GI Anatomy

Question 1

What is an aponeuroses?

Answer 1

The abdominal wall is formed from sheets of muscle and their corresponding sheets of tendon which we call aponeuroses.

Question 2

What is the function of the abdominal aponeuroses?

Answer 2

These muscles hold the abdominal viscera within the abdominal cavity and play an important part in respiration, coughing, sneezing, micturition, defecation and childbirth by contracting to increase intraabdominal pressure.

Question 3

What is the mechanism of a hernia?

Answer 3

Weaknesses in the muscle wall, or the aponeurosis, are common and may allow the bowel (or other organs) to protrude out of the abdomen, this is called a Hernia.

Question 4

What is the position of the rectus abdominis muscle?

Answer 4

Either side of the midline lies a pair of vertical muscles, the rectus abdominis muscles. They are attached to the sternum and costal margin superiorly and to the pubis inferiorly and are surrounded by the rectus sheath.

Question 5

What three muscles lie lateral to the rectus abdominis and what are their directions?

Answer 5

Lateral to the rectus sheath are three sheets of muscle which have fibres running in different directions; obliquely downwards and inwards (external oblique), obliquely upwards and inwards (internal oblique) and transversely (transversus abdominis).

Question 6

What forms the rectus sheath?

Answer 6

As these three muscle layers pass forwards towards the rectus sheath the muscles become aponeurotic and it is these aponeuroses that form the sheath for rectus abdominis.

Question 7

What are the attachments for the external oblique?

Answer 7

Inferiorly the lowest most extent of the external oblique muscle is aponeurotic throughout its length and is attached to the anterior superior iliac spine laterally and the pubic tubercle medially; this is the inguinal ligament.

Question 8

What lies immediately superior to the inguinal ligament?

Answer 8

Just above the inguinal ligament is the inguinal canal which, in the male, transmits all the structures to and from the testis, together these are the spermatic cord. Hernias often occur in this region

Question 9

What is the difference between a symptom and a sign?

Answer 9

a symptom is what the patient tells you is happening to them. A Sign is what the doctor finds by doing an examination.

Question 10

What are the bony landmarks for an abdominal examination?

Answer 10

1. Xiphisternum
2. Costal margin
3. Iliac Crest
4. Anterior Superior Iliac Spine
5. Pubic Tubercle
6. Pubic Symphysis

Question 11

What are the 9 regions of the abdomen?

Answer 11

From most superior to most inferior:

At the Midline: Epigastrium/Epigastric region
Lateral to Epigastrium: Left and Right hypochondrium

Inferior to epigastrium: Umbilicus
Lateral to umbilicus: Left and Right Flank

Inferior to Umbilicus: Hypogastrium/suprapubic
Lateral to Hypogastrium: Left and Right Iliac Fossa/ iliac region

Question 12

Describe the transpyloric plane of addison?

Answer 12

Transpyloric plane of Addison; this plane passes horizontally across the epigastrium and reaches the costal margin at the most lateral part of the rectus abdominis muscle. This is at the tip of the 9th costal cartilage and where the midclavicular line crosses the costal margin. The gall bladder, pancreas, pylorus of the stomach and duodeno-jejunal flexure all lie on this plane.

Question 13

Describe the subcostal plane?

Answer 13

this plane lies at the lowest points of the costal margin(bottom of the ribcage).

Question 14

What is McBurney’s Point?

Answer 14

this point lies 2/3 of the way along a line(diagonal line) joining the umbilicus to the right anterior superior iliac spine. It marks the usual site of the base of the appendix. It also gives a guide to the position of the caecum during clinical examination of the abdomen.

Question 15

What is the clinical significance of the umbilicus?

Answer 15

this variable and is often an unreliable landmark, it marks the point of insertion of the umbilical cord during embryonic life and (only in the thin recumbent patient) the level of the L3 vertebra.

Question 16

What is the intertubercular plane?

Answer 16

this is a plane which lies at the level of the tubercles of the iliac crests and marks the position of the bifurcation of the abdominal aorta.

Question 17

What is the intercristal plane?

Answer 17

this plane lies across the highest point of the pelvis, it cannot be felt with the patient lying on their back. It is used for examinations and procedures on the back whilst the intertubercular plane is used for the front

Question 18

What is unique about internal organ pain?

Answer 18

Pain arising from internal organs is felt as a poorly localised, diffuse sensation and can be felt somewhere other than where the organ lies

Question 19

Which nerve innervates the foregut and where is pain felt?

