PHSL3051 Dr. Olson’s Notes
Introduction to The Digestive System PHSL 3051 Fall 2019
Professor: Dr. Dalay Olson Email: [email protected] Office: 3-120 Jackson Hall Office Hours: Monday 2-3pm or By Appointment.
Reading list:
Textbook Pages Critical Thinking Topics & Sections Exercises Intro to GI 721-727 (21.1) 11.1
Upper GI 727-732 (21.2-21.3) 11.1
Gastric Physiology and SI 732-763 (21.4, 21.6) 11.2-11.4
Smooth Muscle & ANS (Lab) 724-725 (21.6) 11.1 736-740, 750-752 Pancreas, Liver and LI 11.3, 11.5 (21.5, 21.7-21.9)
PowerPoint presentations and class notes can be found on Canvas.
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PHSL3051 Dr. Olson’s Notes Introduction to the Gastrointestinal Tract and Saliva Mini Pre-lecture 1 & 2
Learning objectives:
• Determine the primary roles of the digestive system. • Identify the layers of the gut wall and describe their function. • Explain how the enteric nervous system serves as a control center for short reflexes. • Describe how the chemical components of saliva are helpful for starting the digestion process. • Describe the physiologic stimuli of salivary secretion.
Overview
Organs System Using the word bank, identify the following structures in the image. Where should the stomach be in this figure? Draw it in. Word Bank
Common bile duct
Gallbladder
Sphincter of Oddi
Pancreatic duct
Duodenum
Liver
Pancreas
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PHSL3051 Dr. Olson’s Notes Tissue Level Identify each tissue layer in the GENERAL image of the gut below and describe its function.
Mucosa
Submucosa
Enteric nervous system
Muscularis Externa
Roles of the digestive system Describe the six major roles of the digestive system. 1.______
2.______
3.______
4.______
5.______
6.______
In your own words explain what the digestive system does.
Follow the breakdown process of protein within your digestive tract.
1. What is the food particle? ______2. Name a specific enzyme that helps you digest that food particle ______3. Identify the smaller food particles created following protein digestion ______.
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PHSL3051 Dr. Olson’s Notes Enteric Nervous System The enteric nervous system is broken up into a myenteric plexus and a submucosal plexus.
Describe the myenteric plexus below. When it becomes activated what is the major physiological response? When would this plexus be activated?
Describe the submucosal plexus below. When it becomes activated what is the major physiological response? When would this plexus be activated?
Sensory neurons are responsible for relaying information to different parts of the body. Where are the sensory neurons in the intestine located and what parts of the nervous system is it in contact with?
Short and Long Reflexes On the exam you will have to be able to distinguish between short and long reflexes. Compare short and long reflexes below using the Venn diagram.
Long Reflex Short Reflex
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PHSL3051 Dr. Olson’s Notes Phases of Digestion: There are three phases of digestion. Briefly describe each.
Cephalic Phase
Gastric Phase
Intestinal Phase
Saliva Organ System: Salivary Glands What is the primary role of the salivary glands?
How many glands are there in the mouth?
If one of your glands became injured would you still produce saliva?
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PHSL3051 Dr. Olson’s Notes Saliva Identify and describe the five major roles of saliva below.
A B
A B
Role #1 ______.
Role #2______.
Role #3______.
Role #4______.
Role #5______.
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PHSL3051 Dr. Olson’s Notes Lecture 1-Upper GI
• Describe the voluntary and reflex components of swallowing. CT 11.1 #4
• Distinguish between the wall layers of the esophagus and those classically represented by the S.I. (i.e. the transition from skeletal to smooth muscle in the muscularis).
• Describe the local peristaltic reflexes that occur in the esophagus in response to stretch.
• Describe how the closing of lower esophageal sphincter (LES) is aided by positive abdominal pressure. Predict how the closing of the LES is altered with LES displacement into the thoracic cavity. Make the connection between LES function and gastric reflux disease.
