Small Intestine

Question 1

What are the general functions of the small intestine?

Answer 1

digestion
absorb nutrients
produce intestinal hormones using DNES cells

Question 2

What are the three surface adaptations of the small intestine that increase the surface area?

Answer 2

plicae circulares
villi
microvilli

Question 3

What is plicae circulares?

Answer 3

permanent folds affecting the mucosa and submucosa

Question 4

Where are the plicae circulares found?

Answer 4

duodenum, jejunum and proximal ileum

Question 5

Where are microvilli found?

Answer 5

on the luminal cell surface

Question 6

What is the surface epithelium of the mucosa of the small intestine?

Answer 6

simple columnar

Question 7

What other types of cells are found in the mucosa of the intestine?

Answer 7

surface absorptive cells, goblet cells, DNES cells, regenerative cells, paneth cells, M cells

Question 8

What is the function of surface absorptive cells of the mucosa of the small intestine? what do they contain?

Answer 8

absorb water and nutrients, terminal digestion in glycocalyx

contain microvilli

Question 9

What is glycocalyx?

Answer 9

cell produce the enzymes and absorb the monosaccharides and peptides created

Question 10

Where are goblet cells located?

Answer 10

most in ileum, least in duodenum

Question 11

What types of DNES cells are found in the small intestine?

Answer 11

Type I, Type K and Type S

Question 12

What do Type I DNES cells do?

Answer 12

produce CCK

Question 13

What does CCK do?

Answer 13

stimulates gallbladder contraction and pancreatic secretion of enzymes from serous acini

Question 14

What do type K DNES cells do?

Answer 14

produce Gastric Inhibitory peptide (GIP)

Question 15

What does GIP do?

Answer 15

inhibits HCl release

Question 16

What do type S DNES cells do?

Answer 16

produce secretin

Question 17

What does secretin do?

Answer 17

stimulates pancreas secretion of bicarbonate from pancreatic ducts
also inhibit HCl release and movement of chyme into small intestines

Question 18

What does bicarbonate do?

Answer 18

buffer’s chyme

Question 19

Where are regenerative cells found?

Answer 19

crypts (intestinal glands)

Question 20

Where are paneth cells found?

Answer 20

base of crypts (intestinal glands)

Question 21

What is the function of paneth cells?

Answer 21

to produce lysozymes

Question 22

Where are M cells located?

Answer 22

ileum epithelium over Peyer’s patches

Question 23

What is the cellular structure of M cells?

Answer 23

they contain large intracellular pockets that are fairly open to LP
sample foreign antigens in gut lumen and transfer antigens to lymphocytes and dendritic cells that have entered the M cell pockets

Question 24

What do M cells do?

Answer 24

promote humoral immunity

maintain appropriate gut flora

Question 25

What is a result of humoral immunity from M cells?

Answer 25

causes plasma cells to produce IgA which is transferred to epithelial cells (enterocytes) and released into the gut lumen

Question 26

What makes up the lamina propria of the mucosa of the small intestine?

Answer 26

loose areolar CT

Question 27

Where is the LP found?

Answer 27

villus core and bordering the intestinal glands

Question 28

What is contained within the villus core?

Answer 28

lacteals, vascular components and some longitudinal smooth muscle

Question 29

What are lacteals? What do they do?

Answer 29

lymphatic capillaries | absorp most lipids

Question 30

Why is smooth muscle important in the lamina propria of the gut?

Answer 30

if it is irritated then the muscle contracts and the villi shorten, which can lead to nutrient deficiencies if this is prolonged

Question 31

Describe the muscularis mucosae of the mucosa of the small intestine.

Answer 31

thin but present; connects to the smooth muscle in the villi

Question 32

What makes up the submucosa of the small intestine?

Answer 32

dense fibroelastic CT and large blood vessels (very vascular)

Question 33

What is the significant structure found in the submucosa of the duodenum?

Answer 33

duodenal (brunner) glands

Question 34

What are Brunner glands?

Answer 34

seromucous glands that primarily produce alkaline mucus, but also produce urogastrone

Question 35

Why do Brunner glands produce alkaline mucus?

Answer 35

to neutralize chyme

Question 36

Why do Brunner glands produce some urogastrone?

Answer 36

to inhibit HCl secretion and increase mitosis of epithelial cells

Question 37

What are the significant structures of the jejunum?

Answer 37

there are none

Question 38

What are the significant structures of the ileum?

Answer 38

Peyer's patches and submucosal (Meissner's) plexus

Question 39

What are Peyer's patches in the ileum?

Answer 39

groups of regularly occuring large lymph nodules

Question 40

What is the submucosal plexus there for? Where is it?

Answer 40

parasympathetic innervation to influence mucosa | located close to circular muscle in muscularis externa

Question 41

What is the pattern for the muscularis externa?

Answer 41

normal pattern (inner circular, outer longitudinal)

Question 42

Where is the Myenteric (Auerbach) plexus found?

Answer 42

in the muscularis externa between the circular and longitudinal muscle layers

Question 43

What is the function of the myenteric (Auerbach) plexus in the muscularis externa of the small intestine?

Answer 43

stimulate muscularis externa for peristalsis

Question 44

Where is serosa found?

Answer 44

all of jejunum and ileum as well as the first and last cm of the duodenum

Question 45

Where is adventita found?

Answer 45

vertical (descending) portion of the duodenum

Question 46

Where is the ileocecal valve found?

Answer 46

between ileum and cecum of colon

Question 47

Is the ileocecal valve an anatomical or physiological sphincter?

Answer 47

both