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The Rectus Sheath & Its Contents

Is a fibrous sheath formed by the aponeurosis of

external oblique, internal oblique & transversusabdominis muscles, and it encloses the rectus

abdominis and pyramidalis muscles.

The arrangement of these aponeuroses varies in

different regions of the abdomen;

Above the Costal Margin:

The anterior wall of is formed by aponeurosis of

external oblique.

The posterior wall is formed by 5th, 6th, 7th costal

cartilages and their intercostal spaces.

Betweet the costal margin & the level of

anterior superior iliac spine: The anterior wall is formed aponeurosis of external

oblique & anterior layer of aponeurosis of internal

oblique.

The posterior wall is formed by posterior layer of

aponeurosis of internal oblique and aponeurosis of

transversus abdominis.



Below the Level of Ant. Sup. Iliac Spine (Below Arcuate Line):

The anterior wall is formed by the aponeurosis of external oblique, internal oblique &

transversus abdominis muscles.

The posterior wall is formed by transversalis fascia.

The arcuate line is the site where the posterior layer of aponeurosis of internal oblique

and aponeurosis of transversus abdominis end.

The inferior epigastric artery ascends in rectus sheath behind the middle of arcuate line.

Linea alba is the midline fusion of the aponeuroses of abdominal muscles of both sideanterior to rectus abdominis. It extends between xiphoid process and symphysis pubis and

has the scar of umbilical cord attachment (umbilicus).

Linea semilunaris is the lateral border of rectus abdominis muscle which is obvious when

the muscle contract, and it cuts the tip of 9th costal cartilage where the fundus of gall bladder

is located.

Contents of rectus sheath are:

rectus abdominis & pyramidalis muscles

superior & inferior epigastric vessels

continuation of lower six intercostal nerves

lymphatic vessels



The Inguinal Canal

Intermuscular pathway between abdominal muscles,located in the inguinal region of anterior abdominal wall,

above & parallel to inguinal ligament.

Developmentally created by the descent of testis and its

spermatic cord in the male, and by the round ligament of

uterus in the female.

It is an oblique canal, 4 cm long, located parallel to andabove the inguinal ligament.

It extends between the deep and superficial inguinal

rings.

The deep inguinal ring is a small, oval opening in fascia

transversalis, 1.3 cm above mid-inguinal point. Its

margin gives extension of transversalis fascia along thespermatic cord forming the internal spermatic fascia of

spermatic cord.



The superficial inguinal ring is a larger triangular opening in the aponeurosis of external

oblique just above & medial to pubic tubercle. From the margin of superficial ring, the

aponeurosis of external oblique extends around the spermatic cord as external spermaticfascia. The ilioinguinal nerve emerges through the superficial ring.

The inguinal canal contains spermatic cord in male, round ligament of uterus in female,

and the ilioinguinal nerve in both sexes.

It is important clinically for being the site of indirect inguinal hernias.

The Walls of Inguinal Canal

The anterior wall: is formed by external oblique aponeurosis and anterior fibers of

internal oblique.

The posterior wall: is formed by the fascia transversalis laterally and conjoint tendon

medially. The conjoint tendon is formed by the arching fibers of

internal oblique and tranversus abdominis.

The roof or superior wall: is formed by arching fibers of internal oblique and


The floor or inferior wall: is formed by inguinal ligament.



The Spermatic Cord

It conveys structures between the testis and abdominal cavity. Its covered by three layers;

the inner layer is internal spermatic fascia derived

from fascia transversalis.

The middle layer is cremasteric muscles and fascia

derived mainly from internal oblique & partly by


The outer layer is external spermatic fascia derived

from external oblique aponeurosis.

Its contents are:

Vas deferens

Testicular artery

Pampiniform plexus & testicular vein

Lymphatic vessels & autonomic nerves

Artery of vas deferens from inferior vesicle artery

Cremasteric artery (branch of inferior epigastric artery)

Genital branch of genitofemoral nerve which supplies cremasteric muscles

Remnant of processus vaginalis



The Scrotum

A pendulous sac lodging the testes.

Divided into right & left halves by median

thick fibrous septum.

