Ch. 14 Digestive System & Nutrition
What are the two major functions of the small intestine?
1. Digestion 2. Absorption
What are the 3 regions of the small intestine?
1. Duodenum 2. Jejunum 3. Ileum
what are the three functions of the stomach?
1. Food Storage 2. Digestion 3. Regulation of delivery
Five basic processes accomplish digestive system
1. Mechanical processing and movement 2. Secretion 3. Digestion 4. Absorption 5. Elimination
four main ingredients Saliva contains?
1. Mucin 2. Salivary amylase 3. Bicarbonate 4. Lysozyme
4 layers of the GI tract?
1. Mucosa 2. Submucosa 3. Muscularis 4. Serosa
Enzymes in Protein Digestion
1. Pepsin 2. Trypsin 3. Chymotrypsin 4. Carboxypeptidase 5. Intestinal enzymes
Enzyme in Carbohydrate Digestion
1. Salivary amylase 2. Pancreatic amylase 3. Intestine enzymes
What are the four subdivide sections of the colon?
1. ascending colon 2. Transverse colon 3. descending colon 4. Short Sigmoid colon
Duodenum
10 inches long and its where most of digestion takes its place
How long does it take the stomach to empty completely after a meal?
2 to 6 hours
Feces contain about how many % of bacteria weight?
30%
Esophagus
A muscular tube consisting of both skeletal and smooth muscle that connects the pharynx to the stomach. Lining produce lubricating mucus helps moves food from pharynx to stomach easily.
External anal sphincter
A ring of skeletal muscle under our conscious control. Can prevent defecation by voluntarily contracting.
Appendix
A small fingerlike pouch, extends from the cecum. No known digestive function.
Large intestine
Absorbs the last of the remaining water, ions, and nutrients and stores the now nearly solid waste material until it can be eliminated.
how is water-soluble vitamins absorbed?
Active transport or diffusion through channels or pores
What can be absorb through the stomach?
Alcohol and aspirin, which are small lipid soluble substances that can cross the mucus barrier and absorbed into the bloodstream directly from the stomach.
Carbohydrates
Body's main sources of energy. 45 to 65% recommend of our calorie intake. Simple or complex.
What slows stomach peristalsis?
Chyme with high acid or fat content stimulates the release of hormones slowing peristalsis, giving small intestine more time to absorb the nutrients.
Chylomicrons
Clusters of triglycerides coated with proteins to form water-soluble droplets. Released from the cell by exocytosis. Enter more permeable lacteals and travels in the lymph vessels until the lymph is returned to the venous blood vessels near the heart.
Mucosa structure
Contains large folds covered with microscopic projections called villi that are covered with microvilli
periodontitis
Decay that inflames the periodontal membrane.
Two pancreatic Ducts
Deliver these secretions to the duodenum, where they facilitate the process of digestion.
Small intestine
Digests proteins, fats, and carbohydrates. Absorbs most nutrients and water, secretes digestive hormones and enzymes
how is fat-soluble vitamin absorbed?
Dissolved in the micelles and are absorbed by diffusion across the lipid membrane of the mucosal cell layer.
Anus
Expels undigested material
Pancreatic amylase
In Pancreas, active in small intestine, substance digested polysaccharides, and breakdown disaccharides.
lipase
In pancreas, active in small intestine, substance digested are triglycerides, and breakdown free fatty acids and monoglyceride.
Salivary amylase
In salivary glands, active in the mouth, substance digested polysaccharides and breaks down disaccharides
Intestine enzymes
In small intestine, active in small intestine, substance digested disaccharides and breakdowns monosaccharides (glucose).
Pepsin
In stomach, active in stomach, substance digested is proteins, and breakdown peptides
Primary pathway where is alcohol is absorbed?
Intestine
In the small intestine where does digestion products primarily absorbed?
Jejunum and ileum
Enzyme in Lipid Digestion
Lipase
Cirrhosis
Long-term exposure, such as prolong alcohol abuse, can destroy enough cells to permanently impair liver function.
Digestion
More of a storage bag. Chemical digestion of proteins begins because exocrine glands in the stomach add strong acid protein-degrading enzymes to stomach contents. Acids kills most bacteria. Muscle contractions mix these secretions with food, mechanically breaking apart food particles.
