anatomy GI Flashcards
Where does the GI system begin and end?
Superiorly by the inferior thoracic aperture and inferiorly by the pelvic inlet.
What are the layers of the abdominal wall?
- Skin
Subcutaneous Tissues - Superficial fascia (Campers: fatty)
- Superficial fascia- Scarpa’s
Muscles - External oblique
- Internal Oblique
- Transversus abdominis muscle
Fascia - Transverse fascia
- Extraperitoneal fascia/fat
- Parietal peritoneum
Do all sections of the stomach have all the layers?
No, for example, when doing a C section, we will make an incision lower in the abdominal where as a midline incision will be through a different layer.
Why is the GI system enclosed? What is it enclosed by?
The GI system is enclosed by the peritoneum and this is protective in the case of a hole or perforation, so bacteria don’t leak out and infection can be contained. The GI system is still continuous with the pelvic cavity.
Females with ovarian cancer, where is the malignancy more likely to spread?
To the abdominal wall
What is the fundiform ligament?
a suspensory ligament that separates the penis and the vulva
What makes up the Scarpa’s superficial fascia?What are the margins of Scarpa’s?
Does Not contain fat, runs inferior to the abdominal wall and merges with the fascia lata of the thigh. On the midline Scarpa’s merges with the Linea alba, which is a very fibrous structure that runs down the midline of the abdomen. Also forms the fundiform ligament
Aponeurosis suspends what structures?
The muscles used the specialized flattened tendons called the aponeurosis to attach to bone or other fascia. A lot of times, they are attached to the linea alba here too.
When we cut the abdomen during surgery what are we cutting?
There isn’t much muscle in the central portion of the stomach, really only the rectus abdominis and aponeurosis. This is where we talk about belly muscle weakness during pregnancy. We are really cutting the aponeurosis.
Describe the external oblique
The fibers of this muscle run hands in pockets. The linea alba extends from the xiphoid process down to the pubic symphysis. The inguinal ligament runs from the anterior superior iliac spine (ASIS) to the pubic tubercle of the pelvis.
Aponeurosis (rectus sheath) and linea alba
Define aponeurosis
Flattened tendon by which muscle attaches to bone or fascia
What does the internal oblique contribute to?
This contributes to some of the reasons why we develop hernias in the lower abdomen. The rectus sheath differs throughout the abdomen and linea alba.
How does the rectus sheath differ in regards to the internal obliques?
The rectus sheath is important because it differs in the upper vs lower abdomen.
What is the orientation of internal obliques?
Sit more horizontally and travel more superior medial. Fibers run superficially (perpendicular to the external oblique).
What is the purpose of the transversalis fascia?
It separates the muscular layer from the peritoneum. It is a little deeper and continues down into the pelvic cavity
Define the transversus abdominis
This is the deepest layer and contributes to the rectus sheath. Runs similarly to the internal oblique just deep. Still contributes to the aponeurosis
What does the word fascia mean?
It is the layer of fibrous connective tissue that surrounds muscles, blood vessels, and nerves
What is the purpose of extraperitoneal fascia/fat?
Anteriorly it is pretty narrow and posteriorly it thickens up to surround the kidneys to protect and cushion them.
There is vasculature all throughout the layers of skin, which concerns us when?
When we are doing surgery and inserting items like trocars and such.
What is the rectus abdominis?
Vertical, more anterior paired midline muscle. Outside of trauma cases, most surgeons will try to move these muscles to avoid cutting them. These muscles are enclosed within the rectus sheath. Separated in the middle by the linea alba and the tendinous intersections separates the abdominal muscles and creates that 6-pack look.
What structures differentiate the start of the arcuate line?
Midway below our belly button
Why do we get umbilical hernias?
There is an opening of the rectus sheath there, so it is a common site for hernias to occur
Surgeons are terrified of wound dehiscence. Why?
The more tension we have on a wound, the greater risk for dehiscence.
What is the relationship of the rectus sheath to above the arcuate line?
