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GI System--Structure. MouthEsophagusStomachSmall IntestineLarge intestineRectumAnus. GI System--Structure. GI tract is about 30 feet long from mouth to anusLayers from inner to outerMucosaSubmucosaMuscle- 2 layersCircular (inner)Longitudinal (Outer)Serosa except esophagus (fibrous). GI
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1. Gastrointestinal SystemModule 1
2. GI System--Structure Mouth
Esophagus
Stomach
Small Intestine
Large intestine
Rectum
Anus
3. GI System--Structure GI tract is about 30 feet long from mouth to anus
Layers from inner to outer
Mucosa
Submucosa
Muscle- 2 layers
Circular (inner)
Longitudinal (Outer)
Serosa except esophagus (fibrous)
4. GI System--Structure Innervation
Sympathetic-inhibitory
Parasympathetic-excitatory
Example:
Peristalsis is increased with parasympathetic stimulation
5. GI System--Structure GI tract receives 25-30% of cardiac output
Venous blood empties into portal vein which peruses liver
Upper portion of GI tract receives blood from splanchic artery
Small intestine receives blood from hepatic and mesentery arteries
Large intestine receives blood supply from superior and inferior mesenteric arteries
6. GI System--Structure Two types of movement
Mixing (Segmentation)
Propulsion (Peristalsis)
Hormones and enzymes for digestion
Mucous provides protection, lubrication, water, electrolytes
7. GI System--Structure Abdominal organs are covered by peritoneum
Two layers of peritoneum
Parietal-lines abdominal cavity wall
Visceral-covers abdominal organs
Peritoneal cavity- space between parietal and visceral
Two folds of peritoneum
Mesentery-attaches small intestine to posterior abdominal wall
Lesser omentum-hangs from stomach like apron, contains fat and lymph nodes
8. GI SystemIntrinsic/Enteric layer GI tract has its own nervous system
Enteric or intrinsic
Two intrinsic layers
Lies between mucosa and the circular muscle layer
Other layer lies between circular and longitudinal layer
Innervation contributes to coordination of GI motor and secretory activities
Enteric nervous system is also known as the gut brain
Ability to control movement and secretion of GI tract
9. GI System-Function Supply nutrients to body cells
Ingestion (taking in) and propulsion (movement)
Digestion-breakdown
Absorptiontransfer of food products into circulation
Elimination-Excreting waste products
10. GI System-Function/Ingestion Swallowing (deglutition)-mechanical component of ingestion
Mouth
Lips
Oral cavity
Three pairs of salivary glands
Parotid
Submaxillary
Sublingual
Glands produce saliva (water, protein, mucin, salts, amylase(pytalin))
11. GI System-Function/Ingestion Pharynx
Esophagus
Upper third striated muscle
Distal two thirds-smooth muscle
With swallowing, peristaltic wave moves bolus into esophagus
Lower esophageal sphincter (LES) remains contracted except when swallowing, vomiting, or belching
LES-important barrier that prevents acid reflux from stomach
12. GI System-Digestion/Absorption Digestion is mechanical and chemical
Mouth
Lubricates and softens mass
Stomach
Stores food
Mixes food with gastric secretions
Empties contents into small intestine
13. GI System-Digestion/Absorption-Stomach Parts of stomach
Fundus
Chief cells (secrete pesinogen)
Parietal cells (secrete HCL, water, and intrinsic factor)
Acid Ph protects against ingested organisms
Intrinsic factor promotes cyclocobalamin (B 12) absorption in the small intestine
Body
Antrum
14. GI System-Digestion/Absorption-Stomach Pylorus
Small portion of antrum
Lies proximal to pyloric sphincter
Pyloric sphincter guards entrance to and from entrance to stomach
Rugae-folds in stomach, contains glands
15. GI System-Digestion/Absorption-Small Intestine Two functions
Digestion
Absorption-uptake of nutrients from gut to bloodstream
Approximately 23 feet long
Extends from pylorus to ileo cecal valve (prevents reflux from small intestine to large intestine)
Large surface area for absorption
16. GI System-Digestion/Absorption-Small Intestine Villi
Functional units of small intestine
Contains goblet cells
Secrete mucous
Epithelial cells
Produce digestive enzymes
Mirovilli-assist villi to increase surface area
Crypts of Liberkuhn-contain base columnar cells
Brunners glands-secrete mucous in duodenum
17. GI System-Physiology of Digestion Salivary gland-breakdown of starch
Stomach-releases of pepsinogen from chief cells
Acid in stomach converts of pepsinogen in to pepsin-initial breakdown of proteins
Stomach has minimal impact on breakdown of starches and fat
Food stays in stomach 3-4 hours
18. GI System-Physiology of Digestion-Small Intestine Carbohydrates broken down into monosaccharides
Fats to glycerol
Proteins to amino acids
Chyme (food mixed with gastric secretions)
19. GI System-Physiology of Digestion-Small Intestine Enzymes secreted from pancreas
Bile from liver
Intestinal secretions
Hormones secretin stimulates pancreas to produce bicarb (neutralizes acid in chyme)
Duodenum secretes mucous to protect small intestine from acid
Hormone cholecystokinin stimulates gall bladder contraction and relaxation of the sphincter of Oddi-bile released-digest fat
20. GI System-Physiology of Elimination-Large Intestine 5-6 feet long
Four parts
Cecum and Appendix
Colon
Rectum
Anus
Most important function-absorption of water and electrolytes
21. GI System-Physiology of Elimination-Large Intestine Forms feces until defecation
Feces
Water
Bacteria
Unabsorbed minerals
Undigested food
Bile pigment
Epithelial cells
22. GI System-Physiology of Elimination-Large Intestine Bacteria-
Responsible for breakdown of proteins not digested by small intestine
Synthesize Vitamin K and some B vitamins
Production of flatus
Slow movement-haustral churning
Defecation
Voluntary and involuntary muscles
Valsalva maneuver
23. Physiology of Elimination-Liver Largest internal organ in body
Right and left lobes
Lobules-functional unit
Rows of hepatic cells (hepatocytes)
Kupfer cells-phagocytic activity-removes toxins/bacteria from blood
Portal circulatory system brings blood to liver from stomach, intestine
Involved in metabolism, detoxification, destruction of RBC
24. Physiology of Elimination-Biliary Tract Consists of
Gallbladder-concentrate, store bile
Duct system
Bile-produced by hepatic cells
Moves down common bile duct, enters duodenum at ampulla of Vater
In intestine, bilirubin converts to stercobilirubin (color of stool) and urobilirubin (color of urine)
Sphincter of Oddi keeps ampulla closed
25. Physiology of Elimination-Biliary Tract Bilirubin metabolism
Breakdown of Hemoglobin
Bound to albumin for transport to liver (uncongugated)
In liver, conjugated with glucuronic acid
Conjugated bilirubin is soluable
26. Physiology of Elimination-Pancreas Exocrine and endocrine functions
Exocrine-digestion-pancreatic enzymes
Endocrine
Islets of Langerhans
Beta cells-insulin
Alpha cells-glucagon
Delta-somatostatin
F cells-pancreatic polypeptides
27. GI System and Aging Periodontal disease-loss of teeth
Taste buds, smell, salivary secretions decrease
Delayed gastric emptying
Motility of GI tract diminishes
Decrease in HCL secretion
Reduction in secretion of acid and intrinsic factor
Liver size decreases
28. GI System-Factors that Influence Function Stress/anxiety
Dietary intake
Ingestion of ETOH/caffeine
Cigarette smoking
Fatigue
Organic diseases
Others?