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130 Cards in this Set
- Front
- Back
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What is the primary function of the Digestive system?
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To transfer nutrients, water and electrolytes from the food we eat into the body's internal environment
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What 3 layers comprise the internal (mucosa)?
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1. Mucous membrane
2. Lamina Propria 3. Muscularis Mucosa |
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What's the function of goblet cells?
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Mucous producing cells in the Mucosa
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Describe the function of Exocrine cells of the mucosa?
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Dispersed among the epithelial cells produce digestive juices (ex parietal cells)
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What do the endocrine cells of the mucosa do?
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Produce GI hormones ie gastrin
-can act on the same organ or different organs |
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What is the Lamina Propria?
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Middle layer of the intestinal mucosa that is composed of connective tissue
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Describe the Muscularis Mucosa?
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Outer layer of the the Mucosa
-Can differ in thickness based on the location along the GI tract |
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Describe the small intestine muscularis mucosa?
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Arranged in deep folds called villi that increase surface area of the intestine
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Where does the submucosa layer of the digetive tract?
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Between the intestinal mucosa and the muscularis externa
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What comprises the muscularis externa?
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1. Inner Cirucular muscle
2. Outer Longitudinal muscle |
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A contraction of the inner circular muscle causes what type of tubal movement?
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Lengthens the tube
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How is the digestive tube shortened?
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By contracting the longitudinal muscle
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What is the outmost layer of the digestive tract?
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The serosa
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How is the serosa attached to the body wall?
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By the Mesentery
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What is the mesentery?
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Double fused layer of serous membrane that attaches the serosa to the body wall
-Also provides a conduit for nerves, vessels and lymphatic vessels to meet the organ |
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The thin membrane that lines the cavities of the digestive tract and covers the organs of the abdoment is called?
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The peritoneum
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What is the space enclosed by the peritoneum called?
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Parietal cavity
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List the 4 basic digestive processes
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1. Motility
2. Secretion 3. Digestion 4. Absorption |
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What are the 2 types of movements in the digestive tract?
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1. Mixing movements
2. Propulsive movements |
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What is the primary propulsive movement in the GI?
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Peristalsis
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Which muscles are used in peristalsis? What is the specific action?
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Both circular and longitudinal
-Circular: behind the contraction to promote propulsion -Longitudinal: In front of the food to push it forward |
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What is the exception of peristalsis only acting as a propulsive?
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In the stomach where it also acts to mix
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What is the primary mixing movement?
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Segmentation contractions
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What muscles are used in segmentation contractions?
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the Circular muscles in a random pattern to chop and mix the food with digestive enzymes
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Where do segmentation contractions also help with propulsion?
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In the SI
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What are the 3 categories of foodstuffs that humans consume?
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1.Carbohydrates
2. Proteins 3. Fats |
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Which carbohydrates taste sweet on the tongue?
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Disaccharides
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Give 4 ezymes that are used to breakdown carbohydtrates to glucose.
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1. Amylase
2. Maltase 3. Sucrase 4. Lactase |
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Where are proteins denatured?
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in the stomach
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How are proteins absorbed into the blood stream?
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In the form of single amino acids
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What enzyme breaks down fat?
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Lipase
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What body product is used to emulsify fat?
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Bile
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What is the most important process in the digestive tract?
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Absorption
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Which organ is most responsible for Absorption?
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The small intestine
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The mouth has what type of motility?
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Chewing
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State the enzymes/products secreted in the mouth
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1. Mucus
2. Amylase: immediately starts to break down carbs 3. Lysozyme: natural antibacterial agent |
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What product begins digestion in the mouth?
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Carbohydrates
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Does any absorption take place in the mouth?
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No food, only sublingually administered drugs
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The pharynx and esophagus have what responsibility in the GI tract?
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They have motility: get food to the stomach.
-No digestion, no absorption |
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What type of motility occurs in the stomach?
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1. Receptive relaxation
2. Waves of peristalisis (propulsive and mixing) |
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Describe the secretion in the stomach.
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Gastric Secretions
-Juices: HCL, pepsin, mucous (protective function) and intrinsic factor -hormone: gastrin |
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What digestion begins in the the stomach?
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Protein
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What product in the stomach allows for protein digestion?
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pepsin
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Does any food absorption take place in the stomach?
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NO!
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What absorption takes place in the stomach?
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1. Fat soluble substances
2. drug absorption (asparin) |
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What are the pancreas and liver considered?
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Accessory organs
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What is the function of the pancreas in digestion?
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Exocrine!