Rectus sheath runs both superficial and deep
What structures are below the arcuate line?
The rectus sheath only runs superficially. Hernias, surgical incisions, vascular considerations, and no rectus sheath posteriorly
What structures are at the arcuate line?
There are some blood vessels that supply the abdominal wall by penetrating through the rectus sheath.
Why do we love trocar incisions at the belly button?
Because we are going through the linea alba and not going through any muscle
The superficial arteries of the abdominal wall are the main supply to skin and superficial fascia through which arteries?
Musculophrenic artery (branch of internal thoracic)- supplies superior portion of the superficial abdominal wall.
Superficial epigastric and circumflex iliac arteries (branches of the femoral artery) supplies the inferior portion of the superficial abdominal wall.
Where do the intercostal, lumber, and subcostal arteries extend from?
Directly off of the abdominal aorta
The deep arteries of the abdominal wall supply the muscles and deeper structures through which arteries?
Superior epigastric artery (branch of the internal thoracic)- supplies superior portion of the deep abdominal wall
Intercostal, lumbar, and
subcostal arteries brnach directly off the abdominal aorta suppies lateral and posterior portion of the deep abdominal wall
Inferior epigastric and deep circumflex branch off of the external iliac arteries and supplies the inferior portion of the deep abdominal wall
What would we be worried about hernias occurring near the inferior epigastric?
Because hernias occur either laterally or medially to this artery and it can cause occlusion
Why is lymphatic drainage of the abdomen important?
Sometimes in patients with colon cancer, we can palpate these enlarged lymph nodes. Defined as above or below the umbilicus.
Where do the main lymph nodes above the umbilicus drain?
The lymph nodes above the umbilicus drain mostly to the axillary and some parasternal lymph nodes
What are the parietal/visceral peritoneum?
The peritoneum is the deepest layer. These posteriorly in the abdomen are thin sheets that come off and wrap around the structures that are suspended in the abdomen.
Where do the main lymph nodes below the umbilicus drain?
The lymph nodes below the umbilicus drain to the superficial inguinal nodes
What is mesentery?
The name of the fold of peritoneum that helps to suspend structures of the abdomen is called the mesentery. Mesentery is also a main route of nerves and vessels to travel along and enter and exit this tissue to supply structures of the abdomen.
Describe the greater omentum
A big blob of fat, which is the first thing we will see, hangs from the inferior portion of the stomach, aka the greater curvature of the stomach. We will move this out of the way or potentially cut through it. Left and right gastro-omental vessels provide blood to the greater omentum.
Describe what organs are intraperitoneal
Stomach, spleen, liver, first and fourth parts of the duodenum, jejunum, ileum, transverse, and sigmoid colon. These organs are suspended in the mesentery.
Describe what organs are retroperitoneal
The aorta, esophagus, second and third parts of the duodenum, ascending and descending colon, pancreas, kidneys, ureters, and adrenal glands. These structures lie between the peritoneum and the abdominal wall.
Describe the lesser omentum
When the liver is reflected, usually during a cholecystectomy, we can see the lesser omentum that anchors and forms the Hepatogastric and Hepatoduodenal ligaments.
Omental bursa forms the lesser sac that is behind the stomach
What are the divisions of the peritoneal cavity?
The greater sac extends from the diaphragm to the pelvis, and the connection between the greater and lesser omentum is the omental foramen. The lesser sac (omental bursa) is behind the stomach and the lesser omentum
What arteries form the foregut?
The foregut includes the esophagus, stomach, liver, gallbladder and bile ducts, pancreas, and proximal duodenum
It is supplied by the celiac trunk, which includes the common hepatic, left gastric, and splenic arteries.
What arteries form the midgut?
The midgut includes the lower duodenum, jejunum, ileus, cecum, appendix, ascending colon, and proximal ⅔ of the transverse colon and is supplied by the superior mesenteric artery (SMA)
What arteries form the hindgut?
The hindgut includes the distal ⅓ of the transverse colon, descending colon, sigmoid colon, rectum, and upper anal canal and it is supplied by the inferior mesenteric artery (IMA)
Why is the GE junction such an important structure?
