Biological Sciences
Human Digestive System
The human digestive system is a complex network of organs and glands that work together to break down food into nutrients that the body can absorb and use for energy, growth, and repair. It includes the mouth, esophagus, stomach, small and large intestines, liver, and pancreas. Digestion involves mechanical and chemical processes that transform food into molecules that can be absorbed into the bloodstream.
Written by Perlego with AI-assistance
Related key terms
1 of 5
10 Key excerpts on "Human Digestive System"
eBook - PDF- Jonathan Bubb(Author)
- 2021(Publication Date)
- Cengage Learning EMEA(Publisher)
733 Chapter 13 The Gastrointestinal System Chapter Introduction While sitting down to enjoy a tasty meal is often considered a relaxing experience, it requires the gastrointestinal system to kick into high gear. Food that is consumed must be broken down into a form that is usable by the body to promote health and growth and prevent disease. In this chapter, we learn how the GI system breaks down and digests the food we consume into absorbable nutrients and expels waste. UNIT INTRODUCTION Digestion is essential to life; at its most basic, it breaks down food into smaller parts until they can be absorbed by the human body, providing fuel to power the body’s activities. As the body digests food, it breaks it down into the nutrients that can be used, absorbs these nutrients into the bloodstream, and then rids the body of any wastes. SECTION 6 Gastrointestinal System and Human Nutrition UNIT OBJECTIVE 13.1 Describe the general structure and functions of the digestive system. Identify the general functions of the digestive system. LEARNING OBJECTIVE 13.1.1 Describe the general functions of the digestive system. LEARNING OBJECTIVE 13.1.2 KEY TERMS absorption Passage of digested food materials from the digestive tract of an individual into the cardiovascular and lymphatic systems for distribution to the body’s cells. alimentary canal The long muscular tube of the digestive system that transports ingested materials from the mouth to anus; site of mechanical and chemical digestion. chemical digestion Molecular breakdown of food by bile and enzymes secreted throughout the digestive system. digestion Breakdown of the large food materials into smaller particles by mechanical and chemical digestion. excretion Discharge of waste from the body. mechanical digestion Physical breakdown of food. peristalsis Process of smooth muscle contraction along the GI tract that forces material to move further along the tract.
eBook - PDF- Marie Boyle(Author)
- 2022(Publication Date)
- Cengage Learning EMEA(Publisher)
When several organs work together cooperatively, these organs are considered parts of a body system. One such system, the digestive system, consists of organs and tissues working together to supply necessary energy, water, and essential nutrients to every cell in our bodies. Copyright 2023 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 76 C h a p t e r 3 A n a t o m y f o r N u t r i t i o n ’ s S a k e 3.1 The Digestive System You may eat meals only two or three times a day, but your body’s cells need nutri- ents 24 hours a day. Providing the needed nutrients requires cooperation of mil- lions of specialized cells. When the body’s cells are deprived of fuel, specific nerve cells in the hypothalamus (part of the brain) detect this condition and generate nerve impulses that signal hunger to the conscious part of the brain. Hunger and appetite are experienced in the cortex of the brain—the thinking, outer layer (see Figure 3-2). Hunger (involuntary action) has primary control over how much we eat, while the type of food we look for and eat is determined by appetite (voluntary action). The digestive system is made up of the gastrointestinal (GI) tract—also called the digestive tract—and the liver, pancreas, and gallbladder. The gastrointestinal tract provides the body with a constant supply of water and nutrients.
eBook - PDFVisualizing Nutrition
Everyday Choices
- Mary B. Grosvenor, Lori A. Smolin(Authors)
- 2017(Publication Date)
- Wiley(Publisher)
51 CHAPTER OUTLINE The Organization of Life 52 The Digestive System 55 • Organs of the Digestive System • Digestive System Secretions Digestion and Absorption of Nutrients 57 • The Mouth • The Stomach • The Pharynx • The Small Intestine • The Esophagus • The Large Intestine The Digestive System in Health and Disease 65 • The Intestinal Microbiota • Gut Immune Function in Health and Disease What a Scientist Sees: Bacteria on the Menu Debate: Should You Be Gluten Free? • Other Digestive System Problems and Discomforts What Should I Eat? For Digestive Health Thinking It Through: A Case Study on How Changes in the Digestive System Affect Nutrition Delivering Nutrients and Eliminating Wastes 73 • The Cardiovascular System • The Lymphatic System • Elimination of Wastes An Overview of Metabolism 77 • Releasing Energy • Synthesizing New Molecules Digestion: From Meals to Molecules The human body has been compared to a car: We fill the tank of our car with gasoline to get down the highway; we fill our body with food to get on with life. In both “machines,” combustion with oxygen releases energy. Our bodies are machine-like in another way as well: They are virtu- ally identical to one another. Like cars, we look different on the outside but are basically the same on the inside. The processes that drive us—like the internal combustion engine, no matter where it’s manufactured—are more similar than different because they are based on the same funda- mental chemical reactions. Despite the similarities, there are differences between human bod- ies and machines. An automobile cannot use gasoline to heal itself or to grow, as we do with nutrients. Although a gas tank and a stomach both store fuel, gasoline travels unchanged through the fuel line to the engine, whereas in humans the digestive system must break down the fuel into smaller units before it can be used by the body.
