Digestion and Absorption

Question 1

Large intestine

Answer 1

takes 18-24 hours for food to pass by.

fece formation.

Propulsion and Mixing. Slight segmental mixing occurs. Mass movements propel feces toward the anus. and defecation eliminates the feces.

Secretion. Mucus provides lubrication; mucus and bicarbonate ions protect against acids produced by bacteria.

Absorption. The first half of the colon absorbs salts (e.g., NaCi), water, and vitamins (e.g.. K) produced by bacteri Elimination. The second half of the colon holds feces until they are eliminated.

Question 2

Functions of digestive system

Answer 2

Ingestion and mastication(chewing) - consumption of solid or liquid food.

propulsion and mixing - to exposed areas to secretion. large -> small

Digestion(breaking down), (mechanical and chemical) and secretion(adding to it),(addition of liquids and enzymes and mucous.

Elimination- feces!

Question 3

Oral cavity

Answer 3

Ingestion and Mastication. Solid food and fluids are taken into the digestive tract through the oral cavity.

The teeth break food into smaller pieces.

Propulsion and Mixing. The tongue forms food into a bolus and pushes the bolus into the pharynx to begin the swallowing reflex.

Digestion and Secretion. Mastication begins mechanical digestion of food. Amylase in saliva begins carbohydrate (starch) digestion.

Absorption. There is no absorption of nutrients in the mouth, although some drugs can be absorbed across the oral mucosa.

Question 4

Pharynx

Answer 4

Propulsion and Mixing. Swallowing moves the bolus from the oral cavity to the esophagus. Materials are prevented from entering the nasal cavity by the soft palate and kept out of the lower respiratory tract by the epiglottis and vestibular folds.

Secretion. Mucus provides lubrication.

Question 5

Esophagus

Answer 5

Propulsion and Mixing. Peristaltic contractions move the bolus from the pharynx to the stomach. The lower esophageal sphincter limits reflux of the stomach contents into the esophagus.

Secretion. Mucus provides lubrication and protects the inferior esophagus from stomach acid.

Question 6

Stomach

Answer 6

Propulsion and Mixing. Mixing waves churn ingested materials and stomach secretions into chyme. Rugae allow the stomach to expand and store food. Peristaltic waves move the chyme into the small intestine.

Secretion. Release of hydrochloric acid creates the acidic stomach environment. The acid kills most microorganisms and activates the precursor of the proteolytic enzyme pepsin. Mucus provides lubrication and prevents digestion of the stomach wall.

Digestion. Mechanical digestion occurs as food is churned in the stomach by mixing waves. Protein digestion begins as a result of the actions of hydrochloric acid and pepsin.

Absorption. Absorption of only a few substances (e.g, water, alcohol, aspirin) takes place in the stomach.

Question 7

Small intestine

Answer 7

Propulsion and Mixing. Segmental contractions mix the chyme, and peristaltic contractions move the chyme into the large intestine.

Secretion. Bicarbonate ions from the pancreas and bile from the liver neutralize stomach acid to form a pH environment suitable for pancreatic and intestinal enzymes. Mucus provides lubrication, prevents digestion of the intestinal wall, and protects the small intestine from stomach acid.

Digestion. Segmental contractions aid mechanical digestion. Enzymes from the pancreas and the lining of the small intestine complete the breakdown of food molecules. Bile salts from the liver emulsify lipids to allow lipid digestion.
Absorption. The circular folds, villi, and microvilli increase surface area. Most nutrients are actively or passively absorbed. Most of the ingested water or the water in digestive tract secretions is absorbed.

Question 8

Serosa

Answer 8

(serous membrane visceral peritoneum)

Connective tissue layer

simple squamous epithelium

helps maintain structural integrity

Question 9

Muscularis

Answer 9

Circular muscle layer

longitudinal muscle layer

propulsion of food

Question 10

Submucosa

Answer 10

thick layer of connective tissue where nerves, blood vessels and small glands.

Question 11

Mucosa

Answer 11

(mucous membrane)

Epithelium lamina propia

muscularis mucosea

has layer so we dont digest ourselves

actually touches food

1.absorptive cells – have microvilli, produce digestive enzyme and absorb digestive food.

2.goblet cells – which produce a protective mucus

3.granular cells - which may help protect the intestinal epithelium from bacteria.

4.endocrine cells - which produce regulatory hormones.

