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Questions and Answers
The pancreas lies posterior to the ______.
The pancreas lies posterior to the ______.
stomach
The endocrine cells of the pancreatic islets secrete ______ and glucagon.
The endocrine cells of the pancreatic islets secrete ______ and glucagon.
insulin
Pancreatic lipase breaks down complex ______.
Pancreatic lipase breaks down complex ______.
lipids
The liver is responsible for metabolic and hematological ______.
The liver is responsible for metabolic and hematological ______.
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The gallbladder stores and concentrates ______ prior to excretion.
The gallbladder stores and concentrates ______ prior to excretion.
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The large intestine extends from the end of the ileum to the ______.
The large intestine extends from the end of the ileum to the ______.
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The cecum receives material arriving from the ______.
The cecum receives material arriving from the ______.
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The rectum forms the last ______ cm of the digestive tract.
The rectum forms the last ______ cm of the digestive tract.
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The primary function of the digestive system is to acquire __________ from the environment.
The primary function of the digestive system is to acquire __________ from the environment.
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__________ is the process that decomposes substances to provide energy cells need to function.
__________ is the process that decomposes substances to provide energy cells need to function.
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Ingestion occurs when material enters via the __________.
Ingestion occurs when material enters via the __________.
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The process of moving organic substrates, electrolytes, vitamins, and water across the digestive epithelium is known as __________.
The process of moving organic substrates, electrolytes, vitamins, and water across the digestive epithelium is known as __________.
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The rhythmic, wave-like contractions that move a bolus along the digestive tract are called __________.
The rhythmic, wave-like contractions that move a bolus along the digestive tract are called __________.
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The major functions of the stomach include storage of ingested food and mechanical __________ of ingested food.
The major functions of the stomach include storage of ingested food and mechanical __________ of ingested food.
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The segment of the small intestine closest to the stomach is called the __________.
The segment of the small intestine closest to the stomach is called the __________.
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Villi are tiny, finger-like projections in the small intestine that help absorb __________ and water.
Villi are tiny, finger-like projections in the small intestine that help absorb __________ and water.
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The final segment of the small intestine is known as the __________.
The final segment of the small intestine is known as the __________.
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Gastric rugae, or gastric folds, in the stomach allow it to __________ and increase its surface area.
Gastric rugae, or gastric folds, in the stomach allow it to __________ and increase its surface area.
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Study Notes
Digestive System Function
- Acquires nutrients from the environment
- Anabolism: Uses raw materials to build complex molecules, requiring energy and reducing power.
- Catabolism: Breaks down substances to provide energy for cellular functions.
Digestive (GI) Tract
- Oral Cavity, Teeth, Tongue: Mechanically processes food, moistens it, and mixes it with saliva.
- Mouth: Entrance to the digestive system.
- Liver: Secretes bile for lipid digestion, stores nutrients, and performs various vital functions.
- Gallbladder: Stores and concentrates bile.
- Pancreas: Secretes buffers and digestive enzymes. Also produces hormones.
- Large Intestine: Dehydrates and compacts indigestible materials for elimination.
- Salivary Glands: Secrete lubricating fluid containing enzymes that break down carbohydrates.
- Pharynx: Muscular propulsion of materials into the esophagus.
- Esophagus: Transports materials to the stomach.
- Stomach: Mechanically breaks down food; chemically breaks down food using acid and enzymes. Produces intrinsic factor needed for Vitamin B12 absorption.
- Small Intestine: Enzymatically digests and absorbs water, organic substrates, vitamins, and ions. Consists of three sections: duodenum, jejunum, and ileum.
Actions of the GI Tract
- Ingestion: Material enters the mouth.
- Secretion: Release of water, acids, buffers, enzymes, and salts by the GI tract and glandular organs.
- Mechanical Processing: Crushing and shearing of materials to make them easier to move through the tract.
- Absorption: Movement of organic substrates, electrolytes, vitamins, and water across the epithelium of the digestive tract.
- Digestion: Chemical breakdown of food into smaller components.
- Excretion: Removal of waste products from the body.
Movement of Digestive Materials
- Peristalsis: Rhythmic cycles of muscular contractions moving a bolus (a mass of food) along the digestive tract.
Functions of Oral Cavity
- Sensory Analysis: Of material before swallowing.
- Mechanical Processing: Through actions of teeth, tongue, and palatal surfaces.
- Lubrication: Mixing with mucus and salivary secretions
- Limited Digestion: Of carbohydrates and lipids.