Its covering from outward and inward are:

skin, which is thick, hairy and dark colored

superficial layer of superficial fascia called

dartos fascia containing smooth musclesfibers (dartos muscles)

membranous layer of superficial fascia called Colle¶s fascia which is continuous

with that of anterior abdominal wall.

External spermatic fascia

Cremasteric muscles & fascia Internal spermatic fascia

Tunica vaginalis ( parietal layer, cavity & visceral layer) covering the anterior, medial

& lateral surfaces of testis

It protects the testis & maintains optimum temperature for normal spermatogenesis.



The Descent of Testis

The testis develops with the kidneys in abdominal cavity on the posterior abdominal wall

behind the peritoneum. The descent of testis begins at the 7th month of pregnancy and completed just before birth.

The descent of testis is stimulated by fetal testosterone and it

is guided by a cord of mesenchymal tissue called

gubernaculum attached to the lower pole of testis.

A fold of peritoneum (processus vaginalis) also starts to

descend anterior to the testis and gabernaculum.

The testis, gabernaculum and fold of peritoneum emerges

through the deep inguinal ring of fascia transversalis, passing

between the muscles of abdomen forming the inguinal canal.

To find their way down to scrotum, the testis and the

accompanying structures emerge through superficial inguinal

ring of external oblique aponeurosis and finally reach thescrotum.

The gabernaculum will degenerates and disappear,.

The fold of peritoneum will form tunica vaginalis

(a peritoneal sac) around the testis, which either lose its

connection with abdominal peritoneum or will be connected

with it a fibrous process called processus vaginalis.



Important Clinical Notes on Anterior Abdominal Wall

The most frequent clinical cases affecting the anterior abdominal wall

are hernia.

Hernia is a protrusion of a peritoneal sac with or without abdominal

viscera (mainly intestines) through a natural defect or acquired

weakness in anterior abdominal wall.

Types of abdominal wall hernias include:

1) Inguinal hernias (direct or indirect):

The indirect hernia occurs through a weakened & enlarged deep inguinal ring passinginto the scrotum through the inguinal canal. It is usually congenital

The direct hernia usually occurs in the Hasselbach triangle of anterior abdominal wall

(bounded by midline, inguinal ligament & inferior epigastric artery)

2) Femoral hernia: occurs mainly in females through the weakened femoral ring, in front of

thigh just below inguinal ligament .

3) Diaphragmatic hernia: Congenital hernia of Morgagni usually occurs through the

sternal origin of diaphragm, while congenital hernia of Bockdalek

occurs through a patent left pleuroperitoneal canal.

Acquired hiatus hernia usually occurs in females through

weakened esophageal hiatus of diaphragm.



4) Epigastric hernia: occurs in adult through small aperture in the linea alba above the

umbilicus. It is usually painful and mimics peptic ulcer.

5) Umbilical hernias:The congenital type usually appears in infant while the acquired type occurs in adult and

called paraumbilical hernia.

6) Hernia of lumbar triangle (hernia of Petit triangle): it is rare and occurs

posteriorly in the Petit triangle bounded by free posterior border of external oblique, iliac

crest and latissmus dorsi muscle.

7) Acquired incisional hernias: are complications of improper

or large abdominal incisions used in surgery.

Omphalocele minor & major: it is due to failure of development

of anterior abdominal wall, and the viscera are exposed and covered

by moist peritoneum.

Patent urachus: is a congenital anomaly in which the urachus

between the apex of urinary bladder and umbilicus remains patent

thus, urine will escape out of umbilicus when the bladder is full of urine.



Common Clinical Notes on Scrotum & Spermatic Cord:

1) Hydrocele: is a collection of fluid in the cavity of tunica

vaginalis around the testis. It is commonly congenital due persistent connection of processus vaginalis, whilev the

acquired is usually due to infections of testis & its coverings.

2) Improper Descent of Testis: it could be;

Completely undescent of testis (Cryptorchidism): the testis remains in the peritoneal cavity

and degenerates leading to malignancy if not removed.

Incomplete descent of testis: the descent of testis is arrested any where in the inguinal canal.

Maldescent of testis: the testis is not in the scrotum and usually migrated into places

different from its proper pathway such as root of penis, perineum or thigh.

Retractile testis: the testis is not fixed in the scrotum, it goes up & down and requires

surgical fication.