eBook - PDFNutritional Sciences
From Fundamentals to Food, Enhanced Edition
- Michelle McGuire, Kathy Beerman(Authors)
- 2017(Publication Date)
- Cengage Learning EMEA(Publisher)
How Does the Digestive System Break Down Food into Absorbable Components? To nourish your body, your digestive system methodically disassembles the com- plex molecules in food into simpler basic components. This arduous task re- quires many organ systems, but primarily it is the digestive system that gets the job done. Your digestive system is made up of the digestive tract and accessory organs. The digestive tract, more commonly known as the gastrointestinal (GI) tract or alimentary tract, can be thought of as a hollow tube that runs from the mouth to the anus (Figure 3.12). Organs that make up the GI tract include the mouth, esophagus, stomach, small intestine, and large intestine. The accessory organs, which participate in digestion but are not part of the GI tract, include the salivary glands, pancreas, and biliary system (liver and gallbladder). The accessory organs release secretions needed for the process of digestion into ducts, which empty into the lumen, the inner cavity that spans the entire length of the GI tract. Together, the GI tract and accessory organs carry out three important functions: (1) digestion, the physical and chemical breakdown of food; (2) absorption, the transfer of nutrients from the GI tract into the blood or lymphatic circulatory systems; and (3) egestion, the process whereby solid waste (feces) is expelled from the body. THE GI TRACT HAS FOUR TISSUE LAYERS THAT CONTRIBUTE TO THE PROCESS OF DIGESTION As shown in Figure 3.13, the digestive tract contains four major tissue layers— the mucosa, submucosa, muscularis, and serosa. Each tissue layer contributes to the overall function of the GI tract by providing secretions, movement, com- munication, and protection. neurotransmitters Chemical messengers released from nerve cells that transmit information. hormones Substances released from glands or cells in response to various stimuli that exert their effect by binding to receptors on specific tissues.
eBook - PDFVisualizing Nutrition
Everyday Choices
- Mary B. Grosvenor, Lori A. Smolin(Authors)
- 2021(Publication Date)
- Wiley(Publisher)
51 51 David McLain / Aurora Photos CHAPTER OUTLINE The Organization of Life 52 The Digestive System 55 • Organs of the Digestive System • Digestive System Secretions Digestion and Absorption of Nutrients 57 • The Mouth • The Stomach • The Pharynx • The Small Intestine • The Esophagus • The Large Intestine The Digestive System in Health and Disease 65 • Immune Function and the Role of the Gut • The Intestinal Microbiota What a Scientist Sees: Bacteria on the Menu • Food Allergies • Gluten-Related Disorders Debate: Should You Be Gluten Free? • Other Digestive System Problems and Discomforts What Should I Eat? For Digestive Health Thinking It Through: A Case Study on How Changes in the Digestive System Affect Nutrition Delivering Nutrients and Eliminating Wastes 74 • The Cardiovascular System • The Lymphatic System • Elimination of Wastes An Overview of Metabolism 78 • Releasing Energy • Synthesizing New Molecules What Is Happening in This Picture? Digestion: From Meals to Molecules The human body has been compared to a car: We fill the tank of our car with gasoline to get down the highway; we fill our body with food to get on with life. In both “machines,” combustion with oxygen releases energy. Our bodies are machine-like in another way as well: They are virtu- ally identical to one another. Like cars, we look different on the outside but are basically the same on the inside. The processes that drive us—like the internal combustion engine, no matter where it’s manufactured—are more similar than different because they are based on the same funda- mental chemical reactions. Despite the similarities, there are differences between human bod- ies and machines. An automobile cannot use gasoline to heal itself or to grow, as we do with nutrients.
