Human Digestive System Quiz

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Questions and Answers

What is the primary function of the ileo-cecal valve?

To absorb water from chyme

To enhance the absorption of vitamins

To facilitate the passage of food to the rectum

To prevent back flow of chyme from the small intestine (correct)

Which section is the last part of the large intestine?

Cecum

Rectum

Transverse colon

Sigmoid colon (correct)

Which vitamins are absorbed in the large intestine?

A and C

D and E

Folate and B12

B and K (correct)

What term describes the process that involves strong peristaltic waves occurring in the large intestine?

Mass peristalsis Signup and view all the answers

How long does chyme generally spend in the large intestine before being converted into feces?

7-10 hours Signup and view all the answers

What reflex initiates mass peristalsis in the large intestine?

Gastro-colic reflex Signup and view all the answers

What primarily contributes to the color of feces?

Stercobilin generated from bilirubin breakdown Signup and view all the answers

Which structure controls involuntary defecation?

Internal anal sphincter Signup and view all the answers

Which components are primarily absorbed in the small intestine?

Water, minerals, and water-soluble vitamins Signup and view all the answers

Which type of cell in the small intestine is primarily responsible for nutrient absorption?

Absorptive cells Signup and view all the answers

What role do brush border enzymes play in carbohydrate digestion?

They convert disaccharides into monosaccharides Signup and view all the answers

During the defecation reflex, which bodily function is primarily activated?

Contraction of rectal muscles Signup and view all the answers

What is the primary function of gastric juice in the stomach?

To dissolve food and mix it into chyme Signup and view all the answers

Which cell type in the stomach secretes hydrochloric acid?

Parietal cells Signup and view all the answers

What happens to salivary amylase in the acidic environment of the stomach?

It gets inactivated Signup and view all the answers

Which part of the stomach is directly involved in the passage of chyme into the small intestine?

Pylorus Signup and view all the answers

Which substance is secreted by G cells in the stomach?

Gastrin Signup and view all the answers

What is the 'alkaline tide' associated with in the stomach?

Increase of bicarbonate ions in the circulation Signup and view all the answers

What is the role of pepsin in the stomach?

To digest proteins Signup and view all the answers

What primarily distinguishes the pyloric antrum from the pyloric canal?

Size and function Signup and view all the answers

Which mechanism is responsible for the secretion of hydrogen ions in the stomach?

Active transport via proton pump Signup and view all the answers

How does the stomach ensure that proteins are optimally digested?

By maintaining a low pH with HCl Signup and view all the answers

What is the primary mechanism by which monosaccharides are absorbed in the small intestine?

Facilitated diffusion for fructose and active transport for glucose and galactose Signup and view all the answers

How are dipeptides and tripeptides primarily absorbed in the small intestine?

Mostly through active transport Signup and view all the answers

What role do micelles play in the absorption of lipids?

They encapsulate fatty acids to facilitate diffusion across intestinal cells Signup and view all the answers

What is the intestines' movement speed of chyme as it travels towards the large intestine?

10 cm/sec Signup and view all the answers

What percentage of lipid absorption occurs in the small intestine?

95% Signup and view all the answers

Which type of vitamins can be absorbed alongside fatty acids in the small intestine?

Lipid-soluble vitamins: A, D, E, and K Signup and view all the answers

What mechanism governs the absorption of water in the intestines?

Simple diffusion and osmotic gradients Signup and view all the answers

Which phase of gastric secretion is initiated by the smell and sight of food?

Cephalic phase Signup and view all the answers

What nutrients are broken down by pancreatic lipase during lipid digestion?

Triglycerides into fatty acids and monoglycerides Signup and view all the answers

What role do stretch receptors in the stomach play during the gastric phase?

Ensuring proper motility and acid secretion Signup and view all the answers

What stimulates the production of intestinal juices in the digestive process?

Vasoactive intestinal polypeptide (VIP) Signup and view all the answers

What is the significance of stretching in the small intestine?

It plays a role in the 'segmentation' process Signup and view all the answers

What physiological effect does gastrin have when released into the bloodstream?

Stimulates the release of gastric juices Signup and view all the answers

What is the primary purpose of secretin in the intestinal phase of digestion?

