Please enable JavaScript.
Coggle requires JavaScript to display documents.
Digestive system, Alimentary Canal:
Continuous Muscular Digestive tube…
-
Alimentary Canal:
- Continuous Muscular Digestive tube that extends from the mouth to the anus (Key terms)
- of the canal, the organs' main function is to nourish the body (23.1)
Mouth:
- beginning of the Alimentary canal.
- The teeth and the tongue begin mechanical digestion, breaking down the food physically. (23.1)
- The salivary glands begin chemical digestion (23.1)
Pharynx:
- propels food from the oral cavity to the esophagus; it also lubricates food and passage ways (23.2)
- When swallowing, elevator skeletal muscles contract causing the pharynx to rise and expand to receive bolus (23.3)
- forces bolus into esophagus and initiates Peristalsis (23.3)
Esophagus:
- Muscular tube that connects the Pharynx to the stomach that is 25.4 cm in length (23.3)
- has a mucosa made of epithelial lining that protects it from erosion against food particles (23.3)
Stomach:
- contributes to chemical and mechanical digest of food from the esophagus before releasing it, as chyme, to the small intestine (Key Terms)
- The stomach's muscularis has an inner oblique smooth muscle layer that allowing churning to break down food into smaller particles (23.4)
- The stomach's mucosa epithelial lining will secrete a protective coat of alkaline mucus (23.4)
Small Intestine:
- considered the primary digest organ because most digestion and almost all absorption occurs here (Key Terms)
- its mucosa and submucosa have features than can increase absorptive surface area up to 600-fold, including circular folds, villi, and microvilli. Prominent in the proximal 2/3s of the small intestine (23.5)
Large Intestine:
- Terminal part of the alimentary canal that functions to finish absorption of nutrients, water, synthesize certain vitamin, form feces, and eliminate feces from the body (23.5)
- Goblet cells of the Large intestine secrete mucus that ease the movement of feces and provides protection from the effects of acids and gases. (23.5)
- Enterocytes absorb water and salts as well as vitamins produced by intestinal bacteria (23.5)
Accessory Digestive Organs:
- aid in the breakdown of food (23.1)
- sprout lining cells of developing gut (mucosa) and enhance its function (23.1)
Salivary Glands:
- exocrine gland that secretes digest fluid called saliva (23.3)
- increases secretion when eating, helping moisten food and begins the chemical breakdown of carbohydrates (23.3)
- the submandibular gland lies on the floor of the mouth (23.3)
- The sublingual glands, lie below the tongue
- The parotid gland lie between the skin and the masseter muscle, near the ears. (23.3)
Teeth:
- tear, grind, mechanically break down food. (23.3)
- 8 incisors, the sharp teeth that we use for biting into food (23.3)
- 4 cuspids (canines), pointed edged teeth that help tear food (23.3)
- 8 premolars, helps mash food (23.3)
-12 molars, used to crush food so it can be swallowed (23.3)
Liver:
- largest gland of the body, it functions to produce bile (Key term)
- The bile salts emulsify lipids, aiding their digestion and absorption (23.2)
- the liver can process bloodborne nutrients and toxins. After doing so, it will release nutrients back into the blood (23.6)
Gallbladder:
- stores and concentrates bile (23.6)
- propels bile into the duodenum via common bile duct (23.6)
- nest in a shallow area on the posterior aspect of the right lobe of the liver (23.6)
Pancreas:
- Aids in digestion and regulation of blood glucose (Key Terms)
- produces protein-digesting enzymes in inactive forms that will later be activated in the duodenum (23.6)
- The sodium bicarbonate from pancreatic juice creates an optimal environment for pH-sensitive digestive enzymes in the small intestine. (23.6)
The Stomach:
- contributes to the chemical and mechanical digest of food from the esophagus before releasing it, as chyme, to the small intestine (Key terms)
Digestive Process:
- the mechanical process includes a mixing wave that will mix and soften food with gastric juices to create chyme (23.4)
- initial mixing waves are gentle but become more aggressive when reaching the pylorus.
- The chemical process includes lingual lipase; it will activate from the acidic chyme and break down triglycerides into free fatty acids, and mono/diglycerides (23.4)
Mucosal Barrier:
- protects the stomach from gastric juices (Key terms)
- covering the stomach wall is bicarbonate-rich mucus; it forms a physical barrier and neutralizes acids. (23.4)
- epithelial cells of the mucosa meet at tight junctions, blocking gastric juices from underlying tissue layers (23.4)
- stem cells where the gastric glands join the gastric pits will replace damaged epithelial mucosal cells. (23.4)
Response to Filling:
- stretch receptors are activated by distention. (23.4)
- distention triggers parasympathetic neurons to release ACh, increasing the secretion of gastric juice (23.4)
- HCI is produced from parietal cells, providing an acidic environment protein digestion, influenced by gastrin of enteroendocrine G cells (23.4)
Hormonal Regulation of Gastric Secretion:
- Gastrin stimulates the secretion of gastric acid (23.2)
- Secretin is produced by the duodenum, and it stimulates watery secretion of bicarbonate by the pancreas (23.2)
- Cholecystokinin stimulates the secretion of pancreatic enzymes, bile from the liver, and the release of bile from the gallbladder (23.2)
Stomach Gland Cells
Mucous Neck Cells:
- located in gastric glands of the upper part of the stomach (23.4)
- secretes a thin, acidic mucus; the role of this mucus is currently unknown (23.4)
Parietal Cells:
- located primarily in the middle region of gastric glands; it produces hydrochloric acid and intrinsic factor (23.4)
- The HCI produced is responsible for the high acidity of the stomach (23.4)
