Gut and Peritoneal cavity

Question 1

Define Peritoneum

Answer 1

A thin membrane that lines the walls of of the abdominal cavity and and covers much of the viscera

1. Parietal peritoneum; lines the walls of the cavity
2. Visceral peritoneum; lines covers the viscera
3. Peritoneal cavity; the potential space betweeen the two layers of the peritoneum (lubrication)

Abdominal Viscera are either

1. suspendend in the peritoneal cavity ( by folds of peritoneum-mesenteries)–> INTRAPERITONEAL
2. outside the peritoneal caviity–> RETROPERITONEAL ( one surface or part of the one surface if covered by the peitoneum)

Question 2

Visceral Vs Parietal peritoneum

Answer 2

Visceral

1. innervated by visceral afferents that accompany automoatic (sympathetic and parasympathetic)
2. poorly localized sensations of discomfort and to reflex visceral motor activity

Parietal

1. innervated by somatic afferents carried in branches of the associated spinal nerves
2. sensitive to well localized pain

Question 3

Subdivision of the peritoneal cavity

Answer 3

1. Greater sac
2. Omental bursa

Greater Sac

1. most of the space in the peritoneal cavity
2. begins superiorly at the diaphragm
3. continuing inferiorly into the pelvic cavity
4. it is enterered once the parietal peritoneum is entered

Omental bursa

1. smaller subdivision of the peritoneal cavity
2. posterior to the stomach and liver
3. continuous with the greater sac through an opening –> omental foramen

Sorrounding the Omental foramen

1. anteriorly;
   
   • portal vein
   • hepatic artery proper
   • bile duct
2. posteriorly;
   
   • inferior vena cava
3. superiorly
   
   • caudate lobe of the liver
4. inferiorly
   
   • first part of the duodenum

Question 4

Omenta

Answer 4

• folds that develop from the original dorsal and ventral messenteries
• which suspend the developing gastrointestinal tract in the embryonic coelomic cavity
• consist of two layers of the peritoneum which pass from the stomach and the first part of the duodenum;

1. Greater omentun ( aka greater sac) which is derived from the dorsal mesentery
2. Lesser omentum (aka omentum bursa) which is derived by the ventral mesentary

Greater Omentum

1. large, thin membrane, apron like peritoneal fold
2. contains accumulation of fats (may become substantial in some individuals)
3. attaches to the greater curvature of the stomach and the first part of the duodenum
4. drapes inferiorly over the transverse colon
5. then coils into the jejumum and ileum
6. turning posteriorly it assends to associate with - and become adherent to- the peritoneum
   
   • on the superior surface of the transverse colon
   • on the anterior surface of the transverse mesocolon before arriving at the posterior abdominal wall

Arteries and accompaning veins

1. right and left gastro-omental vessels
2. between the double layered peritoneal apron
3. inferior to the greater curvature of the stomach

Lesser Omentum

1. thin membrane ( continuous of the peritoneal coverings of the anterior and posterior surfaces of the stomach)
2. the other two layered peritoneal omentum
3. extends from the lesser curvature of the stomach and the first part of the duodenum
4. to the inferior surface of the liver
5. divided into ;
   
   • medial hepatogastric ligament–> passes between stomach and liver
   • lateral hepatoduodenal ligament –> passes between duodenum and liver
   • ends latterarly as a free margin and serves the anterior border of the omenta foramen
   • enclosed in this free edge are the hepatic proper artery, bile duct, portal vein, righ and left gastric vessel

Question 5

Messenteries

Answer 5

• peritoneal folds that attach viscera to the posterior abdominal wall
• allow some movement
• provide conduit for vessels, nerves, lymphatics
• subdivided to
  
  • messentery –> associated with parts of the small intestine
  • transverse mesocolon –. associated with transverse colon
  • sigmoid mesocolon–> associated with the sigmoid colon

