Digestive System 2

Front 1

Expanded part of digestive tube lying beneath diaphragm

Back 1

Stomach

Front 2

General fxn of the stomach is to:

Back 2

Receive bolus of macerated food from esophagus which produces chyme by mixing and partial digestion by small intestine

Front 3

3 histological regions of stomach include

Back 3

Cardiac
Pyloric
Fundic

Front 4

near esophageal orifice & contains cardiac glands

Back 4

Cardiac region

Front 5

proximal to pyloric sphincter & contains pyloric glands

Back 5

Pyloric region

Front 6

largest part of stomach found between cardiac and pyloric regions & contains fundic or gastric glands

Back 6

Fundic

Front 7

Gastric Mucosa includes:

Back 7

Rugae, gastric pits, and simple columnar epithelium lining surface & gastric pits

Front 8

________are longitudinal folds composed of mucosa & submucosa present on inner surface of EMPTY stomach
Prominent in narrower regions; disappears when stomach fully extended and DOES NOT alter total surface area; accommodates expansion & filling of stomach

Back 8

Rugae

Front 9

________are openings in mucosal surface; glands open into bottom of gastric pits

Back 9

Gastric pits (foveolae)

Front 10

Lots of mucinogen granules; occupies most of cell volume & appear clear (washed out) w/ H&E staining (mucinogene lost); stains intensely with toluidine blue &/or PAS!!!!

Back 10

surface mucous cells

Front 11

Surface mucous cells in stomach also have _________________________

Back 11

Prominent, elongated nucleus, golgi, small amt of rER basal to mucous granules - gives light basophilic staini

Front 12

Secretion of mucous cells in stomach forms__________

Back 12

Mucous secretion described as visible mucus – cloudy appearance; thick, viscous, gel-like coat that adheres to epithelial surface which provides protection because of lots of biocarbonate

Front 13

Mucous cells have no function in
absorption except for

Back 13

water, salts, & lipid-soluble drugs alcohol & certain drugs (aspirin) ------lamina propria by damaging

Front 14

Simple, branched, tubular glands; known as _______extend from bottom of gastric pits to muscularis mucosa; several glands open into single pit

Back 14

Fundic (gastric) glands of gastric mucosa

Front 15

Fundic (gastric) glands of gastric mucosa are composed of 5 different cell types

Back 15

Mucous neck cells
Chief cells
Parietal (oxyntic) cells
Enteroendocrine cells
Undifferentiated cells

Front 16

________ is located b/t gastric pit & gland and is site of cell replication

Back 16

Isthmus

Front 17

2 distinctions about cell migration are upward and downward

Back 17

cells migrate upward become mucous surface cells (lifespan is 3 – 5 days): cells shed into stomach lumen
cells migrate downward and differentiate into chief, parietal, mucous neck & enteroendocrine cells

Front 18

Cells of gastric glands produce gastric juice (~2L/day) containing:

Back 18

water and electrolytes

Front 19

Hydrochloric acid (HCl) – produced by ____________ is 150 – 160 mM resulting in pH of <1.0 – 2.0

Back 19

parietal cells

Front 20

___________initiates digestion of protein (promotes acid hydrolysis); converts inactive pepsinogen to pepsin which destroys most of bacteria; H. pylori survives

Back 20

Hydrochloric acid (HCl)-produced by parietal cells

Front 21

Helicobacter pylori and ulcer formation

Back 21

Helicobacter pylori contains urease which hydrolyzes urea. This creates protective basic “ammonia cloud” which survives the acidic stomach Thus H. pylori releases cytotoxic proteases which damages epithelial wall. This process results in bleeding ulcer

Front 22

___________is a proteolytic enzyme produced by chief cells
Hydrolyzes proteins into small peptides by splitting internal peptide bonds

Back 22

Pepsin

Front 23

Pepsin is converted from________ by HCl at pH < 5.0

Back 23

pepsinogen

Front 24

_______is acid-protective coating for stomach and is secreted by several types of mucus-producing cells

Back 24

Mucus

Front 25

Mucus traps _________ which is important for maintenance of neutral pH; contributes to physiologic gastric mucosa barrier; physical barrier

Back 25

bicarbonates

Front 26

________ is vitamin B12-binding glycoprotein that is essential for absorption (in distal part of ileum) of vitamin B12

Back 26

intrinsic factor

Front 27

lack of intrinsic factor most common cause for_________ deficiency

Back 27

vitamin B12

Front 28

__________are located in neck region of fundic gland; usually intersparsed with parietal cells
2. Shorter than surface mucous cells & less mucinogen; spherical nucleus
3. Secrete soluble mucus upon vagal stimulation, therefore no secretion in resting stomach

Back 28

Mucous neck cells (lifespan ~6 days):

