Alexis+S.



= The human digestive system- Post #1, March 2016 =

The human digestive system is a complex series of organs and glands that process food. Our digestive system is made up of the gastrointestinal tract, liver, pancreas and gallbladder. It is essentially a long, twisting tube. The GI tract is a series of hollow organs, made up of the mouth, esophagus, stomach, small intestine, large intestine and anus.

The digestive process
The mouth is the beginning of the digestive tract. Food is partly broken down by the process of chewing as well as by the chemical action of salivary enzymes. These enzymes are produced by the salivary glands, the mix with food and break down starches into smaller molecules.

After being chewed and swallowed, the food enters the **__esophagus__**. The esophagus is a muscular tube extending from the pharynx to the stomach. The esophagus delivers food to the stomach by a series of contractions called peristalsis. This muscle movement gives us the ability to eat or drink even when upside down. Just before the connection to the stomach there is a "zone of high pressure," called the lower esophageal sphincter, it is a "valve" used to keep food from passing backwards into the esophagus.

The __**stomach**__ is a large, sack-like organ that churns food and covers it in gastric acid (a very strong acid). Chyme is the term used to describe food that is party digested and mixed with stomach acids. When it leaves the stomach, food has the consistency of a liquid or paste. From there the food moves to the small intestine.

The __**small intestine**__ is a long tube loosely coiled in the abdomen, if spread out it would be more than 20 feet long. It is made up of three segments: the duodenum, jejunum and the ileum. The small intestine continues the process of breaking down food by utilizing enzymes released by the pancreas, as well as bile from the liver (bile is a compound that aids in digestion of fat and eliminates waste products from the blood). Peristalsis also plays a role in this organ, by moving food through and mixing it with digestive secretions. The duodenum is mostly responsible for continuing to break down food, while the jejunum and ileum absorb nutrients into the blood stream.

The helpers: **Pancreas**- The pancreas secretes enzymes into the small intestine that help break down protein, fat and carbohydrates in the food we eat **Liver**- It's 2 main functions in the digestive system are to make and secrete bile as well as to cleanse and purify blood from the small intestine containing the nutrients just absorbed. **Gallbladder**- This pear shaped organ sits under the liver and is responsible for storing bile. During a meal. the gallbladder contracts, and sends bile to the small intestine

The small intestine connects to the __**large intestine**__, sometimes referred to as the colon. It is a 5-6 foot long muscular tube that consists of the cecum, the ascending colon, the transverse colon, the descending colon, the sigmoid colon and finishes at the rectum. Waste left over from the digestive process is passed through the colon by peristalsis. It begins in a liquid state, and as water is removed to forms solid stool. This stool is stored in the sigmoid colon until it is emptied into the rectum, which usually occurs once or twice a day. The stool, made of food debris and bacteria, usually takes 36 hours to get through the large intestine. The bacteria in the stool is very useful because it protects against harmful bacteria, synthesizes some vitamins and processes waste products and food particles. As the descending colon becomes full of stool ( also referred to as feces) it empties into the rectum and the process of elimination begins

The __**anus**__ is the last part of the digestive tract, and it is made up of the pelvic floor muscles and 2 anal sphincters. The pelvic floor muscle creates an angle between the rectum and the anus, which stops stool from coming out freely. The anal sphincter prevents you from going to the bathroom when you are asleep or otherwise unaware of the presence of stool. This is the final portion of the digestive system.

** Why is digestion important? ** Digestion is vital for breaking down food into molecules, which the body then uses for energy, growth and cell repair. Everything we consume must be converted to smaller molecules before the blood stream can absorb them and carry them to cells throughout the body. Our bodies breakdown nutrients from food and drinks into: **carbohydrates, protein, fats and vitamins.**

Carbohydrates- sugars, starches and fiber found in many foods. Depending on their chemical structure they are called simple or complex. Simple carbohydrates include sugars found naturally in foods, for example fruits or vegetables. Complex carbohydrates are starches and fiber found in whole grain breads or legumes for example.



