The cells in our bodies perform a wide variety of activities such as __________, __________, and __________ of substances across cell membranes.

- protein synthesis

- cell division

- active transport

1. Food must be consumed in order to provide the ______ for these cellular activities.

2. However, the food that you ingest typically contains ________, which are too large to be used by the cells of the body.

1. energy

2. polymers

The ________ in food must first be broken down into ________ that are small enough to be taken up by cells and then used for energy.

- polymers

- monomers

The process by which the polymers in food are broken down into their constituent monomers is called ________.

digestion

Digestion involves _____________ that __________ the polymers in the food in the lumen of the digestive tract.

- digestive enzymes

- catabolize (break down)

As the monomers are released, they are absorbed from the ______ of the digestive tract into the ______ and then transported to the ______ in the rest of the body.

- lumen

- blood

- cells

Once inside of the cells, the monomers are further broken down via the process of ____________ in order to provide ATP as the energy source for different cellular activities.

cellular (aerobic) respiration

The organs of the digestive system are divided into 2 main groups. What are they?

1. gastrointestinal (GI) tract

2. accessory organs

What consists of organs that collectively form a continuous tube?

gastrointestinal (GI) tract

Name the organs of the gastrointestinal (GI) tract? (7 total)

1. mouth

2. pharynx

3. esophagus

4. stomach

5. small intestine

6. large intestine

7. anus

connected to but are not continuous with the organs of the GI tract

accessory organs

Name all of the accessory organs of the digestive system. (6 total)

1. teeth

2. tongue

3. salivary glands

4. pancreas

5. liver

6. gallbladder

What are the six basic processes that the digestive system performs?

1. ingestion

2. secretion

3. motility

4. digestion

5. absorption

6. defecation

In general, the organs of the GI tract consist of the same 4 layers. What are they?

1. mucosa

2. submucosa
3. muscalaris

4. serosa

inner layer of the GI tract

mucosa

What are the 3 layers that make up the mucosa of the GI tract?

1. epithelium

2. lamina propria

3. muscalaris mucosae

located closest to the lumen of the GI

epithelium

consists of connective tissue containing collagen fibers, elastic fibers, blood vessel, and lymphatic vessels

lamina propria

consists of a thin layer of smooth muscle

muscularis mucosae

What does the submucosa consist of? (4 total)

1. connective tissue containing collagen fibers

2. elastic fibers

3. blood vessels

4. lymphatic vessels

consists of either skeletal muscle or smooth muscle, depending on the organ

muscularis

1. The muscularis of the mouth, pharynx, and upper esophagus contains ___________.

2. The muscularis of the rest of the GI tract (lower esophagus, stomach, small intestine, and large intestine) contains ___________.

1. skeletal muscle

2. smooth muscle

1. The smooth muscle is usually arranged into an __________ layer and an ____________ layer.

2. Contraction of the smooth muscle in the muscularis is responsible for ________.

1. inner circular; outer longitudinal

2. peristalsis

wave-like contractions within the wall of the GI tract that propel food over a long distance in an anal-ward direction

peristalsis

- Similar to squeezing a tube of toothpaste from the bottom to the top of the tube

What is the function of peristalsis?

To propel food down the lumen of the GI tract from the esophagus to the anus.

Peristaltic contractions occur throughout the GI tract, but the intensity of these contractions varies depending on the location. They are strong in the ________, moderate in the ________, and weak in the ________.

- esophagus

- stomach

- intestines

- also called the peritoneum

- the outer layer of the GI tract

- consists of epithelial tissue and connective tissue

serosa

1. The _______________ consists of about 100 million neurons found within the wall of the GI tract.

2. Arranged into two plexuses (groups) of neurons, what are they?

1. enteric nervous system (ENS)

2. submucosal plexus and myenteric plexus

- also known as the plexus of Meissner

- located in the submucosa

- regulates GI secretion

submucosal plexus

- also known as the plexus of Auerbach

- located in the muscularis

- regulates GI motility (movement)

myenteric plexus

1. __________ nerves innervate the organs of the GI tract via the ________ nerves.

2. Stimulation of these nerves to the GI tract ______ peristalsis and GI secretion of fluids (gastric juice, pancreatic juice, intestinal juice, etc.) into the GI lumen.

1. Parasympathetic; Vagus (X)

2. increases

1. The organs of the GI tract are also innervated by ________ nerves.

2. Stimulation of these* nerves to the GI tract ______ peristalsis and GI secretion.

3. In addition, stimulation of these* nerves also causes ________ of the blood vessels that supply the organs of the GI tract, which results in shunting blood away from these organs.

1. sympathetic

2. inhibits

3. vasoconstriction

1. contains the oral cavity

2. surrounded by what 5 parts?

1. the mouth

2. lips, cheeks, hard palate, soft palate, tongue

- forms the anterior region of the roof of the mouth

- consists of bones (maxilla and palatine) covered by a mucosa

hard palate

- forms the posterior region of the roof of the mouth

- consists of skeletal muscle that is covered by a mucosa

soft palate

1. The _____ is an extension of the soft palate.

2. During __________, the soft palate closes off the entrance to the nasal cavity, thereby preventing reflux of food into the nose

1. uvula

2. deglutition (swallowing)

1. forms the floor of the mouth

2. consists of what 2 components?

