40 Questions
What governs the control mechanisms of the gastrointestinal system according to the text?
Volume and composition of the luminal contents
What factor leads to an increase in the force of antral smooth muscle contractions in the stomach?
Expansion of the stomach walls
Which substance is mentioned in the text as influencing the force of initial stomach contraction after a large meal?
Gastrin
What is meant by 'luminal contents' in the context of gastrointestinal control mechanisms?
Food and other substances within the digestive tract
How does the body respond to nutrients ingested even when it may not need them according to the text?
It absorbs all nutrients for immediate use
What conditions inhibit gastric emptying in the duodenum?
Distension, presence of fat, high acidity, hypertonic solutions
Which segment of the small intestine is approximately 25 cm (10 in.) long?
Duodenum
Where does 90% of absorption occur in the digestive system?
Small intestine
What anatomical structures in the small intestine favor absorption and digestion?
Villi and microvilli
Which part of the pancreas secretes pancreatic juice into the small intestine?
Exocrine portion
Which of the following is NOT a function of the pharynx and esophagus during swallowing?
The stomach initiates mechanical breakdown and mixing of ingested food
Which of the following statements about the stomach is FALSE?
The stomach is responsible for the complete digestion and absorption of proteins
Which of the following statements about gastric glands is CORRECT?
Gastric glands are responsible for the production of pepsinogen, an inactive precursor of pepsin
Which of the following chemical messengers stimulates the production of hydrochloric acid (HCl) in the stomach?
Gastrin
Which of the following is NOT a function of the stomach?
Complete absorption of water and electrolytes from the ingested food
What triggers reflex relaxation of the external anal sphincter to allow feces expulsion?
Pressure in the rectum
What is the most common location for peptic ulcers?
Lower part of the stomach
Which enzyme and acid combination is typically responsible for causing ulcers?
Pepsin and acid
What symptom is characteristic of peptic ulcers?
Dull continuous ache
What serious condition can result from a perforated ulcer?
Peritonitis
What is the primary function of the pharynx and esophagus?
Mixing and propulsion of food into the stomach
Which of the following is NOT a type of gastric gland found in the stomach?
Duodenal glands
Which hormone plays a key role in regulating the production of hydrochloric acid (HCl) in the stomach?
Gastrin
What is the primary function of the stomach?
Storage and mixing of ingested food
Which part of the stomach is responsible for storing and concentrating bile prior to excretion into the small intestine?
Gallbladder
What is the primary function of the pancreatic enzyme amylase?
Digestion of carbohydrates
Which of the following is NOT a component of bile secreted by the liver?
Pepsin
What is the primary function of the hepatic portal system?
To deliver absorbed nutrients to the liver for processing
Which of the following is NOT a function of bile secreted by the liver?
Digestion of carbohydrates
What is the primary function of the pancreatic enzyme lipase?
Digestion of lipids
What is the primary function of the pharynx?
To facilitate the passage of food from the oral cavity to the esophagus
Which of the following is NOT a function of the esophagus?
Secretion of enzymes to initiate protein digestion
Which type of gastric gland is responsible for the production of hydrochloric acid (HCl) in the stomach?
Parietal cells
Which hormone is primarily responsible for stimulating the production of hydrochloric acid (HCl) in the stomach?
Gastrin
Which part of the stomach is primarily responsible for the mechanical breakdown of food?
Antrum
Which of the following is NOT a function of the stomach?
Secretion of enzymes for lipid digestion
Which part of the stomach is primarily responsible for the temporary storage of ingested food?
Fundus
Which of the following cells in the gastric glands are responsible for the production of pepsinogen?
Chief cells
What is the primary function of the pyloric sphincter in the stomach?
To regulate the flow of chyme into the small intestine
Which part of the stomach is responsible for the production of intrinsic factor, necessary for vitamin B12 absorption?
Body
Study Notes
Gastrointestinal System
- The body absorbs all nutrients ingested, regardless of whether they are needed or not.
- Control mechanisms of the gastrointestinal system are governed by the volume and composition of the luminal contents.
Stomach
- Gastric motility is increased by the concentration of gastrin and distension of the stomach.
- The force of initial stomach contractions is greater after a large meal, resulting in a greater emptying per contraction.
- Gastric emptying is inhibited by distension, presence of fat, high acidity, and hypertonic solutions in the duodenum.
Small Intestine
- 90% of absorption occurs in the small intestine.
- The small intestine is divided into three segments: duodenum, jejunum, and ileum.
- It is composed of fingerlike villi and microvilli structures, which increase the surface area for absorption and digestion.
Absorption in the Small Intestine
- The small intestine is anatomically arranged for a large surface area, enhancing absorption of nutrients.
- Villi increase surface area and contain blood vessels and lacteal, which play a role in absorption.
- Microvilli increase surface area and form the brush border.
Pancreas
- The pancreas has both exocrine and endocrine functions.
- The exocrine portion secretes pancreatic juice into the small intestine, which is rich in bicarbonate and digesting enzymes.
- Pancreatic secretions break down triglycerides into monoglycerides and 2 fatty acids.
Regulation of HCl Production
- Parietal cells in the stomach secrete about 2L of HCl per day.
- The acid secretion is regulated by four chemical messengers: gastrin, acetylcholine, histamine, and somatostatin.
- Somatostatin inhibits acid secretion, while the other three stimulate it.
Pathophysiology of the Gastrointestinal Tract
- Ulcers affect approximately 10% of the population in the USA.
- Ulcers are an erosion of the lining of the GI wall, usually due to pepsin and acid.
- Symptoms include a chronic rhythmic and periodic gnawing or burning pain.
Liver and Gall Bladder
- The liver serves as a secretory organ, secreting bile.
- Bile is a yellow-brownish liquid that contains bile salts, bicarbonate, lecithin, cholesterol, bilirubin, and other ions.
- Functions of bile include emulsifying large lipid molecules and neutralizing acidic chyme.
Hepatic Portal System
- The Hepatic Portal System is a specialized vasculature that delivers absorbed nutrients to the liver for processing.
- It is responsible for the synthesis of plasma proteins, processing and storing nutrients, and removal of old red blood cells.
Large Intestine
- The large intestine consists of the cecum, colon, and rectum.
- Functions of the large intestine include absorption of salt and water, mixing and propulsion of contents, storage and concentration of undigested matter, and defecation.
Motility of the Large Intestine and Defecation
- Contractions of the circular smooth muscle in the large intestine produce a segmentation motion.
- Three to four times a day, a wave of intense contraction known as a mass movement spreads rapidly over the transverse segment of the large intestine toward the rectum.
- The sudden distension of the walls of the rectum initiates the defecation reflex.
Learn about the breakdown process of triglycerides by lipase, the movement of food through the pharynx and esophagus, and the key functions of the stomach in the digestive system.
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