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digestion Flashcards

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1
Q

List three sensory structures involved in mastication reflexe

A
  • proprioceptors in the temporomandibular joint
  • proprioceptors in the muscles of mastication
  • proprioceptors in the periodontal ligaments
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2
Q

Masticationreflexesareintegratedinthe________

A

medulla oblongata

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3
Q

Twoeffectorsofmasticationreflexesinclude_______________________and
_________________________.

A

temporalis muscle and masseter muscle

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4
Q

Listthreecomponentsofsaliva(inadditiontowater)andthefunctionofeach.

A

amylase, an enzyme that digests starch

  • electrolytes, like Na+, function not completely understood
  • mucin, protein that absorbs water and acts as a lubricant
  • also others
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5
Q

Outlinethebasicmechanismofdeglutition

A
  • voluntary contraction of tongue muscles pushes the bolus upwards and activates pressure receptors in the pharynx
  • sensory impulses are transmitted along the glossopharyngeal nerve to the medulla oblongata where the swallowing reflex is triggered
  • pharyngeal constrictor muscles contract pushing the bolus of food down the pharynx
  • the posterior part of the epiglottis moves downwards to cover the glottis and the bolus slides over it into the upper part of the esophagus
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6
Q

Describe the movement of a bolus down the esophagus: the main structures and
forces involved and how they are controlled (3

A
  • the upper esophageal sphincter relaxes to allow the bolus to enter the esophagus
  • the bolus moves down the esophagus because of a wave of peristalsis
  • peristalsis is partly the result of local reflexes and partly the result of parasympathetic reflexes controlled by the medulla oblongata
  • the lower esophageal sphincter relaxes for the bolus to enter the stomach
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7
Q

Name a medical procedure that eliminates the swallowing reflex.

A

-deep anesthesia

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8
Q

cribe the characteristics of mixing waves in the stomach.

A
  • peristatic waves
  • mostly in body of stomach
  • move back and forth
  • about 3 per minute
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9
Q

Ingesta spends about _____________ (time) in the stomach.

A

2-4 hours

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10
Q

Describe the secretions of the stomach and the digestion that occurs there (2
marks).

A

mucus, hydrochloric acid, pepsinogen and water

-proteins are converted to peptides by pepsin

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11
Q

Label a stomach showing the general positions of cardiac, oxyntic and pyloric glands
and indicate which area produces gastrin and which area produces acid and proteins
(2 marks).

A
  • cardiac region is near the opening to the esophagus - its wall contains glands that produce mucus
  • the pyloric region is near the opening to the duodenum-its wall contains glands that produce mucus and the hormone gastrin
  • the body is between the pyloric and cardiac regions-its wall contains oxyntic glands that produce hydrochloric acid and pepsinogen, as well as mucus
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12
Q

Describe the roles of enterochromaffin cells, chief cells and parietal cells and how
each is regulated.

A
  • enterochromaffin cells produce histamine in response to stimulus by gastrin
  • chief cells secrete pepsinogen when stimulated by acetylcholine from the vagus nerve
  • parietal cells secrete hydrochloric acid when stimulated by either the vagus nerve or histamine from enterochromaffin cells
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13
Q

intrinsic factor is produced in the ________________________; its function is to
____________________________.

A

parietal cells of oxyntic glands…promote the absorption of vitamin B12 from the intestines

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14
Q

Describe the mechanism for acid secretion by cells of the stomach and list two
chemicals that stimulate the process (4 marks).

A
  • parietal cells contain the enzyme carbonic anhydrase the catalyzes the conversion of carbon dioxide to bicarbonate ion and hydrogen ion
  • bicarbonate diffuses out of the cell into the blood, in exchange for chloride ion
  • hydrogen ion is pumped out of the cell into the lumen of the stomach, in exchange for potassium ion
  • histamine and the neurotransmitter acetylcholine stimuate acid production
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15
Q

Explain how mixing waves are generated in the stomach and list two factors that
increase their activity (3 marks).

