digestive system ch 22

A. name the regions and functions of the pharynx.

(3 regions) nasopharynx, oropharynx and laryngopharynx.

LO12 Describe the anatomy of the intestinal tract and its histological features.

- Duodenum: first 25 cm, final exocrine secretions added to aid in neutralizing chyme and further digestion - Jejunum: ⅖ remaining length, where majority of absorption takes place, brush border enzymes are key - Ileum: last portion, uptake of cholesterol, bile salt, B12, electrolytes, and houses some flora

LO15 explain the regulation of gastric activity by central and local mechanisms.

- Excitatory: autonomic: parasympathetic, physical: stretch and chemical presence, gastrin, histamines - Inhibitory: autonomic: sympathetic, GIP (triggered by fats and carbs), CCK (triggered by fats and proteins), VIP: inhibits gastric acid secretion, secretin (triggered by acidity of chyme), pH 3.0-1.5

LO17 Describe the large intestines histology and role in fecal compaction and explain the defecation reflex.

- Simple columnar epithelium; contains tubular glands to secrete plenty of mucus to aid movement - Use of anal sphincters; under both voluntary and involuntary controls

A. Name and briefly describe an important characteristic of each of the three phases of gastric secretion.

1) cephalic phase - begins when you see, smell, taste or think of food. Directed by the CNS, prepares the stomach to receive food. The neural output proceeds by way of the parasympathetic division of the autonomic nervous system, and the vagus nerves (X) innervate the submucosal plexus of the stomach. Next, postganglionic parasympathetic fibers innervate mucous cells, chief cells, parietal cells, and G cells of the stomach. In response to stimulation gastric juice production accelerates. this phase only lasts minutes. 2) Gastric phase - begins when food arrives in the stomach and builds on the stimulation provided during the cephalic phase. The stimuli that initiate the gastric phase are (1) distension of the stomach (2) increase in the pH of the gastric contents due to dilution of acid during mixing and (3) the presence of undigested food in the stomach, especially proteins and peptides. Lasts about 3-4 hours while the acid and enzymes process the ingested food. During this period, gastrin stimulates contractions in the muscular layer of the stomach and intestinal tract. After the first hour, the material in the stomach is churning. Gastric phase Consists of mechanisms. a. local responses - distension of the gastric wall stimulates the release of histamine in the lamina propria, which bind to receptors on the parietal cells and stimulates acid secretion. b. Neural responses - the stimulation of stretch receptors and chemoreceptors triggers short reflexes coordinated in the submucosal and myenteric plexus. this in turn activates the stomachs secretory cells. The stimulation of the myenteric plexus produces powerful contractions called mixing waves in the muscular layer. c. Hormonal response - Neural stimulation and the presence of peptides and amino acids in chyme stimulate the secretion of the hormone gastrin. Gastrin travels by the bloodstream to the parietal and chief cells, whose increased secretions reduce pH of the gastric juice. In addition, gastrin stimulates gastric motility. 3) Intestinal Phase - gastric secretion begins when chyme first enters small intestine, usually after several hours of mixing contractions. functions: controlling the rate of gastric emptying to ensure that the secretory, digestive, and absorptive functions of the small intestine can proceed with reasonable efficiency. The arrival of chyme in the small intestine also triggers other neural and hormonal events that coordinate the activities of the intestinal tract and the pancreas, liver and gallbladder. Intestinal phase includes mechanisms a. Neural responses - chyme leaving the stomach decreases the distension of the stomach, thereby reducing the stimulation of the stretch receptors. Distension of the duodenum by chyme stimulates receptors and chemoreceptors that trigger enterogastric reflex. This reflex inhibits both gastrin production and contractions and stimulates the contraction of pyloric sphincter, which prevents further discharge of chyme. b. At the same time local reflex at the duodenum stimulates mucus production, which help protect the duodenal lining from the arriving acid and enzymes. c) Hormonal responses - Arrival of lipids and carbohydrates stimulates the secretion of cholecystokinin (CCK) and gastric inhibitory peptide (GIP). A decrease in pH below 4.5 stimulates the secretion of secretin. Partially digested proteins in the duodenum stimulate the secretion of gastrin, which speeds gastric processing.

A. Name the three segments of the small intestine from proximal to distal.

1) duodenum - segment closest to the stomach; "mixing bowl"; receives chyme from the stomach and digestive secretions from the pancreas and liver. mostly in retroperitoneal position and is firmly attached to the posterior body wall. 2) jejunum - segment between the duodenum and ileum, marked by its sharp bend at its beginning. the small intestine reenters the peritoneal cavity, supported by a sheet of mesentery. Bulk of digestion and nutrient absorption occurs here. 3) Ileum - final segment of the small intestine, and the longest. ends at the ileocecal valve, a sphincter that controls the flow of material from the ileum into the cecum of the large intestine.

B. Describe two central reflexes triggered by stimulation of the stretch receptors in the stomach wall.

1) gastroenteric reflex - stimulates motility and secretion along the entire small intestine. 2) gastrolienal reflex - triggers the opening of the ileocecal valve, allowing materials to pass from the small intestine to large intestine.

