Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
120 Cards in this Set
- Front
- Back
|
The digestive tract |
Aka the gastrointestinal (GI) tract or alimentary canal A muscular tube that extends from oral cavity to anus and passes through - pharynx - esophagus - stomach - small/large intestines - anus |
|
|
Functions of digestion |
Ingestion Mechanical processing Digestion Secretion Absorption Excretion |
|
|
When does ingestion occur |
When materials enter digestive tract via the mouth |
|
|
What is mechanical processing |
Crushing and shearing that makes material easier to propel along digestive tract |
|
|
What is digestion |
The chemical breakdown if food into small organic fragments for absorption by digestive epithelium |
|
|
What is secretion |
The release of water, acids, enzymes, buffers, and salrs by epithelium of digestive tract and by glandular organs |
|
|
What is absorption |
The movement of organic substrates, electrolytes, vitamins, and water across digestive epithelium into interstitial fluid of digestive tract |
|
|
What is excretion |
Removal of waste products from body fluids |
|
|
2 serous membranes and what they line |
Serosa or visceral peritoneum covers organs within peritoneal cavity Parietal peritoneum lines inner surface of body wall |
|
|
Peritoneal cavity |
Space between the serous membranes Located within the abdominopelvic cavity Secretes peritoneal fluid Allows sliding without friction or irritation |
|
|
What are the mesentaries and what do they do |
Double layer membrane that suspends in peritoneal cavity Provides an access for nerves, blood, and lymphatic vessels Stabilize positions of attached organs Prevent intestines from becoming entagled |
|
|
Lesser omentum does what |
Stabilizes position of stomach Provides access route for blood vessels and other structures entering or leaving liver |
|
|
Where is the greater omentum located |
Extends inferiorly between the body wall and the anterior surface of small intestine Hangs like an apron from lateral and inferior borders of stomach |
|
|
What does adipose tissue in the greater omentum do |
Conforms to shapes of surrounding organs Pads and protects surfaces of abdomen Stores lipid energy reserves |
|
|
What parts of the digestive system are involved in absorption and what increases the surface area for absorption |
Stomach, sma intestine, and most of large intestine are involved (simple columnar epithwlium with goblet cells) Folding increases surface area for absorption (longitudinal folds that disappear as digestive tract fills and permanent transverse folds or plicae) |
|
|
Where are enteroendocrine cells found and what do they do |
Scattered among columnar cells of digestive epithelium Secrete hormones that coordinate activities of the digestive tract and accessory glands |
|
|
Major layers of the digestive tract |
Mucosa Submucosa Muscularis externa Serosa |
|
|
What do parasympathetic and sympathetic digestive innervation do |
Parasympathetic: increases muscle tone and activity, peristaltic and secretion Sympathetic: promotes muscular inhibition and relaxation, closes sphincters |
|
|
What does smooth muscle do along the digestive tract and how are they controlled |
Has rhythmic waves of activity (peristalsis) Controlled by pacesetter cells Moves a bolus |
|
|
What do smooth muscle cells undergo spontaneously |
Spontaneous depolarization that triggers a wave of contraction through entire muscular sheet |
|
|
How does peristaltic motion work |
- Circular muscles contract behind bolus while circular muscles ahead of the bokus relax - Longitudinal muscles ahead of bolus contract shortening adjacent segments - Wave of contraction in circular muscles forces bolus forward |
|
|
Neural mechanisms |
Control - movement if materials along digestive tract - secretary function Motor neurons - control smooth muscle contraction and glandular secretion - located in myenteric plexus |
|
|
How many digestive hormones and what do they effect |
At least 18 hormones that affect - most aspects of digestive function - activities of other systems |
|
|
How are digestive hormones produced |
By enteroendocrine dells in digestive tract |
|
|
Local mechanisms |
- Prostaglandins, histamine, and other chemicals released into interstitial fluid - affect adjacent cells within small segment of digestive tract - coordinating response to changing conditions (variations in local pH, chemical, or physical stimuli) - affect only a portion of the tract |
|
|
Functions of oral cavity |
- sensory analysis of materials before swallowing - mechanical processing through actions of teeth, tongue, and palatal surfaces - lubrication: mixing with mucus and salivary gland secretions - limited digestion of carbohydrates and lipids |
|
|
What is hard palate formed by |