3) Varicocele: is abnormal dilation (varicosity) of theveins of pampiniform plexus of testis & spermatic cord.

It is more common in left side. and if bilateral & not

treated, it leads to sterility.

4) Torsion of testis: the testis rotates around its vertical axis either

anteriorly or posteriorly according to direction of trauma. It occlude the blood vessels and should

be treated within 6-8 hours to prevent atrophy of testis.



The Peritoneum

Serous sac lining the abdominal wall & inferior surface of diaphragm. It extends to invest

abdominopelvic viscera. It consists of outer parietal layer, peritoneal cavity containing serous peritoneal fluid,

and inner visceral layer.

It is like a large balloon invaginated inward by the abdominopelvic viscera.

The visceral layer is a continuation of parietal layer

and extends as mesentery or ligaments consisting

of two layers of parietal peritoneum separated by

loose connective tissue containing blood vessels,

lymph nodes & lymph vessels, and autonomic nerves.

The two layers of the mesentery or ligament on

reaching the viscera, they invest the organ. In this

way, the blood, lymphatic vessels & nerves reach

the organs.

No organs has a complete peritoneal covering.



An intraperitoneal organ is covered by the visceral peritoneum from all its sides except the

area where the two layers of peritoneum diverge around it (abdominal esophagus, stomach,

1st

2.5 cm of duodenum, jejunum, ileum, cecum, appendix, transverse & sigmoid colon, liver & spleen).

An extra or retroperitoneal organ is covered by peritoneum only on its anterior surfaces

and its sides.

The peritoneal cavity contains only fluid and divided into the greater and lesser sacs

communicated with each other by the epiploic foramen or aditus of lesser sac located

below the free border of lesser omentum of stomach.

The greater sac is the largest part of peritoneal cavity extending into the pelvic cavity and

divided by the transverse mesocolon into supracolic & infracolic parts.

The lesser sac lies behind the stomach and in the greater omentum of stomach.

The epiploic foramen is bounded by:

Anteriorly: by the free border of lesser omentum

containing portal vein, hepatic artery & bile duct.

Posteriorly: by inferior vena cava.

Superiorly: by caudate process of liver.

Inferiorly: by 1st part of duodenum.



Peritoneal Omenta:

Are two folds of peritoneum, the greater & leseer omentum, attached to borders of stomach.

The greater omentum is 4 folds of peritoneum containing the inferior recess of lesser sac

and attached to greater curvature of stomach. Its lower border is free and reaches pelvic

cavity. Its posterior layer is fused with the anterior layer of transverse mesocolon, and its

upper part extends between the fundus of stomach and the hilum of spleen as gastrosplenic

ligament which continues from spleen to left kidney as splenorenal ligament.

The lesser omentum is double layer of peritoneum extending from the lesser curvature of stomach and upper border of first 2.5 cm of duodenum to the porta hepatis and fissure for

ligamentum venosum of the liver.



Peritoneal Ligaments

Are extension of double layers of peritoneum from parietal peritoneum to abdominal viscera

which include;

Falciform ligament of liver which extends from

parietal peritoneum of anterior abdominal wall above

umbilicus and from parietal peritoneum of inferior surface

of diaphragm to the anterior superior surface of liver. It

has the ligamentum teres (obliterated left umbilical vein)

in its free posterior border.

The right coronary ligament, right & left triangular ligaments of liver are peritoneal

ligaments reflected from upper posterior surface of liver to peritoneum on the inferior

surface of diaphragm. They suspend the liver in position.

Gastrosplenic & splenorenal ligaments.



Peritoneal Folds & Recesses

Folds of peritoneum can be produced by the underlying

structures or vessels, such as:

Median umbilical fold: formed by the obliterated urachus

between the apex of urinary bladder & umbilicus.

Medial umbilical fold: formed by the obliterated umbilical

artery.

Lateral umbilical fold: formed by the inferior epigastric artery.

Peritoneal folds can be also extensions of peritoneum

between viscera of abdominal cavity which leads to formation

of recesses of peritoneal cavity around them.

These recesses are sites for formation of internal hernias, and include:

Recesses at the duodeno-jejunal junction: include, superior

duodenal , inferior duodenal, paraduodenal & retroduodenal recesses.

