Digestive System Updated 2024 PDF

DIGESTIVE SYSTEM VALERIE S. HUISO, RTRP, MHA (c) DIGESTIVE SYSTEM Digestive system is a group of organs that work together to digest and absorb nutrients from the food you eat. It breaks down and absorbs nutrients from the food and liquids you consume. Your digestive system also takes care...

DIGESTIVE SYSTEM VALERIE S. HUISO, RTRP, MHA (c) DIGESTIVE SYSTEM Digestive system is a group of organs that work together to digest and absorb nutrients from the food you eat. It breaks down and absorbs nutrients from the food and liquids you consume. Your digestive system also takes care of food waste — the stuff that’s left over after you digest food. Your digestive system turns food waste into poop (stool). The digestive system is made up of the gastrointestinal tract—also called the GI tract or digestive tract—and the liver, pancreas, and gallbladder. The GI tract is a series of hollow organs joined in a long, twisting tube from the mouth to the anus. The hollow organs that make up the GI tract are the mouth, esophagus, stomach, small intestine, large intestine, and anus. The liver, pancreas, and gallbladder are the solid organs of the digestive system. Parts of the Digestive System The main parts of your digestive system are your gastrointestinal (GI) tract and your biliary tract: Your GI tract is a series of hollow organs that connect to digest and move food through your body. It includes your mouth, esophagus, stomach, small intestine and large intestine and rectum. Your biliary tract makes and releases fluids that help digestion. It includes your bile ducts, gallbladder, liver and pancreas. The Gastrointestinal Tract (GI) Your GI tract is a long tube that runs from your mouth to your anus. If you could stretch it out, it would measure 30 feet (9 meters). It’s shorter in your body because your intestines — the longest parts of the tract — coil up in your lower abdomen (belly) under your stomach. Your GI tract parts are your: 1. Mouth. This is where digestion begins. Food starts to move through your GI tract when you eat. When you swallow, your tongue pushes the food into your throat. A small flap of tissue, called the epiglottis, folds over your windpipe to prevent choking and the food passes into your esophagus. The Gastrointestinal Tract (GI) 2. Esophagus. This is a tube in the center of your chest, behind your windpipe (trachea) and in front of your spine. Once you begin swallowing, the process becomes automatic. Your brain signals the muscles of the esophagus and peristalsis begins. *Lower esophageal sphincter. When food reaches the end of your esophagus, a ringlike muscle—called the lower esophageal sphincter — relaxes and lets food pass into your stomach. This sphincter usually stays closed to keep what’s in your stomach from flowing back into your esophagus. 3. Stomach. Your stomach sits in your upper abdomen on the left side of your body. After food enters your stomach, the stomach muscles mix the food and liquid with digestive juices. The stomach slowly empties its contents, called chyme, into your small intestine. The Gastrointestinal Tract (GI) 4. Small intestine. This 22-foot-long muscular tube is the longest part of your gastrointestinal tract. It coils up in your lower abdomen and curves around your pancreas. The muscles of the small intestine mix food with digestive juices from the pancreas, liver, and intestine, and push the mixture forward for further digestion. The walls of the small intestine absorb water and the digested nutrients into your bloodstream. As peristalsis continues, the waste products of the digestive process move into the large intestine. 5. Large intestine (colon). The last step in the digestive process, the large intestine includes rectum and anus. Waste products from the digestive process include undigested parts of food, fluid, and older cells from the lining of your GI tract. The large intestine absorbs water and changes the waste from liquid into stool. Peristalsis helps move the stool into your rectum. 6. Rectum. The lower end of your large intestine, the rectum, stores stool until it pushes stool out of your anus during a bowel movement. The BILIARY TRACT Your biliary tract is in your upper abdomen (belly). Organs in your biliary tract support digestion by delivering bile and enzymes that help your small intestine break down food. Your biliary tract includes your: 1. Bile ducts. You have bile ducts inside and outside your liver. They connect to your gallbladder. Bile ducts carry bile from your liver to your gallbladder for storage, or to the small intestine for use. 2. Liver. An organ and a gland, your liver is on the right side of your body under your ribs. Your liver makes a digestive juice called bile that helps digest fats and some vitamins. The BILIARY TRACT 3. Gallbladder. Your gallbladder is tucked below your liver on the right side of your body. Your gallbladder stores bile between meals. When you eat, your gallbladder squeezes bile through the bile ducts into your small intestine. 