Intestines

Question 1

Plicae circulares

Answer 1

Mucosal folds covering the luminal (inner) surface

Question 2

Duodenum

Answer 2

. Secondarily retroperitoneal 
. Adjacent to the pylorus
. Thickness of 12 fingers
. C-shaped
. Cradles the head of the pancreas 
. Sup. Portion, descending portion, horizontal portion, ascending portion

Question 3

Sup. Portion of duodenum

Answer 3

. Has mesentery, more mobile
. Has smooth wall area of duodenal cap or bulb
. Plicae circulares begin 3-5cm from pylorus

Question 4

Duodenal ulcers

Answer 4

. Post wall of sup. Part of the duodenum near the pylorus

. Can lead to peritonitis if stomach contents enters peritoneal cavity

Question 5

Descending portion of duodenum

Answer 5

. Courses inf. To the right of L1-3 vertebrae
. Located parallel and to the right of the IVC
. Contains combined openings of bile duct and pancreatic ducts
. Major duodenal papilla w/ ostium: assoc. w/ chief or moan pancreatic duct and bile duct forming hepatopancreatic ampulla
. Minor duodenal papilla w/ ostium: assoc. w/ accessory pancreatic duct

Question 6

Horizontal portion of duodenum

Answer 6

. Crosses lower part of L3 body

. Sup. Mesenteric a. Arises above this

Question 7

Duodenum ascending portion

Answer 7

. Ascends lat. to L2-3 vertebrae
. Located on the L side of the abdominal
. Turns ventrally to be continuous w/ jejunum at duodenal-jejunal flexure
. Recesses and fossae that can be possible sites for gut herniation

Question 8

Suspensory ligament of duodenum

Answer 8

. Ligament of Treitz
. Fibromuscular band attached at flexure
. Attaches sup. To crus of diaphragm

Question 9

Recesses in descending portion of duodenum

Answer 9

. Sup. Duodenal fold/recess: next to flexure
. Inf. Duodenal fold/recess: ant. To angle btw horizontal and ascending portions of duodenum
. Retroduodenal recess: post. To ascending portion
. Paraduodenal fold/recess: left of duodenum, covers, inf. Mesenteric v. And L colic a.

Question 10

Jejunum

Answer 10

. Intraperitoneal
. No good demarcation from ileum (2/5 of combined length of jejunum and ileum)
. Frequently empty
. Wider diameter
. Thicker walls
. Redder from more vasculature
. Plicae circulares more prominent
. Blood vessels in mesentery (1-2 layers of arcades, long vasa recta)
. Features most prominent at proximal end

Question 11

Ileum

Answer 11

. Intraperitoneal 
. Features most prominent at distal end 
. Narrower, thinner, paler
. Small/absent plicae circulares
. Inc. mesenteric fat
. Blood vessels in mesentery (4-5 layers arcades, short Vasa recta)
. Peyer’s patches 
. Meckel’s diverticula

Question 12

Peyer’s patches

Answer 12

. Submucosal aggregates of lymph tissue along antimesenteric border

Question 13

Meckel’s diverticulum

Answer 13

. Common malformation
. Finger-like blind pouch remnant of embryonic Vitelline duct
. 2% individuals 2” long 2 feet from iliocecal junction
. Mimic appendix symptoms if inflamed

Question 14

Mesentery

Answer 14

. Fan shaped double layer peritoneum containing blood vessels, nerves, lymph
. Short root: 15 cm running obliquely (sup to inf, left to right) across post. A nominal wall from duodenal-jejunum flexure to iliocecal junction
. Long border: 6-7m at point of attachment to jejunum and ileum

Question 15

Large intestine distinct surface characteristics

Answer 15

. Teniae coli: outer longitudinal muscle layer incomplete, forms 3 equally spaced bands
. Haustra or sacculation: teniae coli 1/6 shorter than rest of colon so gut wall bulges out
. Epiploic appendices: fat-filled appendages

Question 16

Inner surface of large intestine

Answer 16

. Semilunar mucosal folds that run from teniae coli to teniae coli

Question 17

Regions of large intestine

Answer 17

. Cecum w/ appendix 
. Ascending colon 
. Transverse colon
. Descending colon
. Sigmoid colon 
. Rectum 
. Anal canal

Question 18

Cecum

Answer 18

. Blind pouch 6-7cm
. Secondarily retroperitoneal
. Ileum enters cecum at ileocecal orifice

Question 19

Appendix

Answer 19

. Intraperitoneal (mesentery called mesoappendix)
. 2-20 cm long, avg 8 cm
. Appendicular orifice
. Opening 3 cm inf. To ileocecal valve
. Root is only fixed point
. Usually retrocecal (64%) or pelvic rim (32%)
. Frequently inflamed

Question 20

McBurney’s point

Answer 20

. Junction of lat. and middle thirds of line joining ASIS to umbilicus
. Produces max abdominal pain in appendicitis