Recesses around ileocecal junction are: superior ileocecal, inferior

ileocecal & retrocecal recesses.

Intersigmoid recess is present at the apex of sigmoid mesocolon

anterior to the left ureter.



Peritoneal Gutter & Pouches

Peritoneal gutters are large spaces of peritoneal cavity located on either sides of ascending

& descending colon.

Peritoneal pouches are spaces of peritoneal cavity located between the pelvic viscera and are

occupied by coils of small intestine. These pouches are:

In male is the rectovesicle pouch between the rectum & urinary bladder.

In female; the uterovesicle pouch lies between the urinary bladder & uterus, while the

rectovaginal pouch or Douglass pouch lies between the rectum and vagina and its has

important clinical implications.



Nerve Supply of Peritoneum

The parietal peritoneum is sensitive to general sensations.

The parietal peritoneum of abdominal cavity is supplied with anterior abdominal by the lower

six thoracic nerves and the ilio-hypogastric & ilio-inguinal nerves of 1st lumbar nerve.

The parietal peritoneum of pelvic cavity is supplied by the obturator nerve of lumbar plexus.

The visceral peritoneum is sensitive only to stretch and tear and it is supplied by autonomic

nerves of related viscera.

Blood Supply & Lymph Drainage of Peritoneum

The parietal peritoneum is supplied by vessels od anterior abdominal & pelvic wall, while the

visceral peritoneum is supplied by vessels of related viscera.

The lymph drainage of parietal follows that of abdominopelvic wall, while that of visceral

peritoneum follows that of related viscera.



The Stomach

Intraperitoneal muscular sac located in the epigastric, left hypochondrial and umbilical regionsof the abdomen, and extends between the cardiac and pyloric orifices or openings.

The cardiac opening is the junction between esophagus & stomach, while pyloric opening

is the junction between the stomach and duodenum.

It is J-shaped when empty, freely mobile except at its fixed cardiac and pyloric ends.

Its functions are:

Storage, digestion & mixing of food stuffs as chyme.

Secretion of mucus to protect its own mucosa.

Secretion of HCl, gastric lipase and pepsin.

Secretion of vitamin B12 intrinsic factor.

Secretion of hormones mainly gastrin, somatostatinand serotonin.

Controls the delivery of chyme into duodenum.

It has two borders (lesser & greater curvatures attaching to them lesser & greater omenta,

respectively), two surfaces (anterior & posterior), and two openings (cardiac & pyloric).



The inner surface of stomach, the mucus membrane, is thrown into longitudinal folds called

rugae. These rugae are not present in the mucus membrane of stomach opposite the lesser

curvature forming a pathway called gastric canal for rapid transport of fluid.

it is descriptively is divided into; cardia, fundus, body, pyloric antrum, pyloric canal &

pyloric sphincter.

The cardia is the area surrounding cardiac orifice,

The fundus is the part above and to the left of cardiac orifice

The body extends from cardiac orifice to incisura

angularis, a small depression in lower part of lesser

border of stomach .

The pyloric antrum is the distended part of pylorus

after incisura angularis.

The pyloric canal is tubular part of pylorus and hasthickening of circular smooth muscles forming the

pyloric sphincter.



Relations of Stomach

Anteriorly:

Anterior abdominal wall, left lobe of liver, left dome of diaphragm separating the stomach

from left pleura, base of left lung & pericardium.

Posteriorly:

The stomach bed formed by lesser sac, pancreas, splenic vessels, transverse colon & mesocolon,

left suprarenal gland, upper pole of left kidney, spleen & the diaphragm.



Blood Supply of StomachAreteries:

They anastamose freely with each other in the wall

of stomach and include;

Left gastric artery: arises from celiac trunk of

abdominal aorta: runs in the upper part of lesser

omentum

Right gastric artery: arises from the common

hepatic artery of celiac trunk & runs in the lower

part of lesser omentum

Left gastro-epiploic artery: arises from the splenic

artery at the hilum of spleen and runs in the upper

part of greater omentum through gastrosplenic

ligament.

Right gastro-epiploic artery: arises from the gastroduodenal artery of common hepatic

artery and runs in the lower part of greater omentum.

Short gastric arteries: arises from splenic artery at the hilum of spleen and supplied the

fundus.



