Chapter3

Chemical, Biological, and Chemical, Biological, and Physiological Aspects of NutritionPhysiological Aspects of Nutrition

Chapter 3

How Does Chemistry Apply to How Does Chemistry Apply to the Study of Nutrition?the Study of Nutrition?

• Organization• Atoms simple molecules complex

molecules cells tissues organs organ systems

• Made of and fueled by nutrients in food

Levels of Organization in the Levels of Organization in the BodyBody


• Atoms• Protons

• Neutrons

• Electrons

• Ions• Cations

• Anions

• Important ions

Formation of Cations and AnionsFormation of Cations and Anions


• Reduction-oxidation (redox) reactions• Oxidation

• Loss of electrons

• Reduction• Gain of electrons


• Simple molecules • Elements – 20 essential for human health

• 6 elements account or 99% of total body weight

• Chemical bonds

• Compounds

• Molecular formulas

The Most Abundant Elements in The Most Abundant Elements in the Human Bodythe Human Body


• Complex molecules • Examples

• Assembly and disassembly• Condensation

• Hydrolysis

• Acid-base chemistry • pH scale

– Basic, neutral, acidic– Buffers

Condensation and HydrolysisCondensation and Hydrolysis

How Do Biological Molecules Form How Do Biological Molecules Form Cells, Tissues, Organs, & Organ Cells, Tissues, Organs, & Organ

Systems?Systems?

• Cells• Organelles, cytoplasm, Extracellular and

intracellular environments

• Cell membranes• Selectively permeable

• Transport mechanisms– Passive transport mechanisms– Active transport mechanisms


Systems?Systems?

• Passive transport mechanisms• Simple diffusion

• Facilitated diffusion • Membrane-bound transport proteins

• Osmosis • Solutes

Passive TransportPassive Transport


Systems?Systems?• Active transport

mechanisms• Carrier-mediated

active transport• Requires ATP &

transport proteins • Vesicular active

transport• Endocytosis• Exocytosis

Carrier-mediated active transport

Active TransportActive Transport

A Typical CellA Typical Cell


Systems?Systems?

• 4 types of tissues, 40 organs, 11 unique organ systems

• Tissues• Epithelial

• Connective

• Muscle• Smooth, cardiac, skeletal

• Neural

Four Basic Types of TissueFour Basic Types of Tissue


Systems?Systems?

• Organs • Two or more different types of tissues

• Organ system• Communication systems

• Nervous system– Neurotransmitters

• Endocrine system– Hormones

• Negative feedback systems

Organ Systems and Related Organ Systems and Related Major FunctionsMajor Functions

How Does the Digestive System How Does the Digestive System Break Down Food into Absorbable Break Down Food into Absorbable

Components?Components?

• Gastrointestinal tract• Hollow tube from mouth to anus

• Organs• Mouth, esophagus, stomach, small intestine, and

large intestine

• Accessory organs

• Three important functions• Digestion, absorption, and egestion

Organs of the Digestive SystemOrgans of the Digestive System



• Tissue layers • Mucosa

• Mainly epithelial cells

• GI secretions

• Lifespan

• Submucosa• Rich supply of blood vessels

• Lymphatic vessels

• Network of nerves

The Layers of the GI TractThe Layers of the GI Tract



• Tissue layers• Muscularis

• Two layers of smooth muscle– Longitudinal layer and circular layer

• Mixing of food mass with digestive secretions

• Serosa• Secretes fluid that lubricates digestive organs

How Do Gastrointestinal Motility and How Do Gastrointestinal Motility and Secretions Facilitate Digestion?Secretions Facilitate Digestion?

• Transit time• 24 to 72 hours

• Factors affecting transit time

• Sphincters• Named according to anatomical locations

Sphincters Regulate the Flow of Sphincters Regulate the Flow of FoodFood


• GI motility• Mixing and propulsion of material

• Muscular contractions

• Two types of movement• Segmentation

– Mixes and propels food

• Peristalsis – Vigorous propulsive movements

SegmentationSegmentation

PeristalsisPeristalsis


• GI secretions• Mucus

• Protective coating

• Digestive enzymes • Biological catalysts

• Organs that release digestive secretions

Summary of Major GI SecretionsSummary of Major GI Secretions


• Three regulatory control mechanisms• Neural

• Enteric nervous system – Sensory receptors: chemoreceptors &

mechanoreceptors

• Central nervous system

• Hormonal• GI hormones

– Influence desire to eat

The Major GI Hormones & Their The Major GI Hormones & Their Related FunctionsRelated Functions

How Does the GI Tract Coordinate How Does the GI Tract Coordinate Functions to Optimize Digestion & Functions to Optimize Digestion &

Nutrient Absorption?Nutrient Absorption?