4. Pancreas. This organ is behind your stomach and in front of your spine on the right side of your body. Your pancreas makes a digestive juice that has enzymes that break down carbohydrates, fats, and proteins. The pancreas delivers the digestive juice to the small intestine through small tubes called ducts. THE DIGESTIVE SYSTEM  MOUTH SALIVA The food is broken down by the teeth It lubricates food with mucus, and mixed with saliva. making it easier to swallow. Saliva is excreted by three pairs of It contains the enzyme salivary glands: amylase, which acts on cooked The parotid gland (below the ear) starch turning some of it into maltose. The submandibular (under the tongue) It keeps the mouth and teeth clean. The sublingual (under the tongue) The ball of food that leaves the mouth is known as a bolus. Bolus is Saliva contains water, mucus and the a food that has been chewed and enzyme salivary amylase. mixed in the mouth with saliva  ACCESSORY ORGANS IN THE DIGESTIVE SYSTEM TONGUE TASTE CENTERS FUNCTIONS OF THE TONGUE Taste: it is covered with thousands of taste buds. These are sensitive to salt, sweet, sour and bitter chemicals in food and drink. They help us enjoy food and drink and warn us when food, drink are off or inedible. Chewing: the tongue aids chewing by moving the food around the mouth, pushing it between the teeth and covering it with saliva, which contains enzymes that start the digestive process. The food is turned into a partially digested mass known as a bolus. Swallowing: when the food is ready to travel to the stomach, the tongue pushes it to the back of the mouth.  ACCESSORY ORGANS IN THE DIGESTIVE SYSTEM TEETH There are four different types An adult human has 32 teeth, 16 of tooth in either jaw Incisors The shape and size of the tooth -These cut and bite food varies with the job it has to do Canines These grasp and tear food Pre-molars -These grind and chew food Molars These also grind and chew food Structure of the Esophagus and its Functions The food passes into the pharynx (a muscular tube behind the mouth) and down the esophagus. The epiglottis a small flap of cartilage blocks the entrance to the larynx, this stops the food going down the wrong way and prevents choking. It is a muscular tube. It leads from the pharynx to the stomach. Functions To carry chewed food from the pharynx to the stomach. Food moves along it by a muscular contraction known as peristalsis. The muscle fibers contract and relax which acts like a wave on the tube, pushing the bolus forward. It’s lining secretes mucus to lubricate the passage of food. Stomach FUNCTIONS OF THE STOMACH It digests protein through the action of enzymes. It churns food with the gastric juices. It helps lubricate the food by producing mucus. It absorbs alcohol. It kills bacteria by producing hydrochloric acid. STOMACH STRUCTURE It is a J-shaped, elastic organ. The walls of the stomach is Food enters it from the made up of layers of muscle. esophagus through the cardiac It has an inner mucous sphincter. membrane. The cardiac sphincter, is a valve This membrane has lots of folds. that stops back flow of the When the stomach is full these stomach`s contents. folds stretch out, enabling it to Food leaves the stomach expand, then they contract through the pyloric sphincter when the stomach empties. into the duodenum (first part of the small intestine). STRUCTURE OF THE SMALL INTESTINE It is seven meters long. It is divided into three parts: The duodenum The jejunum The ileum The walls has four layers: A muscular layer -A layer containing blood vessels, lymph vessels, and nerves. A submucous layer A mucous layer. FUNCTIONS OF THE SMALL INTESTINE Pancreatic juices is secreted into the duodenum and contains the following enzymes: Trypsin: converts proteins into shorter chains. Lipase: converts fats into fatty acids and glycerol. Amylase: converts starch into disaccharides. Bile: emulsifies fats (breaks them into smaller droplets). Intestinal Juices have the following enzymes: Maltase, sucrase, lactase: change disaccharides into monosaccharides. Peptidase: changes polypeptides into amino acids. GASTRIC JUICES Hydrochloric acid neutralises bacteria and activates pepsin. Rennin is an enzyme that curdles milk protein in infants. Pepsin is an enzyme that breaks down proteins into peptones. What is the difference between pancreatic juice and gastric juice? The main difference between gastric juice and pancreatic juice is that the gastric juice mainly contains enzymes for the digestion of proteins whereas the pancreatic juice mainly contains enzymes for the digestion of carbohydrates and fat. Furthermore, gastric juice is acidic while pancreatic juice is alkaline. ENZYMES An enzyme is a biological catalyst A catalyst speeds up chemical reactions Enzymes speed up biological reactions All chemical reactions that take place in living systems require the action of an enzyme Digestive enzymes break food down into smaller, more soluble substances This allows the food to be absorbed into the blood  ENZYMES An example of a digestive enzyme is amylase Amylase is present in saliva Amylase chemically breaks down starch Amylase converts starch into a sugar called maltose (STARCH MALTOSE) The substance that an enzyme works on is known as