HUMAN ANATOMY – VOLUME 1

Between the large intestine and the abdominal walls and neighboring organs there are ligaments, which are formed by folds of the peritoneum. These ligaments form a fixating apparatus, which prevents shifting and ptosis of the colon, and provide passages for blood vessels. The superior ileocecal ligament is a continuation of the mesentery. It attaches to the lower medial surface of the ascending colon. Its base is connected with the peritoneum of the right mesenteric sinus. The mesentericopudendal ligament begins on the mesentery of the terminal part of the ileum. It forms a triangular structure, which descends toward the right edge of the inlet into the lesser pelvis. In the female this ligament continues onto the suspensory ligament of the ovary, and in the males — into the deep ring of the inguinal canal, where it passes into the parietal peritoneum. The left diaphragmaticocolic ligament stretches between the costal part of the diaphragm and the left colic flexure. The bottom of this ligament attaches in the splenic angle between the transverse and descending colons, connecting them to each other. Usually this ligament is accreted with the greater omentum. Other ligaments may be present but are not constant.

I n n e r v a t i o n: colon — branches of vagus nerves and sympathetic fibers from the superior and inferior mesenteric plexuses; rectum — parasympathetic pelvic nerves and sympathetic fibers from the inferior hypogastric plexuses.

B l o o d s u p p l y: colon — superior and inferior mesenteric arteries; rectum — rectal arteries from the inferior mesenteric and iliac arteries.

Ve n o u s o u t f l o w: colon — superior and inferior mesenteric veins; rectum — inferior mesenteric vein, inferior vena cava (through medial and inferior rectal veins).

Ly m p h o u t f l o w: caecum and appendix — ilieocolic, precaecal and retrocaecal lymph nodes. Ascending, transverse and descending colons — mesentericocolic, paracolic, right, middle and left colic lymph nodes. Sigmoid colon — inferior mesenteric (sigmoid) lymph nodes. Rectum — internal iliac (sacral), subaortal and rectal lymph nodes.

Questions for revision and examination

1.Name the parts of the large intestine and describe each of these parts.

2.Describe the differences between the small and large intestines.

3.Describe the surface relief of mucosa of the rectum, particularly its lower section.

4.Describe the structure of the mucosa of the large intestine.

5.Describe the muscularis of the large intestine. Name its sphincters and ligaments.

!#

LIVER

The liver (hépar) is the largest gland of the body. It is shaped like a flattened and somewhat distorted top of a sphere. Its consistence is that of a soft solid and its color is reddish-brown. In an adult the liver measures 20–30 cm in length, 10–21 cm in width, and between 7 and 15 cm in height. It weights 1400 – 1800 g. The liver participates in the metabolism of proteins, lipids, carbohydrates and vitamins. It also carries out functions of defense and decontamination, bile production and more. During embryogenesis it is an organ of hemopoiesis.

The liver has visceral and diaphragmatic surfaces. The d i a p h r a g - m a t i c s u r f a c e faces upward and to the front. The v i s c e r a l s u r - f a c e is flat and is directed downward and to the back (Fig. 139). The inferior border of the liver is sharp, while in the back the liver is rounded.

The liver is located mostly in the subcostal region and, partially, in the epigastrium. It projects onto the skeleton so that its highest point along the right midclavicular line is at the level of the fifth intercostals space. Along the midclavicular line the inferior margin of the liver normally corresponds to the tenth intercostal space. The inferior margin extends forward along the right costal arch. It passes upward from left to right, cross-

Fig. 139. Liver. Visceral surface.

1 — bile duct; 2 — cystic duct; 3 — gallbladder; 4 — right lobe; 5 — falciforme ligament; 6 — round ligament of liver; 7 — quadrate lobe; 8 — left lobe; 9 — hepatic artery proper; 10 — vena portae hepatis; 11 — caudate lobe; 12 — inferior vena cava.

!#

ing the epigastrium. At the level of the sixth left costal cartilage, to the left of the sternum, the inferior border (left lobe) crosses the costal arch and meets the upper border of the liver. In the back (along the right scapular line) the superior border of the liver projects into the seventh intercostal space, and the inferior border — onto the upper edge of the eleventh rib.

At the top the diaphragmatic surface adjoins the right and, partially, left cupulae of the diaphragm. The front upper part of the liver lies against the costal part of the diaphragm and the front abdominal wall. In the back it adjoins the T10 and T11 vertebrae, peduncles of the diaphragm, abdominal part of the esophagus, the aorta and the right adrenal gland. Below the liver lie the cardia, body and pyloric region of the stomach, superior part of the duodenum, right kidney, right colic flexure and right part of the transverse colon (see «visceral surface of the liver»).

