Specialised Cells in Human Biology Essay Example for Free

Specialised Cells in Human Biology Essay â€Å"The cells in your body are tiny-a row of about forty would fit into 1mm. But although they are too small to see with the naked eye their complexity is remarkable. A single cell can be thought of as an organised chemical system, separated from its disorganised surroundings by a membrane† (Boyle et al 1999) First here is a brief summary of major eukaryotic organelles and their structures. The nucleus is the largest and most prominent organelle in the cell. It is usually spherical and about 10um in diameter. It contains the DNA and chromosomes and carries information that allows the cell to divide and carry out its cellular processes. Almost all eukaryote cells have a nucleus. The nucleolus is located in the nucleus it is 1-2 um. Its function is to manufacture ribosomes. The ribosomes are found either free in the cytoplasm or attached to the rough endoplasmic reticulum R. E. R, They are 20nm in size and their function is to synthesise the protein in the cell. The cell surface membrane controls the entry and exit of substances in and out of the cell. It is partially permeable. It separates’ the cells contents from the external environment. It is a double layer of phospholipid molecules around 7-10nm thick. Cytoplasm is a jelly like substance that fills the cell it is around 80% water. This is where cell activities occur and most chemical reactions take place. Organelles are suspended in it. The R. E. R. occurs throughout the cytoplasm, it has an extensive membrane network. Its function is to isolate and transport newly synthesised proteins. The mitochondrion is numerous in cytoplasm and there are usually up to 1000per cell. Its function is aerobic respiration and synthesises most of the A. T. P. for the cell. The smooth endoplasmic reticulum S. E. R. is found in small patches in the cytoplasm, they vary in size and their function is to synthesise lipids and steroids. The muscle cells (see figure 1) that are found in the muscles that move the bones at joints in the skeleton. These cells allow for movement like walking or running. The skeletal muscle is made up of specialised cells also referred to as muscle fibres. These cells are long and thin, these elongated cells are tubular in appearance. The cells contain several nuclei for the cell to contract and relax the muscle; the cell needs many nuclei as the nucleus contains the DNA the genetic information that carries the instructions for making each protein i. e. the first step in making proteins takes place in the nuclei. The actual building of the proteins takes place in the sarcoplasm otherwise known as the cytoplasm. There is lots of mitochondria in the cell this because it is needed foe aerobic respiration to create the A. T. P. energy that is needed for the muscle to contract and relax. It is surrounded by the cell membrane or the sarcolemma, filled with sarcoplasm. The sarcoplasm contains many thread like fibres known as myofibrils. These run along the length if the muscle fibres parallel. The sarcoplasmic retilum that is around each myofibril consists of a network of tubes that contain calcium ions these play a major role in bringing about muscle movement. The neurone is the functional unit of the nervous system. They form connections with other neurones. They can carry electrical impulses in one direction; receiving and transmitting information. The thicker the insulation the faster the electrical impulses travel. They are found in the brain or the spinal cord. They are long and thin in fact they are the longest cell in the body. They vary in shape and size depending on their position and function. The neurones running down your leg can be over one metre long. Although all neurones have a similar basic structure, see figure 2 which shows the structure of a typical motor neurone. It transmits signals to muscle fibres. The cell body contains cytoplasm, a large nucleus which is found at the end of the cell and other organelles. Coming off the cell body are as many as 200 thread like dendrites that make the area of the cell body larger, these allow many connections to be made to other neurones and one long limb called an axon. The dendrites bring impulses into the cell body while the axon brings impulses away to connect with other neurones or with effectors such as glands or muscles. A significant feature of a neurone is that their cell bodies contain nissi granules; these work to be a maintenance system that monitors the cell. They are also the site of protein synthesis in the cell. The axoplasm or the cytoplasm extends throughout the cell into the dendrites, synoptic bulbs, cell body and axon. Materials reach different parts of the neurone by axoplasmic transport. Most human cells are microscopic. The largest cell in the human body is the egg cell or the ova. This is just visible with the naked eye. It needs to be bigger than other cells as it needs the space to store food reserves. It is large in diameter at 0. 2mm and has a large cytoplasm this is packed with food reserves which allow the cell to divide before it implants in to the nucleus. It has a large nucleus (see figure 3) this is because it contains all the genetic material of the cell including all of the DNA, 23 chromosomes and all of the information necessary to make a complete human being in just nine months. .The egg cell is surrounded by several layers of cells and the complete unit is called a follicle. The production of egg cells oogenesis takes place within the ovaries of the developing female fetus. At birth a girl already has two million. These fuse with the male gametes called spermatozoa or sperm in a process known as fertilisation. The resulting cell the zygote develops inside the uterus nourished by the placenta into a new individual. The sperm (see figure 4) has a large nucleus; this is because it contains digestive enzymes it also contains the 21 chromosomes that must be delivered to the egg in order for the complete 42 chromosomes to be in the zygote, it also contains chemicals to penetrate the egg and carries genetic information. The sperm has many mitochondria this is because it needs a lot of energy for its long swim to the egg. It has a long tail called a flagellum that is a modified cilium that it uses for swimming to the egg cell. It is one of 50-200 million sperm that attempt the journey to the egg cell but only one can make it and fertilise the egg cell. When the sperm reaches the egg cell; digestive enzymes that are found on the tip of the sperm head are released when the bag splits releasing the enzymes which digest a pathway through any remaining follicle cells and the zona pellucida. Fertilisation has begun.

