Digestive System - Mod. 3 Flashcards
What role does the oral cavity have in the digestive system?
It is where the initial phases of mechanical and chemical digestion begin, it also plays an important role in sensing the food contained within it, such as taste, texture, and temperature.
What is the vermillion border?
The line marking the border between the lips and the regular skin.
When does chemical digestion begin?
When the salivary glands secrete saliva into the mouth.
What are the two types of salivary glands that saliva is produced by?
The intrinsic (minor) salivary glands, and the extrinsic (major) salivary glands.
What are intrinsic (minor) salivary glands?
Glands within the oral cavity that secrete saliva directly into the mouth.
What are extrinsic (major) salivary glands?
Glands away from the oral cavity that secrete saliva into the mouth via a series of ducts.
What are the main components of saliva?
Water, small amounts of digestive enzymes, mucus, antibodies, and electrolytes (salts).
What are the functions of saliva?
- Soften and lubricate food so that it can be swallowed
- Begin the chemical digestion of food
- Ensure that food can be tasted
- Cleanse the teeth and mouth, keeping bacteria population under control
What is salivation?
The secretion of saliva
What can act as stimulants of salivation?
The taste and smell of food
What covers the surface of the tongue?
Papillae, some of which contain taste buds.
What are the functions of the tongue?
- Taste and sense the texture and temperature of food
- Manipulate the food under the teeth for chewing
- Compress the food into small round bolus for swallowing
- Aid in swallowing
What is the function of the intrinsic muscles of the tongue?
They are responsible for the intricate shape changes required for speech.
What is the function of the extrinsic muscles of the tongue?
They are responsible for the strong movements required for swallowing.
What is the function of the teeth?
To break up food in the mouth
What are the two sets of teeth that humans develop?
- Deciduous teeth (primary or baby teeth) - 20 teeth that grow in between 1-2 years old
- Permanent teeth - 32 teeth that replace the deciduous teeth and grow in between 6-20 years old.
What is the function of the incisors?
Cutting
What is the function of the canines?
Piercing
What is the function of the premolars?
Tearing
What is the function of the molars?
Crushing
What are the 3rd molars commonly called?
Wisdom teeth
What are the four parts of the tooth?
Crown, neck, root, and pulp cavity.
What are the four basic tissues of the teeth?
From hardest to softest: enamel, dentin, cementum, and pulp.
What is enamel?
The hardest substance in the body, covering the dentin of the crown.
What is dentin?
Hard tissue that makes up most of the tooth.
What is cementum?
Tough yellow tissue that covers the root, periodontal fibers are embedded within it.
What is the pulp?
Soft tissue within the pulp cavity containing nerves and blood vessels that nourish the dentin.
What is mastication?
Chewing
What is the function of the muscles of mastication?
They are involved in chewing, forcibly open and close the mandible, move it forwards and backwards, and from side to side.
What is the pharynx?
A U-shaped structure that connects the oral and nasal cavities with the esophagus, and is a common passage for solid food, liquids, and air.
What are the three parts of the pharynx?
From top to bottom: nasopharynx, oropharynx, laryngopharynx.
What is the esophagus?
A continuation of the pharynx that empties into the stomach inferiorly.
What is peristalsis?
It moves food through the digestive tract, starting in the esophagus and ending in the anus.
What is the function of the pharyngeal constrictor muscles?
They constrict to push food into the esophagus.
What are the three phases of swallowing?
- Buccal phase (oral phase)
- Pharyngeal phase
- Esophageal phase
What happens during the buccal phase of swallowing?
- Food is chewed, mixed with saliva, and pushed against the hard palate, forming a bolus.
- Then muscles of the soft palate and tongue contract to move it backwards.
- This phase is voluntary.
What happens during the pharyngeal phase of swallowing?
- The bolus moves into the pharynx and towards the esophagus.
- The soft palate is closed to prevent regurgitation.
- The epiglottis closes off the entrance to the larynx to prevent choking.
- Breathing is temporarily stopped, and the vagus nerve sends a cough reflex if anything enters the respiratory tract.
What happens during the esophageal phase of swallowing?
- The walls of the esophagus contract to propel the bolus down.
- Bolus reaches the lower esophageal sphincter, which relaxes, allowing the bolus to enter the stomach.
What is the primary function of the stomach?
Major site of digestion within the digestive tract, and secretion of gastric juice.
What are the main components of gastric juice?
Water, mucus, hydrochloric acid, intrinsic factor, and the enzyme pepsinogen.
What are gastric pits?
Small indentations in the stomach lining that produce gastric juice.
What are the three cell types that produce components gastric juice?
Parietal cells, chief cells, and neck mucous cells.
What do parietal cells produce?
Hydrochloric acid, making gastric juice very acidic.
What do chief cells produce?
Digestive enzymes, including pepsinogen and gastric lipase
What is pepsin and what does it do?
Proteolytic enzyme that breaks protein into amino acids and short chain peptides produced by chief cells as pepsinogen
What is the function of gastric lipase?
Breaks down lipids into fatty acids and monoglycerides
What are neck mucous cells?
Cells located in the neck of the gastric glands that produce mucus, protecting the lining of the stomach from hydrochloric acid and digestive enzymes
What are the accessory glands in the digestive system?
Pancreas, liver, and gallbladder
What do the accessory glands of the digestive system do?
Aid in chemical digestion of chyme as it passes into the small intestine
What percent of the specialized cells of the pancreas are exocrine?
