Re: If a human doesn't have a large intestine, how does he get the minerals?

Greetings,
 
This is a very good question, I found an abundant amount of information on
the website of the  National Institute of Diabetes and Digestive and 
Kidney Diseases, National Institutes of Health.
The information below should adequately answer any question you have 
related to the digestive process.
 http://www.nutristrategy.
com/digestion.htm

Absorption and Transport of Nutrients
Digested molecules of food, water and minerals from the diet, are absorbed 
from the cavity of the upper small intestine. The absorbed materials cross 
the mucosa into the blood, and are carried off in the bloodstream to other 
parts of the body for storage or further chemical change. This process 
varies with different types of nutrients.
Carbohydrates: An average American adult eats about half a pound of 
carbohydrate each day. Some of our most common foods contain mostly 
carbohydrates. Examples are bread, potatoes, pastries, candy, rice, 
spaghetti, fruits, and vegetables. Many of these foods contain both 
starch, which can be digested, and fiber, which the body cannot digest.
The digestible carbohydrates are broken into simpler molecules by enzymes 
in the saliva, in juice produced by the pancreas, and in the lining of the 
small intestine. Starch is digested in two steps: First, an enzyme in the 
saliva and pancreatic juice breaks the starch into molecules called 
maltose; then an enzyme in the lining of the small intestine (maltase) 
splits the maltose into glucose molecules that can be absorbed into the 
blood. Glucose is carried through the bloodstream to the liver, where it 
is stored or used to provide energy for the work of the body.
Table sugar is another carbohydrate that must be digested to be useful. An 
enzyme in the lining of the small intestine digests table sugar into 
glucose and fructose, each of which can be absorbed from the intestinal 
cavity into the blood. Milk contains yet another type of sugar, lactose, 
which is changed into absorbable molecules by an enzyme called lactase, 
also found in the intestinal lining.
Protein: Foods such as meat, eggs, and beans consist of large molecules of 
protein that must be digested by enzymes before they can be used to build 
and repair body tissues. An enzyme in the juice of the stomach starts the 
digestion of swallowed protein. Further digestion of the protein is 
completed in the small intestine. Here, several enzymes from the 
pancreatic juice and the lining of the intestine carry out the breakdown 
of huge protein molecules into small molecules called amino acids. These 
small molecules can be absorbed from the hollow of the small intestine 
into the blood and then be carried to all parts of the body to build the 
walls and other parts of cells.
Fats: Fat molecules are a rich source of energy for the body. The first 
step in digestion of a fat is to dissolve it into the watery content of 
the intestinal cavity. The bile acids produced by the liver act as natural 
detergents to dissolve fat in water and allow the enzymes to break the 
large fat molecules into smaller molecules, some of which are fatty acids 
and cholesterol. The bile acids combine with the fatty acids and 
cholesterol and help these molecules to move into the cells of the mucosa. 
In these cells the small molecules are formed back into large molecules, 
most of which pass into vessels (called lymphatics) near the intestine. 
These small vessels carry the reformed fat to the veins of the chest, and 
the blood carries the fat to storage depots in different parts of the body.
Vitamins: Another important part of our food that is absorbed from the 
small intestine is the class of chemicals we call vitamins. There are two 
different types of vitamins, classified by the fluid in which they can be 
dissolved: water -soluble vitamins (all the B vitamins and vitamin C) and 
fat-soluble vitamins (vitamins A, D, and K).
Water and Salt: Most of the material absorbed from the cavity of the small 
intestine is water in which salt is dissolved. The salt and water come 
from the food and liquid we swallow and the juices secreted by the many 
digestive glands. In a healthy adult, more than a gallon of water 
containing over an ounce of salt is absorbed from the intestine every 24 
hours.

 


Why Is Digestion Important?
When we eat such things as bread, meat, and vegetables, they are not in a 
form that the body can use as nourishment. Our food and drink must be 
changed into smaller molecules of nutrients before they can be absorbed 
into the blood and carried to cells throughout the body. Digestion is the 
process by which food and drink are broken down into their smallest parts 
so that the body can use them to build and nourish cells and to provide 
energy. 
The digestive system is a series of hollow organs joined in a long, 
twisting tube from the mouth to the anus. Inside this tube is a lining 
called the mucosa. In the mouth, stomach, and small intestine, the mucosa 
contains tiny glands that produce juices to help digest food. 
There are also two solid digestive organs, the liver and the pancreas, 
which produce juices that reach the intestine through small tubes. In 
addition, parts of other organ systems (for instance, nerves and blood) 
play a major role in the digestive system.