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The helmet and its improvements for safety. Bicycles, the one way we got to move around as kids, and as adults it is the one way we get around too, because cars are mainstream. Safety is an issue when it comes to bicycling and that why the helmet is an important factor when it comes to safety for bikes. Every year, in the U.S, nearly 900 persons die from injuries due to bicycle crashes and over 500,000 persons are being treated in emergency departments. Head injuries are by far the greatest concern for bicyclists, causing one third of emergency department visits, two thirds of hospital admissions, and three fourths of deaths. There are other injuries such as facial injuries, which occur at a rate nearly the same to head injuries. It is hard to trust that helmets would be protective against head injury, but establishing the real effectiveness of helmets is important. Since the beginning of cycling there have been head injuries. Head injuries increased as more roads were being paved. The materials used to pave the roads are macadam and asphalt and they are unforgiving when it comes to crashes. During the 1800’s high wheeler users in clubs started wearing pitch helmets, they noticed that head injuries were becoming a problem. A helmet made of crushable material such as Pith was likely the best option at the time. When impacting the ground the material would break, but there was fewer cars, roads and competitions back then, therefore it was designed for a single impact. At the turn of the century many Racing Cyclist began using â€Å"Helmets† made of leather-covered padding, initially with a ring of leather around the head and a wool ring above that. Soon enough the style had changed, the ring of leather around the head was supplemented by... ...may look, it can save your life or prevent any traumatic injuries. Technology is improving and the series of test being conducted too. Cycling clubs and racers are trying to protect themselves as much as they can, and it makes them happy to see that helmets will be improving as the years go by. In conclusion the helmet has been a huge help in preventing more head injuries. The helmet has been improved throughout the years and since it originated it has followed through with its purpose. We are in the year 2013 and yet scientist are trying to improve the helmet as much as they can, the future to come from the helmet is very bright. There are faster and stronger cars out there, so cyclist are bound to get hit more, the helmet is yet to get stronger. Personally helmets are a big part of me I enjoy cycling a lot, but I know there is a lot of safety that comes with it.