1. tongue

2. mucosa and skeletal muscle

- the outer layer of the tongue

- consists of epithelium and connective tissue

- contains taste buds and lingual glands

mucosa

1. The ________ of the tongue are involved in the detection of taste.

2. The lingual glands of the tongue are ______ glands that secrete the enzyme __________ into the oral cavity.

1. taste buds

2. exocrine; lingual lipase

Lingual lipase initiates the digestion of ________ in small globules of fat.

triglycerides

triglyceride is broken down by lingual lipase into → 2 _______, 1 ________

2 fatty acids, 1 monoglyceride

- form the inner layer of the tongue

- responsible for the movements of the tongue during speech and also during ingestion

- Posteriorly, the mouth becomes continuous with the pharynx

skeletal muscle

1. An adult contains __ permanent teeth, which have replaced the __ deciduous teeth (baby teeth).

2. What are the 4 groups of adult teeth?

1. 32 (16 on the top and 16 on the bottom); 20

2. incisors, canines, premolars (bicuspids), molars (tricuspids)

1. The teeth insert into the ______ of the alveolar processes of the maxilla and mandible.

2. The border of the alveolar processes is lined by a mucosa called the ________.

1. sockets

2. gingivae (gums)

1. Each tooth is held in the alveolar socket by a ____________.

2. Recall that the joint formed between each tooth and the alveolar socket via this* is called a ________, which is a type of __________.

1. periodontal ligament

2. gomphosis; synarthrosis (immovable joint)

A tooth consists of 3 external regions, what are they?

1. crown

2. neck

3. root

- the exposed part of the tooth that is above the gingiva

crown

- the part of the tooth that is flush with the gingiva

- connects the crown with the root

neck

- the part of the tooth that is below the gingiva and inserts into the alveolar socket

root

What are the layers of the tooth?

1. enamel

2. dentin

3. pulp cavity

- the outer layer of the tooth

- calcified substance that is harder than bone

- harder than bone because it contains more _________ (i.e. crystals of calcium phosphate) compared to bone.

- enamel

- hydroxyapatite

- Hydroxyapatite crystals make up 97% of enamel’s weight, whereas they comprise only 65% of the weight of bone.

- the middle layer of the tooth

- forms the majority of the tooth

- calcified substance that has a hardness that is intermediate between bone and enamel

dentin

- Hydroxyapatite crystals constitute about 70% of dentin’s weight.

1. located internally to dentin

2. contains _____, which consists of connective tissue containing blood vessels and nerves

1. pulp cavity

2. pulp

- In the crown and neck of the tooth, the pulp cavity is dilated.

In the root, the pulp cavity tapers off, forming the ________, which eventually opens up at the end of the tooth as the ________.

- root canal

- apical foramen

The teeth crush and tear food during __________.

mastication (chewing)

1. exocrine glands that produce saliva

2. Name its 3 pairs.

1. salivary glands

2. parotid, submandibular, and sublingual

- salivary glands located anterior to each ear

parotid glands

- salivary glands located beneath the mandible

submandibular glands

- salivary glands located beneath the tongue

sublingual glands

- Note that each salivary gland has a duct that empties a portion of the saliva into the oral cavity.

How much saliva is produced by the salivary glands each day?

1 L

Saliva Composition.

- constitutes 99% of saliva

- This* in saliva dissolves any food taken into the mouth.

H2O

Saliva Composition.

- The HCO3- ____ in saliva buffer any ingested food that is acidic (like tomato sauce).

ions (HCO3-, Na+, K+, and, Cl- )

Saliva Composition.

Enzyme that hydrolyzes a large starch molecule into several short chains of glucose molecules called ________.

- salivary amylase

- α-dextrins

The ______ in saliva lubricates food.

mucus

- an enzyme that destroys bacteria

- the ________ in saliva protects the mouth from pathogens.

lysozyme

- Recall that __________ is produced by the lingual glands of the tongue, not by the salivary glands.

- Nevertheless, once it is secreted by the lingual glands, it then mixes with the other components of saliva.

lingual lipase

- also called the throat

- a tube that is located between the nasal cavity and the esophagus

pharynx

- The pharynx consists of an inner mucosa and an outer muscularis that consists of skeletal muscle.

What are the 3 regions of the pharynx? Describe them.

1. nasopharynx - the region of the pharynx that is continuous with the nasal cavity

2. oropharynx - the region of the pharynx that is continuous with the oral cavity (mouth)

3. laryngopharynx - the region of the pharynx that is continuous with the larynx and with the esophagus

The pharynx is involved in 2 major functions. What are they?

1.  Passageway for the movement of food and beverages from the mouth to the esophagus.

2. Passageway for the movement of air from the nose and mouth to the larynx.

- a tube that is located between the pharynx and the stomach

esophagus

The muscularis in the upper half of the esophagus consists of __________, while the muscularis in the lower half of the esophagus contains __________.

- skeletal muscle

- smooth muscle

Each end of the esophagus is modified into a sphincter. What are their names and what do they consist of?

- upper esophageal sphincter (UES) - consists of skeletal muscle

- lower esophageal sphincter (LES) - consists of smooth muscle

a region of muscle that regulates the opening to the lumen of an organ

sphincter

Esophagus Function. (5)

1. During swallowing, the ____ opens to allow food to enter into the esophagus from the pharynx. 

2. Once food is in the esophagus, the *** closes, preventing _____  of food into the pharynx.

3. Food is then propelled down the esophagus via ________.

4. The ____ opens in order to allow the food to move out of the esophagus and into the stomach.

5. Once the esophagus is empty, the *** closes in order to prevent reflux of food and __________ into the esophagus.

1. UES

2. reflux

3. peristalsis

4. LES

5. gastric contents

This is  located between the esophagus and the small intestine.

