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Introduction to the Human Body Level 3

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Topics: DNA, Cell, Gene, Cloning
Leanne Butler 02-12-09

Anatomy and Physiology

Introduction to the Human body

Introduction

The human body is such an interesting machine, the way it is structured and how it works is educational. There is so much to learn about the human body and up until today scientists are still under going medical research. There are a lot of questions people would like to know about how their body works. The report will include the following structures: • Deoxyribonucleic Acid (DNA) • An Organelle • The cell membrane

It will also evaluate the functions of the following structures: • The cell • Body tissue • Body system

Findings

1.1Deoxyribonucleic Acid (DNA) 1.2An Organelle 1.3The Cell Membrane 2.1 The Cell 2.2 Body Tissue 2.3 Body System 3.1 Ultrasound 3.2 Gastroscopy 3.3 Similarities, benefits and risks of the two procedures 4.1 Cloning

1.1 Deoxyribonucleic Acid (DNA)

Deoxyribonucleic Acid is a molecule, which passes down information, required for the growth, development and reproduction of an organism. It is passed from adults to their children (offspring). DNA is found inside the nucleus of the cell and due to there being a lot of DNA molecules inside a cell; each molecule must be tightly packed. This then becomes a chromosome.
DNA found in the cell nucleus is referred to as nuclear DNA, a human’s complete set of nuclear DNA is called its genome.
A genome consists of 23 pairs of chromosomes; these chromosomes together consist of 3.1 billion bases of DNA sequence.

DNA consists of chains called nucleotides. Theses are made up of three parts: a phosphate group, a sugar group and one of four types of nitrogen bases. The four types of nitrogen bases found in nucleotides are: adenine (A), thymine (T), guanine (G) and cytosine (C). The order or sequence these bases come in, is due to that specific strand of DNA .Each ladder in the DNA is made of two-linked bases. Only (A) and (T) can link together and (G) and (C) can link together. Adenine and Guanine are purines. Purines are double ringed structures. Cytosine and Thymine are singled ringed structures and are known as pyramidines. Each DNA sequence that contains instructions, to make a protein, is known as a gene.

DNA is used to make proteins in a two-step process. Enzymes read the information in a DNA molecule and then transcribe it into an intermediary molecule called messenger ribonucleic acid (RNA), or mRNA. Next the information in the molecules is translated into the “language” of amino acids, which are the building blocks of proteins. (Appendix i)

1.2 An Organelle

An organelle is a discrete structure within a cell, as chloroplast or acentriole. It is characterised by having specialised functions, a usually distinctive chemical composition and an identifying molecule structure: often found in large numbers in aparticular cell. Organelles have specific roles to play in how cells work. Some organelles are separated from the rest of the cell by lipid bi-layers similar in structure to the cell membrane. An example of an organelle is ribosomes. The function of ribosomes is the assembly of proteins, in a process called translation. Ribosomes do this by catalysing the assembly of individual amino acids into polypeptide chains; this involves binding a messenger RNA and then using this as a template to join together the correct sequence of amino acids. (Appendix ii)

1.3 The Cell Membrane

All cells are surrounded by a cell membrane, and its primary purpose is to keep the contents of the cell all together. Cell membranes are like many other organelles of a cell because they exist for a specific job. This job is to monitor and control everything that enters and leaves the cell. The cell membrane is made up of lipid molecules called phospholipids. These molecules all have one polar head and two hydrocarbon tails according to cellupedia. There are three main classes of lipid molecules, which make up a cell membrane. These classes include phospholipids, glycolipids and cholesterol. The particular amount of these lipids varies across different membranes.

