Lecture 42 & 44: GIT Flashcards
What structure delineates the thorax and abdomen?
The diaphragm
What structure delineates the abdomen and pelvis?
Trick question: there is no clear demarcation
What are the two planes of the abdomen?
Transumbilical plane = x-axis
Median plane = y-axis
What are the 5 hollow abdominal viscera?
Esophagus, stomach, small intestine, large intestine, gallbladder.
What are the three viscera of the GI tract?
Esophagus, stomach, small intestine
What are the 5 solid viscera of the abdominal cavity?
Liver, pancreas, spleen, kidneys, adrenals
What are the four facts about each abdominal viscera that we need to know?
Hollow/solid, intraperitoneal/extraperitoneal, identifying feature(s), principle vascular supply
What are the principle muscle layers of the abdominal wall?
Lateral aspect: external obliques, internal obliques, transversus abdominus.
Anterior aspect: Rectus abdominus
What are the three muscles of the posterior abdominal wall? What are their movements?
Psoas major (hip flexion), quadrus lumborum (lateral flexion of the thoracic spine), iliacus (hip flexion)
What shape is the cross section of the abdomen? Why?
Kidney shaped because of the lumbar spine.
What are the three roles of the mesentery?
Holds viscera in place, gives viscera mobility, creates nervous and vascular pathway to the viscera.
What are the two subtypes of peritoneum? Describe them.
Parietal peritoneum – that which covers the abdominal walls
Visceral peritoneum – that which covers the viscera
What is inside the potential space of the peritoneal membrane?
Serous fluid
What is the role of the serous fluid?
Reduces friction, thus increasing motility of the viscera
At what spinal level does the esophagus start?
C6
At what spinal level does the esophagus pass into the abdominal cavity?
T10
What is the role of the esophagus?
Pass food into the stomach
Where is the anatomical sphincter of the esophagus?
At the beginning just below the pharynx.
Where is the functional sphincter of the esophagus?
At the end as it passes obliquely through the muscular diaphragm.
What causes the narrowing in the middle of the esophagus?
The compression of adjacent viscera - ie the left main bronchus and the arch of the aorta
What is the name of the sharp, immediate change in esophageal lining as it enters the stomach?
Esophagogastric junction
What is the function of the stomach?
Store food and begin digestion
What is the location of the stomach?
LUQ
What are the two orifices of the stomach?
Cardiac orifice (opens to the terminal esophagus) Pyloric orifice (opens to the duodenum)
What is the shape of the stomach? (Remember to include the curves.)
J-shapes; lesser curvature (medial) and greater curvature (lateral)
What is the stomach’s relationship to the peritoneum?
Intraperitoneal
Where does air tend to stay in the stomach?
The fundus (up the top)
What is the name of the lining of the stomach that is just distal to the cardiac orifice?
The cardia
What is the largest segment of the stomach?
The body
What is the role of the pylorus of the stomach?
Forms a tunnel to the duodenum
What are the two parts of the pylorus?
Antrum (superior) and canal (narrow, funnel-like, inferior)
What is the role of the pyloric orifice as an anatomical sphincter?
Controls the movement of stomach contents into the duodenum
What are the internal foldings of mucosal lining in the stomach called?
Rugae
What happens to the pattern of the rugae as it tends from fundus to pylorus?
It becomes more massive
What is the first part of the small intestine?
Duodenum
What shape is the duodenum?
C-shaped
What are the four parts of the duodenum?
1 - duodenum cap/superior part
2 - descending part (L1-L3)
3 - Inferior/horizontal part
4 - Ascending part
Describe the location of the duodenum.
RUQ: Medial to the right kidney and closely attaches to the pancreas.
What is the physical relationship between the pancreas and the duodenum?
Medial head of the pancreas sits inside the C-shaped duodenum
What is the relation of the duodenum to the peritoneum?
Retroperitoneal (ie, peritoneum is only on the anterior surface of the duodenum)
Through what feature does the bile AND pancreatic enzyme enter the duodenum?
The major duodenal papilla in the descending duodenum
Where is the minor duodenal papilla relative to the major duodenal papilla? What enters through the minor duodenal papilla?
Proximal; pancreatic enzyme ONLY.
What two ducts join together to form the common bile duct?
Gall duct and hepatic duct
What enzyme is secreted by the pancreas into the duodenum?
Pancreatic enzyme
At what spinal level is the horizontal/inferior part of the duodenum?
L3
What is the relation of the rest of the small intestine (after the 4th part of the duodenum) to the peritoneum?
Intraperitoneal
What are the three parts of the small intestine? (Proximal to distal)
From proximal to distal: Duodenum, jejunum, ileum
What ~% of the small intestine is jejunum? In which quadrant is it located?
~40%; predominately LUQ
What ~% of the small intestine is jejunum? In which quadrant is it located?
~60%; predominately RLQ
What is the demarcation between jejunum and ileum?
