Robles, Lady Angela M. 2014-36452
Performed on: August 23, 2017 Submitted Submitt ed on: August 25, 2017
Laboratory Exercise 2 Study of the Frog Embryo Questions 1. From where are the micromeres derived? Why are they much smaller than the macromeres? Micromeres are derived from the 3 rd cleavage which produces 4 internal and external E. blastomeres. The 3 rd cleavage plane is horizontal as compared to the 1 st and 2nd cleavage. It is shifted towards the animal pole so that the upper set of 4 blastomeres or micromeres are smaller t han those below. 2. How many stages of cleavage can you identify? Six cells stages. The 2 cell stage is where the cleavage furrow appears vertically ending the 1 st zygotic cell cycle. The 3 cell stage is when the 2 blastomeres are cleaving incompletely in a single plane that passes through the animal pole at right angle to plane of first cleavage. In the 8 cell stage, the cleaving is still incomplete however however it now occurs in t wo separate planes parallel to the first one. The morula stage is where the blastocoel is already formed, this will be followed by the early blastocyst where the fluid is already in the cavity between the cells, and the expanded blastocyst stage where the blastocyst is already expanding. 3. What is the adult adult fate of the notochord? The fate of the notochord is different for every species. For example in mammals, the last vestige of the notochord can persist but it is only in the center of the invertebral disc. This is different in the case of agnathans and most primitive bony fishes where the notochord is not divided segmentally. In modern fishes however, the notochord becomes an isolated pad of tissue between one vertebra and the next. 4. State 5 derivatives derivatives of the neural neural crest. crest. The derivatives of the neural crest includes the melanocyte, odontoblast, traqueal cartilage, enterochromaffin cells and laryngeal cartilage. Questions 1. In terms of ontogeny, ontogeny, differentiate differentiate the following following a. Epiphysis from hypophysis hypophysis b. Retina from organ of corti The epiphysis originates directly in the roof of the third ventricle as an invagination of the neurorpithelium while the hypophysis begins when the Rathke’s pouch grows and rises upward to the roof of the third ventricle.
The retina originates as outgrowth of the developing brain, specifically the embryonic diencephalon; thus the retina is part of the central nervous system and is actually brain tissue. The organ of corti however, originates from the sensory primordium within the cochlear epithelium during embryonic development of the inner ear. 2. What is the function of the anterior choroid plexus? The anterior choroid plexus produces cerebrospinal fluid (CSF) and forms the blood-CSF barrier. It also establishes and maintains the extracellular milieu throughout the brain and spinal cord, in part by secreting numerous growth factors into the CSF. 3. What are the adult functions of the optic lobes? The optical lobe is the one that processes and detects visual information from the eyes. 4. What are the adult derivatives of the myelencephalon? The adult derivative of the myelencephalon is the medulla oblongata. 5. Aside from being a receptor organ for hearing, what is another function of the ear? Aside from hearing, the ear also has a part in the body’s balance. The Eustachian tube equalizes air pressure in the middle ear with the air pressure in the atmosphere. This helps humans retains their balance. The vestibular complex in the inner ear is also important as it contains receptors that regulate a sense of equilibrium. 6. What is the function of the semicircular canal? The semicircular canal is composed of three canals used to provide information to the brain on directional balance. Each canal is filled with endolymph, a fluid that moves and pushes the cilia, also found in the canal, back and forth to create a motion sensor. 7. What is the fate of the endolymphatic ducts? The endolymphatic duct passes along the aquaeductus vestibuli and ends in a blind pouch (endolymphatic sac) on the posterior surface of the petrous portion of the temporal bone, where it is in contact with the dura mater .
Questions 1. What is the importance of the pharyngeal pouches in development?
The pharyngeal pouches develop into a series of structures that include the middle ear cavity, thymus, palatine tonsil, the four parathyroid glands and the ultimobranchial bodies of the thyroid gland. 2. What ducts empty into the common bile duct? The ducts that empty into the common bile duct are the hepatic duct that carries its bile first to the liver before emptying it in the common bile duct and the cystic duct that also carries its bile first in t he gallbladder before unfilling it. 3. Differentiate the liver from the pancreas in terms of histology and function. In terms of histology, the liver is different to the pancreas because it is made up of a different set of cells which include the hepatocytes, bile canaliculi and hepatic sinusoids. The pancreas is composed of acini and pancreatic islets. In terms of function, the liver is the one that destroys old blood cells and f ilters toxins while the pancreas serves as the exocrine and endocrine gland. Questions 1. Where do the mesonephric ducts empty? The Wolfian duct also known as the mesonepheric duct is one of the paired embryonic tubules that drains the mesonephros or the primitive kidney in the cloaca. 2. What is significance of the glomi? The glomi is a temperature-sensitive organ of modified perivascular smooth muscle cells which is involved in the vascular regulation of skin temperature. 3. What are the adult derivatives of the PGCs? Primordial germ cells (PGCs) are derivatives of the epiblast cells. They migrate to through the yolk sac wall and the mesentery of the hindgut to reach the genital ridge. 4. How many atria are present at this stage? Two atria are present in this stage 5. Where do the subcardinal veins empty? The subcardinal veins drain the blood from the lower half of the body into the two common cardinal veins. 6. Where does the post cava empty anteriorly? Anteriorly, the post cava empties blood into the right atrium of the heart. 7. What organs are drained by the hepatic portal vein?
Digestive organs are drained by the hepatic portal vein. This includes all of the blood from the abdominal part of the gastrointestinal tract like the lower third of the esophagus, stomach, all 3 parts of small intestine, all parts of large intestine and upper half of the anal canal. 8. What are the derivatives of palatoquadrate? The derivatives of the platoquadrate are the incus (quadrate) and alisphenoid (greater wing of sphenoid) 9. What are the functions of the Meckelian hyoid and branchial cartilages? Meckelian hyoid is comprised of 3 distinct regions. The anterior and posterior indergo endochondral ossification and contribute to mandibular development and on the formation of the malleus and incus respectively. The middle region degenerates and gives rise to the sphenomandibular ligament. The branchial cartilage is one of the bony or cartilaginous curved bars on either side of the pharynx throat that support the gills of fishes and amphibians.
References
Chen, P. et al. (2002). The role of Math 1 inner ear development: Uncoupling the establishment of the sensory primordium from hair cell fate determination. Development 129, 2495-2505. Gilbert, S. F. (1970, January 01). The Early Development of Sea Urchins. Retrieved August 24, 2017 from https://ww.ncbi.nlm.nih.gov/books/NBK9987/ Jones, J. (n.d.). Wolfian duct | Radiology Reference Article. Retrieved on August 24, 2017 from https://radiopedia.org/article/wolfian-duct Dr. Bhatia Medical Coaching Institute. (n.d.). Flashcards of general embryology. Retrieved on August 24, 2017 from https://gradestack.com/Dr. BhatiaMedical/Primordial-germ-cells-are/41-3-42-15553-sf Moss-Salentjn, L. and Robinson, E. (n.d.). Pharyngeal pouches. Larsen 3 rd edition p. 352. Okudaira, M. (n.d.). Anatomy of the portal vein system and hepatic vasculature. Portal Hypertension, 1991, pp. 3-12.,doi: 10.1007/978-4-431-68361-2-1. Rademaker,M.(2008). Glomus tumors. Retrieved on August 24, 2017 from https://www.dermnetzorg/topics/glomus-tumors/ William, W. et al. (1997). The endolymphatic duct and sac.
