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Chapter 21 Nutrition & Digestion. Overview: Obtaining and processing food Human Digestive System Diets Nutrition. Getting Their Fill of Krill. Animals obtain and process nutrients in a variety of ways Humpback whales eat small fishes and crustaceans called krill

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Chapter 21 nutrition digestion l.jpg

Chapter 21Nutrition & Digestion

Overview:

Obtaining and processing food

Human Digestive System

Diets

Nutrition


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Getting Their Fill of Krill

  • Animals obtain and process nutrients in a variety of ways

  • Humpback whales eat small fishes and crustaceans called krill

    • This painting shows how the whales corral their food using “bubble nets”


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  • Humpback whales strain their food from seawater using large, brushlike plates called baleen


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  • In a typical day, a humpback whale’s digestive system will process as much as 2 tons of fish and krill


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OBTAINING AND PROCESSING FOOD blubber

Animals ingest their food in a variety of ways

  • Animal diets are highly varied

    • Herbivores are plant-eaters

    • Carnivores are meat-eaters

    • Omnivores eat both plants and other animals


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  • Ingest both plants and animals


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  • Herbivores

  • Feed mainly on plants


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  • Carnivores



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The Four Stages of Food Processing from water

  • Is another word for eating

  • Digestion

    • Is the breakdown of food to small molecules

    • Ingestion

    • Absorption

    • Is the uptake of the small nutrient molecules by the body’s cells

  • Elimination

    • Is the disposal of undigested materials from the food we eat


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    Digestion: A Closer Look from water

    • Begins the process

    • Involves physical processes like chewing

    • Mechanical digestion

    • Chemical digestion

    • Is the breakdown of food by digestive enzymes


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    • Chemical digestion

    • Hydrolases

    • Are enzymes that catalyze digestive hydrolysis reactions


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    Digestive Compartments from water

    • In animals, chemical digestion is contained safely within some kind of compartment

    • Food is digested in compartments housing hydrolytic enzymes

    • Most animals have a specialized digestive tract


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    • Relatively simple animals have a sac with a single opening


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    • In most animals, the digestive compartment is an alimentary canal


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    HUMAN DIGESTIVE SYSTEM from water

    The human digestive system consists of an alimentary canal and accessory glands

    • When food is swallowed, it is moved through the alimentary canal by peristalsis

      • Peristalsis is rhythmic muscle contraction in the walls of the digestive tract

      • Ringlike sphincter muscles regulate the passage of food


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    Digestion begins in the oral cavity from water

    • The teeth break up food

    • Saliva moistens it

    • Salivary enzymes begin the hydrolysis of starch

    • The tongue pushes the chewed food into the pharynx


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    The Pharynx from water

    • Connects the mouth to the esophagus

    • Also opens to the trachea

    • The pharynx

    The food and breathing passages both open into the pharynx

    • The swallowing reflex moves food from the pharynx into the esophagus

      • At the same time, food is kept out of the trachea



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    The Esophagus windpipe entrance

    • Is a muscular tube

    • Connects the pharynx to the stomach

    • Moves food down by peristalsis

    • The esophagus

    • Peristalsis in the esophagus moves food boluses into the stomach


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    The Stomach windpipe entrance

    • Can store food for several hours

    • Churns food

    • Mixes food with gastric juices, which are acidic

    • The stomach

    • The stomach mixes food with gastric juice

      • The gastric juice contains pepsin, which begins the hydrolysis of protein


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    Connection: Bacterial infections can cause ulcers windpipe entrance

    • New evidence suggests that a spiral-shaped prokaryote causes gastric ulcers

      • Helicobacter pylori growth erodes protective mucus and damages the stomach lining

    • Are erosions of the stomach lining


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    The Small Intestine windpipe entrance

    • Is the longest part of the alimentary canal

    • Is the major organ for chemical digestion and absorption

    • The small intestine

    Chemical Digestion in the Small Intestine

    • In the small intestine, hydrolases break down food to monomers


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    • Alkaline pancreatic juice neutralizes stomach acids windpipe entrance