General Overview What physiological symptoms would you expect from someone suffering from xerostomia?
What physiological processes are occurring during the cephalic phase?
Organ System: Esophagus The upper 1/3 of the esophagus differs from the lower 2/3rd in what anatomical way?
Is any of the muscle found in the esophagus under voluntary control?
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PHSL3051 Dr. Olson’s Notes Swallowing Reflex
1. In the boxes provided, briefly identify each phase and describe in words what is occurring during each phase. 2. Complete each of these steps for the appropriate phase. a. Voluntary phase: circle where in the mouth the mechanoreceptors are located (this is the sensor). b. Pharyngeal phase: List the effectors activated c. Esophageal phase: Compare the myogenic and short reflex occurring here.
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PHSL3051 Dr. Olson’s Notes
Complete the flow chart for the swallowing reflex and identify and describe each component below. The controlled variable is muscle length in the back of the mouth.
What is the stimulus for swallowing? ______.
What type of receptor senses the presence of food?
What is the input? ______.
What is the control center? ______.
What is the output? Where is the output originating from?
List the effectors. (There are several!)
Is this negative feedback or positive feedback? How do you know?
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PHSL3051 Dr. Olson’s Notes
Which part of swallowing is voluntary? Which part is involuntary?
Is the swallowing reflex a short or long reflex? How do you know?
Peristalsis in the esophagus There are two distinct pathways that result in peristaltic waves of muscle contraction within the esophagus. Please become familiar with the mechanism of both. Both mechanisms will reappear throughout the digestive tract. The Myogenic Reflex The myogenic reflex occurs entirely within each smooth muscle cell following a stretch stimulus. Describe the myogenic reflex in your own words (include the reflex stimulus and output).
Mechanistically, how does Ca2+ levels increase during the myogenic reflex? What kind of receptor is being activated? How does an increase in Ca2+ levels result in peristalsis?
Is the myogenic reflex a short reflex, long reflex or neither? Justify your answer.
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PHSL3051 Dr. Olson’s Notes Classic activation of peristalsis Mucosal cells in the esophagus sense the bolus of food and respond by activating smooth muscle cells to contract. Fill out the reflex pathway shown. The controlled variable is smooth muscle length in the esophagus.
What is the stimulus?
What kind of receptor is sensing the stimulus?
What is the input?
Where is the control center located?
What is the output?
What are the effectors?
What do the effectors do? (What is the response?)
Is this a short or long reflex? How do you know?
The Lower Esophageal Sphincter (LES) What is the LES?
Why is the LES located outside of the thoracic cavity?
What does GERD stand for? What causes this disease?
Who is most susceptible to this disease and why?
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PHSL3051 Dr. Olson’s Notes Mini Pre-lecture: Gastric Physiology
1. Describe how the gastric muscularis (three layers of smooth muscle) promotes mechanical breakup of chyme through peristalsis. Describe the interaction of the intrinsic BER and extrinsic stimulators of motility in the stomach.
2. Describe the interaction of excitatory and inhibitory stimuli (neural and hormonal) in the regulation of gastric emptying. CT 11.4
General Overview
Describe the three major functions of the stomach.
Storage and motility
Digestion
Protection
Organ System Level
Identify the regions of the three regions of the stomach. Place an “A” next to the regions of the stomach that are acid secreting? Place an “H” next to the region(s) of the stomach that are hormone secreting?
What is a hormone?
What is one major hormone secreted by the stomach? ______
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PHSL3051 Dr. Olson’s Notes
In the previous image, circle the two sphincters on either end of the stomach. Why are sphincters important?
What purpose does the rugae serve?
Tissue Level Using the image, describe the function of each layer of the GI tract and identify the cell types present.
Mucosa
Submucosa
Muscle (What 3 layers are present and what does each do?
The stomach is the only part of the gut containing a third layer of muscle. Which layer of muscle is not typically found in other regions of the gut? Why do you think the stomach has this extra layer?
