Which Process Is Used By Animals To Remove Ingested Foods That Cannot Be Digested?

Chapter 15. Animal Diet and the Digestive System

15.1 Digestive Systems

Learning Objectives

By the end of this section, y'all will be able to:

• Explain the processes of digestion and absorption
• Compare and contrast different types of digestive systems
• Explain the specialized functions of the organs involved in processing food in the body
• Depict the ways in which organs work together to digest food and absorb nutrients

Animals obtain their diet from the consumption of other organisms. Depending on their diet, animals can be classified into the post-obit categories: plant eaters (herbivores), meat eaters (carnivores), and those that eat both plants and animals (omnivores). The nutrients and macromolecules present in nutrient are not immediately accessible to the cells. There are a number of processes that modify food within the animal body in society to make the nutrients and organic molecules accessible for cellular function. As animals evolved in complexity of form and office, their digestive systems take also evolved to accommodate their diverse dietary needs.

Herbivores, Omnivores, and Carnivores

Herbivores are animals whose primary nutrient source is plant-based. Examples of herbivores, equally shown in Figure 15.2 include vertebrates like deer, koalas, and some bird species, besides as invertebrates such as crickets and caterpillars. These animals have evolved digestive systems capable of handling big amounts of institute cloth. Herbivores tin can be further classified into frugivores (fruit-eaters), granivores (seed eaters), nectivores (nectar feeders), and folivores (leaf eaters).

Figure xv.two.  Herbivores, similar this (a) mule deer and (b) monarch caterpillar, eat primarily plant material. (credit a: modification of work past Pecker Ebbesen; credit b: modification of work by Doug Bowman)

Carnivores are animals that consume other animals. The word carnivore is derived from Latin and literally means "meat eater." Wild cats such as lions, shown in Figure 35.three a and tigers are examples of vertebrate carnivores, every bit are snakes and sharks, while invertebrate carnivores include sea stars, spiders, and ladybugs, shown in Figure 15.3 b . Obligate carnivores are those that rely entirely on animal mankind to obtain their nutrients; examples of obligate carnivores are members of the cat family, such as lions and cheetahs. Facultative carnivores are those that as well eat non-creature nutrient in improver to beast nutrient. Note that in that location is no clear line that differentiates facultative carnivores from omnivores; dogs would exist considered facultative carnivores.

Figure 15.3.  Carnivores similar the (a) lion swallow primarily meat. The (b) ladybug is besides a carnivore that consumes small insects called aphids. (credit a: modification of work by Kevin Pluck; credit b: modification of work by Jon Sullivan)

Omnivores are animals that consume both plant- and animal-derived food. In Latin, omnivore ways to swallow everything. Humans, bears (shown in Effigy 15.iv a ), and chickens are example of vertebrate omnivores; invertebrate omnivores include cockroaches and crayfish (shown in Figure 15.iv b ).

Figure 15.4.  Omnivores like the (a) bear and (b) crayfish eat both plant and creature based nutrient. (credit a: modification of work by Dave Menke; credit b: modification of piece of work by Jon Sullivan)

Invertebrate Digestive Systems

Animals accept evolved different types of digestive systems to aid in the digestion of the different foods they eat. The simplest instance is that of a gastrovascular cavity and is found in organisms with merely one opening for digestion. Platyhelminthes (flatworms), Ctenophora (comb jellies), and Cnidaria (coral, jelly fish, and sea anemones) use this type of digestion. Gastrovascular cavities, as shown in Figure 15.5 a , are typically a blind tube or crenel with just one opening, the "oral cavity", which likewise serves every bit an "anus". Ingested material enters the oral cavity and passes through a hollow, tubular cavity. Cells within the cavity secrete digestive enzymes that interruption down the food. The food particles are engulfed by the cells lining the gastrovascular cavity.

The alimentary canal, shown in Figure fifteen.5 b , is a more than advanced system: it consists of one tube with a oral cavity at one finish and an anus at the other. Earthworms are an example of an animate being with an comestible culvert. Once the nutrient is ingested through the rima oris, it passes through the esophagus and is stored in an organ called the crop; then it passes into the gizzard where it is churned and digested. From the gizzard, the food passes through the intestine, the nutrients are absorbed, and the waste matter is eliminated every bit feces, chosen castings, through the anus.

