ICL 1.1: Introduction to GI System & Associated Symptoms

Question 1

how many abdominal quadrants are there?

Answer 1

4

right upper and lower and left upper and lower quadrants

the abdominal surface has a midline of the abdominal wall which extends from xyphoid process to pubic symphysis and a transumbilical horizontal line –> these two axis are what split the abdomen into 4 quadrants

Question 2

what are the 9 anatomical sections of the abdomen?

Answer 2

there are vertical lines at the midclavicular line on each side

horizontally there is a subcostal plane and intertubercular plane (which passes through the tubercles of the iliac crest)

top row sections: right hypochondriac, epigastric region, left hypochondrium

middle row sections: right flank, umbilical region, left flank

bottom row sections: right ground, pubic region, left groin

these are used to describe the locations of the organ!

Question 3

which organs are located in the alimentary canal?

Answer 3

1. oral cavity/salivary gland
2. pharynx
3. esophagus
4. stomach
5. small intestine
6. large intestine
7. anus

Question 4

what are the layers of the alimentary canal?

Answer 4

1. mucosa
2. submucosa
3. muscularis externa; smooth muscle
4. serosa

Question 5

what is the mucosa layer of the alimentary canal?

Answer 5

it’s the innermost layer of the alimentary canal organs

it’s moist membrane with an innermost surface of epithelium –> then farther out there’s a small amount of connective tissue called the lamina propria with mucus glands in it –> then there’s an outermost small smooth muscle layer called the muscularis interna/muscularis mucosa

1. epithelium (inner most)
2. lamina propria
3. muscular interna (outermost)

Question 6

what is the submucosa layer of the alimentary canal?

Answer 6

the layer just outside the mucosa

it’s composed of:
1. connective tissue

2. blood vessels
3. nerve endings
4. lymphatics
5. glands

Question 7

what is the muscular externa layer of the alimentary canal?

Answer 7

it’s actually two layers

there is an inner circular layer while the outer layer is arranged longitudinal

Question 8

what is the serosa layer of the alimentary canal?

Answer 8

it’s the outermost layer of the alimentary canal and it’s also called the visceral peritoneum

it’s composed of layers of serious fluid-producing cells

Question 9

which nerve plexuses are in the alimentary canal?

Answer 9

1. submucosal nerve plexus
2. myenteric nerve plexus
3. subserous plexus

Question 10

what are the parts of the small intestine?

Answer 10

1. duodenum (first part)
2. jejunum
3. ileum (last part)

Question 11

what is the duodenum? where is it located?

Answer 11

it’s the first and widest part of small intestine

it’s split into 4 parts: superior, descending, inferior and ascending

it’s shaped like a letter C within which the head and uncinated process of pancreas are lodged

it starts at pyloric orifice of the stomach and ends at the duodenojejunal flexure –> the flexure is suspended/held in place to the posterior abdominal walls by Ligament of Treitz

Question 12

what are the 3 important anatomical relations of the duodenum?

Answer 12

1. with the gallbladder neck –> chronic inflammation of the gull bladder can lead to the formation of a biliary enteric fistula between the gallbladder and duodenum where large gall stone can pass through and cause a gallstone ileus = partial or complete intestinal obstruction
2. with the gastroduodenal artery branch of the hepatic artery which passes behind the first part of the duodenum, putting the artery at risk in perforated duodenal ulcers
3. with the superior mesenteric artery which crosses in front of the third part of the duodenum which may cause partial obstruction of the duodenum

Question 13

what is the plicae circularis?

Answer 13

the distal mucosa and submucosa of the duodenum has circular folds called plicae circularis

they start in the duodenum and extend through the whole intestine but they do get sparser in the ilium until they disappear in the terminal ilium

Question 14

what is the blood supply of the duodenum?

