Nutrition 1: Food and the Digestive System

Preparation:

Mitochondria - Turning on the Powerhouse
Water and minerals are reabsorbed back into the blood in the colon large intestine where the pH is slightly acidic about 5. Though students know they must eat to live, they may not have made the distinct connections between food and the body properly repairing itself, or food and growth; even a connection as simple as a lack of iron or carbohydrates making one tired. To learn more, including information on some other excellent products, or to order online, Click Here To Order. Saliva, a liquid secreted by the salivary glands , contains salivary amylase , an enzyme which starts the digestion of starch in the food; the saliva also contains mucus , which lubricates the food, and hydrogen carbonate , which provides the ideal conditions of pH alkaline for amylase to work. Food travels through these organs in the following order: Digestion begins in the mouth. The small bowel has 3 main sections:

www.lessontutor.com: the Digestive System- printable picture worksheet

Digestive System of the Upper Torso

This simple model represents the length and sequence of each organ in the digestive system. It does not model the structure of each organ. As students study the path of food through the digestive system, it is valuable to give them a more concrete sense of the length of each part of the system using this simple model.

Students who understand how different stages of digestion occur as food travels throught he system, will better learn the sequence through which food passes. An overarching theme in biology is the connection between structure and function. I often stress this with my students. Please see Sarah Hughes' recent blog, " From Tactile Models to Tactile Graphics " for an excellent model that includes both the structure and the length of the organs of the digestive system.

Air enters the larynx anteriorly but anything swallowed has priority and the passage of air is temporarily blocked. The pharynx is innervated by the pharyngeal plexus of the vagus nerve. The pharynx joins the esophagus at the oesophageal inlet which is located behind the cricoid cartilage.

The esophagus , commonly known as the foodpipe or gullet, consists of a muscular tube through which food passes from the pharynx to the stomach. The esophagus is continuous with the laryngopharynx. It passes through the posterior mediastinum in the thorax and enters the stomach through a hole in the thoracic diaphragm —the esophageal hiatus , at the level of the tenth thoracic vertebra T It is divided into cervical, thoracic and abdominal parts. The pharynx joins the esophagus at the esophageal inlet which is behind the cricoid cartilage.

At rest the esophagus is closed at both ends, by the upper and lower esophageal sphincters. The opening of the upper sphincter is triggered by the swallowing reflex so that food is allowed through. The sphincter also serves to prevent back flow from the esophagus into the pharynx. The esophagus has a mucous membrane and the epithelium which has a protective function is continuously replaced due to the volume of food that passes inside the esophagus.

During swallowing, food passes from the mouth through the pharynx into the esophagus. The epiglottis folds down to a more horizontal position to direct the food into the esophagus, and away from the trachea.

Once in the esophagus, the bolus travels down to the stomach via rhythmic contraction and relaxation of muscles known as peristalsis. The lower esophageal sphincter is a muscular sphincter surrounding the lower part of the esophagus.

The junction between the esophagus and the stomach the gastroesophageal junction is controlled by the lower esophageal sphincter, which remains constricted at all times other than during swallowing and vomiting to prevent the contents of the stomach from entering the esophagus. As the esophagus does not have the same protection from acid as the stomach, any failure of this sphincter can lead to heartburn.

The esophagus has a mucous membrane of epithelium which has a protective function as well as providing a smooth surface for the passage of food. Due to the high volume of food that is passed over time, this membrane is continuously renewed. The diaphragm is an important part of the body's digestive system. The muscular diaphragm separates the thoracic cavity from the abdominal cavity where most of the digestive organs are located. The suspensory muscle attaches the ascending duodenum to the diaphragm.

This muscle is thought to be of help in the digestive system in that its attachment offers a wider angle to the duodenojejunal flexure for the easier passage of digesting material.

