Chapter 23: Digestive System

Place the digestive organs in the following 2 categories: alimentary canal or accessory digestive organs.

*Alimentary canal - mouth, pharynx, esophagus, stomach, small intestine, large intestine. *Accessory digestive organs - teeth, tongue, gallbladder, salivary glands, liver, pancreas.

What are the functions of the bacterial flora of the large intestine?

-Colonize the colon -Ferment indigestible carbohydrates -Release irritating acids and gases (flatus) - *Synthesize B complex vitamins and produces vitamin K (important for clotting)*

List the 3 divisions of the small intestine in the proper order.

1. Duodenum 2. Jejunum 3. Ileum

List the major functions of the digestive system (6) .

1. Ingestion 2. Populsion 3. Mechanical Digestion 4. Chemical Digestion 5. Absorption 6. Defecation

List the 6 essential digestive activities and where they occur in the digestive system.

1. Ingestion- Mouth 2. Propulsion- Oropharynx, esophagus, stomach, small intestine & large intestine. 3. Mechanical Digestion- Mouth, stomach, and small intestine. 4. Chemical Digestion- Stomach and small intestine. 5. Absorption- Lymph vessels, small intestine and large intestine. 6. Defecation- Anus

Identify the 4 layers of a typical GI tract organ and name what tissue comprises each layer.

1. Mucosa: Simple Columnar Epithelium rich in mucus secreting cells. (Innermost layer) 2. Submucosa: Areolar Connective Tissue containing a rich supply of blood and lymphatic vessels & nerve fibers. 3. Muscularis Externa: Smooth muscle cells forms sphincters. 4. Serosa: Areolar connective tissue covered with a single layer of squamous epithelium. (protective outermost layer)

What is amylase, where does it work and what macromolecule does it digest?

A digestive enzyme that helps break down complex carbohydrates, such as starches, into smaller molecules that can be absorbed by the digestive tract.

What is chyme?

A soupy mixture of partially digested food that forms in the stomach. It is highly acidic.

What is a bolus?

A unit of food passed along the digestive system.

What is deglutition?

AKA swallowing. Involves both voluntary action and involuntary action. During the voluntary phase, the bolus is pushed to the back of the mouth by the tongue. The pressure of the bulos on the pharynx activates the swallowing center in the brain that makes the uvula go up, larynx go up, and the epiglottis down to prevent food going to the trachea.

What is the emesis reflex and how can it affect pH?

AKA vomiting. Caused by overdistention of stomach, bacteria, spicy foods, excessive alcohol or drugs. Can lead to alkalosis due to a loss of HCl.

Give the functions of the small intestine.

Absorption and movement of bolus.

Give the number of baby teeth vs adult teeth.

Baby teeth: 20 Adult teeth: 32

List the 3 phases of gastric activity and a summary of the major events in each phase.

Cephalic phase: Prepare stomach for food  Gastric phase: Food processing in stomach Intestinal phase: Passing food to duodenum (chyme)

Give the functions of the mouth, pharynx, esophagus, stomach, small intestine, large intestine, teeth, tongue, gallbladder, the 3 salivary glands, liver, pancreas

Chewing, starts digesting by mechanically and chemically (starches) breaking down food.

Give the functions of the stomach.

Churning; mechanical absorption.

Describe the defecation reflex. What receptors are involved with it?

Distension of rectum caused by feces: Stimulates contraction of the rectal walls Relaxes the internal anal sphincter Voluntary signals stimulate relaxation of the external anal sphincter and defecation occurs gastrocolic reflex - stomach and colon urge to defecate

Give the regions of the large intestine.

Distinct regions: ascending colon, hepatic flexure, transverse colon, splenic flexure, descending colon, and sigmoid colon The sigmoid colon joins the rectum Rectum leads to the anal canal, the last segment of the large intestine which opens to the exterior at the anus

What are villi?

Finger-like projections of the mucosa layer of the small intestine. They increase the surface area of the small intestine to allow for greater absorption of nutrients.