What are its 4 major regions?

stomach

1. cardia

2. fundus

3. body

4. pylorus

- the initial region of the stomach

- separated from the esophagus via the lower esophageal sphincter (LES).

cardia

- the region of the stomach that is superior and lateral to the cardia

fundus

- the large, central region of the stomach

body

- the terminal region of the stomach

- divided into 2 subcomponents, what are they?

pylorus

1. pyloric antrum - located closest to the body of the stomach

2. pyloric canal - located closest to the duodenum of the small intestine

The pyloric canal is separated from the duodenum by the __________, which consists of smooth muscle.

pyloric sphincter

The stomach consists of the same 4 layers as the rest of the GI tract, what are they?

1. mucosa

2. submucosa

3. muscalaris

4. serosa

1. The stomach produces __________.

2. Each day the stomach secretes about ____ of this*.

1. gastric juice

2. 2 L

Gastric juice is produced by __________ that are located in the mucosal epithelium of the stomach.

gastric glands

Each gastric gland contains 4 cell types, what are they?

1. mucous neck cells

2. parietal cells

3. chief cells

4. G cells

secrete mucus into the stomach lumen

mucous neck cells

secretes hydrochloric acid (HCl) and intrinsic factor (IF) into the stomach lumen

parietal cells

- also called zymogenic cells

- secrete pepsinogen and gastric lipase into the stomach lumen

chief cells

Pepsinogen is the ______ form of the enzyme pepsin. Pepsinogen is converted into the ______ form pepsin via ____. 

- inactive

- active 

- HCl

enteroendocrine cells that secrete the hormone gastrin into the blood

G cells

- a strong acid

- causes gastric juice to have a low pH value of 2

- kills pathogens in food and it provides the acidic pH that is required for pepsin and gastric lipase to function.

HCl (hydrochloric acid)

- a protease that catabolizes proteins into smaller peptides

- this* functions only in an acidic environment, which is provided by the HCl in gastric juice.

pepsin

- Note that pepsin is an unusual enzyme in this respect; most other enzymes in the digestive tract (and in the body) require a neutral to slightly alkaline pH (i.e. a pH of 7 to 8) to function optimally.

- Like lingual lipase, this* is an enzyme that catabolizes triglycerides in a small fat globule into fatty acids and monoglycerides.

- Like pepsin, it also requires an acidic pH to function.

gastric lipase

found in gastric juice; coats the surface of the gastric mucosa, thereby protecting these cells from HCl.

mucus

a protein that helps vitamin B12 undergo absorption in the small intestine

intrinsic factor

- We obtain Vitamin B12 from the diet (meat and dairy products) and it is necessary for erythropoiesis.

- If intrinsic factor is not produced, vitamin B12 will not undergo absorption and the individual will have difficulty producing red blood cells -- a condition called pernicious anemia.

The stomach converts food into ______.

chyme

Once food enters the stomach, the ________ in the lower body and pylorus of the stomach contracts and the food is mixed with gastric juce. The ____, ______, and _______ in the gastric juice further break down the large particles in food into smaller particles, resulting in the formation of chyme. Therefore, chyme is a thin, soupy mixture that consists of partially digested food and digestive fluids.

- muscularis

- HCl

- pepsin

- gastric lipase

Some of the chyme moves through the pyloric sphincter and into the ________ of the small intestine, a process called __________. This* is a slow process: only __ mL of chyme are emptied at any given time. Realize that this* should be a slow process in order to prevent the small intestine from being overloaded with chyme.

- duodenum

- gastric emptying

- 2

About __ L of food can be stored temporarily in the ______ and upper body of the stomach while waiting to be converted into chyme.

- 2

- fundus

1. The stomach produces the hormone ______.

2. ______ in gastric glands secrete this hormone into the blood.

1. gastrin

2. G cells

The _______ is a gland that is posterior to the stomach and lateral to the duodenum of the small intestine.

pancreas

The pancreas consists of what 3 external components?

1. head

2. body

3. tail

The pancreas is both an _______ gland and an _______ gland.

- endocrine

- exocrine

Internally, the pancreas consists of what 2 major components?

1. pancreatic islets

2. acini

- also called islets of Langerhans

- comprise 1% of the total weight of the pancreas and are found scattered throughout the pancreas

pancreatic islets

Each pancreatic islet consists of a cluster of endocrine cells:

1. ________: secrete the hormone glucagon into the blood

2. ________: secrete the hormone insulin into the blood

1. alpha (α) cells

2. beta (β) cells

constitutes about 99% of the total weight of the pancreas

acini

1. Each acinus consists of several ______ cells called ______ cells that secrete pancreatic juice into a small duct.

2. The small ducts that surround these* cells empty into the large ___________.

1. exocrine; acinar

2. pancreatic duct (duct of Wirsung)

3. The pancreatic duct unites with the __________ to form the _____________, which opens into the lumen of the duodenum. The opening of this* is regulated by a region of smooth muscle that is called the ____________.

- common bile duct

- hepatopancreatic ampulla (ampulla of Vater)

- sphincter of the hepatopancreatic ampulla (sphincter of Oddi)

The pancreas is involved in 3 major functions. What are they?

