Blood supply of the GIT pdf - Abdomen

Basic Anatomy

191

vitelline duct

cephalic limb of midgut loop

caudal limb of midgut loop

cecum

appendix

cecum

appendix

ascending colon

ileum

appendix

cecum

FIGURE 5.43

Stages in the development of the cecum and appendix. The final stages of development (stages 4, 5, and 6)

take place after birth.

abdominal cavity

dorsal mesentery

greater curvature

of stomach

remains of

extraembryonic coelom

vitelline duct

umbilical cord

developing cecum

superior

mesenteric

artery

developing cecum

FIGURE 5.44

Left-side views of the counterclockwise 90° rotation of the midgut loop while it is in the extraembryonic coelom

gastroepiploic artery (Fig. 5.20).

They anastomose with the left gastric artery and the left

fundus of the stomach in the gastrosplenic omentum.

arise from the end of the splenic artery and reach the

five or six in number,

short gastric arteries,

The

right gastroepiploic artery (Fig. 5.20).

layers of the greater omentum. It anastomoses with the

along the greater curvature of the stomach between the

ach in the gastrosplenic omentum. It passes to the right

the spleen and reaches the greater curvature of the stom

arises near the hilum of

left gastroepiploic artery

The

Pancreatic branches.

Branches

hilum of the spleen (Fig. 5.11).

the artery enters the splenicorenal ligament and runs to the

in the umbilical cord.

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192

CHAPTER 5

ach. It anastomoses with the left gastric artery (Fig. 5.20).

lesser omentum along the lesser curvature of the stom

the upper border of the pylorus and runs to the left in the

arises from the hepatic artery at

right gastric artery

The

Branches

ply the corresponding lobes of the liver.

porta hepatis, it divides into right and left branches to sup

left of the bile duct and in front of the portal vein. At the

front of the opening into the lesser sac and is placed to the

layers of the lesser omentum (Figs. 5.7 and 5.11). It lies in

forward and to the right and then ascends between the

The medium-size hepatic artery* runs

Hepatic Artery.

The Abdomen: Part II—The Abdominal Cavity

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stomach

abdominal cavity

remains of

extraembryonic coelom

umbilical cord

cecum

superior

mesenteric

artery

abdominal cavity

extraembryonic

coelom

stomach

jejunum

superior

mesenteric

artery

cecum

stomach

cecum

developing appendix

ileum

jejunum

colon

descent of cecum

FIGURE 5.45

The descent of the cecum takes place later.

abdominal cavity.

Left-side views of the counterclockwise 180° rotation of the midgut loop as it is withdrawn into the

A, B:

below the celiac artery (Fig. 5.32) and runs downward and

colon. It arises from the front of the abdominal aorta just

appendix, the ascending colon, and most of the transverse

the duodenum, the jejunum, the ileum, the cecum, the

The superior mesenteric artery supplies the distal part of

Superior Mesenteric Artery

which runs to the neck of the gallbladder (Fig. 5.47).

cystic artery,

The right hepatic artery usually gives off the

enter the porta hepatis.

left hepatic arteries

right

The

(Figs. 5.4 and 5.20).

ond part of the duodenum and the head of the pancreas

that descends between the sec

creaticoduodenal artery

superior pan

layers of the greater omentum and the

along the greater curvature of the stomach between the

that runs

right gastroepiploic artery

divides into the

descends behind the first part of the duodenum. It

is a large branch that

gastroduodenal artery

The

, which is the remainder of the artery.

proper

hepatic artery

its origin to the gastroduodenal branch, and the

, which extends from

common hepatic artery

divided into the

*For purposes of description, the hepatic artery is sometimes

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-

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and

Basic Anatomy

that anastomoses with

superior branch

It gives rise to a

passes downward and to the right.

ileocolic artery

The

and divides into ascending and descending branches.

artery. It passes to the right to supply the ascending colon

is often a branch of the ileocolic

right colic artery

The

into right and left branches.

mesocolon to supply the transverse colon and divides

runs forward in the transverse

middle colic artery

The

part of the duodenum.

the pancreas. It supplies the pancreas and the adjoining

der of the third part of the duodenum and the head of

right as a single or double branch along the upper bor

passes to the

inferior pancreaticoduodenal artery

The

Branches

its own ileocolic branch.