Question 12

Voluntary phase - deglutition

Answer 12

bolus is formed in the mouth

tongue pushes bolus against hard palette.

push food to back of mouth, touches soft palate to initiate

Question 13

Pharyngeal phase - Deglutition

Answer 13

close epigloths so food doesnt go into trachea

Question 14

Deglutition (Swalling)

Answer 14

swallowing controlled by a reflex

bolus stimulates receptors in oropharynx

force food down pharynx

epiglottis covers opening into larynx

Question 15

Esophageal phase

Answer 15

moves from pharynx to stomach

muscular contractions occur in peristaltic waves

peristaisis

Question 16

salivary annylase

Answer 16

breaks down starch

breaks covalent bonds between glucose molecules

food spends little time here

Question 17

Oral Cavity - functions of major digestive system secretions

Answer 17

-Creation:

Serous saliva (mostly water, bicarbonate ions)

Salivary glands

Mucus

Lysozyme

-Function:

Moistens food and mucous membrane: neutralizes bacterial acids: flushes bacteria from oral cavity

Digests carbohydrates

Lubricates food; protects digestive froct from digestion

Has mild antibacterial activity

prevents bacterial infections in the mouth

saliva neutralizes pit in mouth

Question 18

Stomach - functions of major digestive system secretions

Answer 18

-Creation:

Hydrochloric acid

Pepsin

Mucus

Intrinsic factor

Gastric lipase

-Function:

Antibacterial; decreases stomach pi to activate pepsinogen to pepsin

Digests protein into smeller peptide chains; activates pepsinogen

Protects stomach lining from acid and digestion

Binds to vitamin B, and aids in its obsorption in the small intestine

Question 19

Liver

Answer 19

-Creation:

Bile

-Function:

Bile salts in bile emulsify lipids, making them available to lipases, and help make end products soluble and available for absorption by the intestinal mucosa, many of the other bile contents are waste products, such as bile pigments, that are transported to the intestines for disposal

Question 20

Pancreas - functions of major digestive system secretions

Answer 20

-Creation:

Trypsin

Chymotrypsin

Carboxypeptidase

Pancreatic amylose

Pancreatic lipase

Cholesterol esterase

Ribonuclease

Deoxyribonuclease

Bicarbonate ions

-Function:

Digests proteins (cleaves at orginine or lysine amino acids; activates trypsinogen and other digestive enzymes

Digests proteins (cleaves at hydrophobic amino acids)

Digests proteins (removes amino acids from the carboxyl end of proteins)

Digests carbohydrates (hydrolyzes starches and glycogen to form maltose and
isomaltose)

Digests lipids (breaks down triglycerides into monoglycerides and free fatty acids)

Digests cholesteryl esters (breaks down into cholesterol and free fatty acid

Digests ribonucleic acid hydrolyzes phosphodiester bonds)

Digests deoxyribonucleic acid thydrolyzes phosphodiester bonds)

Neutralize acid from stomach; provide appropriate pH for pancreatic enzymes

Question 21

Small intestine - functions of major digestive system secretions

Answer 21

-Creation:

Mucus

Peptidases

Enterokinase

Sucrase

Maltase

Isomaltase

Lactase

-Function:

Protects duodenum from stomach acid, and intestinal wall from digestive enzymes

Split amino acids from polypeptides

Activates trypsin from trypsinogen

Splits sucrose into glucose and fructose

Splits maltose into two glucose molecules

Splits isomaltose into two glucose molecules

Splits lactose into glucose and galactose

Question 22

Large intestine - functions of major digestive system secretions

Answer 22

-Creation:

Mucus

-Function:

Provides adhesion for fecal matter; protects intestinal wall from bacterial acids and actions

Question 23

Pyloric sphincter

Answer 23

entry/exit

between stomach and duodenum (SI)

helps regulate movement of gastric contents into SI

Question 24

Gastrin - functions of the major digestive system hormones

Answer 24

Source: Gastric glands

Function:
Increases gastric secretions.
In anticipation of food entry.
Protect stomach lining

Question 25

Secretin - functions of the major digestive system hormones

Answer 25

Source: Duodenum (SI) Function: decreases gastric secretions. Increases pancreatic and bile secretions high in bicarbonate ions - neutralize stomach acid - also corrected PH balance. Slow food entry for good digestion and absorption - prolong effect. Decreases gastric motility

Question 26

Cholecystokinin - functions of the major digestive system hormones

Answer 26

Source:Duodenum(SI) Function: Decreases gastric secretions. Strongly decreases gastric motility. Increases gallbladder contraction. Increases pancreatic enzyme secretion.

