1. Anatomy of small intestine & Large intestine
Dr. Mohammed Abuelnor

2. OBJECTIVES At the end of the lecture, students should:
List the different parts of small intestine.
Describe the anatomy of duodenum, jejunum & ileum regarding: the shape, length, site of beginning & termination, peritoneal covering, arterial supply & lymphatic drainage.
Differentiate between each part of duodenum regarding the length, level & relations.
Differentiate between the jejunum & ileum regarding the characteristic anatomical features of each of them.
List the different parts of large intestine.
List the characteristic features of colon.
Describe the anatomy of different parts of large intestine regarding: the surface anatomy, peritoneal covering, relations, arterial & nerve supply.

3. Small Intestine Is the longest part of the alimentary canal
Extends from pylorus to the ileocecal junction
The greater part of digestion and food absorption takes place here
Is divided into three parts: Duodenum, Jejunum and Ileum

4. FIXED (Retro peritoneal) PART
FREE (MOVABLE) PART
(WITH MESENTERY)
JEJUNUM & ILEUM
FIXED (Retro peritoneal) PART
(NO MESENTERY)
DUODENUM
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5. DUODENUM SHAPE: C-shaped loop LENGTH: 10 inches
BEGINNING: at pyloro- duodenal junction
TERMINATION: at duodeno-jejunal flexure
PERITONEAL COVERING: retroperitoneal
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6. PARTS The duodenum is divided into (4) parts: 1st : Superior.
2nd : Descending (vertical).
3rd : Inferior (Horizontal)
4th : Ascending
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7. LENGTH – SURFACE ANATOMY
PART
LENGTH
LEVEL
FIRST PART
(Superior)
2 INCHES L1
(Transpyloric
Plane)
SECOND PART
(Descending
3 INCHES
DESCENDS FROM L1 TO L3
THIRD PART
(Horizontal)
4 INCHES
L3 (SUBCOTAL PLANE)
FOURTH PART
(Ascending)
1 INCHES
ASCENDS FROM L3 TO L2
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8. RELATIONS OF FIRST PART3) 2) 1) X X
Anterior
Liver
Posterior
1)Bile duct
2) Gastroduodenal artery
3)Portal vein

9. RELATIONS OF SECOND PART
Posterior
Right kidney
Anterior
1)Liver
2)Transverse Colon
3)Small intestine X
Lateral
R Colic
Flexure
Medial
Pancreas

10. OPENINGS IN SECOND PART OF DUODENUM
Common opening of bile duct & main pancreatic duct: on summit of major duodenal papilla.
Opening of accessory pancreatic duct (one inch higher): on summit of minor duodenal papilla.
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11. RELATIONS OF THIRD PART
Anterior:
a)Small intestine
b) Superior mesenteric vessels
Posterior:
1) Right psoas major
2) Inferior vena cava
3) Abdominal aorta
4) Inferior mesenteric vessels.
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12. RELATIONS OF FOURTH PART
Anterior:
Small intestine
Posterior:
Left psoas major
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13. Blood Supply & Lymph drainage
Because the duodenum is derived from both: Foregut & Midgut,
It has its Arterial Supply from :
Celiac & Superior mesenteric arteries.
Venous Drainage to :
Superior mesenteric& Portal veins.
LYMPHATIC DRAINAGE: Celiac & Superior mesenteric lymph nodes.
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14. JEJUNUM & ILEUM SHAPE: Coiled tube LENGTH: 6 meters (20 feet)
BEGINNING: at Duodeno- jejunal flexure
TERMINATION: at Ilieo- caecal junction
EMBRYOLOGICAL ORIGIN: Midgut
Blood SUPPLY: Superior mesenteric A & V
LYMPHATIC DRAINAGE: Superior mesenteric lymph nodes

15. JEJUNUM
ILEUM
LENGTH
Shorter (proximal 2/5) of SI
Longer (distal 3/5) of SI
DIAMETER
Wider
Narrower
WALL
Thicker (more plicae circulares)
Thinner (less plicae circulares)
APPEARANCE
Dark red (more vascular)
Light red (less vascular)
VESSELS
High & Less arcades (long terminal branches)
Low & More arcades (short terminal branches
MESENTERIC FAT
Small amount & away from intestinal border
Large amount & close to intestinal border
LYMPHOID TISSUE
Few aggregations
Numerous aggregations (Peyer’s patches)

