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LSS 2:Anatomy of the Abdomen, Pelvis & Perineum > The gut and peritoneal cavity > Flashcards

The gut and peritoneal cavity Flashcards

1
Q

What type of epithelium is the peritoneum?

A

Simple squamous epithelium – mesothelium

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2
Q

What is contained in the peritoneal cavity?

A

Nothing - there is only a small amount of fluid and it is a potential space

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3
Q

what are intra-abdominal organs suspended in?

A

Intra-abdominal organs are suspended in peritoneal reflections called mesenteries (a fold of the peritoneum which attaches the stomach, small intestine, pancreas, spleen, and other organs to the posterior wall of the abdomen.)

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4
Q

what is found under the thoracic cage just below the thoracic diaphragm?

A

Right

  • Liver
  • Gallbladder
  • Transverse colon

Left

  • stomach
  • spleen
  • transverse colon
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5
Q

what is found within the pelvic cavity just above the pelvic floor?

A
  • Sigmoid colon

- Rectum

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6
Q

where does the gut tube originate from and where is it suspended from?

A

Endoderm and splanchnic mesoderm.

-It is suspended from the posterior abdominal wall by a peritoneal fold – the dorsal mesentery

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7
Q

what are mesentries?

A

Peritoneal folds attaching viscera to the abdominal wall.

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8
Q

What do the peritoneal folds act as a conduit for?

A

Nerves, blood vessels, lymphatics that supply the viscera.

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9
Q

what is the difference between the visceral peritoneum and parietal peritoneum?

A

VISCERAL peritoneum – covering the suspended organs/ viscera

PARIETAL peritoneum – lines the abdominal wall.

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10
Q

What is the difference between intraperitoneal and retroperitoneal?

A

INTRAperitoneal – structures, e.g. most of small intestine, suspended from the abdominal wall by mesenteries.
RETROperitoneal – structures, e.g. kidneys and great vessels that lie between parietal peritoneum and abdominal wall.

The viscera are not actually within the peritoneal cavity.
Abdominal organs that are not surrounded by peritoneum (e.g. kidneys) are called retroperitoneal.

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11
Q

State three viscera that are secondarily retroperitoneal.

A
  • Duodenum (except the first part)
  • Pancreas (tail is INTRAperitoneal)
  • Colon (ascending and descending only)

These organs originally had a mesentery, then became secondarily retroperitoneal when the mesentery fused with the body wall

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12
Q

State viscera that were retroperitoneal from the start.

A
  • Kidneys & ureters
  • Suprarenal glands
  • Aorta/Inferior vena cava
  • Nerves: lumbar plexus, sympathetic trunk
  • Oesophagus
  • Rectum
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13
Q

What are the three divisions of the GI tract and what defines their borders?

A

Forgut – abdominal oesophagus – dueodenum at enttrance of common bile duct (Major duodenal papilla)
Midgut – Major duodenal papilla – 2/3rds along transverse colon
Hindgut – distal third of transverse colon to rectum.

FOREGUT – Distal 3rd of oesophagus to the 2nd part of the duodenum at the entrance of the bile duct (Major duodenal papilla). from the distal 1/3 of the oesophagus to the major duodenal papilla (entrance of the bile duct to the duodenum)

MIDGUT – 2nd part of the duodenum to two-thirds along transverse colon. 2nd part of the duodenum to 2/3 of the way along the transverse colon

HINDGUT – Distal third of transverse colon to the rectum. final 1/3 of the transverse colon to the rectum

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14
Q

what does each part of the GI tract have?

A

Each part of the GI tract has its own arterial supply, coeliac trunk, superior mesenteric artery and hindgut.

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15
Q

Which mesenteries suspend the different parts of the gut tube?

A

The entire gut tube is suspended by dorsal mesentery

The foregut is ALSO suspended by ventral mesentery

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16
Q

What does the ventral mesentery split into?

A

The foregut also has a ventral mesentery containing the liver, which splits it into the falciform ligament and the lesser omentum

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17
Q

How is the lesser sac (omental bursa) formed?

A

As the liver grows, it moves to the right while the dorsal mesentery and spleen move to the left. The original right side of the upper peritoneal cavity is now posterior – the lesser sac of the peritoneal cavity.

The liver moves right and the stomach and the spleen move left with the dorsal mesentery thus cutting off a space behind the stomach - the lesser sac

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18
Q

What is the lesser omentum?

A

Fold of peritoneum between the liver and the lesser curvature of the stomach.
The lesser omentum is part of the ventral foregut mesentery.

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19
Q

What is the greater omentum?