Does the stomach absorb nutrients and why?
No, it does not. It lacks the required cellular transporting mechanism and because its inner lining is coated with mucus.
How is water absorbed in the small intestine?
Osmosis, along with all of the nutrients being absorbed.
Rectum
Passageway for feces
cholecystokinin (CCK)
Presence of fat and protein stimulates the release of CCK, which signals the pancreas to secrete more digestive enzymes.
Liver
Produces bile, stores fat-soluble vitamins A, D, E, and K and iron, stores glucose as glycogen after meal, and converts glycogen to glucose between meals. Manufactures plasma proteins, such as albumin and fibrinogen, from amino acids. Synthesizes and stores some lipids. Inactivates many chemicals, including alcohol, hormones, drugs, and poisons. Converts ammonia, a toxic waste product of metabolism, into less toxic urea. Destroys worn-out RBCs.
Peristalsis
Propels food forward. Begins when a lump of food (bolus) stretches a portion of the GI tract, causing the smooth muscles in front of the bolus to relax and the muscle behind it to contract pushing food forward, stretching the next part of the tube & causing muscle relaxation in front & contraction behind.
Pancreatic digestive enzymes include:
Proteases, an enzyme that digest proteins, such as trypsin, chymotrypsin, and carboxypeptidase. Pancreatic Amylase, which continues the digestion of carbohydrates only partially accomplished by salivary amylase. Lipase, a lipid digesting enzyme.
Salivary Glands
Saliva moistens food, bicarbonate maintains pH, amylase digest starch, and lysozyme inhibits bacteria.
Pancreas Exocrine Role
Secretes and produce Digestive enzymes, Sodium bicarbonate (NaHCO3), and Two Pancreatic Ducts.
Pancreas
Secretes digestive enzymes into small intestine, secretes bicarbonate into small intestine (duodenum) to neutralize stomach acid via ducts
Pancreas Endocrine Gland Role
Secretes hormones that regulates blood glucose levels
Where is food digested?
Small intestine
which minerals are electrically charged and not lipid soluble?
Sodium, potassium, calcium, phosphate, sulfate, and magnesium. These are either actively transported or absorbed by diffusion via specific transport proteins, pores, or channels.
Gallbladder
Stores and concentrates bile until needed, delivers bile to duodenum via the common bile duct. Concentrates bile by removing most of the water and stores it until after a meal, when it is secreted into the small intestine via bile duct, which joins the pancreatic duct.
Stomach
Stores and mixes food, begins chemical digestion of protein by enzymes and acid, regulates delivery to the small intestine
Where does GI blood pass through after the liver?
The general circulation via two hepatic veins
Muscularis
Third layer of the GI tract tissue, responsible for motility, or movement. Consist of two or three sublayers of smooth muscles. Fibers of the inner sublayer are oriented in a circular fashion around the lumen. Outer sublayer are arranged lengthwise, parallel to the long axis of the digestive tube. Stomach is the exception, which is diagonal (oblique) sublayer of muscle inside the other two.
Secretin
Triggered by acid in chime releases secretin, which stimulates the pancreas to secrete water and bicarbonate to neutralize acid.
What by-product released by bacteria is useful to us?
Vitamin K, which is important for blood clotting.
hiatal hernia
a condition in which part of the stomach protrudes upward into the chest through an opening (hiatus) in the diaphragm muscle.
Gastrin
a hormone secreted in the gastric glands into the bloodstream. stretching and the presence of protein stimulates the stomach to release gastrin hormone, which triggers the release of more gastric juice.
pepsinogen
a large precursor molecule that becomes a protein-digesting enzyme called pepsin once it is exposed to acid in the stomach.
Cecum
a pouch where the large intestine begins. Receives chyme from the small intestine
how much chime does each contraction propels?
a tablespoon
Hepatic portal system
all of the nutrient-rich venous blood leaves the GI tract goes directly to the liver via the hepatic portal system before entering the general circulation. Smaller veins join to become the hepatic portal vein, which enters the liver.
digestive system
all organs that share the common function of getting nutrients into the body. GI tract "hollow organs": mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum, and anus.
Peptic ulcer
an open sore sometimes bleeding. Occurs in esophagus and upper part of the small intestine
appendicitis
appendix infected or inflamed.
