Digestive System - created from Mind Map

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Layers of Digestive Tract

Oral Cavity

Swallowing (deglutition)

Four Regions of the Stomach are:

Gastric Secretion Phases

Subdivions of the small intestines

Pancreatic Enzymes

Hepatitis Viruses

Intestinal Hormones(endocrine)

Mucosa(most superficial layer):

oral cavity: lined by stratified squamous

Stomach, small/large intestines: lined by simple columnar epithelium+goblet cells+enteroendocrine cells (which secrete hormones, break down foods and protects from acids)

Submucosa

dense irregular CT with blood vessels, lymphatic exocrine glands(secrete buffers and enzymes

Muscular Externa

submucosa plexus: outer layer of submucosa has sensory neurons, PSns ganglionic neurons, and sympathetic postgangionic fibers, innervate mucose and submucosa

smooth muscle cells with inner circular layer and outer longitudinal layer for mechanical processing and movement of materials

Serosa

(visceral peritoneum) serous membrane covering most digestive tract(covering the muscularies externae of the stomach, small/large intestines)

Oral mucosa lines oral cavity

stratified squamous, some keratinized cells in areas of abrasion such as the superior surface

occlusal

opposing surfaces of teeth

Periodontal ligament

collagen fibers extend from dentin of the root to the bone of the alveolus (bony socket where tooth sits)

Dentin

Mineralized matrix inside the tooth, you see enamel

Crown

exposed portion of tooth, you see enamel

Enamel

Calcium phosphate compound-hardest biological substance. Need calcium, phosphates, and Vitamin D during childhood to build enamel

Root

Base of tooth, blood vessels and nerves enter the root canal through apical foramen

Cementum

Layer of bony substance that covers the dentin in the root region and anchors the tooth to the periodontal ligament

Buccal Phase

Bolus is pressed against the hard palate. The tongue retracts and pushes bolus into the oropharynx ( the soft palate lifts to isolate the nasopharynx). The buccal phase is all voluntary control.

Pharyngeal Phase

The swallowing reflex is initiated by stimuli to the palatal arches' receptors of the uvula (signals swallowing center in medulla oblongata). Larynx elevates and the epiglottis folds over the glottis so the bolus bypasses entry to the trachea

Esophageal Phase

Pharyngeal muscles contract and push bolus down the esophagus to the stomach

Cardia

smallest part of stomach, lots of mucous glands that coat the connection with the esophagus with alkaline mucous

Fundus

Superior to the junction of esophagus and stomach. The fundus contacts the diaphragm

Body

Largest region of stomach, mixing tank, gastric glands secrete most of the stomachs acids and enzymes

Pylorus

Curve of the J, empties into the duodenum. glands secrete mucus and hormones (gastrin)

Cephalic Phase

Stimuli ( smell of foods, thoughts of foods, sight of foods) trigger parasympathetic neurons. In response to stimulation the rate of gastric juice increases. this phase lasts for minutes

Gastric Phase

Stimuli (distention of stomac,) increase of pH in stomach, the presence of undigested material in the stomach) signal neural, hormonal, and local responses. This phase lasts for 3-4 hours

INTESTINAL PHASE

Stimuli is chyme arriving in the duodenum. Involves a neural response ( enterogastric reflex), and a hormonal response (secretion of CCK), gastric inhibitory peptide (GIP) and secretin).

results are inhibit gastric production , inhibit pepsinogen production, and reduce stomach contractions. This phase lasts for hours.

Duodenum

most proximal segment. Functions as a mixing bowl that mixes chyme and digestive secretions from the pancreas and liver, and neutralizes acids. Has few plicae and small villi

Stimulus of the chyme stimulates secretion of secretin which tells the pancreas to secrete pancreatic juice which alkalizes. CCK is released and increases production and secretion of pancreatic enzymes

Jejunum

Bulk of chemical digestion and nutrient absorption. Plicae and villi are more predominant. So if you cut out part of this segment you willl lose weight due to decreased absorption

Ileum

longest segment. ends at ileocecal valve which controls flow of materials from ileum to cecum. Distal ileum lack plicae(circular folds)

Carbohydrases ( ex: pancreatic-alpha-amylase)

Similar to salivary amylase, breaks down certain starches

Pancreatic Lipase

breaks down certain complex lipids, release fatty acids that can be absorbed

Nucleases

Break down of nucleic acids (DNA/ RNA) protects from some viral and bacterial species

Proteolytic Enzymes

Breakdown certain proteins. Majority of pancreatic enzymes are these which get activated in intestines

Proteases- enzymes that digest large protein complexes

Peptidases- enzymes that digest peptide chains in amino acids

Hep A

Hep B

Food Born

Hep C

Blood Born

chronic cases get cumulative liver damage, increase risk of liver cancer or fatal liver failure, interferon and antivarl drugs slow the progression of the disease

Hep D

Blood Born

chronic cases can cause liver disease , liver cancer or failure, interferon and antiviral drugs slow the progression of the diease

Hep E

Blood Born

in combo with hep B causes severe liver disease , liver cancer or failure

Food Born

Rare in US only-acute infections lethal to pregnant women

Vaccine

Vaccine

Enterocrinin

Produced by duodenal enteroendocrine cells

Secretin

Stimulated by chyme entering the duodenum. Stimulates duodenum submucosa glands to secrete alkaline mucus

Cholecystokinin (CCK)

(+) by chyme entering the duodenum. tells liver to secrete more buffers and secondary effect is the decrease of gastric motility and secretory rates of the stomach

Gastric Inhibitory Peptide (GIP)

(+) by chyme in duodenum (especially lipids and partial digest proteins) Decreases Hunger

Vasoactive Intestinal Peptide (VIP)

(+) by fats and carbs entering duodenum. (+) lipid synthesis of adipose tissue and (+) glucose use in skeletal muscles. Increases release of insulin and inhibits gastric secretion and motility

Gastrin

(+) by chyme in duodenum . (+) buffer secretion of intestines, inhibits acid production in the stomach. Dilates capillaries in stomach to increase absorption

made by G cells in duodenum as well as produced in the stomach. (+) by CN X, chyme in intestines or food in stomach. (+) production of acids, enzymes, and increases gastric motility