20  Digestive System

Figure 20.1 The Digestive System.

20.1 Objectives

In these laboratory exercises, you will be studying the structure of the organs of the digestive system via models, diagrams, and histology images.

By the end of this lab, you should:

• Describe the overall function of the digestive system.
• Describe the functions of the individual organs and structures of the digestive system.
• Identify the individual organs of the alimentary canal on a model, in a picture or diagram or in a specimen, and describe the function of each.
• Identify (on a model, in a picture or diagram, or in a microscope slide) and describe the histological structure of the alimentary canal, and the specific components (layers) that comprise it.
  • Mucosa
  • Submucosa
  • Muscularis externa
  • Serosa or adventitia
• Identify the accessory organs of digestion on a model, in a picture or diagram, or in a specimen, and describe the function of each.
• List and identify the histological specializations of the stomach and the small intestine and describe how these specializations contribute to the function of each organ.
• Identify the histological structure of the stomach, small intestine, pancreas, and liver.
• List select digestive enzymes involved in the digestion of proteins, fats, and carbohydrates, and identify their site of origin.

20.2 Digestive System Terms

20.2.1 Alimentary Canal

• Mucosa
  • Epithelium
  • Lamina propria
  • Muscularis mucosa
• Submucosa
• Muscularis externa
  • Circular layer
  • Longitudinal layer
• Serosa/adventitia
• Myenteric plexus
• Villi
• Lacteals
• Capillary loops

20.3 Mouth and Esophagus

• Salivary glands
  • Parotid gland
  • Submandibular gland
  • Sublingual gland
• Oral cavity
• Tongue
• Hard palate
• Soft palate
• Uvula
• Esophagus
• Lower esophageal sphincter

20.4 Teeth

• Incisor (2/quad)
• Canine (cuspid) (1/quad)
• Premolar (bicuspid) (2/quad)
• Molar (3/quad)
• Enamel
• Dentin
• Pulp cavity
• Crown
• Root
• Periodontal ligament
• Gingiva

20.4.1 Stomach

• Cardia
• Cardiac sphincter
• Fundus
• Body
• Greater curvature
• Lesser curvature
• Pylorus
• Rugae
• Pyloric sphincter

20.4.2 Small Intestine

• Duodenum
• Jejunum
• Ileum
• Circular folds
• Villi
• Duodenal papillae

20.5 Large Intestine

• Ileocecal valve
• Ileocecal sphincter
• Cecum
• Appendix
• Ascending colon
• Transverse colon
• Descending colon
• Sigmoid colon
• Rectum
• Anus
• Internal anal sphincter
• External anal sphincter
• Haustra
• Taeniae coli

20.6 Other Structures

• Peritoneum
  • Mesentery
  • Greater omentum
• Pancreas
  • Main pancreatic duct
• Gall bladder
  • Cystic duct
• Liver
  • L./R. hepatic ducts
  • Common hepatic duct
  • Common bile duct
  • Hepatopancreatic ampulla

20.7 Prelab Activities

20.7.1 Prelab Activity 20.1

For this exercise you need to define the following terms using your textbook or another reliable academic resource.

20.7.2 Definitions

• Alimentary Canal __________________________________________
• Muscularis mucosa ______________________________________________
• Submucosa ____________________________________________________
• Muscularis externa ______________________________________________
• Serosa/adventitia _______________________________________________
• Enteric plexus __________________________________________________
• Salivary glands _________________________________________________
  • Parotid gland _____________________________________________
  • Submandibular gland _______________________________________
  • Sublingual gland __________________________________________
• Esophagus ____________________________________________________
• Lower esophageal sphincter _______________________________________
• Stomach ______________________________________________________
  • Cardia __________________________________________________
  • Cardiac sphincter __________________________________________
  • Fundus __________________________________________________
  • Body ____________________________________________________
  • Pylorus __________________________________________________
  • Pyloric sphincter __________________________________________
• Small Intestine _________________________________________________
  • Duodenum _______________________________________________
  • Jejunum _________________________________________________
  • Ileum ___________________________________________________
• Large Intestine ____________________________________________
  • Cecum __________________________________________________
  • Appendix ________________________________________________
  • Ileocecal sphincter _________________________________________
  • Ascending colon __________________________________________
  • Transverse colon __________________________________________
  • Descending colon _________________________________________
  • Sigmoid colon ____________________________________________
  • Rectum _________________________________________________
  • Anus ____________________________________________________
  • Internal anal sphincter ______________________________________
  • External anal sphincter _____________________________________

20.8 Other Structures

• Mesentery _____________________________________________________
• Greater omentum _______________________________________________
• Pancreas _____________________________________________________
• Liver _________________________________________________________
• Gall bladder ___________________________________________________

20.9 Prelab Activity 20.2

Identify and label the four major layers of the alimentary canal.

Figure 20.2 Layers of the Digestive Tract.

20.10 Prelab Activity 20.3

Identify and label the anatomical features of the mouth, pharynx, and larynx.