Figure 15.v.  (a) A gastrovascular crenel has a single opening through which food is ingested and waste is excreted, as shown in this hydra and in this jellyfish medusa. (b) An alimentary canal has two openings: a rima oris for ingesting food, and an anus for eliminating waste, equally shown in this nematode.

Vertebrate Digestive Systems

Vertebrates accept evolved more complex digestive systems to conform to their dietary needs. Some animals accept a single stomach, while others take multi-chambered stomachs. Birds have developed a digestive organization adapted to eating unmasticated food.

Monogastric: Unmarried-chambered Tum

Equally the word monogastric suggests, this blazon of digestive system consists of 1 ("mono") breadbasket chamber ("gastric"). Humans and many animals accept a monogastric digestive system as illustrated in Figure 15.half-dozen ab . The procedure of digestion begins with the mouth and the intake of food. The teeth play an important office in masticating (chewing) or physically breaking downward food into smaller particles. The enzymes present in saliva also begin to chemically break down food. The esophagus is a long tube that connects the mouth to the stomach. Using peristalsis, or moving ridge-like smooth muscle contractions, the muscles of the esophagus button the food towards the stomach. In order to speed upwardly the actions of enzymes in the breadbasket, the stomach is an extremely acidic surround, with a pH betwixt 1.5 and 2.5. The gastric juices, which include enzymes in the stomach, deed on the food particles and continue the procedure of digestion. Further breakup of nutrient takes place in the small intestine where enzymes produced by the liver, the small intestine, and the pancreas go on the procedure of digestion. The nutrients are absorbed into the blood stream across the epithelial cells lining the walls of the small intestines. The waste material travels on to the large intestine where water is captivated and the drier waste product material is compacted into feces; it is stored until it is excreted through the rectum.

Figure 15.6.
(a) Humans and herbivores, such as the (b) rabbit, have a monogastric digestive system. Even so, in the rabbit the small intestine and cecum are enlarged to allow more time to digest plant cloth. The enlarged organ provides more surface expanse for absorption of nutrients. Rabbits digest their nutrient twice: the first time food passes through the digestive organisation, it collects in the cecum, and and then it passes equally soft feces called cecotrophes. The rabbit re-ingests these cecotrophes to further assimilate them.

Avian

Birds confront special challenges when it comes to obtaining nutrition from food. They do not have teeth and so their digestive system, shown in Effigy 15.vii, must be able to procedure united nations-masticated nutrient. Birds have evolved a variety of beak types that reflect the vast variety in their nutrition, ranging from seeds and insects to fruits and nuts. Because near birds fly, their metabolic rates are high in society to efficiently procedure food and proceed their body weight depression. The stomach of birds has two chambers: the proventriculus, where gastric juices are produced to digest the nutrient before information technology enters the stomach, and the gizzard, where the food is stored, soaked, and mechanically ground. The undigested material forms food pellets that are sometimes regurgitated. Most of the chemical digestion and absorption happens in the intestine and the waste product is excreted through the cloaca.

Figure 15.vii.  The avian esophagus has a pouch, called a crop, which stores food. Nutrient passes from the crop to the first of ii stomachs, chosen the proventriculus, which contains digestive juices that suspension downwardly food. From the proventriculus, the food enters the second breadbasket, chosen the gizzard, which grinds nutrient. Some birds swallow stones or grit, which are stored in the gizzard, to assist the grinding process. Birds do not have separate openings to excrete urine and feces. Instead, uric acrid from the kidneys is secreted into the big intestine and combined with waste from the digestive process. This waste is excreted through an opening chosen the cloaca.

Parts of the Digestive System

The vertebrate digestive arrangement is designed to facilitate the transformation of food thing into the nutrient components that sustain organisms.

Oral Cavity

The oral cavity, or rima oris, is the betoken of entry of food into the digestive system, illustrated in Figure 15.ix. The food consumed is broken into smaller particles by mastication, the chewing action of the teeth. All mammals have teeth and tin chew their nutrient.

