Chapter 21: Digestive System

Describe the four layers of tissue that make up the walls of the digestive tract.

The mucosa is the innermost layer (consisting of epithelium, loose connective tissue, and smooth muscle); the submucosa is a layer of connective tissue that contains glands, blood vessels, lymphatic vessels, and nerves; the muscularis has two layers of smooth muscle; and the serosa is the outermost layer.

What are mesenteries?

Mesenteries are layers of visceral peritoneum that suspend the digestive organs within the abdominal cavity; they also contain blood vessels, nerves, lymphatic vessels, and lymph nodes that supply the digestive tract.

Where does the chemical digestion of carbohydrates begin?

mouth

How many permanent teeth are contained in the adult mouth?

32

What digestive enzymes are contained in saliva and what do they digest?

Amylase (breaks down starch) and lipase (begins the digestion of fat)

What structure helps prevent the backflow of stomach acid into the esophagus?

lower esophageal sphincter (LES)

What is the primary function of the stomach?

Store food; also prepares food for digestion by breaking food into small particles and mixing it with gastric juice.

What is the purpose of rugae in the stomach?

As the stomach fills with food, the rugae flatten so the stomach can expand

Why are parietal cells in the stomach important?

The parietal cells secrete hydrochloric acid (which kills microbes in swallowed food) and intrinsic factor (which is necessary for the absorption of vitamin B12).

What are the three phases of gastric secretion?

cephalic phase, gastric phase, intestinal phase

Describe the blood supply to the liver.

The portal vein carries oxygen-poor, nutrient-rich blood from the digestive organs and spleen to the liver; the hepatic artery delivers oxygenated blood from the aorta to the liver.

What is the purpose of the falciform ligament?

It divides the liver into right and left lobes; it also anchors the liver to the abdominal wall

What is the main bile pigment and where does it come from?

The main bile pigment is bilirubin, which results from the breakdown of hemoglobin.

What role does the pancreas play in the digestive process?

It secretes digestive enzymes and an alkaline fluid into the small intestine.

Where does most chemical digestion, and most nutrient absorption occur?

The small intestine

What are proteases and where do they work?

Proteases are enzymes that break the peptide bonds of proteins; they work in the stomach and small intestine.

What makes the digestion of fat unique?

Fat does not dissolve in water, it enters the duodenum as a congealed mass. Before digestion can occur, it must be broken into small droplets.

What is contact digestion?

Contact digestion occurs when chyme slides against the brush border of the epithelial cells in the small intestine. The villi of the cells secrete enzymes that bind with disaccharides to produce glucose.

Stomach enzyme that hydrolyzes peptide bonds

Pepsin

Main fat-digesting enzyme

Lipase

Liver secretion that aids in the digestion and absorption of fat

Bile salts

Semifluid mixture of food particles and gastric juice

Chyme

Salivary enzyme that breaks down starch

Amylase

Hormone that causes gallbladder contractions

Cholecystokinin

Ringlike constrictions in small intestine that break up food particles

Segmentation

Wavelike ripples that move digested material along the gastrointestinal tract

Peristalsis

In which phase of digestion do enzymes break down food into particles cells can absorb?

chemical digestion

The layer of the digestive tract that contracts and relaxes to propel food forward is the:

muscularis

Which mesentery hangs over the small intestine like an apron?

greater omentum (aka greater apron)

Which enzyme acts in the mouth to begin the breakdown of starch?

amylase

The muscular tube that connects the pharynx to the stomach is the:

esophagus

How do triglycerides enter the bloodstream?

They enter the lacteal and travel through the lymphatic system to enter the bloodstream

What is the purpose of rugae?

allow stomach to expand

Which of the following acts as an initial trigger to the stomach to begin secreting gastric juice?

the smell of food

Which pancreatic cells secrete digestive enzymes?

acinar cells

Most nutrients are absorbed in the:

small intestine

Where is most fat digested?

duodenum

A patient with Crohn's disease is most likely to experience which symptom?

diarrhea