Complete Table 20.1 with the name of the structure, region, feature, or organ that corresponds to each label on the diagram below.

Figure 20.3 Human Vocal Organs in the Oral/Nasal Cavities and Trachea.

Table 20.1 Features of the Digestive System (Midsagittal Head)

1	8
2	9
3	10
4	11
5	12
6	13
7

20.11 Prelab Activity 20.4

Identify the components of the alimentary canal.

Fill in Table 20.2 with the name of the structure, region, or organ that corresponds to each label on the diagram below of the digestive tract.

Figure 20.4 The Digestive Tract.

Table 20.2 Organs within the Digestive Tract

1.	2.
3.	4.
5.	6.
7.

20.12 Prelab Activity 20.5

Identifying anatomical structures of the stomach.

Fill in the table below with the name of the digestive system structure, region, feature, or organ that corresponds to each label on the model.

20.13 Anatomy of the Stomach

Table 20.3 Identification of the Anatomy of the Stomach

Structure Label	Name
1
2
3
4
5
6
7
8
9
D
E

20.14 Prelab Activity 20.6

Identifying anatomical features of the gastrointestinal tract.

Fill in the table below with the name of the digestive system structure, region, feature, or organ that corresponds to each label on the model at the left.

Figure 20.6 Alimentary Canal.

Table 20.4 Identification of the Components of the Digestive Tract

Letter	Name
1
2
3
4
5
6
7
8
9

20.15 Prelab Activity 20.7

Functions of the organs of the gastrointestinal tract (alimentary canal). Fill in the table with their functions in the alimentary canal / digestive system organs.

Table 20.5 Functions of Select Organs in the Digestive Tract

Structure	Function
Mouth
Esophagus
Stomach
Small Intestine
Large Intestine
Liver
Gall Bladder

20.16 Prelab Activity 20.8:

Identify the following components of the digestive system.

Figure 20.7 Biliary System.

Table 20.6 Structures within the Biliary System

Structure Number	Structure Name
3
4
5
6
9
10
12
14
15
18
19
20

20.16.1 Prelab Activity 20.9.

Identify and label the structures of the large intestine.

Figure 20.8 The Large Intestine.

Figure 20.9 Cross Section of a Tooth.

20.17 Prelab Activity 20.10

Identify the structures of the tooth in the diagram above.

Table 20.7 Structures of the tooth

Structure Number	Structure Name
1
2
3
4
5
6
7
8
9

Figure 20.10 Adult Teeth.

20.17.1 Prelab Activity 20.11.

Identify and label the teeth found in the adult mouth. Circle and identify the different sets of teeth.

20.18 Lab Activities

20.19 Organs and systems

20.20 Alimentary Canal Terms

• Mucosa
  • Epithelium
  • Lamina propria
  • Muscularis mucosa
• Submucosa
• Muscularis externa
  • Circular layer
  • Longitudinal layer
• Serosa/adventitia
• Enteric plexus
• Villi
• Lacteals
• Capillary loops

20.21 Lab Activity 20.1

• Gather into your assigned study groups and obtain the 3D microanatomy digestive system and intestinal villi models from the storage area in the laboratory.
• Identify and label structures on the model from the list above. You may have to use your text to assist with these identifications.
• Take pictures of your finished work for your review later. Also palpate the models to enable you to learn the layers and their names more quickly.

Figure 20.12 Layers of the Gastrointestinal Tract.

20.22 Mouth and Esophagus Terms

• Oral cavity

• Tongue

• Hard palate

• Soft palate

• Uvula

• Esophagus

• Lower esophageal sphincter

• Salivary glands

  • Parotid gland
  • Submandibular gland
  • Sublingual gland

20.23 Lab Activity 20.2

• Obtain a 3D medial head section, a human head as well as a human digestive model from the storage area in the laboratory.
• Identify and label structures on the model from the list above. You may have to use your text to assist with these identifications.
• Locate and label the structures listed above on the models.

Figure 20.13 The Structures of the Mouth.

Figure 20.14 Anatomy of the Mouth and Esophagus.

20.23.1 The Salivary Glands

Figure 20.15 The Salivary Glands.

20.24 Lab Activity 20.3

• Form into your assigned study groups and obtain a 3D model of the teeth from the storage area in the laboratory.
• Identify and label the types of teeth on the model from the list below. You should be able to identify each tooth type from an individual specimen in the upcoming practical.
• Locate and label the structures of an individual tooth as noted in figure 20.17. Be able to identify the structures based on either a 3D model or a diagram.

20.25 Tooth Types

• Incisor (2/quad)

• Canine (cuspid) (1/quad)

• Premolar (bicuspid) (2/quad)

• Molar (3/quad)

Figure 20.16 Types, or Sets, of Teeth.

