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week1chap3.pptxChapter 3 The Human Body: From Food to Fuel
Taste and Smell: The Beginnings of Our Food Experience
Sight, smell, thought, taste, and sound
Trigger a set of responses that prepare the digestive tract to receive food
The Gastrointestinal Tract
Variety of functions, including:
Ingestion of food
Transport of ingested food
Secretion of digestive enzymes, acid, mucus, and bile
Absorption of end products of digestion
Movement of undigested material
Elimination of digestive waste products
The Gastrointestinal Tract
Several layers to the GI tract, including
Mucosa
Circular muscle
Longitudinal muscle
Sphincters
Overview of Digestion
Physical movement
Peristalsis
Wavelike, muscular contractions
Transport food and nutrients along the GI tract
Segmentation
Series of muscular contractions in the small intestines
Divides and mixes the chyme
Chemical breakdown
Enzymes
Proteins that catalyze chemical reactions
Other secretions
Acid
Base
Bile
Mucus
Overview of Digestion
Overview of Absorption
The road to nutrition absorption
Passive diffusion
Facilitated diffusion
Active transport
Assisting Organs
Salivary glands
Moisten food
Supply enzymes
Assisting Organs
Liver
Produces bile
“Chemical factory”
“Dynamic warehouse”
Assisting Organs
Gallbladder
Stores and secretes bile
Pancreas
Secretes bicarbonate
Secretes digestive enzymes
Putting it All Together: Digestion and Absorption
Mouth
Enzymes
Salivary amylase acts on starch
Lingual lipase acts on fat
Saliva
Moistens food for swallowing
Putting it All Together: Digestion and Absorption
Esophagus
Transports food to stomach
Esophageal sphincter
Putting it All Together: Digestion and Absorption
Stomach
Hydrochloric acid prepares protein for digestion and activates enzymes
Pepsin begins protein digestion
Gastric lipase has some fat digestion
Gastrin (hormone) stimulates gastric secretion and movement
Intrinsic factor is needed for absorption of vitamin B12
Putting it All Together: Digestion and Absorption
Small intestine
Sections of small intestine
Duodenum, jejunum, and ileum
Nutrient digestion
Bicarbonate neutralizes stomach acid
Pancreatic and intestinal enzymes
Carbohydrates
Fat
Protein
Putting it All Together: Digestion and Absorption
Small intestine
Absorption
Folds, villi, and microvilli expand absorptive surface
Most nutrients absorbed here
Fat-soluble nutrients go into lymph
Other nutrients go into blood
Putting it All Together: Digestion and Absorption
Large intestine
Sections
Cecum, colon, rectum, anal canal
Digestion
Peristaltic movement is slow, taking 18–24 hours for material to travel
Some digestion of fiber by bacteria
Putting it All Together: Digestion and Absorption
Large Intestine
Absorption
Water
Sodium, potassium, and chloride
Vitamin K (produced by bacteria)
Elimination
Circulation of Nutrients
Vascular system
Veins and arteries
Carries oxygen and nutrients to tissues
Removes wastes
Lymphatic system
Vessels that drain lymph
Empties into the bloodstream near the neck
Circulation of Nutrients
Excretion and elimination
Lungs
Excrete water and carbon dioxide
Kidneys filter blood
Excrete waste; maintain water and ion balance
Signaling Systems: Command, Control, and Defense
Nervous system
Regulates GI activity
Enteric nervous system
Autonomic nervous system
Hormonal system
Increases or decreases GI motility and secretions
Influence your appetite
Signaling Systems: Command, Control, and Defense
Immune system
Protects us from foreign invaders
Role of GI tract
Barrier
Immune response
Natural killer cells
Macrophages
Location of lymphoid tissues
Lymphocytes
Antibodies
Influences on Digestion and Absorption
Psychological influences
Taste, smell, and presentation of food
Chemical influences
Type of protein you eat and the way it is prepared
Bacterial influences
Hydrochloric acid kills most bacteria
Nutrition and GI Disorders
Constipation
Hard, dry, infrequent stools
Reduced by high fiber, fluid intake, exercise
Diarrhea
Loose, watery, frequent stools
Symptom of diseases/infections
Can cause dehydration
Broth, tea, toast, and other low-fiber foods can help reduce
Nutrition and GI Disorders
Diverticulosis
Pouches along colon
High-fiber diet reduces formation
Heartburn and GERD
Reduced by smaller meals, less fat
Smoking weakens the esophageal sphincter
Being overweight often worsens symptoms
Nutrition and GI Disorders
Irritable bowel syndrome
Causes abdominal pain, diarrhea or constipation, and cramps
Stress and certain foods aggravate the symptoms
Can usually be controlled by diet and lifestyle modifications
Stress management
Nutrition and GI Disorders
Colorectal cancer
Fiber-rich diet may reduce risk
Gas
Most foods that contain carbohydrates can cause
Ulcers
Pain in the upper abdomen
Can cause nausea, vomiting, loss of appetite, and weight loss
Bacterial cause (H. pylori)
Nutrition and GI Disorders
Functional dyspepsia
Chronic pain in the upper abdomen
Treat with medicine and stress reduction
