Biology in regards to nutrition: What happens in the body - Lily Cramer

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Biology in regards to nutrition: What happens in the body

Most of us have covered the basics of digestion in our biology classes during middle school and/or high school, but it never hurts to have a refresher course. How do you get the nutrients out of the foods that you eat, and what do they do once they’re in your body? So let’s start out at looking exactly what your GI (gastrointestinal tract) does with all components of nutrition.

What is the Gastrointestinal Tract?

–       Your gastrointestinal tract is responsible for receiving food.

–       Receives food from your mouth onto the other organs for digestion and absorption.

–       It separates the nutrients from your food and releases them into your stomach and your small intestine through your blood.

–       You have microvilli and villi in your small intestine, which help facilitate the transfer of nutrients into your portal blood or for fatty acids, into your lymph.

–       Water absorption occurs in your colon, which is also called your large intestine.

–       The last thing your GI tract is responsible for doing is excreting waste. The indigestible matter of the food that you don’t utilize becomes waste product.


Digestive System

Digestion Destinations From Beginning to End

1. The mouth

–  In your mouth is where all digestion begins – mechanical and chemical.

– You chew your food and it mixes with saliva, which contains a starch-digesting enzyme.

– Your pharynx helps you swallow the chewed food where it’s mixed with the saliva as well.

2. The Esophagus

– After your mouth, food passes into your esophagus, which is the tube that connects your mouth to your stomach.

– The process of peristalsis ~ circular muscles that contract and push the bolus of food downward.

– There are also longitudinal muscles that contract which shortens the passageway ahead of the bolus with rhythmic contractions that continue to push food down the esophagus until it gets close to the stomach.

– Your body very slowly regulates. The direction that the food goes, and the pace at which it flows into your stomach and through your GI tract.

3. The Stomach

– When a wave of peristaltic contraction reaches the stomach. It allows it to relax. That opens the sphincter, and allows the bolus of food to empty into the stomach.

– When the bolus of food comes out of your stomach, it’s so far removed from what was originally food, that we refer to it as chyme. Chyme is moved by peristalsis, and is mixed by the rhythmic contractions of the intestine through a process called segmentation.

– The primary nutrients that are absorbed in the stomach include water and alcohol and minerals such as copper, iodide, fluoride, and molybdenum.

– There’s not a whole lot of digestion going on in the stomach, but rather there’s mechanical mixing. Your stomach is a highly acidic environment and it secretes a lot of  gastric juices.

– Here’s some of the gastric juices that your stomach makes.  There are four gastric juices: Hydrochloric acid, pepsin, lipase and mucus.

  1. The first one is hydrochloric acid, you sometimes see it abbreviated HCL. Hydrochloric acid denatures protein and activates
  2. Pepsin is an enzyme that digests protein.
  3. Your stomach also secretes gastric lipase. Lipase break down lipids.
  4. Lastly your stomach is coated with a thick layer of mucus and the role of the mucus is to protect the stomach lining from the very acidic contents of the stomach.


The stomach.

4. The pancreas

– Your pancreas releases a number of different hormones, including releases bicarbonate. And the role of bicarbonate is to help neutralize the intestinal contents from the stomach’s acidic environment.

– Your pancreas also produces enzymes that digest carbohydrate, protein, and fat.

5. The gallbladder

– Your gallbladder is an ancillary organ to digestion that stores bile. Bile is important in helping you to digest and absorb fat.

6. The Small intestine


Small Intestine
Villi and Microvilli

– Your small intestine is about 20 feet in length. The folds contain fingerlike projections called villi and microvilli. The villi absorb the nutrients into the system and the microvilli act as part of the brush border to help absorb the circulating nutrients. And this represents the very, very large Absorptive capacity of your small intestine.

– Your small intestine is responsible for absorbing nutrients into the blood or the lymph, and this is where most nutrient digestion occurs.