Answer 14

the proximal half of the duodenum, above the hepato-pancreatic ampulla, developmentally belongs to the foregut and supplied by branches of the celiac artery:

1. superior pancreaticoduodenal
2. supraduodenal artery
3. right gastric

the distal half of duodenum, below the hepatopancreatic ampulla, developmentally belongs to the midgut and is supplied by branches of the superior mesenteric artery, through the inferior pancreatico-duodenal artery

Question 15

what is Willkie’s Syndrome?

Answer 15

aka superior mesenteric syndrome

the duodenum is sandwiched in-between the branch point of the abdominal aorta and the superior mesenteric artery and if this angle gets to less than 10 degrees it’ll compress the 3rd part of the duodenum causing partial or complete intestinal obstruction

a typical patient is tall, frail, slender = asthenic habitus, and has flacid abdominal muscles

they also usually have nausea and vomiting 1-2 hours after meals and obtain relief by lying down or leaning forward to widen the angle between the arteries

Question 16

what happens in the small intestine?

Answer 16

the small intestine is where the partially digested food from the stomach is mixed with the pancreatic and intestinal enzymes and becomes completely digested

digested food, water, electrolytes and minerals are absorbed and directed to the liver through portal circulation

so there is complete digestion and absorption of food in the small intestine!

it also has entero-endocrine function

the length of small intestine is approximately 6-7 meter

Question 17

where are the jejunum and ileum located?

Answer 17

the small intestine progressively decreases in diameter and wall thickness from duodednojejunal flexure to ileocecal junction

the jejunum and ileum occupy the infracolic compartment of the greater peritoneal sac

the greater omentum hangs down from the stomach covering them

the coils of jejunum lies above and to the left (umbilical and left lumbar regions), whereas the ileum lies below and to the right (hypogastric and pelvic regions)

jejunum and ileum are attached to the posterior wall by the mesentery = intraperitoneal and mobile

Question 18

what are the mucosal specializations present in the jejunum and ileum?

Answer 18

the small intestine is not only long, but also endowed with marked specialization of it is luminal surface (mucosa) to increase the absorptive capacity

1. circular folds (plicae circularis)
2. intestinal villi
3. intestinal glands (crypts of lieberkuhn)

serosa and muscularis externa is similar to the remaining part of the GI tract

Question 19

where are the plicae circularis? what do they look like?

Answer 19

the plicae circularis includes the mucosa and submucosa starting in the duodenum

they reach their maximum height (8mm) and number in the jejunum, and decrease in height and number gradually in the ilium

they are responsible for the feather-like appearance in radiographs –> they make the jejunum look like it’s wrinkled

Question 20

what are the intestinal villi?

Answer 20

a feature of the mucosa throughout the entire length of the small intestine

they’re finger-like projections less than 0.5 mm barely visible to the naked eye but en masse they give the mucuous membrane the velvety appearance

Question 21

what are the crypts of Lieberkuhn?

Answer 21

aka the intestinal glands that are throughout the mucuosa of the small intestine

they are simple tubular glands

Question 22

where is the jejunum located? where does it start and end? how long is it?

Answer 22

it’s the second part of the small intestine and lies between the duodenum and the ileum

it’s is considered to begin at the attachment of thesuspensory ligament of the duodenumto the duodenum, a location called theduodenojejunal flexure

however, the division between the jejunum and ileum is not anatomically distinct

in adulthumans, the small intestine is usually between 6-7m long, about two fifths of which (2.5 m) is the jejunum

Question 23

what are the general characteristics of the ileum?

Answer 23

it’s the final segment of the small intestine and it has more fat inside the mesentery than the jejunum

the diameter of its lumen is smaller and has thinner walls than the jejunum

its circular folds are smaller and absent in the terminal part of the ileum

while the length of the intestinal tract contains lymphoid tissue, only the ileum has abundant Peyer’s patches

Question 24

what is the blood supply of the jejunum and ileum?

Answer 24

the jejunum and ileum receive their blood supply through 10-16 jejunal and ileal branches from the superior mesenteric artery

within the mesentery, these branches form anastomotic arterial arcades which increase in complexity toward the terminal ileum

Question 25

what's the difference between the blood supply of the jejunum vs. ileum?