20.26 Tooth Anatomy

• Enamel

• Dentin

• Pulp cavity

• Crown

• Root

• Periodontal ligament

• Gingiva

Figure 20.17 Diagram of a Molar

20.27 Digestive Organs

20.28 Lab Activity 20.4

• Obtain a human digestive model and a from the storage area in the laboratory.
• Identify and label structures on the stomach on the model using the list below. You may have to use your text to assist with these identifications.
• Locate and label the structures listed below on the model.

20.28.1 Stomach Structures

• Cardia

• Cardiac sphincter

• Fundus

• Body

• Greater curvature

• Lesser curvature

• Pylorus

• Rugae

• Pyloric sphincter

20.18 Anatomy of the Stomach.

Figure 20.19 The Layers of the Stomach.

20.29 Small Intestine Anatomy

20.29.1 Terms

• Duodenum

• Jejunum

• Ileum

• Circular folds

• Villi

• Duodenal papillae

Figure 20.20 The Small Intestine Anatomy

20.30 Lab Activity 20.5

Obtain a model of the digestive system and the intestinal villi from the storage area.

• Using the human digestive model and the intestinal villi models, identify and label the sections of the small intestine and structures of a villus on the model(s) using the list below. You may have to use your text along with figures 20.20 to 20.21 to assist with these identifications.
• Locate and label the structures listed below on the model.

Photograph your work for later reference.

Figure 20.21 The Small Intestine Villi Histology.

Figure 20.22 The Duodenal Papilla of the Pancreas.

20.30.1 Large Intestine:

20.31 Large Intestine Anatomy

20.31.1 Terms

• Cecum
• Appendix
• Ileocecal valve
• Ileocecal sphincter
• Ascending colon
• Transverse colon
• Descending colon
• Sigmoid colon
• Rectum
• Anus
• Internal anal sphincter
• External anal sphincter
• Haustra
• Taeniae coli

Figure 20.23 The large Intestine.

20.31.2 Lab Activity 20.6

Using the human digestive model, identify and label the sections of the small intestine and structures of a villus on the model(s) using the list below. You may have to use your text along with figures 20.23 and 20.24 to assist with these identifications.

• Locate and label the structures listed below on the model.
• Photograph your work for later reference.

Figure 20.24 Large Intestine Internal and External Sphincters.

20.32 Accessory Organs:

20.32.1 Terms

• Liver
  • L./R. hepatic ducts
  • Common hepatic duct
  • Common bile duct
  • Hepatopancreatic ampulla (Duodenal papilla)
• Gall bladder
  • Cystic duct
• Pancreas
  • Main pancreatic duct
• Mesentery
• Greater omentum

20.33 Lab Activity 20.7

• Using the human digestive model you acquired from the storage area, identify, and label the accessory structures using the list below. You may have to use your text along with figures 20.25 to 20.28 to assist with these identifications.
• Locate and label the structures listed below on the model. Remember to palpate the model to help reinforce the information in your memory.
• Photograph your work for later reference.

20.34 Accessory Structures

Figure 20.25 Accessory Digestive Organs.

20.35 Mesentery

Figure 20.26 The Structure of Mesentery Spread Across the Intestines.

20.36 Greater Omentum

Figure 20.27 Organs of the Thorax and Abdominal Regions. Key: Greater omentum - 7

20.36.1 Pancreas:

Figure 20.28 The Pancreas.

20.37 Supporting internet videos

20.38 Digestive system introduction

• Digestive System Plaque. Dr. Lotz. https://youtu.be/8OI1QrYI4HU?si=g8qilk4DFacMKieK.
• Professor Long 2402 Lab Digestive Tract Anatomy. Professor Bob Long Human Anatomy and Physiology. https://youtu.be/zLpqVkxTM5w?si=lnwCA1w6oocJUEAo.

20.39 Review Video

• Digestive Tract Anatomy | Review and Practice. Anatomy Hero. https://youtu.be/OJyfuXVOs4g?si=xhWD3ch6SiUZTVKx. Note: MISTAKE: Early in the video the presenter said “pharyngeal tonsil” when she should have said palatine

20.40 How the Body Works

20.41 The Architecture of the Liver

• Daniel Izzo, You Tube.https://youtu.be/Gn-ibhGE7PI

20.42 The Small Intestine

• Small Intestine & Nutrient Absorption. Anatomy and Physiology for Paramedics. https://youtu.be/dmjypoW-USE?si=GPYVevvSZQVre3PO.
• Small Intestine Anatomy (Parts, Topography, Structures, Layers). Taim Talks Med. https://youtu.be/j0XVr2Tla-c?si=KvK\_BGBnOY1rdHmq.
• Small Intestine(anatomy). Sam Webster). https://youtu.be/ClOTBwFNnQ?si=PbjxloCXd0JiCms7.

20.42.1 The Large Intestine:

• The large intestine (anatomy): Sam Webster. https://youtu.be/lWw8iOkGe9g?si=gf7GikG2Q\_vGoRLQ.

20.43 Post Lab Activities

20.44 Check Your Understanding

20.45 Post Lab Activity 20.1

20.45.1 Identifications

Identify the structures found in figures 20.29 to 20.32.