Madame Butterfly

Ali Appelbaum WGST 199-01 Professor Uman March 16, 2008 Society puts a strong focus on individuals who experience the act of cross-dressing to create an identity for themselves. The act of cross-dressing helps a person to feel comfortable with themselves because they are able to gain a sense of independence, confidence, and individuality. In the play M. Butterfly, by David Henry Hwang, constructing an identity is made through the character Song. By looking at Song’s appearance in M. Butterfly, we can see that clothing and disguise constructs an identity. The play, M. Butterfly uses the character Song to show the audience how cross-dressing is common, and can make one’s personality. Song cross-dresses from an Asian male, to an Asian female. Throughout the play Song plays the role of a female but expresses herself in a more confident, and independent way as an Asian female. This is because Song has had a gender cross to a women, she is able to demonstrate these qualities in her new identity she has formed. M. Butterfly is about a French diplomat, Gallimard and his love attraction for Song. Gallimard feels as though he’s never been in love, and has a hard time relating to women, until Song comes along. Song, playing the romantic role of Gallimard’s lover takes charge without Gallimard realizing a male was really wooing him the whole time. Song possesses traits of a female, which gives her confidence to pursue her relationship with Gallimard until he’s fallen in love. In the end, Song reveals herself for the man she is, but continues to act with more confidence and independence as a woman than as a man. In the play, you can see that disguise constructs an identity through the character Song. During a scene, Gallimard comments on Song’s feminine appearance and the other women he see’s in China. Song responds to Gallimard, â€Å"Please. Hard as I try to be modern, to speak like a man, to hold a Western woman’s strong face up to my own†¦ in the end, I fail. A small, frightened heart beats too quickly and gives me away. Monsieur Gallimard, I’m a Chinese girl. I’ve never†¦ never invited a man up to my flat before. The forwardness of my actions makes my skin burn† (1. 11 Hwang). This quotes shows that Song posses traits as a female and is proud. Although Song is a male, he has built himself a female identity from disguise. Confidence is expressed in Song’s remarks by telling in conversation how she believes she is more knowledgeable than Gallimard. Song also makes sure notice is taken of her delicate and pretty appearance. Song remarks back to Gallimard, â€Å"Your history serves you poorly, Monsieur Gallimard. True, there were signs reading â€Å"No dogs and Chinamen. But a woman, especially a delicate Oriental woman—we always go where we please. Could you imagine it otherwise? Clubs in China filled with pasty, big-thighed white women, while thousands of slender lotus blossoms wait just outside the door? The clubs would be empty. We have always held a certain fascination for you Caucasian men, have we not? (2. 4 Hwang). Song has shown to her audience that she has a strong confidence about the female body and face. She explains to Gallimard that her new identity, a delicate Oriental woman, is always welcomed in society. Song also feels a sense of power because although she is a man working for the Chinese government, she feels comfortable in her feminine identity. A conversation between Song and her advisor Comrade Chin demonstrates how Song has created has created an identity for herself in disguise. When Song is in quarters where she can act like man, she still acts in a feminine order, rather than a masculine tone. Chin asks Song, â€Å"†¦Is that home come you dress like that? † (2. 4 Hwang). Song responds by saying, â€Å"Like what, Miss Chin? † (2. Hwang). Chin remarks with what he believes is reality by saying, â€Å"Like that dress! You’re wearing a dress. And every time I come here, you’re wearing a dress. Is that because you’re an actor? Or what? † (2. 4 Hwang). Song reveals her identity by saying, â€Å"It’s a†¦ disguise, Miss Chin† (2. 4 Hwang). This conversation between Comrade Chin and Song shows the audience that Song is aware of the fact that she is a male, but possesses more of an interest in the feminine personality and ways of life because she is more confident.

The Concept of International New Ventures - 620 Words

Week 1 HIA Explain how the article builds on the seminal work of Oviatt and McDougall in their paper,. Describe and analyze the factors identified in the Zahra article as giving competitive advantage to new firms in the globalized economy. Do you agree that these are the key factors underlying success in the international business environment? Give reasons for your answer. International New Ventures (INV)are firms who target the international market while lunching their operations (Shenkar and Luo P 11) unlike the traditionally operating firms who target the domestic market before exporting to other countries. In their article, â€Å"Toward a Theory of International New Ventures†, published in 1994 Oviatt and McDougall defined the†¦show more content†¦The major factors overlooked by Oviatt and McDougall, and which build the competitive advantage are - according to Zahra- : 1- The Institutional environment 2- The economic Geography These factors consist in studying the country’s culture, assessing the market, hiring locals and establishing work contacts. In addition to that, Zahra considers that INV’s managers should demonstrate a high degree of openness and flexibility thus allowing the firm to function in the foreign environment. The same critics that Zahra has addressed to Oviatt and McDougall’s analysis applies on his list of factors contributing to the INV’s competitive advantage. We should acknowledge that every country has some economic or cultural specificity; therefore there are some universal business rules which apply on the entire global market. 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