Palatine process of maxillary bones Horizontal plates of palatine bones |
|
|
What is the soft palate and what does it support |
- muscular tissue posterior to hard palate - supports uvula (prevents food from entering pharynx prematurely) |
|
|
Where are Palatine tonsils located |
Located between glossopalatine arch and pharyngopalatine arch |
|
|
4 functions of the tongue |
- mechanical processing: compression, abrasion, and distortion - manipulation: assists in chewing, prepares material for swallowing - sensory analysis: touch, temperature, and taste receptors - secretions: mucins, enzyme lingual lipase |
|
|
Lingual frenulum |
Connects body of tongue to floor of oral cavity |
|
|
What are sublingual glands, what do secretions do, and what do they contain |
- small glands extend into underlying lamina propria - secretions flush tongues epithelium - contain water mucins, enzyme lingual lipase |
|
|
How does lingual lipase work |
Works over a broad pH range (3.0-6.0) Can work in stomach Starts lipid digestion immediately |
|
|
Salivary glands |
3 pairs secrete into oral cavity (parotid, sublingual, submandibular) |
|
|
Where are parotid glands located and what do they produce |
In front of ear Produce enzyme salivary amylase (breaks down starches) |
|
|
Where are sublingual salivary glands and what do they produce |
Covered by mucous membrane on floor of mouth, near tongue Produce mucous secretions (buffer/lubricant) |
|
|
Where are submandibular salivary glands and what did they secrete |
In floor of mouth along inner side of jaw Secrete buffers, glycoproteins (mucins), salivary amylase |
|
|
What controls salivary secretions |
Autonomic nervous system - parasympathetic: large amounts - sympathetic: small amounts |
|
|
How much saliva is produced per day and what does it contain |
- 1 to 1.5 liters each day - contains 99.4% water - 0.6% electrolytes (Na+, Cl-, HCO3-), buffers, glycoproteins (mucins), antibodies, enzymes, waste products |
|
|
Functions of saliva |
- cleans teeth - moistens/lubricates mouth and materials in mouth - dissolving chemicals that stimulate taste buds and provide sensory information - initiate digestion of complex carbohydrates by enzyme salivary amylase and lipids by enzyme lingual lipase |
|
|
Mastication |
To chew food |
|
|
Enamel |
White part of tooth Hardest substance in the body |
|
|
Dentin |
Mineralized matrix similar to that of bone Doesn't contain cells |
|
|
Pulp cavity |
Recieves blood vessels and nerves through thr root canal |
|
|
Gingivae (gums) |
Ridges of oral mucosa Surround base of each tooth on alveolar processes of maxillary/mandible bones |
|
|
Root of tooth |
Alveolus - bony socket where root is located A layer of cemented covers dentin of the root providing protection and anchoring periodontal ligament |
|
|
Root canal |
Narrow tunnel located at root of tooth |
|
|
Neck of tooth |
Marks boundary between root and crown |
|
|
Crown of tooth |
Exposed oprtion of tooth beyond gingiva Dentin covered by layer of enamel |
|
|
Dental arches contain how many types of teeth |
4 (incisors, cupids or canines, bicuspids or premolars, molars) |
|
|
Incisors |
Blade shaped teeth at front of mouth Used for clipping or cutting |
|
|
Cupids or canines |
Conical pointed tip Used for tearing or slashing |
|
|
Bicuspids or premolars |
Flattened crowns Used to crush, mash, grind |
|
|
Molars |
Very large flat crowns with prominent ridges Used for crushing and grinding |
|
|
Primary and secondary dentitions |
During embryonic development, 2 sets of teeth form - primary dentition: deciduous teeth (20) - secondary dentition: permanent teeth (32) |
|
|
Pharynx |
Common passageway for solid food, liquids, and air |
|
|
Swallowing |
Also called deglutition Can be initiated voluntarily but proceeds automatically |
|
|
Esophagus |
Hollow muscular tube About 10 in. Long and 0.8 in. Wide Conveys solid food and liquids to stomach Peristalsis moves food to stomach (lower esophageal sphincter) |
|
|
What are the cardia, fundus, body, and pylorus of the stomach |
Cardia - narrow upper region Fundus - dome shaped, left Body - central portion Pylorus - funnel shaped end |
|
|
2 parts of pylorus |
Pyloric sphincter: regulates flow into small intestine Pyloric glands: secrete mucous |
|
|
Functions of stomach |
- storage of ingested food - mechanical breakdown of ingested food - disruption of chemical bonds in food material (by acids/enzymes, forms chyme) - production of intrinsic factor (glycoprotein required for absorption of vitamin B12 in small intestine) |
|
|
Chyme |
Mixture of secretions and food |
|
|
What is the stomach lined by and what does the lining do |
- simple columnar epithelium lines all portions of stomach - epithelium is a secretary sheet (produces mucus that covers interior surface if the stomach) |