Figure 20.29 Cross Section of the Small Intestine.

Table 20.8 Structures and Layers of the Smal Intestine

Number(s)
1-3 collectively
1
2
3
8
12-13 collectively
12
14-15 collectively
16

Figure 20.30 The Anatomy of the Large Intestine.

Table 20.9 Identification of the Structures in the Large Intestine

Number	Intestinal identification
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15

Figure 20.31 The Digestive System.

Table 20.10. Word Bank for Figure 20.31

Word Bank
Salivary glands	Sublingual gland	Parotid gland	Submandibular gland
	Oral cavity	Tongue	Hard palate
Soft palate	Uvula	Esophagus	Lower esophageal
			sphincter
Teeth	Incisor	Canine	Premolar
Molar	Gingiva	Enamel	Dentin
Pulp cavity	Crown	Root	Periodontal ligament
Stomach	Cardiac sphincter	Fundus	Cardia
Body	Greater curvature	Lesser curvature	Pylorus
Rugae	Pyloric sphincter	Ileum	Jejunum
Small Intestine	Duodenum	Duodenal papillae	Circular folds
Villi	Ileocecal sphincter	Cecum	Haustra
Large Intestine	Ileocecal valve	Ascending colon	Transverse colon
Descending colon	Appendix	Rectum	Anus
Internal anal sphincter	Sigmoid colon	Taeniae coli	External anal sphincter

Identify and describe the function of the structures in figure 20.32.

Figure 20.32 The Digestive System, Unlabeled.

20.46 Post Lab Activity 20.2

20.46.1 Review Questions

Answer the following questions:

1. Which of these organs is not considered an accessory digestive structure?
   1. mouth
   2. salivary glands
   3. pancreas
   4. liver
2. Which of the following membranes covers the stomach?
   1. falciform ligament
   2. mesocolon
   3. parietal peritoneum
   4. visceral peritoneum
3. Which of these is most associated with villi?
   1. haustra
   2. lacteals
   3. bacterial flora
   4. intestinal glands
4. In which part of the alimentary canal does most digestion occur?
   1. stomach
   2. small intestine
   3. ascending colon
5. Which part of the large intestine attaches to the appendix?
   1. cecum
   2. ascending colon
   3. transverse colon
   4. descending colon
6. Which of these is most associated with villi?
   1. haustra
   2. lacteals
   3. bacterial flora
   4. intestinal glands
7. Where does the chemical digestion of starch begin?
   1. mouth
   2. esophagus
   3. stomach
   4. small intestine
8. Where are most of the fat-digesting enzymes produced?
   1. small intestine
   2. gallbladder
   3. liver
   4. pancreas
9. During a hockey game, the puck hits a player in the mouth, knocking out all eight of his most anterior teeth. Which teeth did the player lose and how does this loss affect food ingestion?

20.46.2 Post Lab Activity 20.3

20.46.3 Crossword Puzzles

Complete the following crossword puzzles.

Figure 20.33 Digestive System-1

20.46.4 Across

• 4 The organs of the digestive system which are found in the abdominal cavity, and the cavity itself, are lined by a(n) ____ membrane, the ____. (6,10)

• 5 The most visible mesentary, upon dissection, is the folded layer wich hangs like a curtin from the stomach and transverse colon; it is called the ____ ____. (7,7)

• 6 The ____ is the “dangily” part of the soft palate; together with the sft palate it prevents ___ from entering the nose as one swalows. (5,4)

• 9 the gastrointstinal tract is sometimes called the ____ ____. (10,5)

• 10 The ____ holds abdominal organs in place and prevents them from shifting within the abdominal cavity. In addition , fat accumulates within its folds. (9)

20.46.5 Down

• 1 The roof of the oral cavit is divided into two parts, the bony ____ ____ and the ____ ____. (4,6,4,6)

• 2 The ____ are double layered extensions of the peritoneum which connect the abdominal organs to the abdominal walls. Collectively these extensions are called the _____ (11,9)

• 3 The peritoneal cavity is located between the visceral and parietal layers of the peritoneum and is filled with ____ ____ (6,5)

• 7 The central are aof the gastrointestinal tract is called the ____. (5)

• 8 The posterior part of the mouth leads into the ____. (7)

Figure 20.34 Digestive, Alimentary Canal

20.46.6 Across

• 4 The gastrointestinal tract is sometimes called the ____ ____. (10,5)
• 5 The posterior part of the mouth leads into the ____. (7)
• 6 The ____ holds abdominal organs in place and prevents them from shifting within the abdominal cavity. In addition, fat accumulates within its folds. (9)
• 9 The organs of the digestive system which are found in the abdominal cavity, and the cavity itself, are lined by a(n) ____ membrane, the ____. (6,10)
• 10 The most visible mesentery, upon dissection, is the folded layer which hangs like a curtain from the stomach and transverse colon; it is called the ____ ____. (7,7)