-Releases cocktail of digestive enzymes that break down every category of food! |
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Where are the pancreatic juices released?
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In the duodenum
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What is the main type of Lipase used in digetstion?
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Pancreatic Lipase
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What does not occur in the pancreas?
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Motility and Absorption
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What is the the only digestive function of the Liver?
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The secretion of bile!
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Describe motility in the SI?
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Very Slow
-Segmentation contractions (mixing and propulsion) |
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What ist secretion like in the SI?
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Mucous and Hormones
-Receives the critical pancreatic enzymes/juices and bile from the liver |
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What digestion begins in the SI?
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Fat!
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What does the SI Digest?
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Fat and all other types of food complete digestion In the SI
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Where does absorption occur?
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All food and most electrolytes and water is absorbed in the SI
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What 2 types of motility that occur in the LI?
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1. Mass movements: waves of peristalsis
2. Haustral contractions :segmentation/mixing movements |
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Do any secretions occur in the LI?
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None, except for mucus
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What type of absorption takes place in the LI?
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More water and electrolytes
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Does any digestion occur in the LI?
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No
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What are the Non-Digestive Functions of the GI tract?
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1. Excretion
2. Fluid/Electrolyte Balance 3. Immunity |
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What is Gut Associated Lymphoid Tissue (GALT)?
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Immune cells: lymphocytes and mast cells in between epithelial cells and in the Lamina Propria
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What is the primary neural mechanism that control Gi function?
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Enteric Nervous System (intrinsic neural system of the gut)
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What section of the autonomic nervous governs the enteric nervous system?
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The parasympathetic
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What are the cells of the Hepatic Phagocytic System?
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Kupffer cells
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Which system of the involved in digestion can function autonomously?
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the enteric nervous system
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What are the 2 major neural networks of the ENS?
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1. Myenteric Plexus
2. Submucosal Plexus |
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Where is the myenteric plexus located?
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Between the ciruclar and longitudinal muscles of the muscularis externa
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What is the function of the myenteric plexus?
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Regulates all gut motility (anything that triggers motility is governed by the myenteric!!)
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Where is the submucosal plexus located?
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Submucosal layer
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What are the 2 functions of the submucosal Plexus?
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1. Regulates secretion
2. Indirecetly influences gut motility |
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Give an example of when the submucosal plexus would tell the myenteric to speed up motility.
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When it senses bacterial toxins (diarrheal state)
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What is extrinsic control of the gut?
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Control by nerves from both branches of the autonomic nervous system (Vagal Stimulation
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The autonomic NS releases hormones that target what 3 areas?
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1. Smooth Muscle
2. Endocrine glands 3. Exocrine Glands |
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What is the cardiac sphincter?
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Half above the diaphram and half below and it prevents stomach contents into the esophagus
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What is the thickest layer of the stomach?
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the Antrum
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What marks the endpoint of the stomach?
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The pyloric sphincter
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What are the 3 main functions of the stomach?
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1. Gastric Filling
3. Gastric Mixing 3. Gastric Secretion |
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What are the deep folds of the stomach?
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Rugae
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What do rugae allow for?
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Filling and RECEPTIVE RELAXATION
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Where does peristalsis in the stomach originate?
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In the fundus
-in a group of pacesetter cells |
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When do the pacesetter cells of the fundus reach potential?
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1. The phases of gastric secretion
2. involves the anticipation of food and the presence of food in the stomach |
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Where does gastric mixing occur?
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In the antrum (all peristalsis for mixing and propulsion)
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Where do gastric secretions occur?
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In deep pits in the mucosa called the Onxytic Mucosa
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Describe the mucous secreted by the goblet cells.
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Very Alkaline
-Creates a barrier between the acidic juices of the stomach and the cellular layer of the stomach |
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What do chief cells secrete? Where are they located?
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Pepsinogen that turns into pespin when combined with HCl
-Onxylitic Mucosa |
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What do parietal cells secrete?
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HCl
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What is intrinsic factor needed for?
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B12 absorption
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Enterochromaffin-Like-Cells (ECL) produce what?
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Histamine
-enhances gastric secretion -Has paracrine action: cells only produce enough of these to act locally |
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What cells are produced at the Pyloric Gland Area? What do they produce?
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1. G cells: produce gastin hormone
--increases secretion and motility 2. D cells: produce somatostatin hormone --inhibits secretion and motility |
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How do G and D cells interact?
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They are antagonistic
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What are the 4 phases of controlling gastric secretion and motility?
