Importance of Absorption
The absorption process is the mechanism by which the final digestive products enter the blood or lymph through the intestinal mucosa. In the small intestine, digested molecules of food are absorbed. This means they go into our bloodstream through the membrane of the small intestine. From there, the molecules of the digested food are carried around the body to the necessary location for nourishment. Absorption of food takes place mostly in the small intestine.
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Absorption across a surface happens rapidly and easily if:
The surface is thin
It has a large area
The internal wall of the small intestines is designed to allow for the easy and efficient crossing of substances:
It has a thin wall, just a dense cell
There's a lot of small villi to give a larger surface area
With a thick wall and a small surface, the small intestine may hold a large quantity of digested food before it is absorbed. The villi (singular: villus) stands out and gives a larger surface area for absorption. They also contain blood capillaries for absorbing the molecules of food that are ingested.
Egestion
In the large intestine, excess water is absorbed from the food. What remains is the faecal matter. The faecal matter is stored in the rectum, which is the ending of the large intestine, and it continues to store there till the matter could be ejected out. It then emerges from the rectum in the form of faeces from the anus. This is known as egestion. Make sure that egestion is not confused with excretion. Egestion is the ejection of undigested food, while excretion is the discharge of metabolic waste material.
The digestive system contains several bacteria and bacteria constitute about half the dry weight of the faeces. Bacteria are important in the digestive system. The constituents of the faeces are:
Some forms of nutrients, like certain carbohydrates that people can not digest.
Dead bacteria.
The transport mechanisms on the apical surface of enterocytes (the absorptive cells of the intestine) absorb most nutrients. Lipid, fat-soluble vitamins and most water-soluble vitamins are exceptions. The dietary fats are emulsified by bile salts and lecithin to form micelles that may bring fatty particles to the enterozyte's surface. The micelles release their fats throughout the membrane of the cell. Fats are then processed into chylomicrons, which are converted into lactates, into triglycerides and combined with other lipids and proteins. Other absorbed monomers move from the villus to the hepatic portal vein from blood capillaries to and from the liver.
What is Meant by Digestion?
Digestion is how your body turns food into nutrients that are used to repair cells, energy and facilitate growth. The food pipe connecting your mouth and stomach, the stomach and the anus together form the digestive tract (or gastrointestinal tract). It consists of a variety of muscles that coordinate food movement and other cells that contain enzymes and hormones. Three other organs, that is, the liver, gallbladder and pancreas, are needed for digestion.
Mechanisms of Absorption
Simple diffusion.
Active transport
Facilitated transport.
Passive transport.
Simple Diffusion
Simple diffusion refers to movement through the membrane of the solution from the higher level to the lower level. Some monosaccharides, based on the concentration gradient, diffuse into the blood after digesting. E.g., Glucose, amino acids and chloride ions.
Active Transport
The process of solute movement from lower concentrations to higher concentrations at the cost of energy can be described as active transport. During successful blood flow, electrolytes such as Na (sodium) ions are absorbed.
Facilitated Transport
The process of the movement of solutes across the biological membrane using specific carrier proteins is defined as facilitated transport. This method absorbs certain digested amino acids and glucose into the blood.
Passive Transport
Passive transportation is characterized as the solvent movement process across a cell membrane without the expenditure of energy. After digestion, passive transportation absorbs a simpler food substance into the blood.
The blood can not absorb certain digested products from fats. E.g., Glycerol and fatty acids. These components attach to small droplets and form the micelle complex. The component complexes of this micelle are transformed into chylomicrons. Chylomicrons are fat globules covered with small proteins. The chylomicrons are then moved into the lymph vessels and released into the blood. Eventually, the substance that is digested and ingested enters the fabric to be used. This is how the absorption and assimilation of digested food are done.
FAQs on Absorption of Digested Foods
1. What is meant by the absorption of digested food?
Absorption is the process where the simple, soluble nutrients from digested food pass from the digestive tract into the blood and lymph. This allows the body to transport these essential substances, like glucose, amino acids, and fatty acids, to all the cells for energy, growth, and repair.
2. Where does most of the absorption of digested food take place in the human body?
The vast majority of nutrient absorption, around 95%, occurs in the small intestine. Its long length and inner lining covered with tiny, finger-like projections called villi and microvilli create a massive surface area, making it perfectly suited for this function.
3. What are the different mechanisms by which nutrients are absorbed?
Nutrients are absorbed through several mechanisms, depending on the substance:
- Simple Diffusion: Movement from a high to a low concentration area. Small amounts of monosaccharides like glucose use this method.
- Facilitated Diffusion: Nutrients move with the help of a carrier protein, but still down a concentration gradient. Fructose is an example.
- Active Transport: This method uses energy (ATP) to move nutrients against a concentration gradient. It is used for absorbing glucose, amino acids, and minerals.
- Osmosis: The movement of water across a semipermeable membrane to balance concentrations.
4. Why is the process of absorbing digested food necessary for our survival?
The absorption of digested food is absolutely vital because digestion itself only breaks down food into smaller molecules. Without absorption, these valuable nutrients would simply pass through our body and be excreted. Absorption is the critical step that transfers these nutrients into our internal environment, providing the fuel and building blocks that every single cell needs to function, grow, and repair itself.
5. How is the small intestine's structure adapted for efficient absorption?
The small intestine is specially designed for maximum absorption. Firstly, it is very long, providing more time and surface area. Secondly, its inner wall has folds and is covered with millions of tiny, finger-like projections called villi. These villi are further covered by even smaller projections called microvilli. Together, these features increase the surface area for absorption enormously, making the process highly efficient.
6. What is the main difference between absorption in the small and large intestines?
The main difference lies in what is absorbed. The small intestine is where the majority of all nutrients are absorbed, including carbohydrates, proteins, fats, and most vitamins. The large intestine, on the other hand, primarily absorbs water, some minerals, and certain drugs. It also absorbs vitamins created by gut bacteria, like Vitamin K.
7. How is the absorption of fats different from that of proteins and carbohydrates?
The absorption of fats is unique. While carbohydrates (as glucose) and proteins (as amino acids) are absorbed directly into the bloodstream, fats take a different path. Fats are first broken down into fatty acids and glycerol, which form small droplets called micelles. These are absorbed into the intestinal cells, re-formed into fats, and coated with protein to create chylomicrons. These are then absorbed into the lymph vessels, not directly into the blood.
8. What happens to the nutrients after they are absorbed into the blood or lymph?
Once absorbed, nutrients in the bloodstream are transported directly to the liver. The liver processes, stores, or releases them for the rest of the body. Fats absorbed into the lymphatic system bypass the liver at first and are slowly released into the bloodstream later. The process of cells using these absorbed nutrients for energy and growth is called assimilation.