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PHSL3051 Dr. Olson’s Notes Cellular Level (Gastric Pits) Identify the function of each cell type present in the gastric pit. What does each secrete and what is the role of that secretion? Cell Types Surface mucus cells
Parietal cells
Chief cells
G cells
Notice where the mucus cells are located. Why would it be beneficial for the mucus cells to be located at the top of the gastric pits? What would happen if the acid secreting cells were located at the top instead of the mucus secreting cells?
Notice where the G cells are located within the gastric pits. Why is it beneficial for the G cells to be located near the blood?
Digestion in the stomach Digestion is aided by contractions of all three layers of muscle in the stomach. Just like in the heart, the stomach has pacemaker cells that set its basal electrical rhythm (BER).
What are pacemaker cells? Where else in the body have you learned about pacemaker cells? The spontaneous, rhythmic depolarization of the stomach results in contraction of which muscle layers? ______.
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PHSL3051 Dr. Olson’s Notes
Use the graph to explain what is happening to muscle tension when…
The membrane potential is below threshold.
The membrane potential reaches threshold.
The membrane potential sits above threshold for an extended period of time.
Identify the two branches of the autonomic nervous system.
Compare the pacemaker cell’s response to Ach and NE. Where do these neurotransmitters originate?
Motility Explain how distension of the stomach results in movement of chyme into the small intestine.
Explain how distension of the stomach result in mechanical breakup of the chyme.
Gastric motility is inhibited when fats, amino acids and acid reach which part of the diagram? (circle it). This is important! Why does this happen?
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PHSL3051 Dr. Olson’s Notes Lecture 2: Gastric Physiology
1. Describe the gastric mucosa and discuss how the gastric mucosal secretions (gastrin, acid, pepsinogen, mucus and intrinsic factor) contribute to gastric function. Explain how intrinsic factor and acid help with vitamin B12 and iron absorption.
2. Compare and contrast the intrinsic, paracrine, endocrine and extrinsic mechanisms of acid secretion. Identify the hormones/substances that are secreted for each mechanism. Where do the substances originate and what is their stimulus for release? Explain the negative feedback regulation of somatostatin on acid release.
3. Compare and contrast zymogens with active enzymes. Explain the activation, regulation and function of pepsin.
Acid release in the stomach Release of HCl from the parietal cells relies on the involvement of extrinsic nerves, intrinsic nerves, hormones and paracrine mediators.
What are extrinsic nerves? What is the most important extrinsic nerve in the digestive tract? What types of reflexes are associated with extrinsic nerve activation?
What are intrinsic nerves? What types of reflexes are associated with intrinsic nerves?
Compare and contrast gastrin, histamine and acetylcholine (Ach). Where are they produced? Where are they secreted? What are their targets?
What is the major INHIBITOR of acid secretion? What is its mechanism of action?
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PHSL3051 Dr. Olson’s Notes
Fill in the flow chart describing the different ways in which acid secretion is stimulated in the stomach.
Describe the steps involved in the long reflex depicted:
Describe the steps involved in the short reflex depicted:
Identify and compare the endocrine and paracrine pathways.
Specifically, what branch of the ENS is depicted by ?
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PHSL3051 Dr. Olson’s Notes Mechanism of acid secretion Fill in the equation below
+ Where have you seen this before?
+ The stomach uses this mechanism to produce H . Where does the CO2 originate?
What kind of transport is used to move H+ ions into the lumen of the stomach? How do you know?
a. Primary Active Transport. b. Secondary Active Transport. c. Facilitated Diffusion. d. Simple Diffusion
Describe in your own words the mechanism of acid production in the stomach.
Following the ingestion of a meal, why might the pH of the blood leaving the stomach be elevated?