Messentery

1. large, fan shaped, double layered fold of peritoneum
2. connects the jejunum and ileum to the posterior abdominal wall
3. superior attachment is at the duodenojejunal junction just to the left of the upper lumbar part of the vertebral column
4. passes obliquely downward to the right
5. ends at teh ileocecal junction near the upper body of the right sacro iliac joint
6. in the fat between the two peritoneal layers of the mesentary are the arteries, nerves and lymphatics that supply the jejunum and ileum

Transverse mesocolon

1. connects the transverse colon to the posterior andominal wall
2. its two layers of the peritoneum leave the posterior abdominal wall across the anterior surface of the head and body of the pancreas
3. and pass outward to surround the transverse colon
4. etween the two peritoneal layers of the transverse mesocolon are the arteries, nerves and lymphatics that supply the transverse colon
5. the anterior layer of the transverse mesocolon is adherent to the posterior layer of the greater omentum

Sigmoid mesocolon

1. inverted V-shaped peritoneal fold
2. attaches the sigmoid colon to tthe abdominal wall
3. the apex of V id near the division of the left common iliac artery into its internal and external branches
4. left limb of the descending V –> medial border of the left psoas major muscle
5. right limb of the descending V–> into the pelvis to end at the level of vertbra SIII
6. sigmoid superior rectal vessels along with nerves and lymphatics associated with the sigmoid colon pass throuhg this peritoneal fold

Question 6

Ligaments

Answer 6

consist of two layers of peritoneum that connect two organs to each other or match an organ to the body wall and may form part of the omentum

Question 7

Abdominal Esophagus

Answer 7

• represents the short distal part of the esophagus lacated in the abdominal cavity
• emerges throuhg the right crus of the diaphgram
• level of TX vertebrae
• passes from the esophagus hiatus to the cardial orifice of the stomach just left of the midline

Associated with the esophagus as it enters the abdominal cavity;

1. Anterior vagal trunk
2. Posterior vagal trunk

Anterior Vagal trunk

• consists of several smaller trunks whose fibers mostly come from the left vagus nerve
• rotation of the gut during development moves these trunks to the anterior surface of the esophagus

Poaterior vagal trunk

• consists of a single trunk whose fibers come from the right vagus nerve
• rotational changes of the gut during development move this trunk to the posterior surface of the esophagus

Arterial supply to the abdominal esophagus

1. esophageal branches from left gastric artery ( from celiac trunk)
2. esophageal branches from the left inferior phrenic artery ( from the abdominal aorta)

Question 8

Stomach

Answer 8

• J-like shape
• positioned between the abdominal esophagus and the small intestine
• is positioned in the epigastric, umbilical and left hypochonrium regions of the abdomen

Divided into 4 regions

1. Cardia; surrounds the opening of the esophagus into the stomach
2. Fundusk area above the level of cardial orifice
3. Body; largest region of the stomach
4. Pyloric part; divided into the pyloric antrum and pyloric canal and is the distal end of the stomach

• The most distal portion of the plyoric part of the stomach is the pylorus
• It is marked by the pyloric contriction and contains a thickened ring of gastric circular muscle, the plyoric sphincter that surronds the distal opening of the stomach, the pyloric orifice

Pyloric orifice

1. just to the right of midline in a plane
2. passes through the lower border of vertebrae LI

Other features

1. greater curvature; point of attachment for the greater omentum
2. lesser cervature; point of attachment for the lesser omentum
3. cardial notch; superior angle created when the esophagus enters the stomach
4. angular incisure; bend on the lesser curvature

Arterial supply;

1. left gastric artery from celiac trunk
2. right gastric artery from hepatic artery proper
3. right gastroduodenal artery
4. left gastro-omental artery from the splenic artery
5. posterior gastric artery from the splenic artery

Question 9

Small intestine

Answer 9

• longest part of the gastrointestinal tract
• extends from the pylotic orifice of the stomach to the ileocecal fold
• marroeing diameter from begining to end
• consists of;
  