– The undigested substances pass from your small intestine to the large intestine through a sphincter. Here’s what your small intestine looks like. It’s comprised of three primary parts. The duodenum, the jejunum. And the illium. It’s important to know which minerals and vitamins are absorbed where in the small intestine.

– The duodenum is the first part of the small intestine. This is where the minerals calcium, phosphorus, magnesium, iron, and copper are absorbed. The vitamins thiamin, riboflavin, niacin, biotin, folate, and the fat soluble vitamins are also absorbed here.

– In the jejunum, the same minerals and vitamins are also absorbed but less. We’ve also got lipids, the very small monosaccharide carbohydrates, and some of the smaller amino acids and small protein molecules.

– In your ileum, which is the final part of the small intestine, this is where the mineral magnesium is absorbed and the vitamins vitamin C, vitamin B12, vitamin D, K, and folate.

7. The Large Intestine

– Your large intestine is what we also call your colon. The colon isn’t just a static tube; it contracts like an earthworm to force the residue along. And in length, it’s about five feet.

– In your large intestine is where water is absorbed, and this is where some vitamins and minerals are absorbed. Your large intestine is home to bacteria. These are the intestinal bacteria that help ferment some of the fibers that you eat.

– Those on high fibre ‘traditional food’ diets take only around 12 hours to digest food waste in the colon. In the western world, the food waste may stay in the colon as long as two weeks. The answer? Processed food.

– Water, some vitamins and minerals are absorbed here. The colon has intestinal microflora. So the good bacteria break down fiber, but they also synthesize a number of nutrients.

– You actually have bacteria in your gut that can make certain vitamins, from the corn the contents of what’s left of the digestive process pass onto the rectum where they are stored until they are excrete via the anus.

Large Intestine


Changes in our biochemistry

When stressed, we change the biochemistry of our blood. Starts with perception of threat, triggers adrenal glands which releases adrenaline and cortosol (stress soup) which turn on enzymes, turning the fat cell into a fat storing machine. Alerts brain to find those fattening sweet foods. Cortosol is one of the strongest drives it can feel the need to have a drug. Depending on the cortisol, we either are in fat burning mode or bat gaining mode. Our chronic stressful situation causes us to eat more.

We eat more when we are stressed or bored. If you were to meditate right before a meal, becoming aware of your surroundings, feelings and peaceful. Just smell it and embrace the moment. This will allow you to balance your mind, your caloric intake and your mindfulness of eating.

Exercise allows us more opioides, which allows us to feel pleasure. On the other hand, high fat and sugar products stimulate the release of opioids. Exercise causes you to stop craving food for pleasure, substituting it for food. Exercise keeps the fatty acids in the blood down, which supports to make the heart electrically unstable.If we overeat, our fat cells blow up like balloons to hold up more and more fat. The fat cells were also created a hormone known as Leptin. The thin people are generating a lot of Leptin and the people that cannot control their eating had no Leptin.

Leptin travels up to the hypothamalus. It acts like a temperature indicator for hunger. Fat people have their thermostat set higher. It is easier to get fat than it is to get thin. It is a massive struggle that is a day to day fight. If we have more leptin, we eat less. When we have less leptin, we eat. They are currently working on creating a pill. There are a number of chemicals and parts of the hyperthalamus that control the hunger suppression, amongst other things. At the moment, there is no pill of medical solution for obesity.

Cholesterol is produced naturally by the liver from thereon it gets released in the blood and passed onto the body to help make healthy cells. Our blood has good and bad cholesterol. If saturated fats, it is the bad cholesterol sticks to the walls of the arteries of the brain or heart which can lead to blockage ending up with heart attack or stroke.

Carbs are packed full of molecules the body can turn into energy when exercising strenuously. The others eat fat based protein, which is harder to use when doing strenuous exercise. Which is better? The twins do 18 miles of bicycling and then a 3-mile log race. Carbs are destined for exercise. If you don’t do exercise, there is no point to have a high carb diet.

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