This is where the esophagus enters the stomach. This is a common site for pre-cancer (Barrett’s esophagus) because we get a lot of acid reflux there. This junction sites there and tries to protect the esophagus from that reflux, but we still get it and the more we have and the more damage to tissues, the greater the risk of cancer
What are the structures of the stomach?
Cardia, fundus, body, pylorus (antrum and canal with sphincter and orifice, that are continuous with each other)
What structure determines how fast our stomach empties?
The pyloric sphincter
Who does pyloric stenosis most likely occur in and why?
Little babies due to the narrowing of the canal or sphincter, sx include projectile vomiting. Other causes in other populations may include tumors.
What is the arterial supply of the lesser curvature?
Left gastric artery (direct branch of the celiac trunk):
Right gastric artery (branch of hepatic artery proper of the common hepatic)
What is the arterial supply of the greater curvature?
Left gastro-omental artery (branch of the splenic artery)
Right gastro-omental artery (branch of the gastroduodenal of the common hepatic)
What is the arterial supply of the fundus and upper stomach?
Short gastric arteries (branches of the splenic artery)
Describe the structures of the small intestine
The duodenum (superior, descending, inferior, and ascending)
Jejunum (plicae circulares that are just folds inside of the intestine; proximal ⅖)
Ileum (distal ⅗)
Where does bile enter into the duodenum?
Through the descending duodenum
The ascending portion of the duodenum is suspended by what structure?
The ligament of treitz
Why is the superior duodenum the most common place for duodenal ulcers?
this is the first place where acidic chyme hits
Which structures have more internal plicae circulares and allow us to differentiate them?
The jejunum has more plicae circulares than the ileum
What is the main purpose of the ligament of Treitz?
To suspend the ascending portion of the duodenum
What is the blood supply to the duodenum?
the pancreaticoduodenal artery and the gastroduodenal artery branch of the common hepatic artery
What is the blood supply to the jejunal artery?
The SMA
What is the blood supply to the jejunum and the ileum?
The jejunal artery (SMA) and ileal artery (SMA). These are also called the Vasa Recta blood supply. The ileum has more anastomoses in the vessels within its mesentery.
What is the blood supply to the cecum and appendix?
The cecal artery (SMA)
Describe the ileocecal valve and ileocecal fold flaps
The ileocecal valve prevents the reflux of contents from the SI to the LI
What is the mesoappendix?
Anchors the appendix to the ileum and the cecum.
What is the appendix?
It is a hollow extension of the cecum that does have some lymph tissue in it
What are the differences in placement of the appendix
and what are the names?
What are the structures of the LI?
What are the flexures of the LI?
Right colic fissure and left colic fissure
What do we see a lot of in the sigmoid colon?
Diverticulosis, where little bubbles occur in the wall of the intestine. They are benign until they become diverticulitis where they get inflamed and can perforate and spill intestinal contents into the abdomen. We don’t know what causes diverticulitis, but it is thought that maybe in our diet, we get bacteria or seeds and cause perforation of the bubble.
What is the LI also called?
The colon
What are the taeniae coli?
Longitudinal ligament muscle that separates separates the large intestine into sacs
What are haustra?
The sacs are separated by the tension of the taeniae coli. It is within the walls of the haustra, that we have these outflowings to form these diverticula
What are omental appendices?
Fat deposits
What is McBurney’s point?
It is one one-third the distance between the ASIS and the umbilicus. We should be able to have pain in the patient when pressing on the ASIS.
Describe the left and right paracolic gutters
Peritoneal recesses (spaces) are located between the ascending and descending colon and the abdominal wall. This allows us to kind of pull out the LI and mobilize it to visualize the blood supply and what structures need to be dissected.
What is the blood supply to the large intestine (colon)?
SMA and IMA form a whole bunch of anastomoses that give off arteries like the Marginal artery that runs along the margin and parallel to the colon/LI to help supply it. It helps to provide a lot of collateral blood supply to the LI
What are the rectal arteries?
