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Exercise 38

Exercise 38. Anatomy of the Digestive System. Objectives. Overall function Organs of alimentary canal Accessory digestive organs General functions of organs/structures Histological structure of alimentary canal wall Stomach and small intestine specializations Enzymes produced

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Exercise 38

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  1. Exercise 38 Anatomy of the Digestive System

  2. Objectives • Overall function • Organs of alimentary canal • Accessory digestive organs • General functions of organs/structures • Histological structure of alimentary canal wall • Stomach and small intestine specializations • Enzymes produced • Deciduous and permanent teeth

  3. Digestive System • Provides body with nutrients, water, electrolytes essential for health • Organs ingest (take in), digest (break down), & absorb (take into bloodstream) food, and eliminate the undigested remains

  4. Alimentary Canal • Hollow tube extending from mouth to anus (gastrointestinal tract or GI tract) • Various accessory organs/glands empty into • “Disassembly Line”

  5. Alimentary Canal Histology • Mucosa (mucous membrane) Inner layer, lines lumen; secretion of enzymes, absorption of nutrients, protection • Surface epithelium: simple columnar • Lamina propria: areolar connective • Muscularis mucosa: smooth muscle—local movements of mucosa • Lacteals: in villi (small fingerlike projections) of small intestine, lymphatic capillaries—transport fatty acids to bloodstream LUMEN OUTER surface

  6. Lacteals will be in here ONE VILLUS Fig. 24-3

  7. Alimentary Canal Histology • Submucosa (superficial to mucosa; nutrition, protection) • Blood, lymph vessels, nerve fibers • Submucosal plexus is it’s intrinsic nerve supply Fig. 24-3

  8. Alimentary Canal Histology • Muscularis externa • Bilayer of smooth muscle: • Circular layer of muscle (deep) • Longitudinal layer of muscle (superficial) • Myenteric plexus = another intrinsic nerve plexus, controls these muscle layers  major controller of GI motility Fig. 24-3

  9. Alimentary Canal Histology • Serosa (visceral peritoneum) • Outermost tunic • Mesothelium, areolar connective tissue • Reduces friction as GI organs slide across one another and cavity’s walls, protects and anchors organs also Fig. 24-3

  10. Alimentary Canal Organs Fig. 24-1

  11. Alimentary Canal Organs • Oral cavity (mouth) • Labia (lips) • Hard palate (anterior roof of mouth) • Soft palate (posterior roof of mouth) • Uvula (fingerlike projection of soft palate) • Tongue (floor of oral cavity)

  12. Fig. 24-6

  13. Pharynx Nasopharynx (behind nasal cavity) Oropharynx (behind oral cavity) Laryngopharynx (epiglottis to larynx) Fig. 24-6

  14. Esophagus From pharynx through diaphragm to gastroesophageal sphincter at esophagus-stomach junction, controls food passage into stomach

  15. STOMACH • (left side of abdominal cavity) • Cardiac region: upper region, through which food ENTERS stomach • Fundus: superior & lateral to cardiac • Body: middle portion, inferior to fundus • Pyloric region: terminal part of stomach, continuous w/small intestine • Pyloric sphincter: between stomach & small intestine

  16. Alimentary Canal Organs • Stomach (left side of abdominal cavity) • Greater curvature: lateral, convex • Lesser curvature: medial, concave • Rugae: prominent folds in the mucosa when stomach’s empty

  17. Fig. 24-12

  18. SMALL INTESTINE ~2m long • Duodenum: from pyloric sphincter around pancreas • Jejunum: umbilical region of abdomen • Ileum: terminal portion, joins lg intestine • Plicae circularis: like rugae, deep folds • Ileocecal valve: between small and large intestine

  19. Fig. 24-16

  20. Fig. 24-17

  21. LARGE INTESTINE ~1.5m long Encircles the small intestine on 3 sides • Cecum: 1st region, expanded pouch • Appendix:  attached to cecum, ~3.5” long • Ascending colon: up the right side • Transverse colon: across the top • Descending colon: down the left side