Protein- Meat, eggs and beans are examples of food that contain large molecules of protein that are digested into smaller molecules called amino acids. The amino acids are absorbed through the small intestine into the blood, which then carries them throughout the body.

Fats- fat molecules help the body absorb vitamins and are a rich source of energy. During digestion fat molecules are broken down into fatty acids and glycerol. Examples of healthy fats are olive and sunflower oil, while butter and shortening are examples of unhealthy fats.

Vitamins- Each vitamin plays a different role in the body's growth and health. Fat soluble vitamins are stored in the liver and fatty tissues (vitamin A, D, E and K) and extra water soluble vitamins are flushed out in urine.

** Digestive system diseases ** There are many conditions that can affect the gastrointestinal tract. Two common conditions are irritable bowel syndrome and celiac disease.

Irritable bowel syndrome- Affects the muscles of the intestines and can cause gas, abdominal pain, diarrhea or constipation. This can cause discomfort but most people can control their symptoms through diet and medication

Celiac disease is recognized as one of the most common chronic diseases in the world. People with the disease are advised to eliminate any foods containing gluten as it damages the lining of the small intestine.

It is vital to maintain a healthy digestive system, so here are a few tips: Eat a high-fiber diet Incorporate insoluble and soluble fiber Limit foods that are high in fat Choose lean meats Incorporate probiotics into your diet Eat on schedule and stay hydrated

media type="youtube" key="-Zyk0H1HmjA" width="408" height="323" align="center"

This video gives a visual representation of food travelling through the digestive system

Further Reading:

http://scienceline.ucsb.edu/getkey.php?key=4523 This site discusses what it would like if humans did not have a digestive system https://www.ucsfhealth.org/conditions/digestive_disorders/ This site explores common digestive disorders and their symptoms and treatments http://stemcellfoundation.ca/en/diseases/crohns-disease/ This site discusses the future of treating Crohns disease with stem cells http://www.mayoclinic.org/diseases-conditions/lactose-intolerance/basics/definition/con-20027906 This site looks at why people are lactose intolerant and the symptoms

Sources sited:

https://www.innerbody.com/image/digeov.html http://www.niddk.nih.gov/health-information/health-topics/Anatomy/your-digestive-system/Pages/anatomy.aspx http://www.livescience.com/22367-digestive-system.html http://www.celiac.ca/?page_id=88


 * Genetics and Cancer- Post #2 May 2016 **

//Cancer is defined as a disease of abnormal gene function.//

Certain types of cancer run in some families, but most cancers cannot be clearly linked to the genes inherited from our parents. Sometimes cancer is caused by an abnormal gene that is being passed along from generation to generation. What is being inherited is the abnormal gene that can lead to cancer, not the cancer itself. Approximately 5% to 10% of all cancers result directly from gene mutations inherited from a parent. Gene changes that start in a single cell over the course of a person's life are what cause most cancers.

Genes are pieces of deoxyribonucleic acid (DNA) and they contain the instructions on how to make the proteins the body needs to function, when to destroy damaged cells, and how to keep the cells in balance. They are what determine traits such as hair color, eye color, and height, but can also affect your chance of getting certain diseases, such as cancer. An abnormal change in your genes is called a mutation, gene mutations can be harmful, beneficial or have no effect.


 * The two types of mutations are acquired and inherited **

. An inherited gene mutation is in the egg or sperm that made the child. After the egg is fertilized by the sperm, it creates a zygote that divides to eventually create a fetus. Because all the cells in the body came from this first cell, the mutation is in every cell in the body. It can be passed on to the next generation, as the mutation is also in the eggs and s perm.



