Period of The Zygote free essay sample

The period of the zygote begins at fertilization. After a female egg is fertilized, the resulting one celled organism becomes known as a zygote. Once the egg is fertilized, the zygote begins a two-week period of rapid cell division and will eventually become an embryo. The zygote divides through a process known as mitosis, in which each cell doubles by dividing into two cells. This two-week stage is known as the germinal period of development and covers the time of conception to implantation of the embryo in the uterus. In most cases, each male and female sex cell contains 23 chromosomes. When these two haploid cells join, they form a single diploid cell that contains a total of 46 chromosomes. The zygote begins a journey down the fallopian tube to the uterus where it must implant in the lining in order to obtain the nourishment it needs to grow and survive. The period of the zygote lasts for about four days. We will write a custom essay sample on Period of The Zygote or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page Around the fifth day, 60 to 70 cells exist that form a hollow, fluid filled ball called a blastocyst. The embryonic disk will become the new organism; the outer ring will provide protective covering. Implantation occurs sometime between the seventh and ninth day which the blastocyst burrows deep into the lining of the uterus. The amnion is a membrane that encloses the developing organism in amniotic fluid. The fluid functions as a cushion and temperature regulator. The yolk sac produces blood cells until the liver, spleen, and bone marrow mature enough to take over this function. The chorion, a protective membrane develops around the amnion by the end of the second week. The placenta is a special organ that permits food and oxygen to reach the zygote and waste products to be carried away. The umbilical cord connects the placenta to the developing organism. The period of the embryo lasts from implantation through the eighth week of pregnancy. The most rapid prenatal changes take place during these six weeks as the groundwork for all body structures and internal organs is begun. During the third week, the embryonic disk folds over to form three cell layers: 1.) Ectoderm- becomes the nervous system and skin. 2.) Mesoderm- from which will develop muscles, skeleton, cardiovascular system, and reproductive system. 3.) Endoderm- becomes the digestive system, lungs, urinary tract, and glands. The nervous system develops fastest in the beginning. The neural tube is a primitive spinal cord that forms when the ectoderm folds over. The embryo’s posture becomes more upright. The embryo can move, and it responds to touch, especially in the mouth area and on the soles of the feet. The period of the fetus is the â€Å"growth and finishing† phase that lasts until the end of pregnancy. The third month the organs, muscles, and nervous system organize and connect. By the twelfth week, the external genitals are well-formed, and the sex of the fetus can be determined using ultrasound. Trimesters are three equal time periods in prenatal period, each of which lasts three months. By the middle of the second trimester (which lasts from 13 to 24 weeks), the fetus has grown large enough that the mother cam feel its movements. Vernix is a white cheese like substance that covers the fetus and protects its skin from becoming chapped in the amniotic fluid. Lanugo is a white downy hair that also covers the fetus and helps vernix stick to the skin. At the end of the second trimester all the brain’s neurons have been produced. The fetus can now be both stimulated and irritated by sounds and light. The third trimester is the age of viability, between 22 and 26 weeks, is the age at which the fetus can first survive if born early. The brain continues to make great strides during the last three months. The cerebral cortex enlarges and the fetus spends more time awake. The fetus is also more responsive to external stimulation. The fetus moves less often, because of reduced space and greater ability to inhibit behavior. A layer of fat develops under the skin to assist with temperature regulation. In the last weeks, most fetuses move into an upside-down position.