1. produces pancreatic juice

2. produces the hormone insulin

3. produces the hormone glucagon

The acinar cells of the pancreas secrete about 2 L of ________ into the pancreatic duct on a daily basis.

pancreatic juice

What are the 3 components of pancreatic juice? Which one is the main component?

1. H2O: main component

2. ions (HCO3- , Na+ , Cl- , and K+ ): The HCO3- causes the pancreatic juice to have a slightly alkaline pH of 7.5 to 8.

3. enzymes: Pancreatic juice contains many types of digestive enzymes that continue to digest food particles in the chyme that enters the lumen of the small intestine

Pancreatic juice enzymes.

What are the 4 proteases in pancreatic juice?

1. trypsin

2. chymotrypsin
3. elastase

4. carboxypeptidase

Pancreatic juice enzymes.

1. Which proteases of pancreatic juice catabolize proteins into smaller peptides?

2. Which proteases cleave off individual amino acids from smaller peptides?

1. Trypsin, chymotrypsin, and elastase

2. carboxypeptidase, along with the small intestinal brush border enzyme aminopeptidase

Pancreatic juice enzymes.

1. Pancreatic proteases are initially released as ____________.

2. Trypsinogen is first activated to trypsin by the small intestine brush border enzyme ________.

3. Once activated, trypsin in turn activates the remaining ____________ (chymotrypsinogen, proelastase, and procarboxypeptidase) to produce chymotrypsin, elastase, and carboxypeptidase, respectively.

1. inactive precursors (trypsinogen, chymotrypsinogen, proelastase, and procarboxypeptidase)

2. enterokinase

3. inactive precursors

an enzyme that hydrolyze triglycerides in a small fat globule into fatty acids and monoglycerides

pancreatic lipase

enzyme that hydrolyzes starch into α-dextrins, which are short chains of glucose molecules

pancreatic amylase

1. The pancreas uses its pancreatic juice to further digest ________, ________, and ____ that are in the chyme in the lumen of the small intestine.

2. In order to achieve this goal, the __________ must be open during the digestion of a meal, thus allowing pancreatic juice to move into the small intestine to interact with the chyme

1. carbohydrates, proteins, fats

2. sphincter of Oddi (When there is no chyme present in the small intestine, the sphincter of Oddi is closed and pancreatic juice remains in the pancreas.)

1. The _____ must be neutralized because pancreatic enzymes as well as small intestinal enzymes require a neutral to slightly alkaline pH to function optimally.

2. In the absence of these enzymes, there is _________ of nutrients.

1. chyme

2. malabsorption

- weighs about 3 lbs and is the largest gland in the body.

- located below the diaphragm

liver

1. consists of 2 major lobes: the right lobe and the left lobe

2. consists of cells called _________

1. liver

2. hepatocytes

1. The liver screens ______ for excess nutrients and toxic substances.

2. The hepatocytes screen the *** from the ____________ for excess nutrients and toxic substances.

1. blood

2. hepatic portal vein

1. If there is excess glucose, the hepatocytes take up the glucose and store it as _______.

2. Excess ______ (A, D, E, K, and B12) and ______ (iron and copper) in the blood are also removed and stored in the hepatocytes.

3. Any __________ (like drugs and alcohol) are removed and detoxified by the hepatocytes and then either reintroduced back into the blood or excreted into bile.

1. glycogen

2. vitamins; minerals

3. toxic substances

The liver produces bile.

1. The hepatocytes of the liver also produce bile and then secrete it into the ________ or ________.

2. These* then combine to form the ________, which emerges from the liver.

1. right hepatic duct; left hepatic duct

2. common hepatic duct

The liver produces bile.

3. The common hepatic duct combines with the ________ extending from the gallbladder to form the __________. This* is so-named because it contains fresh bile from the liver via the hepatic ducts and stored bile from the gallbladder via the ***.

4. The common bile duct eventually unites with the ________ to form the ____________, which empties into the duodenum.

5. Recall that the __________ regulates the opening of the hepatopancreatic ampulla. During the digestion of a meal, this* is open and bile is released into the duodenum to interact with chyme that is present there. When digestion is not occurring, this* is closed and any bile produced by the liver backs up into the cystic duct and then goes to the gallbladder for storage.

3. cystic duct; common bile duct

4. pancreatic duct; hepatopancreatic ampulla

5. sphincter of Oddi

- a fluid that is yellow to green in color

- pH is slightly alkaline (7.5 to 8)

- the hepatocytes of the liver secrete about ___ of this* on a daily basis. 

bile

- 1 L

What are the 4 components of bile? Which one is the biggest component?

1. H2O (majority constituent, makes up 97% of bile)

2. cholesterol

3. bile salts

4. bile pigments

- derivatives of cholesterol

- Examples: glycocholate, taurocholate

- these* are ________; this means that each one* has a hydrophilic region and a hydrophobic region.

bile salts

- amphipathic

The main pigment found in bile is _______, which has a yellowish green color.

bile pigments

- bilirubin

Origin of Bilirubin.

1. Recall that macrophages in the spleen break down worn-out red blood cells. During this process, the __________ of the heme in hemoglobin is eventually converted to bilirubin, which is subsequently released into the blood.

2. The ________ remove the bilirubin from the blood and then secrete it as a component of bile.

3. The ________ of bile promote the emulsification of fat, which is vital to the digestion and absorption of lipids by the small intestine.

