Chapter 24: The Digestive System, Study Guide Summer 2026, APII

The peritoneum is divided into two parts. Which part lines the inner surface of the body wall?

The parietal peritoneum.

 The peritoneum is divided into two parts. Which part covers organs that project into the peritoneal cavity?

The visceral peritoneum (serosa).

What fluid separates the visceral peritoneum (serosa) from the parietal peritoneum? What is its Function?

Peritoneal fluid, lubricates the surfaces

What is ascites?

Abdominal swelling caused by the buildup of fluid

What is the structure and function of the mesenteries?

Double sheets of peritoneal membrane that stabilize the positions of the attached organs

Where in the digestive system does adipose tissue deposit to give the characteristic "beer belly".

The greater omentum

What is peritonitis?

Inflammation of the peritoneum

What do circular folds and villi in the small intestines provide?

Increase the surface area available for absorption

Which layer of the digestive tract plays an essential role in mechanical digestion and in moving materials along the digestive tract?

Muscular layer

What is peristalsis?

Contractions of the muscular layer propels materials from one portion of the digestive tract to another

What is a bolus?

Soft rounded ball of digestive contents

What is segmentation?

Cycles of contraction in the intestines that churn and fragment the bolus, mixing the contents with intestinal secretions

What three structures of the oral cavity aid in mechanical digestion?

Tongue, teeth, salivary glands

Why is the lipid-soluble drug nitroglycerin administered orally to treat angina pectoris?

The mucosa inferior to the tongue is is thin and vascular enough to permit rapid absorption

What is the uvula?

A dangling process that helps prevent food from entering the pharynx to soon

What is the lingual frenulum?

A thin fold of mucous membrane that connects the body of the tongue to the mucosa covering the floor of the oral cavity; prevents the tongue from readily being swallowed or blocking the pharynx.

What enzyme is secreted from glands present at the posterior part of the tongue which starts digestion of lipids in the mouth? Why can the enzyme continue to function in the stomach when swallowed?

Lingual lipase; it tolerates an acid environment

What is dentin?

Mineralized matrix that comprises the bulk of the tooth

What is enamel?

A crystalline calcium phosphate that covers the dentin; hardest biologically manufactured substance

List four types of teeth found in the human body.

Incisor, canine, premolar, molar

What are deciduous teeth?

Baby teeth

Which salivary glands produce salivary amylase? What is the function of this enzyme?

Parotid glands; break down starches (complex carbohydrates)

Which two molecules are present in saliva and function to control populations of oral bacteria?

Lysozyme and IgA

What is the main salivary gland that is infected by the mumps virus?

Parotid gland

What is mastication?

chewing

Which part of the digestive system is shared with the respiratory system?

Pharynx

The esophageal mucosa and submucosa are packed into large folds that extend its length. What do the folds allow for?

Expansion during the passage of a large bolus

What is the name of the sphincter that prevents stomach contents from backflowing into the esophagus?

lower esophageal sphincter

What is deglutition?

swallowing

What is chyme?

A mixture of partially digested food

List the four regions of the stomach.

Cardia, fundus, body, pyloric part

What is the name of the largest region of the stomach?

The body

What region of the stomach is located between the body region and the duodenum?

The pyloric part

What is the function of the pyloric sphincter?

Regulates the release of chyme into the duodenum

What is the name and the function of the prominent longitudinal mucosal folds seen in an empty stomach.

Rugae; let the gastric lumen expand

The stomach has extra layers of smooth muscle. One function of this is to strengthen the stomach wall. What is another function?

Assist in the mixing and churning to form chyme

What substance produced by cells in gastric pits protects the stomach from the low pH of stomach acid?

Mucus

Prolonged gastritis can lead to an erosion of the stomach or duodenal lining. What is the resulting condition called?

Peptic ulcer

What two types of gastric cells produce gastric juice?

Parietal cells and chief cells

Which gastric cells produce intrinsic factor? What is the function of intrinsic factor?

Parietal cells; absorb vitamin B12 across the intestinal lining

Parietal cells indirectly produce stomach acid by pumping which two ions into the lumen of the gastric gland?

H+ and Cl-

What inactive proenzyme is produced by chief cells?

Pepsinogen

What converts pepsinogen to pepsin?

Acid in the gastric lumen

What is the function of the enzyme pepsin?

