Week 15: Digestive System Physiology

Besides the nurse's "bender" comment, and Mrs. Fender's social history, Tim suspects alcohol abuse based on many of his physical exam findings. Name at least three signs and/or symptoms that point to alcoholism, and briefly explain why each sign/symptom may occur.

Ascites: ascites is an abnormal fluid buildup inside of the abdomen. this is a pattern shown in people who abuse alcohol. Hepatomegaly: a condition of having a large liver. The liver takes care of poisons and alcohol and breaking them down. People who abuse alcohol show high ratings of enlarged livers (due to overexposure of alcohol in the liver). Neurological changes: structural, or biochemical abnormalities in the brain. to those who abuse alcohol show major neurological changes in their brains.

Which of the following is not a common risk factor for acid reflux disease?

sitting upright after a meal

Absorption of nutrients primarily occurs in the __________.

small intestine

Which function below is NOT carried out by the liver? -manufacturing and secreting insulin -storing glucose as glycogen -producing bile as a result of blood detoxification -transaminating and deaminating amino acids

manufacturing and secreting insulin The pancreas, not the liver, manufactures and secretes insulin. The liver stores glycogen, produces bile, and has the necessary enzymes to transaminate and deaminate amino acids.

Mrs. Fender's jaundice is caused by the accumulation of bilirubin in her blood and tissues. What is the normal fate of bilirubin, and what role does the liver play? Explain how Mrs. Fender's cirrhosis is related to her jaundice.

Hemoglobin from worn-out erythrocytes is broken down into heme and iron. The iron is recycled, and the heme is further degraded into bilirubin, bound to albumin, and carried to the liver. The liver removes it from the blood and excretes it into the intestines as bile. When the liver is damaged (as in cirrhosis or hepatitis), bilirubin, which is a yellow pigment, spills over into tissues and the blood, thus giving tissues, blood, and the overlying skin a yellowish appearance, especially the lighter skin of the palms of the hands. Jaundice is also more apparent in the white sclera of the eyes.

H. pylori weakens the duodenal mucosa making it more susceptible to gastric juice. Besides the high acidity, why are the contents of gastric juice so hostile to the exposed duodenal wall?

Along with HCl, gastric juice contains pepsin, an enzyme that digests protein in the acidic environment of the stomach. Typically, pepsin is inactivated by the higher pH of the pancreatic juices. However, when excessive amounts of acid enter the duodenum and/or H. pylori degrades the duodenal mucosa, pepsin can further digest the tissue of the duodenal wall, creating an ulcer.

The structures in the epigastric region share a common nerve supply. Can you name the specific cranial nerve that serves this region and the part of the nervous system to which it belongs?

Cranial nerve X, the vagus nerve, carries visceral sensory information from receptors located in the abdominal organs.

Mr. Volpe's epigastric pain, emanating from his duodenal ulcer, is relieved immediately by food, but returns 2-4 hours later. Which of the following explanations is most likely?

It takes 2-4 hours for the acidic chyme to move from the stomach into the duodenum.

This patient appears to have a problem with the hepatobiliary system −− the liver and gall bladder −− leading to a buildup of bilirubin in her blood. Drag the labels into position on the flow chart of hepatobiliary bile processing.

Red blood cells contain the protein hemoglobin. When red blood cells are old or injured, the spleen breaks them down and converts the heme from their hemoglobin into bilirubin. The liver further converts it into bile, which is stored in the gall bladder. When you eat fat, the cells of your small intestine release the hormone cholecystokinin. Contraction of the gall bladder forces the bile into the duodenum, where it emulsifies fats and aids in their digestion.

As Mrs. F stands up, you notice that she is limping. She tells you that she banged her foot against a chair several days ago, and it is still sore. When you examine it, you see a swollen, dark purple little toe on her right foot.What is the significance of this sign? What further assessment would be most appropriate for Mrs. F's bruised toe?

She may have trouble absorbing calcium, so you should check to see if the toe is broken.

Match these vocabulary terms to their meanings.

The enzymes that digest lipids are called lipases. After swallowing, the gastroesophageal sphincter opens to allow food from the esophagus into the stomach. During the enterogastric reflex, acid secretion in the stomach is inhibited. Liver cells are more properly referred to as hepatocytes.

Choose the answer that best describes the liver's role in lipid digestion.

The liver creates bile, a soapy compound that emulsifies lipids.

Explain why the underproduction of albumin by a cirrhotic liver contributes to excessive filtration, which leads to ascites. Refer again to the forces that determine net filtration pressure in the hepatic capillaries, and to the function of albumins.

