chapter 25 sections 25.6 and 25.7 - Chemical Digestion & Absorption, The Large Intestine

the final 3 cm of the large intestine is the ______ ______ which passes through the levator ani muscle of the pelvic floor and terminates at the anus

anal canal

the mucosa of the large intestine has a simple columnar epithelium in all regions except the lower half of the ____ _____ which has a nonkeratinized stratified squamous epithelium

anal canl

vigorous _______ _______ breaks up the fat into small droplets dispersed throughout the watery chyme that emulsifies the fat before passing it on to the duodenum, exposing much more fat surface to enzymatic action

antral pumping

attached to the lower end of the cecum is the _____. it is densely populated with lymphocytes and is a significant source of immune cells

appendix

the ______ colon begins at the ileocecal valve and passes up to right side of the abdominal cavity.

ascending

what are the four regions of the colon?

ascending, transverse, descending and sigmoid

the transverse colon passes horizontally across the upper abdominal cavity and turn 90* toward the left colic (splenic) flexure near the spleen. here is becomes the ______ colon where it passes down the left side of the abdominal cavity

descending

the brush border enzymes ______ and _____ hydrolyze oligosaccharides that are three or more residues long

dextrinase, glucoamylase

_______ occurs when the large intestine absorbs too LITTLE water *it occurs when the intestine is irritated by bacteria and feces pass through too quickly for adequate reabsorption or when the feces contains abnormally high concentrations of a solute that opposes osmotic absorption of water

diarrhea

amino acids absorbed from the small intestine come from what 3 sources?

dietary proteins, digestive enzymes digested by each other, sloughed epithelial cells digested by these enyzmes

_________ splits dipeptides in the middle and releases the last two free amino acids

dipeptidase

in the duodenum, _________ _______ received from the stomach are coated by certain components of bile - lechithin and bile acids

emulsification droplets

the digestion is complete as the chyme contacts the brush bordr of the _________

enterocytes

micelles transport lipids to the surfaces of the _____ where the lipids leave the micelles and diffuse through the plasma membrane into the cell

enterocytres

the _____ anal sphincter is under voluntary control, enabling one to limit defecation to appropriate circumstances

external

the glucose taken up by the SGLT is transported out of the base of the cell and into the _____ ______

extracellular fluid

the nonkeratinized stratified squamous epithelium of the lower half of the anal canal provides resistance to the abrasion caused by the passage of ______

feces

the large intestine contains about 7-10 L of gas. Expelling about 500 mL/day as _____ and reabsorbs the rest

flatus

of the 9 L of water the digestive tract, the following amount come from what sources? 0.7 L from _____ 1.6 L from _____ 6.7 L from ____

food, drink, intestinal secretions (saliva, gastric, intestinal and pancreatic juice, bile)

pepsin hydrolyzes any peptide bond between tyrosin and phenylalanine - digesting 10-15% of dietary protein into shorter polypeptides and small amount of _____ _____ ______

free amino acids

when lipase acts on a triglyceride, it removes the first and third fatty acids from the glycerol backbone and usually leaves the middle one. the products of lipase action are therefore two _____ _____ ____ and a __________

free fatty acids, monoglyceride

mass movements are often triggered by the ________ and _____ reflexes in which the filling of the stomach and duodenum stimulates motility of the colon

gastrocolic, duodenolic

the intestinal crypts of the large intestine are deeper than in the small intestine and have a greater density of ______ cells that secrete mucus

goblet

the large intestine harbors about 800 species of bacteria collectively called the _____ _____

gut microbiome

the muscle tone of the taeni coli contract the colon lengthwise and causes its wall to bulge and form pouches called

haustra

the most common type of colonic motility is a type of segmentation called _______ _____ which occur about every 30 minutes

haustral contractions

prominent _________ veins form superficial plexuses in the anal columns around the orifice

hemorrhoidal

________ are permanently distended veins that protrude into the anal canal or form bulges external to the anus.

hemorrhoids

iron absorption is stimulated by the live hormone _______

hepcidin

transcellular calcium uptake is under ______ influence

hormonal

the jejunum and ileum absorb more calcium than the duodenum because of their greater length. They absorb by the paracellular route and are independent of _______

