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University of Sulaimani

College of Pharmacy

Anatomy

Lectures of the Abdomen

Second Stage

2019-2020

DR.Shaxawan Ali

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The Abdomen:

The abdomen is the region of the body that l ies between the thorax above and

the pelvis below.

Structure of the Anterior Abdominal Wall :

The anterior abdominal wall consists of (Fig. 1):

1) Skin .

2) Superficial fascia.

3) Deep fascia.

4) Muscles .

5) Fascia transversalis .

6) Extraperitoneal fat .

7) Parietal peritoneum .

Figure (1): Structure of the anterior abdominal muscles.

Superficial fascia

(fatty layer)

Superficial fascia

(membranous layer) Skin

Rectus muscle

Extraperitoneal fat

Parietal peritoneum

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Muscles of the Anterior Abdominal Wall :

1) 3 broad thin sheets of muscles: the external oblique , internal oblique ,

and transversus abdominis .

2) A vert ical muscle: the rectus abdominis (Fig. 2).

Figure (2): Muscles of anterior abdominal wall.

Functions of the Anterior Abdominal Wall Muscles

1) Laterally f lex the trunk.

2) Support the abdominal viscera.

3) Assist the diaphragm during inspirat ion.

4) Assist in the act of forced expirat ion during coughing & sneezing.

5) Help in micturit ion, defecation, vomit ing, and labor by increasing the intra-

abdominal pressure.

Inguinal ligament

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Structure of the Posterior Abdominal Wall :

The posterior abdominal wall is formed, in the midline, by the f ive lumbar

vertebrae, and laterally, by the 12th r ibs, the bony pelvis , the psoas muscles, &

quadratus lumborum muscles (Fig. 3).

Figure (3): Structure of the posterior abdominal wall.

Abdominal regions:

For clinical purposes, the abdomen is divided into many regions by v ert ical l ines

and horizontal planes (Fig. 4).

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Figure (4): Regions of the abdomen.

Peritoneum:

The peritoneum is a serous membrane that l ines the walls of the abdominal and

pelvic cavit ies and covers the viscera. The parietal peritoneum l ines the walls

of the abdomen and pelvis, and the visceral peritoneum covers the organs. The

space between the parietal and visceral layers is cal led the peritoneal cavity

(Fig. 5). The space contains a f luid, the peritoneal fluid , which al lows free

movement between the viscera.

Iliac

Iliac (Suprapubic)

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Figure (5): The peritoneum.

Intraperitoneal and Retroperitoneal Organs:

Intraperitoneal organs: are organs that are almost completely covered with

visceral peritoneum, e.g. stomach, jejunum, i leum, and spleen.

Retroperitoneal organs: are organs that are only part ially covered with visceral

peritoneum and l ie behind the peritoneum, e.g. pancreas, k idney, ascending

colon and descending colon.

duodenum

Peritoneal cavity

Parietal peritoneum

Visceral peritoneum

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The Abdominal Cavity:

Omentum: is a fold of peritoneum that connects the stomach to another

organ, e.g., greater omentum & lesser omentum (Figs. 6 & 10).

Mesenteries: are folds of peritoneum that connect the intest ines to the

posterior abdominal wal l, e.g., the mesentery of the small intestine (Fig. 7).

Figure (6): The greater & lesser omenta.

Gastrointestinal Tract:

Esophagus:

The esophagus is a muscular tube about 25 cm long that joins the pharynx to

the stomach. The greater part of the esophagus l ies within the thorax. It enters

the abdomen through the esophageal opening in the diaphragm. I t joins the

stomach at the gastro-esophageal junction (Fig. 8) which is a physiological

sphincter rather than an anatomic sphincter.

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Figure (7): The mesentery & the transverse mesocolon.

Stomach: (Figs. 8 & 9)

The stomach is the dilated part of the gastrointest inal tract. I t is situated in the

upper part of the abdomen, occupying the epigastr ic and umbilical regions.

The stomach has two openings, the cardiac and pyloric orifices; two

curvatures, the greater and lesser curvatures; and two surfaces, anterior and

posterior surfaces.

The stomach is divided into:

Fundus .

Body.

Antrum.

Pylorus .

The mucous membrane of the stomach is thick and is thrown into folds. The

muscular wall contains longitudinal, circular and oblique f ibers. The

peritoneum completely covers the stomach.

Transverse

mesocolon

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Figure (8): General arrangement of abdominal viscera.

Functions:

1) Stores food ( in the adult it has a capacity of about 1500 mL)

2) Mixes the food with gastr ic secret ions

3) Controls the rate of delivery of food to the small intest ine.