IMA, internal iliac, and pudendal arteries
What are dentate/pectinate line and how do they contribute to hemorrhoids?
There is a neurologic line referred to as the dentate/pectinate line, where above there is less pain, maybe some bleeding, and they are internal, so they can’t be visualized. Below the detent/pectinate line is where we can get external hemorrhoids that tend to cause more pain and rectal bleeding and can be visualized in the rectal tissue
What are the structures of the posterior surface of the liver?
left/right/caudate/quadrate lobes
Renal, gastric, esophageal, and colic impressions
Ducts: left and right hepatic = common hepatic
What is the falciform ligament?
Anterior abdominal wall attachment that anchors the liver
What is the porta hepatis?
This is where vasculature enters and bile ducts exit the liver. “The gateway point”
What are the structures of the gallbladder?
Neck, body, fundus
Ducts: cystic which merges with common hepatic to become (common) bile duct
What is the arterial supply of the liver?
Common hepatic artery
What is the arterial supply of the gallbladder?
Cystic artery (branch of the common hepatic artery). Cut this structure when doing a cholecystectomy and NOT the common hepatic, because you can kill someone
What are the structures of the pancreas?
Lies posterior to the stomach
Head, neck, body, tail
Main and accessory pancreatic ducts release enzymes
Arterial supply: splenic, common hepatic, and SMA
What procedure has been known to cure pancreatic cancer?
Cancer usually occurs in the head of the pancreas most often and the Whipple procedure has been known to cure it, where surgeons resect a portion of the pancreas
What are the structures of the spleen?
Sits at the diaphragm at rib 9 and 10
Hilum , Red (where RBCs are made) and white (where WBCs are made) pulp. Blood supply through the splenic artery. Spleen is insanely vascular
The left renal vein drains what structures?
Kidney, adrenal glands, gonads
The common iliac veins drain which structures?
Lower limb, pelvis, peritoneum
What does the hepatic portal system drain?
Intestines, spleen, pancreas, gallbladder, and hepatic veins
What do the portocaval anastomoses with?
HBS→ liver → Hepatic veins → IVC
Portocaval anastomoses are in the HBS.
Inferior esophagus, superior rectum, beds drained by systemic vessels
What do we see commonly with liver failure?
Mostly in alcoholics
Varices or caput-medusae (specific abdominal wall vasculature that is congested) and thrombocytopenia= recipe for disaster and these patients will probably come in vomiting blood
What do caput medusae, esophageal varices, and rectal varices look like?
When the liver or HBS fails, there is backup of fluid and these circumstances can occur.
What is the celiac plexus (foregut)?
Receives fibers from the greater and lesser splanchnic nerves and vagus nerves
What is the aortic plexus?
Superior mesenteric plexus (midgut) → receives fibers from the lesser and least splanchnic nerves and vagus nerve.
Inferior mesenteric plexus (hindgut) → receives fibers from the lumbar splanchnic nerves and pelvic splanchnic nerves
What is the sensory innervation of the nerves?
What is the hypogastric plexus?
Aka the pelvic organ connects the abdominal autonomic system to the pelvic ANS
What is the autonomic innervation of abdominal organs via the paravertebral/prevertebral plexus?
sympathetic= splanchnic nerves (greater, lesser, least, lumbar)
parasympathetic= vagus and pelvic splanchnic nerves
What are the main three plexus’ of the prevertebral plexus?
Aortic plexus, hypogastric plexus and celiac plexus
Describe the linea alba and its margins
White band that extends from the xiphoid process to the umbilicus. Then inferior to the umbilicus, it extends to the pubic symphysis and is covered by aponeurosis of the external abdominal oblique.
What does the aponeurosis and rectus sheath cover?
The abdominis muscle
Where is the transversus abdominis located?
Deep to the internal oblique
Describe the purpose of the transversalis fascia
Connects the anterior abdominal wall peritoneum to the posterior aspect of the transversus abdominis.