Answer 19

The foregut is supplied by the greater splanchnic nerve which arises from T5 to T9 spinal level and pain from the foregut is usually felt anteriorly, in the midline, at the T5-T9 dermatome level, i.e. in the epigastrium. We say that the pain is ‘referred’ to the epigastrium.

Question 20

Which nerve innervates the midgut and where is pain felt?

Answer 20

Midgut pain, supplied by the lesser splanchnic nerve (T10 and T11) is referred to the periumbilical area

Question 21

Which nerve innervates the hindgut and where is pain felt?

Answer 21

Hind gut pain (lowest splachnic nerve, T12) is referred to the suprapubic area

Question 22

When is pain from the appendix felt directly above the appendix?

Answer 22

The peritoneum covering the inside if the abdominal wall has the same sensory nerve supply as the skin overlying the same area of the abdominal wall. If a disease process involves the abdominal wall, such as an inflamed appendix the pain is felt very precisely directly over the appendix.

Question 23

How is irritation in the diaphragm felt as pain in the shoulder?

Answer 23

The under surface of the diaphragm is supplied by sensory nerves from the phrenic nerve (cervical 3,4,5 nerve roots) and diseases which irritate the diaphragm, such as cholecystitis (inflammation of the gall bladder), may be felt as referred pain in the C3, C4, C5 dermatome distribution; the pain is felt in the shoulder, despite the disease being in the abdomen (Phrenic C3, C4, C5 keep the diaphragm alive)

Question 24

What is the interrelationship between kidney and gonadal pain?

Answer 24

The sensory innervation of the kidney is via the sympathetic plexus which accompanies the renal artery (T10, 11, 12), the same plexus supplies the gonad.

Pain from the kidney can be referred along the cutaneous nerves of T10, 11, 12, most commonly T12, the pain is often described as radiating from the loin to the groin. Renal pain can also be felt in the gonadal area and conversely gonadal pain can be felt in the loin.

Question 25

What is the linea alba?

Answer 25

The aponeurosis passes in front of the rectus abdominis muscle to fuse with the aponeurosis of the opposite side in the linea alba (white line).

Question 26

What is the superior attachment of the external oblique?

Answer 26

On the lower lateral part of the thorax identify the muscular part of external oblique and follow it superiorly to where it interdigitates with serratus anterior above

Question 27

Where in the abdominal wall would one see the intercostal nerves?

Answer 27

running in the space between internal oblique and transversus abdominis

Question 28

Describe the rectus abdominus and the rectus sheath?

Answer 28

• Notice that the rectus abdominis muscles have tendinous intersections, these are firmly attached to the rectus sheath.
  
  • Note the number and position of the intersections
  • You may be able to identify the intercostal nerves as they enter the sheath from the lateral side and penetrate the muscle posteriorly.
  • Also identify the superior and inferior epigastric arteries on the posterior surface of the muscle. Immediately deep to the rectus abdominis muscle is the posterior rectus sheath and deep to that extraperitoneal fat, peritoneum and the abdominal cavity

Question 29

What is a typical history for appendicitis?

Answer 29

A typical history for appendicitis (inflammation of the appendix) is a vague central abdominal pain which after a few hours or days moves to the right iliac fossa and changes character. Pain from the appendix is relayed in the lesser splanchnic nerve via the sympathetic nervous system and results in a vague ‘dull’ central abdominal pain. However, when the inflammation extends to the surface of the appendix and this rubs on the inside of the abdominal wall the pain is relayed by cutaneous nerves and the pain is felt in the skin directly over the appendix and is described as being ‘sharp’.

Question 30

What is an aortic aneurysm and how does it relate to the abdomen?

Answer 30

An aortic aneurysm is an abnormal swelling of the aorta which can burst and lead to sudden death. Because the aorta only extends as far as intertubercular plane, an aortic aneurysm is only felt above this point (in the epigastrium down to the umbilicus).

Question 31

What is the presentation of shingles?

Answer 31

Shingles is an infection of sensory nerve cell bodies by the Herpes Zoster virus. The virus becomes dormant in the sensory dorsal root ganglia and can activate when the patient becomes ill. The virus reproduces and travels down the sensory nerve fibres to the skin where it produces a very itchy rash with small fluid filled blisters (vesicles). The fluid in the blisters is full of virus and when the patient scratches the virus is released to infect others. If the virus is in the T10 spinal nerve the rash will form as a ribbon from T10 vertebra at the back to the umbilicus at the front (the T10 dermatome).

Question 32

What is the upper extent of the abdominal cavity?

