Anatomy Lecture 3 -- Abdomen 3 Flashcards
Identify the 4 divisions of the stomach
- Cardia
- Fundus
- Body
- Pylorus
2 sphincters associated with the stomach
- Lower esophageal sphincter
- Pyloric sphincter (valve)
2 sphincters at the lower end of the esophagus
- External sphincter (right crus of the diaphragm)
- Internal sphincter (LES)
Anatomically define the external sphincter (right crus of the diaphragm)
Loop of muscle around the esophagus likea sling
Function of the external sphincter (right crus of the diaphragm)
Upon inspiration, constricts the esophagus to prevent the stomach contents from refluxing up the esophagus when intra-abdominal pressure rises during inspiration
Anatomically define the internal sphincter (LES)
A bundle of muscle at the low end of the esophagus, where it meets the stomach
Function of the internal sphincter (LES)
Closed = prevent acid and stomach contents from traveling backwards from the stomach. Not under voluntary control
Define a hiatus hernia (in general)
The protrusion (or herniation) of the upper part of the stomach into the thorax through a tear or weakness in the diaphragm
2 major kinds of hiatus hernias
- Sliding hiatus hernia (most common - 95%)
- Rolling (or paraesophageal) hiatus hernia
Define a sliding hiatus hernia
Gastroesophageal junction moves above the diaphragm together with some of the stomach
Define a rolling (or paraesophageal) hiatus hernia
A part of the stomach herniates through the esophageal hiatus and lies beside the esophagus, without movement of the gastroesophageal junction.
Consequence of a spasmodic contraction of the pyloric sphincter
Prevention of food from passing easily into the duodenum, causing discomfort and vomiting
May occur in 2 - 12 week old infants
Define pyloric stenosis
Narrowing of the opening from the stomach to the first part of the duodenum, due to enlargement (hypertrophy) of the muscle surrounding this opening which spasms when the stomach empties
When does pyloric stenosis most often occur?
In the first few months of life
Consequence of pyloric stenosis
Severe projectile non-bilious vomiting
Identify the 4 parts of the duodenum and their respective lengths
- Superior = ~5 cm
- Descending = ~7 - 10 cm
- Inferior/horizontal = ~ 5 - 7.5 cm
- Ascending = ~5 cm
Describe the anatomy of the first part (superior) of the duodenum (5)
- Begins as a continuation of the duodenal end of the pylorus
- Passes laterally (right) superiorly and posteriorly on the right side of L1, before making a sharp curve inferiorly
- Lies on the transpyloric plane
- Ends at the superior duodenal flexure
- First half is intraperitoneal, connected to liver via the hepatoduodenal ligament
Describe the anatomy of the second part of the duodenum (descending) (4)
- Begins at the superior duodenal flexure
- Passes inferiorly to the lower border of vertebral body 3, before making a sharp turn medially
- Pancreatic duct and bile duct open into it (ampulla of Vater)
- Ends at the inferior duodenal flexure
Describe the anatomy of the third part (inferior/horizontal) of the duodenum (2)
- Begins at the inferior duodenal flexure
- Passes transversely to the left, crossing the right ureter, right testicular/ovarian vessels, IVC, aorta, superior mesenteric artery and vertebral column
Describe the anatomy of the fourth part (ascending) of the duodenum (2)
- Passes superiorly, ascends on the left side of the aorta, up to the level of the upper border of L2 and the inferior border of the body of the pancreas
- Curves anteriorly and terminates at the duodenujejunal flexure (ligament of Treitz)
Important anatomical landmark of the duodenojejunal junction
Ligament of Treitz
Function of the ligament of Treitz
Suspensory muscle that connects the fourth part of the duodenum to the diaphragm
Anterior relations of the first part of the duodenum
- Quadrate lobe of liver
- Gall bladder
Posterior relations of the first part of the duodenum
- Lesser sac (first ~2.5 cm)
- Gastroduodenal artery
- Bile duct
- Portal vein
- Inferior vena cava
Superior relations of the first part of the duodenum
Epiploic foramen
Inferior relations of the first part of the duodenum
Head of the pancreas
Anterior relations of the second part of the duodenum
- Fundus of gall bladder
- Right lobe of liver
- Transverse colon
- Coils of the small intestine
Posterior relations of the second part of the duodenum
- Hilum of right kidney
- Right ureter
Lateral relations of the second part of the duodenum
- Ascending colon
- Right colic flexure
- Right lobe of liver
Medial relations of the second part of the duodenum
- Head of pancreas
- Bile duct
- Main pancreatic duct
Anterior relations of the third part of the duodenum
- Root of mesentery of small intestine
- Superior mesenteric vessels (in root of mesentery)
- Coils of jejunum
Posterior relations of the third part of the duodenum
- Right ureter
- Right psoas muscle
- Inferior vena cava
- Aorta
Superior relations of the third part of the duodenum
Head of pancreas
Inferior relations of the third part of the duodenum
Coilds of jejunum
Anterior relations of the fourth part of the duodenum
- Beginning of root of mesentery of small intestine
