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105 Cards in this Set

  • Front
  • Back
Subdivisions of the Digestive System
1 - Digestive Tract
2 - Accessory organs
Digestive Tract
A tube extending from MOUTH to ANUS. Includes oral cavity, pharynx, esophagus, stomach, small intestine, and large intestine.
Accessory Organs
Includes the teeth, tongue, salivary glands, liver, gallbladder, and pancreas.
Parts of the digestive tract NOT in the peritoneal cavity
Duodenum, pancreas, and parts of the large intestine, retroperitoneal
Relationship to the Peritoneum
On dorsal wall of the abdominal cavity, the parietal peritoneum turns inward and forms a tissue sheet (dorsal mesentery), extending to the digestive tract. Forms the outer covering (serosa) of the stomach and most parts of the intestines.
Describe what's along the lesser curvature of the stomach.
...the serosae of the stomach surfaces meet and continue as a ventral mesentery, the lesser omentum, extending from the stomach to the liver.
Describe what's along the greater curvature of the stomach.
...the serosae form the greater omentum, which hangs loosely over the small intestine like an apron.
The omenta
Omenta have a loosely organized, lacy appearance due partly to many holes in the membranes and partly to an irregular distribution of fatty tissue. May also contain lymphatic tissue.
Four functions of digestive system
1 - Ingestion
2 - Digestion
3 - Absorption
4 - Defecation
3 Principle processes (carrying out the digestive system)
Motility
Secretion
Membrane Transport
Stages of digestion
Mechanical & Chemical
Mechanical Digestion
Cutting and grinding teeth action and the churning contractions of the stomach and small intestine.
Chemical digestion
Solely of hydrolysis reactions that break the dietary macromolecules into their monomers. Carried out by digestive enzymes produced by the salivary glands, stomach, pancreas, and small intestine.
The Mouth
aka oral/buccal cavity
Functions: ingestion, taste and other sensory responses, mastication, chemical digestion, swallowing, speech, and respiration.
Mouth's enclosure
Enclosed by cheeks, lips, palate, and tongue.
Cheeks and Lips
Retain food and push it betwn the teeth for mastication. Important for sucking and blowing actions.
The Lips
Divided into a cutaneous area and a red area, the latter of which gets its color from the tall dermal papillae and the proximity of blood vessels to the surface.
Tongue
Agile. Muscular organ moving food for chewing and swallowing, bears taste receptors, and aids in speech.
Tongue surface
Covered with lingual papillae, most of which have taste buds.
Tongue's body
Attached to the floor of the mouth by the lingual frenulum.
Tongue's Mass
Composed mainly of two groups of lingual muscles made of skeletal tissue.
The Palate
Separates the oral cavity from the nasal cavity, makes it possible to breathe while chewing food.
Hard Palate
Anterior portion. Supported by the palatine process of the maxilla and the palatine bones.
Soft Palate
Posterior to the hard palate.
Conical, medial projection called the uvula.
Teeth
Adult has 32.
16 mandible and maxilla.
Teeth aka dentition.
Teeth Groupings.
Incisors, canines, premolars, molars.
Based on their shape, location, and function.
Alveolus
A socket in which each tooth is embedded. Forms a gomphosis btwn tooth and bone. Lined by a periodontal ligament.
The Gum
Aka gingiva. Covers the alveolar bone. The crown of the tooth is the part that extends above the gum line; the neck is the portion from the margin of the gum to the alveolar bone; and the root is the portion inserted into the alveolus.
Tooth's consistency
Hard, yellowish tissue called dentin. Covered with enamel in the crown and neck and cementum in the root.
Tooth's internal structure
Tooth has a dilated pulp cavity in the crown and a narrow root canal in the root. These spaces are occupied by pulp, which is composed of loose connective tissue, blood and lymphatic vessels, and nerves.
Mastication
1st step in mechanical digestion.
Breaks food into pieces small enough to be swallowed and exposes more surface to the action of digestive enzymes.