Special Stains Laboratory Report The WritePass Journal

Special Stains Laboratory Report Introduction Special Stains Laboratory Report IntroductionMethodMasson’s TrichromeCongo RedDiscussionReferencesRelated Introduction Staining is a technique that is used to diagnose or study the morphology of abnormal cells such as cancerous cells by highlighting the structural components of a tissue (Bancroft and Gamble, 2008). Staining provides a contrast between different structures in a tissue specimen and allows its examination under a light microscope (Cook, 2006). Haematoxylin and eosin (HE) is a routine stain that is used to microscopically diagnose a vast majority of specimens in which the haematoxylin stains the nuclei, whereas the eosin is used to stain cytoplasm and other extracellular materials (Bancroft and Cook, 1995). According to Slauson and Cooper (2002) special stains are histochemical stains that react with known substances in the tissue. Mohan (2005) explains that special stains are required in various circumstances, where the pathologist needs to demonstrate certain constituent of the cells or the tissue to confirm the diagnosis by etiologic, histogenic and pathogenic components. This techniq ue is called special because they are not a routine stain that is performed on a tissue specimen, instead they are used in addition to HE stained sections (Bancroft and Gamble, 2008). Special stains can identify the presence and abundance of any specific class of molecules in a tissue specimen for example periodic acid-Schiff (PAS) reaction is used to identify carbohydrate substances such as glycogen (Slauson and Cooper, 2002). Other examples include Toluidine blue stain which is used to stain mast cell granules, Perl’s stain demonstrates iron in haemochromatosis, Ziehl-Neelsen stains mycobacteria and Giemsa staining is used to identify Helicobacter Pylori and Giardia organisms (Slauson and Cooper, 2002 and Bass et al., 2005) Masson’s trichrome (MT) and Congo red are the two main special staining methods used in pathology laboratories. Connective tissues consist of cells such as collagen fibres, elastic fibres, and glycosaminoglycans that are scattered within an extracellular matrix (Starr et al., 2011). These cells are distinguished by using a combination of dyes to stain different structures in various different colours (Starr et al., 2011). Masson’s trichrome is used to express collagen in tissues and involves staining with three different sized dyes to stain three diverse tissue densities (Cook, 2006). MT staining produces three distinct colours as the name suggests; nuclei and other basophilic structures are stained black with iron hematoxylin; collagen is stained green or blue depending on aniline light green or aniline blue; and cytoplasm, muscle, erythrocytes and keratin are stained bright red with Biebrich scarlet stain (Young et al., 2006). Since erythrocytes are the densest as the y are packed with haemoglobin, and less porous tissues they are stained with the smallest dye molecule, the intermediate cytoplasm and muscles cells are stained by the intermediate sized dye and the collagen is stained with the biggest dye (Bancroft and Gamble, 2008). However, it has also been suggested that the acid dye which is the Biebrich Scarlet, first stains the tissue as it binds to its acidophilic elements (Carson, 2001). Subsequently, the tissue is treated with phosphomolybdic/phosphotungstic acids so that the less permeable components retain the red colour, whereas it is diffused out of the collagen fibers causing it to bind with the aniline blue or aniline light green (Bancroft and Gamble, 2008). Young et al., (2006) describes that in addition to the use MT stain in assessing the degree of fibrosis, it is also used to evaluate portal tract structures such as the bile ducts, arteries and veins in inflamed liver According to Romhanyi (1971) (cited in Bely, 2006) Congo red is a special stain that is highly specific and a sensitive method for early diagnosis and recognition of amyloidosis.   Cook (2006) states that Congo red is used as the preferred method to identify amyloids in most laboratories on formalin fixed, paraffin embedded tissue of patients with amyloidosis. Kiernan (2007) describes that amyloid is an intercellular material that varies in its composition and is deposited in tissues such as heart, muscle, kidneys, spleen, liver and brain, deposits differ in their composition. Rubin and Strayer (2008) explains that Congo red stain has a linear shaped molecule which helps it to bind to the ÃŽ ² pleated sheet structure of the amyloid through non-polar hydrogen bonds, giving it a red colour. Sen and Basdemir (2003) states that Congo red fluorescence (CRF) is another method that examines the amyloid deposits stained with