Anatomy Final - Digestive System I. Introduction a. Two...

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Digestive System I. Introduction a. Two main parts i. Gastrointestinal tract (GI)- mouth, pharynx, esophagus, stomach, small intestine, large intestine, anus ii. Accessory digestive organs – teeth, tongue, gallbladder, salivary glands, liver, pancreas b. Abdominopelvic cavity is line by 2 serous membranes = peritoneal membranes = peritoneum – secretes a watery fluid i. Visceral- fused to abdominal organs ii. Parietal – attaches to the body wall II. Histology of the GI tract – all parts of the GI tract have the same four layers a. Tunica Mucosa- innermost, 3 layers i. Epithelial layer- from mouth to stomach = nonkeratinized stratified squamous for protection, from stomach to anus – simple columnar epithelium 1. For absorption 2. Secretion a. Of digestive enzymes b. Mucus from goblet cells ii. Lamina propria – connective tissue with lymphatic nodules (aggregation of WBC) iii. Muscularis mucosae 1. Thin layer of smooth muscle b. Tunica Submucosa i. Connective tissue ii. Highly vascular iii. May contain mucous glands iv. Nerve plexus = submucosal (Meissner’s) plexus
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c. Tunica Muscularis- muscularis externa i. Most common pattern is two layers of smooth muscle ii. Inner – circular iii. Outer – longitudinal iv. The tunica muscularis contracts by means of peristalsis 1. Waves of smooth muscle contraction and are controlled by mysenteric (Auerbach’s) plexus d. Tunica Serosa or Tunica Adventitia i. Serosa = connective tissue with simple squamous epithelium ii. Adventitia – connective tissue III. Mouth – Oral Cavity a. Function i. Receive food ii. Initiates digestion 1. Mastication 2. Saliva a. Has enzyme amylase which breaks down carbs iii. Initiates swallowing b. Histology i. Tunica Mucosa 1. Nonkeratinized stratified squamous ii. Tunica submucosa 1. Connective tissue iii. Tunica muscularis 1. Facial muscles (skeletal) iv. Skin – outer c. Tongue – has papillae
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i. Filiform papilla 1. Most numerous, conical; for tactile sensation (touch, temperature, texture, hot, cold, etc) ii. Fungiform papilla 1. Larger, rounded 2. Has taste buds on anterior 2/3 rd a. microscopic iii. Circumvallate papilla 1. Has taste buds on sides of tongue 2. Macroscopic 3. Very large d. Palate – roof of oral cavity i. Hard palate 1. Maxilla and palantine bones ii. Soft palate = muscular arches 1. Uvula a. End of soft palate 2. Palatoglossal arch a. anterior 3. Palatopharyngeal arch a. Posterior 4. Between these two arches is the palantine tonsils e. Teeth = mastication f. Salivary glands = 3 glands i. Parotid gland 1. Largest 2. On masseter
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3. Secretes serous (watery) fluid 4. Fluid enters mouth through parotid duct ii. Submandibular 1. Secretes serous and mucous (thick fluid) iii. Sublingual 1. Secretes primarily mucus into the floor of the mouth g. Pharynx i. Common to respiratory and digestive systems ii. Connects the oral cavity to esophagus
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Anatomy Final - Digestive System I. Introduction a. Two...

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