Saliva
Moistens the mouth. Digests small amt of starch/fat, cleanses teeth, and inhibits bacterial growth.
Dissolves molecules so they can stimulate taste buds, and moistens food and binds particles together to aid in swallowing; from salivary glands.
Saliva's composition
Hypotonic solution.
97%-99.5% water
Solutes: amylase, lingual lipase, mucus, lysozyme, immunoglobulin A, electrolytes.
Saliva's pH
pH 6.8 - 7
Salivary Glands
Intrinsic.
Located with the oral tissues.
Includes lingual glands embedded in the tongue.
Labial glands on the inner aspect of the lips.
Buccal glands on the cheek's insides.
Secrets small amts of saliva all the time to keep the mouth moist and inhibit bacterial growth.
Salivary Glands II
(Extrinsic Glands)
Outside the oral cavity.
Convey saliva to it through ducts.
Glands include parotid, submandibular, and sublingual.
How much salivation per day?
1.0 - 1.5 L secreted by extrinsic s.g.
Salivation stimulation
Food stimulates tactile, pressure, and taste receptors, which transmit signals to the salivatory nuclei in the medulla oblongata and pons. These nuclei also receive input from higher brain centers so even the odor, sight, or thought of food stimulates salivation.
Salivation (divisions of stimulation)
Salivatory nuclei send autonomic signals: Sympathetic stimulation reduces saliva output, and parasympathetic stimulation causes the production of thinner saliva with more salivary amylase.
Salivary amylase
Begins to digest starch as the food is chewed, while the mucus of saliva binds food particles into a soft, slippery, easily swallowed mass (bolus).
Pharynx
Has a deep layer of longitudinally oriented skeletal muscle and superficial layer of circular skeletal muscle.
Pharynx's circular muscle
Divided into superior, middle, and inferior pharyngeal constrictors, forcing food downward during swallowing.
Pharynx's circular muscle
Divided into superior, middle, and inferior pharyngeal constrictors, forcing food downward during swallowing.
Esophagus
Straight muscular tube extending from the LARYNX to STOMACH at the cardiac orifice.
Esophagus' 5 Layers
1 - Mucosa,
2 - Submucosa
3 - Muscularis Externa
4 - Adventitia
5 - Serosa
Enteric Nervous System
Nervous network regulating the system's motility, secretion, and blood flow for the esophagus, stomach, and intestines.
Inferior End of Esophagus
More constricted than the rest.
Forms a lower esophageal sphincter.
Physiological constriction.
Helps close the cardiac orifice.
Swallowing
Aka deglutition.
Complex action involving over 22 muscles in the mouth, pharynx and esophagus.
Coordinated by the swallowing center, a nucleus in the medulla oblongata and pons.
Swallowing Stages
Buccal phase.
Pharyngeal-esophageal phases
Buccal stage (Swallowing)
Tongue collects food, forms bolus, and pushes it back into the oropharynx. Bolus stimulates tactile receptors and activates the pharyngeal-esophageal phase.
Pharyngeal-esophageal phase
1 - Root of the tongue blocks the oral cavity 2 - Soft palate rises and blocks the nasopharynx, and 3 - the infrahyoid muscles pull larynx up. Epiglottis covers its opening, and vestibular folds close off the airway. Food bolus is driven downward by constriction of the upper, then the middle, and finally the lower pharyngeal constrictors. Bolus entering esophagus stimulates stretch receptors and triggers peristalsis.
In the esophagus, what does the circular muscle behind the bolus do?
It constricts and pushes the bolus downward. Ahead of the bolus, the circular muscles relaxes while the longitudinal muscle contracts.
What is the stomach?
A muscular sac in the upper left abdominal cavity immediately inferior to the diaphragm.
Stomach's function
Primarily as a food storage organ.
Mechanically breaks up food particles, liquefies the food, and begins the chemical digestion of proteins and a small amt of fat, producing a mixture of semidigested food (chyme).
Stomach's capacity
When empty - Volume of 50 mL.