1. porphyrin ring

2. hepatocytes

3. bile salts

the process by which a large fat globule is converted into many small fat globules

emulsification

- Emulsification of fats must occur before pancreatic lipase can act on the triglycerides in the fat globule.

Fate of Bile.

1. Bile is released into the lumen of the ________.

2. As bile moves through the small intestine, it mixes with _____, promoting fat emulsification.

1. duodenum

2. chyme

Fate of Bile.

3. Near the end of the small intestine, the bile salts are absorbed into the blood and eventually return back to the liver via the hepatic portal vein. The hepatocytes remove the bile salts from the blood and use them to make more bile. This process of moving the bile from the small intestine back to the liver is called the ____________, which functions to recycle the bile salts.

4. The rest of the bile components (H2O, cholesterol, and bilirubin) continue into the large intestine as part of chyme and eventually become part of the feces. During this process, bilirubin is eventually converted into a brown pigment called ________. This* is responsible for the brown color of feces

3. enterohepatic circulation

4. stercobilin

1. A pear-shaped organ that is located underneath the liver

2. What are it's 3 layers?

1. gallbladder

2. mucosa, smooth muscle, serosa

Gallbladder.

- inner layer

- surrounds the lumen

- consists of an epithelial layer and a connective tissue layer

mucosa

Gallbladder.

- middle layer

smooth muscle

Gallbladder.

- outer layer

- connective tissue

serosa

What are the 2 major functions of the gallbladder?

1. stores bile

2. concentrates bile

1. When digestion is not occurring, the ___________ is closed and bile backs up into the gallbladder for storage.

2. The gallbladder is a small organ and can hold about ____ of bile at one given time. However, the liver secretes about ____ of bile per day.

3. Hence, the gallbladder concentrates the bile (and hence reduces the volume) by removing some of the _____.

1. sphincter of Oddi

2. 50 mL; 1000 mL

3. water

1. Located between the stomach and the large intestine

2. What are its dimensions?

1. small intestines

2. Diameter: 1 inch, Length: 20 feet

- The small intestine is the longest part of the digestive tract.

The small intestine consists of 3 major external regions. What are they?

1. duodenum

2. jejunum

3. ileum

- the initial portion of the small intestine

- this* is separated from pyloric canal of the stomach via the __________

duodenum

- pyloric sphincter

- the middle portion of the small intestine

jejunum

- the terminal and longest portion of the small intestine

- this* is separated from the cecum of the large intestine by the __________

ileum

- ileocecal sphincter

The small intestine consists of the same 4 layers as the rest of the GI tract. What are they?

mucosa, submucosa, muscularis, and serosa

- Note that the mucosa of the small intestine differs from the mucosa of the rest of the GI tract due to modifications in the epithelium and lamina propria.

The epithelium of the small intestinal mucosa contains a superficial covering and lining epithelium that is surrounded by intestinal glands called ______________.

crypts of Lieberkuhn

The covering and lining epithelium consists of 2 types of cells. What are they?

1. absorptive cells

2. goblet cells

absorb nutrients (monomers) from the lumen of the small intestine

absorptive cells

secrete mucus into the lumen of small intestine

goblet cells

- also called an intestinal gland

- consists of 6 types of cells. Name all 6.

crypts of Lieberkuhn

1. absorptive cells

2. goblet cells

3. Paneth cells

4. S cells

5. I cells

6. K cells

- secrete lysozyme into the lumen of the small intestine

- recall that lysozyme is an enzyme that destroys bacteria; in this case, it is used to kill any bacteria that contaminate the intestinal chyme.

Paneth cells

enteroendocrine cells that secrete the hormone secretin into the blood

S cells

enteroendocrine cells that secrete the hormone cholecystokinin (CCK) into the blood

I cells

- enteroendocrine cells that secrete the hormone gastric inhibitory peptide (GIP) into the blood

- Gastric inhibitory peptide is also called glucose-dependent insulinotropic peptide

K cells

Each day the crypts of Lieberkuhn secrete about ___ of intestinal juice that mixes with incoming chyme, bile, and pancreatic juice.

1 L

What are the 3 components of intestinal juice?

1. H2O -major constituent

2. mucus

3. ions (HCO3 - , Na+ , and Cl- )

- The bicarbonate ions give intestinal juice an alkaline pH, ranging from 7.5 to 8.

- The slightly alkaline pH of intestinal juice helps to provide the ideal environment for small intestinal enzymes and for pancreatic enzymes.

The lamina propria of the small intestinal mucosa contain connective tissue and ______.

lacteals

- specialized lymphatic vessels involved in fat absorption

- Unlike the rest of the GI tract, the lamina propria of the small intestine contains these*

lacteal

The mucosa of the small intestine is folded extensively to increase surface area for ________.

absorption

the movement of digested food (monomers) from the lumen of the gastrointestinal tract into the blood

absorption

- Most absorption occurs in the small intestine and to a lesser extent in the large intestine

Absorption in the small intestine occurs due to 3 types of folds. What are they?

1. circular folds

2. villi

3. microvilli

- also called plicae circularis

- folds of the mucosa and submucosa

- increase the absorptive surface area of the small intestine about 3 times

circular folds

- finger-like projections of the mucosa caused by the folding of its epithelium cells and lamina propria

- give the small intestine a velvety appearance

- increase the absorptive surface area of the small intestine about 10 times

- Each one contains an overlying covering and lining epithelium and a core of capillaries and lacteals from the lamina propria

villi

1. The thin, folded structure of the villus facilitates ________ of nutrients in the small intestine:

2. Nutrients easily pass from the lumen of the small intestine through the absorptive cells covering the _____ and then into the capillary or lacteal (depending on nutrient type) to complete the absorption process.

