BN Ch.26 The Digestive System Flashcards
1
Q
On a chart, trace the digestive pathway, naming major organs of the gastrointestinal (GI) system and the function of each.
A
- Mouth
- Chews and mixes food with saliva
- Pharynx
- Directs food from mouth to esophagus
- Salivary glands
- Secrete saliva
- Epiglottis
- Protects airways during swallowing
- Trachea
- Allows air to pass to and from lungs
- Esophagus
- Passes food from the mouth to the stomach
- Esophageal sphincters
- Allow the passage from mouth to esophagus and from esophagus to stomach, prevent back flow from stomach to esophagus and from esophagus to mouth
- Diaphragm
- Separates the abdomen from the thoracic activity
- Stomach
- Churns, mixes, and grinds food to a liquid mass
- Adds acid, enzymes, and fluid pyloric sphincter
- Allows passage from stomach to small intestine
- Prevents back flow from small intestine
- Liver
- Manufactures bile salts, detergent
- Like substances, to help digest fats
- Gallbladder
- Stores bile until needed
- Bile Duct
- Conducts bile from the gallbladder to the small intestine
- Appendix
- House bacteria and lymph cells
- Small intestine
- Secretes enzymes that digest all energy
- Yielding nutrients to smaller nutrient particles
- Cells of wall absorb nutrients into blood and lymph ileocecal valve (sphincter)
- Allows passage from small to large intestine prevents back flow from large intestine
- Pancreas
- Manufactures enzymes to digest all energy
- Yielding nutrients and releases bicarbonate to neutralize acid chyme that enters the small intestine
- Pancreatic duct
- Conducts pancreatic juice from the pancreas to the small intestine
- Large intestine
- Absorbs water and minerals; passes waste along with water to rectum
- Rectum
- Stores water prior to elimination anus
- Holds rectum closed; opens to allow elimination
2
Q
Define the following terms and processes: mastication, deglutition, and peristalsis.
A
- Mastication
- Their chief function is to break food into smaller particles, accomplished through mastication, chewing.
- Deglutition
- Voluntary movement of the tongue begins the swallowing process ( deglutition ), by lifting and pushing the bolus of food, mixed with saliva, into the pharynx, the next portion of the digestive tube.
- The upper surface of the tongue appears rough because of visible indentations ( fissures ) and projections ( papillae ).
- The taste buds are microscopic nipple-like projections located on the sides of the papillae.
- They are specialized nerve endings allowing detection of various flavors, such as salty, bitter, sweet, sour, alkaline, and metallic.
- The ability to taste food also depends on the sense of smell.
- Peristalsis
- The smooth (involuntary) muscles pass food through the entire GI tube by waves of contractions, peristalsis , an alternating muscular relaxation and contraction, without which digestion cannot occur.
3
Q
Explain the actions of hydrochloric acid (HCl), gastrin, intrinsic factor, cholecystokinin, and pancreatic juice in the process of digestion.
A
- Hydrochloric acid (HCl)
- Destroys microorganisms
- Gastrin
- Stimulates secretion of gastric acid (HCl) and pepsin
- Intrinsic factor
- Needed for absorption of vitamin B 12 , needed for development of RBCs (also requires folate)
- Cholecystokinin
- Activates gallbladder to release bile
- Pancreatic juice
- Breaks fats into tiny droplets (emulsification)
4
Q
Explain two functions of the pancreas and gallbladder as they relate to digestion.
A
- Gallbladder
- Its major functions are storage and release of bile, as needed in the small intestine for fat emulsification.
- It also concentrates bile by absorbing water and salts.
- Pancreas
- As an endocrine gland, it secretes the hormones insulin, glucagon, and somatostatin into the bloodstream, to help regulate blood sugar levels.
- Its exocrine function is to produce pancreatic juice, which is necessary for life, because it is vital in digestion.
- It is produced by the acinar cells.
- The acinar cells secrete three main enzymes that assist in digestion of specific nutrients:
- Pancreatic amylase:
- Starch/Carbohydrates
- Trypsin:
- Protein
- Pancreatic lipase:
- Fats, Lipids (into triglycerides)
- Pancreatic amylase:
5
Q
Describe the functions of the liver related to digestion.
A
- Only the brain is capable of more functions than the liver.
- Some of the liver’s major functions include the following:
- Secretion of bile Absorption of bilirubin after destruction of old red blood cells (RBCs)
- Detoxification of blood (removal of toxins or poisons)
- Storage of fat-soluble vitamins (A, D, E, K)
- Formation of vitamin A and some nonessential amino acids
- Storage of vitamin B complex and iron
- Formation of plasma proteins (albumin, prothrombin, globulins)
- Synthesis of urea, a waste product from protein anabolism
- Storage of glucose as glycogen (helps regulate glucose levels)
- Synthesis of clotting factors (fibrinogen; prothrombin; factors V, VII, IX, X)
- Formation of triglycerides and cholesterol
- Secretion of heparin (anticoagulant)
- Synthesis of immunoglobulins
- Breaking down of fats (lipids)
- Metabolism of carbohydrates; storage of fats and carbohydrates
- Regulation of amino acids
- Production of body heat
- Storage of minerals
- Production of lymph
6
Q
Describe the physiology of digestion and absorption, including how carbohydrates, fats, and proteins are broken down; describe absorption in the small intestine.
A
- Mechanical digestion
- is the physical breakdown of food caused by chewing and the movement of food in the digestive tract.
- Breaking food into smaller pieces exposes more food surface area to the effects of enzymes, acids, and other chemicals.