intestine and ends by anastomosing with the ileal branch of

the right between the layers of the mesentery of the small

the third part of the duodenum. It continues downward to

to the right behind the neck of the pancreas and in front of

193

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ventral mesentery

liver

vitelline duct

yolk sac

allantois

proctodeum

cloaca

umbilical arteries

stomach

dorsal mesentery

spleen

foregut artery
(celiac artery)

midgut artery
(superior mesenteric
artery)

hindgut artery (inferior
mesenteric artery)

FIGURE 5.46

Formation of the midgut loop (

axis for the future rotation of the midgut loop.

). Note how the superior mesenteric artery and the vitelline duct form an

shaded

left hepatic artery

gastroduodenal artery

portal vein

porta hepatis

left hepatic duct

right hepatic duct

common hepatic duct

neck

right hepatic artery

cystic artery

gallbladder

body

fundus

cystic duct

left gastric artery

celiac artery

splenic artery

hepatic artery

right gastric artery

bile duct

FIGURE 5.47

Structures entering and leaving the porta hepatis.

194

CHAPTER 5

moses less freely with the superior rectal artery (Fig. 5.36).

the superior mesenteric artery, and it ends where it anasto

junction, where it anastomoses with the ileal branches of

This begins at the ileocecal

marginal artery.

called the

margin of the large intestine forms a single arterial trunk

The anastomosis of the colic arteries around the concave

Marginal Artery

inferior rectal arteries.

anal canal and anastomoses with the middle rectal and

The artery supplies the rectum and upper half of the

artery. It descends into the pelvis behind the rectum.

rior mesenteric artery as it crosses the left common iliac

is a continuation of the infe

superior rectal artery

The

supply the descending and sigmoid colon.

are two or three in number and

sigmoid arteries

The

divides into ascending and descending branches.

flexure, and the upper part of the descending colon. It

plies the distal third of the transverse colon, the left colic

runs upward and to the left and sup

left colic artery

The

Branches

iliac artery. Here, it becomes the superior rectal artery.

runs downward and to the left and crosses the left common

1.5 in. (3.8 cm) above its bifurcation (Fig. 5.36). The artery

of the anal canal. It arises from the abdominal aorta about

colon, the sigmoid colon, the rectum, and the upper half

the transverse colon, the left colic flexure, the descending

The inferior mesenteric artery supplies the distal third of

Inferior Mesenteric Artery

minal arcades, small straight vessels supply the intestine.

supply the jejunum than supply the ileum. From the ter

second, third, and fourth series of arcades. Fewer arcades

Branches from the arcades divide and unite to form a

unite with adjacent branches to form a series of arcades.

(Fig. 5.32). Each artery divides into two vessels, which

arise from the left side of the superior mesenteric artery

are 12 to 15 in number and

jejunal and ileal branches

The

of the posterior cecal artery (Fig. 5.33).

is a branch

appendicular artery

rior cecal arteries;

poste

anterior

The inferior branch gives rise to the

tomoses with the end of the superior mesenteric artery.

that anas

inferior branch

the right colic artery and an

The Abdomen: Part II—The Abdominal Cavity

and

the

■

the foregut (which includes the distal third of the esophagus,

mesenteric, and pancreatic veins.

It receives the short gastric, left gastroepiploic, inferior

neck of the pancreas to form the portal vein (Fig. 5.48).

It unites with the superior mesenteric vein behind the

and passes to the right in the splenicorenal ligament.

This vein leaves the hilum of the spleen

Splenic vein:

tric vein, right gastric vein, and cystic veins.

vein are the splenic vein, superior mesenteric vein, left gas

The tributaries of the portal

Tributaries of the Portal Vein

tum, see Figures 5.7 and 5.11.

