Essentials of Human Anatomy & Physiology

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Slides 14.1 – 14.14

Seventh Edition

Elaine N. Marieb

Chapter 14

The Digestive System and

Body Metabolism

Lecture Slides in PowerPoint by Jerry L. Cook

Organs of the Digestive System

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Two main groups

Alimentary canal – continuous coiled hollow tube

Accessory digestive organs

Organs of the Digestive System

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Figure 14.1

Organs of the Alimentary Canal

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Mouth

Pharynx

Esophagus

Stomach

Small intestine

Large intestine

Anus

Mouth (Oral Cavity) Anatomy

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Figure 14.2a

Mouth (Oral Cavity) Anatomy

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Figure 14.2a

Mouth (Oral Cavity) Anatomy

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Figure 14.2a

Processes of the Mouth

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Mastication (chewing) of food and mixing it with saliva

Initiation of swallowing by the tongue

Ingestion of food

Pharynx Anatomy

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Figure 14.2a

Pharynx Function

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Passageway for air and food

Food is propelled to the esophagus by alternating contractions of the muscle layers (peristalsis)

Esophagus

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Runs from pharynx to stomach through the diaphragm

Conducts food by peristalsis

Passageway for food only

Stomach Anatomy

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Figure 14.4a

Stomach Anatomy

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Cardiac region

Pylorus Body

Fundus

Stomach Functions

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storage tank for food

Site of food breakdown from churnning, mixing, and secreting enzymes

Delivers chyme (processed food) to the small intestine

Stomach Anatomy

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pyloric sphincter – place where food empties into the small intestine

Rugae – internal folds of the mucosa

Structure of the Stomach Mucosa

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Gastric pits formed by folded mucosa Mucous neck cells – produce a sticky alkaline

mucus

Gastric glands – secrete gastric juice

Chief cells – produce protein-digesting enzymes (pepsinogens)

Parietal cells – produce hydrochloric acid

Endocrine cells – produce gastrin

Structure of the Stomach Mucosa

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Figure 14.4b, c

Small Intestine

Characteristics

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Site of nutrient absorption into the blood

Muscular tube extending from the pyloric sphincter to the ileocecal valve

Suspended from the posterior abdominal wall by the mesentery

Subdivisions of the Small Intestine

Subdivisions of the Small Intestine

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Duodenum

Attached to the stomach

Curves around the head of the pancreas

Subdivisions of the Small Intestine

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Jejunum

Attaches anteriorly to the duodenum

Subdivisions of the Small Intestine

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Ileum

Extends from jejunum to large intestine

Chemical Digestion in the Small

Intestine

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Figure 14.6

Chemical Digestion in the Small

Intestine

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Intestinal cells and pancreas provide a source of enzymes that are mixed with chyme

Bile enters from the gall bladder

Villi of the Small Intestine

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Fingerlike structures formed by the mucosa

Figure 14.7a

Give the small intestine more surface area for absorption

Microvilli of the Small Intestine

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Small projections of the plasma membrane on absorptive cells to increase surface area even more

Figure 14.7c

Villi & Microvilli

Structures Involved in Absorption of

Nutrients

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Absorptive cells

Figure 14.7b

Blood capillaries

Lacteals (specialized lymphatic capillaries)

Large Intestine

Characteristics

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Larger in diameter, but shorter than the small intestine

Frames the internal abdomen

Large Intestine

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Figure 14.8

Functions of the Large Intestine

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Absorption of water

Eliminates indigestible food from the body as feces

Does not participate in digestion of food

Goblet cells produce mucus to act as a lubricant

Structures of the Large Intestine

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Cecum – saclike first part of the large intestine

Cecum

Structures of the Large Intestine

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Appendix

Accumulation of lymphatic tissue that sometimes becomes inflamed (appendicitis)

Appendicitis

Structures of the Large Intestine

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Colon

Ascending

Transverse

Descending

S-shaped sigmoidal

Colon

Structures of the Large Intestine

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Rectum – holds feces before expulsion

Anus – external body opening that expels feces

Accessory Digestive Organs

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Salivary glands

Teeth

Pancreas

Liver

Gall bladder

Salivary Glands

Salivary Glands

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Saliva-producing glands

Parotid glands

Submandibular glands

Sublingual glands

Saliva

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Mixture of mucus and serous fluids