- Coils of jejunum
Posterior relations of the fourth part of the duodenum
- Left margin of aorta
- Medial border of left psoas muscle
Sphincter between small intestine and large intestine
Ileocecal valve
3 ways to differentiate between the jejunum and ileum
- Ileum has more fat inside the mesentery
- Only the ileum has abundant Peyer’s patches
- The jejunum had fewer arterial arcades and longer straight arteries (vasa recta)
Most common congenital abnormality of the small intestine
Meckel’s diverticulum
Cause of Meckel’s diverticulum
An incomplete obliteration of the vitelline duct (connects the fetus to the yolk sac through the umbilical cord)
Location of Meckel’s diverticulum
Distal ileum, usually within about 60 - 100 cm (2 feet) of the ileocecal valve
Describe the physical features of Meckel’s diverticulum
Blind segment or small pouch, about 3 - 6 cm long and may have a greater lumen diameter than that of the ileum
Define intussusception
A medical condition in which a part of the intestine has invaginated into another section of intestine, similar to the way in which the parts of a collapsible telescope slide into one another
Define McBurney’s point
Point located 1/3 of the distance from the ASIS to the navel. Roughly correspends to the most common location of the base of the appendix where it is attached to the cecum
Clinical relevance of McBurney’s point
Specific localization of tenderness at this point = inflammation no longer limited to the lumen of the bowel (pain is poorly localized there), and is irritating the lining of the peritoneum at the place where the peritoneum comes into contact with the appendix. Therefore suggests the evolution of acute appendicitis to a later stage –> increased likelihood of rupture
List the parts of the colon from the small intestine to the anus
- Cecum
- Ascending colon
- Hepatic flexure
- Transverse colon
- Splenic flexure
- Descending colon
- Sigmoid colon
- Rectum
Define haustra
Small pouches in the colon caused by sacculation, which give the colon its segmented appearance
How are haustra formed?
Because the taenia coli is shorts than the intestine, sacculation occurs between the taenia
Define haustral contractions
Slow segmenting movements that occur every 25 minutes. One haustrum distends as it fills, which stimulates muscles to contract, pushing contents to the next haustrum
Define epiploic appendices
Small pouches of the peritoneum filled with fat and situated along the colon and upper part of the rectum. Mostly appended to the transverse and sigmoid parts of the colon
Define diverticulosis
Outpocketings of the colonic mucosa and submucosa through weaknesses of muscle layers in the colon wall.
Where is diverticulosis most common and why?
Sigmoid colon since its is a common place for increased pressure
Define volvulus
A loop of bowel that has completely twisted around its site of mesenteric attachment
Two mechanisms caused by volvulus and their associated symptoms
- Bowel obstruction –> abdominal distension, vomiting, lack of defecation
- Ischemia to the affected portion of intestine
3 muscles in the anorectal area
- Levator ani muscle
- Internal anal sphincter muscle
- External anal sphincter muscle
3 main arteries from the dorsal aorta that supply the abdominal GI organs
- Celiac trunk
- Superior mesenteric artery
- Inferior mesenteric artery
Draw out and label the main arteries that branch off from the celiac trunk and the main vessels that branch off from them***
From where does the superior mesenteric artery branch off on the aorta?
The front of the aorta at the level of L1
From the left side of the superior mesenteric artery, what branches off?
Jejunal and ileal arteries to the jejunum and ileum
From the right side of the superior mesenteric artery, what branches off?
- Ileocolic artery
- RIght and middle colic arteries
What organs does the ileocolic artery supply?
- Terminal part of the ileum
- Cecum
- Appendix
- Lower part of the ascending colon
What organs do the right and middle colic arteries supply?
Upper part os the ascending colon and the transverse colon
From where does the inferior mesenteric artery branch off?
The front of the aorta at the level of L3
What does the inferior mesenteric artery branch off into?
- Left colic artery
- SIgmoid arteries
- Superior rectal artery
What do the branches of the inferior mesenteric artery supply?
- Last part of the transverse colon
- Descending colon
- Sigmoid colon
- Upper part of the rectum
4 important veins draining the abdominal organs
- Portal vein
- Splenic vein
- Inferior mesenteric vein
- Superior mesenteric vein
Portocaval anastomoses of the venous drainage system of the abdominal organs
- Esophageal
- Paraumbilical
- Rectal
- Retroperitoneal
Define paraumbilical veins
Small veins in the course of ligamentum teres and the median umbilical ligament
Define portocaval hypertension
High blood pressure in the portal vein system caused by liver disease
Consequences of portocaval hypertension
Blood being forced down alternate channels (esophageal and anorectal varices, or paraumbilical veins) by the increased resistance to flow through the systemic venous system rather than the portal system
