Anatomy of small intestine & Large intestine Dr. Mohammed Abuelnor

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.

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

FIXED (Retro peritoneal) PART FREE (MOVABLE) PART (WITH MESENTERY) JEJUNUM & ILEUM FIXED (Retro peritoneal) PART (NO MESENTERY) DUODENUM اسم ورقم المقرر – Course Name and No. 5/1/2019

DUODENUM SHAPE: C-shaped loop LENGTH: 10 inches BEGINNING: at pyloro- duodenal junction TERMINATION: at duodeno-jejunal flexure PERITONEAL COVERING: retroperitoneal اسم ورقم المقرر – Course Name and No. 5/1/2019

PARTS The duodenum is divided into (4) parts: 1st : Superior. 2nd : Descending (vertical). 3rd : Inferior (Horizontal) 4th : Ascending 5/1/2019

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 اسم ورقم المقرر – Course Name and No. 5/1/2019

RELATIONS OF FIRST PART 3) 2) 1) X X Anterior Liver Posterior 1)Bile duct 2) Gastroduodenal artery 3)Portal vein

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

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. اسم ورقم المقرر – Course Name and No. 5/1/2019

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. اسم ورقم المقرر – Course Name and No. 5/1/2019

RELATIONS OF FOURTH PART Anterior: Small intestine Posterior: Left psoas major اسم ورقم المقرر – Course Name and No. 5/1/2019

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. اسم ورقم المقرر – Course Name and No. 5/1/2019

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

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)

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 اسم ورقم المقرر – Course Name and No. 5/1/2019

(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 اسم ورقم المقرر – Course Name and No. 5/1/2019

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 اسم ورقم المقرر – Course Name and No. 5/1/2019

Peritoneal Covering PARTS DEVOID OF PERITONEAL COVERING: Lower 1/3 of rectum Anal canal اسم ورقم المقرر – Course Name and No. 5/1/2019

Anterior Relations of (CECUM – ASCENDING & DESCENDING COLONS) 1. Greater omentum 2. Coils of small intestine Anterior abdominal wall اسم ورقم المقرر – Course Name and No. 5/1/2019

Posterior Relations (CECUM – ASCENDING & DESCENDING COLONS) Psoas major Iliacus Ascending colon: Quadratus lumborum Right kidney. Descending colon: Left kidney 5/1/2019

COLIC FLEXURES Position: higher Angle: more acute Hepatic flexure Splenic flexure

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

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

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

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 اسم ورقم المقرر – Course Name and No. 5/1/2019

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 اسم ورقم المقرر – Course Name and No. 5/1/2019

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) اسم ورقم المقرر – Course Name and No. 5/1/2019

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 اسم ورقم المقرر – Course Name and No. 5/1/2019

Relation Between Embryological Origin of GIT& its Arterial Supply

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. اسم ورقم المقرر – Course Name and No. 5/1/2019

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). اسم ورقم المقرر – Course Name and No. 5/1/2019

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) اسم ورقم المقرر – Course Name and No. 5/1/2019

References Gray's Anatomy for Students- Second edition. Clinically Oriented Anatomy , Keith L. Moore- Sixth edition. Netter’s Clinical Anatomy, Second edition. 17-11-19