Small And Large Intestines Anatomy

Front 1

Defining the foregut, midgut and hindgut

Back 1

Foregut: esophagus, stomach, half of the duodenum

Midgut: most of the small intestine (second
half of the duodenum, jejunum and ileum)
and half of the large intestine (caecum,
appendix, ascending and transvsere colon)

Hindgut: Consists of the remainder of the transverse
colon, descending and sigmoid colon, rectum, part of
anal canal

Front 2

Arterial blood supply defines the foregut, midgut and hindgut

Back 2

The blood supply, venous drainage and innervation to the gut is delivered from the posterior abdominal wall via the mesentery

Front 3

Root of the Mesentery

Back 3

The root of the mesentery is 15 cm long. It suspends the jejunun and the ileum from the post abdominal wall

Front 4

Peritoneum covering retroperitoneal structures

Back 4

Front 5

Paracolic Gutters

Back 5

Paracolic gutters are important in flow of peritoneal fluid (and inflammatory material/cancer cells).
Greater absorption of peritoneal fluid by peritoneum in upper abdomen. Patients with intraperitoneal
infection are placed in inclined position  fluid gravitates to pelvic cavity where there is slower
absorption of toxins.

Front 6

Peritoneal Spaces

Back 6

Front 7

The Small Intestine

Back 7

Is the first part of the midgut. It consists of the second half of the duodenum, the jejunum and the ileum

Front 8

Duodenum – 4 parts

Back 8

The embryonic foregut ends at the 2nd part of the
duodenum (Ampulla of Varter where the the common bile duct joins the chief pancreatic duct). The midgut starts at 3rd and 4th parts of the duodenum because they are supplied by the superior mesenteric artery.

Front 9

DDx Jejunum and Ileum

Back 9

Front 10

DDx Jejunum and Ileum on X-ray

Back 10

Front 11

Meckel’s diverticulum:

Back 11

resembles the appendix
is usually within a metre of ileocaecal junction
inflammation may mimic pain of appendicitis
is the connection to the embryonic yolk sac

Front 12

Blood Supply to Small Intestine

Back 12

Front 13

The Large Intestine Structures

Back 13

Caecum, appendix, colon (ascending,
transverse, descending, and sigmoid),
rectum, first half of the anal canal

Ascending and descending colon are typically
retroperitoneal.

Front 14

The large Intestines;
Function

Back 14

Function: absorption of water & electrolytes, storage, elimination. Large intestine is 1.5 metres long,
extends from terminal ileum to anal canal

Front 15

Features that Distinguish the Colon

Back 15

The colon is characterised by…..
1. taeniae coli start at base of appendix and extend to rectosigmoid junction
2. haustrations (sacculatrae)
3. epiploic appendages (appendices epiploicae)

The colon also has a larger diameter than the small intestine but is shorter (1.5m)

Front 16

Caecum and Vermiform Appendix

Back 16

Caecum (L. blind) – 5-7cm long & wide, below level of ileocaecal valves. In contact with anterior abdominal
wall when full (distended with fluid/gas); taenia coli converge on base of appendix

Vermiform appendix – variable (3-15 cm), narrow, blind-ended tube; suspended by mesoappendix; supplied by an end artery. Inflamed appendix starts as vague peri-umbilical pain shifts to pain in R. iliac fossa.

Front 17

Ileocacal Valve

Back 17

makes like a flutter or farty sound when letting food through

Front 18

Colon - relations

Back 18

Front 19

Rectum

Back 19

Rectum from rectosigmoid junction (ant. to sacral segment 3) to anorectal jn (at pelvic diaphragm); located in pelvic cavity, anterior to sacrum & coccyx. Rectal ampulla is lower anterior dilatation.

No sacculations, appendices epiploicae or taeniae coli in rectum.

Front 20

Curvatures of the rectum

Back 20

Front 21

Rectum - Relationships

Back 21

Rectum has peritoneum on front & sides of upper 1/3rd, on front of middle 1/3rd and no peritoneum
related to lower 1/3rd. Peritoneum reflects from rectum onto pelvic viscera forming rectouterine pouch
in females & rectovesical pouch in males.

Anterior – coils of intestine + cervix, vagina (female) or
prostate, seminal vesicle (male) + vas deferens, bladder
Posterior – sacrum, coccyx
Lateral – coils of intestine (in pararectal fossa), pelvic
diaphragm

Front 22

Anal Canal

Back 22

Front 23

Importance of the Pectinate Line

Back 23

Front 24

Large Intestines BS

Back 24

Midgut supplied by superior mesenteric a; hindgut supplied by inferior mesenteric artery (to
pectinate line); rectal and anal canal walls also supplied by paired branches of internal iliac a.
(middle & inferior rectal aa)

Front 25

Anal Canal BS

Back 25

Front 26

Back 26

Front 27

Venous Drainage of Large Intestine

Back 27

Front 28

Barium Meal and Enema

Back 28