Human Anatomy: Digestive System

4 steps of digestion

Ingestion, Digestion, Absorption, Elimination

Ingestion

Taking food/drink into the body by swallowing

Mechanical Digestion

Physically breaking food into smaller pieces (chewing, churning)

Chemical Digestion

Using enzymes to break food into smaller molecules

Absorption

Nutrients move into the bloodstream for use by the body

Elimination

Removal of undigested material from the body

Main Role of the Digestive System

Break down food into small molecules for absorption and energy use

Metabolism

Chemical processes in the body that maintain life

Fast Metabolism

Faster chemical breakdown of food and energy

Primary Digestive Organs (Alimentary Canal)

Mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum, anus

Accessory Organs

Salivary glands, pancreas, liver, gallbladder

Salivary Glands

Produce saliva with water and amylase; lubricate food and start starch digestion

Pancreas

Produces digestive enzymes for carbs, proteins, and fats

Liver

Produces bile to emulsify fats

Gallbladder

Stores and releases bile into the small intestine

Bile

Emulsifies fats into smaller droplets for easier enzyme action

Lipase

Enzyme that breaks down fats into fatty acids and glycerol

Fats in the Body

Provide energy, insulation, vitamin absorption, and hormone production

Carbohydrates are broken into

Simple sugars (glucose) for quick energy

Proteins are broken into

Amino acids to build and repair tissues

Lipids/Fats are broken into

Fatty acids and glycerol for energy storage and hormones

Hydrolysis

Process where water breaks large molecules into smaller ones during digestion

Enzymes

Proteins that speed up (catalyze) chemical reactions without being used up

Lock and Key Model

Enzyme fits a specific substrate like a key fits a lock

Amylase

Breaks down starches (carbs)

Protease

Breaks down proteins

Lipase

Breaks down fats

All enzyme names end in - "

ase"

Enzyme Conditions

Work best at optimal pH and temperature; extreme conditions denature enzymes

Small Intestine Parts

Duodenum, Jejunum, Ileum

Duodenum

Main site of chemical digestion, receives bile and pancreatic enzymes

Jejunum

Primary site of nutrient absorption (sugars, amino acids, fatty acids)

Ileum

Absorbs remaining nutrients and bile salts

Villi and Microvilli

Fingerlike projections that increase surface area for absorption in small intestine

Capillaries in Villi

Absorb water soluble nutrients (sugars, amino acids)

Lacteals in Villi

Absorb fats and fat soluble vitamins (A, D, E, K)

Anabolism

Builds complex molecules, uses energy

Catabolism

Breaks down molecules, releases energy

Six Essential Nutrients

Water, Vitamins, Minerals, Carbohydrates, Lipids, Proteins

Water..

Regulates temperature, aids digestion, transports substances

Vitamins

Help enzymes, act as coenzymes, do not provide energy

Minerals

Inorganic, support bones, nerves, fluid balance

Carbohydrates

Primary energy source, stored as glycogen

Lipids (Fats)

Secondary energy source, insulation, forms membranes, make hormones

Proteins

Build/repair tissues, make enzymes, molecules

Where are Fat Soluble Vitamins - A, D, E, K Stored?

liver and fat tissue

Vitamin A

Vision, skin, immunity, found in carrots and leafy greens

Vitamin B Complex

Energy release, found in yeast, liver, grains

Vitamin C

Collagen, wound healing, found in citrus fruits

Vitamin D

Bone health, from sunlight, milk, fish oils

Vitamin E

Antioxidant, from nuts and vegetable oils

Vitamin K

Blood clotting, from leafy greens and gut bacteria

High Protein Diet Risks

Dehydration, nutrient deficiencies, kidney stress

Water Soluble Nutrient Pathway

Absorbed into capillaries - bloodstream

Fat Soluble Nutrient Pathway

Packaged into micelles -enter lymphatic system - bloodstream

Large Intestine Function

Absorbs water and salts, compacts waste into feces

Rectum

Stores feces before elimination

Gut Microbiome

Trillions of bacteria/fungi/viruses aiding digestion and immunity

Dietary Fiber

Feeds gut bacteria, improves immune function and reduces inflammation

Bifidobacterium

Breaks down fiber, produces short chain fatty acids for gut health

Lactobacillus

Breaks down lactose into lactic acid, prevents harmful bacteria growth

E. coli (beneficial)

Produces Vitamin K, protects gut lining

Probiotics Sources

Yogurt, kimchi, sauerkraut, tempeh, kombucha

Serotonin in the Gut

90% of body's serotonin made in the gut, affects mood, anxiety, and cravings

Food passes through mouth by

mechanical (chewing) and chemical (salivary amylase) digestion

Food passes through pharynx and esophagus by

peristalsis (muscle contractions)

Food is moved through the Stomach by

Mechanical churning and chemical digestion with acid and pepsin

Small intestine

main site of digestion and nutrient absorption

Large intestine

absorbs water and stores feces

Pancreas..

Releases enzymes and bicarbonate to the small intestine

Pancreas enzymes

amylase, lipase, trypsin