Veins:

Left gastric vein: drains into the portal vein

Right gastric vein: drains into portal vein

Left gastroepiploic vein: drains into superior

mesenteric vein

Right gastroepiploic vein: drains into splenic

vein

Short gastric veins: drains into splenic vein

Lymph Drainage of Stomach The lymph vessels of stomach run alongside its

blood vessels to the left gastric, right gastric, left

gastroepiploic, and right gastroepiploic groups

of lymph nodes located in the roots of lesser &

greater omenta.

Lymphatic vessels from these nodes run into the

celiac lymph nodes (anterior aortic nodes).

Nerve Supply of Stomach Parasympathetic nerves from the anterior & posterior vagal trunks.

Sympathetic nerves from the greater splanchnic nerves of sympathetic trunk via the celiac plexus.



Histology of StomachThe histological layers of the wall of stomach from inside out are:

1) The Mucosa:

The main layer consisting of epithelium, lamina propria,

and muscularis mucosae. It is thrown into longitudinal folds

(gastric rugae), which disappear when the stomach is fully

distended.

On the mucosal surface there are small, funnel-shaped

depressions called gastric pits.

The entire mucosa is occupied by simple, branched tubular

gastric glands which open into the bottom of the gastric pits.

Each gastric gland has isthmus, neck & base.

The surface epithelium in whole stomach is simple, tall

columnar and contains surface mucous cells The mucus is alkaline and adheres to the epithelium. It forms an ~ 1 mm thick

layer which protects the mucosa from acidic content of stomach.



The mucus cells of surface epithelium are renewed approximately every 3-4 days. The source

of the new cells is from the stem cells of isthmus (the upper part of the neck of the gastric

glands), where cells divide and then migrate upwards to surface epithelium and differentiate

into mature epithelial cells.

In contrast to the surface epithelium, cellular composition and function of the gastric glands

are specialized in the different parts of the stomach.

Cardiac glands Are heavily branched tubular glands with coiled ends, and are similar to the cardiac glands

of esophagus.

They contain mainly mucus-producing cells which produce mucus & lysozymes..

A few parietal cells are also present.



Principal Glands (Glands of Fundus & Body)

Each glandular tubule is placed perpendicular to the surface of the epithelium and consists

of three parts: deep body, middle neck and upper isthmus.

Five cell types are seen in the glands of fundus & body, which are: stem cells, chief cells

(zympgen or pepsinogen cells), parietal cells, mucous neck cells and endocrine cells.

1) Stem cells:

Are low columnar cells with oval basal nuclei, and

located in the isthmus and neck of gastric glands.

They are highly mitotic, divide and differentiate

into all types of mucosal cells.

2) Mucous neck cells:

They are found between the parietal cells in the neck

of the gland. They are difficult to distinguish from chief cells in plain

H&E stained section.



.

3) Parietal cells (oxyntic cells):

They are frequently present in the neck of the glands

and are reach the lumen of the gland, while in thelower parts of gland, they are situated between chief

cells.

Their characteristic features when active are the

presence of numerous cell membrane invaginations

forming intracellular caniliculi with abundant

mitochondria.

They secret hydrochloric acid which activate the

pepsinogen and also sterilizes the contents of

stomach.

The parietal cells also secret intrinsic factor necessary

for the absorption of vitamin B12. Destruction of the

gastric mucosa by e.g. autoimmune gastritis or theresection of large parts of the lower ileum result in

pernicious anemia.

Only one type of bacteria, the Helicobacter pylori

has found to live in the stomach but, unfortunately

these bacteria are involved in the pathogenesis of gastritis, gastric ulcers & cancers.



4) Chief cells (zymogen cells):

They are the most numerous of the four types, present primarily in the body of the glands.

they are protein synthesizing cells so they are rich in rER, Golgi apparatus, and zymogen

granules.

They produce pepsinogen, which is a precursor of the proteolytic enzyme pepsin.



5) Endocrine cells:

Endocrine cells are scattered throughout theepithelium of the gastrointestinal tract.

They are part of the gastro-entero-pancreatic

(GEP) endocrine system.

The most frequent endocrine cells in the gastric

mucosa are gastrin-producing cells (G cells)

and somatostatin-producing cells (D cells).