The extensive chemical process of digestion begins in the oral cavity. As food is being chewed, saliva, produced past the salivary glands, mixes with the food. Saliva is a watery substance produced in the mouths of many animals. There are three major glands that secrete saliva—the parotid, the submandibular, and the sublingual. Saliva contains mucus that moistens nutrient and buffers the pH of the nutrient. Saliva also contains immunoglobulins and lysozymes, which have antibacterial action to reduce molar disuse by inhibiting growth of some bacteria. Saliva besides contains an enzyme called salivary amylase that begins the process of converting starches in the food into a disaccharide chosen maltose. Some other enzyme called lipase is produced by the cells in the tongue. Lipases are a course of enzymes that can pause downward triglycerides. The lingual lipase begins the breakdown of fatty components in the nutrient. The chewing and wetting action provided by the teeth and saliva set up the food into a mass called the bolus for swallowing. The tongue helps in swallowing—moving the bolus from the mouth into the pharynx. The pharynx opens to two passageways: the trachea, which leads to the lungs, and the esophagus, which leads to the tummy. The trachea has an opening called the glottis, which is covered by a cartilaginous flap called the epiglottis. When swallowing, the epiglottis closes the glottis and food passes into the esophagus and not the trachea. This arrangement allows food to be kept out of the trachea.

Figure 15.9.
Digestion of food begins in the (a) oral cavity. Food is masticated by teeth and moistened past saliva secreted from the (b) salivary glands. Enzymes in the saliva brainstorm to digest starches and fats. With the help of the tongue, the resulting bolus is moved into the esophagus by swallowing. (credit: modification of piece of work past the National Cancer Constitute)

Esophagus

The esophagus is a tubular organ that connects the oral cavity to the stomach. The chewed and softened food passes through the esophagus later being swallowed. The smooth muscles of the esophagus undergo a series of wave similar movements called peristalsis that push the nutrient toward the stomach, equally illustrated in Effigy 15.ten. The peristalsis wave is unidirectional—it moves food from the mouth to the stomach, and reverse movement is not possible. The peristaltic motion of the esophagus is an involuntary reflex; it takes place in response to the human action of swallowing.

Figure fifteen.x.  The esophagus transfers nutrient from the mouth to the stomach through peristaltic movements.

A ring-like muscle called a sphincter forms valves in the digestive system. The gastro-esophageal sphincter is located at the tum end of the esophagus. In response to swallowing and the force per unit area exerted by the bolus of food, this sphincter opens, and the bolus enters the stomach. When in that location is no swallowing action, this sphincter is shut and prevents the contents of the stomach from traveling up the esophagus. Many animals take a true sphincter; however, in humans, there is no true sphincter, but the esophagus remains closed when there is no swallowing action. Acid reflux or "heartburn" occurs when the acidic digestive juices escape into the esophagus.

Stomach

A large function of digestion occurs in the breadbasket, shown in Figure xv.11. The stomach is a saclike organ that secretes gastric digestive juices. The pH in the tummy is between 1.5 and two.5. This highly acidic environment is required for the chemical breakdown of food and the extraction of nutrients. When empty, the stomach is a rather minor organ; however, it can aggrandize to upwards to 20 times its resting size when filled with nutrient. This feature is particularly useful for animals that need to eat when food is available.

Effigy xv.11.  The human stomach has an extremely acidic environment where most of the poly peptide gets digested. (credit: modification of work by Mariana Ruiz Villareal)

Which of the following statements about the digestive system is imitation?

1. Chyme is a mixture of nutrient and digestive juices that is produced in the stomach.
2. Food enters the large intestine before the small intestine.
3. In the small intestine, chyme mixes with bile, which emulsifies fats.
4. The stomach is separated from the small-scale intestine past the pyloric sphincter.

The stomach is as well the major site for protein digestion in animals other than ruminants. Protein digestion is mediated by an enzyme called pepsin in the tum chamber. Pepsin is secreted past the chief cells in the stomach in an inactive grade called pepsinogen. Pepsin breaks peptide bonds and cleaves proteins into smaller polypeptides; it likewise helps activate more pepsinogen, starting a positive feedback mechanism that generates more pepsin. Some other cell blazon—parietal cells—secrete hydrogen and chloride ions, which combine in the lumen to grade hydrochloric acid, the main acidic component of the tummy juices. Hydrochloric acid helps to convert the inactive pepsinogen to pepsin. The highly acidic environment likewise kills many microorganisms in the food and, combined with the action of the enzyme pepsin, results in the hydrolysis of poly peptide in the nutrient. Chemical digestion is facilitated by the churning action of the stomach. Contraction and relaxation of smooth muscles mixes the stomach contents about every 20 minutes. The partially digested food and gastric juice mixture is chosen chyme. Chyme passes from the tum to the pocket-size intestine. Further protein digestion takes identify in the small intestine. Gastric elimination occurs within two to six hours after a repast. But a small amount of chyme is released into the small intestine at a fourth dimension. The movement of chyme from the stomach into the small intestine is regulated by the pyloric sphincter.