Answer 25

JEJUNUM 1. less complex arterial arcades 2. longer vasa recta 3. more plicae circulares, thicker, more highly folded 4. no fat in mesentery ILEUM 1. more complex arterial arcades 2. shorter vasa recta 3. less plicae circulates, thinner less folded 3. fat present in mesentery

Question 26

what is the different in the position, diameter, wall thickness, circular folds, vascularity, vasa recta, color, lymphatic follicles and fat in the jejunum vs. ileum?

Answer 26

JEJUNUM 1. upper 2/5 2. bigger diameter 3. thicker walls 4. more plicae circulares 5. greater vascularity 6. long vasa recta 7. deep red color 8. solitary lymphatics 9. less fat ILEUM 1. lower 3/5 2. smaller diameter 3. thinner walls 4. fewer plicae circulares 5. less vascularity 6. pale pink 7. aggregated lymphatics 8. more fat

Question 27

what conditions is the small intestine at risk for? why?

Answer 27

the intraperitoneal nature of the small intestine and the fact that it has mesentery make it highly mobile part of the GI and put it at risk and predispose it the small intestine to these clinical condition: 1. internal, inguinal, and femoral hernias 2. volvulus (gets twisted) 3. intussusception

Question 28

what are the different types of abdominal hernias?

Answer 28

1. internal | 2. exernal --> ventral vs. dorsal

Question 29

what are the components of the large intestine?

Answer 29

1. cecum and the appendix 2. ascending colon 3. right colic flexure (hepatic) 4. transverse colon 5. left colic flexure (splenic) 6. descending colon 7. sigmoid (pelvic) colon 8. rectum 9. anal canal

Question 30

what are the general features of the large intestine?

Answer 30

it's 1.5-1.8 meters long with the exception of the rectum, it is caliber gradually decreases from the cecum to the anal canal the proximal part of the large intestine absorbs water and electrolytes, and it is distal part stores feces

Question 31

how can you distinguish the large intestine from the small intestine?

Answer 31

1. tenia coli 2. sacculations or haustrations 3. appendices epiploicae (mental appendices)

Question 32

what is the tenia coli?

Answer 32

thickening of the longitudinal muscles of the large intestine to form 3 bands on the anterior, posteromedial and posterolateral surfaces it's located on the the transeverse colon, superior, anterior and inferior of the large intestine the tenia coli converge at the base of the appendix and can be used during appendectomy to located the appendix

Question 33

what are sacculations/haustrations?

Answer 33

a feature of the large intestine that helps differentiate it from the small intestine the grooves between the haustra are marked by semilunar folds internally

Question 34

what are the appendices epiploicae?

Answer 34

a feature of the large intestine that helps differentiate it from the small intestine they are peritoneal tags filled with fat present on the surface of the large intestine except in the cecum, appendix and rectum

Question 35

what is the cecum? where is it located?

Answer 35

it is the sacculated diverticulum of the large intestine below the level of ileocecal junction it is the inferior blind end of the ascending colon it is, but not always, completely surrounded by peritoneum which makes it intraperitoneal and mobile the cecum is located in the right iliac region (fossa)

Question 36

what are the opening in the cecum?

Answer 36

1. opening of the vermiform appendix

Question 37

where is the ascending colon?

Answer 37

it starts at the level of ileocecal junction as a continuation of the cecum and ends at the inferior surface of the right lobe of the liver where it sharply bends to form right colic flexure

Question 38

where is the transverse colon?

Answer 38

it starts at the right colic (hepatic) flexure as a continuation of the ascending colon and ends in the left colic (splenic) flexure where the large intestine continues as the descending colon its extremities (hepatic and splenic flexures) are deeply placed and relatively fixed, i.e., do not have mesentery the remaining part is of the transverse colon is suspended by the mesentery (transverse mesocolon) to the posterior abdominal wall (mobile and intraperitoneal) and may reach to the level of the umbilicus or below

Question 39

where is the descending colon?