hormones

the charged ________(hydrophilic/hydrophobic) surface of the micelles keep them suspended in water more easily than free lipids do

hydrophilic

the ________(hydrophobic/hydrophilic) quality of lipids make their digestion and absorption more complicated than that of carbohydrates and proteins

hydrophobic

emulsification droplets have a ________ region attracted to the surface of a fat globule and a ________ region attracted to the surrounding water

hydrophobic, hydrophilic

sugar entering the ECF ____(increases/decreases) its osmolarity and this draws water osmotically from the lumen of the intestine through the leaky tight junctions between the epithelial cells

increases

flatus is composed of nitrogen, carbon dioxide, hydrogen, methane, hydrogen sulfife and two amines: ______- and _______

indole and skatole

what 3 components of flatus produce the odor of both flatus and feces

indole, skatole and hydrogen sulfide

there are no circular folds or villi in the large intestine but there are ______ ______

instestinal crypts

the ______ anal sphincter is composed of smooth muscle of the muscularis externa the _____ anal sphincter is composed of skeletal muscle of the pelvic diaphragm

internal, external

one of the products of the intestinal bacteria is ______ ______

intestinal gas

the process of defecation involves what two reflexes?

intrinsic defecation reflex and parasympathetic defecation reflex

B12 is absorbed poorly unless bound to ____ ____ in the stomach

intrinsic factor

the defecation reflexes are ______ (voluntary/involuntary) and are the sole means of controlling defecation in infants and some people with transecting spinal cord injures

involuntary

carboxypeptidase removes amino acids from the _____(-NH2 or -COOH) end of the chain

-COOH

aminopeptidase removes amino acids from the ____(-NH2 or -COOH) end

-NH2

vitamin D affects the absorptive cells of the duodenum is what three ways?

-increases the number of calcium channels in the apical membrane -increases the amount of calbindin in the cytoplasm -increases the number of calcium-ATPase pumps in the basal membrane THERFORE, it increases absorption of dietary calcium and raises the level of calcium in the blood

what percentage of dietary fat is digested before the chyme passes on to the duodenum?

10-15%

mass movements last about ____ minutes and move residue ceveral cm at a time

15

the solids of the feces include what?

30% bacteria, 30% undigested dietary fiber, 10-20% fat and small amount of protein, salts, mucus and digestive secretions

in most of the world population, lactase production ceases or declines to a low level after age ____ and lactose becomes inigestible (lactose intolerance)

4

the small intestine absorbs only about ___% of dietary calcium, leaving the rest to pass in the feces

40

without micelles, the small intestine absorbs only __-__% of dietary fat and almost no cholesterol

40-50%

endogenous(having an internal origin) amino acids account for 30 g/day and approximately ___-___ g/day come from the diet

44-60

the large intestine measures about ___ ft in length and 6.5 cm in diameter

5

__% of dietary starch is digested before it reaches the small intestine. It's digestion resumes in the small intestine when the chyme mixes with pancreatic amylase

50

salivary amylase functions best at pH of ____ - ____ (typical of the oral cavity)

6.8-7.0

feces usually consists of ___% water and ___% solids

75% water, 25% solids

the digestive system receives about __ L of water per day

9

the fat-soluble vitamins ____ , ____, ____, and ____ are absorbed with other lipids. therefore, if they are ingested without fat-containing food they are not absorbed at all but are passes in the feces and wasted

A, D, E, and K

______ and _____ are absorbed in proportion to the body's need - other minerals are absorbed at a fairly constant rate regardless of need - leaving it to the kidneys to excrete any excess

iron, calcium

_______ lipase is secreted by the intrinsic salivary glands of the tongue and digests a small amount of fat while food is still in the mouth. It becomes more active at the acidic pH of the stomach where it joined by _______ lipase

lingual, gastric

fats are digested by enzymes called ______

lipases

the lamina propria and submocasa of the large intestine has an abundance of ______ tissue which provides protection from bacteria