20.46.7 Down

• 1 The ____ is the “dangly” part of the soft palate; together with the soft palate it prevents ___ from entering the nose as one swallows. (5,4)
• 2 The ____ are double layered extensions of the peritoneum which connect the abdominal organs to the abdominal walls. Collectively these extensions are called the _____ (11,11)
• 3 The roof of the oral cavity is divided into two parts, the bony ____ ____ and the ____ ____. (4,6,4,6)
• 7 The central cavity of the gastrointestinal tract is called the ___. (5)
• 8 The peritoneal cavity is located between the visceral and parietal layers of the peritoneum and is filled with ____ ____ (6,5)

Figure 20.35 Digestive - Stomach

20.46.8 Across

• 4 The upper opening of the stomach is the ___ or ___ opening. (16,7)

• 5 The lower region of the stomach is called the ____. (7)

• 6 The lower esophageal sphincter is also known as the __ ___. (7,9)

• 7 The part of the stomach that is superior to the cardiac sphincter is the ____. (6)

20.46.9 Down

• 1 The esophagus connects the ___ to the ___ and has a(n) ___ at each end to control the entry and exit of food and drink. (7,7,9)

• 2 The esophagus is a tube lying anterior to the ___ and posterior to the ____ and the ____. (9,6,7)

• 3 The interior of the empty stomach is wrinkled; these wrinkles of folds are called ____. (5)

Figure 20.36 Digestive; Intestines and Accessory organs

20.46.10 Across

• 4 The pancreas is a long, roughly triangular organ nested in the curve of the ___, lying posterior to the ____. (8,7)

• 6 The pancreas is essentially two glands in one: It has both ___ and ___ functions (9,0,8)

• 9 The small intestine is divided anatomically into three regions. Listed in order as food moves they are the ___, ___ and ___. (8,7,5)

• 12 Dilute bile is produced by the liver and transferred to the ____. (11)

• 13 The ___ are pancreatic cell clusters which secrete digestive enzymes. (5)

• 14 The anal canal is a passageway which conducts feces out of the rectum. It includes two ____; the inner one is involuntary, the outer is voluntary. (10)

20.46.11 Down

• 1 The large intestine is divided into five regions. Approximately one half of the ___ is found on the left side of the body; from there feces reach the ___ their final storage place prior to their exit through the ____ ____. (5,6,4,5)

• 2 The 25 cm ____ is the C-shaped portion of the small intestine into which the stomach empties. (8)

• 3 The tenia are ribbons of ___ ___ running along the length of the large intestine. They cause the formation of puckered pouches called ___ along the entire length of the large intestine. (6,6,7)

• 5 The ___ ___ is a vestigial organ roughly the size of one’s index finger, suspended from the cecum. (9,8)

• 7 Entry of chyme into the large intestine is controlled by the ___ ___ which is found at the juncture of the ileum and the large intestine. (9,5)

• 8 The longest and terminal portion of the small intestine. (5)

• 10 The great length of the small intestine is necessary for ___ ___. (8,10)

• 11 The second longest portion of the small intestine is the ____. This section is located in the middle of the small intestine. (7)

Figure 20.37 Digestive - Teeth

20.46.12 Across

• 7 The boundary between the tooth crown and the root is the ______ (4)
• 8 The outer layer of a tooths root is the ____ (6)
• 10 The part of the tooth below the gums (4)
• 12 Teeth are held in their sockets by ____ ____ (10,9)
• 13 ____ are teeth which tear (7)
• 14 ____ and ____ are teeth which grind (9,6)

20.46.13 Down

• 1 The ____ salivary glands are located beneath the tongue (10)

• 2 How many pairs of salivary glands are found in the mouth? (5)

• 3 The socket in the jaw which holds a tooth is called a(n) ____. (9)

• 4 The submandibular glands are salivary glands located ___ to each side of the mandible. (12)

• 5 The parotid glands are located ___ to the masseter muscle. (13)

• 6 The crown of the tooth is composed of a core of living tissue called ____ surrounded by a layer of nonliving ____ (6,6)

• 9 The part of the tooth above the gums (5)

• 11 ____ are teeth which cut (8)

20.47 Keys to the Crosswords:

20.48 Figure 20.31 Digestive System-1

• Across: 4 serous membrane, 5 greater omentum, 6 uvula, food, 9 alimentary canal, 10 mesentary
• Down: 1 hard palate, soft palate, 2 mesentaries, mesentary, 3 serous fluid, 7 lumen, 8 trachea

20.49 Figure 20.32 Digestive; alimentary canal

• Across: 4 Serous periteonum, 5 Greater omentum, 6 Uvula food, 9 Alimentary canal, 10 Mesentary.
• Down: 1 Hard palate soft palate, 2 Mesentaries mesentary, 3 Serous fluid, 7 Lumen, 8 Pharynx.

20.49.1 Figure 20.33 Digestive; stomach

• Across: 4 Cardiac sphincter, 6 Pylorus, 7 Vertebrae larynx trachea.
• Down: 1 Pharynx stomach sohincter, 2 Gastroesophegeal cardiac, 3 Fundus, 5 Rugae.