 


How Is Food Digested?
Digestion involves the mixing of food, its movement through the digestive 
tract, and chemical breakdown of the large molecules of food into smaller 
molecules. Digestion begins in the mouth, when we chew and swallow, and is 
completed in the small intestine. The chemical process varies somewhat for 
different kinds of food.
Movement of Food Through the System
• Mouth: Seconds 
• Esophagus: Seconds 
• Stomach: Up to 3 ½ hours 
• Small Intestine: Minutes 
• Large Intestine: Hours
The large, hollow organs of the digestive system contain muscle that 
enables their walls to move. The movement of organ walls can propel food 
and liquid and also can mix the contents within each organ. Typical 
movement of the esophagus, stomach, and intestine is called peristalsis. 
The action of peristalsis looks like an ocean wave moving through the 
muscle. The muscle of the organ produces a narrowing and then propels the 
narrowed portion slowly down the length of the organ. These waves of 
narrowing push the food and fluid in front of them through each hollow 
organ.
The first major muscle movement occurs when food or liquid is swallowed. 
Although we are able to start swallowing by choice, once the swallow 
begins, it becomes involuntary and proceeds under the control of the 
nerves.
The esophagus is the organ into which the swallowed food is pushed. It 
connects the throat above with the stomach below. At the junction of the 
esophagus and stomach, there is a ringlike valve closing the passage 
between the two organs. However, as the food approaches the closed ring, 
the surrounding muscles relax and allow the food to pass.
The food then enters the stomach, which has three mechanical tasks to do. 
First, the stomach must store the swallowed food and liquid. This requires 
the muscle of the upper part of the stomach to relax and accept large 
volumes of swallowed material. The second job is to mix up the food, 
liquid, and digestive juice produced by the stomach. The lower part of the 
stomach mixes these materials by its muscle action. The third task of the 
stomach is to empty its contents slowly into the small intestine.
Several factors affect emptying of the stomach, including the nature of 
the food (mainly its fat and protein content) and the degree of muscle 
action of the emptying stomach and the next organ to receive the stomach 
contents (the small intestine). As the food is digested in the small 
intestine and dissolved into the juices from the pancreas, liver, and 
intestine, the contents of the intestine are mixed and pushed forward to 
allow further digestion.
Finally, all of the digested nutrients are absorbed through the intestinal 
walls. The waste products of this process include undigested parts of the 
food, known as fiber, and older cells that have been shed from the mucosa. 
These materials are propelled into the colon, where they remain, usually 
for a day or two, until the feces are expelled by a bowel movement.

 


Production of Digestive Juices
Glands of the digestive system are crucial to the process of digestion. 
They produce both the juices that break down the food and the hormones 
that help to control the process.
The glands that act first are in the mouth--the salivary glands. Saliva 
produced by these glands contains an enzyme that begins to digest the 
starch from food into smaller molecules.
The next set of digestive glands is in the stomach lining. They produce 
stomach acid and an enzyme that digests protein. One of the unsolved 
puzzles of the digestive system is why the acid juice of the stomach does 
not dissolve the tissue of the stomach itself. In most people, the stomach 
mucosa is able to resist the juice, although food and other tissues of the 
body cannot.
After the stomach empties the food and its juice into the small intestine, 
the juices of two other digestive organs mix with the food to continue the 
process of digestion. One of these organs is the pancreas. It produces a 
juice that contains a wide array of enzymes to break down the 
carbohydrates, fat, and protein in our food. Other enzymes that are active 
in the process come from glands in the wall of the intestine or even a 
part of that wall.
The liver produces yet another digestive juice--bile. The bile is stored 
between meals in the gallbladder. At mealtime, it is squeezed out of the 
gallbladder into the bile ducts to reach the intestine and mix with the 
fat in our food. The bile acids dissolve the fat into the watery contents 
of the intestine, much like detergents that dissolve grease from a frying 
pan. After the fat is dissolved, it is digested by enzymes from the 
pancreas and the lining of the intestine.

 


How Is the Digestive Process Controlled?
Hormone Regulators
A fascinating feature of the digestive system is that it contains its own 
regulators. The major hormones that control the functions of the digestive 
system are produced and released by cells in the mucosa of the stomach and 
small intestine. These hormones are released into the blood of the 
digestive tract, travel back to the heart and through the arteries, and 
return to the digestive system, where they stimulate digestive juices and 
cause organ movement. The hormones that control digestion are gastrin, 
secretin, and cholecystokinin (CCK):
• Gastrin causes the stomach to produce an acid for dissolving and 
digesting some foods. It is also necessary for the normal growth of the 
lining of the stomach, small intestine, and colon.
• Secretin causes the pancreas to send out a digestive juice that is rich 
in bicarbonate. It stimulates the stomach to produce pepsin, an enzyme 
that digests protein, and it also stimulates the liver to produce bile.
• CCK causes the pancreas to grow and to produce the enzymes of pancreatic 
juice, and it causes the gallbladder to empty. 
Nerve Regulators
Two types of nerves help to control the action of the digestive system. 
Extrinsic (outside) nerves come to the digestive organs from the 
unconscious part of the brain or from the spinal cord. They release a 
chemical called acetylcholine and another called adrenaline. Acetylcholine 
causes the muscle of the digestive organs to squeeze with more force and 
increase the "push" of food and juice through the digestive tract. 
Acetylcholine also causes the stomach and pancreas to produce more 
digestive juice. Adrenaline relaxes the muscle of the stomach and 
intestine and decreases the flow of blood to these organs.
Even more important, though, are the intrinsic (inside) nerves, which make 
up a very dense network embedded in the walls of the esophagus, stomach, 
small intestine, and colon. The intrinsic nerves are triggered to act when 
the walls of the hollow organs are stretched by food. They release many 
different substances that speed up or delay the movement of food and the 
production of juices by the digestive organs.
Source: National Institute of Diabetes and Digestive and Kidney Diseases, 
National Institutes of Health.


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June Wingert
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