Anatomy of Jejunum and Ileum

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Questions and Answers

What is the function of the root of the mesentery?

To enclose the mobile intestine

To attach the small intestine to the posterior abdominal wall

To permit the entrance and exit of blood vessels, lymphatic, and nerves (correct)

To divide the small intestine into jejunum and ileum

What is the approximate length of the root of the mesentery?

20 cm

5 cm

15 cm (correct)

10 cm

What is the name of the artery that supplies the lower part of the ileum?

Celiac artery

Ileocecal artery (correct)

Inferior mesenteric artery

Superior mesenteric artery

What is the name of the nodes where lymph from the small intestine drains?

Mesenteric lymph nodes Signup and view all the answers

What is the length of the large intestine?

1.5 meters Signup and view all the answers

What is the name of the sac-like structure that lies in the right iliac fossa?

Cecum Signup and view all the answers

What is the name of the orifice where the terminal part of the ileum enters the large intestine?

Ileocecal orifice Signup and view all the answers

What is the name of the structure that attaches the jejunum and ileum to the posterior abdominal wall?

Mesentery of the small intestine Signup and view all the answers

Which structures are related to the anterior aspect of the transverse colon?

Stomach, liver, and gall bladder Signup and view all the answers

What is the arterial supply to the proximal 2/3 of the transverse colon?

Middle colic artery Signup and view all the answers

What is the length of the descending colon?

25 cm Signup and view all the answers

What is the relation of the posterior aspect of the descending colon?

Psoas muscle, iliacus muscle, femoral nerve, and lateral cutaneous nerve of thigh Signup and view all the answers

What is the total length of the jejunum and ileum?

6 meters Signup and view all the answers

What is the difference in the longitudinal muscle layer between the small and large intestine?

The small intestine has a continuous layer, while the large intestine has three bands Signup and view all the answers

What is the peritoneum's relation to the descending colon?

It covers the front, sides, and binds it to the posterior abdominal wall Signup and view all the answers

What is the location of the jejunum in the abdominal cavity?

Upper left part Signup and view all the answers

What is the characteristic of the jejunum in terms of color and thickness?

Redder and thicker Signup and view all the answers

What is the arterial supply to the distal 1/3 of the transverse colon?

Left colic artery Signup and view all the answers

What is the difference in mobility between the small and large intestines?

The small intestine is mobile, while the large intestine is fixed Signup and view all the answers

What is the characteristic of the plica circulares in the jejunum?

Larger, more numerous, and closely set Signup and view all the answers

Where is the jejunal mesentery attached to the posterior abdominal wall?

Above and to the left of the aorta Signup and view all the answers

What is the characteristic of the jejunal mesenteric vessels?

Form only one or two arcades with long and infrequent branching Signup and view all the answers

Where are the pyres patches found?

Lower ileum Signup and view all the answers

What is the characteristic of the fat deposition in the jejunal mesentery?

Deposited near the root and scanty near the intestinal wall Signup and view all the answers

What is the location of the base of the appendix in relation to the ileocecal opening?

2.5 cm below the ileocecal opening Signup and view all the answers

What is the name of the mesentery that attaches the appendix to the lower layer of the mesentery of the small intestine?

Mesoappendix Signup and view all the answers

What percentage of the time is the appendix found in the retrocecal position?

74% Signup and view all the answers

What is the name of the point where the base of the appendix is located in relation to the anterior abdominal wall?

McBurney point Signup and view all the answers

What is the artery that supplies the appendix?

Appendicular artery Signup and view all the answers

What is the level of the spinal cord where the afferent nerve fibers from the appendix enter?

10th thoracic segment Signup and view all the answers

What is the direction of the ascending colon?

Upward from the cecum to the posteroinferior surface of the liver Signup and view all the answers

What is the length of the first part of the colon?

13 cm Signup and view all the answers

What is a characteristic feature of the wall of the small intestine?

It is smooth Signup and view all the answers

What is a common cause of an acute abdomen in young people?

Hyperplasia of lymphatic follicles in the appendix Signup and view all the answers

What is the result of thrombosis in the appendicular artery?

Ischemia, gangrene, and perforation of the inflamed appendix Signup and view all the answers

What is the consequence of rupture of the appendix?

Infection of the peritoneum Signup and view all the answers

Which of the following contributes to the appendix's predilection to infection?

It has a large amount of lymphoid tissue in its wall Signup and view all the answers

What is produced by distention of the lumen or spasm of the muscle in the appendix?

Visceral pain Signup and view all the answers

What is the result of secretions from the appendix that cannot escape?

The appendix swells, stretching the visceral peritoneum Signup and view all the answers

What type of tissue is present in the mucous membrane of the small intestine but not in the large intestine?

Plicacirculares Signup and view all the answers

Study Notes

Anatomy of the Small Intestine

The jejunum and ileum are 6 meters long, with the upper 2/5 being the jejunum.
The coils of the jejunum and ileum are freely mobile.
The jejunum begins at the duodenojejunal junction, and the ileum ends at the ileocecal junction.
They are attached to the posterior abdominal wall by a fan-shaped fold of peritoneum called the mesentery of the small intestine.

