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The Digestive The Digestive SystemSystem
The Digestive System and Body The Digestive System and Body MetabolismMetabolism
Slide 14.1
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Digestion
Breakdown of ingested food
Absorption Passage of nutrients into the blood
Metabolism Production of cellular energy (ATP)
Organs of the Digestive SystemOrgans of the Digestive System
Slide 14.2a
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Two main groups
Alimentary canal – continuous coiled hollow tube
Accessory digestive organs
How is food digested?How is food digested?
Digestion involves:Digestion involves:
Breaking down of food into smaller Breaking down of food into smaller piecespieces
The mixing of foodThe mixing of food Movement through the digestive tractMovement through the digestive tract Chemical breakdown of the large Chemical breakdown of the large molecules of food into smaller molecules of food into smaller molecules. molecules.
Digestive SystemDigestive System
The digestive tract is a series of The digestive tract is a series of hollow organs joined in a tube from hollow organs joined in a tube from the mouth to the anus. Food passes the mouth to the anus. Food passes through the digestive tract.through the digestive tract.
Accessory organs include the liver, Accessory organs include the liver, gall bladder, and pancreas. Food gall bladder, and pancreas. Food does not pass through these organs.does not pass through these organs.
Organs of the Digestive SystemOrgans of the Digestive System
Slide 14.2b
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 14.1
Organs of the Alimentary CanalOrgans of the Alimentary Canal
Slide 14.3
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Mouth
Pharynx
Esophagus
Stomach
Small intestine
Large intestine
Anus
MouthMouth
Teeth bite off and chew food into a Teeth bite off and chew food into a soft pulp that is easy to swallow. soft pulp that is easy to swallow.
Chewing mixes the food with saliva, Chewing mixes the food with saliva, from salivary glands around the from salivary glands around the mouth and face, to make it moist and mouth and face, to make it moist and easy to swallow.easy to swallow.
Enzymes in the saliva begin Enzymes in the saliva begin digestion of carbohydrates.digestion of carbohydrates.
PharynxPharynx
Slide 14.9
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Serves as a passageway for air and food
Food is propelled to the esophagus by two muscle layers Longitudinal inner layer
Circular outer layer
Food movement is by alternating contractions of the muscle layers (peristalsis)
EsophagusEsophagus
The esophagus is a muscular The esophagus is a muscular tube. It takes food from the tube. It takes food from the throat and pushes it down throat and pushes it down through the neck, and into the through the neck, and into the stomach. stomach.
It moves food by waves of muscle It moves food by waves of muscle contraction called peristalsis.contraction called peristalsis.
EsophagusEsophagus
Slide 14.10
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Runs from pharynx to stomach through the diaphragm
Conducts food by peristalsis (slow rhythmic squeezing)
Passageway for food only (respiratory system branches off after the pharynx)
Stomach FunctionsStomach Functions
Slide 14.18
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Acts as a storage tank for food
Site of food breakdown
Chemical breakdown of protein begins
Delivers chyme (processed food) to the small intestine
Stomach AnatomyStomach Anatomy
Slide 14.17
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 14.4a
Small IntestineSmall Intestine
Slide 14.21
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
The body’s major digestive organ
Site of nutrient absorption into the blood
Muscular tube extending form the pyloric sphincter to the ileocecal valve
Suspended from the posterior abdominal wall by the mesentery
Subdivisions of the Small IntestineSubdivisions of the Small Intestine
““Dogs Just Itch!Dogs Just Itch!
Slide 14.22
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Duodenum Attached to the stomach
Curves around the head of the pancreas
Jejunum Attaches anteriorly to the duodenum
Ileum Extends from jejunum to large intestine
Chemical Digestion in the Small Chemical Digestion in the Small IntestineIntestine
Slide 14.23a
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Source of enzymes that are mixed with chyme
Intestinal cells
Pancreas
Bile enters from the gall bladder
Villi of the Small IntestineVilli of the Small Intestine
Slide 14.24
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Fingerlike structures formed by the mucosa
Give the small intestine more surface area
Figure 14.7a
Microvilli of the Small IntestineMicrovilli of the Small Intestine
Slide 14.25
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Small projections of the plasma membrane
Found on absorptive cells
Figure 14.7c
Structures Involved in Structures Involved in Absorption of NutrientsAbsorption of Nutrients
Slide 14.26
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Absorptive cells
Blood capillaries
Lacteals (specialized lymphatic capillaries)
Figure 14.7b
Digestion in the Small IntestineDigestion in the Small Intestine
Slide 14.57a
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Enzymes from the brush border Break double sugars into simple sugars
Complete some protein digestion
Pancreatic enzymes play the major digestive function Help complete digestion of starch
(pancreatic amylase)
Carry out about half of all protein digestion (trypsin, etc.)
Digestion in the Small IntestineDigestion in the Small Intestine
Slide 14.57bCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Pancreatic enzymes play the major digestive function (continued)
Responsible for fat digestion (lipase)
Digest nucleic acids (nucleases)
Alkaline content neutralizes acidic chyme
Absorption in the Small IntestineAbsorption in the Small Intestine
Slide 14.59Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Water is absorbed along the length of the small intestine
End products of digestion
Most substances are absorbed by active transport through cell membranes
Lipids are absorbed by diffusion
Substances are transported to the liver by the hepatic portal vein or lymph
Small IntenstineSmall Intenstine This part of the digestive tract is This part of the digestive tract is narrow, but very long - about 20 feet. narrow, but very long - about 20 feet.
Enzymes continue the chemical reactions on Enzymes continue the chemical reactions on the food. the food.
