GASTRO - 3

Development of the fore gut

*PHOTO COPY* -Only foregut that has attachment to anterior abdominal wall 1: Diverticuli (balloon-like projections) (from liver and spleen) grow out from gut tube 2: Splits dorsal and ventral mesogastrium 3: Liver grows quicker than others so runs out of space and moves right so stomach and spleen move left 4: Stomach rotates 90' so greater curvature moves left and left omentum moves right

Development of midgut

*PHOTOS COPY* 1: Yolk sac comes through umbilicus and provides nourishment for embryo 2: Forms viterline duct and connects placenta to mid gut 3: Herniates into umbilicus then returns when space (when returns rotates 270' anticlockwise around axis of superior mesoteric artery) 4: When gut tube (Previously viterline duct) returns back into embryo, forces some structures to posterior abdominal wall to which they fuse (retroperitoneal)

Mesentry

-Anchors bowel to posterior wall -Root of transverse mesocolon -Root of sigmoid mesocolon

Anal canal + Sphincters

-Continuation of large intestine -Inferior to rectum -Narrows at pelvic floor -Terminates at anus after passing through perineum -Multiple internal and external sphincters

Ileum

-Distal 3/5th = ileum (Thinner walls) -Fewer plicae circulares -Extensive arterial arcade -Short vesa ercta (BOTTOM DIAGRAM) -More mesenteric fat in ileum

What elongates but remains uncoiled in the midgut during development

-Distal ileum -Caecum -Appendix -Ascending colon -Proximal 2/3rds of transverse colon

Duodenum

-Duodenal cap -4 parts -Intraperitoneal -Anterior to liver and attached to liver -Where bile and pancreatic duct open -Parts 2, 3 and 4 plastered to posterior abdominal wall -Retroperitoneal -Above 2 = foregut -Below 2 = mid gut

Anatomy of stomach

-Fundus (air filled) -Body -Pyloric antrum -Pyloric canal -Cardia -Lesser and greater curvature

Peritoneum related to stomach

-Large sheet (greater omentum) hanging from greater curvature -Smaller sheer (lesser omentum) hanging from lesser curvature (Connects stomach to liver (+hepatogastric and hepatoduodenal ligaments))

Extraperitoneal

-Lie outside peritoneum -Fat (Not organs)

Retroperitoneal

-Organ behind peritoneum/only partially covered

Intraperitoneal

-Organ completely covered with visceral peritoneum -Organs attached to each other or to abdominal wall by peritoneal folds (Mesentry)

Jejunum

-Proximal 2/5ths = jejunum -Larger diameter -More prominant plicae circulares (circular folds of muscle) and less prominant arterial arcades and longer vesa recta (TOP DIAGRAM)

General anatomy (route) of the lower digestive tract

-Stomach -Spleen -Duodenum -Jejenum -Ileum -Appendix -Caecum -Ascending colon -Right colic flexure -Transverse colon -Left colic flexure -Descending colon -Sigmoid colon -Rectum

Peritoneum

-Thin serous membrane lining of abdominal pelvic cavities --Perital peritoneum: lines the wall of th abdominal and pelvic cavities --Visceral peritoneum: lines organs and viscera

Lining of anal canal

-Upper mucosa: >Similar to rectum (longitudinal folds and columns) >Columns unite = anal valves >Sinus secretes fluid allowing faeces to move through without damage >Valves form pectinate line - -Lower mucosa >Below pectinate line >Lined by non keratinised stratified squamous epithelium

Taeniae coli

Band of longitudinal muscle, runs across anterior and posterior surface

Omental appendices

Fatty appendices -Pouches of peritoneum filled with fat

How does SI become LI

Ileum > Caecum (Ileocaecum joint) +Mobile Appendix

Space between peritoneum

Peritoneal cavity: -Potential space -Contains fluid -'Closed in males' -Communication with exterior via the vagina, uterus and uterine tubes in females

Haustra

Pinched appearance

Where s the cut off point of the mid gut

Proximal 2/3rds of transverse colon

SMA

Superior mesenteric Artery