What is the location and importance of the inguinal canal and inguinal ring?
It is a specialized portion of the external oblique aponeurosis that we can see by looking at the inferior border of the external abdominal oblique aponeurosis and there should be the inguinal canal where also looking medially there is a small opening known as the superficial inguinal ring. THIS IS A COMMON PLACE FOR INGUINAL HERNIAS
Describe the position of the parietal peritoneum
Backside of anterior abdominal wall in the midline
What is the rectus abdominis and what are its margins?
It lies deep to the rectus sheath and runs from the costal cartilages above and down to the pubic bone inferiorly
Describe the inguinal ligament and its margins
It runs from the anterior superior iliac spine to the pubic tubercle and along the pectina pubis. It is a specialized portion of the external oblique aponeurosis that we can see by looking at the inferior border of the external abdominal oblique aponeurosis with the inguinal ring medial
What is the round ligament of the liver?
Visceral, strong ligament that extends from the liver to the posterior aspect of the abdominal wall, AKAthe ligament of teres hepatitis that travels towards the umbilicus
Describe the liver with triangular ligaments and its points of attachment
On the right the triangular ligaments attach the right lateral side of the liver to the diaphragm and more specifically to the parietal peritoneum that is coating the inferior surface. The left triangular ligament attaches along the periphery of the coronary ligament
Describe the Falciform ligament with round ligament of the liver and its margins (aka ligamentum of teres hepatitis)
The round ligament of the liver can be palpated within the falciform ligament and these travel all the way to the umbilicus aka ligamentum of teres hepatitis
Describe the greater omentum
Covers the entire anterior abdominal cavity, but superiorly we can see an outline of the transverse colon, more specifically the stomach.
Describe the lesser omentum
The 2 ligaments of the lesser omentum are the hepatoduodenal, where the free edges are and where the gallbladder extends down towards and then down the hepatogastric section.
Describe the ascending, transverse, and descending colon
The descending colon is in a retroperitoneal position and descends to become confluent w/ the sigmoid colon (which has its own mesentery, allowing it to be mobilized within the peritoneal cavity and then if we follow that, we end up at the rectum
Describe the cecum w/ ileocecal junction
Where the appendix and mesoappendix attach. At this junction, we see the ileocecal junction
Describe the SMA and vein and the structures it supplies
It supplies the midgut, jejunal and ileal branches, appendicular branches to the appendix, a branch known as the right colic traveling over to the ascending colon. Middle colic vein and artery travel to the transverse colon. Ileocolic branches to the cecum
Describe the IMA and its associated branches
Branches off around L4 and branche into the left colic, sigmoid arteries, and the continuation as the superior rectal artery
Describe the gallbladder with its associated ducts and arterial vasculature
Gallbladder extends distally with the cystic duct. We then see the left and right hepatic ducts forming the common hepatic duct. When the common hepatic duct and cystic duct come together, they form the bile duct. We have a vessel extending from the right hepatic artery to supply the gallbladder, known as the cystic artery. The bile duct travels to the head of the pancreas and enters the 2nd part of the duodenum.
Describe the arterial supply to the stomach
Gastroepiploic arteries both left and right as they are uniting along the greater curvature of the stomach and extending down into the greater omentum
Describe the hepatic portal vein and 3 associated tributaries
The IMV, splenic vein, and the SMV which runs with the SMA that has 2 branches-anterior, inferior pancreatic duodenal branch and posterior inferior pancreatic duodenal branch
Describe the celiac trunk and associated arteries/branches
Celiac trunk→ common hepatic artery, left gastric artery, and splenic artery
What is the phrenicocolic ligament?
Extends from the splenic flexure of the colon to the diaphragm
Where do the left suprarenal and left gonadal vein drain into?
Left renal vein
At the bifurcation of the abdominal aorta, we have the right and left common iliac veins, which bifurcate into what vessels?
The internal and external iliac veins
The left common iliac travels deep to what structure?
The aorta and its common iliac branches
Where does the aorta enter the abdominal cavity?