A
  • interstitial cells of Cajal act as a pacemaker and start the mixing waves as wall as conduct them through the stomach
  • they increase in response to stimuation by vagus nerve and the hormone gastrin
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16
Q

Describe two ways in which the rate of gastric emptying is regulated (2

A

any 2 of the following ways:

1) stimulation by vagus nerve
2) gastrin released by stomach
3) secretin released by the small intestine
4) cholecystokinin released by the small intestine

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17
Q

List two kinds of digestive processes that occur in the stomach and the enzymes
responsible.

A

1) conversion of protein to peptides by pepsin

2) coagulation of milk proteins in the stomach of infants by rennin

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18
Q

Describe the kinds of substances that are absorbed from the stomach and the
mechanism for this process.

A
  • water, osmosis

- lipid soluble substances such as alcohols, diffusion

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19
Q

Describe what each of the following is and its role in digestion.
a) bolus

A
  • a ball shaped piece of macerated food mixed with saliva

- it is size and consistency the enables it to be swallowed and propelled down the esophagus

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20
Q

b) gastrin

A

-a polypeptide hormone, produced by the stomach in response to the presence of food, that stimulates digestive processes in the stomach

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21
Q

c) pepsin

A

-an enzyme that is present in the stomach that converts proteins to polypeptides

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22
Q

d) chyme

A

-liquid ingesta that is formed in the stomach and propelled into the small intestine

23
Q

e) secretin

A

-a polypeptide hormone, is produced in the small intestine in response to the presence of nutrients, that stimulates digestive acttivities of the liver and pancreas

24
Q

f) cholecystokinin g) trypsin

A

-a polypeptide hormone, produced in the small intestine in response to the presence of nutrients, that stimulates digestive activities of the pancreas and movement of bile into the duodenum…..-an enzyme, produced by the pancreas, that converts proteins to peptides

25
Q

h) chymotrypsin

A

-an enzyme, produced by the pancreas, that converts proteins to peptides

26
Q

i) carboxypeptidase

A

-an enzyme, produced by the lining of the small intestine, that remains attached to the tips of microvilli and converts peptides to amino acids

27
Q

j) rennin

A

-an enzyme produced by the stomach’s of infants that catalyzes the coagulation of mild proteins

28
Q

k) amylase

A

-enzyme, produced by the pancreas as well as salivary glands, that catalyzes the conversion of starch into maltose and oligosaccharides

29
Q

m) maltase

A

-a brush border enzyme that catalyzes the conversion of maltose into glucose

30
Q

n) sucrose

A

-brush border enzyme that catalyzes the conversion of sucrose to glucose and fructose

31
Q

o) lactase

A

brush border enzyme that catalyzes the conversion of lactose to glucose and galactose

32
Q

p) aminopeptidase

A

-brush border enzyme (also called carboxypeptidase) that catalyzes the conversion of peptides to amino acids

33
Q

q) brushborderenzymes

A
  • enzymes produced by the cells that line the small intestine that remain attached to the outer surfaces of microvilli
  • convert small polymers (can’t be absorbed) to monomers (CAN be absorbed)
34
Q

r) enteric plexus

A

-branching network of nerves within the wall of the small intestine

35
Q

s) enterohepaticcirculation

A

-movement of bile salts from the liver into the lumen of the small intestine where they are absorbed into the blood and transported back to the liver

36
Q

t) hepatopancreatic sphincter

1

A
  • band of smooth muscle in pancreatic duct and bile duct where they join and enter the duodenum
  • controls the entry of bile and pancreatic juice into the small intestine
37
Q

u) mass movements

A

-infrequent (several times per day) peristaltic contractions of the smooth muscle of the distal colon that push feces into the sigmoid colon to trigger a defecation reflex

38
Q

v) interstitialcellsofCajal

A

specialized smooth muscle cells arranged as a scattered network in the wall of the stomach and intestines
-act as a pacemaker to initiate peristaltic contractions and transmit them through the digestive tract

39
Q

The major organ of chemical digestion and absorption is _________________

A

small intestine

40
Q

List three components of intestinal juice (in addition to water) and describe where
each is formed (2 marks).

