Transcript chemical digestion

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
 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
 Body fluids
 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
 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
 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
 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
 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
 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
 Glycogen
 Fat cells – fat and fat-related substances
 Variations in nutrient stores