Front 29

____________ are protein secreting cells that secrete pepsinogen & weak lipase
2. H&E appearance: basophilic basal region (lots of rER) & apical region can have light eosinophilic staining due to secretory (zymogen) granules
3. Secretory granules - called zymogen - contain enzyme precursors

Back 29

Chief cells (lifespan 60 – 90 days):

Front 30

Pepsinogen becomes__________ upon contact with gastric juice

Back 30

pepsin

Front 31

_________secrete HCl & intrinsic factor and are located in neck of fundic glands among mucous neck cells & in deeper regions of gland; most numerous in upper and middle regions of neck

Back 31

Parietal (oxyntic) cells (lifespan of 150 – 200 days):

Front 32

H & E appearance of parietal cells

Back 32

Large, triangular –shaped cells; spherical nucleus; sometimes appears binucleate !!!!; apex directed toward lumen of glands
Cytoplasm stains with eosin and other acidic dyes !!!!!(PINK)

Front 33

__________is reservoir of plasma membrane containing active proton pumps;

Back 33

Tubulovesicular membrane system (adjacent to canaliculi)

Front 34

Durung active secretion the number of microvilli on canaliculi ________and tubulovesicular system__________ or disappears – tubulovesicular system inserts into canaliculi which results in increase in surface area & number of proton pumps for acid production

Back 34

increases
decreases

Front 35

Substances that activate HCl secretion:

Back 35

Gastrin – GI peptide hormone; secreted in response to a meal; major player for parietal cell stimulation; stimulates gastric acid secretion; release of gastrin inhibited by H+ in stomach lumen (negative feedback)
b. Histamine H2
c. Acetylcholine M3

Front 36

Steps in HCl production( see concept map also)

Back 36

1. H2O enters cell by osmosis disassociates into H+ & OH-
2.) CO2 diffuses across basal lamina from blood capillaries
3.) CO2 + 2OH- (& carbonic anhydrase) form H2CO3 (carbonic acid)
4.) H2CO3 → H+ and HCO3-
5.) H+ ions transported from cytoplasm into lumen of canaliculus by H+/K+ ATPase proton pump; K+ pumped out of lumen (exchange of K+ for H+)
6.) K+ and Cl- transported from cytoplasm into lumen of canaliculus via activation of K+ and Cl- channels (uniporters) in plasma membrane
7.) Formation of HCl

Front 37

Cells thought to sample contents of gland lumen and release hormones on basis of information and located in all levels of fundic gland but more concentrated at base

Back 37

Enteroendocrine cells (lifespan 60 – 90 days) also known as enterochromaffin, argentaffin and argyrophil cells due to staining with salts, silver and chromium.

Front 38

Primary hormone secretions of enteroendocrine cells include..........

Back 38

gastrin, CCK(cholecytokinin), secretin, motilin, GIP( gastric inhibitory peptide)

Front 39

synthesized in stomach and stimulates gastric acid secretion

Back 39

gastrin

Front 40

synthesized in small intestine and stimulates gallbladder contraction, pancreatic enzyme and bicarbonate ion secretion, and pancreatic growth. It inhibits gastric emptying

Back 40

CCK

Front 41

synthesized in small intestine and stimulates pancreatic enzyme and bicarbonate ion secretion and pancreatic growth. It inhibits gastric acid secretion

Back 41

secretin

Front 42

synthesized in small intestine and stimulates gastric motility and intestinal motility

Back 42

motilin

Front 43

synthesized in small intestine and stimulates insulin release. It inhibits gastric acid secretion

Back 43

GIP (gastric inhibitory peptide)

Front 44

located in narrow region of stomach (cardia) surrounding esophageal orifice and secrete mucous - (component of gastric juice) which aids in protection of epithelium against gastric reflux

Back 44

Cardiac glands of gastric mucosa:

Front 45

located in pyloric antrum (region between fundus and pylorus)
and branched, coiled, tubular glands w/ relatively wide lumen which empty into deep gastric pits that occupy ~ ½ of the mucosa thickness

Back 45

Pyloric glands of gastric mucosa (deep pits is distinguishing feature for pyloric stomach!!!!

Front 46

Muscularis externa of stomach
includes 3 layers of smooth muscle which are________,_________ and ___________.