The diaphragmatic surface of the liver has a smooth glistering texture. It is covered with peritoneum, except for a small area on the posterior side. The peritoneum passes onto the liver from the diaphragm, forming duplications, which act as ligaments. The f a l c i f o r m l i g a m e n t is situated in the sagittal plane; it passes onto the diaphragmatic surface from the diaphragm and the anterior abdominal. Oriented within the frontal plane is the c o r o n a r y l i g a m e n t, which connects with the posterior end of the falciform ligament. The right and left ends of the coronal ligament spread out, forming the r i g h t and l e f t t r i a n g u l a r l i g a m e n t s of the liver. Passing through the free margin of the falciform ligament is the r o u n d l i g a m e n t, which shape is like a cord. This ligament is the obliterated umbilical vein, which connects the umbilicus and the hilum of the liver. Between the hilum of the liver and the lesser curvature of the stomach and beginning of the duodenum a duplication of peritoneum form the h e p a t o - g a s t r i c and h e p a t o d u o d e n a l l i g a m e n t s. On the diaphragmatic surface of the left lobe there is a c a r d i a c i m p r e s s i o n, formed by the heart, which adjoins the liver through the diaphragm.

Anatomically, the liver is divided into the r i g h t and l e f t l o b e s, which are divided by the falciform ligament. On the visceral surface the border between these lobes is marked by the groove of the round ligament and the fissure for the ligamentum venosum. The v e n o u s l i g a m e n t is the obliterated venous duct, which, in the fetus, connected the umbilical vein with the inferior vena cava.

On a visceral surface of the liver, to the right of the round ligament and fissure of the venous ligament is the right sagittal fissure. Towards the front this fissure widens, forming the fossa for gallbladder. In the back it forms the fissure of the inferior vena cava. Between the right and the left sagittal fissures there is a deep transverse fissure, known as the p o r t a h e p a t i s, or portal fissure. The porta hepatis is situated behind the fossa

!#

forward, reaching the portal fissure next to the fissure for ligamentum venosum.

On the underside of the liver there are several impressions formed by adjoining organs. In the left region there is a g a s t r i c i m p r e s s i o n. On the posterior part of the left lobe is the o e s o p h a g e a l i m p r e s - s i o n. On the quadrate lobe, near the fossafor gallbladder is the duodenal impression. To its right, on the right lobe, there is an impression formed by the right kidney. To the left of the renal impression, near the groove for vena cava, is the suprarenal impression. Along the inferior margin of the visceral surface is the c o l i c i m p r e s s i o n.

The liver is made up of five s e c t o r s and eight s e g m e n t s (Fig. 140). A sector is a fragment, supplied with blood by second level branches of the portal vein and hepatic artery. Each such fragment contains a sector bile duct. A segment is a part of the liver, which receives blood supply from a third level branch of the portal vein and contains a segmental bile duct. Segments are numbered on the visceral surface of the liver beginning at the

!#!

Fig. 141. Construction of hepatic lamina (acc. to V.G.Eliseev).

1 — hepatocyte; 2 — hepatic lamina; 3 — haemocapillare (sinusoid vessel); 4 — perisinusoidal space of Disse; 5 — central vein; 6 — perisinusoidal lypocyte; 7 — bile capillare; 8 — reticulocyte; 9 — endotheliocyte; 10 — perilobular bile canaliculus; 11 — perilobular artery; 12 — perilobular vein.

fissure of the inferior vena cava, in the clockwise direction. The right lobe contains segments 1–4, and the left lobe — segments 5–8.

The fibrous capsule of the liver gives off thin connective tissue septa into its parenchyma, dividing it into lobules. A lobule is the functional unit of the liver. It is shaped like a prism with a diameter of 1.0–1.5 mm (Fig. 141, 142). The total number of lobules is approximately 500 thousand. Each lobule consists of cords of hepatocytes, which begin in the center of the lobule and spread out to its periphery. Each cord consists of two rows of hepatocytes. Situated between two rows of cells of a cord are initial parts of the biliary ducts. Between the cords are blood capillaries (sinusoids), which collect into the central vein of the lobule. The space between

!#"

Fig. 142. Blood supply of liver. (acc to V.G.Eliseev and others).

1 — portal vein; 2 — hepatic artery proper; 3 — segmental vein and artery; 4 — interlobular artery and vein; 5 — perilobular veins and arteries; 6 — intralobular haemocapillaries (sinusoid vessels); 7 — central vein; 8 — hepatic lobule («classic»); 9 — collective vein; 10 — hepatic veins.

the walls of sinusoid capillaries and hepatocytes is called p e r i s i n u s o - i d a l (Disse’s) s p a c e. Between lobules there is a small amount of connective tissue, which contains hepatic triad complexes that include an interlobular bile duct and branches of the portal vein and hepatic artery. Such a construction allows hepatocytes to simultaneously excrete bile into bile ducts, and glucose, lipids, urea, vitamins and other substances—into to blood vessels.