|
|
pH of stomach and what this does |
1.5 - 2.0 Kills microorganisms, denatures, and activates pepsin |
|
|
Gastric pits and where are mucous cells found |
- shallow depressions that open onto the gastric structure - mucous cells at base, or neck, of each gastric pit - actively divide, replacing superficial cells |
|
|
Where are gastric glands and how do they communicate |
In fundus and body of stomach, extend deep into underlying lamina propria Each gastric put communicates with several gastric glands |
|
|
Secretary cells in gastric glands |
Parietal cells Chief cells |
|
|
Parietal cells |
Secrete hydrochloric acid (HCL) - results in alkaline blood due to HCO3- influx - activates pepsinogen to pepin Secretes intrinsic factor for B12 absorption |
|
|
Chief cells |
- most abundant near base of gastric glands - Secretes pepsinogen (inactive proenzyme) - secretes hydrochloric acid (HCl) |
|
|
Regulation of acid and enzyme production |
In gastric mucosa cab be controlled by CNS Regulated by short reflexes of ANS coordinated in wall of stomach Regulated by hormones of digestive tract |
|
|
3 phases of gastric secretion |
Cephalic phase Gastric phase Intestinal phase |
|
|
Cephalic phase of gastric secretion |
Begins when you see, smell, taste, or think of food - directed by CNS - prepares stomach to recieve food - activates parietal and chief cells - G cells release gastrin |
|
|
Gastric phase of gastric secretion |
Begins with arrival of food in stomach - builds on stimulation from cephalic phase -chyme acidifies and increases protein digestion |
|
|
Intestinal phase of gastric secretion |
Begins when chyme first enters small intestine After several hours of mixing contractions - when waves of contraction sweep down length of stomach it inhibits gastric secretion |
|
|
Pepsin |
Performs preliminary digestion of proteins |
|
|
Digestion from saliva |
Amylase - some digestion of carbohydrates Lingual lipase - lipids Both active until pH drops below 4.5 (1-2 hours) |
|
|
Stomach contents as digestion happens |
Become more fluid pH approaches 2.0 Pepsin activity increases Protein disassembly begins |
|
|
What happens to nutrients during digestion in stomach and why isn't digestion complete |
Nutrients are not absorbed - mucous aids in prevention - no transport mechanism - membrane impermeable to water - digestion is only preliminary |
|
|
When are alcohol and aspirin absorbed |
During digestion in the stomach due to their lipid nature |
|
|
Small intestine |
Plays a key role in digestion and absorption of nutrients 90% of nutrient absorption occurs here 21 ft long, 1 inch in diameter From pylori valve to ileocecal valve |
|
|
Duodenum |
Segment of small intestine closest to stomach 25 cm long Mixing bowl that eecieves chyme from stomach and digestive secretions from pancreas and liver Few plicae Small villi |
|
|
Duodenum functions |
Recieve chyme from stomach Neutralize acids before they can damage the absorptive surfaces of small intestine |
|
|
Jejunum |
Middle segment of the small intestine 2.5 meters long |
|
|
The jejunum in the located of most |
Chemical digestion Nutrient absorption - absorbs carbs, lipids, protein, calcium, iron |
|
|
Ileum |
Final segment of small intestine 3.5 meters long Ends with ileocecal valve - to cecum of large intestine |
|
|
Peyers patches |
Lymphoid nodules that protect small intestine from bacteria of large intestine |
|
|
Plicae (plicae circulares) |
Transverse folds/ridges in intestinal lining greatly increasing surface area Permanent features (don't dissappear when small intestine fills) |
|
|
Intestinal villi and what are they covered in |
A series of fingerlike projections in mucosa of small intestine Covered by similar columnar epithelium - covered with microvilli, the "brush border" - increases surface area (with plicae, take surface area from 3.6 ft squared to 2200 ft squared) |
|
|
Brush border enzymes |
Integral membrane proteins On surfaces if intestinal microvilli Break down materials in contact with brush border |
|
|
Enterokinase |
A brush border enzyme Activates pancreatic proenzyme trypsinogen |
|
|
What are intestinal secretions, how much per day, and what do they do |
Watery intestinal juice 1.8 liters/day enter intestinal lumen Moistens chyme Assists in buffering acids Keeps digestive enzymes and products of digestion in solution |
|
|
What is the gastroenteric reflex initiated by, and what does it stimulate, trigger, and allow |
- Initiated by stretch receptors as fills - Stimulates motility and secretions along entire small intestine - Triggers relaxation of ileocecal valve - Allows materials to pass from small intestine into large intestine |
|
|
Pancre a s position and how much pancreatic juice does it produce |
