GIT intro and peritoneum

The abdominal cavity extends from the _________ ______ to the ___________, and houses components of the __________ system, ________ system, ___________, and the _______

Inferior thoracic aperture, pelvic inlet, gastrointestinal, urinary, reproductive, spleen

Major elements of the gastrointestinal (GI) system that are considered abdominal viscera include… (7)

1. Caudal end of the esophagus

2. Stomach

3. Small intestines (duodenum, jejunum, ilium)

4. Large intestines (ascending, transverse, and descending parts are part of the abdominal viscera; sigmoid colon and anal canal are in pelvic cavity)

5. Liver

6. Pancreas

7. Gallbladder

Components of the urinary system included in the abdominal viscera include…(2)

1. Kidneys + suprarenal glands

2. Ureters

Name the structures of the path that food goes through, from the oral cavity to the anal canal.

Oral cavity → esophagus → stomach → small intestine (duodenum, jejunum, ilium) → large intestine/colon (ascending, transverse, descending, sigmoid) → rectum → anal canal

Define digestion

The process of turning food into nutrients your body can use

• In other words, mechanically and enzymatically breaking down food into substances for absorption into the bloodstream

T/F: Digestion starts as soon as food enters the mouth

True

Identify

1. Oral cavity

2. Esophagus

3. Stomach

4. Small intestine

5. Colon

6. Rectum

A. Liver

B. Gallbladder

C. Pancreas

D. Appendix

Initially (early development) the GIT is straight and suspended by ____________, which attaches to the _________ abdominal wall. The ___________ connects only the anterior stomach and the liver to the _________ abdominal wall

Dorsal mesentery, posterior, ventral mesentery, anterior

What happens to the GIT from fetus/baby to adult?

1. First, the stomach rotates 90° counterclockwise, bringing the posterior side to the left, and the anterior side to the right

2. The ventral mesentery forms the greater omentum

3. Further rotation of 180° distal to stomach

For the foregut:

1. What organs are part of it?

2. It is supplied by which artery/ies?

3. Which nerve(s) bring(s) parasympathetic innervation?

4. Which nerve(s) bring(s) sympathetic innervation?

1. Esophagus, stomach, pancreas, liver, gallbladder, proximal duodenum

2. Celiac trunk (left gastric, splenic, common hepatic arteries)

3. Vagus

4. Greater Splanchnic nerves (T5-T11)

For the midgut:

1. What organs are part of it?

2. It is supplied by which artery/ies?

3. Which nerve(s) bring(s) parasympathetic innervation?

4. Which nerve(s) bring(s) sympathetic innervation?

1. Everything between (rest of) duodenum and the proximal 2/3 of transverse colon

2. Superior Mesenteric Artery (SMA)

3. Vagus

4. Lesser and least splanchnic nerves (T11-12)

For the himdgut:

1. What organs are part of it?

2. It is supplied by which artery/ies?

3. Which nerve(s) bring(s) parasympathetic innervation?

4. Which nerve(s) bring(s) sympathetic innervation?

1. Distal 1/3 of transverse colon → anal canal

2. Inferior Mesenteric Artery (IMA)

3. S2-4 pelvic splanchnic nerves

4. Lumbar splanchnic nerves (L1-2)

The celiac trunk is found at level ___, and its major branches are…

T12

• Left Gastric Artery

• Splenic Artery

• Common hepatic Artery

The Superior Mesenteric Artery (SMA) is found at level ___ (~1cm inferior to the celiac trunk), it is located just superior to the __________ vein that crosses over the abdominal aorta; its major branches are…

L1, left renal

• Inferior pancreaticoduodenal artery

• Jejunal and ileal arteries

• Middle and right colic arteries

• Ileocolic arteries

The Inferior Mesenteric Artery (IMA) is found at level __, and its 3 major branches are…

L3

• Left colic artery

• Sigmoid arteries

• Superior rectal artery

The abdominal cavity is lined by a serous membrane (fluid secreting) called the __________ Describe it.

Peritoneum

• An epithelial-like single layer of cells (mesothelium) together with a supportive layer of connective tissue

• Serous membrane formed of simple cuboidal epithelium, rich in microvilli

• Similar to the pleura and serous pericardium in the thorax

What are the two layers of the peritoneum?

1. Parietal peritoneum: lines the abdominal wall

2. Visceral peritoneum: covers suspended organs

What’s found between the two layers of the peritoneum?