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PHSL3051 Dr. Olson’s Notes Digestion in the stomach Digestion of primarily proteins begins in the stomach with the help of digestive enzymes and acid. In the stomach, pepsin is the enzyme responsible for cleaving proteins into peptides. Keep in mind, most of the digestion occurs in the intestine. Gastric protein digestion only accounts for 20% of protein digestion.
What is a zymogen and how is it activated?
Is pepsinogen a zymogen or an active enzyme? Underline the part of the name tells you it is a zymogen.
What cells release pepsinogen and how is it activated?
What does pepsinogen do?
Intrinsic Factor and Iron Absorption What is intrinsic factor? Why is important?
If a person stopped producing intrinsic factor, how would Vitamin B12 leave the body?
How does the acidic environment in the stomach help with iron absorption?
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PHSL3051 Dr. Olson’s Notes Mini Pre-lecture: Small intestine Learning Objectives
1. Review the layers of the SI wall including the microstructure of the villus. 2. Identify the major functions of the small intestine and its accessory organs
Tissue Level Identify each tissue layer in the image below and describe its function.
Mucosa
Submucosa
Enteric nervous system
Muscularis Externa
Serosa
What do the circular folds in the intestine help to do?
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PHSL3051 Dr. Olson’s Notes Cellular Level Identify the function of each cell type that comprises the villi in the intestine. What does each secrete and what is the role of that secretion? (Don’t worry about the Paneth cells)
Microvilli
Absorptive Cells
Goblet Cells
Enteroendocrine cells
Counter Current Mechanism The counter current mechanism describes the movement of blood through the villi. Notice the organization of the blood vessel. Which part of the villi experiences the highest concentration of O2? Why does the tip of the villi become hypoxic?
What happens to the cells at the tip of the villi as a result of the hypoxia? Is this beneficial?
Describe the four major functions of the intestine.
Absorption
Digestion
Secretions
Motility
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PHSL3051 Dr. Olson’s Notes Lecture 3: Small intestine and its secretions Learning Objectives
1. Describe the intrinsic (ENS), neural (ANS) and hormonal (CCK, gastrin, motilin and secretin) regulators of motility and digestion in the small intestine. CT 11.3 & 11.5
2. Describe how pancreatic secretions, bile and finally luminal surface enzymes (brush border enzymes) digest carbohydrates, proteins and fats.
3. Compare the absorption of carbohydrates, proteins and fats from the lumen of the GI tract to the blood/lymph vessels. CT 11.2
4. Discuss the exocrine functions of the pancreas and the regulation of these functions by secretin and CCK.
The problem with chyme… There are 3 problems, digestion, movement and neutralization that the intestine must overcome before absorption of nutrients can occur. Let’s focus on each one to see how the intestine deals with the problem. 1st problem with chyme: It is acidic. Why is the chyme acidic? Where does the acid come from?
Why is it important to neutralize the chyme?
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PHSL3051 Dr. Olson’s Notes
The stimulus for this problem is the acid present in the chyme. The controlled variable is a neutral pH. Complete the classic reflex arc below. Recognize that the sensor, input, control center and output is all occuring within one cell, so don’t freak out. The idea is still the same-- you have a stimulus that needs to be turned off (negative feedback).
Fill in the flow chart above and give more specific descriptions in your answers below.
What is the event that disrupts homeostasis in this example? ______.
What senses the change in pH? ______
What cells serve as the control center? ______
Name and describe the output from these cells? ______
Secretin’s effectors are the stomach and the pancreas. Describe the effects of secretin on each of these tissues.
In the pancreas, secretin stimulates the ______to produce bicarbonate.
ductal cells of the pancreas OR acinar cells of the pancreas
What do ductal cells in the pancreas secrete? ______
Where does that bicarbonate go? How does this complete the feedback loop?
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PHSL3051 Dr. Olson’s Notes
Describe the mechanism of bicarbonate production in the pancreas. How is the pH of the blood flowing through the pancreas changing as a result of increased bicarbonate production?