LO 23 Briefly describe several digestive system disorders.

1) periodontal disease - most common cause for tooth loss, occurs when dental plaque forms in the area between the gums and teeth. Bacterial activity may cause gingivitis, tooth decay, and eventually breakdown of periodontal ligament and surrounding bone. 2) Mumps virus - causes mumps, an infection of the salivary glands. infection occurs in the parotid glands but can also affect other salivary glands and other organs, including gonads and meninges. occurs at 5-9years of age. may cause sterility in males. 3) esophagitis - inflammation of esophagus. results from presence of stomach acids that leak through the weakened esophageal sphincter. backflow or gastro-esophageal reflux is responsible for symptoms of heartburn. 4) Hepatitis - inflammation of liver, caused by alcohol, abuse, drugs, or infection. Cirrhosis a form of hepatitis, characterized by the degeneration of liver cells and their replacement with fibrous connective tissue. the surviving liver cells divide but fibrous tissue prevents reestablishment of normal tissues. liver function declines with other complications. many types of hepatitis most common being A, B and C. the hepatitis virus disrupts liver function by attacking and destroying liver cells. can cause high fever or inflammation called jaundice causing yellowing of the eyes and skin due to bilirubin. 5) If bile becomes too concentrated, crystals of insoluble minerals and salts called gallstones form. Small gallstones are not a problem if they can be flushed through the bile duct and excreted. In cholecystitis the gallstones are so large that they damage the wall of the gallbladder or block the cystic duct or bile duct. In that case, the gallbladder may need to be surgically removed. This removal does not seriously impair digestion, because bile production continues at normal levels. 6) Inflammation of the mucous membrane lining the stomach is called gastritis. This condition may develop after ingesting drugs, including aspirin and alcohol. It may also appear after severe emotional or physical stress, bacterial infection of the gastric wall, or the ingestion of strong chemicals. Gastritis may lead to ulcer formation. A peptic ulcer develops when gastric enzymes and acids erode through the stomach or duodenal lining. Specifically, a peptic ulcer located in the stomach is a gastric ulcer, and one located in the duodenum is a duodenal ulcer. Infection by the bacterium Helicobacter pylori is responsible for over 80 percent of peptic ulcers. Treatment for ulcers involves the administration of drugs, such as cimetidine (Tagamet), that inhibit acid production by gastric glands, combined with antibiotics if Helicobacter pylori is present. 7) Pancreatitis is an inflammation of the pancreas. Factors that may cause this condition include blockage of the excretory ducts by viral infections, and toxic drugs, such as alcohol. Any of these stimuli may injure exocrine cells in a portion of the organ. Lysosomes then activate digestive enzymes within the cells, which begin to break down. In about one-eighth of cases, death results when the process does not stop, and the released lysosomal enzymes destroy the pancreas. 8) Enteritis is inflammation of the intestine (usually the small intestine). Enteritis typically causes watery bowel movements, or diarrhea. One cause of diarrhea due to enteritis is the protozoan Giardia lamblia (shown here). Dysentery is inflammation of the small and large intestines that usually. produces diarrhea containing blood and mucus. Gastroenteritis is inflammation of the stomach. and the intestines due to bacterial, viral, protozoan, or parasitic worm infections. Most of these conditions are prevalent in areas that have poor sanitation and low water quality. 9)Colitis is a general term referring to inflammation of the colon, often involving diarrhea or constipation. Diarrhea results when the lining of the colon is unable to reabsorb water normally, or when so much fluid enters the colon that its water reabsorp-tion capacity is exceeded. Constipation is infrequent bowel movement (or defecation), generally involving dry, hard feces. It results when fecal material moves through the colon so slowly that excessive water reabsorption occurs. 10) Colorectal cancer is the third most common cancer in the United States, affecting both men and women. The death rate has declined over the past 20 years for both men and women. It is most common among persons over 50 years of age. Primary risk factors for colorectal cancer include a diet rich in animal fats and low in fiber. There are also a number of inherited disorders that promote epithelial tumor formation along the intestines. It is believed that most colorectal cancers begin as small, localized tumors, or polyps that grow from the mucosa lining the intestinal wall. For individuals at increased risk because of family history, associated disease, or older age, visual inspection of the intestinal lumen by fiberoptic colonoscopy is prudent. Such examination can find polyps before they develop into cancers. The 5-year survival rate for people whose cancer is found at an early stage and treated immediately is greater than 90 percent.

C. Describe the two positive feedback loops involved in the defecation reflex.

1) short intrinsic myenteric defecation reflex - first loop that triggers a series of peristaltic contractions in the rectum that move feces towards the anus. Mediated by the myenteric plexus in the sigmoid colon and rectum. the internal anal sphincter relaxes. 2) long parasympathetic defecation reflex - spinal reflex coordinated by sacral parasympathetic motor neurons. Stimulates mass movements that push feces toward the rectum from the descending colon and sigmoid colon. further relaxes the internal anal sphincter.

LO 19 Discuss the structure and functions of the salivary glands.