A

Lower part of the dorsal foregut mesentery extends down form the greater curvature of the stomach as the greater omentum anterior to the intestine. It lies like an apron in front of the intestines.

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20
Q

What are the dorsal and ventral mesogastria?

A

The mesentery that is joined to the stomach.

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21
Q

Why does the lesser omentum have a lower free border and what opening does that form?

A

Because it is formed by the ventral foregut mesentery, which ends at the start of the midgut. The opening to the omental bursa is called the epiploic foramen.

22
Q

What is the transverse colon suspended by?

A

Transverse mesocolon

23
Q

What vessels run within the lesser omentum near its free edge?

A

Hepatic portal vein, hepatic artery proper, bile duct run between the posterior abdominal wall and liver within the lesser omentum near its free edge. This free edge is present because the ventral mesentery ends at the start of the midgut..

24
Q

Describe how the abdomen is divided into different compartments.

A

The transverse mesocolon divides the abdomen into supracolic and infracolic compartments. The infracolic compartment is further divided by the mesentery of the small intestine (from the duodeno-jejunal flexure to the ileo-caecal valve) - dividing the infracolic compartment into right and left infracolic compartments.
There are also gutters running along the lateral sides of the ascending and descending colon called the right and left paracolic gutter.

25
Q

Describe how the direction of movement of peritoneal fluid differs from that of inflammatory exudate.

A

Peritoneal fluid moves towards the underside of the diaphragm
Inflammatory exudate moves towards the pelvis

26
Q

State the layers of the GI tract.

A

Mucosa, submucosa, muscularis, serosa/adventitia, mesentry.

27
Q

Which layers have nerve plexuses and what are they called?

A

Submucosa - Meissner’s plexus

Muscularis (myenteric) - Auerbach’s plexus

28
Q

At which vertebral position does the oesophagus penetrate the diaphragm and through which crus?

A

Distal oesophagus
T10 - through the right crus.

Pierces muscular part of diaphragm – contributes to LOWER OESOPHAGEAL SPHINCTER which prevents gastro-oesophageal reflux

29
Q

what prevents food entering duodenum?

A

A ring of smooth muscle at distal end of PYLORIC CANAL prevents food entering duodenum – PYLORIC SPHINCTER (palpable)

30
Q

What are the different parts of the stomach?

A
  • the cardia surrounding the openning
  • the fundus
  • the body
  • pyloric region consisting of pyloric antrum and pyloric canal (close to the duodenum) Pyloric canal contains pyloric sphincter which prevents food entering the duodenum
31
Q

What are the four parts of the duodenum?

A

Superior, descending, inferior, ascending
Superior is where the duodenal cap is located - this is a common location for duodenal ulcers

SECOND part of duodenum contains entrance for common bile duct – MAJOR DUODENAL PAPILLA
Most of the duodenum is RETROPERITONEAL.

Duodenum split into four parts:

Superior / first part – duodenal cap, common place for peptic ulcers. Passes anteriorly to bile duct, gastroduodenal artery, portal vein and IVC.

Descending / second part – contains minor and major duodenal pappillae where accessory pancreatic duct and bile duct enter respectively.

Inferior / third – part – crosses IVC and has SMA anterior to it.

Ascending / fourth part – terminates at duodenaojejunal flexure.

The relations of the duodenum are important clinically. Anurysms can compress the duodenum or ulcers can erode into the walls of vessels.

32
Q

What is the major duodenal papilla and where is it found?

A

The major duodenal papilla is the opening of the bile duct to the duodenum - it is in the descending part of the duodenum

33
Q

Describe three ways in which the jejunum and ileum differ.

A

Jejunum and ileum make up the rest of the small intestine and are intraperitoneal.

JEJUNUM:
Proximal two-fifths
Larger in diameter
Upper left quadrant of abdomen
Less prominent ARTERIAL ARCADES
Longer VASA RECTA
ILEUM:
Distal three-fifths
Smaller in diameter
Lower right quadrant of abdomen
Prominent ARTERIAL ARCADES
Shorter VASA RECTA
34
Q

Describe three ways in which the colon differs from the small intestines.

A

Colon has taenia coli (ribbons of longitudinal muscle)
Colon has fatty tags - appendices epiploicae
Colon has a segmental/pocketed arrangement

35
Q

what are the 3 main arteries supplying the gut?

A

3 UNPAIRED arteries arising from the anterior of the AORTA.

COELIAC TRUNK = FOREGUT, liver, pancreas and spleen. The coeliac trunk (or axis) supplies the entire foregut (lower oesophagus, stomach, upper duodenum) and its derivatives (liver and part of pancreas). The spleen, though not part of the alimentary system, shares its blood supply from the coeliac trunk.