20.50 Figure 20.34 Digestive; Intestines and accessory organs

• Across: 4 Duodenum stomach, 6 Endocrine exocrine, 9 Duodenum jejunum ileum, 12 Gallbladder, 13 Acini, 14 Sphincters.
• Down: 1 Colon rectum anal canal, 2 Duodenum, 3 Smooth muscle haustra, 5 Vermiform appendix, 7 Ileocecal valve, 8 Ileum, 10 Nutrient absorption, 11 Jejunum.

20.50.1 Figure 20.35 Digestive - Teeth

• Across: 7 Neck, 8 Dentin, 10 Root, 12 Peridontalligamentts, 13 Canines, 14 Premolars molars.
• Down: 1 Sublingual, 2 Three, 3 Gomphosit, 4 Inferomedial, 5 Posteroateral, 6 Dentin enamel, 9 Crown, 11 Incisors.

20.50.2 Chapter 20: Digestive System Glossary

Terms	Definitions
absorption	passage of digested products from the intestinal lumen through mucosal cells and into the bloodstream or lacteals
accessory digestive organ	includes teeth, tongue, salivary glands, gallbladder, liver, and pancreas
accessory duct (also, duct of Santorini)	duct that runs from the pancreas into the duodenum
acinus	cluster of glandular epithelial cells in the pancreas that secretes pancreatic juice in the pancreas
alimentary canal	continuous muscular digestive tube that extends from the mouth to the anus
aminopeptidase	brush border enzyme that acts on proteins
anal canal	final segment of the large intestine
anal column long fold of mucosa in the anal canal	anal column long fold of mucosa in the anal canal
anal sinus	recess between anal columns
appendix (vermiform appendix)	coiled tube attached to the cecum
ascending colon	first region of the colon
bacterial flora	bacteria in the large intestine
bile	alkaline solution produced by the liver and important for the emulsification of lipids
bile canaliculus	small duct between hepatocytes that collects bile
bilirubin	main bile pigment, which is responsible for the brown color of feces
body	mid-portion of the stomach
bolus	mass of chewed food
brush border	fuzzy appearance of the small intestinal mucosa created by microvilli
cardia (also, cardiac region)	cardia (also, cardiac region the cardiac orifice (esophageal hiatus)
Cardiac sphincter	surrounds the lower part of the esophagus at the junction between the esophagus and the stomach.
cecum	pouch forming the beginning of the large intestine
cementum	bone-like tissue covering the root of a tooth
central vein	vein that receives blood from hepatic sinusoids
cephalic phase (also, reflex phase)	initial phase of gastric secretion that occurs before food enters the stomach
chemical digestion	enzymatic breakdown of food
chief cell	gastric gland cell that secretes pepsinogen
chylomicron	large lipid-transport compound made up of triglycerides, phospholipids, cholesterol, and proteins
chyme	soupy liquid created when food is mixed with digestive juices
circular fold (also, plica circulare)	deep fold in the mucosa and submucosa of the small intestine
colon	part of the large intestine between the cecum and the rectum
common bile duct	structure formed by the union of the common hepatic duct and the gallbladder’s cystic duct
common hepatic duct	duct formed by the merger of the two hepatic ducts
crown	portion of tooth visible superior to the gum line
cuspid (also, canine)	pointed tooth used for tearing and shredding food
cystic duct	duct through which bile drains and enters the gallbladder
deciduous tooth	one of 20 ‘baby teeth’
defecation	elimination of undigested substances from the body in the form of feces
deglutition	three-stage process of swallowing
dens tooth	dens tooth
dentin	bone-like tissue immediately deep to the enamel of the crown or cementum of the root of a tooth
dentition	set of teeth
deoxyribonuclease	pancreatic enzyme that digests DNA
descending colon	part of the colon between the transverse colon and the sigmoid colon
dipeptidase	brush border enzyme that acts on proteins
duodenal gland (also, Brunner’s gland)	Mucous secreting gland in the duodenal submucosa
duodenum	first part of the small intestine, which starts at the pyloric sphincter and ends at the jejunum
enamel	covering of the dentin of the crown of a tooth
enteroendocrine cell	gastric gland cell that releases hormones
enterohepatic circulation	recycling mechanism that conserves bile salts
enteropeptidase	intestinal brush-border enzyme that activates trypsinogen to trypsin
epiploic appendage	small sac of fat-filled visceral peritoneum attached to teniae coli
esophagus	muscular tube that runs from the pharynx to the stomach
external anal sphincter	voluntary skeletal muscle sphincter in the anal canal
fauces	opening between the oral cavity and the oropharynx
feces	semisolid waste product of digestion
flatus	gas in the intestine
fundus	dome-shaped region of the stomach above and to the left of the cardia
G cell	gastrin-secreting enteroendocrine cell
gallbladder	accessory digestive organ that stores and concentrates bile
gastric emptying	process by which mixing waves gradually cause the release of chyme into the duodenum
gastric gland	gland in the stomach mucosal epithelium that produces gastric juice
gastric phase	phase of gastric secretion that begins when food enters the stomach
gastric pit	narrow channel formed by the epithelial lining of the stomach mucosa
gastrin	peptide hormone that stimulates secretion of hydrochloric acid and gut motility