  • duodenum
  • jejunum
  • ileum

Question 10

Duodenum

Answer 10

• first part of the small intestine
• C-shaped
• adjacent to the head of the pancreas
• 20-25cm long
• above the level of the umbilicus
• its lumen is the widest of the small intestine
• it is retroperitoneal except for its begining which is connected to the liver by the hepatoduodenal ligament, part of the lesser omentum

Divided into four parts;

1. superior
2. descending
3. inferior
4. ascending

Superior;

1. extends from pyloric orifice of the stomach to the neck of the gall blader
2. just to the right of the body of vertebrae LI
3. passes anteriorly to the bile duct , gastroduodenal artery, portal vein and inferior vena cava
4. most uclers occur in this part of the duodenum

Descending;

1. just right to the midline and extends from the neck of the gallblader to the lower border of LIII
2. Its anterior surface is crossed by the transverse colon
3. posterior to it is the right kidney
4. medial to it is the head of the pancreas
5. this part of the duodenum contains major duodenal papilla ( common entry for the bile and pancreatic ducts)
6. and the minor duodenal papilla ( entry for accessory pancreatic duct)

Inferior part;

1. longest section
2. crossing the inferior vena cava , the aorta and the vertebral column
3. crossed anteriorly by the superior mesenteric artery

Ascending part;

1. part that passes upward on to the left of the aorta to approximately the upper border of the LII
2. terminated at the duodenojejunal flexure

tThe duodenojejunal flexure is surronded by a fold of peritoneum containg muscle fibers called the suspensory muscle ligament of the peritoneum

Question 11

Jejunum

Answer 11

1. represents the proximal two fifths of the small intestine
2. it is mostly in the upper quadrant
3. larger in diameter adn thicker walls than the ileum
4. inner mucasal lining of the jejunum is characterized by numerous prominent folds that circle the lumen–> PLICAE CIRCULARES
5. one unique characteristic is the less prominent arterial arcades and longer vasa recta ( straight arteries)

Arterial supply;

• jejunal arteries from the superior mesenteric arerteries

Question 12

Ileum

Answer 12

1. makes the distal three fifths of the small intestine
2. right lower quadrant
3. compared to jejunum
   
   1. thinner walls
   2. smaller diameter
   3. fewer and less prominent mucosal walls ( PLICAE CIRCULARES)
   4. shorter VASA RECTA
   5. more mesenteric fat
   6. more arterial arcades
4. opens in the small intestine where the cecum and the ascending colon join together
5. two flaps are projeccting into the lumen of the large intestinei ( ILEOCECAL FOLD) and surround the opening
6. the two flaps come together at the end forming ridges
7. masculature from the illuem continues into each flap forming a sphincter
8. Functions of the ILEOCECAL FOLD
   
   1. preventing reflux from cecum to ileum
   2. regulating the passage of the contents

Arterial supply

1. ideal arteries from superior mesenteric artery
2. ideal branch from the iliac artery ( from superior mesenteric artery)

Question 13

Large intestine

Answer 13

1. extends from the distal end of the ileum to the anus
2. 1.5 meters in adults
3. absorbs fluids and salts from the gut content ( thus forming feces)
4. consists of the;
   
   1. cecum
   2. appendix
   3. colon
   4. rectum
   5. anal canal
5. Begins in the right groin as the cecum ( associated with appendix)
6. continues upwards as the ascending colon through the right flank and into the right hypochondrium
7. Just bellow the liver it bends to the left forming the right colic flexure (hepatic flexure)
8. crosses the abdomen as the transverse colon to the left hypochondrium
9. Just bellow the spleen it bends downwards forming the left colic flexure (splenic flexure)
10. conitnues as the descending colon through the left flank into the left groin
11. enters the upper part of the pelvic cavity as teh sigmoid colon
12. continues on the superior wall of the pelvic cavity as the rectum
13. terminates at the anal canal

Genaral characteristics

1. large internal diameter
2. peritoneal covered accumulations of fats ( omental appendices)
3. segregations of longitudinal muscles in its wall into three narrow bands ( taeniae coli)
4. scculations of the colon ( haustra of the colon)