Esophagus
- A hollow muscular tube, about 25 cm long and 2 cm wide.
- Conveys solid food and liquids to the stomach.
Stomach Function
- Major Functions: Storage of ingested food; Mechanical breakdown of ingested food; Chemical breakdown of chemical bonds in food materials by producing acid and enzymes; and Production of intrinsic factor for vitamin B12 absorption.
Digestion in the Stomach
- Performs preliminary digestion of proteins by pepsin
- Some digestion of carbohydrates (by salivary amylase)
- Lipids: digested by lingual lipase
- Stomach contents become more fluid; pH approaches 2.0; pepsin activity increases; protein disassembly begins.
- Nutrients are NOT generally absorbed in the stomach
Small Intestine
- 90% of absorption occurs in the small intestine
- The duodenum is the first part; receives chyme from the stomach and digestive secretions from the pancreas and liver. Neutralizes stomach acids.
- The jejunum is the middle segment; mostly responsible for chemical digestion and absorption of nutrients.
- The ileum is the final segment; absorbs remaining nutrients and ends at the ileocecal valve.
Small Intestine - Intestinal Secretions
- Watery intestinal juice is secreted in liters in the small intestine.
- The juice moistens chyme, assists in buffering acids, and keeps digestive processes active.
- Chyme arrives in the duodenum, and weak peristaltic contractions move it slowly to the jejunum.
Villi
- Tiny, finger-like projections in the small intestine that help absorb nutrients and water
Rugae
- Gastric rugae (folds) in the stomach expand to increase surface area.
Pancreas
- Located posterior to the stomach, extending toward the spleen
- Endocrine Function: Secretes insulin and glucagon into the bloodstream.
- Exocrine Function: Secretes pancreatic juice
Pancreatic Enzymes
- Pancreatic amylase breaks down starches, similar to salivary amylase
- Pancreatic lipase breaks down complex lipids into fatty acids for absorption
Liver
- Has a right and left lobe
- Hepatocytes: Are liver cells that adjust circulating nutrient levels through selective absorption and secretion. Many Kupffer cells are also located in the liver (resident macrophages that play a role in maintaining liver function).
- Functions: Metabolic regulator, Hematological regulator, Bile production
Gallbladder
- Pear-shaped, muscular sac
- Stores and concentrates bile, releases bile into the duodenum
Large Intestine
- Horseshoe-shaped
- Extends from the end of the ileum to the anus.
- Lies inferior to the stomach and liver, framing the small intestine; also called the large bowel).
- About 1.5 meters (4.9 ft) long, and 7.5 cm (3 in) wide.
Large Intestine Functions
- Reabsorption of water
- Compaction of intestinal contents into feces.
- Absorption of vitamins produced by bacteria
- Storage of fecal material prior to defecation
Parts of Large Intestine:
- Cecum: An expanded pouch that receives material from the ileum and begins compaction
- Appendix: A slender, hollow appendage, about 9 cm (3.6 in) long, dominated by lymphoid nodules.
- Colon: Has a larger diameter and thinner wall than the small intestine; forms a series of pouches called haustra to permit expansion. Parts of the colon include the ascending, transverse, descending and sigmoid colon.
- Rectum: Forms the last 15 cm (6 in) of the digestive tract, an expandable organ for temporary storage of feces; Movement of fecal material into the rectum triggers the urge to defecate.
- Anal Canal: Last portion of the rectum, with small longitudinal folds called anal columns
- Anus: Also called anal orifice, the exit of the anal canal, with keratinized epidermis like skin.
Physiology of the Large Intestine
- Absorption of water, bile salts, vitamins produced by bacteria, and organic wastes
- Bacteria generate ammonia and hydrogen sulfide from peptides in feces.
Three Vitamins Produced in the Large Intestine
- Vitamin K (fat soluble)
- Biotin (water soluble)
- Pantothenic acid (B5) (water soluble)
Organic Wastes:
- Bacteria break down peptides in feces.
- Generate ammonia and hydrogen sulfide
- Produce flatus (intestinal gas)
Digestion
- Digestive system handles each nutrient differently
- Large organic molecules must be digested before absorption.
- Water, electrolytes, and vitamins can be absorbed without processing.
Water Absorption
- Cells cannot actively absorb or secrete water.
- Water movement across the digestive tract lining involves passive water flow.
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Description
Explore the intricate functions and components of the digestive system in this quiz. From the oral cavity to the large intestine, learn how each part contributes to nutrient acquisition and energy production. Test your understanding of both anabolism and catabolism processes involved in digestion.