A

1) bicarbonate is produced in the pancreas and the lining of the small intestine
2) mucous is produced by the glands of the stomach and small intestine
3) bile salts are produced by the liver

41
Q

Explain the difference between peristalsis and segmentation and name the organ in
which both activities are most common.

A
  • peristalsis is a contraction of smooth muscle that moves along the digestive tract in the aboral direction
  • segmentation refers to wave-like contractions of smooth muscle of the small intestine that alternate their direction and form the small intestine into many short segments
42
Q

Describe the mechanism by which each of the following substances is absorbed by the digestive system

a) K+
b) Na+
c) Ca+2

A

absorption is passive, occurring because of a concentration gradient

  • sodium is absorbed by active transport
  • sodium/potassium pumps in the basal membrane pump sodium out of the cells that line the small intestine
  • sodium is absorbed from the contents of the small intestine by transport proteins in the apical surface of the cells that transport sodium along with some other solute
  • Calcium moves from the ingesta into the cells that line the small intestine through calcium channels (the number of calcium channels is controlled by vitamin D)
  • calcium is actively transported from enterocytes into the blood by calcium pumpsiron is transported into enterocytes by divalent metal transporter, a transport protein that increases in response to anemaiiron is transported into enterocytes by divalent metal transporter, a transport protein that increases in response to anemai
43
Q

d) Fe

A

iron is transported into enterocytes by divalent metal transporter, a transport protein that increases in response to anemai

44
Q

Describe the form in which each of the following substances is absorbed by the
digestive system and the mechanism involved. a) carbohydrates
b) proteins
c) lipids
d) water

A
  • carbohydrates are absorbed as monosaccharides
  • glucose and galactose are transported with sodium and sodium is actively transported out of the enterocyte into the blood by the sodium/potassium pump
  • fructose is transported passively
  • proteins are transported as amino acids
  • amino acids are transported into the enterocyte along with sodium and sodium is transported out of the enterocyte and into the blood by the sodium/potassium pump
45
Q

c) lipids

d) water

A
  • lipids, as monoglycerides and fatty acids, diffuse into the enterocytes where they are converted to triglycerides and packaged as chylomicrons
  • chylomicrons enter the lymph through the lacteal
  • water is absorbed by osmosis (the concentration gradient is created by absorption of solutes by active transport)
46
Q

Name the two main components of bile (other that water) and describe the role of
each (2 marks).

A
  • bile salts are derivatives of cholesterol that function in the emulsification of lipids to assist in their absorption
  • conjugated bilirubin is a waste product of heme, associated with erythrocyte degradation
47
Q

he production of bile by the liver is controlled mainly by _____________.

A

the hormone secretin

48
Q

The release of bile by the gall bladder is controlled mainly by _____________

A

cholecystokinin

49
Q

List four components of pancreatic juice (other than water) (2 marks).

A
  • sodium bicarbonate
  • trypsin
  • amylase
  • lipase
50
Q

he production of pancreatic juice is controlled by ____________ and
_________________.

A

secretin,cholecystokinin

51
Q

Most of the water that enters the digestive tract is absorbed from the ____________
(region).

A

small intestine

52
Q

List four functions of the large intestine (2 marks).

A

1) temporary storage of excreta prior to defecation
2) provides a suitable environment for growth of bacteria
3) absorption substances produced by intestinal microflora including fatty acids and vitamin K
4) absorption of a small amount of water

53
Q

32)Explain how defecation is controlled (3 marks).

A
  • several times per day, mass movements result in movement of feces into the rectum
  • stretch receptors in the rectum are activated, sending impulses to the sacral spinal cord
  • reflex relaxation of the internal anal sphincter and contraction of the rectum can result in defecation
  • voluntary constriction of external anal sphincter can prevent reflex defecation and stretch receptor sensations will decrease with time
  • defecation can occur when voluntary contraction of abdominal muscles forces feces into the rectum and the external anal sphincter is voluntarily relaxed

biology final (5 decks)

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