[Anatomy] Abdominal Contents Ii

Front 1

midgut derivatives

Back 1

distal duodenum, jejunum, ilium, cecum, appendix, ascending colon, proximal two-thirds of transverse colon

Front 2

midgut blood supply / venous drainage / lymphatics

Back 2

superior mesenteric artery, superior mesenteric vein, superior mesenteric lymph nodes

Front 3

hindgut derivatives

Back 3

distal one-third of transverse colon, descending colon, sigmoid colon, rectum

Front 4

hindgut blood supply / venous drainage / lymphatics

Back 4

inferior mesenteric artery, vein, lymph nodes

Front 5

small intestine (parts, divisions)

Back 5

consists of duodenum, jejunum, and ileum; proximal half of duodenum: 1st/2nd parts are derived from foregut; distal half: 3rd/4th parts derived from midgut

Front 6

distal duodenum

Back 6

located in right upper quadrant; secondarily retroperitonial; horizontal (3rd) part, ascending (4th) part

Front 7

horizontal (3rd) part of duodenum

Back 7

located in right upper quadrant, secondarily retroperitoneal, superior messenteric vesels emerge superior to this part

Front 8

ascending (4th) part of duodenum

Back 8

2ndarily retroperitoneal, forms duodenojejunal flexure, marking duodenojejunal junction

Front 9

duodenojejunal flexure

Back 9

acute angle marking the duodenojejunal junction; marks the transition from the secondarily retroperitoneal duodenum to the intraperitoneal jejunum; supported by the suspensory muscle of the duodenum (ligament of Treitz)

Front 10

jejunum

Back 10

intraperitoneal (robust mesentery); central position in abdomen; prominent plicae circulares

Front 11

ileum

Back 11

intraperitoneal (robust mesentery); central position in abdomen; plicae circulares are sparse proximally and entirely absent distally; lymphatic nodules (Peyer’s patches); ends at ileocecal junction

Front 12

ileal (Meckel's) diverticulum

Back 12

1-2% occurrence; congenital; remnant of yolk stalk (embryonic connection between the yolk sac and developing gut); blind pouch on the antimesenteric side of ileum; typically ~50 mm from ileocecal junction; inflammation can produce pain similar to appendicitis

Front 13

suspensory muscle of duodenum

Back 13

(ligament of Treitz) supports duodenojujenul flexure, tethering it to diaphragm

Front 14

large intestine (description)

Back 14

consists of cecum, appendix, colon (ascending, transverse, descending, sigmoid), and rectum; includes both midgut and hindgut derivatives; the midgut/hindgut transition lies at the junction of the proximal two-thirds and distal one-third of the transverse colon

Front 15

features of large intestine

Back 15

teniae coli: three longitudinal bands of smooth muscle (not present on rectum); haustra: pouches between the teniae coli; omental (epiploic) appendices: fat

Front 16

cecum

Back 16

intraperitoneal; located in right lower quadrant; round pouch; ileocecal valve between ileum and cecum closes when cecum is distended

Front 17

appendix

Back 17

intraperitoneal (mesoappendix); located in right lower quadrant; typically retrocecal (but position can vary, e.g., may extend inferiorly into pelvis); worm-like appendage of the cecum; teniae coli converge at appendix; root of appendix lies at “McBurney’s point”

Front 18

McBurney's point

Back 18

1/3 of the way from the ASIS along a line from the ASIS to the umbilicus; location of appendectomy incision

Front 19

ascending colon

Back 19

secondarily retroperitoneal (short mesentery in ~25% of people); located in right lower/upper quadrants; extends superiorly along right side of abdominal cavity between the cecum and the right colic (hepatic) flexure; right paracolic gutter is just lateral to the ascending colon

Front 20

transverse colon

Back 20

intraperitoneal (transverse mesocolon; located in right upper and left upper quadrants; extends horizontally between the right colic flexure and left colic (splenic) flexure; left colic flexure typically sits at a higher level than the right colic flexure

