1.02 - Lower GI Anatomy

Question 1

What composes the lower GI

Answer 1

Duodenojejunual junction, rectum and anus

Question 2

What vertebrae is duodenojejunal junction at

Answer 2

L1

Question 3

What marks the start of the Lower GI

Answer 3

Suspensory muscle of duodenum (Ligament of Treitz)

Question 4

What marks the end of ileum and start of caecum

Answer 4

L1

Question 5

What vertebrae level is caecum

Answer 5

L1

Question 6

What marks the start of jejunum

Answer 6

Duodenojejunal flexure

Question 7

What happens to musculature in ileocaceal valve

Answer 7

It thickens

Question 8

Describe the internal anatomy of the jejunum and ileum

Answer 8

Jejunum:
- plicae circularis more pronounced
- walls thicker
- wider diameter
- longer vasa recta
- fewer and larger arcades

Ileum:
- less plicae circularis
- walls thinner
- diameter smaller
- shorter vasa recta
- more and smaller arcades

Question 9

Location of ascending colon

Answer 9

• A retroperitoneal structure which ascends superiors from cecum
• Meets right lobe of liver

Question 10

What is Transverse colon

Answer 10

• extends from right colic flexure to spleen
• meets right lobe of liver
• at left colic flexure colon attached to diaphragm
• intraperitoneal

Question 11

What is descending colon

Answer 11

Inferior from pelvis
Retroperitoneal
Located anteriorly left to left kidney

Question 12

What is the sigmoid colon

Answer 12

Extends from left iliac fossa to S3
Attached to posterior pelvic wall by mesentry

Question 13

What are the characteristics of colon

Answer 13

Omental appendix
Teniae coli
Haustra

Question 14

What is the omental appendix

Answer 14

Small patches of peritoneum filled with fat

Question 15

What is teniae coli

Answer 15

3 bands of longitudinal smooth muscle
1. Mesocolic coli
2. Free coli
3. Omental coli

Question 16

What is haustra ‘

Answer 16

Teniae coli contract to shorten wall of bowel producing sacculation

Question 17

What is parabolic gutters

Answer 17

• 2 spaces between ascending/descending colon and posterolateral abdominal wall
• allow material been released from inflamed/infected abdominal organs elsewhere in abdomen

Question 18

What are the 2 flexure in abdomen

Answer 18

1. Sacral flexure
2. Peritoneal flexure

Question 19

What forms the valves in rectum

Answer 19

Mucosal Folds

Question 20

Are 1 and 3 valves in the rectum constant

Answer 20

YES

Question 21

Are the valves 2 and 4 constant

Answer 21

No

Question 22

What is a feature in the lower part of rectum

Answer 22

Temporary folds that disappear on distension

Question 23

Give importance of valves

Answer 23

• support weight of faeces
• prevent passage of instruments
• renal wash should be done in left lateral position -> prevent injury to 3rd valve

Question 24

What marks the junction of rectum and anal canal

Answer 24

Anorectal ring

Question 25

What makes the anorectal ring

Answer 25

Internal anal sphincter, external anal sphincter and puborectalis muscle

Question 26

What is internal anal sphincter

Answer 26

Thickening of involuntary circular smooth muscle in upper 2/3

Question 27

What is external sphincter

Answer 27

Voluntary muscle surrounding lower 2/3 of anal canal

Question 28

What divides the anal canal

Answer 28

Dentate/pectinate line

Question 29

Where are sinuses with mucus secreting glands in anal canal

Answer 29

Upper part where the anal canal joins by semi-lunar flaps called valves

Question 30

What is histology of duodenum

Answer 30

Only part of small intestine that has Brunner’s glands in submucosa

Question 31

What is Brunner’s gland

Answer 31

Secretes alkaline solution to neutralise acidic chyme Mucus also secreted to protect lining of intestinal walls

Question 32

What is histology of Jejunum

Answer 32

- most prominent with plicae circularis Villi lined with simple columnar epithelium - Crypts of Lieberkuhn

Question 33

What is histology of the ileum

Answer 33

Shortest villi - Mucosa has Peyner’s patches starting rom Lamina propia - Villi rich in goblet cells - crypt cells - villi lined by epithelial simple columnar

Question 34

What is histology of the large intestine

Answer 34

- no. Plicae circularis - epithelium -> simple columnar ciliated - straight glands - epithelium had goblet cells (mucus secretion) and brush cells (absorption of water) - presence of lymphoid aggregation

Question 35

What is the epithelium on rectum

Answer 35

Simple columnar epithelium

Question 36

What is the epithelium on anus

Answer 36

Stratified squamous non-keratinised epithelium after the dentate

Question 37

What happens to epithelium at the tip of anus

Answer 37

Stratified non-keratinised squamous becomes keratinised