The liver is the major production site of albumins. Albumin (the main protein) is typically too large to diffuse across the capillary wall, so it remains in the blood vessels where they create an osmotic force that maintains water volume in the vasculature. In fact, albumins are the primary source of osmotic pressure, contributing to the reabsorption of water.

Why does liver dysfunction, such as cirrhosis, lead to hyperglycemia?

The liver is unable to take up glucose and store it as glycogen. Liver injury, as in alcoholic cirrhosis, impairs the ability of the liver to take up and store glucose, which leads to increased glucose in the blood.

Mrs. F's blood work has come back and shows that she has low plasma osmolarity and decreased levels of plasma proteins and plasma K+K+. The doctor says, "This explains her edema!"How are plasma proteins related to edema? Drag the terms to complete the summary of Mrs. F's protein problems.

The normal osmolarity of intracellular and extracellular fluid is 300 mOsm, which makes them isotonic. Normal cell and plasma osmolarity is best illustrated by diagram number 1. Mrs. F's liver is no longer producing enough plasma protein so her blood has become hypotonic to her cells. This is best illustrated by diagram number 3. Because Mrs. F's cells are hypertonic to her plasma, water will move into the cells by osmosis, causing her tissues to swell.

Enteric interneurons that are inhibitory to smooth muscle use which of the following neurotransmitters?

VIP (vasoactive intestinal peptide)

In response to a steak dinner, certain secretions are needed to aid digestion. What cells in the pancreas would provide these secretions?

acinar cells Yes, in response to a high fat and protein meal, CCK would be stimulated and in turn would stimulate an enzyme-rich secretion from the pancreas.

HCl secretions convert pepsinogen to the active hormone pepsin. What cells in the gastric pits produce pepsinogen?

chief

The cholesterol determination is _______.

enzymatic and colorimetric

The breakdown products of which of the following are absorbed into lacteals?

fats Yes, chylomicrons are absorbed into lacteals because they are too large to pass through the basement membrane of a capillary and into the blood.

Salivation is controlled almost entirely by the nervous system. Which of the following stimuli would inhibit salivation? -fear -the thought of food -nausea -a lemon

fear Yes, fear, sleep, fatigue, and dehydration all inhibit salivation.

In the small intestine, which of the following enzymes breaks down oligosaccharides?

glucoamylase

Chyme entering the large intestine normally consists of __________.

indigestible fiber, enteric bacteria, and water

In Mr. Volpe's case, H. pylori degraded his duodenal lining, leaving it vulnerable to the stomach HCl. What other constituent of gastric juice is harmful to a damaged duodenal wall?

pepsin Pepsin is an enzyme that digests protein in the acidic environment of the stomach. Typically pepsin is inactivated by the higher pH of the pancreatic juices in the duodenum. However, when H. pylori degrades the duodenal mucosa, the pepsin can further digest the tissue of the duodenal wall, creating an ulcer.

Which of the following digestive processes could be affected by a patient's taking a large amount of antacids?

protein digestion Protein digestion is partially accomplished by pepsin, an enzyme that works best in a pH range of 1.5 to 2.5.

Which patient sample(s) tested in the borderline elevated range?

sample 4

Which patient sample(s) tested in the desirable range?

samples 1 and 3

In this activity, we will measure _______.

total blood cholesterol

Choose the two most likely organs involved in her illness.

-Gall bladder, because it stores bile and might be related to the bilirubin buildup in her blood. -Liver, because of the yellow coloration in her eyes, which indicates that the liver is not processing bilirubin.

The medication Pepcid® that Mr. Volpe took for partial relief of his dyspepsia is called an H2 (histamine) receptor antagonist, or H2 blocker. That means it prevents histamine release. What is the normal function of histamine in the stomach and how might this help Mr. Volpe's hyperacidity problem?

During the gastric phase of digestion, when food has entered the stomach, three chemicals are released that signal parietal cells to secrete HCl: acetylcholine (by parasympathetic nerve fibers), gastrin (by gastrin-secreting enteroendocrine cells called G cells), and histamine (from enterochromafin-like cells). A histamine-receptor blocker, like Pepsid® (famotadine), inhibits the release of histamine and, thereby, diminishes hydrogen generation and HCl secretion. Since histamine is the dominant pathway for hydrogen generation, blocking it is often sufficient to control acid secretion in the stomach.

Which of the following is a source of dietary fiber and promotes timely movement through the colon?

cellulose Yes, the polysaccharide cellulose is not digested and is used as a source of dietary fiber.

