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Learning Objectives for Chapter 23
THE DIGESTIVE SYSTEM
1. Summarize the digestive system by: Naming the gastrointestinal tract organs and accessory digestive organs
- GI tract: mouth, pharynx, esophagus, stomach, small intestine, large intestine.
- Accessory Digestive organs: teeth, tongue, salivary glands, liver, gallbladder, pancreas.
1. Summarize the digestive system by: Stating its functions
- Ingestion (foods & liquids).
- Secretion (water, acid, buffers and enzymes) into lumen
- Mixing and propulsion
1. Summarize the digestive system by: Describing its basic processes
- 1.Ingestion: Taking foods and liquids into the mouth.
- 2.Secretion: Cells within the GI tract and accessory digestive organs secret approximately 7 liters of water, acid, buffers and enzymes into the lumen of the tract.
- 3.Mixing and propulsion: of food and secretions or motility of the GI tract is achieved by the alternating contractions and relaxations of smooth muscle in the walls of the GI tract.
- 4.Digestion: involves the breaking down of ingested food into smaller molecules mechanically and chemically.
- 5.Absorption: the entrance of ingested and secreted fluids, ions and digestion products into the epithelial cells lining the lumen of the GI tract.
- 6.Defecation: Elimination of wastes, indigestible substances, bacteria, sloughed off cells from the lining of the GI tract, and unabsorbed digested materials by way of the anus in the form of feces.
1. Summarize the digestive system by: Distinguish between mechanical digestion and chemical digestion
Mechanical is grinding or cutting food involves teeth while chemical digestion is where large carbohydrates,lipids are broken down into smaller molecules.
2. State the locations and functions of the four layers of the GI tract wall and describe the histology of the GI tract mucosa.
- The Mucosa is the innermost tissue layer that is in contact with the Lumen. All nutrients must cross the mucosa to enter the blood.
- The submucosa is next to the mucosa and it a connective tissue layer containing blood vessels, lymph vessels, and nerves. Components of food that are absorbed across the mucosa enter the blood and lymph vessels of the submucosa.
- The Muscularis is the third layer of the GI tract tissue and it is responsible for movement.
- The Serosa is the the outermost layer of the GI tract wall. This layer is a thin connective tissue layer that surrounds and protects the other three layers and attaches the digestive system to the walls of the body cavities.
3. State the functions of the peritoneum:
the cavity in which the abdominal organs in and contain blood & lymphatic vessels and nerves that supply the abdominal organs.
3.Describe the parietal peritoneum:
Parietal peritoneun: Lines the wall of abdominal pelvic cavity.
3.Describe the visceral peritoneum:
Visceral peritoneum: covers some of the organs in the cavity and in their serosa.
3.Describe the greater omentum:
Greater Omentum: double sheet that folds back upon its self giving a total of 4 layers that loosely covers the transverse colon and small intestine
3.Describe the lesser omentum:
Lesser Omentum: Arises as two folds in the serosa of the stomach and duodenum that connects the medial curve of the stomach with the liver.
3.Describe the mesentery:
- Mesentery: A fan-shaped fold of the Peritoneum that holds the small intestines to the posterior abdominal wall, the meocolon where the large intestines is similarly secures to the posterior abdominal wall. The liver is bound to the anterior abdominal wall by the falciform ligament.
4. Define peritonitis.
Inflammation of peritoneum.
5. Summarize the mouth by: Stating the source and describing the functions of saliva
- Source: Salivary glands (Parotid, submandibular & sublingual).
- Function: mosten soft tissues of the mouth; dissolves and lubricates food for easy mastication.
5. Summarize the mouth by: Describing the pulp cavity, pulp, and root canals
- Pulp Cavity: within the crown, enclosed by dentin filled with pulp.
- Pulp: connective tissue, blood vessels, nerves and lymphatic vessels.
- Root Canals: extensions from pulp cavity that run through the root of the tooth; blood supply, nerves and lymphatic vessels enter here at the base of the tooth.
5. Summarize the mouth by: Describing mastication
Or chewing is the mechanical digestion performed in the mouth in which food is ground by teeth, manipulated by the tongue and moistend with saliva.