Arterial Supply: (Fig. 9-B)

1) Left gastr ic artery.

2) Right gastr ic artery.

3) Left gastroepiploic artery.

4) Right gastroepiploic artery.

5) Short gastr ic arteries.

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Figure (9): (A) The stomach, (B) Arteries of stomach

(A)

(B)

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Small intestine:

The small intest ine is the longest part of the alimentary tract that extends from

the stomach to the i leocecal junction. The greater part of digestion and

absorption takes place in the small intestine.

It is divided into three parts: the duodenum, the jejunum, and the i leum.

Duodenum:

This is situated in the epigastr ic and umbilical regions. I t is about 25 cm long

that extends from the stomach to the jejunum (Fig. 8). It receives the bile & the

pancreatic ducts at a small elevation called major duodenal papilla (Fig. 10).

The f irst 2.5 cm of the duodenum is covered with peritoneum. The remainder of

the duodenum is retroperitoneal.

The mucous membrane of the duodenum is thick. In the f irst part it is smooth;

in the remainder of the duodenum it is thrown into numerous folds called the

plicae circulars (Fig. 10).

Figure (10): The duodenum.

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Jejunum and Ileum: (Figs. 7, 8 & 11)

The jejunum and i leum together measure about 6 m long; the upper two f if ths of

this length makes up the jejunum. The jejunum begins at the duodenojejunal

junction, and the i leum ends at the i leocecal junction.

The coils of jejunum and i leum are freely mobile and are attached to the

posterior abdominal wal l by the mesentery of the small intestine.

Figure (11): The small intestine and large intestine.

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Differences between jejunum and ileum: (Fig. 12)

1) The jejunum lies in the upper part of the peritoneal cavity; the i leum is in

the lower part of the cavity.

2) The jejunum is wider, thicker walled, and redder than the i leum.

3) The jejunal vessels form only one or two arcades. The i le al vessels f rom a

series of three or four or even more arcades.

4) Aggregations of lymphoid t issue (Peyer's patches) are present in the

mucous membrane of the lower part of i leum which is absent in the

jejunum.

5) Mesentry of jejunum lies above & to the left of aorta, while mesentry of

i leum lies below and to the r ight of aorta

Figure (12): Some dif ferences between jejunum and i leum:

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Large Intestine:

The primary function of the large intest ine is the absorption of water and

electrolytes and the storage of undigested material to be excreted as feces.

I t is divided into the cecum, appendix, ascending colon, transverse colon,

descending colon, sigmoid colon, rectum, and anal canal.

Cecum:

The cecum lies in the r ight i l iac fossa. I t is about 6 cm long and is completely

covered with peritoneum. As in the co lon, the longitudinal muscle forms 3 bands,

the teniae coli .

The i leum enters the large intest ine at the junction of the cecum with the

ascending colon, called the i leocecal junction (Figs. 8 & 11).

Appendix:

This is a worm-shaped tube (about 8-13 cm long) containing a large amount of

lymphoid t issue that l ies in the r ight i l iac fossa. It is attached to the

posteromedial surface of the cecum (Figs. 8 & 11).

Differences between the Small and Large Intestine: (Fig. 13)

External Differences:

1) The small intest ine is mobile, whereas the large intest ine is more f ixed

2) The diameter of the small intest ine is smaller than the large intest ine.

3) Teniae coli are present in large intest ine & absent in the small intest ine.

4) The wall of the small intest ine is smooth, whereas that of the large

intest ine is sacculated.

5) Large intest ine has fatty tags (appendices epiploicae), which are absent

in small intest ine.

Internal Differences:

1) The mucous membrane of the small intest ine has vil l i & folds, which are

absent in the large intest ine.

2) Aggregations of lymphoid t issue are found in the small intestine which are

absent in the large intest ine.

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Figure (13): Some differences between small & large intestine.

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Blood Vessels of Abdomen:

Abdominal aorta:

The aorta enters the abdomen through the diaphragm at the level of T12. It ends

by dividing into 2 common il iac arteries at the level of L4 (Fig. 14).

Branches: (Fig. 14)

1) 3 anterior branches: celiac artery, superior mesenteric artery, and

inferior mesenteric artery.

2) 3 lateral visceral branches: suprarenal artery, renal artery, and

test icular (or ovarian) artery.

3) 5 lateral parietal branches: inferior phrenic artery & 4 lumbar arteries.

Inferior Vena Cava:

The inferior vena cava conveys most of the blood from the body below the

diaphragm to the r ight atr ium. I t is formed by the union of the common il iac

veins at the level of L5 (Fig. 14).