The blood tests came back negative for liver and pancreatic enzymes, but the X-ray confirmed gallstones filling her gallbladder and blocking the lower biliary duct near the hepatopancreatic ampulla (ampulla of Vater). The doctor mentioned that this might also affect pancreatic function, scheduled a cholecystectomy for the next day, and decided to admit her to the hospital overnight. Why might a gallstone affect the pancreas? Choose the most accurate answer.

A gallstone that blocks the hepatopancreatic ampulla (ampulla of Vater) will block the release of digestive enzymes from the pancreas.

Salivary amylase is a digestive enzyme not featured in the Concept Map. Which of the following describes its function? breaks down complex starches into smaller units, and where in the body does this occur?

Salivary amylase breaks down complex starches into smaller units in the mouth.

Dr. Lorraine explains to Mr. Volpe that H. pylori decreases the buffering effect in his duodenum. How does the duodenum buffer the acidic gastric chyme?

Secretion of bicarbonate-rich mucosal mucus and pancreatic juice in the duodenum. Normally, the pancreas secretes bicarbonate-rich "pancreatic juice" into the duodenum that matches the amount of HCl secreted in the stomach. In addition, the duodenal submucosal glands (called Brunner's glands) secrete an alkaline mucus. Together they buffer the acidity of gastric chyme.

The nurse asked whether she has noticed a change in her stools. The woman answered that they were hard to flush (they float) and kind of gray-looking.Why did the nurse ask about stools? Choose the best explanation for the nurse's question.

Someone with difficulty converting bilirubin into bile will have trouble digesting fats, and they will go out in the stool. Like you, this nurse realized that if bile doesn't enter the duodenum, fat will pass through the intestines without being digested, and as a result it will pass out in the stools. The stools will be pale, perhaps foamy or liquid, because of the fat in them. And fat floats, so the stools will be hard to flush down the toilet! The clinical term for this is "steatorrhea," or fatty diarrhea.This is the sort of sign that patients may be embarrassed to bring up unless you ask them.

One year after Mr. Volpe's therapy, Dr. Lorraine performs a follow-up endoscopy and is delighted to see a healed and healthy duodenum. Describe what she sees through the lens of her endoscope as she looks at the lining of the duodenum.

The brush border is distinctive to the duodenum and is formed by the densely packed microvilli on the villi of the mucosal layer. The circular folds - plicae circularis - are also apparent.

In order to understand the disease in Mr. Volpe's alimentary canal, one must know the layers that make up its walls. Design a chart that identifies the four basic layers of the alimentary canal, the tissues that make up each layer, and the general function of each layer.

The four layers of the alimentary canal, from the lumen out, are: mucosa, submucosa, muscularis externa, and serosa. The mucosa is coated with simple columnar epithelium. It secretes mucus, enzymes and hormone; protects underlying layers; and absorbs digested end-products. The submucosa, composed of areolar connective tissue, surrounds the mucosa and contains blood and lymph vessels as well as nerves that serve nearby tissues. The muscularis externa is composed of smooth muscle that contributes to motility in the alimentary canal. Lastly, the outermost serosa is an epithelial-connective tissue membrane (visceral peritoneum) that anchors the alimentary canal in the abdominal cavity. (In the esophagus, the serosa is replaced by a fibrous connective tissue called adventitia.)

As Dr. Lorraine is listening to Mr. Volpe's complaints she automatically visualizes the organs in the epigastric region that are the potential source of his problems. Where is the epigastric region and what organs associated with digestion are located in that area?

The organs near or in the epigastric region are the stomach, pancreas, liver, gall bladder, esophagus, and duodenum. The heart, aorta, and lungs are nearby but rarely refer pain to the epigastric region, and so rarely cause the gnawing, burning pain associated with eating that Mr. Volpe presents.

Match these prefixes to their meanings.

The prefix lip(o)- means fat or fatty tissue. The prefix entero- means intestine. The prefix gastr- means ventral area or stomach. The prefix hepato- means liver.

Mr. Volpe indicates he has epigastric pain, which leads Dr. Lorraine to consider several organs in that region. Which of the following organs is NOT a likely culprit since it is not in the epigastric region? -stomach -appendix -duodenum -liver

appendix The epigastric region of the abdomen is above the umbilical region. The appendix is in the right-lower quadrant of the abdomen, below the umbilicus.

How are vitamins A, D, E, and K absorbed by the body?

by being incorporated into micelles Fat-soluble vitamins are incorporated into micelles when fats are present. Without dietary fats available, these vitamins are not absorbed.