6. Define mumps.
- Inflammation of the Parotid glands.
- Caused by Paramyxovirus; symptoms of fever, pain in throat (swallowing), facial swelling.
7. Define and state the cause of dental caries (cavities).
also known as tooth decay; bacteria act on sugar to produce acid that gradually de-mineralizes enamel and dentin.
8. Define periodontal disease and relate periodontal disease to tooth loss.
Is the inflammation and degeneration of the gingivae, alveolar bone, periodontal ligament and cementum. This can lead to enlargement and softening of gum tissue, deterioration of the alveolar bone & cause teeth to loosen and gums to recede as in Pyorrhea.
9. Describe deglutition:
Deglutition: or swallowing of an ingested bolus.
9. Describe peristalsis.
Peristalsis: sequential contractions of the GI tract (pinching and shortening) to move bolus' of ingested matter from the pharynx to the stomach.
10. Define and state the cause of gastroesophageal reflux disease and its symptom, heartburn.
Contractions of the stomach muscularis expel gas from the stomach upward into the esophagus with so much force that sometimes gastric juice can be forced into the esophagus. The caustic hydrochloric acid in gastric juice can irritate the mucosa of the esophagus. This is known as Heartburn and is so named because the discomfort appears to be located at the heart. Esophageal ulcers may result. An even more threatening outcome is esophageal cancer.
11. Summarize the stomach by: Stating the collective name for the secretions of the gastric glands
11. Summarize the stomach by: Describing chyme
The soupy liquid mixture of food and gastric juices.
11. Summarize the stomach by: Describing the role of the stomach in mechanical digestion, chemical digestion, and absorption
- Mechanical digestion in the stomach occurs via mixing waves (produced by Muscularis) which macerate food, mix it with secretions of gastric glands and reduce it to chyme.
- Chemical digestion in the stomach is achieved the secretions of by HCl, Pepsin (pepsinogen), gastric lipase and intrinsic factor.
- Absorption in the stomach is limited to a small quantity of water, ions, short-chain fatty acids and some drugs.
11. Summarize the stomach by: Stating the digestive system organ that secretes hydrochloric acid and the functions of the secretion:
- Hydrochloric acid: secreted by parietal cells.
- Function are to kill microbes, convert pepsinogen to pepsin and denature protein.
11. Summarize the stomach by: Stating the digestive system organ that secretes pepsin and the functions of the secretion.
Pesin is converted from pepsinogen which is secreted by chief cells. Function is to break down proteins into peptides.
11. Summarize the stomach by: Stating the digestive system organ that secretes and intrinsic factor and the functions of the secretion.
Intrinsic factor is secreted by parietal cells. Function is to help the absorption of vit B 12 ( needed for erythropoiesis).
11. Summarize the stomach by: Explaining why pepsin does not digest proteins in the stomach wall
Pepsin is secreted by the chief cells in an inactive form called pepsinogen that becomes activated only after contact with HCl from Gastric juices secreted into the lumen of stomach. The epithelial cells that line the stomach are protected from the acidic enviroment by an alkaline layer of mucus produced by both the surface mucous and mucous neck cells.
12. State the digestive system function of bile.
Emulsification of large dietary lipids into small fat globules, this increases the surface area for pancreatic lipase for digestion of triglycerides and facilitation of lipid absorption after digestion.
13. Define hepatitis.
Inflammation of the liver, caused by infectious or toxic agents and characterized by jaundice, fever, liver enlargement, and abdominal pain.
14. Define gallstones.
Calculi, or crystalline concentration of bile components such as lecithin or excessive cholesterol formed within the gallbladder.
15. Define cirrhosis.
Final phase of chronic liver disease. A chronic degenerative disease of the liver. Scarring of the liver characterized by poor liver function.
16. Explain how small intestine absorption is assisted by circular folds (plicae circulares), villi, and microvilli:
Circular folds, Villi, and Microvilli allow for increased Surface area.
Describe mechanical digestion in the small intestine:
peristalsis moves food in the process of digestion along the intestine, while segmentation breaks up larger molecules (circular muscle pinching) and continually mixes contents with digestive juices (like a washing machine agitator)
17. The five components of pancreatic juice are:
- Sodium Bicarbonate.