99%
What is the function of the cells of acini?
They secrete pancreatic juice to neutralize stomach acid
What are the cells responsible for the endocrine role of the pancreas?
The Islets of Langerhans
What is the function of the islets of langerhans?
Secrete insulin and glucagon, regulating blood sugar levels
What are the functions of the liver?
- Produces urea and bile
- Stores and metabolizes fats
- Stores vitamins
- Metabolizes amino acids, sugars, and toxins
What is the bare area of the liver?
An area devoid of peritoneum, surrounded by the coronary ligaments and in direct contact with the diaphragm
What is bile?
A greenish-yellow alkaline liquid synthesized by the liver and stored in the gallbladder
What is bile secreted by?
Hepatocytes
What is the principal pigment in bile?
Bilirubin
Where is bile released and via what duct?
Released into the duodenum via the common bile duct
What is the function of the common bile duct?
Emulsifies fats into droplets, making digestion easier by increasing the surface area
What is bilirubin?
Yellow pigment produced by the breakdown of the heme group from the hemoglobin molecule
How is bilirubin excreted from the body?
The liver absorbs bilirubin from the blood, secretes it into bile, which is released into the small intestines and further broken down in the large intestine and excreted as feces
What role do hepatocytes play in the excretion of drugs?
Actively and passively excrete them into the bile, which is released into the duodenum. The drug is either reabsorbed or eliminated in the poopoo
How is vitam D synthesized?
- Hepatocytes in the liver make and secrete vitamin D precursor
- Precursor is transported to the skin
- Sun’s UV rays convert vitamin precursor to second precursor
- Second precursor is transported to the liver and kidneys and converted to vitamin D
What is the role of vitamin D in the small intestine?
Transfer calcium from food into the blood
What is the function of the gallbladder?
It stores and concentrates bile, releasing it into the duodenum during digestion.
What does the biliary tree connect?
It connects the liver, gallbladder, and pancreas to the duodenum.
What is the main function of the small intestine?
It is the main digestion and absorption site for water, proteins, carbohydrates (sugars), and lipids (fats).
What are the three sections of the small intestine?
Duodenum, jejunum, and ileum.
What is the main function of the large intestine?
Absorb water and salts, and eliminate waste.
How does the large intestine move waste?
Specialized types of peristaltic contractions occur 3-4 times a day, moving fecal matter into the sigmoid colon and rectum.
What is peritoneum and what are its main functions?
It is a continuous serous membrane, lining the walls and contents of the abdomen.
Its functions are, preventing friction between abdominal organs, holding organs in place, carries vessels, and prevents the spread of infection.
What are the two types of peritoneum?
- Parietal peritoneum: covers the abdominal wall
- Visceral peritoneum: covers the abdominal organs
What is the peritoneal cavity?
A potential space between the parietal and visceral peritoneum that contains lubricating fluid.
What is chemical digestion?
The breakdown of nutrients (carbohydrates, proteins, and lipids) into smaller units that can be absorbed into the body.
Where does the majority of chemical digestion take place?
In the small intestine
What is absorption?
The movement of digested nutrients across the intestinal wall and into the bloodstream, allowing the body to utilize them.
What is carbohydrate digestion?
The process of breaking down complex carbohydrates (polysaccharides and disaccharides) into monomeric units (monosaccharides, glucose, fructose, and galactose) in order to be absorbed into the bloodstream.
What is protein digestion?
Proteins from food get broken down into single amino acid molecules in order to be absorped into the bloodstream.
What are amino acids used for in the body?
They are used to build and repair cells, and are involved in the producrion of enzymes, neurotransmitters, DNA, and RNA.
What is lipid digestion?
Triglycerides must be broken down into smaller monoglycerides and fatty acid molecules in order to be absorbed into the lacteals (lymph vessels) and transported into the bloodstream.
What is carbohydrate absorption?
Monosaccharides are transported from the small intestine into the bloodstream, sing faciliated duffusuion or active transport.
What is protein absorption?
Amino acids can be absorbed as di- and tri- peptides, which are cotransported from the intestinal lumen to the surrounding cells with hydrogen ions.
What is lipid absorption?
The process where monoglycerides and free fatty acids combine with bile salts and lecithin to form micelles, allowing then to be absorbed into intestinal cells.
What is water and electrolyte (ion) absorption?
The process where water and electrolytes (such as sodium) are absorbed from the gastrointestinal tract into the bloodstream, through osmosis. Sodium creates a concetration gradient that helps pull water into the cells.
What are the two categories that vitamins fall into?
Fat-soluble vitamins (A, D, E, and K) and water-soluble vitamins (B complex, and C)
How are the fat-soluble vitamins absorbed?
They are transported to the brush border of the absorptive cells by micelles, where they are then absorbed by diffusion.
How are the water-soluble vitamins absorbed?
They are absorbed directly through simple diffusion.
How is vitamin B12 absorbed?
By active transport after being coupled with an intrinsic factor produced by the stomach.
What activities are coordinated and controlled by neural and hormonal mechanisms?
Digestive activities, such as salivation, gastric juice secretion, and gastric emptying.
What is the enteric nervous system (ENS)?
A network of nerve cells in the digestive system are responsible for neural regulation of the muscles and exocrine glands of the gastrointestinal tract, controlling digestion.
What are enteroendocrine cells?
They are located throughout the mucosa of the stomach through to the colon and are responsible for hormonal regulation of the gastrointestinal tract.