What other organ in Mrs. Fender's right upper quadrant, besides the liver, must be considered when investigating her abdominal pain?

gallbladder The gallbladder is located on the posterior surface of the liver in the right upper quadrant of the abdomen.

What is the condition called where a proximal portion of the stomach pushes through an opening in the diaphragm, allowing stomach acid to pass into the esophagus?

hiatal hernia

Hypocholesterolemia is linked to _______.

low levels of serotonin

Hepatocytes contain an extensive rough endoplasmic reticulum, Golgi apparatus, and abundant exocytotic vesicles. These cellular structures work together to ______.

manufacture and export a variety of proteins The rough ER produces proteins, the Golgi packages proteins, and vesicles are formed around these proteins to export them by exocytosis.

This group of enzymes digests the majority of ingested fat.

pancreatic lipases Pancreatic lipases break the bonds between fatty acid chains and glycerol after the fats have been emulsified.

Enzymatic breakdown of which of the following compounds doesn't begin until it reaches the stomach?

proteins

Which of the following GI hormones promotes a pancreatic juice rich in bicarbonate ions?

secretin Secretin (from S cells in the duodenum) causes both the liver and pancreas to secrete bicarbonate into the small intestine.

An increase in HCl (hydrochloric acid) arriving in the duodenum would stimulate which hormone that would help to counteract the effects of HCl?

secretin Yes, secretin stimulates the duct cells in the pancreas and liver to secrete a bicarbonate-rich solution that will bind hydrogen ions and increase the pH.

In what portion of the gastrointestinal tract does most salt and water absorption occur?

small intestine

Dr. Lorraine explains to Mr. Volpe that the H. pylori often causes excess stomach acid secretion. All of the following mechanisms normally increase gastric acid secretion EXCEPT ________. -gastrin -histamine -acetylcholine from the parasympathetic nerve fibers -somatostatin

somatostatin Somatostatin inhibits gastric and pancreatic secretions.

Clinical Case Study: Peptic Ulcer Disease: A Case on the Digestive System

It's Friday morning and Sal Volpe is sitting in Dr. Lorraine's exam room, dozing after another night of disrupted sleep. When the doctor knocks and walks in, she finds the 66-year-old man looking exhausted and uncomfortable. Sal gets to the reason for his visit immediately: He's been suffering from "stomach aches" (dyspepsia) that wake him at night and nag him in between meals during the day. He describes his pain as gnawing, burning (maybe a 4 out of 10 on a pain scale), and points to the epigastric region of his abdomen. When he eats, he tells Dr. Lorraine, the pain goes away, but then he feels bloated and a little nauseated. The pain usually returns 2-4 hours later, depending on what he eats. Sal explains that he has had some pain relief from the over-the-counter drug Pepcid® (famotadine). Dr. Lorraine proceeds with the history and physical exam. She discovers that Sal has a family history for gastrointestinal cancer and has unintentionally lost 10 pounds since his checkup a year ago. His epigastric area is modestly tender to palpation. She suspects a peptic ulcer (gastric or duodenal), but the weight loss and family history make it prudent to eliminate the diagnosis of stomach (gastric) cancer. "Mr. Volpe, I think you may have a stomach or intestinal ulcer," Dr. Lorraine says. "I suggest we perform an endoscopy to have a look. This involves passing a small tube with a small camera through your mouth and into your stomach. We can look at the wall of your stomach and small intestine, check for an ulcer, and remove a very small piece of tissue to test for infection. We call this a biopsy. We'll also test the biopsy for cancer because of your family history. But, I really think we're dealing with an ulcer here and not cancer." Later that month, the endoscopy is performed and it confirms Dr. Lorraine's suspicions. Sal has a duodenal ulcer and infection with the bacterium Helicobacter pylori (H. pylori). This is not surprising since H. pylori is the cause of most peptic ulcer disease, particularly in the duodenum. Treatment involves complete eradication of the H. pylori with two different antibiotics, and a drug that decreases gastric acid secretion, a so-called proton pump inhibitor (PPI). Dr. Lorraine explains to Sal, "Mr. Volpe, you do not have stomach cancer, but you do have a duodenal ulcer caused by the H. pylori bacteria I was telling you about. Too much acid and inflammation from this infection is causing your pain. The good news is we can probably cure your ulcer by killing the bacteria, but you will have to take three different medications twice a day for 14 days. I'll see you again in 3 weeks; we can do a simple breath test to determine if the H. pylori has been successfully eliminated."

