38 Questions
What is the primary function of peristalsis in the digestive system?
To propel food through the digestive tract
Which type of movement in the digestive system promotes solubilization and absorption of food?
Mixing movements
What type of muscle contraction is involved in segmentation?
Circular smooth muscles only
Which phase of gastric secretion is triggered by the presence of acid, carbohydrates, lipids, and undigested proteins in the duodenum?
Intestinal phase
What is the role of gastrointestinal hormones in the intestinal phase of gastric secretion?
They stimulate the release of enzymes
Which movement in the digestive system results in slow food propulsion?
Segmentation
What process do small aquatic sessile animals utilize to obtain food?
Filter or suspension feeding
Which process involves the engulfing of larger food particles?
Phagocytosis
What mechanism is used to take up smaller nutrient particles?
Pinocytosis
What happens after the food particles are engulfed or taken up by the cell?
They fuse with a lysosome containing digestive enzymes
What is the main difference between phagocytosis and pinocytosis?
Phagocytosis involves engulfing larger food particles, while pinocytosis involves taking up smaller nutrient particles
Which process is a more active form of feeding?
Endocytosis
What is the role of HCO3- secreted by Brunner's glands in the duodenum?
To aid in the activation of some intestinal enzymes needed for absorption
Which cells secrete somatostatin and inhibit pepsinogen, HCl, and gastrin release?
D cells
Which type of fluid secreted by the mammalian small intestine contains enzymes that aid in digestion?
Thinner, enzyme-rich alkaline fluid from the crypts of Lieberkühn
What is the function of the crypts of Lieberkühn in the small intestine?
To secrete a thinner, enzyme-rich alkaline fluid
Which of the following substances is not secreted by the mammalian small intestine?
Gastrin
What is the role of the alkalinity provided by Brunner's glands in the duodenum?
To activate some intestinal enzymes needed for absorption
What is the primary function of the salivary glands in the digestive system?
To initiate the chemical digestion of carbohydrates and fats
What is the main function of the midgut in the digestive system?
To digest and absorb nutrients
What type of food generally requires a longer period of digestion?
Low-quality food
What is the main function of the hindgut in the digestive system?
To absorb water before digestive material is expelled during defecation
Which division of the alimentary canal is responsible for receiving ingested material?
Headgut
What is the primary function of the foregut in the digestive system?
To conduct, store, and digest ingested material
Which of the following is not a function of the tongue in the digestive system?
Initiating the chemical digestion of carbohydrates
What is the main function of the esophagus in the digestive system?
To carry food from the headgut to the stomach
What is the main function of the crop in the digestive system?
To conduct, store, and digest ingested material
Which of the following is not a function of saliva in the digestive system?
Solvent for molecules that stimulate taste buds
Which hormone is synthesized and released by I-cells in the duodenum in response to fat and protein-rich chyme?
Cholecystokinin (CCK)
Which hormone is primarily responsible for inducing insulin secretion from the pancreas in response to carbohydrates and fat-rich chyme?
Gastric Inhibitory Peptide (GIP)
Which enzymes function at the brush border membrane in the small intestine, rather than directly in the lumen?
Enterokinase, sucrase, lactase, aminopeptidase
Which hormone is synthesized and released by S-cells in the duodenum when exposed to the acidic contents of an emptying stomach?
Secretin
Which hormone is synthesized and released by enteroendocrine cells in the duodenum in response to fat-rich chyme?
Vasoactive Intestinal Peptide (VIP)
Which part of the digestive system acts to store the remnants of the digested food, reabsorbs inorganic ions, and excess water into the circulatory system, and defecates faeces?
Hindgut
Which hormone is commonly referred to as glucose-dependent insulinotropic peptide (GIP) due to its role in inducing insulin secretion from the pancreas?
Gastric Inhibitory Peptide (GIP)
Which part of the digestive system conducts, stores, and digests ingested material?
