Lab 6 Digestive System1 Digestive tract Oral cavity

Lab # 6 Digestive System-1

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

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

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 Muscularis mucosae Stratified squamous epithelium 2 - Submucosa 3 - Muscularis externa: Inner circular layer Outer longitudinal layer Simple columnar epithelium 4 - Serosa Stratified squamous epithelium

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

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

Functions: The Tongue 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 (taste buds) (friction) (taste buds)

The Salivary Glands Functions: 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 Parotid ducts Parotid glands Sublingual glands Submandibular glands Mucous cells (Mucins) Serous cells (Enzymes) Duct

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

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

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

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

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

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

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

The Small Intestine Macroscopic anatomy 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

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

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

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

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