All of the following reasons can explain why most peptic ulcers, like Mr. Volpe's, occur in duodenum EXCEPT which statement? -Normally, the duodenum lacks a mucosal layer. -Bicarbonate-rich pancreatic juice is secreted after the acidic chyme enters the duodenum. -The duodenum is the anatomical structure nearest to the stomach's outlet. -The chyme coming from the stomach is very acidic.

Normally, the duodenum lacks a mucosal layer. The duodenum is lined in a mucosa is made up of simple columnar epithelium abundant in mucus-secreting cells which provide a slippery, wet protective barrier from digestive enzymes, pathogens and other harmful substances. The duodenum is right at the outlet of the stomach, it is the first receptacle of stomach's highly acidic chyme, and the chyme arrives before the pancreas secretes neutralizing bicarbonate-rich juices.

The woman was scheduled for laparoscopic cholecystectomy the next day. But that night she developed severe abdominal pain. The nurse noticed the following: She was pale, sweating, and had cool, clammy skin. Her heart rate was high and so was her blood pressure. She had no detectible bowel sounds.What part of the autonomic system appears to be activated in this client?

Sympathetic −− you can tell because the sympathetic system causes most of her signs and symptoms. This patient's pain and fear have activated her sympathetic system, the response her body uses to survive emergencies. That's what has made her pale and sweaty, increased her heart rate and blood pressure, and decreased her intestinal motility, reducing her bowel sounds.

Mr. Volpe asks, "What do the bacteria have to do with the ulcer?" Dr. Lorraine tells him that the H. pylori increases stomach acid secretion and, at the same time, breaks down the lining of your stomach and duodenum. What is the source and normal function of acid in the stomach and what regulates its production?

The parietal cells in gastric pits pump out hydrogen and chloride, which combine in the stomach to form the strong acid, HCl. HCl aids in digestion by activating pepsin, denaturing food proteins, and breaking down plant cell walls. As a protective mechanism, HCl kills many types of microorganisms. Secretion of HCl is under the regulation of the gastric reflex and the hormone gastrin. When food enters the stomach, baroreceptors are stretched and chemoreceptors detect protein and an increase in pH. Nerve signals reflexively increase gastric secretions (including gastrin) and motility. The protein content of food also stimulates the release of gastrin from enteroendocrine cells in gastric pits. Gastrin then stimulates the release of HCl from parietal cells.

Which of the following were disposed of in the biohazardous waste disposal?

the alcohol wipe, the lancet, and the cholesterol strip

Cirrhosis leads to scarring and increased hydrostatic pressure in the hepatic portal vein. Explain why this increased venous pressure causes net filtration to increase in the hepatic capillaries, leading to ascites (swollen and fluid-filled interstitial space of the abdomen).

In alcoholic cirrhosis, the portal vein becomes scarred and blocked, causing an increase in hydrostatic pressure (portal hypertension). This leads to an increase in capillary hydrostatic pressure. Alcoholic cirrhosis also causes the liver to underproduce albumin. This lowers osmotic pressure in the vasculature, enhancing filtration out of the capillaries. (Recall the effect of capillary hydrostatic pressure and osmotic pressure on net filtration.)

The secretion in the large intestine consists of which of the following?

bicarbonate- and potassium-rich mucus Yes, an alkaline mucus secretion of bicarbonate and potassium protects the large intestinal wall from acids produced by resident bacteria.

LDLs contain _______.

cholesterol and protein

During which phase in the control of the digestive system would bicarbonate and bile be stimulated?

intestinal phase Food in the intestines initiates a reflex that stimulates secretions of bicarbonate, digestive enzymes, and bile.

Which of the following enzymes is important for the digestion of fat?

pancreatic lipase Yes, pancreatic lipase is important for the digestion of fats. It is secreted by the pancreas and works in the small intestine.

Which of the following enzymes is important for breaking down protein?

pepsin

An individual diagnosed with celiac disease would be prescribed a gluten-free diet in order to __________.

prevent inflammation caused by malabsorption of gluten protein In a person with celiac disease, gluten breakdown products interact with the immune system in the digestive tract, leading to damage of the intestinal lining.

Norepinephrine is the neurotransmitter released by which fibers?

sympathetic postganglionic fibers

Dr. Lorraine is suspicious of a peptic ulcer, which is a disruption in the stomach or duodenal mucosa extending through its muscularis layer. The primary function of the mucosa is _________.

to provide a protective barrier The mucosa is made up of simple columnar epithelium abundant in mucus-secreting cells which provide a slippery, wet protective barrier from digestive enzymes, pathogens, and other harmful substances. In both stomach and duodenum, this epithelial layer is highly regenerative for rapid repair. This is particularly useful in the hostile environment of the stomach. In the stomach the epithelium is also simple columnar epithelium with abundant mucus cells; they produce an especially viscious, alkaline mucus that protects against the acidic gastric juices and pepsin. Additionally, there are deep gastric pits with a variety of chemical-secreting cells.