Foregut
Which enzyme is responsible for stimulating the pancreatic enzyme release for protein digestion?
Cholecystokinin (CCK)
Which hormone stimulates the secretion of salt and water into the duodenum and HCO3- secretion by the pancreas?
Vasoactive Intestinal Peptide (VIP)
Study Notes
Feeding Mechanisms
- Feeding mechanisms include peristalsis, mixing movements, and segmentation to facilitate digestion and absorption.
- Peristalsis involves the contraction and relaxation of circular and longitudinal smooth muscles to propel the bolus forward.
- Segmentation involves the alternate contraction and relaxation of circular smooth muscles to mix food and digestive enzymes.
Digestive System Anatomy and Function
- The digestive system consists of four main divisions: headgut, foregut, midgut, and hindgut.
- The headgut receives ingested material, the foregut conducts, stores, and digests ingested material, the midgut digests and absorbs nutrients, and the hindgut absorbs water and expels waste.
Midgut Motility
- Peristalsis involves the contraction and relaxation of adjacent segments of the tract to propel the bolus forward.
- Segmentation involves the alternate contraction and relaxation of segments of the tract to mix food and digestive enzymes.
Intestinal Phase of Secretion
- The intestinal phase of secretion involves the release of gastrointestinal hormones in response to the presence of chyme in the duodenum.
- Hormones released include cholecystokinin (CCK), secretin, vasoactive intestinal peptide (VIP), and gastric inhibitory peptide (GIP).
- These hormones regulate gastric motility, acid secretion, and pancreatic enzyme release.
Endocytosis
- Endocytosis is a more active form of feeding that involves the engulfment of food particles by the cell.
- There are two types of endocytosis: phagocytosis (engulfment of larger particles) and pinocytosis (engulfment of smaller particles).
Filter or Suspension Feeding
- Filter or suspension feeding involves the use of cilia or flagella to generate water currents that bring in nutrients.
- This type of feeding is used by small aquatic sessile animals.
Digestive Systems
- Digestive systems combine features of continuous-flow and plug-flow reactors.
- The design of the digestive system must match the quality of food that the animal eats.
- Herbivores have a longer digestive system to accommodate lower quality food, while carnivores have a shorter digestive system to accommodate high-quality food.
Food Quality and Digestion
- Food quality affects the time required for digestion.
- High-quality food requires less energy and time for digestion, while low-quality food requires more energy and time.
- Digestive systems are adapted to the type of food an animal eats.
General Plan of Vertebrate Digestive System
- The vertebrate digestive system consists of the mouth, pharynx, esophagus, stomach, small intestine, and large intestine.
- Accessory digestive organs include salivary glands, exocrine pancreas, and the biliary system.
Headgut
- The headgut receives ingested material and consists of the mouth, oral cavity, pharynx, teeth, bills/beak, tongue, and salivary glands.
- The tongue assists in mechanical digestion and swallowing, and contains chemoreceptors (taste buds).
- Salivary glands produce saliva that lubricates food, begins digestion of carbohydrates, and has antibacterial properties.
Salivary Glands
- There are three major salivary glands: sublingual, submandibular, and parotid.
- Saliva contains 99.5% water, 0.5% electrolytes and proteins, including amylase, lingual lipase, and mucin.
- Salivary secretion is a two-stage process involving acinar cells and duct cells.
Foregut
- The foregut conducts, stores, and digests ingested material.
- The primary organs of the foregut are the pharynx, esophagus, and crop.
Hindgut
- The hindgut absorbs water and expels waste.
- The hindgut in vertebrates consists of the large intestine or colon (including the cecum) and the rectum.
- The hindgut terminates in a cloaca in many vertebrates.
Explore the feeding mechanisms of tapeworms, focusing on how small molecules like amino acids are taken in by transport mechanisms, and how larger molecules are absorbed through bulk processes such as endocytosis. Learn about phagocytosis and the active form of feeding involved in this process.
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