Digestive System-1

1. Lab # 6 Digestive System-1 (Martini, Chapter 24, page 895)

2. Digestive tract Accessory organs - Oral cavity - Pharynx - Esophagus - Stomach - Small intestine - Large intestine Digestive System - Teeth - Tongue - Salivary glands - Liver - Gallbladder - Pancreas

3. Oral cavity Pharynx Tongue and teeth Esophagus Salivary glands Liver Stomach Gallbladder Pancreas Large intestine Small intestine

5. Most of the digestive tract follows the basis structural plan with digestive tract wall consisting of the following tissue layers, in order from the inner to the outer surface: Cross section of the esophagus 1- Mucosa: Stratified squamous epithelium Lamina propria Stratified squamous epithelium Muscularis mucosae 2- Submucosa 3- Muscularis externa: Inner circular layer Simple columnar epithelium Outer longitudinal layer 4- Serosa Stratified squamous epithelium

6. Stomach Esophagus Simple columnar epithelium (it contains gastric pits and gastric glands) Stratified squamous epithelium (also in oral cavity, pharynx and esophagus). Diaphragm Three layers of smooth muscle in the muscularis externa: outer longitudinal, middle circular, and inner oblique. Two layers of smooth muscle in the muscularis externa: outer longitudinal and inner circular. Folds of the mucosa called rugae. Longitudinal folds of the mucosa that allow for expansion Large Intestine Taeniae coli Small Intestine Simple columnar epithelium with microvilli (it contains crypts of Lieberkuhn and intestinal glands) Transverse folds of the wall called haustra. Simple columnar epithelium without villi (it is dominated by mucous cells) Two layers of smooth muscle in the muscularis externa: outer longitudinal and inner circular. Two layers of smooth muscle in the muscularis externa: outer longitudinal reduced to the taeniae coli, and inner circular. Transverse folds of the mucosa called plicae circulares, and fingerlike projections called villi.

8. Soft palate Hard palate Uvula Upper lip Cheek Vestibule Lingual frenulum Lower lip The Oral Cavity 1- The Lips and the Cheeks, 2- The Palate Functions: 1- Ingestion takes place, 2- Mechanical and chemical digestion start Tongue

9. (taste buds) (taste buds) The Tongue Functions: 1- Mechanical digestion, 2- Keeping the food against the teeth during chewing and swallowing, 3- Analysis of food (touch, temperature, and taste receptors), 4- Secretion of mucus and lingual lipase, 5- Helping in speech (friction)

10. Parotid ducts Mucous cells Serous cells Parotid glands Submandibular glands Duct Sublingual glands The Salivary Glands They secret saliva which 1- Cleanses the mouth, 2- Dissolves and moistens food, and 3- Contains enzymes that starts the break down of the carbohydrates Functions: (Mucins) (Enzymes)

11. Enamel Dentin Crown Gingiva or gum Neck Periodontal ligament Root Cementum Root canal Blood vessels and nerve The Teeth Functions: Mechanical break down of food (chewing or mastication) Pulp cavity

12. Central incisor Cuspid or canine Lateral incisor Bicuspids or premolars Molars Total: 20 primary, temporary or deciduous teeth The Teeth (Blade-shape teeth: Clipping and cutting) (Conical with a sharp ridgeline and a pointed tip: Tearing or slashing) Upper dental arch (Flattened crown with prominent ridges: Crushing, smashing and grinding) (Very large flattened crowns with prominent ridges: Crushing and grinding) Lower dental arch Total: 32 permanent or secondary teeth

14. Nasopharynx (air passageway) Pharyngeal tonsil Eustachian or auditory tube Oropharynx Soft palate (food and air passageway) Laryngopharynx Palatine tonsil (food and air passageway) Lingual tonsil Epiglottis Glottis The Pharynx Function: It propels the food to the esophagus.

15. The Esophagus Function: It carries food and liquids to the stomach Mucosa

17. The Stomach Fundus Cardia Serose Oblique layer Circular layer Longitudinal layer Mucosa Muscularis Externa: Pyloric region: Lesser curvature Pyloric Antrum Body Pyloric canal Pyloric sphincter Greater curvature Duodenum Rugae

19. Simple columnar epithelium Mucosa Gastric pit Lamina propria Muscularis mucosae Submucosa Oblique muscle Circular muscle Longitudinal muscle Serosa (visceral peritoneum) Histology of the Stomach It secrets alkaline protective mucus

20. Gastric pit Parietal cells Chief cells Gastric gland G cells Mucous cells They produce alkaline protective mucus They produce HCl and Intrinsic Factor They produce Pepsinogen (In new born and infants produce rennin and gastric lipase) They are enteroendocrine cells that produce Gastrin, Somatostatin, Histamine and Serotonin

22. Macroscopic anatomy The Small Intestine It is the major digestive and absorptive organ of the body. It extends from the pyloric sphincter to the ileocecal valve (19.7 ft ) Functions: 1- To complete digestion 2- To absorb 99% of the digested nutrients Duodenum (10 inches) It receives the pancreas and liver secretions that mix with the chyme Jejunum (8.2 ft ) It is where most chemical digestion and absorption take place Ileum (11.48 ft ) It is where digestion is completed. It ends at the ileocecal valve, which control the passage of undigestive materials to the large intestine

23. Microscopic anatomy Plicae Circularis They increase the surface area for absorption They make chyme spiral through the lumen to mix with intestinal juice They slow movement to allow time for absorption

24. Microscopic anatomy Mucosa Submucosa Plicae Muscularis externa Serosa General Structure of the Small Intestine Highly folded lining where absorption occurs Connective tissue containing blood vessels and nerves Circular and longitudinal muscle layers used for peristalsis Peristalsis: The contraction of the smooth muscle that produces waves, which push materials along the length of the digestive tract Connective tissue

25. Microvilli Absorption of nutrients Epithelium Lacteal Capillary network Nerve Arteriole Lymphatic vessel Venule (Simple columnar) Villus Plica

29. Large colon Ileocecal valve F- The Large Intestine Functions 1- Reabsorb water 2- Compact undigested food stuff into feces 3- Eliminate faces 4- Absorb bacterial vitamins 5- Store fecal matter until defecation Cecum Rectum Anus