The peritoneal space → a minimal space that allows the two layers of the peritoneum to glide over one another (filled with serous fluid, 5-20 mL)

Identify

1. Transversalis fascia

2. Parietal peritoneum

3. Visceral peritoneum

4. Peritoneal cavity

5. Dorsal mesentery

What are mesenteries? What is their function?

• Double layers of elongated visceral peritoneum

• Provide a pathway for neurovasculature

• Connects intraperitoneal organs with posterior abdominal wall - also allows mobility for IP organs

• Storage for adipose tissue

What is the difference between dorsal and ventral mesenteries (location wise) ?

The dorsal (posterior) mesentery runs along the entire length of the system

The ventral (anterior) mesentery is only at the proximal regions of the gut tube

What are the three most important mesenteries?

1. Mesentery proper — small intestine

2. Mesocolon — colon

3. Mesoappendix — appendix

What are omentums? What are the two most important?

The are sheets (4 layers, or 2 double layers) of visceral peritoneum

• Greater omentum

• Lesser omentum

Identify

Greater omentum

Identify

1. Mesentery proper

2. Mesocolon

3. Greater omentum

Give characteristics of the greater omentum.

• Originates from greater curvature of stomach and proximal duodenum → runs inferiorly to distal end of abdominal cavity → wraps around itself → goes back up and attaches to transverse colon

• Thin, degenerated in elderly (sometimes absent)

• Big role in immunity → moves with movements of viscera, wraps itself around inflamed viscera, thereby protecting other organs

• Have many milky spots — contain immune cells that provide innate immunity

Give characteristics of the lesser omentum.

• Originates from the lesser curvature of stomach and proximal duodenum → attaches to liver

• Derived from mesogastrum

• Also called hepatogastric ligament → connects stomach to liver

• Associated with epiploic foramen and hepatoduodenal ligament

What is the hepatoduodenal ligament?

A thick, peritoneal fold that forms the right edge of the lesser omentum

• connects the liver to the proximal duodenum

• Is a surgical landmark for surgeons to access the livers blood supply

• Contains the portal triad : hepatic portal vein, hepatic artery proper, and bile duct

What is the epiploic foramen?

A right-sided passageway behind the hepatoduodenal ligament into the lesser sac, or omental bursa

• Also called Foramen of Winslow

What is the lesser sac / omental bursa?

A potential space posterior to the lesser omentum, and posterior to the liver and stomach

• Usually collapsed in healthy patients

What’s the function of the omental bursa?

To allow unrestricted movement of the stomach

• Can also act as a barrier to block pathological processes, but can also be a channel for disease spread

Identify

1. Gallbladder

2. Omental foramen

3. Duodenum

4. Ascending colon

5. Descending colon

6. Stomach

7. Lesser curvature

8. Lesser omentum

9. Liver

10. Lesser omentum (again)

11. Hepatoduodenal ligament

What are intraperitoneal vs retroperitoneal organs?

Intraperitoneal = enveloped by visceral peritoneum (anterior and posterior)

Retroperitoneal = visceral peritoneum only on anterior side, not suspended in mesentery, and lie between parietal peritoneum and posterior abdominal wall

What are the intraperitoneal organs?

SALTD SPRSS

• Stomach

• Appendix

• Liver

• Transverse colon

• Duodenum (1st part)

• Small intestine (jejunum and ileum)

• Pancreas (tail only)

• Rectum (upper 1/3)

• Spleen

• Sigmoid colon

What’s the difference between primary and secondary retroperitoneal organs?

Primary = developed and remained outside of the parietal peritoneum, never had a mesentery

Secondary = developed intraperitoneal with a mesentery, then migrated posterior to the parietal peritoneum

Why are secondary retroperitoneal organs surgically considered intraperitoneal?

Because the peritoneum is very thin

What are the retroperitoneal organs?

SAD PUCKER

• Suprarenal glands

• Aorta/IVC

• Duodenum (2 - 4th parts) — secondary

• Pancreas (except tail) — secondary

• Ureters

• Colon, ascending/descending — secondary

• Kidneys

• Esophagus (thoracic part)

• Rectum (distal 2/3)

The subperitoneal space is _______ to the peritoneum, and contains organs such as the _______, ____________, and _________

Inferior, bladder, distal rectum/anal canal, uterus (females)

Name some muscles of the retroperitoneal space?

Diaphragm, psoas major/minor, iliacus, quadratus lumborum