Stopping gastric secretion Signup and view all the answers

How does the body regulate the emptying of the stomach during the intestinal phase?

Through negative feedback mediated by intestinal hormones Signup and view all the answers

Which neurotransmitter is released by the parasympathetic fibers to stimulate gastric secretion during the gastric phase?

Acetylcholine Signup and view all the answers

What happens to the pH of the stomach as partially digested proteins enter, and why is it significant?

It rises, inhibiting gastric secretion Signup and view all the answers

What is one of the main functions of cholecystokinin (CCK) in the digestive process?

Inhibiting stomach emptying Signup and view all the answers

What is the effect of the vagus nerve during the cephalic phase of digestion?

It stimulates secretion of digestive juices Signup and view all the answers

Study Notes

Stomach

The stomach is a portion of the digestive tract, capable of storing 1.5-2 liters of food.
It has three layers of muscle within its walls.
Four major parts of the stomach are: Cardia, Fundus, Body, and Pylorus (including Pyloric Antrum, Pyloric Canal, and Pyloric Sphincter).
The stomach's curved shape is characterized by the greater and lesser curvatures.
The stomach lining (mucosa) is folded into rugae.

Stomach Glands

Surface mucous cells secrete mucus.
Mucous neck cells secrete mucus.
Parietal cells secrete hydrochloric acid and intrinsic factor (for vitamin B12).
Chief cells secrete pepsinogen and gastric lipase.
G cells secrete gastrin.

Stomach Function

Mixing waves, rather than peristaltic waves, mix food with gastric juice, converting it to a liquid called chyme.
Stomach acid inactivates salivary amylase but activates lingual lipase, which begins the breakdown of triglycerides.
A proton pump, which is an H+/K+ pump, utilizes ATP to move hydrogen ions into the stomach lumen, activating pepsinogen into pepsin.
Hydrochloric acid (HCl) created helps eliminate microorganisms, denatures proteins, and stimulates hormone production which facilitates bile and pancreatic juice production

Regulation of Gastric Secretion and Motility

Cephalic, gastric, and intestinal phases are overlapping stages of digestion, influenced by various neural and hormonal factors.
Cephalic phase: Initiated by stimuli other than food ingestion, like smell, sight, or thoughts of food. This stimulates medulla oblongata, initiating the secretion of pepsinogen, mucus, and HCl. Gastrin hormone also is released to bloodstream.
Gastric phase: Initiated by stretching and increased pH inside the stomach. Stretch and pH receptors initiate continuous gastric secretion as long as food is present. Peristalsis pushes chyme into the duodenum.
Intestinal phase: When chyme enters the small intestine, intestinal reflexes inhibit gastric secretion and slow stomach emptying to prevent overwhelming the duodenum with chyme. Chyme causes secretion of secretin and cholecystokinin (CCK) which inhibits further gastric emptying.

Small Intestine

The small intestine is a long, highly absorptive section of the gastrointestinal tract (approximately 3-3.5 meters).
It has three sections: duodenum, jejunum, and ileum.
Inner lining (mucosa) features circular folds, villi, and microvilli to maximize absorption surface area.
It's connected to the posterior abdominal wall by the mesentery.
The small intestine creates intestinal juice, essential to process chyme and contains different cell types including: Absorbent, goblet, enteroendocrine, and paneth cells.

Chemical digestion in large intestine

Bacteria in the large intestine break down remaining proteins, resulting in amino acids.
Bilirubin breakdown yields stercobilin (feces color).
B and K vitamins are absorbed.
Approximately 0.9 liters of fluid are absorbed in the large intestine, along with sodium, chloride, and some water-soluble vitamins.

Defecation Reflex

The rectum (ampulla) is a temporary storage site for digestive waste products.
Stretch receptors in the rectum initiate a reflex that enforces large intestine emptying by stimulating parasympathetic fibers.
Voluntary sphincter control allows the passage of feces.

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Description

Test your knowledge on the functions and anatomy of the large intestine in the human digestive system. This quiz covers key aspects such as the ileo-cecal valve, nutrient absorption, and the processes involved in defecation. Challenge yourself and see how much you know about this vital organ.