Digestive System

1. Digestive System

2. Digestion Facts Made up of the digestive tract and associated digestive structures Also called the alimentary canal Gastrointistinal tract - below the diaphragm Accessory structures include: tongue, teeth, salivary glands, pancreas, liver, and gall bladder

3. Functions Ingestion Taking food into the body Motility Movement of food through the digestive tract Secretion Adds substances to the lumen of the digestive tract to help digestion and absorption

4. Functions Digestion Breakdown of food into smaller molecules Absorption Transfer of digested nutrients from the digestive tract into the rest of the body Elimination Removes indigestible bits and waste from the body

5. Layers (tunics) of the Digestive Tract Mucosa Mucous membrane, the innermost layer, made of epithelial cells, glands, and lymph tissue Submucosa Loose connective tissue

6. Layers (tunics) of the Digestive Tract Muscularis mucosa 2 layers of muscle circular and longitudinal Mix contents of stomach and moves food through the digestive tract Serosa Peritoneum

7. Oral Cavity Contains the tongue and teeth Sensitive to pain, heat, and cold

8. Teeth Mastication Chewing breaks down food so that digestive juices can reach all parts Deciduous teeth (primary) 6mo - 2 yrs Baby teeth (20) that are replaced by - Permanent teeth 6 yrs - adult Odontoclasts, form permanent teeth (32), dissolve the roots of the deciduous teeth

9. Types of Teeth Incisors - biting, shearing Canine - tearing food Pre-molars - (bicuspids), biting and grinding Molars - biting and grinding Because humans are omnivores we have teeth to fit a varied diet

10. Tooth Anatomy Enamel Hardest substance in the body, not replaced Dentin Like bone Pulp Blood vessels and nerves

11. Tooth Anatomy Periodontal membrane Cementum and periodontal ligaments attach tooth to the jaw

12. Tongue Nearly fills the oral cavity when the mouth is closed Body of the tongue is skeletal muscle Mixes food with saliva Sensitive to 4 flavors, salt, sweet, sour, bitter

13. Functions Speech Swallowing Taste Papillae - bumps on the tongue Frenulum - attaches tongue to the floor of the oral cavity

14. Sense of Taste Taste buds are the organs of taste Associated with papillae Found in smaller numbers on the roof of the mouth and walls of the pharynx Chemicals of taste must be in water solution for the taste buds to sense them

15. Primary Taste Sensations Sweet - tip of the tongue Salty - tip and on the sides Bitter - at the back of the tongue Sour - sides of the tongue Alkaline and metallic are two other possible taste sensations

16. Palate Forms the roof of the mouth Hard palate Maxillary, palatine bones Soft palate Muscular arch extends down and back forming the uvula Soft palate keeps food from going up the nose

17. Salivary Glands Parotid Clear watery fluid with amylase Submandibular Serous fluid Sublingual Mucous

18. Salivary Gland Functions Puts food into solution so taste buds can pick up molecules Begins digestion of starches with sallivary amylase 1-2 liters of saliva are produced each day Mucous helps the food slide down the esophagus

19. Pharynx Nasal and oral cavities down to the level of the trachea Refer to the respiratory notes for the divisions of the pharynx

20. Other Structures in the Mouth Tonsils Pharyngeal Lingual Palatine

21. Swallowing Occurs in 3 stages 1. Food is chewed and mixed with saliva, mass is rolled into a bolus and moved to the pharynx by the tongue 2. Food reaches the pharynx and stimulates sensory receptors. This starts the swallowing reflex

22. Swallowing 3. Food is transported by the esophagus to the stomach by peristalsis, an involuntary muscular contraction It takes about 9 seconds for food to travel the 10 inch esophagus Deglutition (swallowing) both voluntary and involuntary

23. Esophagus 25 cm (10 inches) Collapsible Goes through the diaphragm Lined with mucous membranes and smooth muscle Cardiac or esophageal sphincter is the lowest limit of the esophagus

24. Stomach Upper left quadrant of the abdomen Held in place by the greater and lesser omenta May interfere with breathing if distended

25. Parts of the Stomach Fundus part above the cardiac sphincter Body Main part of the stomach Pylorus Area at the intestinal end of the stomach

26. Parts of the Stomach Cardiac Sphincter Muscle at the entrance to the stomach Pyloric Sphincter Muscle regulating the passage of food into the intestine Antrum Lowest part of the body

27. Layers of the Stomach Peritoneum Parietal Abdominal lining, is continuous with Visceral Covers some organs in the abdomen Submucosa Loose vascular layer

28. Layers of the Stomach Mucosa Epithelial layer Folded into Rugae inside the stomach Glands Gastric pits are located at the ends of gastric glands and form an outlet for gastric juice.