Answer 32

The costal margin

Question 33

Describe the nerve supply to the skin of the abdominal wall?

Answer 33

The peritoneum covering the inside if the abdominal wall has the same sensory nerve supply as the skin overlying the same area of the abdominal wall. abdominal wall pain is relayed by cutaneous nerves and the pain is felt in the skin

Question 34

What is the surface marking of the aortic bifurcation?

Answer 34

Intertubercular plane; this is a plane which lies at the level of the tubercles of the iliac crests and marks the position of the bifurcation of the abdominal aorta. L4

Question 35

Describe the anatomy of a six pack?

Answer 35

=The rectus abdominis muscle runs vertically from the pubis up to the costal margin. Along its length there are three places where it becomes a tendon. When exercised the muscle hypertrophies (becomes bigger) but the tendinous part stays the same. The result is three bulges (of muscle) between the tendons. This occurs on either side of the midline; six bulges in all.

Question 36

What is the name of the space behind the stomach?

Answer 36

The Lesser Sac

Question 37

What are intraperitoneal viscera?

Answer 37

(Intraperitoneal organs are enveloped by visceral peritoneum, which covers the organ both anteriorly and posteriorly. Examples include thestomach,liverandspleen

Question 38

What are retroperitoneal viscera?

Answer 38

Retroperitoneal organs are not associated with visceral peritoneum; they are only covered in parietal peritoneum, and that peritoneum only covers theiranterior surface.
They can be further subdivided into two groups based on their embryological development:
Primarily retroperitonealorgans developed and remain outside of the parietal peritoneum. Theoesophagus,rectumandkidneysare all primarily retroperitoneal.
Secondarily retroperitonealorgans were initially intraperitoneal, suspended by mesentery. Through the course of embryogenesis, they became retroperitoneal as their mesentery fused with the posterior abdominal wall. Thus, in adults, only their anterior surface is covered with peritoneum. Examples of secondarily retroperitoneal organs include the ascending and descendingcolon.

Question 39

What is the pneumonic for remembering which abdominal viscera are retroperitoneal?

Answer 39

A useful mnemonic to help in recalling which abdominal viscera are retroperitoneal isSAD PUCKER:
• S=Suprarenal(adrenal)Glands
• A=Aorta/IVC
• D=Duodenum(except the proximal 2cm, the duodenal cap)
• P=Pancreas(except the tail)
• U=Ureters
• C=Colon(ascending and descending parts)
• K=Kidneys
• E=(O)esophagus
• R=Rectum

Question 40

What is the parietal peritoneum?

Answer 40

Where the peritoneum covers the inside of the abdominal wall it is called the parietal peritoneum

Question 41

What is the visceral peritoneum?

Answer 41

Where it covers the viscera (bowel and mesentery) it is called the visceral peritoneum, this leaves a space (cavity) between the two layers which is the peritoneal cavity.
The distinction between parietal and visceral peritoneum is clinically very important because they have different nerve supplies and pain from each of them feels different and is felt in different places, this was studied last session

Question 42

What is ascites?

Answer 42

• The cells of the serosa (peritoneum) trap a layer of mucous between their microvilli allowing the viscera to slide freely. Fluid and pus may collect in recesses within the peritoneal cavity affecting adjacent structures and tumour cells may spread within the cavity.

Occasionally the cavity may become distended by fluid – ascites.

Question 43

Where would one find the urachus?

Answer 43

On the inside of the lower flaps, in the midline, try to identify a ligamentous structure extending from the dome of the bladder to the umbilicus; this is the urachus, and embryological remnant which may remain tubular and allow urine to flow out of the umbilicus

Question 44

Describe the course of the remnants of the paired umbilical arteries?

Answer 44

On either side there are two further ligamentous structures which are remnants of the paired umbilical arteries; these extend from the superior vesical artery (blood supply of the bladder) to the umbilicus.

Question 45

What would one find lateral to the remnants of the paired umbilical arteries?

Answer 45

identify the inferior epigastric artery and the deep inguinal ring lying lateral to it

Question 46

What may be identified on the right upper flap of the retracted abdominal wall?

Answer 46

On the right upper flap, find the falciform ligament and palpate the remnant of umbilical vein; the ligamentum teres in its free edge

Question 47

Where would you find and what is the left triangular ligament?

Answer 47

Put your hand over the left lobe of the liver and feel the attachment of the liver to the under surface of the diaphragm, this is a double layer of peritoneum called the left triangular ligament

Question 48

does the stomach lie deep or superficial to the left lobe of the liver?

