Small intestine pdf - Abdomen

174

CHAPTER 5

The Abdomen: Part II—The Abdominal Cavity

anterior vagal trunk

hepatic branch

pyloric branch

celiac branch

posterior vagal trunk

FIGURE 5.24

Distribution of the anterior and posterior vagal trunks within the abdomen. Note that the celiac branch of the

posterior vagal trunk is distributed with the sympathetic nerves as far down the intestinal tract as the left colic flexure.

Trauma to the Stomach

tric mucous membrane is possible. It is also possible to perform

Gastroscopy is the viewing of the mucous membrane of the

bloc and, with it, its lymphatic field. The continuity of the gut is

cal operation is a desperate attempt to remove the stomach en

the greater curvature, along with the greater omentum. This radi

along the lesser curvature of the stomach; and the nodes along

and body of the pancreas and their associated nodes; the nodes

and their associated lymph nodes; the splenic vessels; the tail

the spleen and the gastrosplenic and splenicorenal ligaments

lower end of the esophagus and the first part of the duodenum;

treated by total gastrectomy, which includes the removal of the

nodes. For these reasons, malignant disease of the stomach is

or bypass the local lymph nodes and are held up in the regional

away from the primary site. Cancer cells also often pass through

cer cells to travel to different parts of the stomach, some distance

Because the lymphatic vessels of the mucous membrane and

and is referred to the epigastrium. It is believed that the pain-

blunt trauma to the abdomen. However, its large size makes it

Apart from its attachment to the esophagus at the cardiac orifice

and its continuity with the duodenum at the pylorus, the stomach

is relatively mobile. It is protected on the left by the lower part

of the rib cage. These factors greatly protect the stomach from

vulnerable to gunshot wounds.

Gastric Ulcer

The mucous membrane of the body of the stomach and, to a

lesser extent, that of the fundus produce acid and pepsin. The

secretion of the antrum and pyloric canal is mucous and weakly

alkaline (Fig. 5.25). The secretion of acid and pepsin is controlled

by two mechanisms: nervous and hormonal. The vagus nerves

are responsible for the nervous control, and the hormone gas-
trin, produced by the antral mucosa, is responsible for the hor-

monal control. In the surgical treatment of chronic gastric and

duodenal ulcers, attempts are made to reduce the amount of

acid secretion by sectioning the vagus nerves (vagotomy) and by

removing the gastrin-bearing area of mucosa, the antrum (partial

gastrectomy).

Gastric ulcers occur in the alkaline-producing mucosa of the

stomach, usually on or close to the lesser curvature. A chronic

ulcer invades the muscular coats and, in time, involves the peri-

toneum so that the stomach adheres to neighboring structures.

An ulcer situated on the posterior wall of the stomach may per-

forate into the lesser sac or become adherent to the pancreas.

Erosion of the pancreas produces pain referred to the back. The

splenic artery runs along the upper border of the pancreas, and

erosion of this artery may produce fatal hemorrhage. A penetrat-

ing ulcer of the anterior stomach wall may result in the escape

of stomach contents into the greater sac, producing diffuse peri-

tonitis. The anterior stomach wall may, however, adhere to the

liver, and the chronic ulcer may penetrate the liver substance.

Gastric Pain

The sensation of pain in the stomach is caused by the stretch-

ing or spasmodic contraction of the smooth muscle in its walls

transmitting fibers leave the stomach in company with the sym-

pathetic nerves. They pass through the celiac ganglia and reach

the spinal cord via the greater splanchnic nerves.

Cancer of the Stomach

submucosa of the stomach are in continuity, it is possible for can-

restored by anastomosing the esophagus with the jejunum.

Gastroscopy

stomach through an illuminated tube fitted with a lens system.

The patient is anesthetized, and the gastroscope is passed into

the stomach, which is then inflated with air. With a flexible fiber-

optic instrument, direct visualization of different parts of the gas-

a mucosal biopsy through a gastroscope.

(continued)

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

Basic Anatomy

175

Nasogastric Intubation

Nasogastric intubation is a common procedure and is performed

to empty the stomach, to decompress the stomach in cases of

intestinal obstruction, or before operations on the gastrointesti-

nal tract; it may also be performed to obtain a sample of gastric

juice for biochemical analysis.
1.

The patient is placed in the semiupright position or left lateral

position to avoid aspiration.

The well-lubricated tube is inserted through the wider nostril

and is directed backward along the nasal floor.

Once the tube has passed the soft palate and entered the oral

pharynx, decreased resistance is felt, and the conscious pa-

tient will feel like gagging.