H e p a t o c y t e s are polygonal cells with a diameter of 20–25 mm. Most hepatocytes have only one nucleus, but some have two or several. Their cytoplasm may be coarse or fine-grained, depending on the composition of its inclusions (lipids, pigments). Hepatocytes contain a lot of mitochondria, a well-developed endoplasmic reticulum and Golgi complex, and a large amount of ribosomes, lysosomes and micro-vesicles, contain-

!##

ing lipid metabolism enzymes. The cytoplasm contains grains of glycogen. The cell membrane of hepatocytes forms numerous microvilli, directed into the perisinusoidal space.

Biliary system

The liver is a compound tubular gland with a branching system of bile ducts. Bile ductules, or canaliculi, begin in the hepatic acini, where the width of their lumens is 0.5–1.0 mm. These canaliculi do not have walls, but are dilated zones of intercellular fissures between hepatocytes. Bile ductules have short blind branches, which extend between neighboring hepatocytes. Bile ductules begin blindly near the central vein and pass to the peripheries of lobules, where they collect into short bile ducts called c h o l a n g i o l e s (intermediate canals of Hering), which open into i n - t e r l o b u l a r b i l e d u c t s. The interlobular ducts connect with each other, gradually increasing in diameter, and form the r i g h t and l e f t h e p a t i c d u c t s. In the porta hepatis these two ducts are connected with each other and form the c o m m o n h e p a t i c d u c t, which is 4–6 cm long. Between the sheets of the hepatoduodenal ligament the common hepatic duct is connected with the c y s t i c d u c t (from the gallbladder), forming the common bile duct.

The bile duct (dúctus cholédochus) is situated between the sheets of hepatoduodenal ligament, in front of the portal vein and to the right of the hepatic artery. Further the bile duct passes behind the superior part of the duodenum, and then between its descending part and the head of the pancreas. Inside the wall of the duodenum it connects with the p a n c r e - a t i c d u c t, forming the h e p a t o p a n c r e a t i c a m p u l l a. This ampulla opens into the duodenum through the apex of the major duodenal papilla. In the walls of the hepatopancreatic ampulla there is a s p h i n c - t e r (sphincter of Oddi), formed by a thickening of circular muscle fascicles. The distribution of muscle fascicles of the sphincter is uneven. Their thickness near the base of the major papilla reaches 75 mm, and closer to the top of the papilla — 40 mm. The width of the sphincter is 15–20 mm. In periods between digestion the sphincter of Oddi stays closed and bile accumulates in the gallbladder. During digestion the sphincter opens and bile enters the duodenum.

The walls of the bile duct contain another sphincter, which is situated just before its junction with the main pancreatic duct. By closing this sphincter prevents bile from entering the hepatopancreatic ampulla and the duodenum.

The walls of interlobular ducts are formed by simple cuboidal epithelium. The walls of the hepatic, cystic and bile ducts are formed by three

!#$

layers. Their m u c o s a is lined with simple columnar epithelium, which contains goblet cells. The lamina propria of the mucosa is well developed and contains a large amount of longitudinal and circular elastic fibers and some multicellular mucous glands. The s u b m u c o s a is weakly developed. The m u s c u l a r i s is thin, and consists primarily of spiral muscle fascicles, the spaces between which are filled with connective tissue.

I n n e r v a t i o n o f t h e l i v e r: branches of vagus nerves and hepatic (sympathetic) plexus.

Blood vessels of the liver: The porta hepatica contains the hepatic artery and portal vein. The artery carries arterial blood. The hepatic portal vein brings venous blood from the stomach, pancreas, intestines, and spleen. Inside the liver the portal vein and hepatic artery branch out into interlobular arteries and veins, which stay together with interlobular bile ducts within the hepatic triads. The interlobular veins and arteries branch out into the sinusoids, which collect into the central vein. Central veins of the liver lobules connect with each other, forming sublobular (collecting) veins. These veins merge with each other, increasing in diameter, and, finally, form 2–3 hepatic veins. The hepatic veins exit the liver through the groove of the inferior vena cava, where they join the latter.

Ly m p h o u t f l o w: hepatic, celiac, right lumbar, superior diaphragmatic and parasternal lymph nodes.