• Three phases of digestion• Cephalic phase

• Before food enters mouth

• Gastric phase• Arrival of food in stomach

• Intestinal phase



• Digestion begins in the mouth• Mastication

• Saliva

• Taste sensation• Salty, sour, sweet, bitter, umami

• Olfactory and gustatory cells

• Swallowing • Phases

• Bolus

Voluntary & Involuntary Phases Voluntary & Involuntary Phases of Swallowingof Swallowing



• Esophagus• Delivers food to the stomach

• Dysphagia

• Gastroesophageal sphincter

• Transit time• Less than 10 seconds



• Stomach• Regions

• Fundus, body, and antrum

• Pyloric sphincter

• Storage• Rugae

• Mixing food with gastric secretions• Third layer of smooth muscle

• Chyme

Anatomy of the Stomach and Its Anatomy of the Stomach and Its Role in DigestionRole in Digestion



• Stomach• Gastric secretions

• Gastric pits– Endocrine and exocrine cells

• Gastrin

• Parietal cells

• Chief cells

• Gastric mucosal barrier



• Stomach• Peptic ulcers

• Types

• Helicobacter pylori (H. pylori)

• Symptoms

• Gastroesophageal reflux disease (GERD)• Gastroesophageal sphincter

• Symptoms

• Diagnosis

Peptic UlcersPeptic Ulcers

Gastroesophageal Reflux Gastroesophageal Reflux Disease (GERD)Disease (GERD)



• Regulation of gastric emptying• Influential factors

• Volume

• Consistency

• Composition of chyme

• Influence of small intestine• Cholecystokinin (CCK)


Nutrient Absorption?Nutrient Absorption?• Small intestine

• Chemical digestion and nutrient absorption• Regions

• Duodenum, jejunum, and ileum

• Lining of small intestine • Plica circulares • Villi

– Enterocytes• Microvilli • Lacteal

Overview of the SI and Overview of the SI and Accessory Organs Accessory Organs

Absorptive Surface of the Small Absorptive Surface of the Small IntestineIntestine



• Digestion in the small intestine• Regulated by hormones

• Secretin and CCK

• Pancreatic juice

• Bile• Produced in liver; stored in gallbladder

• Digestion of fatty foods

• Enterohepatic circulation

• Enzyme facilitation

The PancreasThe Pancreas

The Role of the Liver and The Role of the Liver and Gallbladder in DigestionGallbladder in Digestion



• Nutrient absorption• Passive and active transport mechanisms

• Stomach absorption

• Small intestine absorption• Entry into and exit from enterocyte

• Bioavailability • Influential factors

Nutrient Absorption and Nutrient Absorption and CirculationCirculation

How Does the Body Circulate How Does the Body Circulate Nutrients & Eliminate Cellular Waste Nutrients & Eliminate Cellular Waste

Products?Products?• Transport

• Circulatory system

• Absorption from small intestine• Water-soluble nutrients

• Circulate to liver in bloodstream


Products?Products?• Cardiovascular system

• Two loops

• Systemic circulation • Delivers blood to all the body’s organs except

lungs

• Capillaries • Exchange of materials, nutrients, and gases

• Arterial and venous vascular systems• Similarities and differences

Nutrient and Gas Exchange Nutrient and Gas Exchange across the Capillary Wallacross the Capillary Wall


Products?Products?• Cardiovascular system

• Pulmonary circulation • Circulation between the heart and lungs

• Pulmonary arteries and veins

Systemic and Pulmonary Systemic and Pulmonary CirculationCirculation


Products?Products?• Lymphatic system

• Circulates fat-soluble nutrients • Eventually delivers them to cardiovascular

system

• Route initially bypasses the liver


Products?Products?• Kidneys

• Cellular waste products

• Nephrons • Filtration

– Initially removes substances from the blood

• Reabsorption

• Causes of impaired kidney function • Hemodialysis

• Formation of urine

Overview of the Urinary SystemOverview of the Urinary System

What Is the Role of the Large What Is the Role of the Large Intestine?Intestine?

• Major functions• Absorption and reabsorption• Microbial action• Storage and elimination

• Four general regions• Cecum• Colon• Rectum• Anal canal

Overview of the Large Intestine Overview of the Large Intestine


• Cecum• Appendix

• Ileocecal sphincter

• Colon • Ascending, transverse, descending

• Anal canal• Internal and external anal sphincters


• Absorption and reabsorption• Haustral contractions

• Absorption• Some water and electrolytes

• Reabsorption • GI secretions

• Feces• Diarrhea and constipation


• Microbial action• Intestinal microbiota

• More than 400 species

• Important roles

• Probiotic and prebiotic foods

• Egestion • Defecate

Irritable Bowel Syndrome & Irritable Bowel Syndrome & Inflammatory Bowel DiseaseInflammatory Bowel Disease

• Inflammatory bowel disease (IBD)• Autoimmune disease

• Examples • Ulcerative colitis

• Crohn’s disease

• Irritable bowel syndrome (IBS)• Functional disorder

• Underlying cause has not been determined

Chapter3

Health & Medicine

Transcript of Chapter3