Some important distances in the adult may be useful. From

The root of the mesentery of the small intes

Anteriorly:

The relations of this part are as follows:

ing the lower margin of the head of the pancreas (Figs. 5.26

plane, passing in front of the vertebral column and follow

duodenum runs horizontally to the left on the subcostal

The third part of the

Third Part of the Duodenum

the main pancreatic duct (Figs. 5.27 and 5.28)

The head of the pancreas, the bile duct, and

Medially:

and the right lobe of the liver (Fig. 5.27)

The ascending colon, the right colic flexure,

Laterally:

ureter (Fig. 5.27)

The hilum of the right kidney and the right

Posteriorly:

small intestine (Fig. 5.29)

lobe of the liver, the transverse colon, and the coils of the

The fundus of the gallbladder and the right

Anteriorly:

The relations of this part are as follows:

nal papilla (Figs. 5.27 and 5.28).

into the duodenum a little higher up on the minor duode

(Fig. 5.28). The accessory pancreatic duct, if present, opens

that opens on the summit of the major duodenal papilla

pierce the duodenal wall. They unite to form the ampulla

medial border, the bile duct and the main pancreatic duct

bar vertebrae (Figs. 5.26 and 5.27). About halfway down its

the right kidney on the right side of the 2nd and 3rd lum

denum runs vertically downward in front of the hilum of

The second part of the duo

Second Part of the Duodenum

The head of the pancreas (Fig. 5.26)

Inferiorly:

loic foramen) (Figs. 5.7 and 5.11)

The entrance into the lesser sac (the epip

Superiorly:

the inferior vena cava (Fig. 5.27)

troduodenal artery, the bile duct and the portal vein, and

The lesser sac (first inch only), the gas

Posteriorly:

bladder (Fig. 5.10)

The quadrate lobe of the liver and the gall

Anteriorly:

The relations of this part are as follows:

tebra (Figs. 5.26 and 5.27).

on the transpyloric plane at the level of the 1st lumbar ver

num begins at the pylorus and runs upward and backward

The first part of the duode

First Part of the Duodenum

four parts.

regions and, for purposes of description, is divided into

The duodenum is situated in the epigastric and umbilical

Parts of the Duodenum

only partially covered by peritoneum.

The remainder of the duodenum is retroperitoneal, being

lower border; the lesser sac lies behind this short segment.

its upper border and the greater omentum attached to its

neuver opens the normally collapsed esophagus and permits

the esophagus (11.2 in. [28 cm]), and where the esophagus

curved course taken by the tube from the cardiac orifice to

the nostril (external nares) to the cardiac orifice of the stom-

ach is about 17.2 in. (44 cm), and from the cardiac orifice to

the pylorus of the stomach is 4.8 to 5.6 in. (12 to 14 cm). The

the pylorus is usually longer, 6.0 to 10.0 in. (15 to 25 cm) (see

Fig. 3.51).

Anatomic Structures That May Impede the Passage
of the Nasogastric Tube

■

A deviated nasal septum makes the passage of the tube
difficult on the narrower side.

■

Three sites of esophageal narrowing may offer resistance

to the nasogastric tube—at the beginning of the esopha-

gus behind the cricoid cartilage (7.2 in. [18 cm]), where the

left bronchus and the arch of the aorta cross the front of

enters the stomach (17.2 in. [44 cm]). The upper esophageal

narrowing may be overcome by gently grasping the wings of

the thyroid cartilage and pulling the larynx forward. This ma-

the tube to pass down without further delay.

Anatomy of Complications

■

The nasogastric tube enters the larynx instead of the esopha-

gus.

■

Rough insertion of the tube into the nose will cause nasal

bleeding from the mucous membrane.

■

Penetration of the wall of the esophagus or stomach. Always

aspirate tube for gastric contents to confirm successful

entrance into the stomach.

■

and 5.27).

■

and coils of jejunum (Figs. 5.26 and 5.27)

tine, the superior mesenteric vessels contained within it,

FIGURE 5.25

Areas of the stomach that produce acid and

pepsin (blue) and alkali and gastrin (red).

176

CHAPTER 5

and coils of jejunum (Fig. 5.30)

The beginning of the root of the mesentery

Anteriorly:

The relations of this part are as follows:

attached to the right crus of the diaphragm (Fig. 5.12).

which is

ligament of Treitz,

tion by a peritoneal fold, the

(Figs. 5.26 and 5.27). The flexure is held in posi

flexure

duodenojejunal

denum runs upward and to the left to the

The fourth part of the duo

Fourth Part of the Duodenum

Coils of jejunum

Inferiorly:

The head of the pancreas (Fig. 5.26)

Superiorly:

inferior vena cava, and the aorta (Fig. 5.27)

The right ureter, the right psoas muscle, the

Posteriorly:

