Digestive Exam Review

the feeding method used to take food into the digestive cavity

ingestion

the splitting of carbohydrates, proteins, lipids, and nucleic acids in foods into chemical subunits small enough to be absorbed into an animal’s body fluids and cells

digestion

the movement of organic molecules, electrolytes (inorganic ions), vitamins, and water across the digestive epithelium and into the interstitial fluid of the digestive tract

absorption

what are the 3 feeding strategies?

herbivore, carnivore, omnivore

one calorie is defined as

the amount of energy required to raise the temperature of 1g of pure water by 1^o C

1 Calorie (or Kcal) is defined as

1000 calories

what are the forms of malnutrition?

undernutrition, overnutrition, and micronutrient-related deficiencies

carbohydrates, proteins, lipids, and vitamins are all

complex organic nutrients

minerals are ___ nutrients

simple inorganic

calcium, magnesium, iron, zinc, potassium are all

minerals

what are the essential amino acids?

valine, leucine, isoleucine, methionine, phenylalanine, tryptophan, threonine, lysine, and histidine (in infants)

what are the essential fatty acids?

linoleic acid and linolenic acid

describe each type of feeding method:

fluid feeding - ingest liquids that contain organic molecules in solutions (ex. blood or nectar)

suspension feeding - ingest small organisms that are suspended in water

deposit feeding - ingest particles of organic matter from solid material they live in/on (ex earthworms, crabs)

bulk feeding - ingest food items whole or in large chunks (most adult mammals, reptiles, birds, amphibians)

describe intracellular digestion (in sponges)

cells (choanocytes) take in food particles through pores in the body walls by endocytosis

a endocytic vesicle containing food particles fuses with a lysosome to form endolysosome

hydrolytic enzymes digest the food particles into their molecular subunits

undigested food is released by exocytosis

explain the sac-like digestive system in flatworms and cnidarians

single opening - both entrance and exit for food/undigested materials

digestion begins in gastrovascular cavity and is completed intracellularly

extracellular digestion occurs in what type of organism?

all vertebrates, some invertebrates.

in extracellular digestion, ___ secrete enzymes

accessory glands

what are the advantages of extracellular digestion?

greatly expands the range of available food sources, allows animals to eat large batches of food

in ___ digestion, food moves in a single direction through the body

extracellular

what are the 5 successive steps of extracellular digestion?

1. mechanical processing

2. secretion of enzymes and other digestive aids

3. Enzymatic hydrolysis

4. absorption

5. elimination

in which step of digestion do organic molecules in the food become broken down into small absorbable units?

enzymatic hydrolysis (third step)

salivary ___ begins the digestion of starch in the ___ step of digestion

amylase, first step (mechanical processing)

how does digestion work in annelids (earthworms)?

earthworms are deposit feeders.

1. Muscular movement propels food through the esophagus

2. food enters crop where it is mixed with mucus

3. mixture enters gizzard where mechanical processing occurs

4. then enters intestine where enzymatic hydrolysis occurs

5. undigested residue expelled through anus

digestion in arthropods

1. insects use mouthparts to tear plant parts into small particles

2. salivary secretions initiate digestion in the pharynx

3. food moves through the esophagus, crop, and gizzard into stomach

4. enzymatic hydrolysis in gastric ceca

5. undigested contents move into intestine for further digestion/absorption

6. water reabsorbed in the distal intestine and wastes expelled through anus

digestion in avians

1. seeds are moistened by mucus in the saliva

2. seeds pass through pharynx

3. esophagus

4. crop (food stored here)

5. proventriculus (digestive secretions mix with food here)

6. gizzard (seeds are ground up here)

7. intestine (food mixed with bile from the liver and digestive enzymes from the pancreas)

8. absorption of molecular subunits

9. undigested residues expelled through anus

the human digestive system consists of a series of specialized digestive regions that are under ___ control

neuoendocrine

list the parts of the GI tract/alimentary canal

mouth → pharynx → esophagus → stomach → small and large intestines → rectum → anus

what are the accessory digestive structures in human digestion?

salivary glands, teeth, tongue, pancreas, liver, gall bladder

organic compounds that are needed in small quantities. most are obtained from food intake, but some people need to supplement.

vitamins

vitamin ___ can be synthesized in the body when the skin is exposed to UV light

D

vitamin ___ is required for blood clotting and is supplied from the ___

K, large intestine

humans require ___ known fat- and water-soluble vitamins in their diet

13

what are the fat soluble vitamins?

vitamins A, D, E, K

what are the water-soluble vitamins?

vitamins of the B complex and C

minerals are ingested as

compounds or ions in solution

list the macrominerals

calcium, phosphorus, magnesium, sodium, potassium, chloride, and sulfer

list the microminerals (or trace minerals)

iron, copper, manganese, selenium, fluoride, cobalt, and iodine

hypernatremia

too much sodium, elevates BP

excessive iron results in

hemochromatosis. liver, heart, pancreas, and blood vessel damage

name the mineral: involved in bone and tooth formation, blood clotting, neural and muscle action?

calcium

name the mineral: involved in HCl formation in stomach, contributes to body’s acid-base balance, necessary for neural function and water balance

