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Digestion & Nutrition Chapter 41
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Overview: Food processing occurs in four stages
Small molecules Pieces of food Nutrient molecules enter body cells Chemical breakdown (enzymatic hydrolysis) Mechanical breakdown Undigested material Food 1 INGESTION 2 DIGESTION 3 ABSORPTION 4 ELIMINATION Figure 21.2
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Digestion occurs in specialized compartments
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
This is called a gastrovascular cavity Example: hydra Mouth Tentacle Hydrolytic enzymes Flagella Food particle Engulfment of food particle Food (Daphnia, a water flea) Gastro- vascular cavity Digestion in food vacuole Figure 21.3A
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In most animals, the digestive compartment is an alimentary canal
This is a tube running from mouth to anus This tube is divided into specialized regions that process food sequentially Crop Gizzard Esophagus Intestine Pharynx Anus Mouth EARTHWORM Wall of intestine Interior of intestine Figure 21.3B
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Esophagus Stomach Gizzard Anus Esophagus Stomach Intestine Gizzard Crop Intestine Mouth Gastric pouches GRASSHOPPER Mouth Crop Anus BIRD Figure 21.3B (cont)
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Ruminants such as cows process cellulose in a four-chambered stomach
Intestine 3 Omasum 1 Rumen Esophagus Rumen 2 4 Reticulum Abomasum Figure 21.12B
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Introductory Question #6
Name the four stages of food processing. (see pg. 853). From pg. 845, name the four types of feeders and the organism example shown. How are the alimentary canals different in an earthworm, grasshopper, a bird, and a cow (ruminant animal). Explain what peristalsis is and what causes it to occur. Name the cells that line the stomach which secrete HCl and pepsin. What are fols in the stomach called? What function do the villi serve in the lining of the intestines? Name the (3) segments of the small intestines and the (4) regions of the large intestines. How is an essential nutrient different from any other nutrient? (pg. 849) Give three examples of a fat-soluble and three examples of a water soluble vitamin.
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Humpback whales strain their food from seawater using large, brushlike plates called baleen
When they feed, they take in large amounts of seawater in which the fish and krill live They must filter out the water in order to get a meal
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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 They store the excess energy they harvest in the form of blubber In about 4 months, a humpback whale eats, digests, and stores as fat enough food for an entire year
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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 Figure 21.1A
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Most animals ingest chunks of food
Figure 21.1E
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Some animals are suspension feeders, consuming particles from water
Some are substrate feeders, living in or on their food source Figure 21.1B, C
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Some are fluid feeders, sucking liquids
Figure 21.1D
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Small intestine Small intestine Stomach Cecum Colon (large intestine) CARNIVORE HERBIVORE Figure 21.12A
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Oral cavity Mouth Tongue Pharynx Salivary glands Esophagus Liver Stomach Pyloric sphincter Stomach Gall- bladder Small intestine Pancreas Small intestine Large intestine Rectum Anus Figure 21.4
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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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The esophagus squeezes food along to the stomach
Peristalsis in the esophagus moves food boluses into the stomach Circular muscle layer Relaxed muscles Circular muscles contract, constricting passageway and pushing bolus down Relaxed muscles Bolus of food Longitudinal muscles contract, shortening passageway ahead of bolus Stomach Longitudinal muscle layer Figure 21.7
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The stomach stores food and breaks it down with acid and enzymes
The stomach mixes food with gastric juice The gastric juice contains pepsin, which begins the hydrolysis of protein
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Interior surface of stomach
Pits Gastric juice (mucus, HCI, and pepsinogen) Food particle 3 Epithelium Gastric juice Pepsinogen Pepsin (active enzyme) 2 Mucous cells HCI Pyloric sphincter Gastric gland 1 STOMACH Chief cells Parietal cells Figure 21.8
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Duodenum of small intestine Pancreas
Bile Liver Gall- bladder Stomach Bile Acid chyme Duodenum of small intestine Pancreas Figure 21.10A
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Enzymes from the walls of the small intestine complete the digestion of many nutrients
Table 21.10
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INTERIOR OF INTESTINE Blood vessel with blood en route to the liver Nutrient absorption Nutrient absorption Microvilli Epithelial cells Lumen Muscle layers Blood capillaries Circular folds Villi Lymph vessel EPITHELIAL CELLS Nutrient absorption INTESTINAL WALL VILLI Figure 21.10B
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Bacterial Infections can cause Ulcers
New evidence suggests that a spiral-shaped prokaryote causes gastric ulcers Helicobacter pylori growth erodes protective mucus and damages the stomach lining