The Abdomen: Part II—The Abdominal Cavity

■

inferior vena cava

portal vein

bile duct

superior

pancreaticoduodenal

artery

right colic

flexure

inferior

pancreaticoduodenal

artery

ascending colon

head of pancreas

superior mesenteric vein

superior mesenteric artery

descending colon

inferior mesenteric vein

left testicular vein

body of pancreas

left colic flexure

tail of pancreas

splenic artery

neck of pancreas

suprarenal glands

FIGURE 5.26

Pancreas and anterior relations of the kidneys.

inferior vena cava

portal vein

bile duct

right kidney

right

colic flexure

psoas muscle

right testicular artery

right ureter

abdominal aorta

inferior mesenteric artery

left ureter

left testicular artery

inferior mesenteric vein

left renal vein

left kidney

suprarenal gland

diaphragm

hepatic artery

superior mesenteric artery

FIGURE 5.27

Posterior relations of the duodenum and the pancreas. The numbers represent the four parts of the duodenum.

Basic Anatomy

der of the duodenum, it is thrown into numerous circular

part of the duodenum, it is smooth (Fig. 5.28). In the remain

of the duodenum is thick. In the first

mucous membrane

The

Mucous Membrane and Duodenal Papillae

border of the left psoas muscle (Fig. 5.27)

The left margin of the aorta and the medial

Posteriorly:

177

■

superior
mesenteric
artery

ileocecal
junction

duodenojejunal
flexure

root of mesentery
of small intestine

FIGURE 5.30

Attachment of the root of the mesentery of the

mesentery of the small

fold of peritoneum known as the

attached to the posterior abdominal wall by a fan-shaped

The coils of jejunum and ileum are freely mobile and are

flexure, and the ileum ends at the ileocecal junction.

one to the other. The jejunum begins at the duodenojejunal

has distinctive features, but there is a gradual change from

upper two fifths of this length make up the jejunum. Each

The jejunum and ileum measure about 20 ft (6 m) long; the

Location and Description

Jejunum and Ileum

teric plexuses.

thetic (vagus) nerves from the celiac and superior mesen

The nerves are derived from sympathetic and parasympa

the origin of the superior mesenteric artery.

coduodenal nodes to the superior mesenteric nodes around

and then to the celiac nodes and downward via pancreati

pancreaticoduodenal nodes to the gastroduodenal nodes

The lymph vessels follow the arteries and drain upward via

Lymph Drainage

mesenteric vein (Fig. 5.22).

into the portal vein; the inferior vein joins the superior

The superior pancreaticoduodenal vein drains

Veins

superior mesenteric artery.

the inferior pancreaticoduodenal artery, a branch of the

artery (Figs. 5.20 and 5.26). The lower half is supplied by

creaticoduodenal artery, a branch of the gastroduodenal

The upper half is supplied by the superior pan

Arteries

about 0.75 in. (1.9 cm) above the major duodenal papilla.

if present, opens into the duodenum on a smaller papilla

(Fig. 5.28). The accessory pancreatic duct,

duodenal papilla

major

the second part is a small, rounded elevation called the

duct and the main pancreatic duct pierce the medial wall of

At the site where the bile

plicae circulares.

folds called the

superior mesenteric artery lies in the root of the mesentery.

downward, and to the right to the ileocecal junction. The

extends from the duodenojejunal flexure on left of the aorta,

small intestine to the posterior abdominal wall. Note that it

Blood Supply

Nerve Supply

-
-

smooth mucous membrane

plicae
circulares

major
duodenal papilla

bile duct

accessory pancreatic
duct

main pancreatic
duct

FIGURE 5.28

Entrance of the bile duct and the main and

accessory pancreatic ducts into the second part of the

duodenum. Note the smooth lining of the first part of the

duodenum, the plicae circulares of the second part, and the

major duodenal papilla.

left hepatic duct

portal vein

lesser omentum

hepatic artery

accessory pancreatic
duct

main pancreatic duct

transverse colon

second part of
duodenum

right hepatic duct

common hepatic duct

cystic duct

bile duct

neck

fundus

gallbladder

body

FIGURE 5.29

The bile ducts and the gallbladder. Note the

relation of the gallbladder to the transverse colon and the

duodenum.