- Pancreatic Amylase.
17. For each of the following state the digestive system organ from which it is secreted, its digestive system function, and in which digestive system organ it functions: Sodium bicarbonate
released by pancreas to help neutralize acid in the stomach and also regulate pH in the small intestine.
17. For each of the following state the digestive system organ from which it is secreted, its digestive system function, and in which digestive system organ it functions: Pancreatic amylase
Secreted from the pancreas, functions as a starch-digesting enzyme in the small intestine
17. For each of the following state the digestive system organ from which it is secreted, its digestive system function, and in which digestive system organ it functions: Pancreatic lipase
- Secreted: by pancreas.
- Function: breaks down tryglycerides into fatty acids and
- monoglycerides in the small intestines.
17. For each of the following state the digestive system organ from which it is secreted, its digestive system function, and in which digestive system organ it functions: Trypsin
secreted by pancreas, breaks down proteins into peptides in the stomach.
17. For each of the following state the digestive system organ from which it is secreted, its digestive system function, and in which digestive system organ it functions: Chymotrypsin
secreted by pancreas, breaks down proteins into peptides in the stomach.
17. For each of the following state the digestive system organ from which it is secreted, its digestive system function, and in which digestive system organ it functions: Brush border enzymes (enterokinase):
activates trypsinogen released by the pancreas into an active trypsin
18. Summarize chemical digestion and absorption in the GI tract by: Stating where in the GI tract the digestion of carbohydrates, proteins, and lipids begins
- carbohydrates: starts in the mouth (Salivary amylase; starches to simpler sugars).
- proteins: starts in the stomach (Pepsin; Proteins to Peptides).
- lipids: start in the mouth. (lingual lipase; triglycerides & other fats to fatty acids and diglycerides).
18. Summarize chemical digestion and absorption in the GI tract by: Stating the end products of carbohydrate, protein, and lipid digestion
- Carbohydrates: glucose, fructose & galactose.
- Proteins: Peptides.
- Lipids: Amino acids & Fatty Acids.
18. Summarize chemical digestion and absorption in the GI tract by: Stating where in the GI tract end products of carbohydrate, protein, and lipid digestion are absorbed
All end products are absorbed in the small intestine.
18. Summarize chemical digestion and absorption in the GI tract by: Describing how end products of carbohydrate, protein, and lipid digestion, and water, are absorbed
- carbohydrates: facilitated diffusion
- proteins: active transport.
- lipids: simple diffusion.
19. Define appendicitis.
Inflammation of the appendix vermiform.
20. Describe digestion and absorption in the large intestine:
- Mechanical: Haustral churning and peristalsis. Formation of feces for defecation.
- Absorption of some water, ions and vitamins occurs here.
20. Describe the defecation reflex.
- The presence of fecal matter in rectum causes distention of rectal wall.
- This stretching stimulates receptors in the wall and sends messages to spinal cord (sacral).
- A motor impulse from the spinal cord is generated to the descending colon, sigmoid colon, rectum, anus via parasympathetic pathway, results in contraction of rectal muscles.
- Results in shortening of rectum which increases pressure in rectum.
- This pressure with parasympathetic stimulation opens internal anal spincter which causes the urge to defecate.
21. Describe diarrhea:
Diarrhea: a person is said to have diarrhea when he has three or more loose liquid bowel movement in one day. Caused by chyme moving too quickly through the large intestine and not enough water is absorbed from the chyme, the result is watery stools.
21. Describe Constipation:
Constipation: When a person has infrequent and hard to pass bowel movement, is called constipated or has constipation. Caused by chyme moving too slowly through the large intestine, too much water is absorbed into the organ, the feces to become more firm and difficult to pass.
22. Define obesity, why it is hazardous to health, and summarize factors that contribute to obesity.
Obesity is defined as a body weight that is 20% over a standard body weight for your height and sex. (Caused by too much adipose tissue). As far as health hazards are concerned, obesity has been shown to be linked to heart disease, high blood pressure, diabetes, osteoarthritis, gallbladder disease/gallstones, breathing problems (apnea, asthma)
23. Summarize nutrition by: Defining nutrient
Body cells use Nutrients in food for growth, maintenance, and repair.