Some inherited gene mutations have been linked to breast cancer. These include mutations in the following genes:
 * //BRCA1//
 * //BRCA2//
 * //p53//
 * //CHEK2//
 * //ATM//
 * //PALB2//

Acquired mutations occur during a person's life and are only present in certain cells. These changes can be caused by environmental factors or other factors that damage the cell's DNA such as UV radiation from the sun, smoking and exposure to certain chemicals. They can also occur if a mistake is made when DNA copies itself during cell division.

Proto-oncogenes are genes that normally help cells grow. When a proto-oncogene mutates or there are too many copies of it, it can become permanently turned on or activated when it is not supposed to be. When this happens the cell grows out of control, which can lead to cancer, this gene is then called an oncogene.

Tumor suppressor genes are genes that slow down cell division, repair DNA mistakes, and tell cells when to die. When these genes don't work correctly, cells can grow out of control, which can lead to cancer. An important difference between oncogenes and tumor suppressor genes is that oncogenes result from the activation of proto-oncogenes, but tumor suppressor genes cause cancer when they are inactivated.




 * How genes can help in the diagnosis and treatment of cancer **

Finding certain genes or gene mutations can be helpful in diagnosing cancer, monitoring the effects of treatment, learning about prognosis, and in treating cancer.


 * Cancer diagnosis and monitoring treatment **

Select mutations are commonly found in the cells of some of cancers. Locating certain mutations in cells can confirm the diagnosis of the cancer. Testing cells for the mutation can also be used after diagnosis to see how or if the cancer is responding to treatment.

Some drugs don’t help patients at all if the cancer cells have certain gene mutations. For example, Erbitux and Vectibix are drugs used to treat advanced cancers, but for patients with mutations in the KRAS gene, these drugs don't help, so doctors must check the cancer cells for these mutations before they administer either of these drugs.
 * Gene testing to help predict if a drug will work **


 * Genes and cancer prognosis **

In some cancers, specific gene changes can be used to predict which patients are likely to have a better or worse outcome. This can help guide the intensity of treatment.

A genetic counselor or doctor can help an individual or family understand their genetic test results. Counseling may include discussing recommendations for preventive care and screening, referring the them to support groups or providing emotional support.

media type="youtube" key="5u50lX30eU0" width="560" height="315" This video helps to further explain how cancer can be inherited

Further Reading:

http://www.cancer.gov/about-cancer/causes-prevention/risk The following are the most common risk factors for cancer

https://www.genome.gov/19516567/faq-about-genetic-testing/ This site has frequently asked questions about genetic testing and the benefits of it

http://www.cancerresearchuk.org/about-cancer/cancer-symptoms This site lists the key signs and symptoms of breast cancer

http://www.webmd.com/breast-cancer/ This site focuses on breast cancer specially, the types and symptoms

Sources cited

http://www.facingourrisk.org www.cancerresearchuk.org www. cancer.ca www.cancer.net

=Antibiotic resistance: Over prescribed and under effective=

Post #3 June 2016


Antibiotics have revolutionized medicine in many respects, and countless lives have been saved; their discovery was a turning point in human history. Regrettably, the use of these wonder drugs has been accompanied by the rapid appearance of resistant strains. The genetic capacities of microbes have benefited immensely from mans over use of antibiotics.

Antibiotics are compounds that either:
1. kill bacteria directly (bacteriocidal)

2. inhibit their ability to grow and reproduce

How do antibiotics inhibit bacterial growth? Antibiotics stop or interfere with cellular processes that bacteria rely on for growth and survival, like:
-stopping/slowing production of the bacterial cell wall that protects the cell from the external environment

-interfering with protein synthesis by binding to the organelle that builds proteins, one amino acid at a time

-Disrupting metabolic processes: synthesis of folic acid, which is B vitamin that bacteria need to thrive

-Blocking synthesis of DNA and RNA

Antibiotics stop working because bacteria come up with methods of countering these actions, such as:
-Stopping the antibiotic from getting to its target: Think of when you're trying to avoid someone, you hide in public when you see them and don't answer their text messages. Bacteria keep an antibiotic from reaching its target, by preventing it from being taken up at all. Bacteria do this by changing the permeability of their membranes or by reducing the number of channels available or open for the antibiotic to enter in through. Some bacteria use energy from ATP to use pumps that shoot antibiotics out of the cell, if they get in.