1) sublingual glands - lie under either side of the tongue, covered by the mucous membrane of the floor of the mouth. Produce a mucous secretion that acts as a buffer and lubricant. 2) Submandibular glands - lie along the inner surface of the mandible within the mandibular groove. Cells of the submandibular glands secrete a mixture of buffers, mucin, and salivary amylase, an enzyme that breaks down starches (complex carbohydrates). The gland cells also transport antibodies (IgA) into the saliva to provide additional protection against pathogens in food. 3) Large parotid glands - lie inferior to the zygomatic arch deep to the skin covering the lateral and posterior surface of the mandible. Each gland has an irregular shape, extending from the mastoid process of the temporal bone across the outer surface of the masseter. The parotid glands produce a serous secretion containing large amounts of salivary amylase. The secretions of each parotid gland are drained by a parotid duct, which empties into the oral vestibule at the level of the second upper molar.

C. Describe the major event in each of the three phases of swallowing.

1. buccal phase - begins with the compression of bolus against the hard palate. retraction of the tongue then forces the bolus into the oropharynx and assists in the elevation of the soft palate, sealing off the nasopharynx. voluntary, once the bolus enters the oropharynx, reflex responses are initiated, and the bolus is moved toward the stomach. 2. pharyngeal phase - begins when tactile receptors on the palatal arches and uvula are stimulated, in response motor commands from the swallowing centers in the medullar oblongata then direct a coordinated pattern of muscle contraction in the pharyngeal muscles. elevation of the larynx and folding of the epiglottis results from contractions of the pharyngeal muscles while the palatal muscles elevate the uvula and soft palate to block the entrance to the nasopharynx. phalangeal constrictors then force the bolus through the pharynx, past the closed glottis and into the esophagus. 3. esophageal phase - begins as contraction of the pharyngeal muscles forces the bolus through the entrance to the esophagus, once in the esophagus, the bolus is pushed toward the stomach by peristalsis. the approach of the bolus triggers the opening of the lower esophageal sphincter, and the bolus then continuous into the stomach. for a typical bolus, the entire trip takes about 9 seconds. liquids may travel faster, flowing ahead of peristaltic contractions with the assistance of gravity. a dry or poorly lubricated bolus travels much more slowly and a series of local reflexes called secondary peristaltic waves may be required to push it all the way to the stomach.

A. Name the four major regions of the stomach in order from is junction with the esophagus to the small intestine.

1. fundus - the portion of the stomach that is superior to the junction between the stomach and the esophagus. contacts the inferior posterior surface of the diaphragm. 2. cardia - superior, medial portion of the stomach within 3cm of the junction between the stomach and the esophagus. contains abundant mucous glands whose secretions coat the junction with the esophagus and help protect that tube from the acid and enzymes of the stomach. 3. body - area of the stomach between the fundus and the curve of the J. largest region; the body functions as a mixing bowl for ingested food and secretions produced in the stomach. 4. pyloric part - forms the sharp curve of the J. AS mixing movements occur during digestion, the pyloric part frequently changes shape.

LO7 Describe the types of teeth and differentiate between deciduous teeth and permanent teeth.

1. incisors - blade shaped teeth located at the front of the mouth, useful for clipping and cutting. have single root. 2. canines - conical, sharp ridgeline and a pointed tip. tearing or slashing. single root. 3. premolars - flattened crowns with prominent ridges. crush mash, grind. one or two roots. 4. molars - large, flattened crows with prominent ridges - crushing and grinding. in upper jaw have three roots, in lower haw have two roots. deciduous teeth are "baby teeth" typically 20 of them. permanent teeth are "adult teeth" typically 32 of them.

B. Cite the major mechanisms that regulate and control digestive activities.

1. local factors - primary stimulus, include changes in ph. of contents of the lumen, physical distortion of the wall of the digestive tract, or the presence of chemicals - either specific nutrients or chemical messengers released by cells of the mucosa. 2. neural control mechanisms - include both short and long myenteric reflexes that result in peristalsis and segmentation. short reflexes are triggered by chemoreceptors or stretch receptors in the walls of the digestive tract; the controlling neurons are located in the myenteric plexus. long reflexes involving interneurons and motor neurons in the CNS provide a higher level of control over digestive and glandular activities. generally controlling large- scale peristalsis. long reflexes may involve parasympathetic motor fibers in the glossopharyngeal (IX) vagus (X) or pelvic nerves that synapse in the myenteric plexus. 3. hormonal control mechanisms - 18 hormones that affect almost every aspect of the digestive function, and some affect other activities of other systems. these hormones are peptides produced by enteroendocrine cells.

B. name the four layers of the digestive tract beginning from the lumen of the digestive tract.

1. mucosa - inner lining, mucous membrane consisting of a moistened epithelium by glandular secretions, and a lamina propria of areolar tissue. 2. submucosa - surrounds the mucosa, dense irregular connective tissue. Has large blood vessels and lymphatic vessels and in some regions contained exocrine glands that secrete buffers and enzymes into the lumen of the digestive tract. 3. muscular layer - dominated by smooth muscle cells in two layers. inner layer and outer longitudinal layer. play essential role in mechanical processing and in moving materials along the digestive tract. 4. serosa - visceral peritoneum layer that covers along most of the muscular layer portions of the digestive tract within the peritoneal cavity. not found in the oral cavity, pharynx, esophagus, and rectum, instead covered by a dense network of collagen fibers that forms a sheath known as an adventitia, that is firmly attaches the digestive tract to adjacent structures.

