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Questions and Answers
Which of the following structures is not an accessory structure of the GI tract?
What is the main function of peristalsis in the GI tract?
Which type of nerve stimulates GI tract activities?
What is the function of amylase enzyme in saliva?
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Which part of the GI tract is responsible for segmentation?
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What is the main function of the reflex mechanism in the GI tract?
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What percentage of the pancreas mass is devoted to its exocrine function?
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Which cell type produces sodium bicarbonate to neutralize acidic gastric contents?
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What is the primary function of the tongue during mastication?
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What is the primary function of pancreatic amylase?
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What is the name of the lump formed during mastication that facilitates easier passage into the pharynx?
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What activates trypsinogen into trypsin?
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What is the human dental formula?
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What is the primary function of salivary glands?
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What is the effect of the parasympathetic nervous system on pancreatic secretion?
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What is the pH range of saliva?
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What is the primary function of pancreatic proteinases?
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What is the primary function of the stomach?
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What is the function of Cholecystokinin (CCK) in the digestive system?
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What is the purpose of the watery fluid secreted by intestinal glands in the small intestine?
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What is the function of enterokinase in the digestive system?
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What is the purpose of the hepatopancreatic sphincter in the digestive system?
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What is the function of lipases in the small intestine?
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What stimulates the secretion of small intestine secretions?
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What is the primary function of villi in the small intestine?
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How are fatty acids absorbed in the small intestine?
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What is the primary function of the large intestine?
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What type of capillaries are found in villi to absorb long-chain fatty acids?
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What is the role of goblet cells in the large intestine?
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What is the mechanism that helps in the formation of feces in the large intestine?
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Study Notes
Accessory Structures of the GI Tract
- Includes teeth, tongue, salivary glands, liver, gallbladder, and pancreas.
Muscular Movement of the GI Tract
- Peristalsis: Wavelike movement from oropharynx to rectum that pushes food towards the anus.
- Mixing: Mechanical digestion in oral cavity and stomach that breaks down food into smaller particles.
- Segmentation: Independent contraction and relaxation of small intestine regions enhance digestion and absorption efficiency.
Regulation of GI Tract Activities
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Nervous System:
- Parasympathetic nerves stimulate GI functions.
- Sympathetic nerves inhibit GI functions.
- Hormonal Control: Endocrine glands and GI tract hormones regulate activities.
- Reflex Mechanism: Reflexes help stimulate or inhibit GI regions, especially in the stomach and small intestine.
Mouth and Oral Cavity
- Food enters via ingestion, undergoing mechanical digestion through mastication.
- Salivary amylase begins the chemical digestion of polysaccharides into disaccharides.
- Pancreatic Function: 98% of pancreas mass is exocrine, producing pancreatic juice; ductile cells secrete sodium bicarbonate to neutralize gastric contents.
- Acinar cells produce digestive enzymes for nutrient breakdown.
Major Pancreatic Enzymes
- Pancreatic Amylase: Digests polysaccharides.
- Pancreatic Lipases: Break down triglycerides into fatty acids.
- Pancreatic Nucleases: Digest nucleic acids into nucleotides.
- Pancreatic Proteinases: Inactive forms digest peptides; activated by trypsin.
Activation of Pancreatic Proteases
- Trypsinogen converted to trypsin, which activates other enzymes: chymotrypsinogen to chymotrypsin, proaminopeptidase to aminopeptidase, procarboxypeptidase to carboxypeptidase.
Pancreatic Secretion Regulation
- Increased secretion from parasympathetic nervous system.
- Hormones from the duodenum, Secretin and Cholecystokinin, influence secretion.
Tongue Function
- Composed of skeletal muscle, manipulates food and houses taste buds.
- Forms a bolus during mastication for easy passage to the pharynx.
Teeth
- Specialized for mechanical digestion with 20 primary teeth before age 6 and 32 permanent teeth by age 7.
- Types of teeth: Incisors (cutting), Canines (tearing), Premolars (crushing), Molars (grinding).
Salivary Glands
- Three pairs: parotid, submandibular, sublingual; responsible for saliva secretion.
- Saliva is 99.5% water, contains amylase, bicarbonate, and electrolytes; aids in moisten food and cleans teeth.
Stomach Function
- Pouch-like organ for food storage (2-4 hours) and some digestion.
- Cholecystokinin (CCK) released from intestinal mucosa stimulates gallbladder contraction and bile release into the duodenum.
Small Intestine Structure
- Long tube (1-inch diameter) from pyloric sphincter to ileocecal valve, divided into Duodenum, Jejunum, and Ileum.
- Intestinal glands secrete fluid that aids in moving chyme; digestive enzymes act on sugars, proteins, and fats.
Absorption in the Small Intestine
- Each villus contains blood capillaries for absorbing nutrients and lacteals for fatty acids.
- Water absorbed by osmosis, fatty acids by diffusion, glucose and amino acids by active transport.
Large Intestine Overview
- Final GI tract segment (2-3 inches in diameter) from ileocecal valve to anus.
- Components: cecum, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, anal canal, anus.
Functions of the Large Intestine
- Lacks significant digestive function but secretes mucus; contains goblet cells for mucus production.
- Absorbs water, electrolytes, and some vitamins; bacteria present break down indigestible substances and synthesize vitamins.
- Feces formation and storage occurs in the large intestine; defecation involves both reflex actions and voluntary muscle contractions.
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Description
This quiz covers the accessory structures of the digestive system, including teeth, tongue, and salivary glands, as well as the muscular movement of the GI tract, including peristalsis and mixing. Test your knowledge of the digestive system!