-Changing the target Many antibiotics work by attaching to their target and preventing it from interacting with other molecules inside the cell. Some bacteria respond by changing the structure of the target, or sometimes replacing it with another molecule all together, so that the antibiotic can no longer recognize it or grab onto it.

-Killing the antibiotic Instead of pushing the drug out or blocking it, some bacteria survive by destroying their enemy directly. For example, certain bacteria can produce beta-lactamases enzymes that stomp out penicillin.


 * How do bacteria gain these habits?**

Some bacteria are just using their own capabilities, but many of these bacteria did not start out as having this resistance. Bacteria can become resistant by getting a copy of a gene encoding (an altered protein or enzyme) from other bacteria, even from those of a different species. There are a number of ways to get a resistance gene:

-During transformation: microbes can join together and transfer DNA to each other -Plasmids: one plasmid can encode resistance to many different antibiotics

- By scavenging DNA remnants from dead bacteria

- Transposon: a DNA sequence that can change its position within a genome, sometimes creating or reversing mutations and altering the cell's genome size.

Once a bacterium gets a resistance gene stuck into its chromosomal DNA or picks one u p in a free-floating plasmid, all of its offspring will inherit the gene and the resistance that comes with it. These resistance genes thrive and spread throughout bacterial population. This is explained by Darwin's idea of the survival of the fittest, bacteria with these genes survive and outgrow susceptible variants.

How humans contribute to the problem:
-Not taking all the pills we are prescribed ( even if we feel better). If you stop taking your medicine too early, your immune system may not be able to kill off what bacteria may be left, and any resistant bacteria will be able to breed and spread to other people . - Insisting on getting antibiotics from the doctor to treat a cold or the flu. Antibiotics are completely ineffective against viruses. AND even worse, antibiotics can't tell the difference between bacteria that are good for us and bacteria that cause disease. We actually co-exist with a wide variety of harmless and beneficial bacteria each day and whenever you take antibiotics, you kill off some of these beneficial bugs. So using antibiotics when you don't actually need to puts you at risk for other, more serious diseases.

-Saving left over pills and attempting to self medicate (BAD idea!) Not every antibiotic will work for every kind of infection. Your doctor prescribed a specific drug based on the kind of infection you have, and also selects and dosage and length of treatment time.

Can bacteria lose their antibiotic resistance?
Antibiotic resistance traits can be lost, but this process occurs more slowly. If the pressure that is applied by the presence of an antibiotic is removed, the bacterial population can potentially go back to a population of bacteria that responds to antibiotics.

**Superbugs**
Doctors often use phrases like "multidrug-resistant bacteria." That's because a superbug isn't necessarily resistant to all antibiotics. It refers to bacteria that can't be treated using two or more antibiotics.

media type="youtube" key="znnp-Ivj2ek" width="560" height="315" This video simplifies and explains how bacteria becomes resistant.

Further reading: http://chealth.canoe.com/channel/Infection/Overview/Superbugs-What-are-they-and-how-are-they-formed A stronger definition of what a super bug is and how they become so resistant http://www.thenakedscientists.com/HTML/questions/question/1000126/ A deeper look into how bacteria can lose their antibiotic http://www.cdc.gov/features/antibioticresistance/ Things we can do to help prevent future antibiotic resistance http://www.who.int/mediacentre/news/releases/2014/amr-report/en/

Sources: http://www.healthycanadians.gc.ca/drugs-products-medicaments http://www.who.int/mediacentre/commentaries/stop-antibiotic-resistance/en/ http://www.microbiologyonline.org.uk/ http://emerald.tufts.edu/med/apua/about_issue/about_antibioticres.shtml