LO5 name the structures and primary functions of the digestive tract organs.

1. oral cavity (mouth) - mechanical digestion with accessory organs (teeth and tongue) moistening, mixing with salivary secretions. 2. pharynx- muscular propulsion of materials into the esophagus. 3. esophagus - transport of materials to the stomach. 4. stomach - chemical breakdown of materials by acid and enzymes; mechanical digestion through muscular contractions. 5. small intestine - enzymatic digestion and absorption of water, organic substrates, vitamins and ions. 6. large intestine - dehydration and compaction of indigestible materials in preparation for elimination.

C. Does a high-fat meal raise or low the level of cholecystokinin (CCK) in the blood?

A high-fat meal raises the cholecystokinin (CCK) level in the blood.

LO 21 Describe the histological features of liver tissue.

Each lobule is roughly 1 mm in diameter. Liver cells, called hepatocytes (HEP-a-tō-sīts), within these lobules adjust circulating levels of nutrients through selective absorption and secretion. In cross section, a typical liver lobule has a hexagonal shape and is surrounded by six portal triads, one at each corner of the lobule.

LO4. Explain the process by which materials move through the digestive tract.

Food enters the digestive tract as a moist, compact mass, known as a bolus. The circular muscles contract behind the bolus, the longitudinal muscles contract ahead of the bolus. A wave of contraction in circular muscle layer forces bolus forward - this contraction is known as peristalsis. the bolus then undergoes segmentation that occurs in most areas of the small intestines and portions of the large intestines. cycles of contraction churn and segment the bolus mixing the contents with intestinal secretions. This rhythmic cycle does not push materials in any one direction along the tract.

C. What bacterium is responsible for most peptic ulcers?

Helicobacter pylori

A. Define hepatitis.

Inflammation of the liver that can be caused by bacteria, viruses, protozoa, helminths, chemicals, or drugs.

C. explain the function of lacteals.

Lacteals are lymphatic capillaries in the intestinal villi that transport materials that cannot enter blood. capillaries, such as absorbed fatty acids combined with proteins.

A. Name the three pairs of salivary glands.

Sublingual glands, submandibular glands, parotid glands.

LO 22 Describe the structure, functions and regulatory activities of the gallbladder.

The gallbladder is a hollow, pear-shaped organ that stores and concentrates bile prior to its ejection into the small intestine. This muscular sac is located in a recess in the posterior surface of the liver's right lobe. The gallbladder is divided into three regions: the fundus, the body, and the neck

B. Describe the anatomy of the interstitial mucosa.

The intestinal mucosa has transverse folds called circular folds (plicae circulares) and small projections called intestinal villi. Pockets called intestinal glands are lined by goblet, epithelial, stem, and paneth cells.

B. Define hemorrhoids.

The lamina propria and submucosa of the distal portion of the rectum contain a network of veins. If venous pressures there rise too high because of straining during defecation or pregnancy, the veins can become distended.

A. How does digestion occur in the large intestine?

The mucosa of the large intestine does not produce enzymes. any digestion that occurs results from enzymes introduced into the small intestine or from bacterial action. The mucus lubricates the feces as it becomes drier and more compact.

LO2 describe the functional histology of the digestive tract.

The mucosal epithelium is highly differentiated along the several regions of the GI tract. At the upper and lower ends of the tract, the epithelium is protective, stratified squamous. This protective epithelium is partially keratinized on the hard palate and gums and on the tips of filiform papillae of the tongue. Elsewhere in the oral cavity, esophagus, and anal canal the epithelium is non-keratinized. Along the lining of the stomach, small intestine, and colon, the epithelium is simple columnar. Each region contains certain specialized cell types which are adapted to carry out the region's characteristic functions of secretion and absorption.

LO 23 Describe the structure functions, and regulatory activities of the pancreas.

The pancreas is an elongated gland located deep within the abdomen, tucked in between the stomach and the spine. One end of the pancreas is wider than the other and is called the head: It sits within the curve of the duodenum (the first part of the small intestine) and is divided into two parts: the head proper and the uncinate process. Much like a comma lying on its side, the pancreas extends slightly upward, becoming narrower and narrower. It is divided into areas referred to as the neck, the body, and, finally, the tail, which is located near the spleen. Two types of gland comprise the pancreas, each with very different but vital functions. The exocrine gland, which runs the entire length of the pancreas, secretes digestive enzymes. The endocrine portion of the pancreas is made up of groups of cells call the islets of Langerhans. There are three types of cells in the islets, each of which secretes different hormones that help to regulate the amount of sugar in the bloodstream. function: The pancreas plays key roles in two important functions in the body—digestion and blood sugar control. These functions are performed independently.

A. What is the primary digestive function of the pancreas?

The pancreas produces pancreatic juice that contains buffers and several digestive enzymes necessary for the breakdown of starches, lipids, nucleic acids, and proteins.