How id the anus normally kept closed?
by Tonic contraction of the internal anal sphincter, a ring of smooth muscle.
lacteal
capillaries and a small lymph vessel which transport nutrients to larger blood vessels and lymph vessels. Located at the end of each villus.
colon
continued from the cecum.
Bile salt
derived from cholesterol, emulsify lipids in the small intestine, that is, they break them into smaller and smaller droplets. Droplets are small enough to be digested by lipases from the pancreas.
pancreas
elongated organ that lies just behind the stomach, has both endocrine and exocrine functions.
Peristaltic contraction occurs?
every 15 to 25 seconds
gastric juices
hydrochloric acid (HCI) or mucus and pepsinogen.
Carboxypeptidase
in pancreas, active in small intestine, substance digested are peptides and breakdown amino acids.
Chymotrypsin
in pancreas, active in small intestine, substance digested are proteins, and breaks down peptides
Trypsin
in pancreas, active in small intestine, substance digested are proteins, breakdown peptides.
Intestinal enzymes
in small intestine, active in small intestine, substance digested are peptides and breakdowns amino acids.
Gastrin + neural reflex + stretching of stomach
increases motility of the large intestine after eating, causing feelings of defecate after first meal of the day.
Secretin + CCK + Stretching small intestine
inhibits stomach motility and stomach secretions. If chime flows too fast from the stomach, the small intestine will slow stomach activity.
Mucosa
innermost tissue layer, in contact with the lumen. All nutrients must cross the mucosa to enter the blood.
Nutrition
interaction between an organism and its food.
lower esophageal sphincter
located at the base of the esophagus, opens briefly as food arrives and closes after it passes into the stomach. Prevents reflux of the stomach's contents back into the esophagus.
gastric pits
millions of small openings in the mucosal layer. leads to the gastric glands below the surface.
Segmentation
mixes food. Short sections of smooth muscle contract and relax in seemingly random fashion. Back-in-forth mixing of the contents of the lumen. Occurs primarily in small intestine as food is digested and absorbed.
Submucosa
next to mucosa layer, connective tissue containing blood vessels, lymph vessels, and nerves. Components of foods that are absorbed across the mucosa enter the blood and lymph vessels of the submucosa.
Serosa
outermost layer of the GI tract wall. Thin connective tissue sheath that surrounds, anchors, and protects the other three layers and attaches the digestive system to the walls of the body cavities.
Pharynx
passageway for food and air, participates in swallowing
the process of defection
presence of feces stretches the rectum, stimulating sensory receptors that send impulses to relax and the rectum to contract, expelling the feces.
Intrinsic factor
protein that binds to vitamin B12 so that it can be absorbed in the small intestine. Secreted in the mucosal cells.
Regulation of delivery
regulates rate at which food is deliver to the small intestine.
Acid reflux
responsible for burning sensation known as "heartburn". Becomes more common with weight gain, pregnancy, and age. Occasionally it indicates a hiatal hernia
accessory organs
salivary glands, liver, gallbladder, and pancreas
Micelles
small droplets composed of bile salts and lecithin that have a polar outer surface and nonpolar inner core.
Lumen
space within hollow tubes of the GI tract areas through which food and liquids travel.
CCK + stretching duodenum
stimulates the gallbladder to contract and release bile.
food storage
stores food until it can be digested and absorb. Shrinks when empty and can expand to 1 to 3 liters.
nutrients
substances in food required for growth, reproduction , and the maintenance of health.
Mouth
teeth chew food, tongue positions and tastes food
Sphincters
thick rings of circular smooth muscle, separates some of the organs of the GI tract from each other. Sphincters contract they can close off the passageway between organs.
What is the function of micelles?
to transport fatty acids and monoglycerides to the outer surface of the mucosal cells so that they can be absorbed into the cells. Once in the cell, fatty acids and monoglycerides recombine into triglycerides.
bile
water mixture containing electrolytes, cholesterol, bile salts from cholesterol, a phospholipid called lecithin, and pigments such as bilirubin derived from the breakdown of hemoglobin.
chyme
watery mixture of partially digested food and gastric juice that is delivered to the small intestine.
Pancreatic Sodium Bicarbonate (NaHCO3)
works best at a more neutral pH unlike pepsin which is effective in acid conditions. NaHCO3 functions to neutralize stomach acid.