For the relations of the portal vein in the lesser omen

soids within the liver.

organs it drains and ends by emptying its blood into sinu

The portal circulation begins as a capillary plexus in the

where it divides into right and left terminal branches.

front of the opening into the lesser sac to the porta hepatis,

lesser omentum (Figs. 5.7 and 5.11). It then runs upward in

right, behind the first part of the duodenum, and enters the

rior mesenteric and splenic veins (Fig. 5.48). It ascends to the

behind the neck of the pancreas by the union of the supe

cava. The portal vein is about 2 in. (5 cm) long and is formed

blood passes into the hepatic veins that join the inferior vena

vein enters the liver and breaks up into sinusoids, from which

blood from the spleen, pancreas, and gallbladder. The portal

the esophagus to halfway down the anal canal; it also drains

nal part of the gastrointestinal tract from the lower third of

The portal vein (Fig. 5.22) drains blood from the abdomi

Portal Vein (Hepatic Portal Vein)

inferior mesenteric arteries.

to the branches of the celiac artery and the superior and

vein, but the veins forming the distal tributaries correspond

The proximal tributaries drain directly into the portal

portal venous system.

tinal tract and its accessory organs drains to the liver by the

The venous blood from the greater part of the gastrointes

Venous Drainage

which represents the fused pair of

the stomach, and the proximal half of the duodenum) is sup-

plied by a number of vessels that fuse to form a single trunk,

the celiac artery (Fig. 5.46). It is interesting to note that this

artery also supplies the liver and pancreas, which are glan-

dular derivatives of this part of the gut. The spleen is also

supplied by the same artery, which is not surprising, since

this organ develops in the dorsal mesentery of the foregut;

the artery to the spleen runs in the splenicorenal ligament.

Midgut Artery
The midgut, which extends from halfway along the second

part of the duodenum to the left colic flexure, is supplied by the
superior mesenteric artery,

vitelline arteries (Fig. 5.46).

Hindgut Artery
The hindgut, which extends from the left colic flexure to half-

way down the anal canal, is supplied by the inferior mesen-
teric artery (Fig. 5.46). This represents a number of ventral

branches of the aorta that fuse to form a single artery.

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Explanation for the Blood Supply to the

and esophageal branches from the aorta. The caudal end of

and the cervical and thoracic portions of the esophagus are

Gastrointestinal Tract

Foregut Arteries
The cephalic end of the foregut (which includes the pharynx)

supplied by the ascending pharyngeal arteries, palatine arter-

ies, superior and inferior thyroid arteries, bronchial arteries,

E M B R Y O L O G I C N O T E S

(continued)

Basic Anatomy

(Fig. 5.22).

der directly into the liver or join the portal vein

These veins either drain the gallblad

Cystic veins:

into the portal vein (Fig. 5.22).

the lesser curvature of the stomach and drains directly

This vein drains the right portion of

Right gastric vein:

(Fig. 5.22).

of the esophagus. It opens directly into the portal vein

the lesser curvature of the stomach and the distal part

This vein drains the left portion of

Left gastric vein:

pancreaticoduodenal, and right gastroepiploic veins.

jejunal, ileal, ileocolic, right colic, middle colic, inferior

behind the neck of the pancreas (Fig. 5.48). It receives the

the third part of the duodenum and joins the splenic vein

of the mesentery of the small intestine. It passes in front of

This vein ascends in the root

Superior mesenteric vein:

rior rectal veins, the sigmoid veins, and the left colic vein.

the body of the pancreas (Fig. 5.48). It receives the supe

posterior abdominal wall and joins the splenic vein behind

This vein ascends on the

Inferior mesenteric vein:

195

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inferior vena cava

portal vein

duodenum

head of pancreas

superior mesenteric vein

uncinate process of pancreas

inferior mesenteric vein

spleen

body of pancreas

splenic vein

FIGURE 5.48

Formation of the portal vein behind the neck of the pancreas.

Portal–Systemic Anastomoses

whereas the left lobe plus the quadrate and caudate lobes

right lobe of the liver receives blood mainly from the intestine,

leads to streaming of the blood flow in the portal vein. The

vein with the superior mesenteric vein to form the portal vein

via the hepatic artery. The wide angle of union of the splenic

remaining 30% is oxygenated blood, which passes to the liver

The portal vein conveys about 70% of the blood to the liver. The

may be anastomosed to the left renal vein after removing the

cava behind the entrance into the lesser sac. The splenic vein

the lesser omentum, to the anterior wall of the inferior vena

involve the anastomosis of the portal vein, because it lies within

for the treatment of portal hypertension may

accompanied by congestive enlargement of the spleen.