What do the acinar cells in the pancreas secrete? ______
Where do both the acinar and ductal cells put their secretions? ______
How do the pancreatic secretions help the intestines deal with the acidic chyme?
2nd problem with chyme: It needs to be moved. Absorption works best over a large surface area. Therefore, to effectively absorb the nutrients found in the chyme it needs to move along the length of the intestinal tract. There are four important modulators of motility within the intestine: extrinsic neuronal input, the myogenic reflex (review page 10), intrinsic neuronal input and spontaneous modulators.
Extrinsic Regulators of Motility The word extrinsic means operating from outside the body. When it comes to extrinsic regulators of motility think of modulators that are OUTSIDE of the intestine. The extrinsic modulator of the intestine is the autonomic nervous system. You’ve seen all this information once already. For review on this topic turn to page 16 of this packet.
What are the two branches of the autonomic nervous system?
Following vagal (parasympathetic) stimulation, what neurotransmitter is release? ______
When Ach binds to the smooth muscle tissue, how do intracellular calcium levels change?
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PHSL3051 Dr. Olson’s Notes
Contrast intestinal pacemaker cell’s response to vagal and sympathetic stimulation.
What overall effect does vagal and sympathetic stimulation have on the smooth muscle cells present in the intestine?
Intrinsic Regulators of Motility The word intrinsic, as it relates to physiology, means contained wholly within the organ on which it acts. For the intestine, the intrinsic regulator is the Enteric Nervous System (ENS).
Recognize that the ENS is INDEPENDENT of the central nervous system and is contained entirely within the GI tract.
What are the major differences between a short and long reflex? Where is the control center located for each reflex?
Identify the common types of stimuli that are being sensed in the intestinal wall?
Mechanoreceptors in the intestine sense______.
Chemoreceptors in the intestine sense ______.
List at least two chemicals present in the chyme that could activate the chemoreceptors.
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PHSL3051 Dr. Olson’s Notes
Spontaneous regulators of motility In the intestine, one of the spontaneous factors that govern motility are generated by the BER (see page 16 for review).
The Migrating Motor Complex (MMC) What is the MMC?
What hormone is responsible for initiating the MMC? ______
What type of intestinal movement occurs following activation of the MMC?
Peristalsis or Segmentation
3rd problem with chyme: It needs to be digested. Chyme contains the nutrients our bodies need to generate energy. To access the energy stored the nutrients we need to move them from the lumen of the intestine into the blood. To do this the macronutrients in the chyme need to be digested (broken down into smaller units) to be absorbed through the epithelium.
Define digestion
Fill complete the flow chart below…the controlled variable an empty small intestine.
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PHSL3051 Dr. Olson’s Notes
Into what compartment is CCK released?
What is CCK’s target tissue? What cells specifically does CCK target?
What is the response of these cells? What type of secretion do they produce in response to CCK?
Into what compartment is this secretion being released?
What does this secretion do? What is its target? Where is its target located?
When does this feedback loop stop? In other words, what shuts down this feedback loop? Is this positive or negative feedback?
Somatostatin release (pancreas) What role does somatostatin play in digestion?
Somatostatin is released in multiple places within the body. You’ve already learned that it is released from which organ? ______. Somatostatin is also released from the pancreas.
Regardless of its origin where is somatostatin released?
True or False:
Only the epithelial cells found in the lumen of the intestine will have access to somatostatin because this is where it is released.
Why is this statement True or False?
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PHSL3051 Dr. Olson’s Notes
Complete the flow chart below related to somatostatin
Into what compartment is somatostatin released?
What is Somatostatin’s target tissue? What cells specifically does Somatostatin target? (2 different targets)
Target cell #1______
Target cell #2______
When does this feedback loop stop? In other words, what shuts down this feedback loop? Is this positive or negative feedback?
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PHSL3051 Dr. Olson’s Notes Absorption Now that we have the chyme neutralized and our digestive enzymes are present in the lumen of the intestine, digestion and absorption can begin. There are three macromolecules that need to be broken down in the intestine before they can be absorbed.