1. absorption

2. villus

- folds of the apical (luminal) membranes of the absorptive cells of the mucosa

- also referred to as the brush border because they resemble the bristles of a brush.

- increase the absorptive surface area of the small intestine about 20 times

microvilli

Collectively, the circular folds, villi, and microvilli increase the absorptive surface area of the small intestine by a factor of _______.

600 (3 x 10 x 20)

1. The small intestine ________ the digestion of nutrients.

2. The absorptive cells of the small intestinal mucosa possess several types of digestive enzymes that are located in their brush borders; these _____________ complete the digestion of food.

1. completes

2. brush border enzymes

What are the 3 types of brush boarder enzymes?

1. α-dextrinase

2. disaccharidases

3. aminopeptidase

- hydrolyzes α-dextrins into individual glucose molecules

α-dextrinase

- hydrolyze disaccharides into monosaccharides

disaccharidases

- hydrolyzes maltose into 2 molecules of glucose

maltase

- hydrolyzes sucrose into a molecule of glucose and a molecule of fructose

sucrase

- hydrolyzes lactose into a molecule of glucose and a molecule of galactose

lactase

1. The small intestine absorbs ______.

2. Once digestion is completed by the brush border enzymes, the ________ are then absorbed by the absorptive cells of the small intestine.

1. solutes

2. monomers

1. Transporters within the _____________ of each absorptive cell absorb any monosaccharides (glucose, galactose, or fructose) or amino acids that many be present in the small intestinal lumen.

2. Transporters are required for movement across the cell membranes of the absorptive cells because carbohydrates and amino acids are ________, while the phospholipids in the cell membranes are ________.

1. plasma membrane

2. hydrophilic; hydrophobic

1. Digestion of triglycerides by pancreatic lipase typically liberates monoglycerides and fatty acids, which can be either ________ fatty acids or _________ fatty acids.

2. Recall that fatty acids and monoglycerides are ________; consequently, they can move across the cell membrane of an absorptive cell without the help of a transporter.

1. long chain; short chain

2. hydrophobic

1. Since ________ fatty acids are so small, they can be absorbed into the blood, which is hydrophilic.

2. _________ fatty acids and monoglycerides, however, are large and hydrophobic. Thus, they cannot be absorbed into the blood directly.

1. short chain

2. Long chain

Lipid absorption.

1. Once inside of an absorptive cell, several long chain fatty acids and monoglycerides recombine to form triglycerides. The triglycerides are then surrounded by a protein coat, forming a ________, which is a type of ________.

- chylomicron

- lipoprotein

Lipid absorption.

2. The chylomicrons then undergo exocytosis across the basolateral membrane of the absorptive cell and subsequently move into the ______ to become part of the lymph.

lacteals

Lipid absorption.

3. From the lymph, the chylomicrons eventually are dumped into the blood. Hence, chylomicrons increase the solubility of the ____________ and ____________ in the blood. 

- long chain fatty acids

- monoglycerides

The small intestine absorbs H2O.

1. The absorptive cells of the small intestine also absorb water from chyme via ________.

2. About ___ of the 9 L of fluid that enters the small intestine is absorbed.

3. The small intestine is the major site of _____ absorption in the GI tract.

1. osmosis (i.e. the water follows the absorbed solute)

2. 8 L

3. water

The small intestine secretes hormones.

These hormones include ___, ______, and ___.

CCK, secretin, and GIP

1. Located after the small intestine and is the last organ of the gastrointestinal tract

2. What is its diameter and length?

1. large intestine

2. diameter = 2.5 in. | length = 5 ft.

- Compared to the small intestine, the large intestine has a greater diameter (hence the name “large”) and a shorter length.

The large intestine is divided into 3 major external regions. What are they?

1. cecum

2. colon

3. rectum

- the beginning portion of the large intestine

- this* is separated from the ileum of the small intestine by the __________.

- attached to the lower end of this* is the ______________

- cecum

- ileocecal sphincter

- wormlike appendix (also called the vermiform appendix)

1. In humans, the appendix is a __________, which means that it is a useless organ that has no known function in the body.

2. Structurally, it consists of scattered ____________ that plays an insignificant role in immunity.

1. vestigial organ

2. reticular connective tissue

Name the 4 sections of the colon.

1. ascending colon

2. transverse colon

3. descending colon

4. sigmoid colon

- the terminal portion of the large intestine

- at the very end of this* is the anus.

rectum

1. The region of the rectum that opens up to the exterior

2. Surrounded by what 2 sphincters?

1. anus

2. internal anal sphincter and external anal sphincter

- consists of smooth muscle

- this sphincter is controlled involuntarily

internal anal sphincter

- consists of skeletal muscle

- this sphincter is under voluntary control

external anal sphincter

The mucosal epithelium of the large intestine, that like of that small intestine, consists of a ______________ and lining epithelium that is surrounded by deep ____________.

- superficial covering

- crypts of Lieberkuhn

Covering and lining epithelium of large intestine consists of _________ and _________.