Answer 39

it starts at the left colic (splenic) flexure and ends by becoming the sigmoid (pelvic) colon

Question 40

what is the blood supply of the large intestine?

Answer 40

from the branches of the superior and inferior mesenteric arteries, anastomosing together and forming the marginal artery named arteries are accompanied by veins which eventually end in the portal vein

Question 41

what is the different between diverticulosis and diverticulitis?

Answer 41

diverticulosis = the presence of diverticula diverticulitis = inflammation and complications of diverticula

Question 42

which organs are associated with the GI system?

Answer 42

1. salivary glands --> parotid, submandibular, sublingual 2. liver 3. pancreas

Question 43

what are the roles of the liver?

Answer 43

1. metabolic activities 2. glycogen storage 3. bile salts and bile pigments secretion 3. host defense 4. toxic metabolite elimination 5. hemopoiesis (fetal life)

Question 44

what is the location of the liver?

Answer 44

it's located in the right upper quadrant of the abdomen and is the largest glandular visceral organ in the body it's intraperitoneal, i.e., completely covered with peritoneum except at the bare area of the liver

Question 45

what are the anatomical lobes of the liver?

Answer 45

based on the surface landmark, the liver is divided into right and left lobes by the falciform ligament and the fissures for ligamentum venosum and fissure for ligamentum teres the caudate and quadrate lobes are parts of the anatomical right lobe

Question 46

what are the functional lobes of the liver?

Answer 46

based on the blood supply, the liver is divided into right and left functional lobes left functional lobe is supplied by the left branch of hepatic artery and includes the anatomical left lobe, caudate lobe and quadrate lobe. right functional lobe is supplied by the right branch of the hepatic artery and includes the right anatomical lobe minus caudate and quadrate lobe

Question 47

what are the hepatic segments of the liver?

Answer 47

the liver is divided into 8 hepatic independent segments each segment is supplied by a branch of portal vein, hepatic artery, branch of hepatic duct, and a tributary of hepatic vein each segment is self-contained and can be surgically resected individually without affecting others

Question 48

what are the surfaces of the liver?

Answer 48

the liver looks like a 4-sided pyramid --> the base (lateral surface) of the pyramid faces right while the apex faces the left it has 5 surfaces: anterior, superior, lateral, posterior and inferior the anterior, superior and lateral surfaces are continuous with no borders separating them and collectively called diaphragmatic surface of the liver, and all the three surfaces can be seen in the anterior view the posterior and inferior surfaces can be seen only in a posterior view

Question 49

what is the diaphragmatic surface of the liver? what features are associated with it?

Answer 49

it's made of the anterior, superior and lateral surfaces of the liver it is related to the diaphragm, separating it from the thoracic wall, base of the lung, base of pleura and costodiaphragmatic recess superiorly, and anterior abdominal wall inferiorly it has the falciform ligament, a peritoneal fold, connecting the liver to the diaphragm and anterior abdominal all, and separating the right and left lobes of the liver the upper layers of the right and left coronary ligaments separate the diaphragmatic surface from the posterior surface of the liver

Question 50

what is the posterior surface of the liver?

Answer 50

the posterior surface of the liver is separated from the superior surface by the upper layer of coronary ligament it is separated from the inferior surface by the lower layer of coronary ligament it has the bare area of the liver on it it is broad on the right side and reduced into a ridge of the left side

Question 51

what is the inferior surface of the liver?

Answer 51

the inferior surface is separated from the posterior surface by the lower layer of coronary ligament, and from the lateral surface by the lateral border, and from the anterior surface by the sharp inferior border

Question 52

what are the 3 peritoneal reflections around the liver?

Answer 52

1. falciform ligament 2. lesser omentum 3. coronary ligaments

Question 53

what is the falciform ligament?

Answer 53

a peritoneal reflection around the liver it's a double-layered fold of peritoneum connecting the anterior and superior surfaces of the liver to the diaphragm and anterior abdominal wall it has the ligamentum teres (round ligament) in its free margin

Question 54

what is the lesser omentum?