23. Summarize nutrition by: Stating the main types of nutrients
Nutrients include water, carbs, lipids, proteins, minerals and vitamins.
23. Summarize nutrition by: Stating the general nutritional functions of water, carbohydrates, lipids, proteins, minerals, and vitamins
- water: provides the medium in which most metabolic reactions occur.
- carbohydrates: provide energy for metabolic reactions and serve as building blocks to make body structures. lipids: provide energy for metabolic reactions and serve as building blocks to make body structures.
- proteins: provide energy for metabolic reactions and serve as building blocks to make body structures.
- minerals: inorganic elements that help regulate enzymatic reactions.
- vitamins: organic nutrients required in small amounts to maintain growth and normal metabolism.
23. Summarize nutrition by: Stating the current recommended distribution of calories in our diet
50-60% carbs, less than 15% simple sugars, less than 30% from fats (no more than 10% as saturated fats), 12-15% proteins
23. Summarize nutrition by: Describing the guidelines for healthy eating
- 1) Eat a variety of food
- 2) maintain a healthy weight
- 3) Eat foods low in fat and cholesterol
- 4) Eat vegetables, fruits, and grain products
- 5) Use sugars in moderation
24.Mouth (oral cavity)
Where chewing takes place to get food into smaller pieces, also saliva is mixed to begin breakdown process.
Functions to keep food between teeth.
Functions to keep food between teeth.
24. Hard palate
allows food to be chewed while breathing continues
24. Soft palate
closes off nasal passages during swallowing
tastes and detects temperature of food, manipulates food under teeth for chewing
containtaste buds, receptors for gustation (taste). some lack taste buds but they conatin receptors for touch to better enable manipulation of food by the tongue during mastication.
24. Salivary glands
- release secretion of saliva
Protects the tooth so teeth can tear and cut food into smaller pieces.
24. Pulp cavity
provides nourishment to the tooth
attaches root to periodontal ligament
assists in the cutting/shredding of food
or canines tear and shred food
(bicuspids) assist in grinding and chewing of food
grind food to prepare it for swallowing
helps propel food into esophagus, then to stomach
secretes mucus, transports food to stomach
serves as mixing chamber/holding reservoir after food is ingested, before intestines digest/absorb
24. Pyloric sphincter
Opens to permit passage of chyme into duodenum.
fold like stuctures that increase surface area for digestion to take place.
helps in creating mixing waves
produces pancreatic juice.
24. Pancreatic duct
drains pancreatic juice into duodenum
24. Common hepatic duct
- formed from right and left hepatic ducts
- joins cystic duct from gall bladder to form common bile duct
stores bile; releases bile into duodenum via cystic duct-->common bile duct.
24. Cystic duct
leaves from gall bladder to join common hepatic duct to form common bile duct.
secretion of digestive juices and absorption of digestive end products
24. Epithelium of the mucosa of the SMALL INTESTINE
made up of simple columnar epithelial cells that include "absorptive cells" that digest and absorb nutrients in chyme, "goblet cells" that secrete mucus, form intestinal glands of the intestine that secrete intestinal juice, Paneth cells that secrete lysozyme and are capable of phagocytosis (for microbial regulation), and endocrine cells (S cells and CCK cells)
24. Lamina propria
inner lumen of the villi of the small intestine contains Peyer's patches (lymphatic nodules) to protect against food pathogens
24. Muscularis mucosae
secretes mucus which helps move materials through colon
increases surface area of epithelium available for absorption/digestion
areolar connective tissue; binds mucosa to muscularis
24. Circular folds
(plicae circulares) cause chyme to spiral and expose more of the mucosa to the nutrients
mixes ingested food with gastric juices to aid in digestion
- Outer most layer of the stomach & small intestine.
- Secretes serous fluid to reduce friction of organs within their cavities
24. Large intestine
completion of absorption, production of certain vitamins, formation/expulsion of feces