Question 14

Cecum and appendix

Answer 14

is the first part of the large intestine

inferior to the ileocecal opening

in the right ileac fossa

intraperitoneal structure because of its mobility ( not because of its suspension in the messentery)
continuous with the ascending colon

usually in contact with the abdominal wall

Question 15

Colon

Answer 15

Extends superiorly from the cecum and consists of the

1. ascending (retroperitoneal)
2. descending (retroperitoneal)
3. transverse (intraperitoneal)
4. sigmoid (intraperitoneal)

Right colic flexure

• the junction of the ascending and transverse colon
• just inferior to the right lobe of the liver

Left colic flexure

• the junction of the transverse and descnding colon
• inferior to the spleen
• higher and more posterior than the left colic flexure
• attached to the diaphgram by the phrenicocolic ligament

Left and right paracolic gutters

• Depressions formed between the lateral margins of the ascending and descending colon and the posteolateral abdominal wall and gutters through which material can pass from one region of the peritoneal cavity to another
• it is a relatively blood-free mobiliazation of the ascending and descending colon is possible by cutting the peritoneum along these lateral paracolic gutters

Final segment of the colon is the sigmoid colon

1. S-shaped strucure
2. begins above the pelvic inlet
3. extends to the levels of vertebrae SIII ( where it continuous with the rectum)
4. quite mobile except at its begining ( where it continues from the descending colon) and the end (where it continuous as the rectum)

Arterial supply to the ascending colon;

1. colic branch form the ileocolic artery ( from superior mesenteric artery)
2. anterior cecal artery from the ileolic artery ( from superior mesenteric artery)
3. posterior cecal artery
4. right colic artery

Arterial supply to the transverse colon

1. right colic artery
2. middle colic artery
3. left colic artery

Arterial supply to the descending colon

1. left colic artery from inferior mesenteric

Arterial supply to the sigmoif colon

1. sigmoidal arteries from inferior mesenteric

Question 16

Rectum and Anal canal

Answer 16

• It extends from the sigmoid colon
• rectosigmoid junction is usually at the begining of the vertebrae SIII
• retroperitoneal structure

Anal cannal; the continuation of the large intestine inferior to the rectum

Arterial supply;;

1. superior rectal artery
2. middle rectal artery
3. inferior rectal artery

Question 17

Liver

Answer 17

• Largest visceral organ
• right hypochondrium and extends into the left hypochondrium

There are two surfaces

1. Diaphragmatic Surface–> in the anterior, posterior and superior directions
2. Visceral surface–> in the inferior direction

Diaphragmatic Surface

1. smooth and doomed
2. lies against the inferior surface of the diaphgram
3. It is associated with
   
   1. the S_ubphrenic recess-_-> seperates the diaphragmatic surface of the liver from the diaphgram and is divided into the right and lest areas by the FALCIFORM LIGAMENT (structure is dderived from the embryonic mesentary)
   2. The Hepatorenal recess--> is part of the peritoneal cavity on the right side between the right kidney adn righ subphrenic gland

Visceral Surface

1. surface of the liver which is covered by visceral peritoneum
2. except at
   
   1. the fossa for the gallblader
   2. the porta hepatis–> serves as a point of entry into the liver for the hepatic arteries and the portal vein and the hepatic ducts

Associated Ligaments

• Liver is attached to the anterior abdominal wall by the FALCIFORM LIGAMENT
• except for a small area against the diaphram ( bare area) the liver is almost completely surrounded by the visceral peritoneum
• Folds of the peritoneum connect the liver to
  
  1. the stomach–> hepatogastric ligament
  2. the duodenum–> hepatoduodenal ligament
  3. the diaphgram–> right and left trangular ligaments + anterior and posterior coronary ligaments
• bare area; part of the diaphgramatic surface of the liver where there’s no intervating peritoneum between the liver and the diaphram
  
  1. Anterior boundary; anterior coronary ligament
  2. Posterior boundary; posterior coronary ligament
  • where the coronary ligaments come together laterally they form the right and left triangular ligaments