- The Intrinsic factor produced is a glycoprotein necessary for the absorption of Vitamin B12 in the small intestine (23.4)
Chief Cells:
- located in the basal regions of gastric glands (23.4)
- secretes pepsinogen, the inactive form of pepsin (23.4)
- Pepsin is the enzyme that begins break down of proteins in the stomach (Key terms)
Enteroendocrine Cells:
- found in gastric glands (23.4)
- secrete a variety of hormones into the interstitial fluid of the lamina propria. (23.4)
The Small Intestine:
- section of the alimentary canal where most digestion and absorption occurs (Key terms)
- 3.05 (10 feet) in length, 2.54 (1 inch) in diameter
Subdivisions:
- Duodenum, begins at the pyloric sphincter, bends posteriorly behind the peritoneum, makes c-shape around the head of the pancreas and ascends anteriorly to the peritoneal cavity, ending at the jejunum (23.5)
- Jejunum, it is about 3 feet, running from the duodenum to the ileum (23.5)
- Ileum, the longest part, about 6 feet in length. Thicker and more vascular. It joins the cecum at the ileocecal sphincter (23.5)
Digestive Process:
- mechanical digestion, it goes through segmentation, combining chyme and digestive juices, and pushing food particles against the mucosa to be absorbed (23.5)
-when most of the chyme becomes absorbed, segmentation is replaced my transport movements, forcing chyme through a short section of the small intestine (23.5)
- chemical digestion, Intestinal juices combine with pancreatic juice to provide a liquid medium to facilitate absorption (23.5)
- the digestion of proteins and carbohydrates is complete in the small intestine with the aid of intestinal/pancreatic juices. (23.5)
- lipid digestion here is facilitated by bile and the enzyme pancreatic lipase (23.5)
Modifications For Absorption:
- the small intestine has circular folds that cause chyme to spiral, providing the time needed for nutrients to be fully absorbed. (23.5)
- villi are vascularized projections that give mucosa a furry texture. These Villi have a capillary bed made of one arteriole and one venule. (23.5)
Intestinal Juice:
- mixture of water and mucus that helps absorb nutrients from chyme (23.5)
- has a pH around 7.4 to 7.8, and is a mixture of water and mucus (23.5)
The Large Intestine:
- The terminal portion of the alimentary canal (23.5)
- its main job is to finish the absorption of nutrients and water, synthesize certain vitamins, form feces, and eliminate feces from the body (23.5)
Anatomy & physiology:
- runs from the appendix to the anus, framing the small intestine on 3 sides'
- four subdivisions: cecum, colon, rectum anus.
- teniae coli, 3 bands of smooth muscle that make up the longitudinal muscle layer of the large intestine. (23.5)
- Haustra, tonic contractions of teniae coli cause the colon to bunch up into pouches (23.5)
- epiploic appendages, its purpose is unknown, however it is unique to the Large intestine (23.5)
Bacterial Flora:
- refers to the trillions of bacteria that live within the large intestine (23.5)
- many facilitate chemical digestion and absorption, eve synthesizing certain vitamins, and vitamin K (23.5)
- some of these bacteria are linked to increase immune response (23.5)
Functions:
- colon movements are triggered when chyme enters the cecum. Overall, mechanical digest consist of 3 types of movements: A slow moving Haustral contraction, peristalsis, and mass movement, a strong wave that quickly forces contents toward the rectum (23.5)
- chemical digestion is exclusively caused by bacteria in the lumen of the colon; bacteria will break down remaining carbohydrates. (23.5)
- absorbs 90% of ingested water (23.5)
The pancreas:
- important for both digestion and regulation of blood glucose (Key terms)
Function:
- releases secretions like bile and enzymes that are essential for digestion to continue (23.1)
- The pancreatic juice that is made contains digestive enzymes and bicarbonate ions (23.6)
- the endocrine function secretes glucagon, insulin, somatostatin, and pancreatic polypeptide (17.9)
Exocrine function:
- The exocrine part of the pancreas has grape-like clusters, acinus, that secrete pancreatic juice (23.6)
Pancreatic juice components:
- made of water, salt, sodium bicarbonate, and several digestive enzymes (23.6)
- Sodium bicarbonate is responsible for the slight alkalinity of pancreatic juice, creating an optimal environment for pH-sensitive digestive enzymes (23.6)
Pancreatic juice release regulation:
- Entry of acidic chyme into the duodenum stimulates the release of secretin, causing duct cells to release bicarbonate-rich pancreatic juice. (23.6)
- Presence of proteins and fats stimulate the release of CCK, which then stimulates acini to secrete enzyme-rich pancreatic juice. (23.6)
- during the cephalic phase and gastric phases, vagal stimulation will prompt the secretion of pancreatic juice (23.6)
The liver:
- plays a role in metabolism and regulation (23.6)
- it is divided into 2 lobes, larger right, smaller left (23.6)
- its main function is to produce bile (23.6)
Functions:
- absorbs nutrients, drugs, and toxins. (23.6)
- releases cells back into the blood after processing bloodborne nutrients and toxins (23.6)
- Produces Bile (Key Terms)
Bile production:
- secreted by Hepatocytes (23.6)
- increases when fatty chyme enters the duodenum and stimulates the secretion of the gut hormone Cholecystokinin (23.6)
Bile contents:
- mixture of water, bile salts, bile pigments, phospholipids, electrolytes, cholesterol, and triglycerides (23.6)
- The salt acts as an emulsifying agent (23.6)
- the salt and phospholipids are the most critical components of emulsification (23.6)
Enterohepatic Circulation:
- Recycling mechanism that conserves Bile Salts (Key Terms)
- Bile salts are absorbed and returned to the liver in the hepatic portal blood when reaching the ileum. (23.6)
- Hepatocytes excrete bile salts into newly formed bile. (23.6)