Enlargement of the portal–systemic connections is frequently

list of portal–systemic anastomoses should be remembered.

Portal hypertension is a common clinical condition; thus, the

mose with the middle and inferior rectal veins (systemic trib

esophageal veins draining the middle third of the esophagus

At the lower third of the esophagus, the esophageal branches

the portal and systemic systems, and they become important

route. However, other, smaller communications exist between

Under normal conditions, the portal venous blood traverses

the liver and drains into the inferior vena cava of the systemic

venous circulation by way of the hepatic veins. This is the direct

when the direct route becomes blocked (Fig. 5.49).

These communications are as follows:

■

of the left gastric vein (portal tributary) anastomose with the

into the azygos veins (systemic tributary).

■

Halfway down the anal canal, the superior rectal veins (portal

tributary) draining the upper half of the anal canal anasto-

utaries), which are tributaries of the internal iliac and internal

pudendal veins, respectively.

■

The paraumbilical veins connect the left branch of the portal

vein with the superficial veins of the anterior abdominal wall

(systemic tributaries). The paraumbilical veins travel in the

falciform ligament and accompany the ligamentum teres.

■

The veins of the ascending colon, descending colon, duode-

num, pancreas, and liver (portal tributary) anastomose with

the renal, lumbar, and phrenic veins (systemic tributaries).

Portal Hypertension

Portacaval shunts

spleen.

Blood Flow in the Portal Vein and Malignant Disease

receive blood from the stomach and the spleen. This distribu-

tion of blood may explain the distribution of secondary malig-

nant deposits in the liver.

C L I N I C A L N O T E S

196

CHAPTER 5

extends to the left to reach the left hemidiaphragm. The

it from the pleura, lungs, pericardium, and heart. The liver

right costal margin, and the right hemidiaphragm separates

The greater part of the liver is situated under cover of the

the abdominal cavity just beneath the diaphragm (Fig. 5.1).

The liver is soft and pliable and occupies the upper part of

conveyed to the duodenum by the biliary ducts.

blood corpuscles and secretes bile salts; these together are

duces bile pigments from the hemoglobin of worn-out red

stance, and has an important detoxicating function. It pro

The liver synthesizes heparin, an anticoagulant sub

the intestine.

that have gained entrance to the blood from the lumen of

of the blood, removing bacteria and other foreign particles

to carbohydrate, fat, and protein metabolism; and filtration

tinal tract; involvement in many metabolic activities related

duction and secretion of bile, which is passed into the intes

variety of functions. Three of its basic functions are pro

The liver is the largest gland in the body and has a wide

Location and Description

Gastrointestinal Tract

tine; these are absent in the large intestine (Fig. 5.50).

are found in the mucous membrane of the small intes

Peyer’s patches

Aggregations of lymphoid tissue called

which are absent in the large intestine.

The mucous membrane of the small intestine has villi,

in the large intestine.

which are absent

plicae circulares,

manent folds, called

The mucous membrane of the small intestine has per

Internal Differences

the large intestine is sacculated (Fig. 5.50).

The wall of the small intestine is smooth, whereas that of

epiploicae.

appendices

The large intestine has fatty tags, called the

The small intestine has no fatty tags attached to its wall.

(Fig. 5.50).

muscle is collected into three bands, the teniae coli

(with the exception of the appendix), the longitudinal

continuous layer around the gut. In the large intestine

The longitudinal muscle of the small intestine forms a

midline into the right iliac fossa.

num) has a mesentery that passes downward across the

The small intestine (with the exception of the duode

of the filled large intestine.

The caliber of the full small intestine is smaller than that

parts of the colon are fixed.

num) is mobile, whereas the ascending and descending

The small intestine (with the exception of the duode

External Differences

The Abdomen: Part II—The Abdominal Cavity

Differences Between the Small and

Large Intestine

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Accessory Organs of the

Liver

-
-

inferior vena cava

phrenic veins

tributaries of azygos veins

esophageal tributaries of left gastric vein

veins on posterior
abdominal wall

colic veins

superficial veins of anterior abdominal wall

superior rectal vein

middle and inferior rectal veins

umbilicus

paraumbilical veins

liver

FIGURE 5.49

Important portal–systemic anastomoses.