G cells are found mainly in glands of pyloric antrum.

Their gastrin hormone stimulates the secretion of acid

& pepsinogen and contraction of muscles. They are

stimulated by cholinergic nerves, distension of the

stomach & intestinal hormones.

D cells produce somatostatin which inhibit G cells function. They arestimulated by acid in the lumen of the stomach and duodenum.

Other types of endocrine cells include, VIP-producing cells (or D1 cells; vasoactive

intestinal peptide) and serotonin-containing cells (enterochromaffin cells). These

cells are alternatively named APUD-cells: amine precursor uptake and decarboxylation cells.



Pyloric glands

They have deeper pits more coiled than principal glands and may be branched.

They secrets mucus and lyzozymes.

Endocrine cells, in particular gastrin-producing cells, are more frequent than in principal

glands. A few parietal cells may be present but chief cells are usually absent.



2) Submucosa:

It lies under the mucosa and consists of fibrous connective tissue.

It contains the Meissner's plexuses.

3) Muscularis externa:

It consists of three layers of smooth muscle; inner oblique layer, middle circular layer

& outer longitudinal.

The circular smooth muscles layer of the pylorus is thick and forms the pyloric

sphincter, which controls the movement of chyme into the duodenum.

The Auerbach's plexus lies in this layer.

4) Serosa:It consists of of connective tissue covered by mesothelium (visceral peritoneum).



The Small Intestine

~ 6-7 m long, located in the center of abdominal cavity.

Begins at the pyloric orifice of stomach and ends in the cecum at at ilieocecal junction.

Consists of duodenum (25 cm), jejunum (2.5 m), and ileum (3.5 m).

It functions in the digestion and absorption of food stuff, and in the secretion of enzymes

and hormones.



Duodenum

C-shaped, 25 cm long, begins at the pyloric endof stomach (1st lumbar vertebra), curves around

the head & body of pancreas and ends at the

duodenojejunal junction (2nd lumbar vertebra).

Descriptively divided into 4 parts; 1st, 2nd, 3rd & 4th.

Only its first 2.5 cm is intraperitoneal.

It supplied by the superior pancreaticoduodenal artery

from gastroduodenal branch of common hepatic artery

of celiac trunk, and the inferior pancreatic artery from

superior mesenteric artery.

Its venous drainage is by the superior and inferior pancreaticoduodenal veins (the superior is a

tributary of portal vein, while the inferior is a tributary of superior mesenteric vein).

Its nerve supply is by the branches of celiac & inferior mesenteric plexuses.

Its lymph is drained into the celiac and superior mesenteric lymph nodes.



First Part:

5 cm long, and only half of it is covered by peritoneum.

Begins from the pyloric end of stomach and ends behind the neck of gall bladder .

Its relations are:

Anteriorly: to quadrate lobe of liver & gall bladder.

Posteriorly: to lesser sac, gastro-duodenal artery, bile duct, portal vein & inferior

vena cava.

Superiorly: to epiploic foramen.

aInferiorly: to the head of pancreas.



Second Part:

8 cm long, descends on the right side of 2nd & 3rd lumbar vertebrae anterior to the hilum of

right kidney.

Its relations are:

Anteriorly: to gall bladder fundus, liver & transverse colon.

Posteriorly to hilum of right kidney.

Laterally: to ascending colon & liver.

Medially: to the head of pancreas and the bile & pancreatic ducts.

The bile & the main pancreatic duct join together just before piercing duodenal wall (at the

middle of 2nd part of duodenum) forming the hepatopancreatic duct. Within the duodenal

wall, the hepatopancreatic duct swells forming ampula of Vater and open in separate

openings on the summit of major duodenal papilla. The smooth muscles in the wall of

ampulla of Vater are thickened forming sphincter of Oddi.

The minor pancreatic duct if present, it extends above the major pancreatic duct and opens in the minor duodenal papilla 2 cm

above the major papilla.



Third Part:

8 cm long, runs horizontally from the right side to the left across the 3rd lumbar vertebra and

the inferior vena cava & aorta to join the 4th part.

Its relations are:

Superiorly: the head & body of pancreas.

Inferiorly: the coils of jejunum.

Anteriorly: the root of the mesentery of small intestine

containing the superior mesenteric artery

& vein.

