Chapter 23; Digestive System A&P

List, describe and label what is included in each layer of the digestive system (histology).

"Mucosa is the innermost layer of tissue. The mucosa has three major functions: 1. Secrete mucus, digestive enzymes, and hormones 2. Absorb the end products of digestion into the blood 3. Protect against infectious disease Digestive mucosa is made up of three sublayers: (1) a lining epithelium, (2) a lamina propria, and (3) a musclularis mucosae. Except in the mouth, esophagus, and anus where it's stratified squamous, the epithelium of mucosa is a simple columnar epithelium rich in mucus-secreting cells. The submucosa, just external to the mucosa, is areolar connective tissue containing a rich supply of blood and lymphatic vessels, lymphoid follicles, and nerve fibers which supply the surrounding tissues of the GI tract wall. Its elastic fibers enable the stomach to regain its normal shape after temporarily storing a large meal." Dense connective tissue, blood vessels, lymphatic vessels, glands, and nerves. "The muscularis externa, (also called the muscularis) surrounds the submucosa. The muscularis is responsible for segmentation and peristalsis. It typically has an inner circular layer and an outer longitudal layer of smooth muscle cells. In several places along the tract, the circular layer thickens and forms sphincters that act as valves that control food passage from one organ to the next, they also prevent back flow." Double layer of smooth muscle: circular layer and longitudinal layer and mechanical digestion. Located in the mouth, pharynx, anterior portion of the esophagus, external anal sphincter: composed of skeletal muscle for voluntary control. "The serosa is the outermost layer of the intraperitoneal organs. In most alimentary canal organs, its made up of areolar connective tissue covered with mesothelium, a single layer of squamous epithelial cells." In the mouth, pharynx, and esophagus the series is not present. Instead collagen fibers called adventitia are present. Holds the alimentary canal in place.

Be able to list the path of blood through the hepatic portal system.

1. Delivers deoxygenated blood containing nutrients from the small intestines. - Also, drugs, tons, are sent to the liver - All blood from the alimentary canal will pass through the liver 2. Once the blood has been filtered through the liver: -Drain into the central vein - Then processed to the interlobular vein - Then to the hepatic vein - Finally joining the inferior vena cava to go back to the heart

Describe the function of the accessory organs to the digestive system.

1. Liver: produces bile salts, which emulsify lipids, aiding their digestion and absorption. 2. Gallbladder: stores, concentrates, and releases bile. 3. Pancreas: produces digestive enzymes and bicarbonate. 4. Salivary Glands: It has a cleansing action on the teeth, it moistens and lubricates food during mastication and swallowing, it dissolves certain molecules so that food can be tasted, it begins the chemical digestion of starches through the action of amylase, which breaks down polysaccharides into disaccharides.

List the general functions of the digestive system.

1. Mouth -Major Function: Ingests food, chews and mixes food, chemical breakdown or carbs, moves food into the pharynx, begins breakdown of lipids via lingual lipose. -Other functions: Moistens and dissolves food, cleans and lubricates teeth and oral cavity, antimicrobial activity. 2. Pharynx -Major Functions: Propels food from the oral cavity to the esophagus. -Other Functions: Lubricates food and passageways 3. Esophagus -Major Functions: Propels food to the stomach -Other Functions: Lubricates food and passageways 4. Stomach -Major Functions: Mixes and churns food with gastric juices to form chyme, chemical breakdown or proteins, releases food into the duodenum as chyme, absorbs some fat-soluble substances (ex: alcohol and aspirin), possesses antimicrobial functions. -Other Functions: Stimulates protein-digesting enzymes, secretes intrinsic factor for vitamin, B12 absorption in small intestine. 5. Small Intestines -Major Functions: Mixes chyme with digestive juices, propels food at a rate slow enough for digestion and absorption, absorbs broken down products of carbs, proteins, lipids, and nucleic acids, along with vitamins, minerals, and water; performs physical digestion via segmentation. -Other Functions: Provides optimal medium for enzymatic activity.

Which of these ingredients in saliva is responsible for activating salivary amylase?

Chloride ions

Which of these processes occurs in the mouth?

All of the above (ingestion, mechanical digestion, and chemical digestion)

Which of these statements about bile is true?

Bile salts are recycled

Pancreatic juice ________.

Buffers chyme

Which part of the large intestine attaches to the appendix?

Cecum

Which of the following stimuli activates sensors in the walls of digestive organs?

Distension

Which of these cells secrete hormones?

Enteroendocrine cells

Which structure is located where the esophagus penetrates the diaphragm?

Esophageal Hiatus

Which phase of deglutition involves contraction of the longitudinal muscle layer of the muscularis?

Esophageal phase

Which of the following organs is supported by a layer of adventitia rather than serosa?

Esophagus

Where does the majority of chemical digestion in the stomach occur?

Fundus and body

Parietal cells secrete ________.

Gastrin

Which of these nutrients is absorbed mainly in the duodenum?

Iron

Which of these is most associated with villi?

Lacteals

Know where chemical and mechanical digestion takes place throughout the digestive system.

Mechanical digestion involves physically breaking the food into smaller pieces. Mechanical digestion begins in the mouth as the food is chewed. Chemical digestion involves breaking down the food into simpler nutrients that can be used by the cells. Chemical digestion begins in the mouth when food mixes with saliva. (teeth, tongue: mechanical; salivary glands: chemical)

Where does the chemical digestion of starch begin?

Mouth

Which of these organs is not considered an accessory digestive structure?

Mouth

Know the path unabsorbed food takes through the digestive system.

Mouth --> pharynx --> esophagus --> gastroesophegial --> sphincter --> stomach --> cardia --> fundus --> body --> pyloric canal --> pyloric sphincter --> small intestines --> ileroceral sphincter --> large intestines --> anal canal

Where are most fat-digesting enzymes produced?

Pancreas

What is the role of the small intestine's MALT?

Preventing bacteria from entering the bloodstream

Which of these processes occurs throughout most of the alimentary canal?

Propulsion

In which part of the alimentary canal does most digestion occur?

Proximal small intestine

During gastric emptying, chyme is released into the duodenum through the ________.

Pyloric sphincter

Which of these statements about reflexes in the GI tract is false?

Short reflexes are provoked by nerves near the GI tract

What nervous system controls the digestive system? How does it control the digestive system?

The autonomic nervous system controls the tone of the digestive tract. The brain controls muscles for eating and elimination. The digestive system sends sensory information to the brain. Hormone Regulators.

Which of these statements about the pharynx is true?

The oropharynx is continuous superiorly with the nasopharynx

Which of these is involved in the chemical digestion of protein?

Trypsin

Which of the following membranes covers the stomach?

Visceral peritoneum