The nutrients are broken down small enough The nutrients are broken down small enough to pass through the lining of the small to pass through the lining of the small intestine, and into the blood (diffusion). intestine, and into the blood (diffusion).
Nutrients are carried away to the liver Nutrients are carried away to the liver and other body parts to be processed, and other body parts to be processed, stored and distributed.stored and distributed.
Large IntestineLarge Intestine
Slide 14.28
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Larger in diameter, but shorter than the small intestine
Frames the internal abdomen
Large IntestineLarge Intestine
Slide 14.28
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 14.8
Functions of the Large IntestineFunctions of the Large Intestine
Slide 14.29
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Useful substances that were not absorbed in the Useful substances that were not absorbed in the small intestine, such as spare water and body small intestine, such as spare water and body minerals, are absorbed through the walls of the minerals, are absorbed through the walls of the large intestine, back into the blood.large intestine, back into the blood.
Eliminates indigestible food from the body as feces
Does not participate in digestion of food
Food Breakdown and Food Breakdown and Absorption in the Large IntestineAbsorption in the Large Intestine
Slide 14.61
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
No digestive enzymes are produced
Resident bacteria digest remaining nutrients
Produce some vitamin K and B
Release gases
Water and vitamins K and B are absorbed
Identify and tell the Identify and tell the function of each part of function of each part of the digestive systemthe digestive system
Rectum and AnusRectum and Anus
The end of the large intestine The end of the large intestine and the next part of the tract, and the next part of the tract, the rectum, store the feces. the rectum, store the feces.
Feces are finally squeezed Feces are finally squeezed through a ring of muscle, the through a ring of muscle, the anus, and out of the body.anus, and out of the body.
PancreasPancreas
Slide 14.38
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Produces a wide spectrum of digestive enzymes that break down all categories of food
Enzymes are secreted into the duodenum
Alkaline fluid introduced with enzymes neutralizes acidic chyme
Endocrine products of pancreas
Insulin
Glucagons
Gall BladderGall Bladder A small baglike part under the liver.A small baglike part under the liver.
It stores a fluid called bile, which is It stores a fluid called bile, which is made in the liver. made in the liver.
As food from a meal enters the small As food from a meal enters the small intestine, bile flows from the gall intestine, bile flows from the gall bladder along the bile duct into the bladder along the bile duct into the intestine. intestine.
It helps to digest fatty foods and also It helps to digest fatty foods and also contains wastes for removal. contains wastes for removal.
LiverLiver
Slide 14.39
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Largest gland in the body
Located on the right side of the body under the diaphragm
Consists of four lobes suspended from the diaphragm and abdominal wall by the falciform ligament
LiverLiver
Blood from the intestines enters to the Blood from the intestines enters to the liver, carrying nutrients, vitamins and liver, carrying nutrients, vitamins and minerals, and other products from minerals, and other products from digestion.digestion.
The liver is like a food-processing The liver is like a food-processing factory with more than 200 different factory with more than 200 different jobs. It stores some nutrients, changes jobs. It stores some nutrients, changes them from one form to another, and them from one form to another, and releases them into the blood according releases them into the blood according to the activities and needs of the body.to the activities and needs of the body.
Role of the Liver in MetabolismRole of the Liver in Metabolism
Slide 14.77
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Several roles in digestion
Detoxifies drugs and alcohol
Degrades hormones
Produce cholesterol, blood proteins (albumin and clotting proteins)
Plays a central role in metabolism
BileBile
Slide 14.40
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Produced by cells in the liver
Composition Bile salts
Bile pigment (mostly bilirubin from the breakdown of hemoglobin)
Cholesterol
Phospholipids
Electrolytes
Processes of the Digestive SystemProcesses of the Digestive System
Slide 14.42a
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Ingestion – getting food into the mouth
Propulsion – moving foods from one region of the digestive system to another
Processes of the Digestive SystemProcesses of the Digestive System
Slide 14.42b
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Peristalsis – alternating waves of contraction
Segmentation – moving materials back and forth to aid in mixing
Figure 14.12
Processes of the Digestive SystemProcesses of the Digestive System
Slide 14.43
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Mechanical digestion Mixing of food in the mouth by the tongue
Churning of food in the stomach
Segmentation in the small intestine
Processes of the Digestive SystemProcesses of the Digestive System
Slide 14.44
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Chemical Digestion
Enzymes break down food molecules into their building blocks
Each major food group uses different enzymes
Carbohydrates are broken to simple sugars
Proteins are broken to amino acids
Fats are broken to fatty acids and alcohols
Processes of the Digestive SystemProcesses of the Digestive System
Slide 14.45
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Absorption
End products of digestion are absorbed in the blood or lymph
Food must enter mucosal cells and then into blood or lymph capillaries
Defecation
Elimination of indigestible substances as feces
Processes of the Digestive SystemProcesses of the Digestive System
Slide 14.46
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 14.11
Control of Digestive ActivityControl of Digestive Activity
Slide 14.47b
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Stimuli include: Stretch of the organ
pH of the contents
Presence of breakdown products
Reflexes include: Activation or inhibition of glandular
secretions
Smooth muscle activity
NutritionNutrition
Slide 14.63
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Nutrient – substance used by the body for growth, maintenance, and repair
Categories of nutrients
Carbohydrates: simple sugars, starches, fiber
Lipids: triglycerides, phospholipids, fatty acids
Proteins: amino acids
Vitamins
Mineral
Water
Body Energy BalanceBody Energy Balance
Slide 14.83
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Energy intake = total energy output (heat + work + energy storage)
Energy intake is liberated during food oxidation
Energy output
Heat is usually about 60%
Storage energy is in the form of fat or glycogen