eBook - PDF- Mary B. Grosvenor, Diana Bedoya(Authors)
- 2014(Publication Date)
- Wiley(Publisher)
For example, the digestive system works with the circulatory system to provide cells with the required oxygen and nutrients needed for the human organism to move and function. © Can Stock Photo Inc. / monkeybusiness 62 CHAPTER 3 Digestion: From Meals to Molecules 1. How are atoms, molecules, and cells related to one another? 2. How do the endocrine and nervous systems interact with the digestive system? The 11 major organ systems of the human body Table 3.1 System Main components Main function Circulatory Heart, blood vessels Transportation of blood, which carries oxygen, nutrients, and wastes etc. Digestive Digestive tract (mouth, pharynx, esophagus, stomach, intestines), accessory organs (salivary glands, pancreas, liver, gallbladder) Digestion, absorption of meals Endocrine Pituitary, adrenal, thyroid, pancreas, and other ductless glands Production and release of hormones (chemical messengers) Integumentary Skin, hair, glands, fingernails Protection, glandular secretion, temperature regulation, regulation of body temperature Lymphatic Lymph nodes, lymph vessels, spleen Drainage, immunity, transportation of fat-soluble nutrients Muscular Skeletal muscles Movement, structure, and production of heat Nervous Sensory receptors, nerves, spinal cord, brain Generation of response to stimuli from external and internal environments, transmission of impulses to activate muscles and glands, integration of activities of other systems Reproductive Ovaries, vagina, uterus, mammary glands (females) Testes, penis (males) Production of offspring Production of sex hormones Respiratory Lungs, air passageways, trachea, pharynx, larynx Gas exchange with external environment Skeletal Bones, cartilage, joints Structure, support, framework for the movement of muscles Urinary Kidney, bladder, urethra Elimination of wastes, regulation of water, pH and electrolyte balance he digestive system is the organ system that is primarily responsi- ble for the digestion and absorption of nutrients.
No longer available |Learn more- Azhar ul Haque Sario(Author)
- 2023(Publication Date)
- tredition(Publisher)
Storage of Bile: The bile produced by the liver is stored and concentrated in the gall bladder. When we eat, especially foods rich in fats, the gall bladder contracts, releasing bile into the small intestine to assist in fat digestion.In summary, these regions of the digestive system work in concert to ensure that nutrients from the food we eat are efficiently broken down and absorbed. This complex interplay of organs and enzymes is essential for maintaining the body's energy balance and overall health.The Human Digestive System is a complex and efficient system designed to convert food into energy and essential nutrients required by the body. Three important components of this system are the pancreas, the ileum and colon, and the rectum and anus, each playing a distinct role in the digestive process.Pancreas – Alkaline Secretion Containing Amylase, Protease, and LipaseThe pancreas, a vital organ in the digestive system, performs crucial functions primarily related to digestion and blood sugar regulation. It secretes an alkaline fluid that contains digestive enzymes, crucial for breaking down various components of the food we consume.Amylase: This enzyme specializes in breaking down carbohydrates into simpler sugars. When food enters the small intestine from the stomach, pancreatic amylase acts on the starches, transforming them into maltose, a simpler sugar, facilitating easier absorption.Protease: This is crucial as proteins are complex molecules, and breaking them into simpler forms allows for their absorption into the bloodstream.Lipase: This enzyme is responsible for breaking down lipids (fats) into fatty acids and glycerol. Lipase ensures that fats are converted into forms that can be easily absorbed by the intestinal lining.The alkaline nature of the pancreatic secretion is also significant. It neutralizes the acidic chyme (partially digested food) that comes from the stomach, creating an optimal pH environment for the function of digestive enzymes in the small intestine.
eBook - PDF- Cecie Starr, Beverly McMillan(Authors)
- 2015(Publication Date)
- Cengage Learning EMEA(Publisher)
3. The preferred energy sources for the body are . 4. The human body cannot produce its own vitamins or minerals, nor can it produce certain and . 5. Digestion is completed and products are absorbed in the . a. mouth c. small intestine b. stomach d. large intestine Figure 11.27 Fill in the blanks for substances that cross the lining of the small intestine. (© Cengage Learning) Major Components Mouth Start of digestive system, where food is (oral cavity) moistened and chewed; polysaccharide digestion begins Pharynx Entrance to tubular parts of digestive and respiratory systems Esophagus Muscular tube, moistened by saliva, that moves food from pharynx to stomach Stomach Sac where food mixes with gastric fluid and protein digestion begins; stretches to store food taken in faster than can be processed; gastric fluid destroys many microbes Small The first part (duodenum) receives secretions intestine from the liver, gallbladder, and pancreas Most nutrients are digested, absorbed in second part (jejunum) Some nutrients absorbed in last part (ileum), which delivers unabsorbed material to colon Colon (large Concentrates and stores undigested matter intestine) (by absorbing mineral ions and water) Rectum Distension triggers expulsion of feces Anus Terminal opening of digestive system Accessory Organs Salivary Glands (three main pairs, many minor ones) glands that secrete saliva, a fluid with polysaccharide- digesting enzymes, buffers, and mucus (which moistens and lubricates ingested food) Pancreas Secretes enzymes that digest all major food molecules and buffers against HCl from stomach Liver Secretes bile (used in fat emulsification); role in carbohydrate, fat, and protein metabolism Gallbladder Stores and concentrates bile from the liver TABLE 11.9 Summary of the Digestive System Copyright 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part.