Identify the three macronutrients
1. ______2. ______3. ______
When the food enters the intestine, it consists of many “large food particles” that need to be broken down to “smaller food particles.” Enzymes help facilitate this process. In the picture below identify the large food particles, the enzyme and the small food particles.
+
Carbohydrates Identify the larger and smaller food particles for carbohydrates. What enzymes help with its digestion?
Compare and contrast the actions of Maltase, Sucrase and Lactase.
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PHSL3051 Dr. Olson’s Notes
Identify the transport mechanism for individual glucose molecules moving from the lumen of the intestine into the intestinal cell.
Describe the Na/Glucose co transporter. What kind of transporter is this?
Describe the concentration that exists for glucose between the lumen of the intestine and the intracellular compartment?
How does glucose move across the basolateral side of the cell? What does this tell you about the concentration gradient of glucose between the interstitial fluid and the epithelial cell? Protein Identify the larger and smaller food particles for proteins. What enzymes help with its digestion?
Many of the enzymes within the digestive system need to become activated before they can work to break down food particles. What do we call the inactive form of an enzyme? ______.
How is trypsinogen activated? What important role does trypsin play in protein digestion?
Once the protein is broken down, what transporters help move these particles across the apical membrane of the endothelial cell? (3 ways)
Identify the transport mechanism for di- and tripeptides moving from the lumen of the intestine into the intestinal cell? Does it take energy to move these peptides? What kind transport is this?
Identify the transport mechanism for di- and tripeptides moving from the intracellular compartment into the blood? Does it take energy to move these peptides? What kind transport is this?
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PHSL3051 Dr. Olson’s Notes
How do individual amino acids move from the lumen of the intestine into the intestinal cell? Does it take energy to move these peptides? What kind transport is this?
How do di- and tripeptides move from the lumen of the intestine into the intestinal cell? Does it take energy to move these peptides? What kind transport is this?
How does glucose move across the basolateral side of the cell? What does this tell you about the concentration gradient of glucose between the interstitial fluid and the epithelial cell? Fats For a good review check out: https://www.youtube.com/watch?v=VuLg5bmKT8A
Identify the larger and smaller food particles for fats.
What are bile salts and how do they aid in digestion? Define emulsification.
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PHSL3051 Dr. Olson’s Notes
True or False:
Bile salts help break up triglyceride molecules into fatty acids and monoglycerides.
Why is that statement True or False?
What enzymes are responsible for the breakdown of fat? What are the products produced by activation of this enzyme?
Why do lipid droplets need to be broken down if they are lipid soluble? In other words, why can’t lipid droplets directly diffuse through the plasma membrane?
What fat molecules are able to cross the apical intestinal membrane? Do they require a transporter? Why or why not?
Inside of the mucosal cell the fat is repackaged into what? ______
Identify the transport mechanism of fats across the basal lateral membrane.
Why are chylomicrons not absorbed into the blood? If the chylomicrons cannot move into the blood where do they go?
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PHSL3051 Dr. Olson’s Notes
Electrolytes and water absorption
Describe the many ways in which Na enters the intestinal cell.
Water typically follows the movement of solutes…let’s talk about why that is.
How does the osmolarity of the lumen change when ions (Na, K, Cl) move into the intestinal cell?
How does the water concentration in the lumen change when ions move from into the intestinal cell?
Is there a gradient for water to move once the ions have left? If so, which way does water move?
Identify the ways in which water can move from the lumen of the intestine to the extracellular fluid.
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PHSL3051 Dr. Olson’s Notes Mini Lecture: Liver and Large Intestine
• Identify the major structures of the liver from an organ system level down its cellular structures.
• Identify the 3 main vessels that move blood and bile within the liver. Which direction are substances moving (towards or away from the central vein)? Compare the function and content of each vessel within the liver.