  22. Fig. 24-23

  23. LARGE INTESTINE • Sigmoid colon: S-shaped curve (behind bladder) between descending colon and • Rectum: last 6” of digestive tract • Anus: exit of the anal canal • Anal sphincter: muscle layers (2) surrounding the anus

  24. Fig. 24-23

  25. LARGE INTESTINE • Teniae coli: 3 external longitudinal muscle bands of muscularis, shorter than rest of wall, cause it to pucker into • Haustra: small pocketlike sacs

  26. Fig. 24-23

  27. ACCESSORY Digestive Organs • Teeth • Deciduous: appear 6 months-2.5 years; begin to lose teeth around 6 years old • 20 teeth • 2, 1, 0, 2 x 2 = 20 2, 1, 0, 2 Each SIDE of the jaw Upper: 2I, 1C, 0 PM, 2M Lower: 2I, 1C, 0 PM, 2M SIDES of the jaw

  28. TEETH • Permanent: gradually replaces the 1st set to age 12 • 32 teeth • 2, 1, 2, 3 x 2 = 32 2, 1, 2, 3 Each SIDE of the jaw Upper: 2I, 1C, 2 PM, 3M Lower: 2I, 1C, 2 PM, 3M

  29. Permanent Teeth Central incisors Lateral incisors Canines (cuspids) 1st premolars (bicuspids) 2nd premolars (bicuspids) 1st molars 2nd molars 3rd molars For biting For chewing

  30. Fig 24-9

  31. Fig. 24-8

  32. Teeth • Anatomical crown: entire area of tooth covered by enamel • Clinical crown: portion of tooth visible above the gum • Root: inferior portion (base) of the tooth (below the gum)

  33. Fig. 24-8

  34. Teeth • Enamel: “white” mineral (calcium salt) outer covering of crown • Dentin: like bone, but no cells; under enamel, it’s most of the tooth • Pulp, pulp cavity: interior chamber of the tooth—has blood vessels & nerves

  35. Fig. 24-8

  36. SALIVARY GLANDS • Parotid glands: inferior to zyg. arch, lateral/posterior mandible • Submandibular glands: floor of mouth, along inside of mandible • Sublingual glands: floor of mouth, more anterior & under tongue

  37. Fig. 24-7

  38. LIVER • Right, left, caudate, quadrate lobes Fig. 24-19

  39. LIVER • Falciform ligament: divides Rt/Lt lobes Fig. 24-19

  40. LIVER • Round ligament: thickened posterior part of falciform ligament Fig. 24-19

  41. LIVER • Hepatic ducts: right, left—collect bile (secreted by liver) from all bile ducts of lobes, unite to form the • Common hepatic duct which leaves the liver…bile then flows to • Cystic duct which leads to the gallbladder (stores/concentrates bile)….OR goes to the • Common bile duct which is formed by union of cystic and common hepatic ducts--empties into the duodenum (sm intest),

  42. Fig. 24-21

  43. PANCREAS • Posterior to stomach, extends laterally off the duodenum toward the spleen • Secretes digestive enzymes and buffers via the • Pancreatic duct into the duodenum • Accessory pancreatic duct branches off the larger pancreatic duct, also empties into duodenum • Hepatopancreatic sphincter (muscle) controlling entrance of substances (from common bile duct, pancreatic duct) into duodenal ampulla

  44. Fig. 24-18

  45. Fig. 24-21

  46. Microscope Work • Stomach • Gastric pits: shallow depressions, open onto gastric surface; mucous cells at base of each one mitotically active—shed into chyme (acidic “soup” of stomach secretions and food)

  47. Fig. 24-13 Fig. 24-13

  48. Microscope Work • Small intestine • Villi: fingerlike projections all over the plicae circulares One VILLUS Fig. 24-17

  49. Microscope Work • Large intestine (no villi in colon) • Goblet cells (unicellular glands) abundant • secrete mucus to help GI motility Fig. 24-24

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