Trick question: No clear demarcation
What are the 6 features that differentiate the jejunum and ileum? (Quite a lot of information.)
Jejunum vs ileum
- Location: LUQ v RLQ;
- Jejunum generally has a larger diameter;
- Jejunum has more mucosal folds, thus its wall is thicker;
- Jejunum has a greater vascular supply, ‘beautiful’ vasculature in the mesentery of the jejunum;
- More fat in the mesentery of the ileum (makes the mesentery look ‘obscure’);
- More absorption in the jejunum because it is more proximal.
Where does the ileum enter the large intestine?
Ileum enters the large intestine at the ileocaecum junction (ICJ)
What type of sphincter is the ICJ?
Anatomical
What two non-colonic structures are included as part of the large intestines?
Appendix and caecum.
Describe the path of the large intestine.
- Ascending colon on the right hand side.
90º medial turn at the liver - hepatic/right colonic flexure. - Transverse colon.
90º inferior turn at the spleen - splenic/left colonic flexure. - Descending colon.
Medial turn. - Sigmoid colon
- Rectum at the midline
- Anal canal.
What are the muscular differences between the small and large intestines?
Small: 2 completely muscular layers - circular and longitudinal.
Large: complete inner circular layer of muscle, but the outer longitudinal layer is subdivided into 3 distinct layers - ‘tenia coli.’
Other than muscle, what are two structural features that distinguish the large intestines from the small intestines?
The large intestines have... 1. Haustra/haustrations Baggy, circular saccy things 2. Omental apendices Fatty tags that hang down
What is the relationship between the peritoneum and the caecum?
Intraperitoneal
What is the relationship between the peritoneum and the appendix?
Intraperitoneal
What is the location of the caecum?
RLQ; inferior to the ICJ
How does the appendix attach to the large intestine?
Base attaches to the inferior aspect of the caecum, at the point where the tenia coli meet.
What are the relationships between the four parts of the large intestine and the peritoneum?
Ascending: Retroperitoneal (~3/4)
Transverse: Intraperitoneal
Descending: Retroperitoneal
Sigmoid: Intraperitoneal
In what ways is the rectum structurally different to the rest of the large intestine?
No tenia coli; no haustra; no omental appendices.
What is the largest solid organ in the body?
The liver
In which quadrant is the liver located?
Predominantly RUQ, beneath the diaphragm
What are the three main functions of the liver?
Produces bile
Metabolisms
Filtering blood
What are the two surfaces of the liver called?
The diaphragmatic surface (anterior, superior) and the visceral surface (posterior, inferior)
Which of the two hepatic surfaces is smooth and which is not smooth?
Diaphragmatic surface - smooth
Visceral surface - not smooth because it has the imprints of abdominal viscera
Is the majority is the liver is intraperitoneal or retroperitoneal?
Intraperitoneal
Why is the diaphragmatic surface smooth?
It sits against the diaphragm, which is a smooth structure
What divides the left and right lobe of the liver?
The falciform ligament
The inferior border of the liver is described as…
“sharp.”
Which lobe of the liver is larger, left or right?
Right
What are three important structural features of the visceral surface of the liver?
- It is concave because of the impressions of adjacent viscera.
- The IVC and the Gall bladder sit in the posterior and the anterior grooves, respectively
- The hilum is on the visceral surface, allowing the transmission of nerves and vessels.
What are the 5 structures that are generally present in a visceral hilum?
Nerves, arteries, veins, ducts, and lymphatic vessels
What is another name for the liver’s hilum?
Portal hepatis
What three vessels make up the hepatic triad?
- Hepatic duct – drains bile to the duodenum/gallbladder
- Hepatic arteries – oxygen and nutrition TO the liver
- Portal veins – actually a second vascular INPUT into the liver
What is the role of the portal vein?
Instead of draining blood away from the liver it brings venous blood into the liver from for metabolism. It collects all the tubular blood from the GIT and other abdominal viscera. (A lot of people have trouble realizing that the portal vein is an INPUT vessel to the liver.)
What part of the visceral surface of the liver is not covered by the peritoneum?
Majority of the visceral surface is covered by peritoneum EXCEPT the area of the hilum and the gall bladder.
How many lobes does the liver have? Which are ‘anatomical’ and which are ‘accessory’ lobes?
The liver has 4 lobes
Anatomical/true lobes: right and left
Accessory lobes: caudate and quadrate lobes
Describe how the visceral surface of the liver is divided into lobes.
Small LEFT lobe and large RIGHT lobe, divided by the left sagittal fissure. The groove of the IVC and Gall bladder forms another fissure: the right sagittal fissure. Hilum horizontally divides the area between the right sagittal fissure and the falciform ligament into another two lobes.
Why are the caudate and quadrate accessory lobes of the liver not considered anatomical lobes?
They are still a part of the right lobe.
Which accessory lobe is posterior and which is anterior?
Caudate - posterior
Quadrate - anterior
Which accessory lobe contains the IVC and which contains the gallbladder?