lymphatic

______, a brush border enzyme, hydrolyzes maltose to glucose

maltase

stronger than haustral contractions, _____ _____ occur 1-3 times per day

mass movements

the absorption of free fatty acids, monoglycerides and other lipids depends on minute droplets in the bile called ______

micelles

amino acid absorption is most like ______ absorption

monosaccharide

the intrinsic defecation reflex is mediated entirely by the ________ _______ -stretch signals travel through here and to the muscularis of the descending and sigmoid colon and the rectum -peristaltic wave is activated and drives feces downward and relaxes the internal anal sphincter

myenteric plexus

______ and ______ of the brush border dempose the nucleotides into phophate ions, ribose (from RNA) or deoxyribose (from DNA) and nitrogenous bases

nucleosidases and phosphatases

most absorbed calcium is from meat and dairy products. Green leafy vegetables also contain a lot of calcium but contain _____ which makes calcium unavailable for absorption

ocalate

starch is digested first to __________ up to eight glucose residues long and then into the disaccharide maltose and then finally into _______ which is absorbed by the small intestine

oligosaccharides, glucose

pepsin has an optimal pH of 1.5-3.5 so it is inactivated when it passes into the duodenum and mixes with the alkaline ______ ______ which has a pH of 8

pancreatic juice

there is enough _____ ______ in the small intestine after a meal to digest the average daily fat intake in as little as 1 or 2 minutes

pancreatic lipase

during the action of the parasympathetic defecation reflex, stretch signals are transmitted to the spinal cord and motor signals return by way of the pelvic nerves to intensify _____ in the descending and sigmoid colon and rectum and to relax the internal anal sphinchter

peristalsis

the absorptive cells of infants can take up intact proteins by _____ and release them into the blood by ______ -this allows IgA from breast milk to pass into infants bloodstream

pinocytosis, exocytosis

enzymes that digest proteins are called _______

proteases (peptidases)

voluntary retention of feces is aided by the _______ muscle

puborectalis

the B12-IF complex binds to receptors on absorptive cells of the distal ileum, where it is taken up by ______-_______ endocytosis

receptor-mediated endocytosis

in the pelvic cavity, the large intestine continues as the _______ which is about 15 cm long

rectum

stretching of the ______ stimulates the defecation reflexes which account for the urge to defecate that is often felt soon after a meal.

rectum

DNA and RNA are hydrolyzed into their constituent nucleotides by _____ and _____ of the pancreatic juice

ribonuclease, deoxyribonuclease

the digestion of starch begins in the mouth when ________ ________ hydrolyzes starch into oligosaccharides

salivary amylase

due to the narrowness of the pelvic cavity, the colon turns medially at the hip bone and travels along the iliac fossa before turning downward at the pelvic inlet. This resulting S-shaped portion is called the _____ colon

sigmoid

how are potassium ions absorbed?

simple diffusion

electrolytes are absorbed along the entire length of the ______ ______

small intestine

the _____ _____ absorbs nearly all dietary phosphate, mainly by active transport

small intestine

the ascending, transverse and descending colons form a three sided frame around the ______ ______

small intestine

the SGLT also absorbs galactose but fructose is absorbed by facilitated diffusion using a separate carrier that does not depend on _______

sodium

about 80% of absorbed sugar is taken up by a _____-_____ transporter (SGLT) similar to the kidney tubules

sodium-glucose

water carried more gluocse than other nutrient with it by a process called ______ _______

solvent drag

the parasympathetic defecation reflex is a ______ reflex

spinal

what is most digestible dietary carbohydrate?

starch

sucrose and lactose are digested by the brush border enzymes ____ and _____ resulting in monosaccharides that are immediately absorbed

sucrase, lactase

maltose is present in some food but the major dietary disaccharides are _____(cane sugar) and _____(milk sugar)

sucrose, lactose

many of the bacteria in the large intestine digest cellulose, pectin and other plant polysaccharides for which we have no digestive enzymes and we absorb the resulting _____

sugars

sodium ions are cotransported with _____ and ______

sugars and amino acids

the muscularis externa encircles the colon but its longitudinal fibers are especially concentrated in three thickened ribbon-like strips where each strip is called a ______ _____

taenia coli

what are the four regions of the large intestine?