The diaphragm also attaches to, and anchors the liver at its bare area. The esophagus enters the abdomen through a hole in the diaphragm at the level of T The stomach is a major organ of the gastrointestinal tract and digestive system. It is a consistently J-shaped organ joined to the esophagus at its upper end and to the duodenum at its lower end. Gastric acid informally gastric juice , produced in the stomach plays a vital role in the digestive process, and mainly contains hydrochloric acid and sodium chloride.

A peptide hormone , gastrin , produced by G cells in the gastric glands , stimulates the production of gastric juice which activates the digestive enzymes. Pepsinogen is a precursor enzyme zymogen produced by the gastric chief cells , and gastric acid activates this to the enzyme pepsin which begins the digestion of proteins. As these two chemicals would damage the stomach wall, mucus is secreted by innumerable gastric glands in the stomach, to provide a slimy protective layer against the damaging effects of the chemicals on the inner layers of the stomach.

At the same time that protein is being digested, mechanical churning occurs through the action of peristalsis , waves of muscular contractions that move along the stomach wall. This allows the mass of food to further mix with the digestive enzymes. Gastric lipase secreted by the chief cells in the fundic glands in the gastric mucosa of the stomach, is an acidic lipase, in contrast with the alkaline pancreatic lipase.

This breaks down fats to some degree though is not as efficient as the pancreatic lipase. The pylorus , the lowest section of the stomach which attaches to the duodenum via the pyloric canal , contains countless glands which secrete digestive enzymes including gastrin. After an hour or two, a thick semi-liquid called chyme is produced. When the pyloric sphincter , or valve opens, chyme enters the duodenum where it mixes further with digestive enzymes from the pancreas, and then passes through the small intestine, where digestion continues.

When the chyme is fully digested, it is absorbed into the blood. Water and minerals are reabsorbed back into the blood in the colon of the large intestine, where the environment is slightly acidic. Some vitamins, such as biotin and vitamin K produced by bacteria in the gut flora of the colon are also absorbed.

The parietal cells in the fundus of the stomach, produce a glycoprotein called intrinsic factor which is essential for the absorption of vitamin B Vitamin B12 cobalamin , is carried to, and through the stomach, bound to a glycoprotein secreted by the salivary glands - transcobalamin I also called haptocorrin , which protects the acid-sensitive vitamin from the acidic stomach contents.

Once in the more neutral duodenum, pancreatic enzymes break down the protective glycoprotein. The freed vitamin B12 then binds to intrinsic factor which is then absorbed by the enterocytes in the ileum. The stomach is a distensible organ and can normally expand to hold about one litre of food.

The stomach of a newborn baby will only be able to expand to retain about 30 ml. The spleen breaks down both red and white blood cells that are spent. This is why it is sometimes known as the 'graveyard of red blood cells'. A product of this digestion is the pigment bilirubin , which is sent to the liver and secreted in the bile.

Another product is iron , which is used in the formation of new blood cells in the bone marrow. The liver is the second largest organ after the skin and is an accessory digestive gland which plays a role in the body's metabolism.

The liver has many functions some of which are important to digestion. The liver can detoxify various metabolites ; synthesise proteins and produce biochemicals needed for digestion.

It regulates the storage of glycogen which it can form from glucose glycogenesis. The liver can also synthesise glucose from certain amino acids. Its digestive functions are largely involved with the breaking down of carbohydrates. It also maintains protein metabolism in its synthesis and degradation. In lipid metabolism it synthesises cholesterol. Fats are also produced in the process of lipogenesis.

The liver synthesises the bulk of lipoproteins. The liver is located in the upper right quadrant of the abdomen and below the diaphragm to which it is attached at one part, This is to the right of the stomach and it overlies the gall bladder. The liver produces bile , an important alkaline compound which aids digestion. Bile acts partly as a surfactant which lowers the surface tension between either two liquids or a solid and a liquid and helps to emulsify the fats in the chyme.

Food fat is dispersed by the action of bile into smaller units called micelles. The breaking down into micelles creates a much larger surface area for the pancreatic enzyme, lipase to work on.