Quadrate - Gallbladder
Caudate - IVC
In which part of the liver is the gallbladder located? Which quadrant is it in?
Quadrate accessory lobe (anterior visceral surface); RUQ
What are the four parts of the gallbladder? (From inferior to superior)
Fundus, body, neck, cystic duct
The common bile duct is a consequence of the joining of which other ducts?
The hepatic duct from the liver and the cystic duct from the gallbladder
Which organ produces bile?
The liver.
Where does bile enter the duodenum?
The major duodenal papilla.
What is the role of the gallbladder?
To store and concentrate bile.
If the gallbladder sits above the major duodenal papilla then how does bile get into the gallbladder?
Major duodenum papilla is a true anatomical sphincter that closes when the duodenum is empty, thus allowing the bile to fill up the common bile duct. When there is enough bile it flows back up into the gallbladder.
What is the role of cholecystokinin (CCK)?
CCK is released when you eat fatty foods. It stimulates bile production in the liver, contraction of the gallbladder, and relaxation of the major duodenal papilla. IE, CCK causes bile release into the duodenum.
What is a cause of gallstones?
Over concentration of bile in the gallbladder.
What are two consequences of gallstones?
Can cause infections and extreme abdominal pains, esp after fatty meals.
Do most gallstones cause pain?
No, >50% of gall stones have silent symptoms.
In which quadrant is the pancreas located?
LUQ
Is the pancreas intraperitoneal or retroperitoneal?
Intraperitoneal
What are the four parts of the pancreas? (From medial to lateral)
Head, neck, body, and tail
Describe the physical relationship between the pancreas and the duodenum.
The head of the pancreas is surrounded by the C-shaped duodenum and its is closely associated with the 2nd and 3rd part of the duodenum.
Describe the location of the tail of the pancreas relative to its adjacent viscera.
Closely associated with spleen and anterior to the left kidney.
What are the functions of the pancreas?
Endocrine: Secretion of hormones directly into the circulation, including insulin. (Cross section shows many small blood vessels in the pancreas.)
Exocrine: secretion of pancreatic enzyme into the duodenum via the main pancreatic duct and the accessory pancreatic duct.
Which of the two duodenal papillae does each pancreatic duct open into?
Main pancreatic duct opens into the major duodenal papilla. Accessory pancreatic duct opens into the minor duodenal papilla.
Describe the location of the spleen.
LUQ against ribs 9, 10, and 11.
What type of viscera is the spleen?
Solid.
In adult, the spleen is purple. Why?
It is a reservoir for blood cells
What are the two surfaces of the spleen?
Diaphragmatic (smooth) surface and the visceral surface (indented)
Which of the two surfaces of the spleen contain the hilum?
The visceral surface.
What is the most common cause of damage to the spleen?
Damage to the spleen often occurs because of its location: behind ribs 9, 10, & 11. Since the ribs are concave if they fracture they will fracture inwards and can tear the spleen.
Why is rapturing the spleen considered a medical emergency?
Since it is a reservoir for blood cells, rupturing the spleen can cause massive internal bleeding and death.
At which spinal level does the aorta pass through the diaphragm?
T12
At which spinal level does the abdominal aorta divide? What does it divide into?
The abdominal aorta divides into the common iliac arteries at L4.
How many sets of paired arteries are there that supply abdominal viscera?
There are three sets of paired arteries: renal arteries, suprarenal arteries, and testicular/ovarian arteries.
How many unpaired arteries are there that supply abdominal viscera?
There are three unpaired arteries: celiac trunk, superior mesentery artery (SMA), inferior mesentery artery (IMA).
What structures do the paired branches of the abdominal aorta supply?
Paired viscera and the abdominal walls.
What viscera does the celiac trunk supply?
Derivatives of the foregut: Abdominal esophagus, stomach, duodenum (up to the major duodenum papilla), liver, pancreas, spleen, and gallbladder.
What viscera does the SMA supply?
Derivatives of the midgut: Duodenum (beyond the major duodenum papilla), jejunum, ileum, appendix, caecum, ascending colon, and the proximal 2/3 of the transverse colon.
What viscera does the IMA supply?
Derivatives of the hindgut: remaing 1/3 of transverse colon, descending colon, sigmoid colon, rectum, and the proximal 1/2 of the anal canal.
How is the blood supply from the celiac trunk, SMA, and IMA, different between the retroperitoneal viscera and intraperitoneal viscera?
The celiac artery gives off direct branches to the retroperitoneal viscera but supplies the intraperitoneal viscera via the mesenteries.
What is the principle venous drainage of the abdominal viscera? What is the exception?
Everything below the diaphragm drains to the IVC except the unpaired abdominal viscera, which first drains to the liver for metabolism via the portal vein.
What veins make up the portal vein?
The splenic vein, superior mesenteric vein, and the inferior mesenteric vein (ie, the derivatives of the primitive gut.) The splenic and the superior mesenteric vein may join together before draining into the portal vein.