Which patient sample(s) tested in the elevated range?

sample 2

Mrs. F has spider nevi, broken skin capillaries. Normally, broken skin capillaries do not cause visible blemishes, but hers are bleeding more than usual. Could this be due to her liver problems? Which of the liver functions below are most likely to affect Mrs. F's clotting?

-The liver creates many plasma proteins. -The liver makes bile, which is needed to absorb lipid-soluble vitamins.

The liver is known for its ability to remove certain toxins from the blood. It can perform this function because its cells, or hepatocytes, contain large quantities of lysosomes and peroxisomes, and also have an extensive smooth endoplasmic reticulum. Briefly describe how these three organelles contribute to this major function of the liver.

Lysosomes engulf toxins by endocytosis and contain acid hydrolases that digest the toxins so they can be safely eliminated by the cell. Peroxisomes engulf toxins by endocytosis and contain oxidases and catalases that detoxify substances like alcohol and neutralize free radicals. The oxidases convert free radicals to hydrogen peroxide, while the catalases complete the process by converting the hydrogen peroxide to water. The smooth endoplasmic reticulum (ER) is part of a network of interconnecting, fluid-filled tubules. The smooth ER contains enzymes (such as the cytochrome P450 enzymatic system) that detoxify certain drugs (such as alcohol).

Nurses Need Physiology: Liver Failure

Mrs. F has a history of mild heart problems, but she has been admitted to the medical-surgical floor for management of her liver failure. She is a white-haired woman in her sixties with a puffy face, overweight, and presents with yellowish skin and sclera, mild generalized edema (swelling), spider nevi (broken capillaries), high blood pressure, increased respiratory rate, and a heart rate of 59 bpm (normal is 60-100 bpm). When you ask whether she has noticed any changes lately, Mrs. F complains about dizziness and lightheadedness. She also mentions weight gain and that her slacks are too tight. She says "They told me this disease would interfere with my digesting lipid, so I thought I'd lose weight!"How is the liver related to lipid digestion?

One of the liver's functions is the production of bile, which helps emulsify lipids in the intestinal contents so they can be effectively digested.Is there any reason to think Mrs. F's liver is not performing this function? Choose the answer that best describes the evidence for altered bile production.

Mrs. F's yellowish skin and sclerae indicate that bilirubin is depositing in her skin instead of being made into bile by the liver. You have identified Mrs. F's jaundice, the yellowish color caused when excessive bilirubin settles in the skin. The liver is not converting that bilirubin into bile, so Mrs. F is also suffering from lack of bile in her digestive system (leading to difficulty digesting lipids). This will also interfere with her absorption of the lipid-soluble vitamins A, D, E, and K.

Dr. Lorraine also explains to Mr. Volpe that H. pylori impairs the normal buffering effect in his duodenum. What does she mean by the "buffering effect?" How does the duodenum accomplish this, and in what way does this protect the duodenum?

Normally, when the acidic chyme is moved into the duodenum it signals the pancreas to secrete bicarbonate-rich juice into the duodenum and duodenal submucosal glands, and to secrete a mucus that is also rich in bicarbonate. The amount of the bicarbonate (a base) that is produced is approximately equivalent to the amount of HCl produced in the stomach. The protection this secretion offers is twofold: neutralization of the acidic chyme (raising the pH), and coating the duodenal wall in viscous, alkaline mucus. H. pylori diminishes the release of bicarbonate-rich mucus, leaving the intestinal wall vulnerable to erosion by the acidic chyme.