Question 21

Ascending colon

Answer 21

. Secondarily retroperitoneal
. From cecum to R colic (hepatic) flexure
. Narrower than cecum

Question 22

Transverse colon

Answer 22

. Intraperitoneal
. Largest and most movable part of large intestine
. Courses from R colic flexure to L colic (splenic) flexure
. Mesenteric attachments: post. To transverse mesocolon (courses across duodenum and pancreas) and ant. To gastrocolic ligament of greater omentum

Question 23

Left colic flexure

Answer 23

. More sup. And post. Than right colic flexure

. Attached to diaphragm by phrenicocolic ligament

Question 24

Descending colon

Answer 24

. Secondarily retroperitoneal
. From L colic flexure to sigmoid colon
. Narrowest part of colon

Question 25

Sigmoid colon

Answer 25

. Intraperitoneal . S-shaped loop . V-shaped Mesenteric attachment running along post. Abdominal wall and pelvis (sigmoid mesocolon)

Question 26

Preganglionic sympathetic fibers of intestines

Answer 26

. From sympathetic chain | . Synapse in sup. Or inf. Mesenteric (preaortic) ganglia

Question 27

Postganglionic sympathetic fibers in intestines

Answer 27

. From sup. Mesenteric ganglia: follow blood vessels to midgut organs (distal 1/2 duodenum through prox. 2/3 transverse colon) . From inf. Mesenteric ganglia: follow blood vessels to hindgut (distal transverse colon to rectum)

Question 28

Sympathetic effect on intestines

Answer 28

. Dec. motility and secretion, vasoconstricts, constricts sphincters . Visceral sensory afferents convey pain

Question 29

Parasympathetic fibers in intestine

Answer 29

. Preganglionic: vagus to GI tract up to L colic flexure, sacral (pelvic splanchnics) to rest of organs . Synapse in wall of gut (myenteric/submucosal plexuses) . Short postganglionic fibers

Question 30

Parasympathetic effects on intestine

Answer 30

. Inc. motility secretion, vasodilates, dilates sphincters | . Visceral sensory afferents conveys senses of nausea and distension

Question 31

Sup. Mesenteric a.

Answer 31

. Unpaired, from abdominal aorta (L1) . Lymph and nerve plexus at base . Supplies SI, cecum, appendix, ascending colon and R 2/3 of transverse colon

Question 32

Sup. Mesenteric a. Branches

Answer 32

``` . Inf. Prancreeaticoduodenal a. . Intestinal a (15-28 in mesentery to jejunum and ileum) forming arcades and vasa recta . Ileocolic a. . R colic a. . Middle colic. A. ```

Question 33

Ileocolic a. Branches

Answer 33

. Cecal branches . Colic branch (anastomoses w/ descending branches of R colic a.) . Ileal branch (anastomoses w/ ileal branches) . Appendicular branch

Question 34

Percentage of ileocolic aa. That arise from common stem w/ R colic a.

Answer 34

40%

Question 35

R colic a.

Answer 35

. Descending branch (anastomoses w/ colic branch of ileocolic a.) . Ascending branch (anastomoses w/ middle colic a.)

Question 36

Inf. Mesenteric a.

Answer 36

. Unpaired from abdominal aorta (L3) above bifurcation . Lymph and nerve plexus at base . Supplies left 1/3 transverse colon, descending colon, sigmoid colon, rectum

Question 37

Inf. Mesenteric a. Branches

Answer 37

. L colic a. . Sigmoidal aa. (2-3) . Sup. Rectal a.

Question 38

Left colic artery branches

Answer 38

. Ascending branch: anastomoses w/ L branch of middle colic a. . Descending branch

Question 39

Sigmoidal aa.

Answer 39

. Ascending branch | . Descending branch

Question 40

Sup. Rectal a. And branches

Answer 40

. Inf. Continuation of inf. Mesenteric a. After last sigmoidal branch is given off

Question 41

Marginal artery of Drummond

Answer 41

. Extensive anastomoses of branches of sup. And inf. Mesenteric aa. . Patent arch around large intestines

Question 42

Veins of intestines

Answer 42

. Sup. Mesenteric v, joins splenic v. To form portal v. | . Inf. Mesenteric v. Terminates in splenic v. (60%) or sup, mesenteric v. (40%)

Question 43

Lymphatic trunks of intestines

Answer 43

. Abdominal (lumbar, intestinal, descending thoracic) converge to form cisterna chyli

Question 44

Cisterna chyli

Answer 44

. Collects lymph from lower half of body | . Beginning of thoracic duct

Question 45

Thoracic duct

Answer 45

. All lymph from lower half of body | . Enters venous system at convergence of L internal jugular and L subclavian vv.

Question 46

T/F infants w/ pets have high diversity of microbes in gut leading to inc. gut. Immunity

Answer 46

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