Answer 54

a peritoneal reflection around the liver it's a double layered fold of peritoneum which attaches to the margins of the fissure for ligamentum venosum and porta hepatis to the lesser curvature of the stomach

Question 55

what are the coronary ligaments?

Answer 55

a pair of peritoneal reflection around the liver 1. the upper (anterior) layer of coronary ligament: the peritoneal reflections from the undersurface of the anterior part diaphragm to the superior surface of the liver 2. the lower (posterior) layer of coronary ligament: the peritoneal reflection from the undersurface of the posterior part of the diaphragm the upper and lower layers of coronary ligament bound the bare area of the liver located on the posterior surface the upper and lower layers of coronary ligament fuse on the right and left to form the right and left triangular ligament; respectively

Question 56

what are the components of the hepatobiliary system?

Answer 56

1. gallbladder 2. cystic duct 3. right and left hepatic ducts 4. common hepatic duct 5. bile duct 6. hepatopancreatic duct

Question 57

what is the location of the pancreas?

Answer 57

it's a large, soft lobulated gland located in the posterior abdominal wall, from the duodenum to the spleen (umbilical, epigastrium, and left hypochondrium)

Question 58

what are the peritoneal coverings of the pancreas?

Answer 58

it is retroperitoneal organ which means only the anterior surface is covered with peritoneum the tail is intraperitoneal and lies within the lienorenal (splenorenal) ligament.

Question 59

what are the 4 parts of the pancreas?

Answer 59

1. head uncinate process = leftward extension of the head behind the SMV 2. neck 3. body 4. tail

Question 60

what is the blood supply of the pancreas?

Answer 60

1. superior pancreaticoduodenal artery 2. inferior pancreaticoduodenal artery 3. splenic artery

Question 61

what are the clinical important anatomic relationship of the pancreas?

Answer 61

1. portal vein forms behind the neck of pancreas so cancers of the head of pancreas may block portal vein causing portal hypertension 2. bile duct runs in a groove in the head of pancreas and may be blocked by cancers of the head of pancreas causing obstructive jaundice 3. tail of pancreas is located in the splenorenal ligament and is at risk during splenectomy 4. pancreas is related to the posterior surface of the stomach and is at risk in perforated gastric ulcer in the posterior wall of the stomach

Question 62

what is the function of the pancreas?

Answer 62

exocrine part secreting pancreatic enzymes endocrine part secreting insulin, glucagon and somatostatin

Question 63

what is the spleen?

Answer 63

a large encapsulated mass of vascular and lymphoid tissue located in the left hypochondrium its shape varies from a slightly curved wedge to tetrahedron

Question 64

what is the function of the spleen?

Answer 64

it removes particulate material, including aging blood cells from circulation and provide lymphocytes and antibodies

Question 65

what are the borders of the spleen?

Answer 65

3 borders: 1. superior at the level of the 9th rib 2. interior border at the level of the 11th rib 3. intermediate border where the hills is located; the long axis of the spleen is at the 10th rib it has 2 ends: 1. broad anterior end at the level of the midaxillary line 2. narrow posterior end 2 inches from the dorsal midline

Question 66

what are the peritoneal coverings of the spleen?

Answer 66

spleen is intraperitoneal organ which means it's completely covered by peritoneum and attached to the stomach by gastrosplenic ligament and to the kidney by the splenorenal (lienorenal ) ligament

Question 67

what are the surfaces of the spleen?

Answer 67

1. diaphragmatic surface: related to the abdominal surface of the diaphragm separating it from to lower part of the left lung and left pleura and the left costodiaphragmatic recess and rib 9-11 2. visceral surface: related to the fundus of the stomach, tail of pancreas, left kidney, left colic (splenic) flexure and phrenicocolic ligament the spleen is the most frequently ruptured abdominal organs followed by the liver by blunt abdominal trauma.