When digesting protein and some fats, the tum lining must exist protected from getting digested past pepsin. In that location are two points to consider when describing how the breadbasket lining is protected. First, as previously mentioned, the enzyme pepsin is synthesized in the inactive form. This protects the chief cells, because pepsinogen does not have the same enzyme functionality of pepsin. 2nd, the stomach has a thick mucus lining that protects the underlying tissue from the action of the digestive juices. When this mucus lining is ruptured, ulcers tin can form in the stomach. Ulcers are open up wounds in or on an organ caused by bacteria (Helicobacter pylori) when the mucus lining is ruptured and fails to reform.

Pocket-sized Intestine

Chyme moves from the stomach to the small-scale intestine. The small intestine is the organ where the digestion of protein, fats, and carbohydrates is completed. The modest intestine is a long tube-like organ with a highly folded surface containing finger-like projections chosen the villi. The apical surface of each villus has many microscopic projections called microvilli. These structures, illustrated in Figure 15.12, are lined with epithelial cells on the luminal side and allow for the nutrients to be absorbed from the digested food and absorbed into the claret stream on the other side. The villi and microvilli, with their many folds, increment the surface surface area of the intestine and increment assimilation efficiency of the nutrients. Captivated nutrients in the blood are carried into the hepatic portal vein, which leads to the liver. There, the liver regulates the distribution of nutrients to the rest of the body and removes toxic substances, including drugs, alcohol, and some pathogens.

Effigy 15.12.  Villi are folds on the modest intestine lining that increase the surface surface area to facilitate the absorption of nutrients.

Which of the following statements virtually the small intestine is false?

1. Absorbent cells that line the small intestine have microvilli, minor projections that increase surface area and aid in the absorption of food.
2. The inside of the small intestine has many folds, called villi.
3. Microvilli are lined with blood vessels likewise as lymphatic vessels.
4. The inside of the small intestine is called the lumen.

The human small intestine is over 6m long and is divided into three parts: the duodenum, the jejunum, and the ileum. The "C-shaped," stock-still part of the small intestine is called the duodenum and is shown in Figure 15.xi. The duodenum is separated from the breadbasket past the pyloric sphincter which opens to allow chyme to move from the stomach to the duodenum. In the duodenum, chyme is mixed with pancreatic juices in an alkaline solution rich in bicarbonate that neutralizes the acidity of chyme and acts as a buffer. Pancreatic juices besides incorporate several digestive enzymes. Digestive juices from the pancreas, liver, and gallbladder, equally well as from gland cells of the intestinal wall itself, enter the duodenum. Bile is produced in the liver and stored and concentrated in the gallbladder. Bile contains bile salts which emulsify lipids while the pancreas produces enzymes that catabolize starches, disaccharides, proteins, and fats. These digestive juices break down the nutrient particles in the chyme into glucose, triglycerides, and amino acids. Some chemical digestion of nutrient takes place in the duodenum. Absorption of fat acids also takes identify in the duodenum.

The second part of the pocket-sized intestine is chosen the jejunum, shown in Figure 15.11. Here, hydrolysis of nutrients is connected while well-nigh of the carbohydrates and amino acids are absorbed through the intestinal lining. The bulk of chemic digestion and food absorption occurs in the jejunum.

The ileum, besides illustrated in Figure xv.11 is the final part of the small intestine and here the bile salts and vitamins are absorbed into blood stream. The undigested food is sent to the colon from the ileum via peristaltic movements of the muscle. The ileum ends and the large intestine begins at the ileocecal valve. The vermiform, "worm-like," appendix is located at the ileocecal valve. The appendix of humans secretes no enzymes and has an insignificant role in immunity.