Back 46

1. Inner oblique
2. Middle circular – poorly developed in periesophageal region
3. Outer longitudinal – mostly missing from anterior and posterior stomach surfaces

Front 47

located between muscle layers & innervate these muscle layers

Back 47

Myenteric (Auerbach’s) plexus

Front 48

Small intestine is the longest component of GI tract (over 6 m) and contains 3 anatomic regions:

Back 48

1. Duodenum – first, shortest and widest part; begins at pylorus of stomach; ends at duodenojejunal junction
2. Jejunum – begins at duodenojejunal junction and constitutes upper 2/5; gradually changes morphologic characteristics to become ileum
3. Ileum – continuation of jejunum; constitutes lower 3/

Front 49

______________is the principal site for digestion & absorption and is delivery site for pancreatic enzymes & bile

Back 49

Small intestine

Front 50

__________ are intestinal absorptive cells that have apically localized microvilli; enzymes localized to glycocalyx (e.g., disaccharidases and dipeptidases) – complete breakdown of sugars & proteins to monosaccharides & amino acids Site of reabsorption of water and electrolytes

Back 50

Enterocytes

Front 51

__________are permanent transverse folds that contain a core of submucosa and increase absorptive surface area
also known as valves of Kerckring

Back 51

Plicae circulares (circular folds)

Front 52

________ are finger & leaflike projections of mucosa that extend from mucosal surface for 0.5 – 1.5 mm into lumen
They completely cover surface of small intestine and increase absorptive surface area

Back 52

Villi

Front 53

several thousand ___________are closely packed on surface of enterocytes and are
major amplification of luminal surface (i.e., increase absorptive surface area)

Back 53

Microvilli

Front 54

at least 5 types of cells in mucosa of small intestine........

Back 54

1. Enterocytes – absorption
2. Goblet cells – mucus secretion
3. Paneth cells – antimicrobial secretions
4. Enteroendocrine cells – paracrine/endocrine hormones
5. M (microfold) cells – cover lymphatic nodules

Front 55

___________ are simple, tubular glands extending from muscularis mucosa and opening at luminal surface at base of villi

Back 55

Intestinal glands (crypts of Lieberkuhn)

Front 56

_________are located at base – restricted to lower ½ of gland

Back 56

Stem cells

Front 57

________ are (absorptive cells) that divide during upward migration from stem cell pool

Back 57

Goblet & enterocytes

Front 58

_____________divide once before differentiating; migrate w/ goblet & enterocytes (absorptive cells) but at slower rate

Back 58

Enteroendocrine cells

Front 59

___________do not migrate; remain in base of gland near stem cells; lifespan ~ 4 wks; replaced by differentiation of nearby committed cell;

Back 59

Paneth cells

******Paneth cells DO NOT divide

Front 60

_________ are olumnar cells w/ basally positioned nucleus and apical microvilli whose primary function is absorption. They also secrete glycoprotein enzymes that are inserted into apical plasma membrane and maintain appropriate liquid state of chyme

Back 60

Enterocytes of small intestine

Front 61

___________produce mucus and appear empty by H&E
Their number present increases from duodenum to terminal part of ileum

Back 61

Goblet cells

Front 62

__________are found @ base of intestinal glands
Their LM & EM appearance: basophilic basal cytoplasm, supranuclear golgi (on top of nucleus) & large, intensely eosinophilic, refractile apical secretory granules – identifying feature !!!!!

Back 62

Paneth cells

Front 63

Paneth cells secret _________,________ and ________APICALLY

Back 63

1. lysozyme (antibacterial enzyme – digests cell walls of certain grps of bacteria)
2. α-defensins (homologs of peptides that fnx as mediators in cytotoxic T cells)
3. TNF alpha

Front 64

___________can also phagocytose certain bacteria and protozoa – role in regulating normal bacterial flora

Back 64

Paneth cells

Front 65

__________are similar to those in stomach
They are concentrated in lower portion of intestinal gland but migrate slowly up at all levels of villus
Contain same peptide hormones as found in stomach

Back 65

Enteroendocrine cells

Front 66

Enteroendocrine cells contain same peptide hormones as found in stomach including
a. Cholecystokinin (CCK) –  pancreatic & gallbladder activity and HCO3- secretion by pancreas (neutralize H+ in intestinal lumen); inhibits gastric secretory function & motility (emptying)
b. Secretin – same function as CCK;  HCO3- secretion; inhibits H+ secretion by gastric parietal cells
c. Glucose-dependent insulinotropic peptide (GIP) – stimulates insulin release in pancreas
d. Glucose-dependent insulinotropic peptide (GIP) – nitiates gastric and intestinal motility

Back 66

Cholecystokinin, Glucose-dependent insulinotropic peptide (GIP), Motilin and Secretin

Front 67

___________increases pancreatic & gallbladder activity and HCO3- secretion by pancreas (neutralize H+ in intestinal lumen); inhibits gastric secretory function & motility (emptying)

Back 67

Cholecystokinin (CCK)

Front 68

same function as CCK; increases HCO3- secretion; inhibits H+ secretion by gastric parietal cells

Back 68

Secretin

Front 69

stimulates insulin release in pancreas

Back 69

Glucose-dependent insulinotropic peptide (GIP)

Front 70

__________nitiates gastric and intestinal motility

Back 70

Motilin