LO 18 Describe the functions of the accessory organs of the digestive system.

The salivary glands and pancreas produce and store enzymes and buffers that are essential to normal digestive function. In addition to their roles in digestion, the salivary glands, liver, and pancreas have vital metabolic and endocrine functions. 1) Salivary glands - 3 major pairs of salivary glands produce secretions that contain mucin and enzymes. 2) Gallbladder - stores and concentrates bile secreted by the liver. 3) Pancreas - exocrine cells secrete buffers and digestive enzymes; endocrine cells secrete insulin, glucagon, pancreatic polypeptide (PP) and GH-IH. 4) Liver - has almost 200 known functions. • Synthesizing and secreting bile • Storing glycogen and lipids • Maintaining normal concentrations of glucose, amino acids, and fatty acids in the bloodstream • Synthesizing and interconverting nutrient types (such as the conversion of carbohydrates to lipids) • Synthesizing and releasing cholesterol bound to transport proteins • Inactivating toxins • Storing iron • Storing fat-soluble vitamins Other Major Functions • Synthesizing plasma proteins • Synthesizing clotting factors • Phagocytizing damaged red blood cells (by stellate macrophages) • Storing blood • Absorbing and breaking down circulating hormones and immunoglobulins • Absorbing and inactivating lipid-soluble drugs

A. What is the function of the salivary glands?

The salivary glands produce saliva, which keeps the mouth and other parts of the digestive system moist.

D. Which pair of salivary glands secretes substances that reduce oral bacteria populations?

The submandibular glands secrete substances (antibodies and lysozyme) that reduce oral bacteria populations.

A. define ingestion.

The taking in of substances into the body through the mouth

C. Describe the alkaline tide.

When gastric glands are actively secreting, enough bicarbonate ions enter the bloodstream to increase the pH of the blood significantly. (Sudden influx of bicarbonate)

A. Define hepatocyte.

a liver cell, found in a liver lobule. adjust circulating levels of nutrients through selective absorption and secretion. The hepatocytes in a liver lobule form a series of irregular plates arranged like the spokes of a wheel. The plates are only one cell thick, and exposed hepatocyte surfaces are covered with short microvilli. The plates of hepatocytes are separated by liver sinusoids, blood vessels that lack a basement membrane but otherwise resemble large fenestrated capillaries.

C. Why can smooth muscle contract over a wider range of resting lengths than skeletal muscle.

actin and myosin filaments are more loosely organized in smooth muscle. a stretched smooth muscle soon adapts to its new length and retains the ability to contract on demand, this function is known as plasticity.

D. A traumatic injury to the umbilical region could affect which segments of the small intestine?

all three segments of the small intestines.

B. Identify the four regions of the colon.

ascending colon, transverse colon, descending colon, sigmoid colon.

A. which other systems work with the digestive system to support the cells and tissues of the human body.

cardiovascular system, urinary system and respiratory system.

B. Describe the muscular layer of the esophagus.

comparable to the other portions of the digestive tract, however shape of lumen and the structure of muscular layers are unique. No serosa but an adventitia of connective tissue outside the muscular layer anchors the esophagus to the posterior body wall. mucosa and submucosa have large folds that allow for expansion during the passage of large bolus. muscle tone in the walls keep the lumen closed except for when you swallow.

A. Name the three main parts of a typical tooth.

crown, neck, root.

C. Describe the function of the large intestine.

dehydration and compaction of indigestible materials in preparation for elimination.

LO 13 Describe the anatomy and physiology of the small intestine.

divided into the duodenum, jejunum, and ileum, plays key role in nutrient digestion and absorption (about 90%) duodenum - has few circular folds and small villi. primary function is to receive chyme from stomach and neutralize acids before they can damage the absorptive surfaces of the small intestine. submucosa is dominated by duodenal glands that produce mucous secretions. jejunum - numerous circular folds and abundant in very long villi. ileum - fewer circular folds than the jejunum and they disappear distally. villi are stumpy. submucosa contains aggregated lymphoid nodules.

LO 9 Explain the embryonic development of the mesenteries and describe the mesenteries that remain in adulthood.

during embryonic development, the digestive tract and accessory organs are enclosed by the peritoneal cavity and suspended by dorsal and ventral mesenteries. the ventral mesentery later disappears along most of the digestive tract, remaining in only two places: between the stomach and the liver and between the liver and the anterior abdominal wall. As the digestive tract elongates the position of the mesentery's changes. Some segments of the tract contact the posterior wall and become fixed in position. As the small intestine coils and increases in length, segments of the mesentery proper come into contact and fuse together. the transverse colon and a small section near the end of the large intestine are suspended by remnants of the original mesocolon. The mesentery associated with the initial portion of the small intestine and the pancreas fuses with the posterior abdominal wall, locking those structures in a retroperitoneal position.

C. Describe enteroendocrine cells.

endocrine cells in the epithelium of the digestive tract that produce peptide hormones that affect digestive function and other activities of other systems.