The cell membrane is mobile and moves along “groves” which are set paths the membrane follow. Membranes are composed phospholipids, proteins and carbohydrates arranged in a fluid mosaic structure. The phospholipids form a thin, flexible sheet, while the proteins float in the phospholipids sheet and the carbohydrates extend out from the proteins. (Appendix iii)

2.1 The Cell

A cell is the smallest unit of living matter. All living things including plants and animals are made up of cells. Cells are made of atoms, which are the smallest units of matter. There are many different kinds of cells. All cells have a “skin” called plasma membrane, protecting it from the outside environment. The cell membrane regulates the movement of water, nutrients and wastes into and out of the cell. Inside of the cell membrane are the working parts of the cell. At the centre of the cell is the cell nucleus. The cell nucleus contains the cell’s DNA, the genetic code that coordinates protein synthesis. In addition to the nucleus, there are many organelles inside of the cell, small structures that help carry out the day to day operations of the cell. Organelles are groups of complex molecules that help a cell survive. There are many functions that the cell has to carry out: molecule transport, reproduction, energy conversion and many more. I have chosen to discuss reproduction as one of the cells functions.

Reproduction

One of the main purposes of human beings and living creatures is to survive. To be able to do this the cells must be able to reproduce. Reproduction allows a species of cells to increase its population and have a higher competitive advantage. Second, sexual reproduction can help introduce genetic variation into specie which can be beneficial in the long run. Example of this might be the difference in looks between individuals.

Cells can reproduce in two ways, mitosis and meiosis. In mitosis, the resulting daughter cell is an identical clone of the original cell. Mitosis is mostly used by somatic cells (cells of the body). Meiosis however, is the form of sexual reproduction and only occurs in gametes (reproductive cells).

Mitosis

If an organism is to live and grow up it must reproduce. Cell division serves an important role in organisms’ health and growth. Cell division begins with interphase, when the cell replicates all of its genomic and cytoplasmic material and prepares for division. After the cell enters the 4-phased mitosis. To see the similarities between mitosis and meiosis see appendix. (Appendix IV)

2.2 Body Tissue

Body tissue is a layer of cells that perform a function. Different types of tissues have different structures that are specific to that function. Tissues can be held together by a sticky coating called an “extracellular matrix”.
The Latin word for tissue is derived from the verb texere, “to weave”.
The major tissue types in the human body: • Connective • Muscular • Nervous System • Lymphatic

The type of tissue that has been selected is muscle tissue.

Muscle Tissue

Muscle tissue contains a number of microfilaments composed of actins’ and myosin, which are contractile proteins. There are three types of tissue: Cardiac muscle, skeletal muscle and visceral (smooth) muscle.

Cardiac muscle is found in the heart. The cells are joined to one another by intercalated discs which allow the synchronisation of the heartbeat.

Skeletal muscle is attached to the bones by tendons. Skeletal muscle is striated muscle. Unlike cardiac muscle, the cells are not branched.

Visceral muscle is found in: the arteries, the bladder, the digestive tract and in many other organs. Visceral muscle contracts slower than skeletal muscle, but the contraction can be sustained over a long period of time. (Appendix v)

2.3 Body System

There are 11 systems in the body they are as follows:
The Circulatory system
Digestive system
Endocrine system
Immune system
Lymphatic system
Muscular system
Nervous system
Reproductive system
Skeletal system.
(Appendix VI)

The system that has been selected is ‘The Reproductive System’.

Reproductive System

Females have sex organs of: ovaries, fallopian tubes, uterus and vagina. Whereas the males sex organs are: vas deferens, seminal vesicles, prostate and the penis.

In the reproductive system a female needs a male to fertilise her egg. There are two types of sex cells known as gametes, the male gamete is sperm and the females’ gamete is the egg. The females’ vagina has several functions: used for sexual intercourse, the pathway that the baby comes out at childbirth, as the route for the menstrual blood (period) to leave the body from the uterus and for a tampon to be used during the menstrual cycle.

The menstrual cycle lasts for around 28 days, during this cycle a egg is released from the females’ ovaries once every month and goes down the fallopian tubes to be fertilised. If the egg does not get fertilised it dries up and two weeks later leaves the body through the vagina, which causes the female to have her period. A period is forms of blood and tissue from the inner lining of the uterus. A period can last anything up to 5 days or longer. Females will not have a period until they have started puberty; puberty usually starts when females and males are aged around 11-14.
If the male and female sex cell are fertilised the egg that is released will not dry up and the female will not have a period. The egg will then make its way to the uterus and grow into a foetus. (Appendix vii)

3.1 1st diagnostic procedure- Ultrasound

Ultrasound is a non-invasive technique that may be used during pregnancy for finding out the sex of the foetus and whether there is more than one foetus, ultrasound also identifies the measurements of the foetus. The sonographer, is the person who carries out the procedure, she or he can usually tell you how many weeks old your foetus is.