Congo red under polarized light which shows a red-green birefring ence and according to Rocken and Eriksson (2009) this is the gold standard for diagnosing amyloid. During this experiment special stain techniques were used to analyse specific tissue elements Aims To identify fibroids in uterine tissue section using Masson’s trichrome stain To identify amyloid in spleen tissue section using Congo red stain To discuss advantages of special stains To use special stains to identify important diagnostic features of the tissue To understand the mechanism used by special stains Method Masson’s Trichrome The formalin fixed and paraffin-embedded uterine tissue section was deparaffinized and rehydrated through 100% alcohol, 95% alcohol, and 70% alcohol.   The section was washed in distilled water and then stained in Weigert’s iron hemotoxylin working solution for 10 minutes. It was then rinsed in running warm tap water for 10 minutes and then washed in distilled water. The next step was to stain the uterine tissue section in Biebrich scarlet-acid fuchsin solution for 15 minutes, and then it was washed using distilled water. It was then differentiated in phosphomolybdic – phosphotungstic solution for 15 minutes or until collagen was not red. The tissue section was then transferred directly (without rinsing) to aniline blue solution and stained for 5-10 minutes. Afterwards the tissue section was rinsed briefly in distilled water and differentiated in 1% acetic acid solution for 1 minute. It was then washed in distilled water and dehydrated very quickly through 95% ethyl a lcohol, absolute ethyl alcohol (to wipe off Biebrich scarlet-acid fuschin staining) and then cleared in xylene. The section was then mounted with resinous mounting medium. Finally the slide was examined under the light microscope. Congo Red The spleen tissue section was deparaffinized and hydrated to distilled water. The section was then stained in Congo red working solution for 10 minutes and rinsed in distilled water. It was then quickly differentiated (5-10 dips) in alkaline alcohol solution and rinsed in tap water. The section was then counterstained in Gill’s haematoxylin for 10 seconds and rinsed in tap water for 2 minutes. Following that, the section was dipped in ammonia water (made by adding a few drops of ammonium hydroxide to tap water and mixing it well) for 30 seconds or until the sections had turned blue. It was then rinsed in tap water for another 5 minutes and dehydrated through 95% alcohol, and 100% alcohol. The section was cleared in xylene and mounted with mounting medium. The slide was then examined under a light microscope. Fig 1: Normal uterine tissue stained with Masson’s trichrome viewed under 10 x 10 microscopic magnification Fig 2: Fibroid uterine tissue stained with Masson’s trichrome viewed under 10 x 10 microscopic magnification The microscopic slide (Fig. 1) shows a normal uterus tissue that was stained with Masson’s trichrome, which showed the nuclei stained black, smooth muscle stained red and the collagen fibres stained blue.   Figure 2 shows a uterus tissue specimen stained with Masson’s trichrome that revealed excessive amount of collagen stained in blue, smooth muscle stained red and nuclei stained black.    Fig 3: Spleen tissue stained with Congo red showing amyloid deposits under 1010 microscopic magnification Fig. 4 Spleen tissue stained with Congo red adapted from Stevens and Lowe, (2000) Discussion Norwitz and Schorge   (2006) states that fibroids also referred to as Leiomyomata, are benign tumours of the myometirum of the uterus   that is mainly composed of smooth muscle and extracellular fibrous material such as the collagen, Fibroids do not   invade surrounding tissues or organs and they can occur in different locations within the uterus (Lark, 1996). The symptoms include heavy periods, frequent urination, constipation, bloating and backache (Tulandi, 2003) Masson’s trichrome was used to stain the uterus tissue (Fig. 1) which showed the collagen stained in blue, smooth muscle and erythrocytes stained red and the nuclei appeared black. MT stain revealed that the normal uterus tissue (Fig. 1) had a small amount of collagen present whereas the other uterus tissue (Fig. 2) showed an elevated amount of collagen stained in blue which suggested fibrosis. MT is an advantageous technique in medicine as it allows comparing the degree of fibrosis before and after the treatment biopsies to show if the treatment has been effective and successful. It is a routine stain for kidney and liver biopsies and this can be used on paraffin fixed sections as well as on frozen sections. Kambic et al., (1986) describes that there are different types of collagen and their organization is better shown using Sirius red with polarized light. Sirius