Give the functions of the tongue.

Grips and repositions food during chewing, mixes food with saliva forming the bolus, initiates swallowing, speech, taste, & releases lingual lipase (a digestive enzyme)

Give the functions of the pancreas.

Is responsible for secreting digestive enzymes.

Give the functions of the gallbladder.

It is mainly a storage vessel. It is connected by ducts from both the small intestine and the liver. It stores bile until it is needed in the duodenum.

Give the functions of the liver.

Its major function is to produce & secrete bile. It also separates and filters waste products from nutrients, stores glucose and produces many substances, such as cholesterol and albumin.

What is lipase, nuclease and bile, where do they work and what macromolecules do they digest?

Lipase: Fat digesting enzymes (only found in the small intestine) The small intestine is therefore the sole site of lipid digestion. Nuclease: Found in the small intestine. Digest nucleic acids into nucleotides. Bile: Emulsifies fats. They separate large fat globules into small accessible fatty droplets that provide a large surface area for the fat digesting enzymes to work on.

Give the functions of the teeth.

Mechanically breaks down food.

Provide the functions of saliva.

Moistens & lubricates food in mouth, dissolves food for taste, chemically digests (amylase).

Why does the large intestine have so many goblet cells?

Mucus secretion

What are the secretions of the parietal cells, chief cells, mucous neck cells and G cells?

Parietal Cells: HCI, Intrinsic Factor (which makes B12, w/o = anemia) Chief Cells: Pepsinogen Mucous Neck Cells: Mucous G Cells: Gastrin

What is pepsin, where does it work and what macromolecule does it digest?

Pepsin: A digestive enzyme released by chief cells in the stomach that digests proteins into peptides.

Define peristalsis and give what essential digestive activity is involved with it.

Peristalsis: The movement of food particles through the digestive tract. Rhythmic waves of smooth muscle contractions perform this action. Its involved with propulsion.

What does gastrin, secretin and CCK target? What is the result?

Secretin: from the small intestine promotes secretion of bicarb from pancreas and gallbladder. CKK: from the small intestine promotes the release of bile salts from the gallbladder Gastrin: is a peptide hormone that stimulates secretion of gastric acid (HCl) by the parietal cells of the stomach and aids in gastric motility.

For the stomach, be able to ID the following: cardiac region, pyloric region, cardiac sphincter, pyloric sphincter, in either a picture or in a written question.

See Lab PP.

ID the hard palate, soft palate and uvula.

See lab PP.

What does emulsification mean? What substance does this, and what macromolecule is involved?

Separating large fat globules into small accessible fatty droplets that provide a large surface area for the fat digesting enzymes to work on. (Bile salts from the liver emulsify fat)

What type of tissue lines a villus?

Simple Colunnar

What is the pH of the stomach and why?

Stomach pH: 2 Gastric juice (stomach acid) is composed of hydrochloric acid which is highly acidic which allows it to digest proteins and inactivates most enzymes in food. It also creates an environment that is unfriendly to many microorganisms ingested with food that may be harmful.

ID what tissue lines the mouth and why.

Stratified Squamous Epithelium. Chewing could cause abrasion so stratified squamous is used for protection.

Give the functions of the large intestine.

Takes H2O out of food to prepare for defecation.

Where do pancreatic, liver and gall bladder secretions "join up" with the alimentary canal?

The Duodenum at the hepatopancreatic sphincter.

Compare internal vs external anal sphincter. Which is voluntary? Involuntary?

The internal anal sphincter is involuntary and the external anal sphincter is voluntary.

List the 3 divisions of the pharynx and what kind of material (liquid, food or air) would normally be traveling in each division.

The oro- and laryngo-pharynx allow passage of food and fluids to esophagus. Trachea: only allows air to travel

What is the purpose of bicarbonate secretion?

The pancreas makes bicarbonate ion to neutralize the HCl from the stomach.

What are the functions of the large intestine?

Vitamins, water, and electrolytes are absorbed. Its major function is propulsion of fecal material toward the anus.