eBook - PDF- Linda DeBruyne, Kathryn Pinna, Eleanor Whitney, , Linda DeBruyne, Kathryn Pinna, Eleanor Whitney(Authors)
- 2019(Publication Date)
- Cengage Learning EMEA(Publisher)
Saliva also helps dissolve the food so that you can taste it; only particles in solution can react with taste buds. THE BODY’S ABILITY TO TRANSFORM THE FOODS A PERSON EATS INTO THE nutrients that fuel the body’s work is quite remarkable. Yet most people probably give little, if any, thought to all the body does with food once it is eaten. This chapter offers the reader the opportunity to learn how the body digests, absorbs, and transports the nutrients and how it excretes the unwanted substances in foods. One of the beauties of the digestive tract is that it is selective. Materials that are nutritive for the body are broken down into particles that can be absorbed into the bloodstream. Most of the nonnutritive materials are left undigested and pass out the other end of the digestive tract. gastrointestinal (GI) tract: the digestive tract. The principal organs are the stomach and intestines. gastro 5 stomach digestion: the process by which complex food particles are broken down to smaller absorbable particles. These terms are listed in order from start to end of the digestive system. mouth: the oral cavity containing the tongue and teeth. pharynx (FAIR-inks): the passageway leading from the nose and mouth to the larynx and esophagus, respectively. epiglottis (epp-ih-GLOTT-iss): cartilage in the throat that guards the entrance to the trachea and prevents fluid or food from entering it when a person swallows. ● epi 5 upon (over) ● glottis 5 back of tongue esophagus (ee-SOFF-ah-gus): the food pipe; the conduit from the mouth to the stomach. sphincter (SFINK-ter): a circular muscle surrounding, and able to close, a body opening. Sphincters are found at specific points along the GI tract and regulate the flow of food particles. ● sphincter 5 band (binder) esophageal (ee-SOF-a-GEE-al) sphincter: a sphincter muscle at the upper or lower end of the esophagus. The lower esophageal sphincter is also called the cardiac sphincter.
eBook - PDF- Craig Freudenrich, Gerard J. Tortora(Authors)
- 2011(Publication Date)
- Wiley(Publisher)
The chemical se- cretions and mechanical mixing work together to break down food into simple carbohydrates, lipids, amino acids, nucleic acids, and vitamins. These substances are ab- sorbed mainly in the small intestine, but some are also absorbed in the stomach and large intestine. What re- mains of your breakfast after it passes through the large intestine moves into the rectum and is excreted from the body. For a summary of the functions of the digestive or- gans, see Table 14.2. Summary of digestive organs and their functions Table 14.2 Organ Functions Mouth See other listings in this table for the functions of the tongue, salivary glands, and teeth, all of which are in the mouth. Additionally, the lips and cheeks keep food between the teeth during mastication, and buccal glands lining the mouth produce saliva. Tongue Maneuvers food for mastication, shapes food into a bolus, maneuvers food for deglutition, detects taste and touch sensations, and initiates digestion of triglycerides. Salivary glands Produce saliva, which softens, moistens, and dissolves foods; cleanses mouth and teeth; and initiates the digestion of starch. Teeth Cut, tear, and pulverize food to reduce solids to smaller particles for swallowing. Pharynx Receives a bolus from the mouth and passes it into the esophagus. Esophagus Receives a bolus from the pharynx and moves it into the stomach.This requires relaxation of the upper esophageal sphincter and secretion of mucus. Stomach Mixing waves soak food, mix it with the secretions of gastric glands (gastric juice), and reduce food to chyme. Gastric juice activates pepsin and kills many microbes in food. Instrinsic factor aids absorption of vitamin B 12 from the colon. The stomach serves as a reservoir for food before releasing it into the small intestine.
Index pages curate the most relevant extracts from our library of academic textbooks. They’ve been created using an in-house natural language model (NLM), each adding context and meaning to key research topics.
