Transcript Liver

Human Anatomy and Physiology
The Digestive System
The Digestive System - Function
• Dissembles food to small molecules that
the body can absorb.
• Components:
– Mouth, pharynx, esophagus stomach, small
intestine, large intestine
– Accessory structures: Salivary glands, pancreas,
liver. These add secretions
Digestive System
• Total length 8-9 meters
– 2/3 small intestines
The digestive system
Mouth
Pharynx
Salivary glands
Esophagus
Liver
Gallbladder
(behind liver)
Rectum
Stomach
Pancreas (behind
stomach)
Large intestine
Small
intestine
Upper Digestive System
• Lips, Mouth (lips, tongue, teeth), salivary
glands, pharynx, esophogus,
Mouth
• Mechanical and Chemical Digestion
– Mastication – “chewing”
• Lips – hold food in
• Tongue – moves food around
• Teeth – cut, tear and crush
– Salivation – chemical digestion begins
• Moistens food – salt, water, mucous
• Amylase – starch breakdown to sugars
• Lysozyme – breaks down cells (especially pathogens)
• End result: Bolus
– Bolus pushed to esophagus
– Tongue and throat muscles
Salivary Glands and Pharynx
• Salivary glands
– Three pairs
• Parotid
• Submandibular
• Sublingual
• Pharynx
• Common passage
• Epiglottis
• Covering for the glottis (opening to the larynx)
Esophogus – about 25 cm (10 inches)
• Peristalsis
– Movements in the “food tube” that push food to the
stomach (voluntary muscle)
• Can eat in no gravity
• Can eat lying down
• Cardiac Sphincter (involuntary)
– Ring of muscle between stomach and esophagus
– Heartburn; acid reflux
• Overeating, high acid foods, high caffeine
Stomach
• Muscular sac
• Chemical Digestion
• Mucus – lubricates and protects the stomach wall
• Hydrochloric acid – provides acidity
• Pepsin
– Activated by HCl
– Begins protein digestion (with HCl)
• Muscular Digestion
– Fluids and food mix to form chyme
– After ~1 to several hours, goes through pyloric
valve to duodenum (1st part of small intestine)
Ulcers
• Caused by Helicobacter pylori
– Requires antibiotics, not bland diets
– Bacteria damage cells of stomach lining, make
stomach susceptible to ulcers, acid further
irritates.
Duodenum
• 1st part of small intestine
• Most chemical digestion here
– Enzymes & digestive juices from pancreas, liver,
and duodenum lining
Digestive System
Site
Enzyme
Salivary amylase
Mouth
Stomach
Pepsin
Small intestine
(from pancreas)
Amylase
Trypsin
Lipase
Small intestine
Maltase, sucrase, lactase
Peptidase
Role in Digestion
Breaks down starches into
disaccharides
Breaks down proteins into large
peptides
Continues the breakdown of
starch
Continues the breakdown of
protein
Breaks down fat
Breaks down remaining
disaccharides into
monosaccharides
Breaks down dipeptides into
amino acids.
Pancreas and Liver
• As chyme enters duodenum of small intestine, add
from:
• Pancreas
– For digestion:
• Amylase – continued starch breakdown
• Trypsin – protein;
• Lipase – fat breakdown
• Sodium bicarbonate – neutralizes stomach acid
– Also: Enzymes that regulate blood sugar levels.
• Liver
– Bile – acts like a detergent
• Disperses fat into droplets
• Lipase then breaks down fats
• Gall bladder – Bile storage area
The liver and pancreas
Section 38-2
Liver
Gallbladder
Duodenum
Bile duct
Pancreas
Pancreatic duct
To small intestine
Small Intestine
• Three parts
– Duodenum – very short (< 1 meter)
– Jejunum (3 meters)
– Ileum (3 meters)
• Role: Absorption of nutrients
– Folds - Villi  Microvilli
• Contain capillary fields
• Chyme moved slowly across surface
• Absorb protein and carbohydrate products
– Lacteals
• Lymph vessels which absorb fatty acids and undigested fats
Villus
Small Intestine
Circular folds
Villi
Epithelial
cells
Capillaries
Lacteal
Vein
Artery
Large Intestine
• What remains?
– Cellulose and undigested materials
– Water
– Bacteria
• Purpose: Water absorption
– Some vitamins produced here (K)
• Defecation
– Elimination of remaining waste material through
rectum. (Solid excretion)
Key Functions of Digestion
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Mastication (Mechanical)
Salivation (Chemical)
Peristalsis (Mechanical)
Actions of Enzymes/Acid (Chemical)
Muscular Digestion (Mechanical)
Absorption
Defecation