burden of proof imposed by subsection (2) above.

Originally posted here:
Human Fertilisation and Embryology Act 1990

Embryology

Surrogacy | Law Commission

We have identified some areas of law that our experience and discussion with stakeholders suggest may require reform. They could be potential projects for the Programme. We would like to hear your views about these, and whether you think they should form part of our work over the next few years.

Is the law governing surrogacy keeping pace with social change?

Various stakeholders have suggested to us that the law relating to surrogacy should be reviewed and Jane Ellison MP, Under Secretary of State for Health, has indicated her and the Governments support for inclusion of such a project in our 13th Programme consultation.

The main legislation concerning surrogacy is the Surrogacy Act 1985 and (in respect of the making of parental orders) the Human Fertilisation and Embryology Act 2008. The law has struggled to adapt to changes in attitudes, a growing demand for surrogacy arrangements, and an increasing number of overseas surrogacy arrangements. There are a number of issues in the law that may be in need of reform:

We are interested in consultees views on the impact of these issues and whether they would be suitable for review by the Law Commission. We would also like to hear about any specific aspects of surrogacy law that consultees suggest require modification, simplification or reform. Please use this form to send us your comments, and email it to programme@lawcommission.gsi.gov.uk.

Return to Law Commission suggested projects

See the rest here:
Surrogacy | Law Commission