SMALL & LARGE INTESTINE Dr. Ahmed Fathalla Ibrahim

ABDOMINAL VISCERA FOR EACH PART YOU MUST KNOW: SURFACE ANATOMY RELATIONS PERITONEAL COVERING BLOOD SUPPLY NERVE SUPPLY LYMPHATIC DRAINAGE SUPPORT (IN SOME PARTS)

SMALL INTESTINE DUODENUM: fixed part JEJUNUM & ILEUM: movable part (with mesentery)

JEJUNUM & ILEUM Length: 6 meters (20 feet) Beginning: duodenojejunal flexure Termination: ileocecal junction Embryological origin: midgut Peritoneal fold: mesentery of small intestine Arterial supply: jejunal & ileal branches of superior mesenteric Lymphatic drainage: superior mesenteric lymph nodes Nerve supply: superior mesenteric plexus: sympathetic & parasympathetic (vagus)

MESENTERY OF SMALL INTESTINE Extent: from duodenojejunal flexure to ileocecal junction Formation: formed of 2 layers Free border (6 meters long): encloses jejunum & ileum Root (6 inches long, J-shaped): crosses superficial to the following structures: Third part of duodenum Abdominal aorta Inferior vena cava Right psoas major Right ureter

MESENTERY OF SMALL INTESTINE Shape: Fan-shaped with undulations Content of root: superior mesenteric vessels Contents (structures between its 2 layers): Jejunal vessels: form few arcades Ileal vessels: form many arcades Mesenteric lymph nodes Autonomic nerve fibers Mesenteric fat

MESENTERY OF SMALL INTESTINE

JEJUNUM Length: shorter (proximal 2/5) Diameter: wider Wall: thicker (more numerous plicae circulares: circular folds of mucosa) Appearance: more red in color (more vascular) Vessels: less arcades, long terminal branches Mesenteric fat: small amount near intestinal border Aggregations of lymphoid tissue: few

ILEUM Length: longer (distal 3/5) Diameter: narrower Wall: thinner (less numerous plicae circulares: circular folds of mucosa) Appearance: light red in color (less vascular) Vessels: more arcades, short terminal branches Mesenteric fat: large amount near intestinal border Aggregations of lymphoid tissue: numerous (Peyer’s patches)

LARGE INTESTINE PARTS: Cecum Appendix Ascending colon Transverse colon Descending colon Sigmoid (pelvic) colon Rectum Anal canal N.B.: Parts of large intestine in abdomen: from 1 to 5

LARGE INTESTINE CHARACTERISTICS: Teniae coli: 3 longitudinal muscle bands Sacculations (haustrations): teniae coli are shorter than large intestine Appendices epiploicae: short peritoneal fold filled with fat N.B.: characteristics are present in all large intestine EXCEPT: in rectum & anal canal

LARGE INTESTINE Embryological origin: From midgut: cecum, appendix, ascending colon, right 2/3 of transverse colon From hindgut: left 1/3 of transverse colon, descending & sigmoid colon, rectum, upper half of anal canal Peritoneal fold: Appendix, transverse & sigmoid colon: have mesentery Cecum: completely covered by peritoneum, but has no mesentery Ascending & descending colon: covered anteriorly & on the sides Rectum & anal canal: discussed later

LARGE INTESTINE Arterial supply: Midgut: colic branches of superior mesenteric Hindgut: inferior mesenteric Lymphatic drainage: Midgut: superior mesenteric lymph nodes Hindgut: inferior mesenteric lymph nodes Nerve supply: Superior mesenteric plexus: sympathetic & parasympathetic (vagus) Inferior mesenteric plexus: sympathetic & parasympathetic (pelvic splanchnic nerves)

LARGE INTESTINE SURFACE ANATOMY

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 Opening: at posteromedial aspect of cecum, 1 inch below ileo-cecal junction

APPENDIX Positions: (from most to least common) Retrocecal: most common position Pelvic Subcecal Preilieal Postileal

CECUM, ASCENDING & DESCENDING COLON ANTERIOR RELATIONS: Coils of small intestine Greater omentum Anterior abdominal wall

1 2 Iliac crest 5 4 3 6 1: Iliohypogastric nerve; 2: Ilioinguinal nerve; 3: lateral cutaneous nerve of thigh 4: Femoral nerve; 5: Genitofemoral nerve; 6: Obturator nerve P.M.= psoas major; Q.L.=quadratus lumborum; I.=iliacus; T.A.= transversus abdominis

1 2 5 3 6 4 1: Iliohypogastric nerve; 2: Ilioinguinal nerve; 3: lateral cutaneous nerve of thigh 4: Femoral nerve; 5: Genitofemoral nerve; 6: Obturator nerve P.M.= psoas major; Q.L.=quadratus lumborum; I.=iliacus; T.A.= transversus abdominis

CECUM, ASCENDING & DESCENDING COLON POSTERIOR RELATIONS: Cecum: psoas major, genitofemoral nerve, iliacus, lateral cutaneous nerve of thigh, femoral nerve Ascending colon: iliacus, lateral cutaneous nerve of thigh, quadratus lumborum, ilioinguial nerve, iliohypogastric nerve, iliac crest, origin of transversus abdominis from lumbar fascia Descending colon: relations of cecum + relations of ascending colon + left kidney

RELATIONS OF TRANSVERSE COLON

RELATIONS OF TRANSVERSE COLON ANTERIOR: greater omentum, anterior abdominal wall POSTERIOR: 2nd part of duodenum, head of pancreas, coils of small intestine SUPERIOR: liver, gall bladder, stomach INFERIOR: coils of small intestine