the cecum, colon, sigmoid colon and the anal canal

defecation normally occurs only when what two things are voluntarily relaxed?

the external anal sphincter and the puborectalis muscle

distension of a haustrum with feces stimulates it to contact. What is the purpose of these contractions?

they churn and mix the residue, promotes water and salt absorption and pass the residue distally to another haustrum

the plasma membrane of the enterocytes have _____ ____ that absorb monosaccharides as soon as the brush border enzymes release them

transport proteins

The ascending colon makes a 90* turn at the right colic (hepatic) flexure near the right lobe of the liver and becomes the _______ colon

transverse

the large intestine takes 36-48 hours to reduce the residue of a meal to feces, with the residue spending the greatest time (about 24 h) in the _______ ______

transverse colon

the rectum has three infoldings called ______ _____ _____ (rectal valves) which enable it to retain feces while passing gas

transverse rectal folds

mass movements occur especially in the ______ to _______ colon, often within an hour after breakfast

transverse, sigmoid

within the enterocytes, FFAs and monoglycerides are transported into the smooth ER and resynthesized into ______

triglycerides

true or false after a high carbohydrate meal, solvent drag absorbs two to three times as much glucose as the SGLT

true

true or false chemical digestion and nutrient absorption are essentially finished by the time food residue leaves the small intestine and enters the cecum

true

true or false proteases (peptidases) - enzymes that digest proteins - are absent in the saliva but begin work in the stomach

true

true or false the intrinsic defecation reflex is relatively weak and usually requires the action of the parasymphatetic defecation reflex

true

true or false vitamins are absorbed unchanged

true

true or false some FFAs enter the blood capillaries, but chylomicrons are too large to penetrate the endothelium

true they are taken up by the lacteal into the lymph.

the external anal sphincter and external _____ sphincter are controlled together by inhibitory signal form the brainstem. As this inhibition is released, defecation is usually accompanied by urination

urethral

unlike veins in the limbs, hemorrhoidal veins lack ____, making them particulary subject to distension and pooling.

valves

inside the enterocyte, most fructose is converted to glucose. glucose, galactose and small amount of remaining fructose are then transported out of the base of the cell by facilitated diffusion and absorbed by the blood capillaries of the ______

villus

______ is secreted in repsonse to blood calcium levels it stimulates the kidneys to synthesize vitamin D from precursors made by the epidermis and liver

PTH

water-soluble vitamins ___ and __ are absorbed by simple diffusion

B complex and C

some bacteria synthesize vitamins ____and _____ which are absorbed by the colon

B, K

chloride ions are actively transported in the distal ileum that exchanges them for ________ ion. reversing the chloride-______ exchange that ocurs in the stomach

bicarbonate, chloride-bicarbonate

micelles are made in the liver and consist of 20-40 _____ ____ molecules aggregated with their hydrophilic side groups facing outward and their hydrophobic steroid rings facing inward

bile acid

in the duodenum, calcium is absorbed by the transcellular route where it bind to a cytoplasmic protein called ______

calbindin

what free calcium there is in the cytoplasm is pumped out of the basal side of the cell by active transport using the enzyme ______-______ as well as a sodium-calcium antiport

calcium-ATPase

in the small intestine, the pancreatic enzymes trypsin and chymotrypsin take over protein digestion by hydrolyzing polypeptides into even shorter oligopeptides these are then taken apart one amino acid at a time by three more enzymes. what are the three enzymes?

carboxypeptidase (a pancreatic secretion) aminopeptidase (a brush border enzyme) dipeptidase (a brush border enzyme)

bile phospholipids and ______ diffuse into the center of the micelle to form its core

cholesterol

the golgi complex combines the trigylcerides with a small amount of cholesterol and coats the complex with a film of phosphoplipids and protein, forming droplets called _______

chylomicrons

where the anal canal terminates at the anus the mucosa forms longitudinal ridges called anal ______ with depressions between them called anal _____

columns, sinuses

______ occurs when fecal movement is slow and too MUCH water is reabsorbed and the feces becomes hardened. *this can result from lack of dietary fiber, lack of exercise, emotional upset or long term laxative abuse

constipation