      • Its enzymes digest polysaccharides, proteins, nucleic acids, and fats

    • Bile emulsifies fat droplets for attack by pancreatic enzymes

      • It is made in the liver and stored in the gall bladder



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    • The lining of the small intestine is folded and covered with tiny, fingerlike villi

    • Contains villi and microvilli

    • Has a large surface area for absorption

    • Nutrients pass through the epithelium of the villi and into the blood

      • The blood flows to the liver

      • The liver can store nutrients and convert them to other substances the body can use


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    Absorption of Nutrients digestion of many nutrients

    • It is not technically “in” the body yet

    • It must be absorbed

    • Although food has been ingested


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    • The duodenum

    • The pancreas

    • Secretes juice that neutralizes stomach acids

  • The liver

    • Secretes bile, which helps digest fats


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    • The jejunum and ileum


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    The Large Intestine (and Beyond) digestion of many nutrients

    • Is shorter, but wider, than the small intestine

    • The large intestine

    • The colon

    • Makes up most of the length of the large intestine

    • Absorbs water from the alimentary canal

    • Produces feces, the waste product of food

    • The rectum

    • Is the last 15 cm (6 inches) of the large intestine

  • The anus

    • Regulates the opening of the rectum


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    The large intestine reclaims water digestion of many nutrients

    • Undigested material passes to the large intestine, or colon

      • Water is absorbed

      • Feces are produced


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    DIETS AND DIGESTIVE ADAPTATIONS digestion of many nutrients

    Adaptations of vertebrate digestive systems reflect diet

    • Herbivores and omnivores generally have longer alimentary canals than carnivores

      • Plant matter is more difficult to digest than meat

      • Nutrients in vegetation are less concentrated than in meat


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  • Other mammals re-ingest their feces to recover nutrients

    • Examples: rabbits and some rodents

    • Some mammals house cellulose-digesting microbes in the colon or cecum


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    NUTRITION connect

    Overview: A healthful diet satisfies three needs

    • An animal’s diet provides

      • fuel for its activities

      • raw materials for making the body’s own molecules

      • essential nutrients that the body cannot make


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    Chemical energy powers the body connect

    • Once nutrients are inside cells, they can be oxidized by cellular metabolism to generate energy

      • This energy is in the form of ATP


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    Calories connect

    • A measure of the energy stored in your food

    • A measure of the energy you expend in daily activities

    • Calories are

    • A calorie is

    • The amount of energy required to raise the temperature of a gram of water by 1ºC

  • A kilocalorie is

    • One thousand calories

    • The unit listed on food labels



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    Metabolic Rate is its basal metabolic rate (BMR)

    • The metabolic rate of an organism is the rate of energy consumption per day


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    • Excess energy is stored as glycogen or fat


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    Connection: Body fat and fad diets is its basal metabolic rate (BMR)

    • The human body tends to store excess fat molecules instead of using them for fuel

    • A balanced diet includes adequate amounts of all nutrients


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    Connection: Vegetarians must be sure to obtain all eight essential amino acids

    • The eight essential amino acids that adults require must be obtained from food

      • They are easily obtained from animal protein

      • They can also be obtained from the proper combination of plant foods


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    Connection: A healthful diet includes 13 vitamins essential amino acids

    • Most of these vitamins function as coenzymes

    • Vitamins

    • Are organic molecules required in the diet for good health

    • Mostly function as assistants to enzymes


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    Connection: Essential minerals are required for many body functions

    • Minerals are elements other than carbon, hydrogen, oxygen, and nitrogen

      • They play a variety of roles in the body

    • Are inorganic substances required in the diet


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    Connection: What do food labels tell us? functions

    • Food labels provide important nutritional information about packaged foods


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    NUTRITIONAL DISORDERS functions

    • Nutritional dysfunction can cause severe problems


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    Malnutrition functions

    • Malnutrition is a dietary deficiency of one or more of the essential nutrients

    • Protein deficiency is an example

    • Undernutrition

    • Is caused by inadequate intake of nutrients


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    Obesity functions

    • Is an inappropriately high ratio of weight to height

    • Obesity



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    Connection: Diet can influence cardiovascular disease and cancer

    • Choice of diet may reduce the risk of cardiovascular disease and cancer


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    • A sound diet supplies


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