Front 21

descending colon

Back 21

secondarily retroperitoneal (short mesentery in ~33% of people); located in the left upper and left lower quadrants; extends inferiorly along left side of abdominal cavity between the left colic flexure and the sigmoid colon; left paracolic gutter is just lateral to descending colon

Front 22

sigmoid colon

Back 22

intraperitoneal (sigmoid mesocolon); located in the left lower quadrant; extends from descending colon to rectum; S-shaped

Front 23

rectum

Back 23

primarily retroperitoneal; lacks teniae coli

Front 24

paracolic gutters

Back 24

conduits for the spread of fluid within the peritoneal cavity; right: just lateral to ascending colon, left: lateral to descending colon

Front 25

superior mesenteric artery

Back 25

midgut; arises from the abdominal aorta at L1 vertebral level, posterior to the pancreas; crosses the 3rd part of the duodenum anteriorly; branches into anterior & posterior inferior pancreaticoduodenal arteries; jejunal and ileal arteries; colic arteries

Front 26

Anterior & posterior inferior pancreaticoduodenal arteries

Back 26

branch from superior mesenteric artery; anastomose with anterior & posterior superior pancreaticoduodenal aa. from celiac trunk

Front 27

jejunal and ileal arteries

Back 27

branch from SMA; form anastomosing arcades that terminate in straight arteries (vasa recta); jejunum characterized by few arcades and long straight arteries; ileum characterized by multiple arcades and short straight arteries

Front 28

colic arteries

Back 28

contribute to the marginal artery (an anastomosing loop that parallels the colon); branches into ileocolic artery (br. into appendicular artery in mesoappendix), right colic artery, middle colic artery

Front 29

inferior mesenteric artery

Back 29

hindgut; arises from the abdominal aorta at L3 vertebral level; branches into left colic artery (contributes to marginal artery), sigmoid arteries (contributes to marginal artery); superior rectal artery (terminal branch of IMA)

Front 30

portal system in midgut/hindgut; portal-caval anastomoses

Back 30

midgut: SMV, hindgut: IMV; portal tributaries draining the colon communicate with the paired veins of the IVC, providing an alternative route in cases of portal hypertension

Front 31

superior mesenteric vein

Back 31

midgut; tributaries generally parallel the branches of the SMA; joins with splenic vein to form the portal vein

Front 32

inferior mesenteric vein

Back 32

hindgut; tributaries generally parallel the branches of the IMA; typically empties into splenic vein posterior to body of pancreas

Front 33

lymphatics of hindgut / midgut

Back 33

midgut derivatives: lymph drain to superior mesenteric lymph nodes then into the chyle cistern; hindgut derivatives: lymph drain to inferior mesenteric lymph nodes then into superior mesenteric or aortic lymph nodes

Front 34

midgut parasympathetic innervation

Back 34

Preganglionic CB: brain (CN X); Preganglionic fibers: vagus nn; Postganglionic CB and fibers: walls of organs

Front 35

hindgut parasympathetic innervation

Back 35

Preganglionic CB: S2-4 levels of the spinal cord; Preganglionic fibers: pelvic splanchnic nerves; Postganglionic CB and fibers: walls of organs

Front 36

midgut sympathetic innervation

Back 36

preganglionic CB: lateral horn of the thoracic spinal cord; Preganglionic fibers: ventral root > spinal nerve > white ramus communicans > sympathetic trunk > thoracic splanchnic nerves; postganglionic CB: celiac or superior mesenteric ganglia; postganglionic fibers: follow arterial branches to target organ

Front 37

hindgut sympathetic innervation

Back 37

preganglionic CB: lateral horn of the lumbar spinal cord; Preganglionic fibers: ventral root > spinal nerve > white ramus communicans > sympathetic trunk > lumbar splanchnic nerves; postganglionic CB: inferior mesenteric ganglion; postganglionic fibers: follow arterial branches to target organ

Front 38

appendicitis pain

Back 38

presents as diffuse periumbilical pain (T10 dermatome); as parietal peritoneum becomes involved, somatic innervation localizes the pain to the right lower quadrant