• Identify the major structures of the large intestine from an organ system level down its cellular structures.
Liver:• OrganDescribe to Cellular the major Structure functions of the large intestine. Identify the liver and the gall bladder in the image.
What is the role of the gallbladder?
How does bile help with digestion?
Identify the 3 vessels that carry substances to and from the liver.
What kinds of substances are found in the hepatic artery? Is the blood moving toward the center of the liver lobule or away from the center liver lobule?
What kinds of substances are present in the hepatic portal vein? Is the blood moving toward the center of the liver lobule or away from the center liver lobule?
What kind of substances are found in the bile duct? Is the bile moving toward the center of the liver lobule or away from the center liver lobule?
34 Gallbladder stores bile and conjugated toxins PHSL3051 Dr. Olson’s Notes Large Intestine: Organ to Cellular Structure Identify the major structures of the large intestine.
Compare and contrast the small intestinal mucosa with the large intestinal mucosa.
What is the major substance absorbed in the large intestine?
What kinds of channels are present on the absorptive cells found within the mucosa?
What role does mucus secretion play in the large intestine?
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PHSL3051 Dr. Olson’s Notes
Lecture: Liver and Large Intestine Learning objectives:
• Explain the major functions of the liver: bile salts production, alkaline fluid production, carbohydrate metabolism and conjugation of toxic substance. Explain why it is important to conjugate toxins and how they are ultimately removed from the body.
• Explain the major role of the gallbladder and ways it can be stimulated or inhibited. Describe the production and secretion of bile as both a secretory (bile salts) and excretory (conjugated toxins) product. Explain the importance of bile in the emulsification and absorption of lipids. Explain how bile salts are recycled.
• Describe the absorption and motility (haustrations, mass movements and defecation) of the LI.
• Explain the steps within the defecation reflex. Compare the short and long defecation reflex within the rectum. Which reflex plays a larger role in initiating defecation?
• Describe how Hirschsprung’s disease results in constipation and difficulties defecating.
What substances are found in the gall bladder?
How does bile help us digest the food we’ve eaten?
Fill in the blank:
Bile is produced by the ______, stored in the ______and released into the ______duct following a fatty rich meal.
Conjugated toxins are stored in the ______, are released into the ______and are ______from the body through the feces.
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PHSL3051 Dr. Olson’s Notes
What stimulates gallbladder contraction (3 stimuli)? What inhibits gallbladder contraction?
Which of these mechanisms is a feed forward system? Justify your answer.
Liver Functions What are the 3 major functions of the liver?
1. ______2. ______3. ______
Bile What is the major function of bile salts?
Describe how bile salts are recycled.
What percentage of bile salts are lost in the feces? ______%
Where in the intestine are bile salts reabsorbed? ______
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PHSL3051 Dr. Olson’s Notes
Carbohydrate Metabolism What is the liver’s role in carbohydrate metabolism? What is glycogen and what is it used for?
Toxin storage and excretion Why does the liver conjugate toxins? Where are these conjugated toxins released (2 areas)?
Why are some toxins released into the blood while others are released into the lumen of the intestine?
Identify and describe the primary jobs of the large intestine (4 major jobs)
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PHSL3051 Dr. Olson’s Notes
Job #1______
Job #2______
Job #3______
Job #4______
Motility What are the three types of motility that occur in the intestine? Briefly describe each.
What are the major substances absorbed in the large intestine? Why is the presence of Na helpful for the movement of water?
What is the major secretion coming from the large intestine? What purpose does it serve?
Define defecation. What purpose does it serve?
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PHSL3051 Dr. Olson’s Notes Defecation reflexes: There are two reflexes that work together to help you defecate. Which reflex plays a larger role in defecation?
Complete the short defecation reflex:
Hirschsprungs Disease Describe the pathophysiology of Hirschsprung’s disease.
Why does the colon become enlarged?
How is this disease treated?
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