Lobes

1. Right (largest) and left (smallest) lobes divided by fossae for the gallbladder adn inferior vena cava
2. Quadrate Lobe;
   
   • arising from the right lobe but is functionally unique
   • visible on teh anterior part of the visceral surface
   • bounded
     
     • on the left; by the FIISSURE of ligamentum teres
     • on the right; by the fossa for the gallblader
3. Caudata Lobe
   
   1. visible on the posterior of the visceral surface
   2. arising from the right lobe but it is functionally unique
   3. bounded
      
      1. on the left by the fissure of the ligamentum venosum
      2. on the right by the groove for the inferior vena cava

Arterial supply;

1. right hepatic artery from the hepatic artery proper ( form the common hepatic artery, from the celiac trunk)
2. left hepatic artery from the hepatic artery proper ( form the common hepatic artery, from the celiac trunk)

Question 18

Gallblader

Answer 18

• pear-shped sac
• lying on the visceral surface of the right lobe of the liver in the fossa between the right and quadrate lobe
• It has;
  
  1. a rounded end; fundus of the gallblader which may project from the inferior border of the liver
  2. a major part of the fossa ( body of the gallblader) which may be against the transverse colon and the superior part of the duodenum
  3. a narrow part ( neck of the gallblader) with mucosal folds forming the spiral fold

Arterial Supply

1. it is the cystic artery from the right hepatic artery, a branch of the hepatic artery proper

The gallblader; receives, concetrates and stores bile from the liver

Question 19

Pancreas

Answer 19

• lies mostly posterior to the stomach
• extends across the posterior abdominal wall from the duodenum to the spleen
• retroperitoneal ( except for a small part of its tail)
• consists of
  
  1. head
  2. uncinate process
  3. neck
  4. body
  5. tail

Head; lies within the C-shaped concavity of the duodenum

Uncinate process; passes posterior to teh superior mesenteric vessels

Neck; is anterior to the superior mesenteric vessels. Posteriorly to the neck of the pancreas the superior mesenteric adn splenic veins join to form the portal vein

Body; is elongate and extends from neck to tail

Tail; passes between layers of the splenorenal ligament

Pancreatic Duct;

• begins in the tail of the pancreas
• passes through the body and when it enters the head it turns inferiorly
• In the lower part of the pancreatic head the pancreatic duct joins the bile duct–> forms the hepatopancreatic ampulla which enters the descending ( second part of the duodenum) at the major duodenal papilla
• sorrounding the ampula is the sphincter of ampula which is a collection of smooth muscles
• the accessory pancreatic duct empties into the deodenum at the minor duodenal papilla ( just above the major duodenal papilla)

The main and accsessory ducts communicate with each other which refelects the embryological origin of the pancreas from the dorsal adn ventral buds from the foregut

Question 20

Duct system from bile

Answer 20

• The duct system extends from the liver, connects with the gallbladder adn empties into the descending part of the duodenum
• The two hepatic ducts combine to form the common hepatic duct
  
  • which runs near the liver with the hepatic artery proper adn portal vein in the free margin of the lesser omentum
• As the common hepatic duct continues to descend it is joined by the cystic duct from the gallbladder
• Bile duct continues to descend passing posteriorly to the superior part of the duodenum before joining with the pancreatic ducts and enter the descending part of the duodenum at the major duodenal papilla

Question 22

Spleen

Answer 22

• develops as part of the vascular system in the part of the dorsal messentary
• lies against the diaphragm in the area of rib 9 to 10
• left upper quadrant/ left hypochondrium
• it is connected to ( both the ligaments are part of the greater omentum)
  
  1. the greater curvature of the stomach–> gastrosplenic ligament ( contains shoer gastric and gastroomental vessels)
  2. the left kidney–> splenorenal ligament ( contains the splenic vessels)
• it is surronded by visceral peritoneum except in the area of the splenic hilium
  
  • ​entry point for the splenic vessels, occasionally the pancreatic tail reaches this area

Arterial supply;

splenic artery from celiac trunk