Chapter 3 The Remarkable Body Nutrition: Concepts & Controversies, 12e Sizer/Whitney

Learning Objectives Describe the levels of organization in the body, and identify some basic ways in which nutrition supports them. Compare the terms mechanical digestion and chemical digestion, and point out where these processes occur along the digestive tract. Trace the breakdown and absorption of carbohydrate, fat, and protein from the mouth to the colon.

The Body’s Cells Body is composed of trillions of cells Body needs nutrients Cells are self-contained, living entities Depend on one another Basic needs Essential nutrients Cells die at varying rates

A Cell (Simplified Diagram)

The Body’s Cells Genes Tissues, organs, and body systems Control function Direct production of proteins Provide instruction for structural components of cells Affects how body handles nutrients Complete set of genes in each cell Tissues, organs, and body systems

From DNA to Living Cells

The Body Fluids and the Cardiovascular System Supply energy, oxygen, nutrients, and water Deliver fresh supplies and pick up wastes Types of fluids Blood Arteries, veins, capillaries Plasma Lymph

Blood Flow in the Cardiovascular System

The Body Fluids and the Cardiovascular System Extracellular fluid Intracellular fluid All cell reactions take place Holds cellular shape

The Body Fluids and the Cardiovascular System All blood circulates to the lungs Picks up oxygen Releases carbon dioxide

The Body Fluids and the Cardiovascular System Blood returns to heart Blood pumped to rest of body Delivers nutrients Picks up wastes Blood passes through digestive system Picks up nutrients Except for fats Fats travel via lymph Routed directly to liver

Lymph Vessels and the Bloodstream

The Body Fluids and the Cardiovascular System Kidneys Fluid intake Red blood cell life expectancy Blood is sensitive to malnutrition

The Hormonal and Nervous System Hormones Chemical messengers Secreted and released directly into blood by glands Stimulate organs to take action Glands monitor conditions in the body Pancreas Insulin and glucagon

The Hormonal and Nervous System Nutrition affects the hormonal system Hormones affect nutrition Appetite changes during pregnancy Nervous system Receives and integrates information from sensory receptors Role in hunger regulation Cortex and hypothalamus

Cutaway Side View of the Brain Showing the Hypothalamus & Cortex

The Hormonal and Nervous System Fight-or-flight reaction (stress response) Neurotransmitters Epinephrine and norepinephrine Metabolism speeds up Organ response Eyes, heart, liver, stomach Heart disease

The Immune System Cooperation among tissues to maintain defenses Physical barriers Antigen Immune defenses White blood cells Phagocytes Lymphocytes (T-cells and B-cells)

The Immune System Inflammation Response to injury or irritation Increased white blood cells, redness, heat, pain, swelling Normal and healthy response Problem with chronic inflammation Dietary factors

The Digestive System Four basic chemical tastes Sweet, sour, bitter, and salty Savory Sweet, salty, and fatty foods Almost universally desired Can lead to drastic overeating of these substances

The Digestive System Digestive tract Flexible, muscular tube Path Total length of about 26 feet Body surrounds digestive canal System’s job is to digest food to its components, absorb, and excrete System works at two levels

The Digestive System

The Digestive System Chemical digestion Digestive juices Mouth Stomach Salivary glands, stomach, pancreas, liver, and small intestine Mouth Saliva – starches and fat Saliva – health of teeth Stomach Hydrochloric acid – protein

The Digestive System Chemical digestion Intestine Bile Pancreatic juice Digestive enzymes in wall of intestine Fiber Food combinations and digestion

The Digestive System Within 24 to 48 hours Mouth 90% of carbs, fat, and protein are digested and absorbed Mouth Food is crushed, mashed, and mixed with saliva Carbohydrate digestion begins Swallowing Peristalic waves

The Digestive System Stomach Small intestine Large intestine Gastric juice mixes with food Unwinds proteins Chyme Small intestine Bile from the liver Pancreas Large intestine

The Digestive System

The Digestive System Absorption Nutrient molecules transverse intestinal lining Water-soluble components Fat-soluble components Cells of small intestine are selective Folded structure Villi Microvilli

Details of the Small Intestine Lining

The Digestive System Transport Nourishment of digestive tract Lymph vessels Products of fat digestion Fat-soluble vitamins Blood vessels Products of carbohydrate & protein digestion Most vitamins Minerals Nourishment of digestive tract

The Excretory System Organs involved in waste removal Kidneys Lungs, liver, kidneys Kidneys Waste materials are dissolved in water Working units – nephrons Urine is stored in bladder Sodium and blood pressure Work regulated by hormones Importance of water supply

Storage Systems Eating intervals of 4-6 hours Major storage sites Liver – carbohydrates Glycogen Muscles – carbohydrates Fat cells – fat and fat-related substances Variations in nutrient stores