Protein digestion

What cells in gastric pits of the pyloric antrum produce the hormone gastrin?

Enteroendocrine cells

What cells in gastric glands release the hormone somatostatin?

D cells

Which hormone initiates hunger? Which one induces satiety?

Ghrelin; leptin

What are the three phases of digestion?

Cephalic, gastric, intestinal

Which accessory digestive organ has both endocrine (secretion of insulin and glucagon) and exocrine functions?

Pancreas

What is the function of the water and ions primarily secreted by the cells lining the pancreatic ducts?

Dilute and neutralize acid in chyme

Several inactive proenzymes are produced by the pancreas. Why are these inactive proenzymes not released in their active form?

Protects the secretory cells from the destructive effects of their own products

Which digestive accessory organ is the largest visceral organ and is divided into right and left Lobes?

Liver

Which two main blood vessels supply the liver with blood?

Hepatic portal vein and hepatic artery

When discussing the liver, what are lobules?

The basic functional units of the liver

What are stellate phagocytic liver cells called?

Kupffer cells

In what organ would you find the hepatic portal system and bile duct system?

Liver

Which organ produces bile?

Liver

Which organ is primarily responsible for regulating the composition of circulating blood?

Liver

Which organ is mainly involved in the removal and breakdown of circulating drugs?

Liver

In the liver, what is a toxic byproduct of amino acid metabolism? What harmless molecule is it converted to then removed from the body?

Ammonia; urea

What mineral is stored in the liver as a complex called ferritin?

Iron

Which organ stores or removes toxins from the blood?

Liver

Which cells in the liver act as antigen presenting cells?

Stellate macrophages

Where is bile stored?

In the gallbladder

What is the main role of bile salts? Note: Bile salts are lipids. This makes sense because like dissolves like.

Digestion of lipids

What process is used when bile salts break apart lipid droplets?

Emulsification

What is cholecystitis?

Large gallstones that can damage the gallbladder walls or block the cystic/bile ducts

The majority of chemical digestion and nutrient absorption occurs in which part of the small intestine?

Jejunum

What is the function of the lacteal of a villus? (Villus is the singular form of villi) What is the molecule mentioned in the book example that is transported by lacteals?

Transport materials that cannot enter blood capillaries; chylomicrons

In what organ are Paneth cells found? What two molecules are released by Paneth cells?

Small intestine; defensins & lysozyme

Duodenal submucosal glands produce large amounts of mucus when chyme arrives from the stomach. What are two functions of mucus?

Protects the epithelium from the acidity of chyme and contains bicarbonate ions to raise the pH of chyme

Which segment of the small intestine primarily functions to receive chyme from the stomach and neutralize its acids before they can damage the absorptive surfaces of the small intestine?

Duodenum

Partial removal of which segment of the small intestine would be a drastic procedure to promote weight loss? Why?

Jejunum; reduction in absorptive area

Which segment of the small intestine contains Peyer's patches?

Lamina propria

What are brush border enzymes? Where are they found?

Break down material that contact the brush border; on the surfaces of intestinal microvilli in the lumen

Which two reflexes speed up movement of substances along the small intestines?

Gastroenteric & gastroileal reflexes

Name three major parts of the large intestine.

Cecum, colon, rectum

What valve is located between the ileum and cecum?

Ileocecal valve

Which major part of the large intestine is associated with the appendix?

Cecum

Which major part of the large intestine has haustra? What is the function of haustra?

Colon; permit the colon to expand and elongate

List the 4 segments of the colon.

Ascending, transverse, descending, sigmoid

What molecule does the large intestine mainly reabsorb?

Water

What three vitamins are produced by the gut microbiome?

Vitamin K, biotin, vitamin B5

Stimulation of which receptors in the wall of the rectum causes the defecation reflex?

Stretch receptors

List three brush border enzymes and state their overall collective function.

Maltase, sucrose, lactase; break disaccharides and trisaccharides into monosaccharides

Which brush border enzyme is lacking in an individual who is lactose intolerant?

Lactase

What are micelles?

Lipid-bile salt complexes

Which three enzymes produced by the pancreas break peptide bonds in the intestines?

Trypsin, chymotrypsin, elastase

What molecules are made from the action of dipeptidases?

Individual amino acids

All movement of water across the lining of the digestive tract involves which passive process?

Osmotic gradients/osmosis