Distinguishing Features of Jejunum and Ileum

The jejunum lies coiled in the upper left part of the abdominal cavity, while the ileum lies coiled in the lower right part of the abdominal cavity and in the pelvis.
The jejunum is redder and thicker than the ileum due to the larger and more numerous plica circulares.
The jejunal mesentery is attached to the posterior abdominal wall above and to the left of the aorta, while the ileal mesentery is attached below and to the right of the aorta.
The jejunal mesenteric vessels form only one or two arcades with long and infrequent branching, whereas the ileal mesenteric vessels form three or four arcades with numerous and short vessels.
Peyer's patches are present in the mucous membrane of the lower ileum.
Fat is deposited near the root of the jejunal mesentery and is scanty near the intestinal wall, whereas in the ileal mesentery, fat is deposited throughout.

Arterial Supply and Lymph Drainage

The superior mesenteric artery supplies the jejunum and ileum through numerous jejunal and ileal branches that anastomose with each other to form arcades.
Lymph drainage passes to the mesenteric lymph nodes and then to the superior mesenteric nodes and finally to the celiac nodes.

Mesentery of the Small Intestine

The mesentery of the small intestine is a double-layered fold of peritoneum that attaches the whole length of the jejunum and ileum to the oblique line across the posterior abdominal wall.
It has a long free edge that encloses the mobile intestine and a short root that is continuous with the parietal peritoneum of the posterior abdominal wall.
The root of the mesentery is about 15 cm long and contains the superior mesenteric vessels, crossing the horizontal part of the duodenum, aorta, inferior vena cava, ureter on the right psoas, and right testicular or ovarian vessels.

Contents of the Mesentery

Jejunal and ileal blood vessels
Extraperitoneal fatty tissue
Plexus of autonomic nerves
Large lacteal lymph vessels

Large Intestine

Extends from the cecum in the right iliac fossa to the anus in the perineum, surrounding the centrally placed small intestine.
Divided into the cecum, vermiform appendix, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, and anal canal.

Cecum and Vermiform Appendix

The cecum is a blind-ended sac, about 7.5 cm in length and breadth, lying in the right iliac fossa.
The terminal part of the ileum enters the cecum at the ileocecal orifice.
The base of the appendix is attached to the posteromedial surface of the cecum and opens into it about 2.5 cm below the ileocecal opening.
The tip of the appendix has varying positions, including hanging down into the pelvis, coiled up behind the cecum, in front or behind the terminal part of the ileum, or projecting upward along the lateral side of the cecum.

Arterial Supply and Nerve Supply of the Appendix

The appendicular artery, a branch of the posterior cecal artery, supplies the appendix.
The appendix is supplied by sympathetic and parasympathetic (vagus) nerves from the superior mesenteric plexus.

Ascending Colon

The ascending colon is about 13 cm long and extends upward from the cecum to the posteroinferior surface of the liver, where it turns to the left, forming the right colic flexure.
Relations: anteriorly, the greater omentum, anterior abdominal wall, stomach, liver, and gallbladder; posteriorly, the second part of the duodenum, head of the pancreas, left kidney, and coils of the small intestine.

Descending Colon

The descending colon is about 25 cm long and extends downward from the left colic flexure to the sigmoid colon.
The peritoneum covers the front and sides and binds it to the posterior abdominal wall.
Relations: anteriorly, the greater omentum, anterior abdominal wall, and coils of the small intestine; posteriorly, the psoas muscle, iliacus muscle, femoral nerve, lateral cutaneous nerve of the thigh, left gonadal vessels, genitofemoral nerve, iliac crest, lower part of the left kidney, and origin of the transverse abdominis.

Differences between Small and Large Intestine

External differences:
- Small intestine is mobile, while ascending and descending colon are fixed.
- Caliber of small intestine is smaller than that of large intestine.
- Small intestine has a mesentery that passes downward across the midline into the right iliac fossa.
- Longitudinal muscle of small intestine forms a continuous layer around the gut, whereas in large intestine, it is collected into three bands (teniae coli).
- Small intestine has no fatty tags (appendices epiploicae) attached to its wall.
Internal differences:
- Mucous membrane of small intestine has plicacirculares, villi, and Peyer's patches, which are absent in large intestine.

Appendicitis

Acute inflammation of the appendix, caused by hyperplasia of lymphatic follicles in the appendix that occludes the lumen.
Symptoms: digital pressure over the McBurney point registers maximum abdominal tenderness.
Complications: thrombosis in the appendicular artery, ischemia, gangrene, and perforation of an inflamed appendix, leading to peritonitis.

Predisposition of the Appendix to Infection

The appendix is prone to infection due to its long, narrow, blind-ended tube structure, which encourages stasis of large-bowel contents.
The appendix has a large amount of lymphoid tissue in its wall.
The lumen has a tendency to become obstructed by hardened intestinal contents (enteroliths), leading to further stagnation of its contents.

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Description

This quiz covers the anatomy of the jejunum and ileum, including their length, structure, and attachments to the abdominal wall. It also distinguishes between the two parts of the small intestine.