Forms a food bolus

Amylase begins starch digestion

Dissolves chemicals so they can be tasted

Pancreas

Pancreas

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Alkaline fluid introduced with enzymes to neutralize acidic chyme into the duodenum

Endocrine products of pancreas are insulin and glucagon

Liver

Liver

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Largest gland in the body

Has four lobes

Connected to the gall bladder via the common hepatic duct

Produces Bile

Cirrhosis from Hepatitis B

Bile

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Produced by cells in the liver

Composition

Bile salts

Bile pigment (mostly bilirubin from the breakdown of hemoglobin)

Cholesterol

Phospholipids

Electrolytes

Gall Bladder

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Sac found in hollow fossa of liver

Stores bile from the liver, causes bile to be more concentrated, and is introduced into the duodenum in the presence of fatty food

Gallstones can cause blockages

Processes of the Digestive System

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Figure 14.11

Processes of the Digestive System

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Ingestion – getting food into the mouth

Propulsion – moving foods from one region of the system to another

Processes of the Digestive System

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Peristalsis – alternating waves of contraction

Figure 14.12

Segmentation – moving materials back and forth to aid in mixing

Processes of the Digestive System

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Mechanical digestion

Mixing of food in the mouth by the tongue and teeth

Churning of food in the stomach

Segmentation in the small intestine

Processes of the Digestive System

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Chemical Digestion

Each major food group uses different enzymes

Processes of the Digestive System

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Chemical Digestion

Carbs are broken down by amylase in mouth and small intestines

Carbohydrate Digestion

Processes of the Digestive System

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Chemical Digestion

Proteins are broken down in the stomach and the small intestine from proteases such as pepsin

Protein Digestion

Processes of the Digestive System

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Chemical Digestion

Fats are broken down by lipases from bile made in the liver

Fat Digestion

Processes of the Digestive System

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AbsorptionFood must enter mucosal cells of small

intestine and then into blood or lymph capillaries

Large intestine absorbs water

DefecationElimination of indigestible substances as

feces

Processes of the Digestive System

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Figure 14.11

Scrubs

Song!

Nutrition

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Nutrient – substance used by the body for growth, maintenance, and repair

Categories of nutrients

Carbohydrates

Lipids

Proteins

Vitamins

Mineral

Water

Slide 14.64Dietary Sources of Major Nutrients

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Carbohydrates

Derived from plants

Exceptions: lactose from milk and small amounts of glycogens from meats

Primary function is to provide energy

Dietary Sources of Major Nutrients

Lipids

Saturated fats from animal products

Unsaturated fats from nuts, seeds, and vegetable oils

Cholesterol from egg yolk, meats, and milk products

Primary function is cushioning and protecting internal organs

Dietary Sources of Major Nutrients

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Proteins

Most are from animal products

Legumes and beans also have proteins, but are incomplete

Primary function is providing structure and support in the body

Dietary Sources of Major

Nutrients Vitamins

Most vitamins are used as cofactors and act with enzymes

Found in all major food groups

Dietary Sources of Major Nutrients

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Minerals

Play many roles in the body

Most mineral-rich foods are vegetables, legumes, milk, and some meats

Dietary Sources of Major Nutrients

• Water

• Primary function

is to be a

dissolving

medium for

chemical

reactions

The Food Pyramid

Cholesterol Metabolism

Cholesterol Metabolism

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Structural basis of steroid hormones and vitamin D

Is a major building block of plasma membranes

Most cholesterol is produced in the liver and is not from diet

CHOLESTEROL

Cholesterol Transport

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They are transported by lipoproteins (lipid-protein complexes)

Low-density lipoproteins (LDLs) transport to body cells and sticks to artery walls and contributes to plaque build-up

High-density lipoproteins (HDLs) transport LDL from body cells to the liver

Ways to Increase HDL

Body Energy Balance

Regulation of Food Intake

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Body weight is relatively stable if energy intake and output remain equal

Mechanisms that may regulate food intakeLevels of nutrients in the blood

Hormones

Body temperature

Psychological factors

Metabolic Rate and Body Heat

Production

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Basal metabolic rate (BMR) – amount of heat produced by the body per unit of time at rest

Metabolic Rate and Body Heat

Production

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Factors that influence BMR Surface area – small body usually has higher

BMR

Gender – males tend to have higher BMR

Age – children and adolescents have a higher BMR

Hormones - thyroxine