Clinical Case Study: Booze Blues: A Case on the Liver

Peggy Fender is well known to the emergency department (ED) staff. She's a 59-year-old woman whose visit today is similar to her frequent visits in the past. She arrives in the afternoon, appearing intoxicated and complaining of abdominal pain, particularly in the right upper quadrant (RUQ) of her abdominopelvic cavity. "Another Fender bender," a nearby nurse whispers to Tim, the new physician assistant (PA) who is due to examine Mrs. Fender. Tim proceeds with his physical examination. Mrs. Fender appears emaciated with bruising of various ages on her arms, legs, and face. She is jaundiced (yellow-skinned) and has the strong smell of alcohol on her breath. Tim palpates the inferior border of her liver, which is hard and enlarged; Mrs. Fender moans with pain. Her entire abdomen is ascitic (swollen and fluid-filled). Mrs. Fender is not entirely coherent; she knows where she is and who she is, but is unable to relate anything about her present illness except a slurred, "My stomach hurts; quit poking it, you idiot!" Her coordination is poor when she attempts to sit or stand. She becomes annoyed and indignant when Tim asks her how much alcohol she's had to drink today even though she is obviously inebriated. Tim reviews her blood tests, which reveal elevated blood transaminases (liver enzymes), high blood glucose (hyperglycemia), and prolonged prothrombin time (PT - slowed clotting time). Based on her history, and present findings, Tim diagnoses Mrs. Fender with alcoholic cirrhosis, which is the result of chronic inflammation of the liver from heavy, consistent alcohol ingestion. If alcohol abuse continues long-term, it leads to fat accumulation in the liver, followed by fibrosis and severe liver dysfunction.

Nurses Need Physiology: Biliary Obstruction and Pancreatitis

Physiology and anatomy problem-solving skills can be vital when you're the one taking a patient's history or doing the initial assessment. If you remember the functions of different organs and their anatomical relationships, you can come up with hypotheses and ask the relevant questions to test them. You will also know what to be alert for when caring for the patient later.An overweight forty-three-year-old woman had been having episodes of gripping abdominal pain after fatty meals. One day she ate French onion soup with lots of cheese and suffered severe enough pain that she called in sick. Her supervisor pointed out that she always gets sick after fatty foods. She went to the clinic and the nurse in triage took her vitals and history.The nurse noticed that the whites of her eyes were yellow and that she had tenderness on the right side of her abdomen. Blood pressure and heart rate were normal.Based on this initial assessment, what organs do you think might be involved in this woman's illness, and why?

The woman was given IV pain meds, and blood was drawn to assess liver and pancreatic function, given her gallstone history. Pancreatic enzymes were elevated, and the doctor diagnosed acute hemorrhagic pancreatitis.After her surgery to remove her gallbladder and clear the obstructed bile duct, the woman recovered uneventfully, and her pancreatitis resolved. Now she wants to know what this surgery has done to her ability to produce bile and digest food. What is the answer?

She can still make bile, but she can't store it, so she can't send a large amount into the duodenum to deal with a lot of fat at one time. This patient's liver is undamaged, so she can still produce bile. Without a gall bladder, however, she has no place to store the bile, and no ability to squeeze an extra amount of bile into her duodenum after eating fat. She may have some digestive problems if she eats large amounts of fat. This varies a great deal with the individual, so her best plan will be to be cautious until she discovers how much fat she can handle.You've used your knowledge of the hepatobiliary system to analyze a case in which a problem starting in one organ −− the gallbladder −− caused damage to another, the pancreas. Without knowing the anatomy of the biliary ducts, health professionals couldn't have predicted this life-threatening complication.

Mrs. F's blood work has come back and shows that she has low plasma osmolarity and decreased levels of plasma proteins and plasma K+. You can see how plasma proteins are related to her liver failure, since the liver synthesizes plasma proteins. But why does she have low K+ levels?

The liver destroys aldosterone. When you think about K+, you should think about aldosterone right away. Aldosterone is the hormone that activates the Na+/K+ exchange in the kidneys, moving 3 Na+ into the blood and 2 K+ into the urine. The liver stops this process by destroying the aldosterone.If the liver cannot destroy aldosterone fast enough, the Na+/K+ exchange will continue to run, and K+ will be lost in the urine. This is sometimes called "potassium wasting." Because potassium controls nerve and muscle firing, this loss of potassium could cause decreased reflexes, weakness, and-finally-fatal heart arrhythmias.In addition, Mrs. F will be moving too much Na+ from her urine into her blood-and because there is more solute entering her blood than her urine, water will also move from her urine into her blood, increasing her blood volume. That is why she has high blood pressure, and it may also make her edema worse.As you care for Mrs. F, you will need to be aware of these potential problems and watch carefully (so you can catch them early if they develop).

The liver has a portal vein as well as a hepatic vein. It also has unique exchange blood vessels similar to capillaries, called "sinusoids." How do these unique structures determine the function of the organ?

