Gross anatomy of GI 2

Question 1

How is the gut tube held in the abdominal wall

Answer 1

Suspended by peritoneum in embryo
Attached along it length to the posterior abdominal wall via dorsal mesentery
Foregut attached to the anterior abdominal wall by ventral mesentery

Question 2

What are the derivatives of gut tube

Answer 2

oesophagus
stomach
small intestine
large intestine
rectum and anal canal
accessory organs

Question 3

What is the transpyloric plane

Answer 3

Lower border of L1 vertebrae

Question 4

Parts of the stomach

Answer 4

Fundus
Body
pyloric antrum
Pyloric canal

Question 5

What is the lesser omentum

Answer 5

Derived from ventral mesentery
Lesser curvature
subdivides into Hepatogastric lig. and Hepatoduodenal lig.
Has foregut arteries, portal vein and bile duct

Question 6

What is greater omentum

Answer 6

Peritoneal reflection derived from dorsal mesentery

Greater curvature

Question 7

4 parts of the duodenum

Answer 7

Superior
Descending
Inferior
Ascending

Question 8

Which parts of the duodenum are retroperitoneal

Answer 8

1st part is intraperitoneal

Rest are retroperitoneal

Question 9

What does the 2nd part of the duodenum contain

Answer 9

major duodenal papilla and minor duodenal papilla

Major duodenal papilla marks boundary between foregut and midgut

Question 10

What are the jejunum and ileum of small intestine

Answer 10

Intraperitoneal parts of the SI
Suspended by mesentery
Jejunum is the proximal 2/5 while ileum is the distal 3/5
Derived from the midgut

Question 11

What connects the SI and LI

Answer 11

Ileocaecal junction

Question 12

What is anal canal lined with

Answer 12

Upper part lined by mucosa similar to rectum
-has longitudinal folds = anal columns
-Form a circle around the anal canal called the pectinate line
-Inferior to this is an area called the anal
pectan
-This then ends at the anocutaneous

Question 13

What type of muscles are the anal sphincters made from

Answer 13

Internal anal sphincter
- smooth muscle

External anal sphincter
- skeletal muscle (deep, superficial and subcutaneous)

Question 14

What is the pelvic floor

Answer 14

Separates the pelvic cavity from the perineum below
Formed by muscle and fascia
Supports pelvic viscera and maintains closure of rectum and vagina

Question 15

What does the levator ani consist of

Answer 15

iliococcygeus
Pubococcygeus
Puborectalis
Urogenital hiatus anteriorly
Posteriorly forms anococcygeal ligament
Anal aperture posteriorly

Question 16

What is the perineal membrane

Answer 16

perineal membrane is a thick, triangular-shaped fascial sheet that fills the space between the pubic arches
Pelvic floor is supported anteriorly by perineal membrane
It has free posterior border
Contains the urethral hiatus and vaginal hiatus

Question 17

What is a deep perineal pouch

Answer 17

Deep perineal pouch is a narrow region superior to perineal membrane
Contains skeletal muscles
Act as sphincters for vaginal and urethral openings
Stabilise posterior edge perineal membrane

Question 18

What is the perineum (anatomically)

Answer 18

Diamond shaped structure
Subdivided by a theoretical transverse line drawn between the ischial tuberosities
-Anterior urogenital triangle
-Posterior anal triangle

Question 19

What does the anal triangle contain

Answer 19

Anal aperture
External anal sphincter
Ischioanal fossae (x2)

Question 20

What does the urogenital triangle contain

Answer 20

Urethral and vaginal openings
has perineal membrane - associated with a deep and superficial pouch
Roots of external genitalia

Question 21

What is the Perineal body

Answer 21

Fibrous connective tissue structure
Muscles of the pelvic floor and perineum attach to it
Positioned in the midline of the posterior border of the perineal membrane
Posterior end of urogenital hiatus formed by levator ani connect to it
Midway between ischial tuberosities and between the urogenital and anal triangles

Question 22

What are the specific blood supplies of each gut tube

Answer 22

Foregut - celiac artery
Midgut - superior mesenteric artery
Hindgut - inferior mesenteric artery

Question 23

What does foregut form

How does it form this

Answer 23

Stomach
it rotates 90 degrees clockwise
left wall grows faster giving the greater curvature
Ventral mesentery dragged to the right
dorsal mesentery moves to the left

Question 24

How is the greater omentum formed

Answer 24

Growth of mesentery on the greater curvature of the stomach in an inferior direction creates the greater omentum
hangs down and covers the small intestines
Initially 4 layers of peritoneum but posterior layer fuses with the mesentery of transverse colon

Question 25

What are the subdivisions of peritoneal cavity

Answer 25

Greater sac
Lesser sac
Connected by the omental or epiploic foramen

Question 26

Explain midgut rotation

Answer 26

Rapid elongation of the gut and its mesentery protrudes into the umbilical cord
Cranial and caudal limb in midline, one above the other
90 degree rotation anticlockwise
Jejunum and ileum elongate and coil
Caecal bud
Gut tube retracts back into abdomen and rotates another 180 degree
large intestine lengthens
Ascending and decending colon become retroperitoneal
Transverse colon retains its mesentery as the transverse mesocolon