When full - holds up to 4L
Gross Anatomy (Stomach)
J-shaped, with a lesser curvature on its medial margin, and a greater curvature along its lateral margin.
Stomach's 4 Regions
1 - Cardiac
2 - Fundic
3 - Body
4 - Pyloric
Innervation & Circulation (stomach)
Receives parasympathetic and sympathetic stimulation.
Supplied with blood from the celiav artery. All blood leaving the stomach enters the hepatic portal circulation before returning to the heart.
The stomach wall is similar to?
Has tissue layers similar to those of the esophagus, with some variations.
When the stomach is empty it forms what?
The mucosa and submucosa form conspicuous longitudinal wrinkles called rugae.
When the stomach is empty it forms what?
The mucosa and submucosa form conspicuous longitudinal wrinkles called rugae.
What are gastric pits?
Depressions packed within the gastric mucosa of the stomach wall. Cells near the bottom of the pits divide repeatedly, providing a new source of epithelial cells.
What is at the bottom of the gastric pits?
Glands. In the cardiac and pyloric regions, these are called the cardiac and pyloric glands, respectively, and secrete mucus only.
What's in the rest of the stomach?
Gastric glands which have variety of cell types and secretions. (1) Mucous cells. (2) Regenerative cells. (3) Parietal cells. (4) Chief cells. (5) Enteroendocrine cells
Mucous cells secrete what?
Mucus.
Regenerative cells do what?
Divid rapidly and produce a continual supply of new cells
Parietal cells secrete?
Hydrochloric acid and intrinsic factor.
Chief cells secrete?
Rennin and lipase in infancy and pepsinogen throughout life.
Enteroendocrine cells secrete?
Secretes hormones and paracrine messengers that regulate digestion.
Gastric Secretions
Produce 2-3 L of gastric juice daily.
Made of mainly water, hydrochloric acid, and pepsin.
Hydrochloric Acid
Gastric juice has high concentration of hydrochloric acid.
pH as low as 0.8.
HCL and pH
HCL secretion doesn't affect pH of parietal cells that make it b/c H+ pumps out as fast as its generated. Bicarbonate ions are exchanged for chloride ions from the blood plasma, and CL- is pumped into the lumen of the gastric gland. HCL accumulates in the stomach while bicarbonate ions accumulate in the blood.
4 Functions of Stomach Acid
(1) Activates the enzymes pepsin and lingual lipase. (2) It breaks up connective tissues and plant cell walls. (3) It converts ferric ions to ferrous ions. (4) It contributes to nonspecific disease resistance by destroying ingested bacteria and other pathogens.
Intrinsic Factor
Parietal cells also secrete a glycoprotein called intrinsic factor that is essential to the absorption of vitamin B12 by the small intestine.
Intrinsic Factor (2)
The only indispensable function of the stomach.
Pepsin
Several enzymes are secreted as inactive proteins called zymogens. Chief cells secrete the zymogen called pepsinogen,.
Pepsin (2)
Hydrochloric Acid removes some of the amino acids from pepsinogen and converts it to pepsin. The fcxn of pepsin to digest dietary proteins to shorter peptide chains.
Other Enzymes In Infants
Chief cells also secrete gastric lipase and rennin.
Chemical Messengers
Gastric glands have diff kinds of enteroendocrine cells that collectively produce as many as 20 secretions, most of which behave as hormones or paracrine secretions.
Gastrin travels where?
Travels in the bloodstream and stimulates motility of the large intestine and it diffuses it to nearby parietal and chief cells and stimulates the secretion of hydrochloric acid and enzymes.
Gastric Motility: During swallowing what happens?
Signals from the swallowing center of the medulla oblongata stimulate the stomach to relax in prep for the arrival of food.
What is the receptive-relaxation response?
When food enters the stomach, it is stimulated to stretch further.
The stomach shows a rhythm of what?
...Of peristaltic contractions, governed by pacemaker cells in the longitudinal layer of muscle of the greater curvature.