red is a hydrophilic dye, in which type I collagen appears orange or red whereas type III collagen appears green (Kumar, 2005). Congo red was used to stain a spleen tissue section where figure 3 showed amyloid deposits in pink and nuclei in blue. Fig. 4 revealed a high amount of amyloid deposits in pink which suggested amyloidosis that is the disorder caused by abnormal deposition of intracellular or extracellular insoluble amyloid which changes the normal tissue function (Stevens and Lowe, 2000). Special stains is an important tool for pathologists   as it allows to the microscopically view and identify cells, tissues and microorganisms, providing an alternative to immunohistochemistry, flow cytometry and various other diagnostic techniques. References Bancroft, J. D. Gamble, M.   (2008).   ‘Theory and practice of histological techniques’.   [Online].   (6th ed).   Philadelphia, PA : Churchill Livingstone/Elsevier.   Available from: http://books.google.co.uk/books?id=Dhn2KispfdQCprintsec=frontcoverdq=Theory+and+practice+of+histological+techniqueshl=enei=ifGETZKEPcWwhAfSvPW_BAsa=Xoi=book_resultct=resultresnum=1ved=0CC8Q6AEwAA#v=onepageqf=false.   [Accessed 7th March 2011]. Bancroft. J. D. Cook, H. C.   (1995).   ‘Manual of histological techniques and their diagnostic application’.   Edinburgh [u.a.] : Churchill Livingstone. Bass, P., Burroughs, S. Way, C.   (2005).   ‘Systematic pathology : a clinically-orientated core text with self assessment’.   Edinburgh : Elsevier Churchill Livingstone. Bely, M. (2006). Histochemical differential diagnosis and polarization optical analysis of amyloid and amyloidosis TheScientificWorldJournal. 6, p.154-168. Carson, F. L.   (2001).   ‘Histotechnology : a self-instructional text’.   (2nd ed).   Chicago : ASCP Press. Cook, D. J.   (2006).   ‘Cellular pathology : introduction to techniques and applications’.   (2nd ed).   Bloxham: Scion Publishing Limited. http://onlinelibrary.wiley.com/doi/10.1046/j.1440-1827.2003.01513.x/abstract Kiernan, J. A.   (2007).   ‘Histological and histochemical methods’.   (4th ed).   Cold Spring Harbor (N.Y.) : Cold Spring Harbor Laboratory Press. Mohan, H.   (2005).   ‘Essential pathology for dental students’.   [online]. (3rd ed).   New Delhi : Jaypee Brothers.   Available from: http://books.google.co.uk/books?id=HmkTtLyxXF8Cprintsec=frontcoverdq=essential+pathology+for+dental+studentshl=enei=xRCCTaiHMs24hAezp6G8BAsa=Xoi=book_resultct=bookthumbnailresnum=1ved=0CDAQ6wEwAA#v=onepageqf=false. [Accessed: 11th March 2011]. Odze, R. D. Goldblum, J. R.   (2009).   ‘Surgical pathology of the GI tract, liver, biliary tract and pancreas’.   [Online].   (2nd ed).   Philadelphia, PA : Saunders/Elsevier.   Available from: http://books.google.co.uk/books?id=8ITX093f1j0Cpg=PA1143dq=Masson%27s+trichrome+staining+in+liverhl=enei=OB2GTYuVLYuqhAfJ_6m8BAsa=Xoi=book_resultct=book-thumbnailresnum=2ved=0CDgQ6wEwAQ#v=onepageq=Masson%27s%20trichrome%20staining%20in%20liverf=false.   [Assessed 16th March 2011] Rocken, C. Eriksson, M. (2009). Amyloid and amyloidoses Der Pathologe. 30, (3), p.182-192. Rubin, R. Strayer, D. S.   (2008).   ‘Rubin’s Pathology : clinicopathologic foundations of medicine’.   [Online].   (5th ed).   Philadelphia [u.a.] : Lippincott Williams Wilkins.   Available from: http://books.google.co.uk/books?id=kD9VZ267wDECpg=PA990dq=mechanism+of+congo+red+stainhl=enei=ADGFTcSQDZGJhQf-n5iuBAsa=Xoi=book_resultct=book-thumbnailresnum=4ved=0CEUQ6wEwAw#v=onepageq=mechanism%20of%20congo%20red%20stainf=false.   [Assessed 7th March 2011]. Sen, S. Basdemir, G. (2003). Diagnosis of renal amyloidosis using Congo red fluorescence Pathology international. 53, (8), p.534-538. Slauson, D. O.   Cooper, B. J.   (2002).   ‘Mechanisms of disease : a textbook of comparative general pathology’.   [Online].   (3rd ed).   St. Louis, MO. [u.a.] : Mosby.   Available from : http://books.google.co.uk/books?id=vRhtM0UMUh4Cpg=PA5dq=special+stainshl=enei=-vSETaMeqJKEB83RwccEsa=Xoi=book_resultct=book-thumbnailresnum=1ved=0CCoQ6wEwADgK#v=onepageq=special%20stainsf=false.   [Accessed 4th March 2011]. Young B., Lowe, J. S, Stevens, A. Heath, J. W. (2006).   ‘Wheater’s functional histology : a text and colour atlas’.   (5th ed).   Edinburgh : Churchill Livingstone Tulandi, T.   (2003).   ‘Uterine fibroids : embolization and other treatments’.   [Online].   Cambridge : Cambridge University Press.   Available from: http://books.google.co.uk/books?id=fZ8eha5yIfcCprintsec=frontcoverdq=fibroidshl=enei=oyOGTfnfMJGGhQeY_92_BAsa=Xoi=book_resultct=book-thumbnailresnum=7ved=0CGAQ6wEwBg#v=onepageqf=false.   [Assessed 15th March 2011]. Stevens, A. Lowe, J.   (2000).   ‘Pathology’.   (2nd ed).   Edinburgh [u. a.] : Mosby Starr, C., Evers, C. A. Starr, L.   (2011).   ‘Biology : concept and applications’.   [Online].   (8th ed).   United States : Cengage Learning.   Available from: http://books.google.co.uk/books?id=_16xbB2Py_UCpg=PA454dq=connective+tissuehl=enei=zYeITdaEAsywhAf61cm6Dgsa=Xoi=book_resultct=book-thumbnailresnum=10ved=0CFYQ6wEwCTgK#v=onepageq=connective%20tissuef=false.   [Assessed 8th March 2011]. Lark, S. M.   (1996).   ‘Natural treatment of fibroid tumors and endometriosis : effective natural solutions for relieving the heavy bleeding, cramps and infertility that accompany these common female problems’.   New Canaan, Conn : Keats Pub. Norwitz, E. R. Schorge, J. O.   (2006).   ‘Obstetrics and Gynaecology at a glance’.   (2nd ed).   Malden, Massachusetts : Blackwell. Kumar, R. K. (2005). Morphological methods for assessment of fibrosis Methods in Molecular Medicine. 117, p.179-188. Kambic, H. E., Kantrowitz, A. Sung, P.   (1986).   ‘Vacular graft update : safety and performance, a symposium’. [Online].   Philadelphia, PA : ASTM.   Available from: http://books.google.co.uk/books?id=NU0cVwIPk_oCpg=PA162dq=limitations+of+collagen+stainhl=enei=AEKLTcmzMsmYhQe1hJHEDgsa=Xoi=book_resultct=resultresnum=10ved=0CFsQ6AEwCQ#v=onepageqf=false.   [Assessed 20th March 2011].

Presentation paper Essay Example | Topics and Well Written Essays - 750 words

Presentation paper - Essay Example However, merit pay has been used to develop the standard payment structure that is common and applicable to all the employees (World at Work 60). Merit pay is as described as pay for performance based on the results set on a standard operative module. It is an approach to compensation that rewards well performing employee. It focuses on offering additional pay for the best performing employees. Despite the challenges, the merit pay system has several advantages. First, it enables the employer to differentiate between high and low performers in the company. Unlike the profit sharing or bonus pay schemes, it allows the employer to differentiate between performances of employees. While there are several programs and schemes are developed to reward overall performance of employees, merit pay offers compensation for strong performers. Merit pay allows the employer to recognize individual performance once meaning to continue benefiting from the scheme the employee must be able to continue the performing perfectly (Jiang, Xiao and Qi 67). Despite the numerous advantages of the scheme, it has been found that it does not offer a better support mechanism to the employees and the employer. The failure to address the essential issues that may affect performance both the group and individual makes the scheme non-effective. The scheme lacks accuracy affecting its ability to differentiate the ability of the individual employees. The success of the scheme has been reduced by the increasing dynamism in human behavior and factors that affect performance. The merit pay structure is different and creates a serious challenge in managing workers. The use of the total reward system has taken over the development of compensation structures. The total reward scheme is a program developed, by employers, to attract, motivate, and retain employees. The main focus of the program is to include everything the employee perceives to be value resulting from the employment relationships. The con cept has been advanced tremendously through evaluation and restructuring of the process of rewarding employees. When developing a total reward system, analyzing the need of every employee in the team (Jiang, Xiao and Qi 112). The development of a total reward scheme involves six steps with the first phase of the process in analyzing. The process of analyzing the needs of the employees includes the examining of the current policies. After analysis, the design process will involve the determination of compensation and the compensation strategies that can be employed in the process. During the design process, all the available approaches in total reward schemes. After the design, of the total reward scheme, the development of the plan and operation strategy involves the use of the various methods (World at Work 45). After the creation of the necessary plan and strategy, the plan must be communicated to the employees, so that they understand the reward scheme. Additionally, communicatio n in the company is vital because of the various reasons. Communication facilitates the development process, and the reasons of promotion and wage level setting. The success of the total reward scheme will depend on the various factors including the management design of the process (World at Work 213). The inclusion of all the factors that affect motivation and employee welfare will ensure that the total reward scheme is perfect. In conclusion, the total reward scheme is based on the inclusion of all