- absorptive cells (absorb H2O from the lumen of the large intestine)

- goblet cells (secrete mucus into the lumen of the large intestine)

also called an intestinal gland

- consists of

a. absorptive cells (absorb H2O from the lumen of the large intestine)

b. goblet cells (secrete mucus into the lumen of the large intestine)

crypt of Lieberkuhn

Notice that the crypts of Lieberkuhn in the large intestine lack ________ cells (I, K, and S cells) and ______ cells found within the crypts of Lieberkuhn in the small intestine

- enteroendocrine

- paneth

The absorptive cells of the large intestinal mucosa do contain microvilli; however, there are no _____ present.

villi

Consequently, the absorptive surface area of the large intestine is significantly _____ than that of the small intestine.

lower

- This should make sense because more absorption occurs in the small intestine than in the large intestine.

The smooth muscle of the large intestinal muscularis is divided into bands called _________ that are visible underneath the serosa.

taenia coli

The taenia coli are usually contracted, causing pouches called ______ to form in the wall of the large intestine.

haustra

The large intestine has 3 major functions. What are they?

1. further processes intestinal chyme using enteric bacteria

2. absorbs H2O

3. forms and stores feces

What does the chyme entering the large intestine consist of?

1. water (about 1 L)

2. waste products

3. indigestible materials

4. the bile pigment bilirubin

Recall that ________ (but not bilirubin) were absorbed near the end of the small intestine as part of the enterohepatic circulation.

bile salts

Living within the large intestine are __________ (usually a harmless strain of Escherichia coli).

enteric bacteria

The enteric bacteria convert some of the chyme’s undigestible carbohydrates and peptides into gases like ______ (CH4), H2, CO2, and ________ (H2S), which smells like rotten eggs

- methane

- hydrogen sulfide

- These gases contribute to intestinal flatus (also called flatulence if excessive).

The enteric bacteria convert bilirubin into ________, a brown pigment.

stercobilin

About ___ mL of the 1 L of H2O that enters the large intestine is absorbed; the remaining passes out of the body as part of the feces.

900 mL

As H2O is absorbed in the large intestine, the chyme in the lumen gradually solidifies into ______.

feces

Defecation Reflex

1. __________ that involves peristaltic contractions in the wall of the rectum, thereby extruding feces out of the body.

2. It takes about __ to __ hours for food to complete its course through the digestive system.

3. ________ are digested the quickest, proteins are intermediate, and lipids take the longest.

1. Spinal reflex

2. 3 to 10 hours

3. Carbohydrates

The regulation of the digestive system involves 3 sequential phases. What are they?

1. cephalic phase

2. gastric phase

3. intestinal phase

Regulation of the Digestive System.

- the first phase

- during this phase, the sight, smell, thought, or initial taste of food causes salivation and gastric juice production in order to prepare the GI tract for the food that is about to be digested.

cephalic phase

- The cephalic phase of digestion involves the ANS

Regulation of the Digestive System.

- the second phase

- begins as soon as food enters the stomach

gastric phase

What 4 activities occur during the gastric phase of digestion?

1. gastric secretion and motility (this promotes the formation of gastric chyme)

2. contraction of the LES (this prevents reflux of gastric juice into the esophagus)

3. relaxation of the pyloric sphincter (this promotes gastric emptying)

4. gastrocolic reflex

- the presence of food in the stomach causes increased motility in the colon

- this reflex clears out the intestinal chyme/feces from the last meal to make way for the new chyme it is about to receive.

- it is because of this* that a person has an urge to defecate during or just after a meal.

gastrocolic reflex

The gastric phase is mediated by the hormone ______.

gastrin

Regulation of Digestive System.

- the third phase

- begins as soon as a significant amount of chyme enters into the small intestine

intestinal phase

What 3 activities occur during the intestinal phase of digestion?

1. release of pancreatic juice and bile into the lumen of the small intestine (The pancreatic juice and bile aid the small intestine in the digestion of food particles in luminal chyme)

2. inhibition of gastric motility, secretion, and emptying (This prevents the small intestine from being overloaded with too much chyme)

3. a feeling of satiety is experienced

The intestinal phase is mediated by several hormones: ______, ________, and ___.

secretin, cholecystokinin, and GIP

Give the name, type, and function of cranial nerve I.

Name: Olfactory

Type: Sensory

Function: Sense of smell

Give the name, type, and function of cranial nerve II.

Name: Optic

Type: Sensory

Function: Vision

Give the name, type, and function of cranial nerve III.

Name: Oculomotor

Type: Motor

Function: Raise eyelids, move eyes, regulate size of pupils, focus of lenses

Give the name, type, and function of cranial nerve IV.

Name: Trochlear

Type: Motor

Function: Eye movements, proprioception

Give the name, type, and function of cranial nerve V.

Name: Trigeminal

Type: Mixed

Function: Sensations of the head and face, chewing movements, and muscle sense.

Give the name, type, and function of cranial nerve VI.

Name: Abducens

Type: Motor

Function: Produce movement of the eyes

Give the name, type, and function of cranial nerve VII.

Name: Facial

Type: Mixed

Function: Facial expressions, secretion of saliva, taste

Give the name, type, and function of cranial nerve VIII.

Name: Vestibulocochlear

Type: Sensory

Function: Balance or equilibrium sense, hearing

Give the name, type, and function of cranial nerve IX.

Name: Glossopharyngeal

Type: Mixed

Function: Taste and other sensations of tongue, swallowing, secretion of saliva, aid in reflex control of blood pressure and respiration

Give the name, type, and function of cranial nerve X.