178

CHAPTER 5

ileum by the following features:

In the living, the jejunum can be distinguished from the

mesentery.

the space between the two layers of peritoneum forming the

mesenteric artery and vein, lymph vessels, and nerves into

permits the entrance and exit of the branches of the superior

region of the right sacroiliac joint. The root of the mesentery

right from the left side of the 2nd lumbar vertebra to the

nal wall along a line that extends downward and to the

ous with the parietal peritoneum on the posterior abdomi

the mobile intestine. The short root of the fold is continu

(Fig. 5.30). The long free edge of the fold encloses

intestine

The Abdomen: Part II—The Abdominal Cavity

-
-

Trauma to the Duodenum

gallbladder wall into the duodenum. Operations on the colon and

been reported in which a large gallstone ulcerated through the

colon, and the right kidney should be remembered. Cases have

The relation to the duodenum of the gallbladder, the transverse

The importance of the duodenal recesses and the occurrence of

ferential diagnosis between a perforated duodenal ulcer and a

paracolic gutter and thus down to the right iliac fossa. The dif

transverse colon directs the escaping fluid into the right lateral

upper part of the greater sac, above the transverse colon. The

rior wall of the first inch of the duodenum may perforate into the

production of a duodenal ulcer at this site. An ulcer of the ante

of the duodenum. This is thought to be an important factor in the

chyme is squirted against the anterolateral wall of the first part

As the stomach empties its contents into the duodenum, the acid

away from crush injuries. In severe crush injuries to the anterior

terior abdominal wall by peritoneum and therefore cannot move

Apart from the first inch, the duodenum is rigidly fixed to the pos-

abdominal wall, the third part of the duodenum may be severely

crushed or torn against the third lumbar vertebra.

Duodenal Ulcer

perforated appendix may be difficult.

An ulcer of the posterior wall of the first part of the duodenum

may penetrate the wall and erode the relatively large gastroduo-

denal artery, causing a severe hemorrhage.

The gastroduodenal artery is a branch of the hepatic artery, a

branch of the celiac trunk (Fig. 5.4).

Duodenal Recesses

herniae of the intestine were already alluded to on page 163.

Important Duodenal Relations

right kidney have resulted in damage to the duodenum.

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

arterial arcades

superior mesenteric artery

fat

thick wall

plicae circulares

arterial arcades

superior mesenteric artery

ileum

thin wall

Peyer's patch

smooth mucous membrane

jejunum

FIGURE 5.31

Some external and internal differences between the jejunum and the ileum.

Basic Anatomy

pathetic (vagus) nerves from the superior mesenteric plexus.

The nerves are derived from the sympathetic and parasym

enteric artery.

which are situated around the origin of the superior mes

teric nodes and finally reach the superior mesenteric nodes,

The lymph vessels pass through many intermediate mesen

Lymph Drainage

teric vein (Fig. 5.22).

rior mesenteric artery and drain into the superior mesen

The veins correspond to the branches of the supe

Veins

supplied by the ileocolic artery.

form a series of arcades. The lowest part of the ileum is also

tery to reach the gut. They anastomose with one another to

arise from the left side of the artery and run in the mesen

rior mesenteric artery (Fig. 5.32). The intestinal branches

The arterial supply is from branches of the supe

Arteries

from the outside.

ing, these may be visible through the wall of the ileum

along the antimesenteric border (Fig. 5.31). In the liv

present in the mucous membrane of the lower ileum

Aggregations of lymphoid tissue (Peyer’s patches) are

(Fig. 5.31).

out so that it extends from the root to the intestinal wall

ileal end of the mesentery, the fat is deposited through

near the root and is scanty near the intestinal wall. At the

At the jejunal end of the mesentery, the fat is deposited

or even more arcades (Fig. 5.31).

terminal vessels that arise from a series of three or four

the intestinal wall. The ileum receives numerous short

arcades, with long and infrequent branches passing to

The jejunal mesenteric vessels form only one or two

right of the aorta.

whereas the ileal mesentery is attached below and to the

abdominal wall above and to the left of the aorta,

The jejunal mesentery is attached to the posterior

lower part they are absent (Fig. 5.31).

they are smaller and more widely separated and in the

in the jejunum, whereas in the upper part of the ileum

cae circulares, are larger, more numerous, and closely set

permanent infoldings of the mucous membrane, the pli

than the ileum. The jejunal wall feels thicker because the

The jejunum is wider bored, thicker walled, and redder

pelvis (Fig. 5.3).

lon; the ileum is in the lower part of the cavity and in the

neal cavity below the left side of the transverse mesoco

The jejunum lies coiled in the upper part of the perito

179

■

-
-

■

Blood Supply

-
-

Nerve Supply

transverse colon

inferior

pancreaticoduodenal

artery

right colic artery

ileocolic artery

ascending colon

anterior cecal artery

posterior cecal artery

appendix

appendicular artery

ileal arteries

ileum

arterial arcades

jejunal arteries

jejunum

superior mesenteric artery

transverse mesocolon

middle colic artery

FIGURE 5.32

ay down

Superior mesenteric artery and its branches. Note that this artery supplies blood to the gut from halfw

arrow

the second part of the duodenum to the distal third of the transverse colon (