The liver has a unique circulatory system. About 75% of the blood flowing through the liver comes from the portal vein, carrying venous blood from the intestines, stomach, pancreas, and spleen. This assures direct delivery of nutrient-rich blood to the liver, which will appropriately package, store, or release these nutrients as the body needs them. The other 25% of blood flow comes from the hepatic artery, which carries arterial blood from the abdominal aorta. This blood is oxygen-rich and refreshes the highly metabolic hepatocytes. At the terminal branches of the portal vein and hepatic artery, the blood mixes and flows into the liver capillaries, which are called sinusoids. The walls of the sinusoids are highly fenestrated, discontinuous epithelial cells that allow plasma and solute to leak into the interstitial space between surrounding hepatocytes. In essence, the blood "percolates" in the sinusoids on its way to the hepatic veins, and then to the vena cava. This percolation is ideal for hepatocytes to filter the blood, process and store nutrients, detoxify (e.g., remove ammonia), and remove debris (e.g., worn-out RBCs, bacteria).

Mrs. Fender's prolonged clotting times and excessive bruising are related. Again, referring to normal physiological functioning of the liver, why do these two things happen when alcohol damages hepatocytes?

The liver produces clotting proteins. When it is damaged (as in cirrhosis), clotting proteins are underproduced and it takes longer for blood to clot (prolonged prothrombin time - PT). This can be evidenced by excessive bruising as well. (It should be noted that alcoholics are also accident-prone when drinking because alcohol impairs their coordination and balance, which contributes to excessive injury and bruising.)

Dr. Lorraine suspects a peptic ulcer. This is an inflammatory lesion in the stomach or duodenal mucosa, which may extend through all layers of the alimentary canal wall. Describe the basic histological (tissue) structure of the mucosa layer in the alimentary canal. Identify the unique features of the mucosa in the stomach and in the duodenum, and explain how this uniqueness determines the function of the stomach and the duodenum.

The mucosal layer is composed of three layers, beginning with the innermost layer: mucosa, lamina propria, and muscularis mucosae. A basic mucosa is made up of simple columnar epithelium that is abundant in mucus-secreting cells, which provide a slippery, wet protective barrier from digestive enzymes, pathogens and other harmful substances. In both the stomach and duodenum, this epithelial layer is highly regenerative for rapid repair. This is particularly useful in the hostile environment of the stomach. In the stomach, the simple columnar epithelium contains many mucus cells; these cells produce a viscous, alkaline mucus that protects against the acidic gastric juices and pepsin. The stomach mucosa also forms gastric pits that release a variety of secretions, which form gastric juice. In the duodenum, the mucosa forms villi - finger-like projections that line the epithelium with microvilli; this greatly enhances surface area. Additionally, the duodenal mucosa forms deep, circular folds - plicae circularis - that churn chyme slowly along the duodenal wall. The greatly enhanced surface area and plicae circularis help to optimize nutrient absorption. The lamina propria is made of loose aerolar connective tissue with a rich capillary bed. Along with the mucosa, the lamina propria forms what is called the mucus membrane. In both the stomach and duodenum, but particularly the duodenum, digested nutrients are absorbed into the capillaries. The muscularis mucosae is made of a thin layer of smooth muscle. It contributes the movement of the mucosa and the facilitation of secretions in both the stomach and duodenum. (The muscularis externa is primarily responsible for motility patterns.)

Mr. Volpe's one-year follow-up endoscopy shows a healed duodenal wall (no more ulcer). What distinctive feature is now visible in the duodenum?

brush border The brush border is distinctive to the duodenum and is formed by the densely packed microvilli on the villi of the mucosal layer.

Why is Mr. Volpe's dyspepsia relieved by food, and aggravated 2-4 hours after a meal?

When food enters the stomach (during the gastric phase of digestion) it raises the pH of stomach contents (which are less acidic), closes the pyloric sphincter, and inhibits duodenal secretions and motility. The stomach begins secreting HCl and is typically empty of food about 2-4 hours after a meal, longer if the meal is high in fat. Also, the stomach continues to secrete HCl for 3-5 hours after eating. (At night, circadian-mediated secretion of HCl is peaking, so this is why Mr. Volpe is awakened by the epigastric pain.)

Where are the enzymes for digestion of disaccharides and small polypeptides located?

brush border Yes, the enzymes for digestion of disaccharides and small polypeptides are found in the brush border of most the absorptive cells of the small intestine.

This type of chemical reaction typically occurs as nutrients are digested in the body.

hydrolysis Hydrolysis refers to the enzymatic breakdown of large polymers into monomers while adding the parts of a water molecule to the broken bonds.

Transaminases, coagulation factors, and albumin are all what kind of organic compound?

protein Transaminases (enzymes), coagulation factors, and albumins are all proteins.