Posteriorly: to the right ureter, right psoas major muscle,

inferior vena cava & aorta.

Fourth Part:

5 cm long, ascends to the left and joins the jejunum at the duodeno-jejunal flexure. The dudeno-jejunal flexure is suspended to the right crus of diaphragm by the ligament of

Treitz.

Its relations are:

Anteriorly: it is related to the root of small intestine mesentery & coils of jejunum.

Posteriorly: it is related to left margin of aorta and medial part of left psoas major muscle.



The Jejunum & Ileum

~ 6-7 m long, covered by visceral peritoneum extended from the mesentery of jejunum &ileum (mesentery of small intestine).

The root of small intestine mesentery is 15 cm long and extends from the left side of 2nd

lumbar vertebra to the right sacroiliac joint. It is attached on the posterior abdominal wall

and crosses anterior to abdominal aorta, infeior vena cava, right psoas major, right ureter and

right gonadal vessels. It contains the superior mesenteric vessels and the lymph nodes,

lymphatic vessels and nerves of jejunum, ileum.

Their blood supply is by the branches of superior

mesenteric vessels.

Their lymph is drained into superior mesenteric lymph nodes.

Their nerve supply is from superior mesenteric autonomic

plexus.



Gross Anatomical Differences between Jejunum & Ileum

The coils of jejunun occupy the upper left part of abdominal cavity while coils of ileum are

in the lower right part and in pelvis.

The mesentery of jejunum lies above and to the left of abdominal aorta, while that of ilieum

is below and to the right of abdominal aorta.

The jejunum is larger in diameter, has thicker wall and more vascular.

The circular folds of mucosa of jejunum (plica circulares) are more numerous.

The arterial arcades of mesentery of jejunum are fewer.

The stored fat in the mesentery of ileum is much more than that of jejunum.

The Peyer¶s patches are more numerous in the wall of ileum.



Histology of Small Intestine:

The wall of small intestine consists of mucosa, submucosa, muscularis and serosa or adventitia.

The three parts of small intestine share in many common features which are described together,and the differences are pointed for each part.

Grossly by naked eye, the inner surface of small intestine is thrown into semi-lunar folds called

plica circulares or Kerckring¶s valves. They are made of mucosa and submucosa and increase

the surface area.

The plica circulares are numerous and characteristic feature of jejunum and few in duodenum and

ileum.



1) The mucosa or mucus membrane:

Consists of epithelium (simple tall columnar), lamina

propria & muscularis mucosae. The lamina propria

contains lymphatic aggregation which together with

those present in submucosa forms the Peyer¶s patches.

The Peyers patches much numerous in the ileum.

Microscopically, the mucus membrane is thrown

into numerous finger like projections called

intestinal villi to increase the surface area of absorption.

Cells lining lower part of villi form simple tubular

intestinal gland (glands or crypts of Lieberkühn).

In the duodenum, the intestinal glands are continuous

with another submucosal, coiled-tubular mucus glands

called Brunner¶s glands, which secret alkaline mucus.

Each villus is 0.5-1.5 mm long, lined by epithelium

and has a core of lamina propria, smooth muscle fibers,

blood vessels, lymphatic vessels and nerves.



The epithelial cells lining the villi are principally absorptive tall columnar cells (enterocytes)

with few intervening goblet cells. The absorptive cell has the following features:

The cell membrane of absorptive cells has largenumber of microvilli which give the appearance

of brush border under LM.

Each microvillus is 1µm long & 0.5µm wide, and

it increases the surface area of absorption (~3000

villi per epithelial cell).

Their cell membrane has peptidases and disaccharidaseswhich help in the conversion of dipeptides and disaccharides

into amino acids & simple sugars which are then absorbed by

active transport.

The absorption of fat products (monoglycerides & fatty acids) after being digested by bile &

pancreatic lipase is by passive transport across the cell membrane.

Each microvillous has a core of cytoskeleton

made of actin & fibrin filaments associated

with villin (a villous cap protein).



Types of Cells of Intestinal Glands

They include; stem cells, few absorptive cells, goblet cells, Paneth¶s & neuroendocrine cells.

1) Absorptive Cells: already described.

2) Goblet Cells: have clear well-known features.

