Session 13 - Lecture 1 - Revision

Question 1

1 - Visualiser 1

Answer 1

{GI embryology - embryo starts with gut tube running down middle of embryo - split into 3: foregut at the beginning; midgut; hindgut (has poo in it).

Divisions:

• between foregut and midgut is where the bile ducts (BD) insert – second part of the duodenum at the ampulla of Vater is where our BDs come in.
• between midgut and hindgut is 2/3 way along transverse colon.

Contents:
foregut = oesophagus, stomach and first part of duodenum
midgut = basically all of your small bowel and a little bit of your colon
hindgut = colon, rectum and a bit of anus.

Blood supply:
foregut = coeliac axis
midgut = superior mesenteric artery
hindgut = inferior mesenteric artery}

Question 2

1 - Visualiser 2

Answer 2

{Eddie the embryo also has a foregut midgut and hindgut.
So take cross-section in transverse plane of Eddie through foregut.

posterior = dorsal (like back, dorsal fin on shark) and anterior = ventral. L and R.

At v back/dorsal of embryo – beginnings of spinal cord and dorsal column – made of ectoderm (outer layer of 3 layers of embryo) - that’s your spine.
In the middle, there’s mesoderm, that sits round the back of your embryo still – made of mesoderm – become things like kidneys.
Mid of embryo is foregut tube – about the level of the stomach. And that’s all covered in layers of peritoneum peritoneum – which cover our foregut tube, covers over the back and a layer again the other side. Cavities are the peritoneal cavities at the level of the foregut – there’s 2, all the way.

Got some mesentery holding our foregut – 2 layers of peritoneum together – where our blood supply comes from. Dorsal mesentery at back and ventral mesentery. At point of foregut is other things develop in mesenteries – ventral mesentery you get dvlmpnt of the liver; dorsal mesentery dvlmpnt of the spleen.

So – peritoneal cavities – foregut at lvl of stomach and beginnings of development of liver and spleen. Doesn’t and can’t stay like that forever.}

Question 3

1 - Visualiser 3

Answer 3

{Cross-section of transverse plane of embryo at foregut.

• blue neuroectoderm
• orange mesoderm that will become kidneys
• foregut in middle – but drawn in slightly different plane (rotation) – what was A and P has rotated 90 degrees clockwise – stomach rotates.
• in dorsal mesentery we have the spleen – this is now enlarged a bit later on in foetal life
  – big liver that’s developed in ventral mesentery
  and that’s all still covered in mesentery

So when rotated it starts to look a bit more recognisable, maybe, and bits of dorsal and ventral mesentery have new names.

• Mesentery connecting with spleen and kidney – we call that a ligament. spleen = lieno; kidney = renal so lienorenal ligament (splenorenal ligament).
• dorsal mesentery between spleen and stomach – spleen = lieno; stomach = gastric – lienogastric ligament – within this become the short gastric vessels.
• ligament between stomach and liver – lesser omentum – in part of ventral mesentery
• bit of ventral mesentery between liver and anterior abdo wall = falciform ligament, which carries the umbilical vein.

So things that were just a strip of mesentery, but now theyre connecting actual organs have names}

Question 4

2

Answer 4

4

Question 5

3

Answer 5

5

Question 6

4

Answer 6

5

Question 7

5

Answer 7

5