Question 27

Cephalic phase

Answer 27

get things started; see food, smell food. getting ready for expected food. Brain phase of stomach secretion, controlled by the CNS begins before bolus of food enters the stomach. tase, smell, or though of food or tactile sensations of food in mouth stimulate the medulla oblongale. AP are sent from here along parasympathetic axons within the vagus nerves to the stomach. the preganglionic neurons stim postanglionic neurons in enteric plexus. The postanglionic neurons stimulate secretory activity in the cells of the stomach mucosa, causing the release of hydrochloric acid, pepsin, mucus, and intrinsic and histamic from endocrine cells. Gastrin is a hormone that enters the blood and is carried back to stomach, where it stimulates additional secretary activity. Histine is both the paracrine chemical signal the acts locally and hormone that enters the blood to stimulate gastric gland secretory activity. Histane is the most Hcl acid secretion. Drugs that block actions of histamine can decrease acid levels.

Question 28

Gastric phase

Answer 28

When food enters stomach. ramp up secretions.

Question 29

Hydrochloric acid

Answer 29

produces pH of 2.0 in stomach. acid kills microorganisms and activates enzyme pepin

Question 30

Pepsin

Answer 30

is converted from its inactive form, called pepsinogen. Breaks covalent bonds of proteins to form smaller peptide chains.

Question 31

Mucous

Answer 31

forms a thick layer. Lubricates epithelial cells of stomach wall and protects from acidic chyme and pepsin

Question 32

Intrisic factor

Answer 32

Binds with Biz and makes it more rapidly absorbed Biz - important for DNA synthesis and rbc production. heartburn is a powerful sensation in chest visually associated with increase in g

Question 33

Preparation of Chyme

Answer 33

what food becomes when mixed with stomach secretions Mixing and propulsion of chyme and primary mechanical events that occur in the SI Persistaltic contractions proceed along the SI variable distances and cause chyme to move Segments contractions are propagated for only short distances and mix intestinal contents mixing waves of contractions until we form liquid enough chyme Produces greatest volume gastric secretions activated by food in stomach stomach stretch stimulates mechanoreceptors and acted parasympathetic reflex. AP generated and carried by vagus nerve to medulla. Stretch also activates local reflexes that increase stomach secretions Peptides made by action of Pepsin on proteins, stimulate secretion of gastrin. Gastrin carried through blood, back to stomach, where along with histamines stimulates secretion.

Question 34

Intestinal phase

Answer 34

we want to slow things down. little chyme (very acidic) entering at a time for exposure to secretions for absorption. inhibits gastric secretions controlled by entrance of acidic chyme into duodenum which initiates neural and hormonal mechanisms. Acidic chyme in duodenum inhibits CNS stimulation and initiates local reflexes that inhibit gastric secretions. chemoreceptors stimulated and initiates local reflexes that inhibit gastric secretions. chemoreceptors stimulated by H+ or lipids -- AP's generated here carried by vagus nerves to medulla where they inhibit PNSAP and decrease gastric secretions. local reflexes activated by H+ or lipids also inhibit gastric secretion Secretin (hormone) inhibits gastric secretion. - Stimulates bile secretion, - released in response to low pH. Fatty acids and peptides in duodenum initiate release of hormone cholecy stokinin, which inhibits gastric secretions

Question 35

Structure and function of small Intestine

Answer 35

large SA main function is absorption of nutrients. consists of : duodenum, jujunum and ileum. secretion from mucosa of the small intestine contain mainly mucus ions and water. SI secretions lubricate and protect the intestinal wall from the acidic chyne and action of digestive enzymes. Keep the chyme in the SI in a liquid form to facilitate the digestive process. Have intestinal enzymes peptidales - digest proteins by breaking peptide bonds in proteins to form a.a disaccarides and digest small sugars. Capillary (blood), Lacteal (lymph) - provide nutrients, picking up absorbed material. --> absorption of fats before circulation fats are hydrophobic so they have to be packages to move through blood. stomach has pits in vaginations while SI has villi(outward)

Question 36

4 Major cell types in mucosa

Answer 36

1.Absorptive cells: have microvilli. Produce digestive enzymes. Absorb digestive foods. 2.Goblet cells: Produce protective mucous. 3.Granular cells: help protect intestinal bacteria. 4.Endocrine cells: produce regulatory cells Mixing and propulsion of chyme is the primary mechanical event.

Question 37

Digestion - functions of the liver

Answer 37

Bile neutralizes stomach acid and emulsifies fats, which facilitates for digestion.

Question 38

Excretion - functions of the liver

Answer 38

Bile contains excretory products, such as cholesterol, fats, and bile pigments (e.g., bilirubin), that result from hemoglobin breakdown.