C. Define stellate macrophages and indicate their functions.

engulf pathogens, cell debris and damaged blood cells. Also store iron, some lipids and heavy metals (tin and mercury) that are absorbed by the digestive tract.

C. Explain the significance of peritoneal fluid.

essential lubrication.

B. Distinguish between the exocrine and endocrine secretions of the pancreas.

exocrine cells secrete buffers and digestive enzymes; endocrine cells secrete insulin, glucagon, pancreatic polypeptide (PP) and GH-IH.

B. What structure marks the division between the left lobe and right lobe of the liver?

falciform ligament.

LO11 Describe the anatomy of the stomach relating to its role in digestion and absorption.

gastric glands - secrete mucus and hormones involved in the coordination and control of digestive activity. mucosa, submucosa, muscular layer, serosa. The stomach has four major functions: (1) temporary storage of ingested food, (2) mechanical digestion of ingested food, (3) chemical digestion of food through the action of acid and enzymes, and (4) production of intrinsic factor.

A. Name the major hormones that regulate digestive activities.

gastrin, secretin, gastric inhibitory peptide (GIP), cholecystokinin (CCK), vasoactive intestinal peptide (VIP), and enterocrinin.

B. name the structure that forms the roof of the mouth.

hard palate

B. Trace a drop of bile from the hepatic ducts to the duodenal lumen.

hepatic ducts - common hepatic duct - bile duct - duodenal ampulla and papilla - duodenal lumen

C. Name the lobes of the liver.

left lobe, caudate lobe, right lobe and quadrate lobe.

LO 20 Describe the anatomy and location of the liver and gallbladder.

liver - large organ found in the upper right quadrant of the abdomen. It is a multifunctional accessory organ of the gastrointestinal tract and performs several essential functions such as detoxification, protein synthesis, bile production and nutrient storage to name only a few. It is the largest gland in the human body, weighing approximately 1.5 kilograms. It works synchronously with many other organs and contributes to the maintenance of basic homeostatic mechanisms. The liver is completely covered by visceral peritoneum, with the exception of the bare area, which is where the liver is in contact with the diaphragm gallbladder - small hollow intraperitoneal organ. It is located on the visceral surface of the liver, between the right and quadrate liver lobes. The superior part of the duodenum, hepatic flexure and proximal transverse colon, are posteriorly related to it. There are three anatomical parts of the gallbladder. From lateral to medial these are: 1. Fundus which points inferoanteriorly. It projects onto the anterior abdominal wall at the intersection of the right 9th rib and the lateral margin of the rectus abdominis muscle. 2. Body which lies in the gallbladder fossa of the liver. 3. Neck (infundibulum) with spiral mucosal folds

A. Describe the outer covering of the liver.

liver is wrapped in a tough fibrous capsule and is covered by a layer of visceral peritoneum.

LO1. name the major and accessory organs of the digestive system.

major organs - oral cavity (mouth), pharynx, esophagus, stomach, small intestine, large intestine. accessory organs - teeth, tongue, salivary glands, liver, gallbladder, pancreas.

B. distinguish between chemical digestion and absorption.

mechanical digestive - involves crushing and shearing ingested solids and then propelling them along the digestive tract. this includes tearing and, mashing by the teeth and compressing by the tongue, swirling, mixing and churning motions of the stomach and intestines. chemical digestion - chemical and enzymatic breakdown of food into substances that can be absorbed by the digestive epithelium.

A. Name the layers of the small intestine from superficial to deep.

mucosa, submucosa, muscular layer, serosa.

B. What anatomical feature of the stomach allows the organ to form chyme?

muscular layer - includes an inner, oblique layer of smooth muscle. This additional layer of smooth muscle strengthens the stomach wall and assists in mixing and churning to form chyme.

B. Describe a portal triad.

or portal area, contains three structures: (1) an interlobular vein, (2) an interlobular artery, and (3) an interlobular bile duct. Branches from the arteries and veins of each portal triad deliver blood to the liver sinusoids, or hepatic sinusoids, of adjacent liver lobules.

B. starting at the mouth, identify the major organs of the digestive system.

oral cavity (mouth), pharynx, esophagus, stomach, small intestine, large intestine.

A. Which is more efficient in propelling intestinal contents along the digestive tract: peristalsis or segmentation. why?

peristalsis, because this is a forceful contraction where segmentation is just churning and mixing of the bolus.

LO8 Describe the anatomy and functions of the pharynx and esophagus and explain the swallowing process.

pharynx (throat) - common passageway for food, liquids and air. (3 regions) nasopharynx, oropharynx and laryngopharynx. esophagus - hollow muscular tube; actively moves food and liquids to the stomach. swallowing process (deglutition) - buccal phase, pharyngeal phase, esophageal phase,

A. Define emulsification.

physical process of breaking up large fat globules into smaller globules, thereby increasing the surface area that enzymes can use to digest the fat.

C. Describe mass movements.

powerful peristaltic contractions that occur a few times each day in response to distension of the stomach and duodenum. These contractions begin at the transverse colon and push materials along the distal portion of the large intestine.