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1. Interdigestive phase
2. Cephalic phase 3. Gastric phase 4. Intestinal phase |
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What is the interdigestive phase?
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No cue to initiate digestion
-Gastric secretion is controlled by sleep-wake cylce, -lowest in the morning -highest in the evening |
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Describe the Cephalic phase
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Anticipation of eating (secretion and motility)
-Starts the secretion before food hits the stomach -Includes tasting, chewing and swallowing -Controlled by the extrinsic loop |
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What stimulations occur during the cephalic phase?
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Secretion of the stomach through vagal innervation
-chief cells -parietal cells -G cells -parietal cells -ECL cells -stimulates motility in stomach |
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What is the gastric phase?
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When you swallowed food and now it hits your stomach
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What are important triggers of the gastric phase?
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1. Protein
2. Caffeine 3. Alcohol 4. Distension |
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How does the gastric phase effect intrinsic and extrinsic phase?
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1. Intrinsic submucosal plexus: chief cells, parietal cells, G cells
2. Extrinsic: vagal sense the 4 substances and stimulate ENS |
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What is the intestinal phase?
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Triggered by cues to move food away from the stomach into the duodenum
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What specifically happens in the intestinal phase?
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1. brings down secretion and motility
2. gradual process 3. gastric secretion slow down 4. slows down gastric emptying |
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What cues trigger the intestinal phase?
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1. Protein levels in the stomach
2. pH of the stomach more acidic 3. stimulate D cells to release Somatostatin which inhibits parietal, chief and G celss |
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What cues come from the duodenum to trigger gastric emptying? Which are most significant?
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1. Fat
2. acid 3. hypertonicity 4. distention 1 and 2 are most significant |
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What 2 tasks in the duodenum require secretion from accessory organs?
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1. Acid in the duodenum needs to be neutralized
2. fat in the duodenum needs to start to get digested |
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What 2 hormones does the duodenum signal to the pancreas and liver to begin secretions?
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1. CCK
2. Secretin |
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What is the function of CCK?
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Contributes to slow gastric emptying
-increases pancreatic secretion -increases bile secretion (especially concerned with fat digestion |
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List the functions of Secretin.
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Slows gastric acid production
-slows gastric emptying -stimulates pancreas to produce a bicarbonate solution into the duodenum -concerned with what is neutralized as acid |
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What are the 2 exocrine cells of the pancreas?
What is their function? |
1. Acinar cells: when stimulated by CCK, produce all of the digestive enzymes in packages
2. Duct cells: produce bicarbonate solution |
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What are the proteolytic enzymes?
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1. Trypsinogen ---> trypsin
2. Chymotrypsinogen ---> chymotrypsin 3.ProCarboxypeptidase --Carboxypeptidase |
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How do all proteolytic enzymes begin and how are they released?
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They begin in an inactive form and are packaged and released together!
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Where is bile produced>?
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Liver's hepatocytes
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What is the composition of bile?
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Congugated bilirubin
-bile salts -cholesterol -lecithin -waste products |
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What allows bile to emulsify fat?
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It is amphipathic
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What does it mean to emulsify fat?
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Take large droplets of fat into smaller droplets of fat that won't reconverge together
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Where is bile specifically released from?
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the sphincter of Oddi, between the bile duct and the duodenum
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What helps the gallbladder contract?
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CCK
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What type of feedback does the release of bile follow?
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Positive feedback (keeps being released until all the fat is gone)
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What determines the digestion time of meals?
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the fat content.
-More fat, the longer it takes |
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What is the purpose of fat emulsification?
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to increase the SA for lipase digestion to triglycerides
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What section of the SI contracts the fastest?
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The first
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What does each villi have that aids in absorption?
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Their own capillary system
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What makes up the bulk of the products in the LI?
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Mostly waste
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What is the direction of flow in the LI?
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Comes in from SI through ILEOCECAL VALVE --> CECUM--> ASCENDING --> TRANSVERSE --> DESCENDING -->SIGMOID COLON -->RECTUM
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What hormone plays an important role in the stimulation of mass movement in LI?
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Gastrin
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What triggers a defecation reflex?
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Gastrin
-the filling of the rectum with the feces |
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Which sphincter of the LI is voluntary?
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The external
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What are Haustral contractions?
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Mixing movement of large intestine at the haustra
-analagous to segmentation contraction |
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What does fiber do?
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Adds to the bulk of feces (helps it move
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What can too much fiber do?
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Cause osmotic diarrhea
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What stimulates CCK?
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fat content…and to a lesser extent protein
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What is the primary stimulus for secretin release?
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The presence of acid
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