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Large Intestine Reclaims Water
Undigested material passes to the large intestine, or colon Water is absorbed Feces are produced Large intestine (colon) End of small intestine Small intestine Rectum Anus Nutrient flow Appendix Cecum Figure 21.11
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Small intestine Small intestine Stomach Cecum Colon (large intestine) CARNIVORE HERBIVORE Figure 21.12A
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Video #5-Digestion & Fluid Balance (Ch. 41)
What organism is used by Dr. Carol Beuchat to illustrate how fluid is regulated and the role played by the urinary tract in maintaining homeostasis? (1st segment) How is a complete digestive system different from an incomplete one? What function does each segment (region) of the digestive system have? Name two enzymes mentioned by Dr. Sokolowski that play a role in the digestive system. How is the diet of a dog different from a cat? What are the nutritional needs for a cat and dog? What is the name of the café mentioned in the video? The final segment discusses the role the kidneys play in maintaining homeostasis. What kind of machine is the patient connected to? **Write the title for each segment and FIVE statements for each segment.
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Digestion begins in the oral cavity
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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TEETH Incisors Canine Premolars Molars “Wisdom” tooth Tongue Salivary glands Opening of a salivary gland duct Figure 21.5
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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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Bolus of food Tongue Epiglottis up Epiglottis down Pharynx Larynx Esophageal sphincter Larynx up Larynx down Trachea (windpipe) Esophagus Esophagus Sphincter contracted Sphincter relaxed Sphincter contracted Figure 21.6
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The small intestine is the major organ of chemical digestion and nutrient absorption
Alkaline pancreatic juice neutralizes stomach acids 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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Nutrients pass through the epithelium of the villi and into the blood
The lining of the small intestine is folded and covered with tiny, fingerlike villi Villi increase the absorptive surface 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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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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Some mammals house cellulose-digesting microbes in the colon or cecum
The cecum is a pouch where the large and small intestines connect Examples: horses and elephants Other mammals re-ingest their feces to recover nutrients Examples: rabbits and some rodents
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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
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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The energy a resting animal requires each day to stay alive is its basal metabolic rate (BMR)
Figure 21.14
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More energy is required for an active life
Excess energy is stored as glycogen or fat Table 21.14
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Body Fat and Fad Diets 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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Fad diets are often ineffective and can be harmful
Table 21.15
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A healthful diet includes 13 vitamins
Most of these vitamins function as coenzymes
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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
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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 ESSENTIAL AMINO ACIDS Methionine Valine (Histidine) Threonine Phenylalanine Corn Leucine Isoleucine Beans and other legumes Tryptophan Lysine Figure 21.16
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Table 21.17 (Fat-soluble vitamins)
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Table 21.17 (Water-soluble vitamins)
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Table 21.18
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What do food labels tell us?
Food labels provide important nutritional information about packaged foods Figure 21.19
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Diet can influence cardiovascular disease and cancer
Choice of diet may reduce the risk of cardiovascular disease and cancer BEHAVIORAL RISK FACTORS UNAVOIDABLE RISK FACTORS Fatty diet High blood cholesterol High blood pressure Aging Lack of exercise Family history CARDIOVASCULAR DISEASE Smoking Being male Figure 21.20
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Table 21.20
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Duodenum of small intestine Pancreas
Bile Liver Gall- bladder Stomach Bile Acid chyme Duodenum of small intestine Pancreas Figure 21.10A
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Video#6: Laparoscopic Cholecystectomy
*Write 10 Statements from the video
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A sound diet supplies enough raw materials to make all the macromolecules we need the proper amounts of prefabricated essential nutrients enough kilocalories to satisfy our energy needs
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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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