Large Intestine

The large intestine, illustrated in Effigy fifteen.13, reabsorbs the h2o from the undigested food cloth and processes the waste fabric. The human large intestine is much smaller in length compared to the minor intestine but larger in diameter. It has three parts: the cecum, the colon, and the rectum. The cecum joins the ileum to the colon and is the receiving pouch for the waste matter. The colon is home to many bacteria or "intestinal flora" that help in the digestive processes. The colon can be divided into iv regions, the ascending colon, the transverse colon, the descending colon and the sigmoid colon. The main functions of the colon are to extract the water and mineral salts from undigested food, and to shop waste material. Carnivorous mammals have a shorter large intestine compared to herbivorous mammals due to their diet.

Rectum and Anus

The rectum is the terminal stop of the large intestine, as shown in Figure 15.xiii. The master function of the rectum is to store the feces until defecation. The feces are propelled using peristaltic movements during elimination. The anus is an opening at the far-cease of the digestive tract and is the go out point for the waste material. 2 sphincters betwixt the rectum and anus control emptying: the inner sphincter is involuntary and the outer sphincter is voluntary.

Accessory Organs

The organs discussed in a higher place are the organs of the digestive tract through which food passes. Accessory organs are organs that add secretions (enzymes) that catabolize food into nutrients. Accessory organs include salivary glands, the liver, the pancreas, and the gallbladder. The liver, pancreas, and gallbladder are regulated by hormones in response to the food consumed.

The liver is the largest internal organ in humans and it plays a very important part in digestion of fats and detoxifying blood. The liver produces bile, a digestive juice that is required for the breakdown of fatty components of the nutrient in the duodenum. The liver too processes the vitamins and fats and synthesizes many plasma proteins.

The pancreas is another important gland that secretes digestive juices. The chyme produced from the stomach is highly acidic in nature; the pancreatic juices comprise high levels of bicarbonate, an brine that neutralizes the acidic chyme. Additionally, the pancreatic juices contain a large variety of enzymes that are required for the digestion of protein and carbohydrates.

The gallbladder is a small organ that aids the liver past storing bile and concentrating bile salts. When chyme containing fat acids enters the duodenum, the bile is secreted from the gallbladder into the duodenum.

Summary

Unlike animals have evolved different types of digestive systems specialized to meet their dietary needs. Humans and many other animals have monogastric digestive systems with a single-chambered breadbasket. Birds take evolved a digestive system that includes a gizzard where the food is crushed into smaller pieces. This compensates for their inability to masticate. Ruminants that eat large amounts of plant cloth have a multi-chambered stomach that digests roughage. Pseudo-ruminants have similar digestive processes as ruminants just practice not accept the four-compartment stomach. Processing food involves ingestion (eating), digestion (mechanical and enzymatic breakdown of large molecules), absorption (cellular uptake of nutrients), and elimination (removal of undigested waste as feces).

Many organs work together to digest food and absorb nutrients. The oral cavity is the point of ingestion and the location where both mechanical and chemical breakdown of food begins. Saliva contains an enzyme chosen amylase that breaks down carbohydrates. The nutrient bolus travels through the esophagus past peristaltic movements to the tum. The tummy has an extremely acidic environment. An enzyme called pepsin digests protein in the stomach. Farther digestion and absorption take place in the minor intestine. The large intestine reabsorbs water from the undigested food and stores waste until emptying.

Exercises

1. Which of the following statements near the digestive system is false?
   1. Chyme is a mixture of nutrient and digestive juices that is produced in the tummy.
   2. Food enters the large intestine before the small intestine.
   3. In the small intestine, chyme mixes with bile, which emulsifies fats.
   4. The breadbasket is separated from the small intestine by the pyloric sphincter.
2. Which of the following statements well-nigh the minor intestine is false?
   1. Absorptive cells that line the small intestine have microvilli, small projections that increment expanse and aid in the absorption of nutrient.
   2. The inside of the pocket-size intestine has many folds, called villi.
   3. Microvilli are lined with blood vessels every bit well as lymphatic vessels.
   4. The inside of the modest intestine is chosen the lumen.
3. Which of the following is a pseudo-ruminant?
   1. moo-cow
   2. pig
   3. crow
   4. equus caballus
4. Which of the following statements is untrue?
   1. Roughage takes a long time to assimilate.
   2. Birds eat large quantities at once so that they can fly long distances.
   3. Cows do not accept upper teeth.
   4. In pseudo-ruminants, roughage is digested in the cecum.
5. The acidic nature of chyme is neutralized by ________.
   1. potassium hydroxide
   2. sodium hydroxide
   3. bicarbonates
   4. vinegar
6. The digestive juices from the liver are delivered to the ________.
   1. stomach
   2. liver
   3. duodenum
   4. colon
7. How does the polygastric digestive organisation aid in digesting roughage?
8. How do birds digest their food in the absence of teeth?
9. What is the role of the accessory organs in digestion?
10. Explain how the villi and microvilli aid in assimilation.