its SUBSTRATE The substance formed by the enzyme is known as its PRODUCT Therefore starch is the substrate for amylase and maltose is its product SMALL INTESTINE The inner wall is covered in villi, tiny hair like projections which increase the surface area for absorption. Each villi contain blood vessels and lymph vessels. STRUCTURE OF THE LARGE INTESTINE It deals with waste. It is about 1.5m long. It consists of the following: The cecum: a small pouch; the ileum empties its contents into the caecum through the ileo-cecal valve. The colon: ascending, transverse, descending colon. The appendix: narrow tube attached to the caecum. The rectum. The anus FUNCTION OF THE LARGE INTESTINE Whatever remains of the food, is passed into the large intestine To reabsorb water and vitamins left in digestive waste. It secretes mucus to help the movement of feces. Short term storage of feces in the rectum. Many bacteria live in the large intestine, they are harmless in the colon and may be useful e.g. produce Vitamin K. Defecation: peristalsis pushes waste along the colon and then it is passed out of the body. THE DIGESTIVE PROCESS Food can be broken down (digested) in one of two ways: Physical Digestion This is where large pieces of food are broken down into smaller pieces of the same food Chemical Digestion This is where food is broken down into a different substance that can easily pass into the blood THE DIGESTIVE PROCESS STAGES OF NUTRITION Nutrition is a method in which the food is consumed by the STAGES OF NUTRITION organisms and utilizing the nutrients from the food. Ingestion Nutrition is the process of taking in food and converting it into Digestion energy and other vital nutrients Absorption required for life. Assimilation The main nutrients are Egestion carbohydrates, fat, protein, vitamins and minerals, The path from where food passes are called alimentary canal. STAGES OF NUTRITION 1. Ingestion: Ingestion is the process in which the food is taken inside the body through the mouth. In the mouth, food is broken down into small pieces and chewed and churned by teeth Saliva is mixed with food by the tongue. In saliva, salivary amylase (ptyalin) enzyme is present which help in the digestion of carbohydrate. Thus, Initial digestion takes place in the mouth by saliva When saliva is mixed with food called bolus. The bolus passes into the stomach through the esophagus. In esophagus, no digestion occurs. 2. DIGESTION  STAGES OF NUTRITION 3. Absorption : The separated nutrients get absorbed in the blood is called absorption. In this process, a finger-like projections called villi help. 4. Assimilation: The absorbed nutrients utilized by the body cells or tissues is called assimilation. 5. Egestion: The undigested waste expelled out from the body through anus is called egestion.  Common Conditions and Disorders that affect the Digestive System Acid Reflux or GERD- Stomach acid that flows into your esophagus causes indigestion and heartburn. Celiac Disease-his is an autoimmune disorder that’s triggered when you eat gluten, a type of protein. Constipation-Hard, dry poops from constipation are one of the most frequent gastrointestinal issues. Diarrhea-Loose, watery poop is one of the most common gut issues. Diverticulosis or diverticulitis- These conditions happen when little pouches (diverticula) develop in your colon. Common Conditions and Disorders that affect the Digestive System Gastroenteritis (stomach flu)-Stomach flu is a viral infection in your stomach and intestines. Hemorrhoids- Swollen veins inside of your rectum or outside of your anus can itch and hurt. Stomach ulcers-These are open sores in your stomach lining. Inflammatory Bowel Disease (IBD)- Chron’s disease and ulcerative colitis are two common inflammatory bowel diseases. Is a term that describes disorders involving long-standing (chronic) inflammation of tissues in your digestive tract. TYPES OF INFLAMMATORY BOWEL DISEASE (IBD) Ulcerative colitis. This condition involves inflammation and sores (ulcers) along the lining of your large intestine (colon) and rectum. Crohn's disease. This type of IBD is characterized by inflammation of the lining of your digestive tract, which often can involve the deeper layers of the digestive tract. Crohn's disease most commonly affects the small intestine. However, it can also affect the large intestine and uncommonly, the upper gastrointestinal tract. Common Conditions and Disorders that affect the Digestive System Nausea- is a diffuse sensation of unease and discomfort, sometimes perceived as an urge to vomit. It can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, abdomen, or back of the throat Irritable bowel syndrome (IBS)- is a functional gastrointestinal disorder characterized by a group of symptoms that commonly include abdominal pain, abdominal bloating and changes in the consistency of bowel movements. Gallstone- is a stone formed within the gallbladder from precipitated bile components. The term cholelithiasis may refer to the presence of gallstones or to any disease caused by gallstones, and choledocholithiasis refers to the presence of migrated gallstones within bile ducts