LO 14 Discuss the major digestive hormones and their primary effects.

produced by the duodenum 1)Gastrin - secreted by G cells in the pyloric antrum and enteroendocrine cells in the duodenum. secretes gastrin when stimulated by the vagus nerves when food arrives in the stomach. Duodenal cells release gastrin when they are exposed to large quantities of incompletely digested proteins. The function of the gastric are to increase stomach motility and stimulating gastric acid and enzyme production. 2) Secretin - released when chyme arrives in the duodenum. primary effect is an increase in the secretion of buffers by the pancreas, which increase pH of chyme. secondary effects, stimulates secretion of bile by the liver and reduces gastric motility and gastric secretory rates. 3) Gastric Inhibitory peptide (GIP) - secreted when fats and carbohydrates (especially glucose) enter the small intestine. inhibition of gastric activity is accompanied by the stimulation of insulin release at the pancreatic islets. GIP secondary effects, stimulating submucosal duodenal gland activity, stimulating lipid synthesis in adipose tissue, and increasing glucose use by skeletal muscles. 4) Cholecystokinin (CCK) - secreted when chyme arrives in the duodenum, especially when it contains li[ids and partially digested proteins. In the pancreas CCK accelerates the production of secretion of all types of digestive enzymes. Causes relaxation of the hepatopancreatic sphincter and contraction of the gallbladder, resulting in the ejection of bile and pancreatic juice into the duodenum. Thus, the net effects of CCK are to increase the secretion of pancreatic enzymes and to push pancreatic secretions and bile into the duodenum. The presence of high CCK in high concentrations has two additional effects: it inhibits gastric activity and it appears to have CNS effects that reduce the sensation of hunger. 5) Vasoactive intestinal peptide (VIP) - stimulates the secretion of intestinal glands, dilates regional capillaries, and inhibits acid production in the stomach. by dilating capillaries in active areas of the intestinal tract, VIP produces an efficient mechanism for removing absorbed nutrients. 6) Enterocrinin - released by enteroendocrine cells of the duodenum in response to stimulation by the vagus nerves before chyme reaches the pyloric sphincter and also when chyme enters the duodenum. stimulates production of alkaline mucus by the duodenal submucosal glands, which protects the intestine from acidic chyme.

A. Explain the significance the alkaline mucous layer lining the interior surface of the stomach.

protects the epithelial cells against the acid and enzymes in the gastric lumen.

B. identify the segment of the small intestine found within the epigastric region.

proximal portion of the duodenum.

Name the major functions of the large intestine.

reabsorbing water and compacting material into feces, absorbing vitamins, and storing fecal material.

C. What is the primary function of the duodenum?

receives chyme from the stomach and digestive secretions from the pancreas and liver.

B. What is the function of the lesser omentum?

remanent of the ventral mesentery between the stomach and the liver.

A. What is the falciform ligament?

remnant of the ventral mesentery between the liver and the anterior wall of the peritoneal cavity.

C. Describe the lining of the stomach.

rugae - prominent but temporary mucosal folds that allow the gastric lumen to expand. as the stomach fills, the rugae gradually flatten out until, at maximum distension, they almost disappear.

LO 6 describe the anatomy of the oral cavity and discuss the functions of its structures.

sagittal view hard plate - formed by the palatine processes of the maxillary bones and the horizontal plates of the palatine bones. soft palate - muscular; lies posterior to the hard palate. uvula - dangling process in the posterior margin of the soft palate, helps prevent food from entering the pharynx prematurely and swings upwards during swallowing to prevent food from entering the nasopharynx. palatine tonsils - lies on either side of the entrance to the oropharynx. root of the tongue - fixed and projects into the oropharynx. lingual tonsils - embedded in the root of the tongue. The floor of the mouth inferior to the tongue receives extra support from the geniohyoid and mylohyoid. body of the tongue - is a muscular organ that forms part of the oral cavity floor. The mucosae of the cheeks - or lateral walls of the oral cavity, are supported by pads of fat and the buccinator. Anteriorly, the mucosa of each cheek is continuous with that. of the lips, or labia. anterior view oral vestibule - the space between the cheeks (or lips) and the teeth. frenulum of upper lip - attaches the gums to the upper lip. frenulum of tongue, or lingual frenulum - connects the body of the tongue to the floor of the oral cavity. frenulum of lower lip - attaches the gums to the lower lip. gingivae or gums - are ridges of oral mucosa that surround the base of each tooth on the alveolar processes of the maxillary bones and mandible. In most regions, the gingivae are firmly, bound to the periostea of the underlying bones. tongue - manipulates materials inside the mouth and may occasion-ally be used to bring foods into the oral cavity. fauces - the space between the oral cavity and the oropharynx. (The root of the tongue forms the inferior margin.) palatoglossal arch - anterior; extends between the soft palate and the base of the tongue. palatopharyngeal arch - posterior; extends from the soft palate to the pharyngeal wall. a palatine tonsil lies between the palatoglossal and palatopharyngeal arches on each side.

B. What is the function of parietal cells?

secrete intrinsic factor, glycoprotein that helps absorb vitamin B12 across the intestinal lining, necessary for erythropoiesis. also secrete hydrochloric acid.