Name: Vagus

Type: Mixed

Function: Transmit impulses to muscles associated with speech, swallowing, the heart, smooth muscles of visceral organs in the thorax, and abdomen

Give the name, type, and function of cranial nerve XI.

Name: Accessory

Type: Motor

Function: Turning movements of the head, movements of the shoulder and viscera, voice production

Give the name, type, and function of cranial nerve XII.

Name: Hypoglossal

Type: Motor

Function: Tongue movements

inflammation and enlargement of the parotid glands accompanied by moderate fever, malaise (general discomfort), and extreme pain in the throat, especially when swallowing sour foods or acidic juices

mumps

multi-step procedure in which all traces of pulp tissue are removed from the pulp cavity and root canals of a badly diseased tooth

root canal therapy

the LES fails to close adequately after food has entered the stomach, the stomach contents can reflux (back up) into the inferior portion of the esophagus

gastroesophageal reflux disease

- smooth muscle fibers of the sphincter fail to relax normally, so food does not pass easily from the stomach to the small intestines

- a narrowing of the pyloric sphincter that must be corrected surgically

pylorospasm and pyloric stenosis

forcible expulsion of the contents of the upper GI tract (stomach and sometimes duodenum) through the mouth

vomiting (emesis)

- inflammation of the pancreas, as may occur in association with alcohol abuse or chronic gallstones

- usually affects people over 50 years of age and occurs more frequently in males

pancreatitis and pancreatic cancer

yellowish coloration of the sclerae, skin, and mucous membranes due to a buildup of a yellow compound called bilirubin

jaundice

if bile contains either insufficient bile salts or lecithin or excessive cholesterol, the cholesterol may crystallize to form ________

gallstones

the absorptive cells of the small intestines fail to produce enough lactase, which is essential for the digestion of lactose

lactose intolerance

- because it is lipid-soluble, this* begins to be absorbed in the stomach

- alcohol dehydrogenase, present in gastric mucosa cells, breaks down a lot of the alcohol to acetaldehyde

absorption of alcohol

inflammation of the appendix that is preceded by obstruction of the lumen of the appendix by chyme, inflammation, foreign body, etc.

appendicitis

generally slow-developing benign growths that arise from the mucosa of the large intestine

polyps in the colon

blood that is hidden, not detectable by the human eye

occult blood

consists of indigestible plant carbohydrates found in fruits, vegetables, grains, and beans

dietary fiber

tooth decay, involves a gradual demineralization of the enamel and dentin

dental caries

collective term for a variety of conditions by inflammation and degeneration of the gingivae, alveolar bone, periodontal ligament, and cementum

periodontal disease

- 5-10% of the population develops this*

- ulcers that develop in areas of the GI tract exposed to acidic gastric juice

peptic ulcer disease

sac-like outpouchings of the wall of the colon, occur in places where the muscalaris has weakened and may become inflamed

diverticular disease

among the deadliest of malignancies, ranking 2nd to lung cancer in males and 3rd to breast cancer in women

colorectal cancer

inflammation of the liver that can be caused by viruses, drugs, and chemicals, including alcohol (several types: A, B, C, D, E)

hepatitis

condition caused by malfunction of the myenteric plexus in which the LES fails to relax normally as food approaches

achalasia

a rumbling noise caused by the propulsion of gas through the intestines

borborygmus

painful ulcer on the mucous membrane of the mouth that affects females more often than males, usually between ages 10 and 40

canker sore

distorted or scarred liver as a result of chronic inflammation due to hepatitis, chemicals that destroy hepatocytes, parasites that infect the liver, or alcoholism

cirrhosis

inflammation of the mucosa of the colon and rectum in which absorption of water and salts in reduced

colitis

the visual examination of the lining of the colon using an elongated, flexible, fiber-optic endoscope called a colonoscope

colonoscopy

diversion of feces through an opening in the colon, creating a surgical "stoma" (artificial opening) that is made in the exterior of the abdominal wall

colostomy

difficulty in swallowing that may be caused by inflammation, paralysis, obstruction, or trauma

dysphagia

air in the stomach or intestine, usually expelled through the anus

flatus

a sudden illness caused by ingesting food or drink contaminated by an infectious microbe or a toxin

food poisoning

endoscopic examination of the stomach in which the examiner can view the interior of the stomach directly to evaluate an ulcer, tumor, inflammation, or a source of bleeding

gastroscopy

varicosed (enlarged or inflammed) superior rectal veins, develop when the veins are put under pressure and become engorged with blood

hemorrhoids

protrusion of all or part of an organ through a membrane or cavity wall, usually the abdominal cavity

hernia

inflammation of the gastrointestinal tract that exists in 2 forms: (1) Crohn's disease and (2) Ulcerative colitis

inflammatory bowel disease

disease of the entire GI tract in which a person reacts to stress by developing symptoms associated with alternating patterns of diarrhea and constipation

irritable bowel syndrome (IBS)

a number of disorders in which nutrients from food are not absorbed properly

malocclusion

infectious disease of the GI tract that results in loose, urgent bowel movements, cramping, abdominal pain, malaise, nausea, and occasionally fever and dehydration

Traveler’s diarrhea

chronic disorder characterized by self-induced weight loss, negative perception of body image, and physiological changes that result from nutritional depletion

anorexia nervosa

disorder that typically affects young, single, middle-class white females, characterized by overeating at least twice a week followed by purging by self-induced vomiting

bulimia