Anatomy: Development of small intestine/bowel/rectum and blood supply

Question 1

What part of the oesophagus is under voluntary motor control?

Answer 1

The upper 1/3rd (Somatic motor and sensory)

Question 2

What direction do muscle fibers of the oesophagus go?

Answer 2

They are perpendicular to constrictor fibers

Question 3

How long is the oesophagus?

Answer 3

10 inches from the pharynx to the stomach

Question 4

Where are the oesophageal narrowings located?

Answer 4

At cricoid cartilage

Where left bonrchus crosses

Oesophageal hiatus in the diaphragm.

Question 5

What is the shape of the oesophagus’ lumen under normal circumstances?

Answer 5

Mucous membrane is folded and collapsed

Question 6

What epithelium does the oesophagus have?

Answer 6

Stratified squamous epithelium

Question 7

What structures are located around the oesophagus?

Answer 7

Trachea on the right

Lower aorta on left

Medial to left lung behind the left atrium

Question 8

What causes hiatal hernias?

Answer 8

At the gastroesophageal junction there is usually fat and lots of elastic tissue blocking stomach and oesophagus from moving up into the thorax. In hiatal hernias the stomach and oesophagus protrude through the hiatus.

Question 9

What is the duodenum?

Answer 9

First 12 inches of the gut

Question 10

What are the 4 parts of the duodenum?

Answer 10

They form a C shape:

Duodenal cap (Radiologically identified, ulcers form here)

Descending part (Pancreatic and bile ducts)

Horizontal part (Crosses psoas, IVC, and aorta) (Crossed by mesentery superior mesenteric artery)

Ascending part

Question 11

What crosses the horizontal part of the duodenum?

Answer 11

Crosses psoas, IVC, and aorta (Passes anteriorly to these structures)

Crossed by mesentery and superior mesenteric artery (Passes posteriorly to these structures)

Question 12

What happens in the duodenal cap?

Answer 12

Radiologically identified and ulcers form here. It is mobile.

Question 13

What structures penetrate the duodenum at the descending part?

Answer 13

Pancreatic and bile ducts enter here

Question 14

Which parts of the duodenum are retroperitoneal?

Answer 14

The descending and horizontal part. (The duodenum is considered mostly retroperitoneal)

Question 15

Which part of the duodenum cradles the head of the pancreas?

Answer 15

The descending part

Question 16

Which part of the duodenum receives the hepatopancreatic ampulla?

Answer 16

The descending part

Question 17

Which part of the duodenum crosses posteriorly to superior mesenteric blood vessels? At what level of the spine does this occur?

Answer 17

Inferior part crosses posteriorly to the superior mesenteric blood vessels at the level of L3

Question 18

What is Meckel’s diverticulum?

Answer 18

A Meckel’s diverticulum, a true congenital diverticulum, is a slight bulge in the small intestine present at birth and a vestigial remnant of the omphalomesenteric duct (also called the vitelline duct or yolk stalk).

• Wikipedia definition

Connects umbilicus to intestine

Question 19

How is jejunum positioned in the peritoneum?

Answer 19

It is suspended by mesentery. (Supplied by superior mesenteric artery)

Question 20

How is the jejunum different to the ileum?

Answer 20

Larger in diameter

Thicker walls

Internally has mucosal folds that are higher and more numerous

Occupies left upper quadrant of the abdomen.

Ileum has Peyer’s patches (important for immune system)

Question 21

How is the mesentery of the jejunum different to the mesentery of the ilium?

Answer 21

Jejunal arteries anastomose forming 1 or 2 arcades with long vasa recta.

Ileal arteries anastomose forming 3 or 4 arcades with short vasa recta.

Question 22

What proportion of small intestine is jejunum?

Answer 22

2/5ths, transition to ileum is gradual.

Question 23

How does jejunum transition to ileum?

Answer 23

Gradually, there is an increase in the number of small villi, there is an increase in the number of lymph nodules, there are no submucosal glands, there are lacteals in each villus, and columnar epithelium

Question 24

What position of the appendix is most common?

Answer 24

Appendix tucked in behind caecum

Question 25

What causes appendicitis?

Answer 25

In older people: Obstruction by faecal matter

In younger people: Hyperplasia of lymphoid tissue

Question 26

How does appendicitis present?

Answer 26

Often first presents with vague pain in umbilical region = Dermatome of T10

Once inflammation spreads to the peritoneum then there is sharp pain in the right lower quadrant particularly over McBurney’s point.

Question 27

What is McBurney’s point?

Answer 27

McBurney’s point is the name given to the point over the right side of the abdomen that is one-third of the distance from the anterior superior iliac spine to the umbilicus (navel). This point roughly corresponds to the most common location of the base of the appendix where it is attached to the cecum.

Question 28

Where is the colon retroperitoneal?

Answer 28

On the ascending and descending parts.

Question 29

What flexures are present in the colon?

Answer 29

Right colic/hepatic

Left colic/splenic

Question 30

How does the transverse colon hang in the peritoneum?

Answer 30

Transverse mesocolon makes it intraperitoneal.

Question 31

What does the colon do?

Answer 31

Absorbs water and important ions from faeces

Compacts faeces for delivery to the rectum

Question 32

What are the important features of the colon?

Answer 32

Teniae coli

Haustra

Omental appendices (small fat accumulations that hang from colon)

Question 33

What are teniae coli?

Answer 33

3 longitudinal bands of smooth muscle on colon surface that assists in peristalsis

Question 34

What are haustra?

Answer 34

Sacculations of colon created by contracting teniae coli

Question 35

What are omental appendices?

Answer 35

Small fat accumulations that hang from colon

Question 36

What problem can haustra cause in older people?

Answer 36

Can be a site of food entrapment leading to irritable bowel syndrome

Question 37

Is the sigmoid colon intra or retroperitoneal?

Answer 37

Intraperitoneal suspended by the sigmoid mesocolon

Question 38

What is the uro-rectal septum?

Answer 38

Structure that divides the bladder and urogenital sinus from the rectum