The Antrum
Holds about 30mL of chyme. As peristaltic wave passes down the antrum, it squirts about 3 mL of chyme into the duodenum. Allows only small amts to enter at a time enabling the duodenum to neutralize stomach acid and digest nutrients.
Vomiting
Induced by excessive stomach stretching, psychological stimuli, and chemical irritants. Factors stimulate the emetic center in the Medulla Oblongata, which in turn stimulates the lower esophageal sphincter to relax and the diaphragm and abdominal muscles to contract.
Protein, starch and fat are partially digested where and how?
In the stomach by salivary and gastric enzymes and then passed to the small intestine, where most digestion and nearly all nutrients are absorbed.
Does the stomach absorb ALOT of nutrients?
No; but it does absorb aspirin and some lipid-soluble drugs.
Stomach's protection (3 Ways)
1 - Highly Alkaline mucous coat
2 - Epithelial cells replaced every 3-6 days
3 - Tight junctions betwn epithelial cells prevent gastric juice from seeping between cells and digesting connective tissue.
Gastric Functions 3 stages
Cephalic
Gastric
Intestinal
What's the intestinal phase stimulated by?
Chyme entering the duodenum.
For a short time, enteroendocrin cells secrete intestinal gastrin, which initially enhances gastric secretion and mobility.
In intestinal phase what triggers enterogastric reflex?
Hydrochloric acid, fats, and peptides in the duodenum.
Sympathetic signals inhibit gastric motility and secretion.
Chyme also stimulates what ?
Enteroendocrin cells to release secretin, cholecystokinin, and gastric inhibitory peptide. First 2 hormones stimulate the pancreas and gallbladder, but all 3 suppress gastric secretion and motility.
Small intestine receives what secretions?
Receives chyme from stomach and secretions from pancreas and liver.
Liver Description
Reddish brown gland.
Located inferior to diaphragm in the right hypochondriac and epigastric regions.
Body's largest gland and performs a tremendous variety of fxcns.
Secretion of bile for digestion.
Liver's Gross Anatomy
Four lobes - the right, left, quadrate, and caudate lobes. Gallbladder is on the inferior surface of the liver btwn right and quadrate lobes.
What is the liver's parenchyma?
Consists mostly of hepatocytes arranged in cylinders called hepatic lobules. Lobule = 1mm in diameter and 2 mm long and has a central vein passing through its core.
Liver secretes what?
Bile. Narrow channels = Bile canaliculi, btwn the hepatocytes. Passes from there into the small bile ductules and then into the right and left hepatic ducts. These 2 ducts converge to form the common hepatic duct, which then joins the cystic duct coo=ming from the gallbladder.
Common bile duct is where?
Descends thru lesser omentum and joins the pancreas duct, forming the hepatopancreatic ampulla. Major duodenal papilla on the duodenal wall contains the hepatopancreatic sphincter, which regulates the passage of bile and pancreatic secretion into the duodenum.
How long is the gallbladder?
About 10 cm long.
Liver's Gross Anatomy
Four lobes - the right, left, quadrate, and caudate lobes. Gallbladder is on the inferior surface of the liver btwn right and quadrate lobes.
What happens when bile isn't needed?
The hepatopancreatic sphincter is closed. Then bile fills up the bile duct and spills over into the gallbladder, which absorbs water and stores the bile for later use.
What is the liver's parenchyma?
Consists mostly of hepatocytes arranged in cylinders called hepatic lobules. Lobule = 1mm in diameter and 2 mm long and has a central vein passing through its core.
Liver secretes what?
Bile. Narrow channels = Bile canaliculi, btwn the hepatocytes. Passes from there into the small bile ductules and then into the right and left hepatic ducts. These 2 ducts converge to form the common hepatic duct, which then joins the cystic duct coo=ming from the gallbladder.
Common bile duct is where?
Descends thru lesser omentum and joins the pancreas duct, forming the hepatopancreatic ampulla. Major duodenal papilla on the duodenal wall contains the hepatopancreatic sphincter, which regulates the passage of bile and pancreatic secretion into the duodenum.
How long is the gallbladder?
About 10 cm long.