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.