gastrocolic reflex	propulsive movement in the colon activated by the presence of food in the stomach
gastroileal reflex	long reflex that increases the strength of segmentation in the ileum
gingiva	gum
Greater curvature	long, convex, lateral surface of the stomach
Greater omentum	a large apron-like fold of visceral peritoneum that hangs down from the stomach.
haustral contraction	slow segmentation in the large intestine
haustrum	small pouch in the colon created by tonic contractions of teniae coli
hepatic artery	artery that supplies oxygenated blood to the liver
hepatic lobule	hexagonal-shaped structure composed of hepatocytes that radiate outward from a central vein
hepatic portal vein	vein that supplies deoxygenated nutrient-rich blood to the liver
hepatic sinusoid	blood capillaries between rows of hepatocytes that receive blood from the hepatic portal vein and the branches of the hepatic artery
hepatic vein	vein that drains into the inferior vena cava
hepatocytes	major functional cells of the liver
hepatopancreatic ampulla (also, ampulla of Vater)	bulb-like point in the wall of the duodenum where the bile duct and main pancreatic duct unite
hepatopancreatic sphincter (also, sphincter of Oddi)	sphincter regulating the flow of bile and pancreatic juice into the duodenum
hydrochloric acid (HCl)	digestive acid secreted by parietal cells in the stomach
ileocecal sphincter	sphincter located where the small intestine joins with the large intestine
ileum	end of the small intestine between the jejunum and the large intestine
incisor	midline, chisel-shaped tooth used for cutting into food
ingestion	taking food into the GI tract through the mouth
internal anal sphincter	involuntary smooth muscle sphincter in the anal canal
intestinal gland (also, crypt of Lieberkuhn)	gland in the small intestinal mucosa that secretes intestinal juice
intestinal juice	mixture of water and mucus that helps absorb nutrients from chyme
intestinal phase	phase of gastric secretion that begins when chyme enters the intestine
intrinsic factor	glycoprotein required for vitamin B12 absorption in the small intestine
jejunum	middle part of the small intestine between the duodenum and the ileum
labial frenulum	midline mucous membrane fold that attaches the inner surface of the lips to the gums
labium	lip
lactase	brush border enzyme that breaks down lactose into glucose and galactose
lacteal	lymphatic capillary in the villi large intestine terminal portion of the alimentary canal
laryngopharynx	part of the pharynx that functions in respiration and digestion
left colic flexure (also, splenic flexure)	point where the transverse colon curves below the inferior end of the spleen
Lesser curvature	the shorter, concave, medial surface of the stomach,
lingual frenulum	mucous membrane fold that attaches the bottom of the tongue to the floor of the mouth
lingual lipase	digestive enzyme from glands in the tongue that acts on triglycerides
lipoprotein lipase	enzyme that breaks down triglycerides in chylomicrons into fatty acids and monoglycerides
liver	largest gland in the body whose main digestive function is the production of bile
lower esophageal sphincter	smooth muscle sphincter that regulates food movement from the esophagus to the stomach
main pancreatic duct (also, duct of Wirsung)	duct through which pancreatic juice drains from the pancreas
major duodenal papilla	point at which the hepatopancreatic ampulla opens into the duodenum
maltase	brush border enzyme that breaks down maltose and maltotriose into two and three molecules of glucose, respectively
mass movement	long, slow, peristaltic wave in the large intestine
mastication	chewing
mechanical digestion	chewing, mixing, and segmentation that prepares food for chemical digestion
mesentery	an organ that attaches the intestines to the posterior abdominal wall, consisting of a double fold of the peritoneum.
mesoappendix	mesentery of the appendix
micelle	tiny lipid-transport compound composed of bile salts and phospholipids with a fatty acid and monoacylglyceride core
microvillus	small projection of the plasma membrane of the absorptive cells of the small intestinal mucosa
migrating motility	complex form of peristalsis in the small intestine
mixing wave	unique type of peristalsis that occurs in the stomach
molar	tooth used for crushing and grinding food
motilin	hormone that initiates migrating motility complexes
motility	movement of food through the GI tract
mucosa	innermost lining of the alimentary canal
mucosal barrier	protective barrier that prevents gastric juice from destroying the stomach itself
mucous neck cell	gastric gland cell that secretes a uniquely acidic mucus
muscularis	muscle (skeletal or smooth) layer of the alimentary canal wall
myenteric plexus (plexus of Auerbach)	major nerve supply to alimentary canal wall; controls motility
nucleosidase	brush border enzyme that digests nucleotides
oral cavity (also, buccal cavity)	mouth
oral vestibule	part of the mouth bounded externally by the cheeks and lips, and internally by the gums and teeth
oropharynx	part of the pharynx continuous with the oral cavity that functions in respiration and digestion