Lipase digests the triglycerides which are broken down into two fatty acids and a monoglyceride. These are then absorbed by villi on the intestinal wall.

If fats are not absorbed in this way in the small intestine problems can arise later in the large intestine which is not equipped to absorb fats. Bile also helps in the absorption of vitamin K from the diet. Bile is collected and delivered through the common hepatic duct. This duct joins with the cystic duct to connect in a common bile duct with the gallbladder. Bile is stored in the gallbladder for release when food is discharged into the duodenum and also after a few hours.

The gallbladder is a hollow part of the biliary tract that sits just beneath the liver, with the gallbladder body resting in a small depression. Bile flows from the liver through the bile ducts and into the gall bladder for storage. The bile is released in response to cholecystokinin CCK a peptide hormone released from the duodenum. The production of CCK by endocrine cells of the duodenum is stimulated by the presence of fat in the duodenum.

It is divided into three sections, a fundus, body and neck. The neck tapers and connects to the biliary tract via the cystic duct , which then joins the common hepatic duct to form the common bile duct.

At this junction is a mucosal fold called Hartmann's pouch , where gallstones commonly get stuck. The muscular layer of the body is of smooth muscle tissue that helps the gallbladder contract, so that it can discharge its bile into the bile duct. The gallbladder needs to store bile in a natural, semi-liquid form at all times. Hydrogen ions secreted from the inner lining of the gallbladder keep the bile acidic enough to prevent hardening. To dilute the bile, water and electrolytes from the digestion system are added.

Also, salts attach themselves to cholesterol molecules in the bile to keep them from crystallising. If there is too much cholesterol or bilirubin in the bile, or if the gallbladder doesn't empty properly the systems can fail.

This is how gallstones form when a small piece of calcium gets coated with either cholesterol or bilirubin and the bile crystallises and forms a gallstone. The main purpose of the gallbladder is to store and release bile, or gall. Bile is released into the small intestine in order to help in the digestion of fats by breaking down larger molecules into smaller ones. After the fat is absorbed, the bile is also absorbed and transported back to the liver for reuse.

The pancreas is a major organ functioning as an accessory digestive gland in the digestive system. It is both an endocrine gland and an exocrine gland. The endocrine part releases glucagon when the blood sugar is low; glucagon allows stored sugar to be broken down into glucose by the liver in order to re-balance the sugar levels. The pancreas produces and releases important digestive enzymes in the pancreatic juice that it delivers to the duodenum.

The pancreas lies below and at the back of the stomach. It connects to the duodenum via the pancreatic duct which it joins near to the bile duct's connection where both the bile and pancreatic juice can act on the chyme that is released from the stomach into the duodenum. Aqueous pancreatic secretions from pancreatic duct cells contain bicarbonate ions which are alkaline and help with the bile to neutralise the acidic chyme that is churned out by the stomach.

The pancreas is also the main source of enzymes for the digestion of fats and proteins. Some of these are released in response to the production of CKK in the duodenum. The enzymes that digest polysaccharides, by contrast, are primarily produced by the walls of the intestines. The cells are filled with secretory granules containing the precursor digestive enzymes. The major proteases , the pancreatic enzymes which work on proteins, are trypsinogen and chymotrypsinogen.

Elastase is also produced. Smaller amounts of lipase and amylase are secreted. The pancreas also secretes phospholipase A2 , lysophospholipase , and cholesterol esterase.

The precursor zymogens , are inactive variants of the enzymes; which avoids the onset of pancreatitis caused by autodegradation.

Once released in the intestine, the enzyme enteropeptidase present in the intestinal mucosa activates trypsinogen by cleaving it to form trypsin; further cleavage results in chymotripsin.

The lower gastrointestinal tract GI , includes the small intestine and all of the large intestine. The lower GI starts at the pyloric sphincter of the stomach and finishes at the anus. The small intestine is subdivided into the duodenum , the jejunum and the ileum.