- Chemical digestion
- is the breakdown of chemical bonds in food, with the addition of enzymes, acids, and water.
- Some digestive processes begin in the mouth, pharynx, and stomach, but most digestion occurs in the duodenum.
- Chief cells .
- Pepsinogen is a precursor of pepsin, the enzyme needed to break down proteins.
- Gastric lipase breaks down triglycerides in butterfat (found in milk and dairy products).
- Secrete pepsinogen and gastric lipase
- Parietal cells
- Secrete hydrochloric acid (HCl), which functions to activate pepsinogen and kill most stomach microorganisms.
- When activated, pepsinogen changes into the enzyme pepsin, which begins to break down proteins.
- Digestion of starches into glucose molecules starts in the mouth, but primarily takes place in the small intestine by the action of specific enzymes secreted from the pancreatic amylase: starch/carbohydrates
- Absorption in the Small Intestine
- Absorption of approximately 85% of nutrients used by the body occurs across the villi , small finger-like projections on the mucosa of the small intestine, into the capillary network.
- To increase surface area, villi contain microvilli, microscopic folds on the surface of epithelial cells in the cell membrane. (Unfolded and straightened out, one person’s villi and microvilli could completely cover more than 2,000 square feet, half a basketball court.)
- Villi wave to keep food molecules thoroughly mixed with digestive juices.
- Amino acids are absorbed in the duodenum and jejunum;
- Most fats are absorbed in the jejunum.
- Because villi are so important in absorption, they are heavily supplied with capillaries, which carry nutrients, via hepatic portal circulation, to the liver for further processing.
- Active and passive transport are the means by which nutrients are absorbed into the circulation and then to the body’s cells.
- Absorption of nutrients into the bloodstream occurs via the small intestine.
- The body cannot use these food materials, however, until the bloodstream delivers them to the cells by transporting the particles across each cell’s membrane.
7
Q
Identify and describe two major categories of metabolism.
A
- Catabolism (destruction, catabolic phase)
- Is the breakdown of larger molecules into smaller ones, releasing energy.
- Cellular respiration is a series of catabolic reactions.
- Catabolism (destructive metabolism): breaking down foods into useable substances (generates heat, carbon dioxide, water, and ATP)
- The end products of catabolism resulting from cellular respiration are:
- Carbon dioxide
- Water
- Energy
- Anabolism (construction, anabolic phase)
- Is the synthesis of simpler substances into new, organized substances to be used by body cells.
- Anabolism (constructive metabolism): using products of catabolism to build and repair body cells and maintain life
- Examples of anabolism include synthesis of glycogen, triglycerides, or proteins.
8
Q
Explain how the large intestine changes its contents into fecal material.
A
- Whatever nutrients are not reabsorbed and sent to the portal (liver) circulation are eliminated as solid intestinal wastes ( defecation , bowel movement, egestion ).
- After water reabsorption, a plant fiber, cellulose, other undigested material, living and dead bacteria, and mucus remain.
- These mass together and pass into the rectum as solid or semisolid waste or feces (excrement, excreta), where they stimulate sensory nerve endings, causing a sensation of accumulating bulk and initiate the defecation (evacuation) reflex.
- Peristaltic waves push feces against the anal muscle as a signal for emptying the rectum (the defecation reflex ), and parasympathetic-controlled nervous activity causes strong contractions.
- The internal sphincter relaxes and pressure from peristalsis, along with pressure consciously exerted by the diaphragm and abdominal muscles, brings about defecation.
- To expel feces, the external anal sphincter, a skeletal muscle, relaxes voluntarily. If the defecation reflex is ignored routinely, the impulse tends to die and constipation often occurs.
- This can become life threatening if it results in bowel obstruction.
9
Q
List the effects of aging on the digestive system.
A
- Saliva production decreases
- Decreased Gag Reflex
- Bony structures decrease around the mouth
- Loss of teeth
- Taste decreases, especially sweet and sour tastes.
- Sense of smell decreases
- Gastric mucosa atrophies and secretions such as HCl, intrinsic factor, and enzymes may decrease
- Food stays in stomach longer
- Peristalsis decreases
- Reduced secretion of digestive juices
- Ignoring the need to defecate
- Occurrence of gallstones may increase
- Lower tolerance to some foods
- Ignoring hunger or thirst
- Decreases in absorptive surfaces in intestines, due to decreased villi height and decreased intestinal motility
- Fat tissue replaces muscle tissue
- Reduced exercise; poor diet
- Caloric needs decrease
- Physical inactivity
- Difficulty swallowing (may be due to disease process such as stroke, Huntington disease, etc.)
- Dementia—may forget to eat or may repeats meals
- Financial factors—cannot afford nutritious diet
- Unable to properly prepare foods
- Anal sphincter insufficiency
10
Q
The system of passageways for the transport of bile from the liver to the gallbladder to the intestine is known as __________ apparatus.
A
Biliary
11
Q
_________ digestion is the breakdown of
chemical bonds in food with the addition of
enzymes, acids, and water.
A
Chemical
12
Q
__________cells in the stomach mucosa secrete pepsinogen (breakdown proteins) and gastric lipase.
A
Chief
13
Q
A small, finger-like projection of the cecum is the vermiform _________.
A
Appendix
14
Q
In the stomach, all foods mix with gastric
juices and churn until they are in a
semiliquid form called __________.
A
Chyme
15
Q
The contraction of this organ results in continuation of the act of swallowing and pushes the food into the esophagus.
A
Pharynx