SUPERIOR MESENTERIC ARTERY (SMA) = MIDGUT

INFERIOR MESENTERIC ARTERY (IMA) = HINDGUT

36
Q

What does the coeliac trunk divide into?

A

Common Hepatic Artery
Left Gastric Artery
Splenic Artery

37
Q

What are the branches of the superior mesenteric artery?

A 
Jejunal Arteries
Ileal Arteries 
Iliocolic Artery 
Right Colic Artery 
Middle Colic Artery
38
Q

What are the branches of the inferior mesenteric artery?

A
  • Left Colic Artery
  • Sigmoid Arteries
  • Superior Rectal Artery
39
Q

Describe the venous drainage of the gut.

A

The venous drainage does NOT follow the arterial supply. All the venous blood from the gut drains through the liver. The inferior mesenteric vein joins the splenic vein and the splenic vein then joins the superior mesenteric vein to form the hepatic portal vein. The superior mesenteric vein joins the splenic vein behind the first part of the duodenum.

40
Q

Where do you find portal-systemic anastamosis?

A

Oesophagus, rectum, umbilicus
Oesophagus: between oesophageal vein and left gastric vein
Umbilicus: between umbilical vein and epigastric veins
Rectum: between superior rectal vein and inferior rectal vein
NOTE: there is a fourth anastomosis between the colic veins and posterior abdominal wall veins

41
Q

where does the portal vein arise from

A

The portal vein arises from the superior mesenteric and splenic veins posterior to the 1st part of the duodenum / pylorus of the stomach. It then runs in the free edge of the lesser omentum to the liver. It drains blood from all abdominal viscera and liver

42
Q

where do all lymph drain into

A
  • All lymph drains into the cisterna chyli.
  • Cisterna chyli is an elongated lymphatic sac located in front of the L1 & L2 bodies
  • The thoracic duct commences from the cisterna chyli
43
Q

What is the clinical significance of the portal-systemic anastamoses?

A

If there is liver damage or a blockage then you get portal hypertension leading to dilation of the porto-systemic anastomoses, which could possibly lead to oesophageal or rectal haemorrhage.

44
Q

describe the innervation of the gut?

A

Abdominal viscera supplied by AUTONOMIC nervous system.

Sensory fibres most important
Parasympathetic sensory (regulate reflex gut function):
VAGUS NERVE
PELVIC SPLANCHNIC NERVES (S2-S4)

Sympathetic sensory (mediate PAIN):
THORACIC SPLANCHNIC (T5-T12)
Thoracic Splanchnic Ns.

Greater Splanchnic N. (T5-T9)

Lesser Splanchnic N. (T10-T11)

Least Splanchnic N. (T12)

Lumbar SPLANCHNIC (L1+L2)

In the viscera:
Sensory fibres running with the sympathetic (T1-L2) mediate pain
Sensory fibres running with the parasympathetic (vagus or sacral) are involved in reflex regulation of gut function

45
Q

Describe the lymphatic drainage of the gut.

A

The lymphatics follow the arteries. There are coeliac lymph nodes, superior mesenteric lymph nodes and inferior mesenteric lymph nodes. They all drain into the cysterna chyli and then through the thoracic duct.

46
Q

Which vertebral level is the cysterna chyli positioned at?

A

(in front of the vertebral body of) L1 and L2

47
Q

What are the main parasympathetic sensory nerves of the gut?

A

Vagus Nerve

Pelvic Splanchnic Nerves (S2-S4)

48
Q

What are the main sympathetic sensory nerves of the gut?

A

Thoracic Splanchnic Nerves (T5-T12)

Lumbar Splanchnic Nerves (L1+L2)

49
Q

What are the roles of the parasympathetic sensory and sympathetic sensory nerves of the gut?

A

Parasympathetic Sensory - involved in regulate reflex gut function
Sympathetic Sensory - mediate pain

50
Q

What are the three divisions of the thoracic splanchnic nerves?

A

Greater Thoracic Splanchnic - T5-T9
Lesser - T10-T11
Least - T12

51
Q

describe the control over gut motility and secretory activities?

A

Controlled by the ANS.
Parasympathetic efferents: increase peristalsis, relax sphincters, increase secretion.

Sympathetic efferents: decrease peristalsis, constrict sphincters, decrease blood flow and secretions

LSS 2:Anatomy of the Abdomen, Pelvis & Perineum (7 decks)

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