The cecum marks the division between the small and large intestine. The large intestine includes the rectum and anal canal. Partially digested food starts to arrive in the small intestine as semi-liquid chyme , one hour after it is eaten. After two hours the stomach has emptied. In the small intestine, the pH becomes crucial; it needs to be finely balanced in order to activate digestive enzymes.

The chyme is very acidic, with a low pH, having been released from the stomach and needs to be made much more alkaline. This is achieved in the duodenum by the addition of bile from the gall bladder combined with the bicarbonate secretions from the pancreatic duct and also from secretions of bicarbonate-rich mucus from duodenal glands known as Brunner's glands.

The chyme arrives in the intestines having been released from the stomach through the opening of the pyloric sphincter. The resulting alkaline fluid mix neutralises the gastric acid which would damage the lining of the intestine. The mucus component lubricates the walls of the intestine.

When the digested food particles are reduced enough in size and composition, they can be absorbed by the intestinal wall and carried to the bloodstream. The first receptacle for this chyme is the duodenal bulb. From here it passes into the first of the three sections of the small intestine, the duodenum. The next section is the jejunum and the third is the ileum. The duodenum is the first and shortest section of the small intestine.

It is a hollow, jointed C-shaped tube connecting the stomach to the jejunum. It starts at the duodenal bulb and ends at the suspensory muscle of duodenum. The attachment of the suspensory muscle to the diaphragm is thought to help the passage of food by making a wider angle at its attachment. Most food digestion takes place in the small intestine. Segmentation contractions act to mix and move the chyme more slowly in the small intestine allowing more time for absorption and these continue in the large intestine.

In the duodenum, pancreatic lipase is secreted together with a co-enzyme , colipase to further digest the fat content of the chyme. Use a few tablespoons of coconut butter, shreds, or oil a day in conjunction with an otherwise healthy, whole foods diet not a diet with junk foods that diminish brain health.

While an excess of anything may lead to fat storage, mild to moderate intake of coconut can be used for detoxification and energy without the need for supplements and over-the-counter drugs. Of course, it should go without saying that alcohol and an unhealthy diet can not be covered up with coconut; you still need to lead a healthy lifestyle.

Add it to a smoothie with spinach, berries, hemp, some stevia, ice, and a squeeze of lemon for a super detox, healing, and satisfying shake!

A new way that coconut is being used in the health spectrum is for digestive health. Because of the unique way it is digested, coconut does not cause digestive upset; it can, in fact, help with IBS, slow motility, inflammation, poor nutrient absorption, regularity, and can help seal the lining of the digestive tract that may be inflamed from leaky gut syndrome, inflammation, or other gastrointestinal problems.

While overdoing it is not smart, a tablespoon at meals can actually have quite the healing effect. Because it boosts your digestive health, it will also in return, boost your brain health and your overall sense of well-being.

Coconut flour is also a wonderful fiber source and protein source for those that eat a grain-free diet and suffer digestive illnesses. It is healing, filling, and will regulate the system without causing ill side effects. And finally, coconut fats fight candida yeast that lives within the digestive tract. Though you can not kill candida, it can easily take over the good bacteria in your body and feeds off sugars, processed foods, and a weak immunity.

Due to the popularity of coconut products, it may be sourced from an unreliable company that uses pesticides or chemicals, or may be processed in a way that damages the nutritional value. Look for the USDA certified seal, not just the word organic.

If you buy coconut shreds, always buy unsweetened and raw if you can not the flaked coconut you grew up eating in cakes and pies by baking brands.

Most that are organic are today, however, not all brands are. Raw Lemon Meltaway Balls. Lupus is a chronic, autoimmune disease that causes inflammation to the skin, joints, and vital organs because the immune system has gone awry.

Everyone wishes to have a normal blood pressure reading as it is commonly known that high blood pressure can lead to hypertension and increase your risk for a cardiac event or stroke.

DIGESTIVE SYSTEM FUNCTION