At T12 through the aortic hiatus
Why is the cisterna chyli important?
It is a dilated component of the lymphatic system that as it crosses up into the thorax becomes the thoracic duct and drains all the lymph below the diaphragm
What are the branches of the abdominal aorta?
Celiac trunk → inferior phrenic artery
Descending → SMA
Left renal artery and its smaller branches that ascend to the adrenal gland (suprarenal and infrarenal)
Right renal artery
Lumbar arteries
Truncated IMA
Gonadal artery travels anterior to the ureter
What is the importance of the sympathetic trunk? Its location?
It is lateral to the aorta and the preaortic plexus can be visualized as running anterior to the aorta and then branches of the sympathetic chain aka the lumbar splanchnic nerves contributing to the superior hypogastric plexus.
What is the importance of the parasympathetic components of the abdomen?
The anterior vagal trunk comes through the esophageal hiatus and enters into the celiac ganglion and the SMA ganglion
Define the four quadrants and what aterial structures and organs are in each
What are the lobes of the liver?
left, right, caudate (above the gallbladder) and quadrate (belowe or beside the gallbladder)
Where does the abdominal aorta begin and end?
It begins at the aortic hiatus at T12 and descends inferiorly to about L4 where it is actually slightly to the left of the midline and branches into the common iliac arteries
Define the beginning and end of the foregut
The foregut starts with the esophagus and ends inferior to the duodenal papilla (aka midway along the descending part of the duodenum)
Where does the celiac trunk branch off?
L1
Define the beginning and end of the midgut
starts just inferior to midway point of the descending part of the duodenum and ends at the junction between the proximal 2/3 and distal 1/3 of the transverse colon.
Define the beginning and end of the hindgut
begins at the left colic flexure junction and ends midway through the anal canal
What is the smallest branch of the celiac trunk?
left gastric artery and it gives off all the esophageal branches. It supplies the lesser curvature of the stomach and the lesser omentum
Which structure does the left gastric artery eventually anastomose with?
the right gastric artery
What structure do the short gastric and left gastro-omental arteries branch off of?
the splenic artery
What is the largest branch of the celiac trunk?
the splenic artery. supplies the pancreas (everything but the head) and enters the hilum of the spleen.
What are the two branches of the common hepatic artery?
gastroduodenal artery and hepatic artery proper
What artery supplies the greater curvature of the stomach?
right gastro-omental artery
What structure supplies the head of the pancreas and a small portion of the duodenum?
the superior pancreaticoduodenal artery, which is a branch of the gastroduodenal artery
Where does the SMA branch off and what are its three main branches?
immediately below the celiac trunk and it gives on the inferior pancreaticoduodenal branch and the jejunal and iliac branches
From the right side of the main trunk of the SMA, what arteries are branching off and what do they supply?
- middle colic
- right colic
- ileocolic arteries
These arteries supply the terminal ileum, cecum, ascending colon, and two-thirds of the transverse colon
What are the vasa recta?
supply the jejunum are usually long and close together forming narrow windows visible in the mesentery. They also supply the ileum but are short, far apart, but more numerous.
Which of the colic arteries passes retroperitoneal?
right colic artery
The ileocolic artery continues inferior to branch into 4 other vessels, what are they?
colic, cecal, appendicular, and ileal branches
What is a watershed area and why is it clinically significant?
Along the descending part of the duodenum, there is a potential watershed area between the celiac trunk blood supply and the SMA. This is HIGHLY UNUSUAL for this area to become ischemic whereas other watershed areas are more vulnerable to ischemia
The IMA branches off of what area of the abdominal aorta and what branches does it supply?
it branches off of L3, slightly to the left of the midline, and supplies the left colic artery, sigmoid arteries, and the superior rectal artery
In certain disease states, the region of the splenic flexure of the colon can become ischemic. What happens when this occurs?
the mucosa sloughs off, rendering the patient susceptible to infection and perforation of the large bowel, which then requires urgent surgical attention.
