Digestive, Respiratory, and Circulatory Systems Working Together Nutrient Absorption Digestive, Respiratory, and Circulatory Systems Working Together

Nutrition  The Vital Nutrients - Six basic kinds of nutrients can be found: 1. Carbohydrates Main source of energy 2. Fats Used to store energy 3. Proteins Form part of muscles and many cell structures, including the cell membrane

Serve as structural materials 5. Vitamins Ca 4. Minerals Serve as structural materials 5. Vitamins Needed for growth and metabolism 6. Water Facilitates chemical reactions, helps dissolve materials and helps maintain the body’s temperature Cr Mg Vitamin D Vitamin C B12

Following the Digestion of a Meal Functions of the Digestive System Main function is to disassemble the food you eat into its component molecules so that it can be used as energy (ATP) by your body.

All of these organs work together to break down food into simpler compounds that can be absorbed by the body.

Four Stages of Digestion Ingestion- the act or process of taking food or other substances into the body. Digestion- the process of converting food to an absorbable form by breaking it down to simpler compounds. Absorption- the process of moving water and solutes from outside of the cell into the interior. Elimination-the process of the body ridding itself of any indigestible material.

Digestion/Absorption Summary Digestion begins as soon as you start eating. Enzymes in your saliva start the process of converting food into energy. Via mechanical and chemical mechanisms, large nutrient molecules are broken down into smaller ones that your intestine absorbs into the blood stream. Cells then take up these nutrient molecules and use them to build new molecules and provide their cellular energy needs. Cells can also store the molecules for later use.

 The Mouth - The disassembly line STARTS at the mouth What happens when you chew? Your tongue moves food around & helps position it between your teeth Chewing is a form mechanical digestion = the physical process of breaking down food into smaller pieces. This prepares food for chemical digestion Chemical digestion = the process of changing food on a molecular level through the action of enzymes

Chemical Digestion begins in Mouth Saliva in mouth contains digestive enzymes, called amylase, which breaks down starch into smaller molecules In the stomach, amylase continues to digest food for about 30 min.

Starch

Swallowing Your Food Chewed food becomes a ball and is swallowed Swallowing forces food into throat and then to the esophagus = a muscular tube that connects the mouth to the stomach Food moves through the esophagus by peristalsis = a series of involuntary smooth muscle contraction along the walls of the digestive tract

Peristalsis

The epiglottis = a flap of cartilage that closes over the opening to the respiratory tract as you swallow, keeping food out After food passes, epiglottis opens again If you talk or laugh as you swallow, food may enter the upper portion of the respiratory tract Your response is to choke & cough, forcing food out of the respiratory tract

 The Stomach Stomach = a muscular pouchlike enlargement of the digestive tract Muscle Churning The walls of the stomach are composed of 3 layers of involuntary muscles When the muscles contract, they work to physically breakdown food, creating smaller pieces The pieces mix with digestive juices produced by the stomach

Chemical Digestion in the stomach The lining of the stomach contains millions of glands that secrete a mixture of chemicals called gastric juice Gastric juice contains pepsin & hydrochloric aced Pepsin = an enzyme that begins the chemical digestion of proteins in food

The lining of the stomach secretes mucus that forms a protective layer b/t it and the acidic environment of the stomach Food remains in stomach for about 2-4 hrs When food leaves it is the consistency of tomato soup (YUMMY!)

 The Small Intestine - Small intestine = a muscular tube about 6 m long Called “small” because of how narrow it is (only 2.5 cm in diameter) - Digestion is COMPLETED here - First 25 cm of the small intestine called the duodenum

Secretions of the Pancreas Pancreas = soft, flattened gland that secretes both digestive enzymes & hormones The mixture of enzymes it releases break down carbs, proteins, & fats

Secretions of the Liver Liver = large, complex organ that produces bile Bile = chemical substance that helps break down fats Made by the liver, but stored in the gallbladder From the gallbladder, bile passes into duodenum Bile causes further digestion by breaking large drops of fat into smaller droplets Gallstones form when bile in the gallbladder becomes too concentrated due to high levels of cholesterol in you diet

