•ANATOMY OF THE

LARGE INTESTINE

Dr. Ahmed Fathalla IbrahimAssociate Professor of AnatomyCollege of MedicineKing Saud UniversityE-mail: ahmedfathala@hotmail.com

Dr. Jameela Al-MedanyAssociate Professor of AnatomyCollege of MedicineKing Saud University

OBJECTIVESAt the end of the lecture, students should: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.

PARTS OF LARGE INTESTINECECUMAPPENDIXASCENDING COLONTRANSVERSE COLONDESCENDING COLONSIGMOID COLON RECTUMANAL CANAL

ABDOMEN

PELVIS

PERINEUM

Abdomen

Pelvis

Perineum

CHARACTERISTICS OF COLON(NOT FOUND IN RECTUM & ANAL CANAL)1. Teniae coli: 3 longitudinal muscle bands2. Sacculations (haustra): teniae coli are

shorter than large intestine3. Epiploic Appendices : short peritoneal fold

filled with fat

PERITONEAL COVERINGPARTS WITH MESENTERY:1. Transverse colon2. Sigmoid colon3. Appendix4. CecumRETROPERITONEAL

PARTS:1. Ascending colon2. Descending colon

PERITONEAL COVERING

RETROPERITONEAL PARTS3. Upper 2/3 of rectumPARTS DEVOID OF

PERITONEAL COVERING:1. Lower 1/3 of rectum2. Anal canal

Rectum

Analcanal

SURFACE ANATOMY

ASIS1/3

2/3McBurney’s point

Right hypochondrium Left hypochondriumEpigastrium

Hypogastrium

Umbilical regionRight lumbar region Left lumbar region

Left iliac fossaRight iliac fossa

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

Positions:1.Retrocecal: most common 2.Pelvic3.Subcecal4.Preilieal5.Postileal: least common

(5)

(3)

(1)

(4)

(2)

RELATION BETWEEN EMBRYOLOGICAL ORIGIN & NERVE SUPPLY

Origin: Midgut (endoderm)Nerve: Autonomic: Sympathetic + vagus

Origin: Hindgut (endoderm)Nerve: Autonomic: Sympathetic + pelvic splanchnic nerves

Right 2/3Left 1/3

Origin: ectodermNerve: Somatic: inferior rectal

Lower part of anal canal

RELATION BETWEEN EMBRYOLOGICAL ORIGIN OF GUT & ITS ARTERIAL SUPPLY

CECUM – ASCENDING & DESCENDING COLONS (ANTERIOR RELATIONS)

Coils of small intestineGreater omentum

Anterior abdominal wall

CECUM – ASCENDING & DESCENDING COLONS (POSTERIOR RELATIONSCecum:1. Psoas major2. IliacusAscending colon:1. Iliacus2. Quadratus lumborumDescending colon:1. Left kidney2. Quadratus lumborum3. Iliacus4. Psoas major

Quadratus lumborum

RALATIONS OF TRANSVERSE COLONAnterior: greater omentum, anterior abdominal wall Superior: liver, gall bladder, stomach

Inferior: coils of small intestine Posterior: 2nd part of duodenum, pancreas

COLIC FLEXURES

RECTUMBeginning: 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)

RELATIONS OF RECTUM IN PELVIS

MALE PELVISAnterior: seminal vesicles, posterior surfaces of urinary bladder & prostate glandPosterior: sacrum & coccyx

FEMALE PELVISAnterior: posterior wall of vaginaPosterior: sacrum & coccyx

R R

QUESTION 1

Which one of the following is the most common position of appendix?

1. Subcecal2. Retrocecal3. Pelvic4. Preileal

QUESTION 2

Regarding the transverse colon, which one of the following statements is correct?

1. It is only supplied by the superior mesenteric artery.

2. It has no mesentery.3. It lies behind the pancreas.4. It contains taeniae coli in its wall.

THANK YOU