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Digestion & Absorption
HLTH 120 N: Lecture 3
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Objectives Distinguish between appetite and hunger
Identify differences between digestion & absorption Know the GI organs & how they contribute to digestion, absorption and elimination Know key enzymes & their role in digestion Identify major hormones involved in GI regulation Describe the 4 types of absorption Explain the structural characteristics of and function of the small intestines lining Recognize GI diseases & disorders covered in class
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What’s the Difference? Hunger Appetite
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How is hunger regulated?
The _____________ is signaled by nerve cells and hormones that respond to organs Nerve cells Hunger hormones Respond to blood sugar: ____________________ Give feelings of satiety: leptin, CCK, serotonin Satiety
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The fate of food Digestion: Absorption:
Elimination: undigested food & waste are excreted
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Digestion starts in the mouth
Chewing is Saliva begins Amylase - Bicarbonate neutralizes acids Food travels as down the ___________ through ____________ (waves of muscular contraction) Released to the by the esophageal sphincter
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The stomach Here food is mixed, digested & stored
Gastric glands secrete gastric juices HCL: Pepsin: Gastric Lipase: Mucous: Intrinsic Factor: binds to B12 Absorbed: Food is mixed into chyme which is stored until release by the pyloric sphincter
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Intestines Small Intestine Large Intestine
3 sections- Duodenum, Jejunum, Ileum Further breakdown of nutrients Main role: Large Intestine Stores waste ( , toxins, bacteria & water) for excretion
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Enzymes break food into molecules
Chemical Digestion Enzymes break food into molecules Digestive Enzymes Produced in the GI tract Organ Enzyme Action Mouth Salivary Amylase Stomach Pepsin Gastric Lipase Pancreas Proteases Pancreatic lipase Pancreatic amylase Small Intestine (enzymes discussed in lecture 4) Lipase Sucrase Maltase Lactase Digests sucrose Digests maltose Digests lactose
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Chemical Digestion Hormones are messengers that send signals to help regulate digestion They bind to proteins on specific cells to signal a cascade of events
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Small Intestine Main function is _____________
Large surface area due to its lining: Villi are are absorptive cells lining the villi Lined with projections called Capillaries and a lacteal are inside each villus The brush border is composed of microvilli, which greatly increase the surface area
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Absorption Passive Diffusion: Facilitated Diffusion: Active Transport:
Endocytosis: nutrient is engulfed by the cell membrane Blood: carries most nutrients Lymph: carrise most lipids & fat soluble vitamins
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Absorption Pathways
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Accessory Organs Pancreas Liver Gallbladder Produces bicarbonate to…
Secretes amylase, lipase & proteases Secretes insulin & glucagon Liver Synthesizes chemicals like bile, aiding fat digestion Receives products from the portal vein for storage Blood functions: releases nutrients to blood & filters Gallbladder CCK signals release of bile into duodenum
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GI Disorders Neuromuscular dysfunction, allergies & intolerances, hormonal imbalance Belching & Flatulance
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Heartburn & GERD Heartburn Treatment GERD: painful, chronic heartburn
Excessive HCl Gastroesophogeal sphincter opens too soon Treatment OTC antacids Swallowing food/air GERD: painful, chronic heartburn Over-relaxed or damaged sphincter
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Ulcers Peptic ulcers: leroded by HCL & pepsin
Most common from: helicobacter pylori Less common: NSAIDS
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Food reactions Food Intolerance: Food Allergy: Celiac Disease:
Hypersensitivity reaction of the immune system Reactions: Celiac Disease: Inability to process ___________, causing destruction of intestinal villi & malnutrition Eliminate wheat, barley, rye
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Inflammatory Disorders
Crohn’s Disease Diarrhea, abdominal pain, rectal bleeding, malnutrition & weight loss How can this impact a child? Treated with medication, nutrition, surgery Ulcerative Colitis Similar to crohn’s disease Limited to the colon’s inner lining
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Functional Disorders Diarrhea Constipation
Acute if lasting less than ____________ Chronic has many causes Treat immediately to avoid dehydration Constipation Absence of bowel movement for longer than normal Nervous System, change in schedule/diet/meds Irritable Bowel Syndrome (IBS) Cramps, bloating, diarrhea and/or constipation Certain foods, interrupted signaling, immunity, etc.
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Diet Analysis Project: Part 1
Log your food/beverage intake and physical activity for 3 days 2 week days 1 weekend day Be accurate and specific I will not be judging your intake! You will be graded on completion of the entire project at the end of the semester
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