29. Layers of the Stomach Gastric Juice Made up of HCl, digestive enzymes Parietal cells Produce HCl and intrinsic factor (B12 absorption) Zygomatic (chief) cells Produce enzymes and mucous that protects the lining of the stomach

30. Physiology Cephalic phase Conditioned reflex, gastric juices begin to flow Gastric phase Solid food stimulates the production of gastrin, a hormone that stimulates the production of gastric juices

31. Physiology Intestinal Phase Stimulated by distention, acidity, end products of digestion Gastric contents are ready to enter the intestine

32. Motor Functions Storage of food Mixing food with digestive juice until chyme is formed Killing bacteria Empty food into the small intestine at a suitable rate

33. Stomach Facts Liquids move through the fastest Fatty foods move through the slowest 1 liter capacity Mixing waves (peristalsis) occur every 20 seconds Very little food is absorbed through the stomach, water, alcohol, and glucose can be

34. Vomiting

35. Causes Rapid changes in position Distention Excitement Irritation of the stomach Food Illness Vomiting center is in the medulla

36. Steps Take a deep breath Soft palate closes nasal cavity Glottis closes off the trachea Cardiac sphincter relaxes Stomach is squeezed between the abdominal wall and the diaphragm muscles

37. Gastritis Not a disease - usually a symptom of something else An inflammation of the stomach

38. Other Organs Organs that help with digestion

39. Liver Largest gland in the body Upper right side of the abdominal cavity 4 lobes, easily broken

40. Functions Produces bile Emulsifies fats Produces blood proteins Fibrinogen Prothrombin Globulins Albumin Heparin

41. Functions Converts glucose to glycogen Makes glucose from protein Food metabolism Detoxification Stores vitamins A, D, E, K (fat soluble)

42. Gall Bladder Small sack under the liver Stores bile Bile emulsifies fats and helps with the absorption of vitamins A, D, and K

43. Pancreas Exocrine Functions Secrete digestive enzymes (1400 ml/day) Large amounts of sodium bicarbonate are used to neutralize the acid Endocrine Functions Secrete insulin and glucogon

44. Small Intestines Duodenum First section 22cm long Digestive enzymes are pumped in here Jejunum 2 meters Ilium 3.5 meters

45. Functions Lining is made up of finger like structures called villi Total surface area = tennis court Most carbohydrate, protein and fat digestion occur in the small intestine Controls the amount of fluid lost during digestion

46. Functions Fluid enters the small intestine from liquid (1.5 liters) and as secretions from the digestive tract (7.5 liters) About 8.5 liters are reabsorbed before leaving the intestine Absorption of break down products takes place in the small intestine

47. Large Intestine Larger diameter (6cm) but shorter in length (1.5m) than small intestine Runs from ileocecal sphincter to the anus Finishes absorption, forms and stores feces, and eliminates feces from the body

48. Large Intestine Parts Cecum Pouch located in the lower right quadrant in the abdomen Extending from the cecum is the appendix (8cm) Colon Ascending, Transverse, Decending, Sigmoid, and Rectum

49. Large Intestine Parts Hepatic, Splenic Flexure Rectum Last 12cm of the digestive tract Anal Canal Last 4cm Internal and External Anal Sphincter Internal is involuntary muscle, External is voluntary

50. Large Intestine Facts No enzymes are secreted here Large amounts of mucous and water can be secreted if the large intestine is irritated Material can stay in the large intestine for 24 hours

51. Defecation When fecal material reaches the rectum it initiates a desire for defecation Feces generally contain about 75% water Solid part of feces is about 30% bacteria along with cell debris cell salts, and bile pigments Biliruben gives feces their brown color