Chlorine

name the mineral: Required for many enzymes, in bones and teeth, ATP processing

magnesium

name the mineral: in bones and teeth, component of nucleic acids, ATP and phospholipids; energy processing

phosphorus

name the mineral: muscle and neural function, water balance; muscle and neural function; main positive ion in cell

potassium

name the mineral: Acid-base balance; water balance; muscle and neural function; main positive ion in extracellular fluid

sodium

name the mineral: component of body proteins

sulfur

name the mineral: thyroid hormone function

iodine

name the mineral: component of hemoglobin, myoglobin, and electron carriers

iron

name the mineral: component of many enzymes and some transcription factors; protein synthesis; DNA synthesis; cell division; immunity; wound healing

zinc

list the four major layers of the gut

mucosa, submucosa, muscularis, serosa

innermost layer of the GI wall. contains epithelial and glandular cells, lines the inside of the digestive tract. also contains some connective tissue and smooth muscle

mucosa

thick layer of elastic connective tissue that contains neuron networks (the enteric nervous system), blood and lymph vessels, and small glands. second innermost layer of the GI tract

submucosa

formed by two smooth muscle layers (circular and longitudinal) that play an essential role in mechanical processing and in moving materials along the digestive tract

muscularis

what is peristalsis? where does it come from?

peristalsis is a wave of contractions that passes along the gut, constricting the git and pushing the digestive contents onward. It is produced by the muscularis layer of the GI tract

contraction of the ___ muscles and relaxation of the ___ muscles lengthens the gut, and vice versa.

contraction of circular muscles and relaxation of longitudinal muscles = lengthened gut

the outermost layer of the GI wall, made of serous membrane. This layer is actually the visceral layer of the peritoneum.

serosa

movement of food through the digestive tract is regulated by ___ present at the junction between various regions

sphincter muscles

what are sphincter muscles?

smooth muscles that contract and relax to push the contents from one region to another

sphincter between the pharynx and the esophagus

pharyngoesophageal sphincter (or upper esophageal sphincter)

sphincter between the esophagus and the stomach

gastroesophageal sphincter

sphincter between the stomach and the duodenum

pyloric sphincter

sphincter between the ileum and the cecum

ileocecal sphincter

what is the final sphincter in the digestive tract?

the anal sphincter

what disease causes unpleasant symptoms due to the backflow of stomach acids into the esophagus?

gastroesophageal reflux disease (GERD)

what happens if GERD is left untreated?

can cause precancerous lesions such as seen in Barrett esophagus (chronic inflammation)

trace the journey of food through the GI tract.

mouth → pharynx → esophagus → stomach → small intestine → large intestine → anus

starch digestion begins in the

mouth

the ___ prevents the movement of food into the respiratory tract

epiglottis

what is the main function of the stomach?

store food and aid in mechanical breakdown of food by disrupting the chemical bonds in food through the action of acid and the enzyme pepsin

the stomach also produces an intrinsic factor for…

the absorption of vitamin B12 in the small intestine

in addition to the outer longitudinal and middle circle layer, the stomach has another muscle layer called the ___. what is its role?

oblique muscle layer. its roles are to strengthen the stomach wall and mix and churn for the formation of chyme

what are rugae?

the prominent folds in the stomach when it is relaxed. these go away as the stomach stretches

protein digestion begins in the ___ by the enzyme ___

stomach, pepsin

when is chyme formed? where does it go from there

partially digested food at the end of the stomach digestion is called chyme. it moves through the pyloric sphincter into the duodenum (small intestine)

what are gastric pits?

shallow depressions of the mucosal layer containing gastric glands

gastric juice contains (name each secretion and what cell they’re secreted from)

pepsinogen - secreted by chief cells

hydrochloric acid - H+ and Cl- ions secreted by parietal cells (combine to form HCl in the lumen of the stomach)

mucus - produced by goblet cells

what is the importance of hydrochloric acid in the stomach?

keeps the stomach contents at a low pH, kills microorganisms, helps break plant cell walls and connective tissues in meat, activates pepsinogen to active pepsin

most absorption (90%) occurs in the

small intestine

the absorptive ability of the small intestine is increased by

increased surface area by the folds in the small intestine, which are covered by intestinal villi, which are covered by microvilli

as compared to the rugae of the stomach, permanent folds in the intestine…

do not disappear when the small intestine fills

pancreatic enzymes aid in

proteolytic digestion (protein digestion by breaking polypeptide chains)

___ secretes bile that is stored in the ___ for discharge into the ___

liver, gallbladder, small intestine

what do bile salts do?

break down into small lipid droplets to facilitate the digestion and absorption of lipids

list the three parts of the small intestine and their main function

duodenum - receives chyme from the stomach, mixes it with pancreatic enzymes and bile

jejunum - bulk of chemical digestion and absorption

ileum - longest and final segment of the small intestine

the liver stores excess glucose in the form of ___

glycogen

the liver synthesizes lipoproteins that

transport fats and cholesterol

this organ detoxifies ethyl alcohol and other toxic chemicals and drugs, as well as inactivates steroid hormones

the liver

what is the hepatic portal vein?

the vein that leads to the liver

the ___ is known as the “large bowel”

large intestine

the large intestine begins at the ___ and ends at the ___

end of the ileum, anus

list the parts of the large intestine

cecum, colon, rectum, terminates at the anal sphincter.

the colon can be subdivided into

ascending, transverse, descending, and sigmoidal

<10% of nutrient absorption is underway in the ___

large intestine

the ___ sphincter regulates the movement of substances from the ileum and the cecum

ileocecal

the cecum…

collects and stores materials from the ileum and begins the process of compaction

the rectum…

serves as a temporary storage space for feces

the large intestine secretes ___ and ___

mucus and bicarbonate ions

reabsorption of water occurs in ___. what else is reabsorbed?

the large intestine. ions, bile salts, and vitamins

the intestinal probiotic organisms residing in the large bowel produce:

useful metabolites, fatty acids, and vitamins such as vitamin K, folic acid, biotin, pantothenic acid

bacteria convert bilirubin into ___, and oxidation produces ___. these result in what?

urobilinogens and stercobilinogens; urobilins and stercobilins. these give feces its characteristic color