digestive system organs digestive system broken down into 2 parts 1. alimentary canal –...
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DIGESTIVE SYSTEM
ORGANS
DIGESTIVE SYSTEM BROKEN DOWN INTO 2 PARTS
1. Alimentary Canal – gastrointestinal (GI Tract) – Path that food travels
2. Accessory Organs
GI Tracts Oral Cavity
Pharynx
Esophagus
Stomach
Duodenum
Jejunum
Ileum
Cecum
Accessory Organs
Tongue
Liver
Parotid Gland
Sublingual Gland
Submandibular Gland
Uvula
Lingual Frenulum
Ascending Colon
Transverse Colon
Descending Colon
Sigmoid Colon
Rectum
Anus
Pancreas
Gallbladder
Appendix
MOUTH
Palate:HardSoftUvula
Tongue
SALIVARY GLANDS
Cleanses Mouth Important for Taste Moistens food Contains Enzymes
MAJOR SALIVARY GLANDS
•Parotid gland •Submandibular gland•Sublingual gland
The average person produces 1000-1500 ml a day
TEETH
Masticate = to chew
Baby teeth (deciduous)Full set = 20 teeth
Permanent teeth = 32 teethIncisorsCaninesPremolars/molars
PHARYNX
Longitudinal & Circular layers of Muscles Peristalsis
Peristalsis - is a radially symmetrical contraction and relaxation of muscles that propagates in a wave down a tube
ESOPHAGUS
Propels food using muscles (Peristalsis)
STOMACH
Mostly Protein DigestionNo Absorption***Mechanically & Chemically Digested Into ChymeGastric glands produce gastric juice: acidicWalls of Stomach lined with mucus so the acid doesn’t “digest itself”
CHYME
Substance in the stomach that is formed from food and enzymes
PROBLEMS OF THE STOMACH
Ulcers: a hole in the mucus lining of the stomach
Heartburn (acid reflux): contents of stomach move into esophagus
SMALL INTESTINE
SM. INTESTINE
Chemical digestion of carbohydrates, proteins, nucleic acids, & fatsDone with enzymes from pancreas and bile (formed in liver)Pancreatic duct and bile duct empty into duodenum – where enzymes empty into.
LARGE INTESTINE Function:To absorb waterEliminate residue as fecesAbsorb vitamins produced by bacteria
Role of Bacteria:Digest some nutrientsProduce vitaminsProduce gas
ACTION OF L. INTESTINE Peristalsis Mass Peristalsis: a strong wave that pushes contents towards rectum
Problems:DiarrheaConstipation
ACCESSORY ORGANS - PANCREAS
Releases enzymes into duodenum
Has an endocrine function
ACCESSORY ORGANS - LIVER
Produces bile; leaves through common hepatic duct Bile: part waste produce, part digestive secretion (mechanical digestion of lipids)
OTHER LIVER FUNCTIONS
Metabolism of carbs, lipids, and proteins Processing of drugs and hormones Excretion of bilirubin (from hemoglobin of old RBCs)
ACCESSORY ORGANS - GALLBLADDER
Releases bile in response to fatty food entering duodenum Location: underside of liver Gallstones
STEPS OF DIGESTION
DIGESTION
Major functions of the digestive tract are digestion and absorption
ESSENTIAL ACTIVITIES OF THE GI TRACTIngestionPropulsionFood Breakdown – mechanical digestionFood Breakdown – chemical digestionAbsorptionDefecation
1. INGESTION
•Food must be placed into the mouth before it can be acted on.
•Active, voluntary process
2. PROPULSION
•In order for food to be processed by different organs, they must be propelled from one organ to the next.
•Example:•Swallowing – depends on the propulsive process called peristalsis•Peristalsis – involuntary and involves alternating waves of contraction and relaxation of the muscles in the organ walls
3. FOOD BREAKDOWN – MECHANICAL DIGESTION•Mixing of food in the mouth by the tongue•Churning food in stomach•Segmentation – propels foodstuffs through the small intestine
•Prepares food for further degradation by enzymes
4. FOOD BREAKDOWN – CHEMICAL DIGESTION
•Sequence of steps which large food molecules are broken down to their building blocks by enzymes
5. ABSORPTION
•Transport of digested end products from the lumen of the GI tract to the blood or lymph
•For absorption to occur, digested foods must first enter the mucosal cells by active or passive transport processes
•Small intestine is major site of absorption
6. DEFECATION
•Elimination of indigestible residues from the GI tract via the anus to form feces
NEURAL & HORMONAL CONTROL
CEPHALIC PHASE•Occurs before food enters the stomach, especially while it is being eaten
•Brain is activated by smell, sight, thought, and taste of food
•Neurons to salivary glands and gastric glands/stomach muscles
•Autonomic Nervous System
GASTRIC PHASESTIMULUS: FOOD IN STOMACH•Neural:•Stretch receptors activated. Impulse to neurons in submucosa
•Triggers:•Gastric gland production and causes peristalsis
•Hormonal:•Food triggers release of gastrin. Goes in the blood.•Triggers:•Gastric gland juices•Sphincter to prevent acid-reflux
•Stomach muscles•Relaxes lower stomach sphincter
INTESTINAL PHASESTIMULUS: FOOD IN INTESTINE•Neural:•Stretch receptors to medulla oblongata
•Sympathetic nerves to stomach cause:•Decreased stomach movement & increase contraction of pyloric – bottom – sphincter (delays stomach emptying)
•Hormonal:•Cholecytokinin (CCK): stimulates pancreatic juice/squeezes gallbladder
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