Question 39

Nutient storage - functions of the liver

Answer 39

Liver cells remove sugar from the blood and store it in the form of glycogen; they also store fat, vitamins (A, B. D, E, and K), copper, and iron.

Question 40

Nutrient conversion - functions of the liver

Answer 40

Liver cells convert some nutrients into others; for example, amino acids can be converted to lipids or glucose, fats can be converted to phospholipids, and vitamin D is converted to its active form.

Question 41

Detoxification of harmful chemicals - functions of the liver

Answer 41

Liver cells remove ammonia from the blood and convert it to urea, which is eliminated in the urine; other substances are detoxified and secreted in the bile or excreted in the urine.

Question 42

Synthesis of new molecules - functions of the liver

Answer 42

The liver synthesizes blood proteins, such as albumin, fibrinogen, globulins, and clotting factors.

Question 43

Liver

Answer 43

Largest internal organ in body receives blood from hepatic artery and portal vein. hepatic artery -- delivers oxygenated blood to liver to provide O2

Question 44

Bile

Answer 44

Bile neutralized stomach acids Important because pancreatic enzymes cant function at acidic pH Bile salts- emulsify lipids, needed for digestion of lipase. parasympathetic stimulation from vagus nerve stimulates gallbladder to control releasing bile into duodenum. cholecystokinin and secretion as help. bile salts increase bile secretion through pos feedback.

Question 45

Exocrine pancreas secretions.

Answer 45

intestinal phase pancreatic islet produce insulin and glucogen and somatiosin Protein digestion -Trypsin, Chymotrypsin, Carbocypeptidase Lipid digestion-Pancreatic amylase Carbohydrate Digestion- Pancreatic amylase Neutralize Stomach Acid- Bicarbonate ion. buffer. maintain neutral environment secreted from pancreas. To stop pepsin digestion. Required for pancreatic enzymes.

Question 46

Overview of digestion

Answer 46

breakdown of food to molecules that are small enough to be absorbed by blood · absorption begins in stomach -- most occurs in SI breakdown so they can be absorbed across the PM in intestine.

Question 47

Carbohydrates proteins

Answer 47

mechanical digestion in mouth, just no chemical. Breakdown smaller chains. Salivary amylase doesnt work in stomach because pH is too low. Nothing in mouth or stomach just mayingalittle mixing.

Question 48

Cellulose

Answer 48

polysaccaride, not digested but important for fiber

Question 49

Carb digest

Answer 49

1) Salivary amylase: begins carb digestion, breaks down polysaccarides. 2) Stomach to continue mixing food with acid, which inactivates salivary amylase. 3) Pancreatic enzyme: dudenum, breaks polysaccarides into smaller disaccatides 4) Disaccharidases: digest disaccharides into monosaccharides which are then absorbed by intestinal epithelial cells. 5) absorption occurs through cotransport, diffusion of Na+ down [ ] gradient provides NRG for glucose to move across membrane (secondary active transport) invaginations and microvilli drastically increase SA

Question 50

Absorption of lipids

Answer 50

1) Lipase, secreted by pancrease, digests lipid molecules primary products are fatty acids and monoglycerides. 2)Emulsification where bile salts transform large lipid droplets into smaller ones. This increases SA of lipid droplets to expose them to digestive enzymes (lipases)

Question 51

Transport of lipids in circulation

Answer 51

1) once lipids are digested in SI, bile sales aggregate around small droplets of digestive lipids to form micelles. 2) lipids pass via simple diffusion from micelles through cell membrane of epithelial cells. 3) fatty acids and monglycerides recombine to form triglycerids. Packed into chylomicron. 4) Chylomicron leave epithelial cells via exocytosis and enter lacteals absorbed lipid is called chyle.--> decreases if not chylomicrons go to liver to be stored, converted to other molecules or used as NRG.

Question 52

Absorption - amino acids (protein)

Answer 52

1) pepsin secreted by stomach breaks down large proteins into smaller individual polypeptides. 2)Enzymes trypsin, chymotrypsin and carboxypeptidases once in SI 3)Peptidases furthere break down protein -- bound to microvilli/ in SI 4)absorption occurs through cotransport, most with Na+ gradient 5) move out of intestinal epithelial cells 6)a.a enter blood capillaries in the villi and are carried by hepatic portal vein and to the liver.

Question 53

Fluid ingestion, secretion and reabsortion

Answer 53

9L of water enters digestive tract (2L food + drink, 7L digestive secretions. 92% absorbed by SI