Answers

1. B
2. C
3. D
4. B
5. C
6. C
7. Animals with a polygastric digestive organization have a multi-chambered stomach. The four compartments of the stomach are called the rumen, reticulum, omasum, and abomasum. These chambers contain many microbes that break down the cellulose and ferment the ingested nutrient. The abomasum is the "true" breadbasket and is the equivalent of a monogastric stomach bedchamber where gastric juices are secreted. The four-compartment gastric sleeping room provides larger infinite and the microbial support necessary for ruminants to digest plant material.
8. Birds have a breadbasket chamber called a gizzard. Hither, the nutrient is stored, soaked, and ground into finer particles, oftentimes using pebbles. Once this process is complete, the digestive juices accept over in the proventriculus and continue the digestive procedure.
9. Accompaniment organs play an important role in producing and delivering digestive juices to the intestine during digestion and absorption. Specifically, the salivary glands, liver, pancreas, and gallbladder play important roles. Malfunction of whatever of these organs can lead to disease states.
10. The villi and microvilli are folds on the surface of the modest intestine. These folds increase the surface surface area of the intestine and provide more area for the absorption of nutrients.

Glossary

alimentary canal: tubular digestive system with a mouth and anus
anus: go out betoken for waste material
bile: digestive juice produced by the liver; important for digestion of lipids
bolus: mass of food resulting from chewing action and wetting by saliva
carnivore: animate being that consumes animate being flesh
chyme: mixture of partially digested nutrient and stomach juices
digestion: mechanical and chemical break downwardly of food into small organic fragments
duodenum: first office of the small intestine where a big part of digestion of carbohydrates and fats occurs
endocrine system: arrangement that controls the response of the various glands in the body and the release of hormones at the appropriate times
esophagus: tubular organ that connects the mouth to the stomach
essential food: nutrient that cannot be synthesized by the body; it must be obtained from food
gallbladder: organ that stores and concentrates bile
gastric inhibitory peptide: hormone secreted by the small intestine in the presence of fatty acids and sugars; it as well inhibits acid production and peristalsis in order to tiresome down the rate at which food enters the small intestine
gastrin: hormone which stimulates hydrochloric acrid secretion in the tummy
gastrovascular crenel: digestive system consisting of a single opening
gizzard: muscular organ that grinds food
plant eater: animate being that consumes strictly plant diet
ileum: last part of the pocket-sized intestine; connects the small intestine to the large intestine; important for absorption of B-12
ingestion: human activity of taking in food
jejunum: second function of the small intestine
lactase: enzyme that breaks down lactose into glucose and galactose
large intestine: digestive arrangement organ that reabsorbs water from undigested material and processes waste thing
lipase: enzyme that chemically breaks down lipids
liver: organ that produces bile for digestion and processes vitamins and lipids
maltase: enzyme that breaks downward maltose into glucose
mineral: inorganic, elemental molecule that carries out important roles in the body
monogastric: digestive organisation that consists of a single-chambered stomach
omnivore: animal that consumes both plants and animals
pancreas: gland that secretes digestive juices
pepsinogen: inactive form of pepsin
pepsin: enzyme found in the tum whose master office is protein digestion
peristalsis: moving ridge-similar movements of muscle tissue
proventriculus: glandular part of a bird'south stomach
rectum: surface area of the torso where carrion is stored until elimination
roughage: component of food that is depression in energy and high in fiber
ruminant: beast with a tummy divided into four compartments
salivary amylase: enzyme found in saliva, which converts carbohydrates to maltose
pocket-size intestine: organ where digestion of protein, fats, and carbohydrates is completed
somatostatin: hormone released to stop acid secretion when the stomach is empty
sphincter: band of muscle that controls movement of materials throughout the digestive tract
stomach: saclike organ containing acidic digestive juices
villi: folds on the inner surface of the small intestine whose role is to increment absorption expanse
vitamin: organic substance necessary in small amounts to sustain life

Source: https://opentextbc.ca/biology/chapter/15-1-digestive-systems/

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