Lies posterior to stomach from duodenum toward spleen 100 mL (1 qt.) Pancreatic juice per day |
|
|
Functions of pancreas |
Endocrine cells: of pancreatic islets secrete insulin and glucagon into bloodstream Exorcize organ: main job is to produce digestive enzymes and buffers delivered to duodenum |
|
|
Pancreatic enzymes and what they break down |
Pancreatic alpha amylase: breaks down starches Pancreatic lipase: breaks down complex lipids Nucleases: break down nucleic acids Proteolytic enzymes: break certain proteins apart |
|
|
Two types of proteolytic enzymes and what they do |
Proteases break large protein complexes (trypsinogen) Peptidases break small peptides into amino acids |
|
|
How is trypsinogen converted to trypsin |
Enterokinase in duodenum converts trypsinogen to trypsin |
|
|
Liver weight, what it does, how many lobes, and how are they divided |
Largest visceral organ (1.5 kg) Performs essential metabolic and synthetic functions 2 major and 2 minor lobes divided by falciform ligament |
|
|
3 functions of liver |
Metabolic regulation Hematological regulation Bile production |
|
|
How does the liver do hematological regulation |
Largest blood reservoir in body Recieves 25% cardiac output Performs hematological regulation functions |
|
|
Hepatocytes |
Liver cells that adjust circulating levels of nutrients through selective absorption and secretion |
|
|
Lipid digestion/absorption |
- Dietary lipids aren't water soluble - Mechanical processing in stomach creates large drops containing lipids - Pancreatic lipase isn't lipid soluble, it interacts only at the surface of liquid droplet |
|
|
Where is bile produced, stored, discharged, and what does it contain |
Produced in lived, stored in gallbladder, and discharged into small intestine Contains buffers and bile salts |
|
|
What do bile salts do |
Break droplets apart (emulsification,) - increases surface area exposed to enzymatic attack - creates tiny emulsion droplets coated either bile salts |
|
|
What is the gallbladder and what does it store |
A pear shaped muscular sac Stores and concentrated bile prior to excretion in duodenum via common vile duct |
|
|
Gallstones |
Crystals of insoluble minerals and salts Form if bile is too concentrated Small stones may be flushed through bile duct and excreted |
|
|
Gallbladder and bile modification |
Full gallbladder contains 40-70 mL bile Bile composition changes in gallbladder - water is reabsorbed - bile salts and solutes become concentrated |
|
|
Large intestine measurements and position |
Almost 5 ft long and 3 ft wide Horseshoe shaped Extends from end of ileum to anus Lies inferior to stomach and liver Frames small intestine Larger diameter and thinner walls than small intestine |
|
|
Functions of large instestine |
Reabsorption of water Compaction of intestinal contents into feces Absorption of important vitamins produced by bacteria Storage of fecal material prior to defecation |
|
|
3 parts of large intestine |
Cecum, colon, rectum |
|
|
Cecum |
Pouchlike first portion of large intestine Recieves material arriving from ileum Stores material and begins compaction Appendix attached |
|
|
Colon |
Largest portion of large intestine - ascending colon - transverse colon - descending colon - Sigmoid colon |
|
|
Rectum |
Forms last 6 inches of digestive tract An expandable organ for temporary storage of feces Fecal material in rectum triggers urge to defecate Anal canal - last 1 inch- exits via the anus |
|
|
Internal anal sphincter |
Circular muscles layer if muscularis externa Has smooth muscle cells not under voluntary control |
|
|
External anal sphincter |
Encircles distal portion of anal canal A ring of skeletal muscle fibers under voluntary control |
|
|
Characteristics of colon |
-Lack of villi -Abundance of goblet cells -Presence distinctive intestinal glands -Mucosa doesn't produce enzymes (provides lubrication for fecal matter) -less than 10% of nutrients absorption occurs in large intestine -Prepares fecal material for ejection from body |
|
|
Types of absorption in large instestinr |
-Reabsorption of water -Reabsorption of bile salts (in cecum, transported in blood to liver) -Absorption of vitamins produced by bacteria (K, Biotin, pantothenic acid) -Absorption of organic wastes |
|
|
What do organic wastes do and what do they generate |
Bacteria break down peptides in fever and generate - ammonia: as soluble as ammonium ions - indole and skatole: nitrogen compounds responsible for odor of feces - hydrogen sulfide: gas that produces rotten egg odor |
|
|
What do bacteria that feed on indigestible carbohydrates (complex polysaccharides) produce |
Flatus or intestinal gas in large intestine |
|
|
Essential nutrients |
Carbohydrates Proteins Lipis Water Electrolytes Vitamins |