LO 10 Describe the anatomy of the stomach and its histological features.

shape is highly variable. when empty, the stomach resembles a muscular tube with a narrow, constricted lumen. when full, it can contain 1-1.5 liters of material. that material, which consists of food combines with saliva and the secretion of the gastric glands is a viscous, highly acidic, soupy mixture called chyme. The human stomach is subdivided into four regions: the fundus, an expanded area curving up above the cardiac opening (the opening from the stomach into the esophagus); the body, or intermediate region, the central and largest portion; the antrum, the lowermost, somewhat funnel-shaped portion of the stomach; and the pylorus, a narrowing where the stomach joins the small intestine.

A. what is the importance of the mesenteries?

sheets consisting of two layers of serous membrane separated by areolar connective tissue. The areolar tissue between the mesothelial surfaces provides a route to and from the digestive tract for blood vessels, nerves, and lymphatic vessels. Also stabilize the positions of the attached organs, preventing the intestines from becoming entangles during digestive movements.

B. identify the structural characteristics of smooth muscle fibers.

smooth muscle fiber has no T tubules, and the sarcoplasmic reticulum forms a loose network throughout the sarcoplasm. smooth muscle cells also lack myofibrils and sarcomeres, as a result this tissue has no striations and is called nonstriated muscle. thin filaments are anchored to dense bodies.

B. Damage to the parotid glands would affect the digestion of which nutrient?

starches (complex carbohydrates)

D. what effects might a shortened frenulum of tongue cause?

sticking out the tongue. breastfeeding and learning to speak in toddlers.

A. the oral cavity is lined by which type of epithelium?

stratified squamous epithelium.

LO3 Describe the structural and functional features of smooth muscle tissue.

structure - relatively long and slender ranging from 5 to 10 nm in diameter and 30 to 200nm in length. where layers are formed the cells are aligned parallel to one another. In the digestive tract, there is inner circular layer where the muscular layers look like round balls and a longitudinal layer where they look like long spindles. functions- form sheets, bundles or sheaths around other tissues in almost every organ. around blood vessels regulate blood flow through vital organs. In the digestive and urinary systems, smooth muscle sphincters regulate the movement of materials along internal passageways.

C. Which pair of salivary glands contributes most to saliva production?

submandibular glands (70%)

C. compare the submucosal neural plexus with the myenteric plexus.

submucosal neural plexus - nerve network that contains sensory neurons parasympathetic ganglionic neurons, and sympathetic postganglionic fibers that innervate the mucosa and submucosa. myenteric plexus - network of parasympathetic ganglia, sensory neurons, interneurons, and sympathetic postganglionic fibers lies sandwiched between the circular and longitudinal muscle layers. the myenteric plexus and the submucosal plexus contain neurons of the enteric nervous system (ENS) and most digestive activities are locally controlled. in general, parasympathetic stimulation increases muscle tone and activity: sympathetic stimulating decrease muscle tone and activity.

C. list the accessory organs of the digestive system.

teeth, tongue, salivary glands, liver, gallbladder, pancreas.

D. What is the function of the gallbladder?

temporarily stores bile produced by the liver.

B. Describe cholecytisis.

the gallbladder becomes inflamed, the gallstones are so large that they damage the wall of the gallbladder or block the cystic duct or bile duct

LO 16 Describe the gross anatomy of the three segments of the large intestine.

the large intestine consists of three segments: the cecum, the colon, and the rectum. 1) Colon - larger diameter and thinner wall than small intestine. subsided into four regions. ascending and descending colon are retroperitoneal and firmly attached to the abdominal wall. Transverse colon and sigmoid colon are suspended by remnants of the embryonic mesocolon. 2) Cecum - Material arriving from the ileum first enters an expanded pouch called the cecum. The cecum collects and stores materials from the ileum and begins the process of compaction (the forming of feces by compression). 3) forms the last 15 cm (6 in.) of the digestive tract. It is an expand-able organ for the temporary storage of feces. The movement of fecal material into the rectum triggers the urge to defecate.

C. Which accessory organ of the digestive system is responsible for almost 200 known functions?

the liver.

B. How would he pH of the intestinal contents be affected if the small intestine did not produce secretin?

the pH of the intestinal contents would be lower (more acidic) than normal. Secretin stimulates the pancreas to release a fluid high in buffers that neutralizes the acidic chyme entering the duodenum from the stomach.

C. Describe the location of the fauces.

the superior margin is formed by the ridge that connects the more anterior palatoglossal arch with the uvula.

A. describe the orientation of smooth muscle fibers in the muscular layer of the digestive tract.

where layers are formed the cells are aligned parallel to one another. In the digestive tract, there is inner circular layer where the muscular layers look like round balls and a longitudinal layer where they look like long spindles.

B. What is the name sometimes given to the third set of molars.

wisdom teeth.

C. Why might severing the branches of vagus nerves that supply the stomach provide relief for a person who suffers from chronic gastric ulcers (sores on the stomach lining)?

would interrupt parasympathetic stimulation of gastric secretions, and the consequent reduction in acid secretions would provide some relief from the pain of gastric ulcers.