palatoglossal arch	muscular fold that extends from the lateral side of the soft palate to the base of the tongue
palatopharyngeal arch	muscular fold that extends from the lateral side of the soft palate to the side of the pharynx
pancreas	accessory digestive organ that secretes pancreatic juice
pancreatic amylase	enzyme secreted by the pancreas that completes the chemical digestion of carbohydrates in the small intestine
pancreatic juice	secretion of the pancreas containing digestive enzymes and bicarbonate
pancreatic lipase	enzyme secreted by the pancreas that participates in lipid digestion
pancreatic nuclease	enzyme secreted by the pancreas that participates in nucleic acid digestion
parietal cell	gastric gland cell that secretes hydrochloric acid and intrinsic factor
parotid gland	one of a pair of major salivary glands located inferior and anterior to the ears
pectinate line	horizontal line that runs like a ring, perpendicular to the inferior margins of the anal sinuses
pepsinogen	inactive form of pepsin
Periodontal ligament	the fibrous connective tissue found between the roots of the teeth and the inner wall of the bone socket.
peristalsis	muscular contractions and relaxations that propel food through the GI tract
permanent tooth	one of 32 adult teeth
pharynx	throat
phosphatase	brush border enzyme that digests nucleotides
porta hepatis	‘gateway to the liver’ where the hepatic artery and hepatic portal vein enter the liver
portal triad	bile duct, hepatic artery branch, and hepatic portal vein branch
premolar (also, bicuspid)	transitional tooth used for mastication, crushing, and grinding food
propulsion	voluntary process of swallowing and the involuntary process of peristalsis that moves food through the digestive tract
pulp cavity	deepest portion of a tooth, containing nerve endings and blood vessels
pyloric antrum	wider, more superior part of the pylorus
pyloric canal	narrow, more inferior part of the pylorus
pyloric sphincter	sphincter that controls stomach emptying
pylorus	lower, funnel-shaped part of the stomach that is continuous with the duodenum
rectal valve	one of three transverse folds in the rectum where feces is separated from flatus
rectum	part of the large intestine between the sigmoid colon and anal canal
reticuloendothelial cell (also, Kupffer cell)	phagocyte in hepatic sinusoids that filters out material from venous blood from the alimentary canal
retroperitoneal	located posterior to the peritoneum
ribonuclease	pancreatic enzyme that digests RNA
right colic flexure (also, hepatic flexure)	point, at the inferior surface of the liver, where the ascending colon turns abruptly to the left
root	portion of a tooth embedded in the alveolar processes beneath the gum line
ruga (plural: rugae)	fold of alimentary canal mucosa and submucosa in the empty stomach and other organs
saccharolytic fermentation	anaerobic decomposition of carbohydrates
saliva	aqueous solution of proteins and ions secreted into the mouth by the salivary glands
salivary amylase	digestive enzyme in saliva that acts on starch
salivary gland	an exocrine gland that secretes a digestive fluid called saliva
salivation	secretion of saliva
segmentation	alternating contractions and relaxations of non-adjacent segments of the intestine that move food forward and backward, breaking it apart and mixing it with digestive juices
serosa	outermost layer of the alimentary canal wall present in regions within the abdominal cavity
sigmoid colon	end portion of the colon, which terminates at the rectum
small intestine	section of the alimentary canal where most digestion and absorption occurs
soft palate	posterior region of the bottom portion of the nasal cavity that consists of skeletal muscle
stomach	alimentary canal organ that contributes to chemical and mechanical digestion of food from the esophagus before releasing it, as chyme, to the small intestine
sublingual gland	one of a pair of major salivary glands located beneath the tongue
submandibular gland	one of a pair of major salivary glands located in the floor of the mouth
submucosa	layer of dense connective tissue in the alimentary canal wall that binds the overlying mucosa to the underlying muscularis
submucosal plexus (plexus of Meissner)	nerve supply that regulates activity of glands and smooth muscle
sucrase	brush border enzyme that breaks down sucrose into glucose and fructose
tenia coli	one of three smooth muscle bands that make up the longitudinal muscle layer of the muscularis in all of the large intestine except the
terminal	end
tongue	accessory digestive organ of the mouth, the bulk of which is composed of skeletal muscle
transverse colon	part of the colon between the ascending colon and the descending colon
upper esophageal sphincter	skeletal muscle sphincter that regulates food movement from the pharynx to the esophagus
Valsalva’s maneuver	voluntary contraction of the diaphragm and abdominal wall muscles and closing of the glottis, which increases intra-abdominal pressure and facilitates defecation
villus	projection of the mucosa of the small intestine
voluntary phase	initial phase of deglutition, in which the bolus moves from the mouth to the oropharynx
α-dextrin	breakdown product of starch
α-dextrinase	brush border enzyme that acts on α- dextrins