3) Stem Cells: scattered among other cells and recognized with special markers.

4) Paneth¶s Cells: serous cells secret lysozymes for destruction of bacteria within the intestinal

lumen. They are demonstrated by special immunostaining methods.



5) M Cells (Microfold Cells):

They are specialized epithelial cell present over

the lymphatic follicles (Peyer¶s patches).

They have many basal enfolding and pits lodging

macrophages, lymphocytes and plasma cells.

Play an important role in intestinal immunity

as they transport antigens from intestinal lumen

to underlying macrophages & lymphocytes.

6) Neuroendocrine Cells:

They are several types and are illustrated in the table.

They care clearly demonstrated clearly by special

immunostaining techniques, and are essential in

the normal physiology of digestion and absorption.

They exist in two forms; closed type which does not

reach the surface, and the open type which reach the

surface.

The open type probably act as chemoreceptors to

record the nutrients content & pH in intestinal

lumen.



Cell Type & Location Hormone produced Major Action

S-cells (small intestine) Secretin Stimulates secretion of bile andpancreatic juice.

K-cells (small intestine) Gastric inhibitory polypeptide Inhibits gastric secretion.Stimulates insulin secretion.

L-cells (small intestine) Glucagon-like peptide Inhibits gastric secretion.

Stimulates insulin secretion.I-cells (small intestine) Cholecystokinin Stimulates pancreatic secretion.

Stimulates gall bladdercontraction.

D- cells (stomach & smallintestine)

Somatostatin Inhibits exocrine & endocrinesecretion.Inhibits neurotransmitter release.

Mo-cells (small intestin) Motilin Increases gut motility

EC cells (small intestine) Serotonin & Substance P Increases gut motility

D1-cells (GIT) VIP (vasoactive intestinalpolypeptide)

Increases water & ions secretion.Increase gut motility.

Intestinal Hormones



2) The submucosa:

It consists of fibrous tissue and contains Meissner¶s plexus which supplies muscularis

mucosae.

In the duodenum, it contains Brunner¶s glands (mucus, coiled tubular).

In the ileum, it has many Peyer¶s patches.

3) Muscularis: It consists of inner circular and outer longitudinal layers, lying in between,

is the Auerbach¶s plexuses.

4) Serosa or Fibrosa: It consists of dense fibrous tissue and mesothelium.



The Arteries of GIT

The GIT is supplied by three single branches of

abdominal aorta; celiac superior mesenteric &inferior mesenteric arteries.

1) Celiac artery: arises immediately below the

aortic hiatus of diaphragm anterior to 1st lumbar

vertebra. It divides into; left gastric, splenic &

common hepatic arteries.

The left gastric artery supplies the stomach and

lower part of esophagus.

The splenic artery runs behind the stomach and

pancreas to reach the hilum of spleen . It gives right

gastro-epiploic artery, short gastric arteries, pancreatic branches, and splenic

branches.

The common hepatic artery runs in the lesser omentum toward the porta hepatis. It becomes

the proper hepatic artery after giving the right gastric, gastroduodenal & supraduodenal

arteries. The gastroduodenal artery divides into the right gastro-epiploic and superior

pancreatico-duodenal arteries.

In the porta hepatis, the proper hepatic artery divides into right and left hepatic arteries

which supplies the lobes of liver. The right hepatic artery gives the cystic artery to gall

bladder.



2) Superior mesenteric artery:

It arises 0.5 cm below the celiac artery, enters the

root of the mesentery of small intestine and

accompanied by the superior mesenteric vein.

It continues in the mesentery anterior to 3rd part of

duodenum, and gives the following branches:

i) inferior pancreatico-duodenal artery

ii) right colic artery

iii) middle colic arteryiv) ileocecal artery artery which gives anterior and

posterior cecal branches. The posterior cecal

artery gives the appendicular artery to appendix.

v) ileocolic artery

vi) jejunal & ileal branches

3) Inferior mesenteric artery:It rises at the level of 3rd lumbar vertebra and gives

the following branches:

i) left colic artery

ii) two sigmoidal arteries

iii) superior rectal artery



The Veins of GIT

The venous drainage of GIT is through the portal venous system which is illustrated in the

diagram below.

git lectures(1) dr.adeeb-1

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