The mother usually has an ultrasound twice in nine months, the first at 3 months and the second at 5 months. Usually at the second scan you will be able to find out if the baby is a boy or a girl. Ultrasound can find any complications or problems that the baby might have during the pregnancy. They put a cold gel on the mothers’ bump and press the transducer across the bump to see inside of the belly. Having experienced this procedure confirms that ultrasound is a very accurate method of confirming all of the above. (Appendix viii)

3.2 2nd diagnostic procedure- Gastroscopy

Gastroscopy is used if a person is suffering problems, such as severe heartburn or indigestion. An individual may then be required to have a Gastroscopy. It is a diagnostic procedure that allows doctors to look at the upper part of the digestive system. The doctor uses a tiny camera on the end of a flexible tube which is called an endoscope.

It is then fed down your throat and down through the tube that carries your food to your stomach which is called oesophagus. It is then into your stomach. Once in place the camera shows the image onto a screen for the doctor to diagnose any problems.

It usually takes between 5-20 minutes to perform the procedure. It is usually performed at an outpatient department, which means you can go home the same day. You should not eat anything for six hours before the procedure as the stomach needs to be empty. (Appendix ix)

3.3 Similarities, benefits and risks of the two diagnostic procedures

The two diagnostic procedures are only similar in a few ways. When both procedures are performed you get to leave the hospital the same day. Both procedures take no less than 5 minutes and no longer than 20 minutes. There should be no pain in either of the procedures performed. However, Ultrasound does not have any risks whereas Gastroscopy has a few risks. Some of the benefits of having an Ultrasound are: • There are no needles or injections and the procedure is painless • Ultrasound imaging uses no ionizing radiation • Causes no health problems • Gives a clear picture of soft tissues, that do not show up in an x-ray • There are no risks

Some of the risks for having a Gastroscopy are: • The individual may have a sore throat for a day or two afterwards, this is caused if the endoscope scrapes your throat • Small risk that the endoscope could tear your stomach which is known as perforation • Risk of chest infection or pneumonia is slightly higher than normal • When the endoscope is removed your likely to gag or rench (Appendix x)

4.1 Cloning

This is the topic which has been selected to discuss.
There are 4 types of cloning: Recombinant DNA technology or DNA cloning, reproductive cloning and therapeutic cloning. People are most familiar with reproductive cloning when it comes to talk about cloning.

Reproductive Cloning

Reproductive Cloning is a technology used to generate an animal that has the same DNA as an existing animal or a previous existing animal. Scientists transfer genetic material from the nucleus of a donor adult cell to an egg whose nucleus has been removed. The DNA from the reconstructed egg must be treated with chemicals or electric current in order to stimulate cell division. This process is known as “somatic cell nuclear transfer”. Once the cloned embryo reaches a suitable stage, it is then placed into the animals’ uterus where it continues to grow until birth.
Scientists have bee cloning animals for many years since 1952; hundreds of cloned animals such as sheep and cows exist today.

Scientists are hoping to be able to use cloning by generating tissues and organs to use for transplants. To do this the patient waiting for a transplant, would have DNA extracted from their body. This would then be inserted into an enucleated egg. After the DNA starts to divide, embryonic stem cells that can be transformed into a tissue would then be harvested. The stem cells would then be used to generate an organ or tissue, which is a genetic match to the patient

Reproductive cloning is contentious as it seeks to create a duplicate of an existing animal. Until the birth of Dolly the sheep in 1996, there was doubt that this would work in mammals, but now some scientists are trying to clone a human. Many ethical arguments against human cloning are caused by misconceptions. Many people seem to think that clones will have the same sort of characteristics and personalities as the person from which they were cloned. Also some people seem to believe that clone will be both physically and behaviourally the same as the donor. Many people also believe that cloning would lead to the loss of individuality however; cloned people have their own personality that is dissimilar from whom they were cloned according to the House Judiciary Committee.

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