LIVER

Absorption of Food Liquid food stays in the intestine for 3-5 hrs. as it is moved through As food moves it passes over thousands of tiny fingerlike structures called villus = a single projection on the lining of small intestine that function in the absorption of food Now that food is in the form of small molecules, it can be absorbed directly into the cells of the villi (plural for villus) Food then diffuses into blood vessels of the villus & enter the bloodstream * Villi are the link between the digestive system & the circulatory system

 The Large Intestine - All indigestible material from a meal then moves into the large intestine = a muscular tube that is also called the colon - Large intestine is only about 1.5 m long, but it is much wider that the small intestine ( about 6.5cm in diameter)

Water Absorption As indigestible mixture passes through the large intestine, water and salts are absorbed by the intestinal walls, leaving behind a more solid material This way water in NOT wasted

Bacteria in the large intestine make some B vitamins and Vitamin K, which are absorbed as needed by the body These bacteria also stop harmful bacteria from colonizing, reducing the risk of intestinal infections

Elimination of Wastes After 18-24 hrs in the large intestine, the remaining indigestible material, now called feces, reaches the rectum Rectum = the last part of the digestive system

Respiratory/Circulatory Systems Functions Your respiratory system takes in oxygen from the atmosphere and moves that oxygen into the blood stream by allowing it to move across the membranes of the lungs into the blood vessels. The circulatory system then carries oxygen to all the cells in the body and picks up carbon dioxide waste, which it returns to the lungs. Carbon dioxide diffuses from the blood into the lungs , and you exhale it into the atmosphere.

Digestive Dependence Upon Respiration The digestive tract functions by using muscular contractions to break up food and move it along the tract. These muscles depend upon oxygen in order to function. Without oxygen, your digestive tract would stop working.

Respiratory Dependence Upon Digestion Your respiratory tract wouldn’t be able to function without the products of digestion. The process of exhalation is passive; does not require muscular contraction. Contraction of the diaphragm and intercostal muscles requires fuel. This fuel is primarily in the form of carbohydrates or lipids.

Blood And Energy Your body relies primarily on carbohydrates and fats from the foods you eat for energy. The blood transports these chemicals to the cells of your body through the circulatory system.

Cellular Dependence Upon All Three Systems The body cells depend upon products of both the respiratory and digestive systems’ functions in order to maintain themselves To produce energy, cells burn nutrient molecule fuel in oxygen. Digestive tract provides nutrient molecules, while the respiratory tract provides oxygen. Circulatory system transports both products to the cell.

Neural and Hormonal Regulation of Digestion Gastrointestinal activities are coordinated by the nervous system and endocrine system. Stomach secretions are regulated by food and gastrin. The passage of chyme into the duodenum inhibits stomach contractions. Duodenum secretes other hormones that inhibit stomach emptying and promote bile release and bicarbonate secretion. enterogastrones

Hormonal Control of Gastrointestinal Tract

Accessory Organs Liver regulatory functions Liver chemically modifies substances absorbed in the gastrointestinal tract before they reach the rest of the body. also removes toxins and poisons, and converts them into less toxic forms Liver regulates many compounds such as steroid hormones, and produces most proteins found in blood plasma.

Regulation of Blood Glucose Concentration After a carbohydrate-rich meal, the liver and skeletal muscles remove excess glucose from blood and store it as glycogen. stimulated by insulin When glucose levels decrease, the liver secretes glucose in the blood. breakdown of glycogen gluconeogenesis - process of converting other molecules into glucose

Actions of Insulin and Glucagon

Glucose Feedback Loop Blood Glucose Blood Glucose Insulin Glucagon HIGH LOW Blood Glucose Blood Glucose pancreas secrete secrete Insulin Glucagon stimulates stimulates stimulates absorption liver release Glucose Glucose absorption Target tissue