Portal Vein: (Fig. 15)

The portal vein drains blood from the gastrointest inal tract , spleen, pancreas

and gallbladder to the l iver . I t is about 5 cm long and is formed by the union of

the superior mesenteric and splenic veins.

Tributaries:

1) Splenic vein

2) Inferior mesenteric vein:

3) Superior mesenteric vein.

4) Left gastr ic vein.

5) Right gastr ic vein.

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Figure (14): Aorta and inferior vena cava.

Figure (15): The portal vein.

ureter

Suprarenal

glands

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Liver:

The l iver is the largest gland in the body . I t weighs approximately 1500 g and

receives about 1500 ml of blood per minute. It has 2 surfaces: a diaphragmatic

surface & a visceral surface .

The liver may be divided into a large right lobe and a small left lobe by the

falciform ligament.

The r ight lobe is further divided into a quadrate lobe and a caudate lobe (Fig.

17).

Experiments have shown that, in fact, the quadrate and caudate lobes are a

functional part of the left lobe of the l iver.

The liver is made up of liver lobules . At the centre of each lobule is the central

vein . In the spaces between the lobules are the portal canals (portal tr iad),

which contain branches of the hepatic artery, portal vein, and a bile duct (Fig.

16).

Figure (16): Liver lobule

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Functions of the liver:

1) Production and secret ion of bile.

2) Involvement in carbohydrate, fat, and protein metabolism.

3) Production of heparin .

4) Removal of toxic substances.

5) Filtrat ion of the blood.

Figure (17): The l iver.

Common bile duct

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Blood Circulation through the Liver:

The blood vessels conveying blood to the l iver are the hepatic artery (30%) and

portal vein (70%).

The hepatic artery brings oxygenated blood to the l iver, and the portal vein

brings venous blood r ich in the products of digestion, which have been absorbed

from the gastrointestinal tract.

Bile Ducts of the Liver:

The bile ducts of the l iver consist of the right and left hepatic ducts , common

hepatic duct , common bile duct , gallbladder , and cystic duct (Figs. 17 & 18).

Gallbladder:

This is a pear-shaped sac lying on the undersurface of the l iver. It is divided

into fundus, body, and neck (Figs. 17 & 18). It concentrates & stores bile.

I t has a capacity to store 30 - 50 mL.

Pancreas:

The pancreas (Fig. 18) is both an exocrine and an endocrine gland. The

exocrine port ion produces a secret ion that contains the enzymes which are

involved in metabolism of proteins, fats, and carbohydrates. The endocrine

port ion (islets of Langerhans) produces insulin and glucagon .

The pancreas is divided into a head, neck, body, and tail.

The pancreatic duct opens with the common bile duct into the duodenum at the

major duodenal papilla (Ampulla of Vater) (Figs. 10 & 18).

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Figure (18): Liver, pancreas, spleen and gall bladder.

Figure (19): The spleen.

Common hepatic duct

Common bile duct

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Spleen:

The spleen (Figs. 18 & 19) is the largest single mass of lymphoid t issue in the

body. It is completely covered by peritoneum. It has also a capsule. It has

gastr ic, diaphragmatic & renal surfaces & has a notch called splenic notch .

The spleen is important for destruct ion of the old blood cells and in the

immunological defenses of the body.

Kidneys:

The kidneys play a major role in controll ing the water and electrolyte balance

and the acid–base balance of the blood. The waste products leave as urine.

The normal k idney measures about 12 * 6 * 3 cm & weighs about 130 g.

The kidneys are reddish brown and l ie behind the peritoneum. The r ight k idney

l ies slight ly lower than the left k idney because of the large size of the r ight lobe

of the l iver.

The hilum transmits the renal vein, renal artery, ureter and lymph vessels (Fig.

20).

Each kidney has an outer cortex and an inner medulla . The medulla is

composed of a dozen renal pyramids . The cortex extends into the medulla

between adjacent pyramids as the renal columns .

The upper end of the ureter is called the renal pelvis. This divides into two or

three major calyces , & this divides into two or three minor calyces . The minor

calyces open at the renal pyramids (Fig. 20) .

Suprarenal Glands:

The suprarenal glands are yellowish organs that l ie on the upper poles of the

kidneys (Fig. 14). Each gland has a cortex and a medulla.

The r ight suprarenal gland is pyramidal in shape, while the left is crescentic.

The cortex of the suprarenal glands secretes the mineralocorticoids ,

glucocorticoids , and sex hormones . . The medulla of the suprarenal glands

secretes the epinephrine and norepinephrine.

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Figure (20): The kidney.

renal column