Gallbladder

The gallbladder (vésica féllea) is a pear-shaped organ, in which bile is accumulated and concentrated. It is situated in the right subcostal region. Its upper surface adjoins the fossa for gallbladder on the visceral surface of the liver. Its free lower surface is turned into the abdominal cavity and is covered by peritoneum. It adjoins the front wall of the superior part of duodenum and the right colic flexure. The length of the gallbladder is 8–12 cm, and the width is 4–5cm.. Its volume is approximately 40 cm3. The gallbladder has a broadened f u n d u s, a b o d y and a n e c k. Its f u n d u s slightly protrudes from underneath the inferior margin of the liver, next to the junction of the eighth and ninth costal cartilages. It continues into the gallbladder body, which narrows and becomes the neck. The neck forms the beginning of the cystic duct. The n e c k and cystic duct, which are directed toward the porta hepatis, lie within the hepatoduodenal ligament. At the transition between its body and neck the gallbladder forms a flexure, such that the neck and the body are situated at an angle to each other.

The wall of the gallbladder consists of the m u c o s a, s u b m u c o s a, m u s c u l a r c o a t and s e r o s a. The mucosa is thin, and forms numer-

!#%

ous tiny folds. In the region of the neck these rugae have a spiral orientation. The gallbladder mucosa is lined with simple columnar epithelium. The well-developed lamina propria contains solitary and small groups of lymphocytes, mucous glands, blood vessels and nerves. The submucosa of the gallbladder is thin. The muscularis layer is formed by a single layer of smooth myocytes, which form longitudinal and spiral fascicles. The muscularis is less developed in the fundus, and is thicker in the neck, where it continues into the muscle layer of the cystic duct. To the outside of the muscularis is the subserosa and serosa, which is formed by the peritoneum. The peritoneum covers the gallbladder from the sides and bottom, while its hepatic surface is covered by adventitia.

I n n e r v a t i o n of the gallbladder: branches of the vagus nerves and the hepatic (sympathetic) plexus.

B l o o d s u p p l y: cystic artery (from hepatic artery). Ve n o u s o u t f l o w: cystic vein (into portal vein).

Ly m p h a t i c r e t u r n: hepatic and cystic lymphatic nodes.

Questions for revision and examination

1.Where on the front abdominal wall do projections of the superior and inferior liver margins meet in an adult person?

2.What organs adjoin the visceral surface of the liver?

3.What is a liver lobule? How is it structured?

4.Describe the sizes and volume of the gallbladder.

5.Describe the structure and topography of the common bile duct.

PANCREAS

The pancreas (páncreas) – is an elongated pinkish-gray organ, which lies retroperitoneally (Fig.143). The pancreas is a large alimentary gland, which produces mixed secretion. It has an exocrine compartment, consisting of typical secretory sections and excretory duct system, and an endocrine part. As an exocrine gland it produces 500–700 ml of pancreatic juice per day. This juice contains proteolytic, amylolytic and lipolytic enzymes (trypsinogen, chymotrypsinogen, prolipase, amylase, etc.). The endocrine part of the gland consists of numerous groups of cells (pancreatic islets), which produce hormones that regulate metabolism of carbohydrates and lipids (insulin, glucagon, etc).

The pancreas is 14–18 cm long, 6–9 cm wide and 2–3 cm thick. It weights 85–95 g. The gland is covered by a thin connective tissue capsule. It extends from the level of the T12 vertebra obliquely downward and to the right, to the level of L1-L3 vertebrae. The pancreas consists of a head, body and tail.

!#&

Fig. 143. Pancreas. Anterior aspect. Duct is opened. Anterior wall of pancreas is cut and pulled aside.

1 — body of pancreas; 2 — pancreatic duct; 3 — tail of pancreas; 4 — duodeno-jejunal flexure; 5 — ascending part of duodenum; 6 — jejunum; 7 — uncinate process; 8 — horizontal part of duodenum; 9 — circular folds; 10 — major duodenal papilla; 11 — longitudinal fold of duodenum; 12 — minor duodenal papilla; 13 — descending part of duodenum; 14 — accesory pancreatic duct; 15 — superior part of duodenum.

The h e a d o f t h e p a n c r e a s (Fig.144) is slightly flattened and resembles the head of a hammer. The boundary between the head and the body is marked by the p a n c r e a t i c n o t c h, located on its lower edge. The head is turned toward the medial wall of the duodenum. In the fissure between the head and duodenal wall passes the superior mesenteric vein and, usually, the anastomosis between the superior and inferior pancreaticoduodenal arteries. In the back the head of the pancreas lies against the inferior vena cava, right renal vein and the beginning part of the portal vein. In front of the head lies the transverse colon.

The b o d y o f t h e p a n c r e a s is trihedral in shape. It has three surfaces. The a n t e r o s u p e r i o r s u r f a c e is covered by parietal peritoneum, which forms the posterior wall of the omental bursa. On this surface there is an o m e n t a l e m i n e n c e. The p o s t e r i o r s u r f a c e of the body adjoins the vertebral column, inferior vena cava, aorta, splen-

!#'