16. Large Intestine Extends from the ileum to the anus
Is divided into the cecum, appendix, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, and anal canal
Its primary function is the absorption of water and electrolytes, and storage of undigested material
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17. (3) longitudinal muscle bands 2. Sacculations (Haustra):
Characteristics of COLON (NOT FOUND IN RECTUM & ANAL CANAL
Taeniae coli:
(3) longitudinal muscle bands
2. Sacculations (Haustra):
Because the Taeniae coli are shorter than large intestine
3. Epiploic Appendices : Short peritoneal folds filled with fat
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18. Peritoneal Covering PARTS WITH MESENTERY: Sigmoid colon Appendix Cecum
Transverse colon
Sigmoid colon
Appendix
Cecum
RETROPERITONEA L PARTS:
Ascending colon
Descending colon
3. Upper 2/3 of rectum
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19. Peritoneal Covering PARTS DEVOID OF PERITONEAL COVERING:
Lower 1/3 of rectum
Anal canal
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20. Anterior Relations of (CECUM – ASCENDING & DESCENDING COLONS)
1. Greater omentum
2. Coils of small intestine
Anterior abdominal wall
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21. Posterior Relations (CECUM – ASCENDING & DESCENDING COLONS)
Psoas major
Iliacus
Ascending colon:
Quadratus lumborum
Right kidney.
Descending colon:
Left kidney
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22. COLIC FLEXURES Position: higher Angle: more acute Hepatic flexure
Splenic flexure

23. Relations of Transverse Colon
Anterior: greater omentum, anterior abdominal wall
Posterior: 2nd part of duodenum , pancreas & superior mesenteric vessels.

24. Relations of Transverse Colon
Superior: liver, gall bladder, stomach
Inferior: coils of small intestine

25. Appendix
It is a narrow, muscular tube containing a large amount of lymphoid tissue
Varies in length from 3-5 inches
Base is attached to the posteromedial surface of the cecum about 1 inch below the ileocecal junction
The remainder of the appendix is free
Has a complete peritoneal covering
Small mesentery is known as mesoappendix

26. APPENDIX Surface anatomy:
the base of appendix is marked by Mc’Burney’s point:
A point at the junction of lateral 1/3 & medial 2/3 of a line traced from right anterior superior iliac spine to umbilicus
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27. APPENDIX
Opening:
At posteromedial aspect of cecum, 1 inch below ileo- cecal junction
Positions:
1.Retrocecal :(most common)
2.Pelvic
3.Subcecal
4.Preilieal
5.Postileal: least common
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28. RECTUM Beginning: as a continuation of sigmoid colon at level of S3.
Termination: continues as anal canal, one inch below & in front of tip of coccyx. Its end is dilated to form the rectal ampulla.
Length: 13 cm(5 inches)
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29. Relations of Rectum in Pelvis
MALE PELVIS
Anterior: seminal vesicles, posterior surfaces of urinary bladder & prostate gland
Posterior: sacrum, sacral plexus & coccyx
FEMALE PELVIS
Anterior: posterior wall of vagina
Posterior: sacrum , sacral plexus & coccyx
Anterior: posterior wall of vagina
Posterior: sacrum , sacral plexus & coccyx
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30. Relation Between Embryological Origin of GIT& its Arterial Supply

31. VENOUS DRAINAGE OF GIT
The veins of the gut form the tributaries of the portal vein which enters the liver and drains into the portal circulation.
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32. Lymph drainage of GIT The lymph vessels follow the arteries.
Ultimately, all the lymph is collected at the Preaortic lymph nodes (Celiac , Superior & Inferior mesenteric).
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33. RELATION BETWEEN EMBRYOLOGICAL ORIGIN & NERVE SUPPLY
Origin: Midgut (endoderm)
Nerve supply: (Autonomic):
Sympathetic + Vagus
Origin: Hindgut (endoderm)
Sympathetic + pelvic splanchnic nerves
Origin: ectoderm (lower 1/3 of anal canal)
Nerve Supply: Somatic (inferior rectal)
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34. References Gray's Anatomy for Students- Second edition.
Clinically Oriented Anatomy , Keith L. Moore- Sixth edition.
Netter’s Clinical Anatomy, Second edition.