Answer 48

Deep

Question 49

Can the left lobe of the liver be palpated transabdominally?

Answer 49

Notice that the entire left lobe of the liver is above the costal margin and cannot be palpated trans-abdominally.

Question 50

What lies on the inferior surface of the right lobe of the liver?

Answer 50

Gall bladder (stained green)

Question 51

Can the right lobe of the liver be palpated?

Answer 51

Notice that the inferior border of the right lobe of the liver runs parallel with the costal margin, on deep inspiration a normal right lobe of liver may just be palpable below the costal margin if the patient is slim

Question 52

What is the lesser omentum?

Answer 52

The lesser omentum is a thin fatty sheet of tissue containing blood vessels and nerves that attaches the lesser curvature of the stomach to the liver. The lesser omentum extends from the diaphragm, next to the oesophagus, down to the porta hepatis.

Find the anterior wall of the stomach and trace it upwards and to the right to find a thin fatty sheet of tissue containing blood vessels and nerves. This is the lesser omentum and attaches the lesser curvature of the stomach to the liver.
The lesser omentum extends from the diaphragm, next to the oesophagus, down to the porta hepatis.

• Note that the lesser omentum attaches to the first part of the duodenum and to the liver and the portal triad travels along the free edge of the omentum.

Question 53

What is the porta hepatis and where can it be palpated?

Answer 53

The porta hepatis is where two major blood vessels enter the liver, the portal vein and hepatic artery, and the bile leaves the liver in the bile duct.
These three structures together are the portal triad and run in the free edge of the lesser omentum.

Pass your fingers behind the free edge of the lesser omentum into the epiploic foramen (Foramen of Winslow) and palpate the portal triad (the vein is usually filled with clotted blood and feels hard).

Question 54

Describe the anatomical position of the spleen and can it normally be palpated?

Answer 54

• Notice that the spleen is well above the costal margin and cannot normally be palpated.
• The spleen is attached to the greater curvature of the stomach and to the posterior abdominal wall by folds of peritoneum forming part of the greater omentum.
• It is difficult to see the spleen fully in an intact abdomen

Question 55

What are the borders of the greater omentum?

Answer 55

• Look at the greater omentum, noting its extent and the amount of fat it contains. One edge of the greater omentum is attached to the greater curvature of the stomach and extends down in front of the rest of the bowel a variable distance.
• The other edge is attached to the under surface of the diaphragm and retro-peritoneum. Directly behind the stomach is another peritoneal space, the lesser Sac.

Question 56

What is the only way from the peritoneal sac to the lesser sac?

Answer 56

Through the epiploic foramen

Question 57

What structure is attached to the deep surface of the greater omentum?

Answer 57

The transverse colon

Question 58

What is the location of the duodenal-jejunal flexure?

Answer 58

just below the transverse colon mesentery

Question 59

Where is the ileocaecal junction?

Answer 59

In the right iliac region, where the terminal ileum curves upwards and forms the caecum

Question 60

Where is the appendix and where does its mesentery attach?

Answer 60

It is an appendage off the origin of the caecum and its mesentery attached to the lower part of the caecum.

The appendix arises from the base of the caecum at a fairly fixed position, whose surface marking is referred to as McBurney’s point, but its distal end may lie in a variety of positions within the abdomen or pelvis giving rise to a range of symptoms when it becomes inflamed and involves adjacent structures during appendicitis.

Question 61

What is the pathway from the pyloric sphincter to the rectum?

Answer 61

Duodenum, Duodenal-jejunal flexure, jejunum, ileum, ileocaecal junction, caecum, ascending colon, hepatic flexure, transverse colon, splenic flexure, descending colon, sigmoid colon, rectum

Question 62

What is the issue with infection in the abdomen?

Answer 62

Infection in the abdomen is common and can arise from a variety of sources; the appendix, gall bladder, uterine tudes or divirticular disease of the colon etc. Once bacteria are in the cavity they can spread rapidly and widely. They tend to ‘gravitate’ to the lowest place which is behind the right lobe of the liver when lying flat and into the pelvis when upright. Tumours may also spread through the cavity.

Question 63

What is the clinical significance of the semi-permeability of the peritoneum?

Answer 63

The peritoneum is semi-permeable which means that small molecules can pass freely in and out of the cavity whereas large molecules, such as protein, (normally) cannot. In patients with renal failure it may be possible to draw waste products from the blood into the peritoneal cavity and then drain them out of the cavity. This is the basis of peritoneal dialysis

Question 64

Explain the difference between fixed and mobile parts of the abdomen in terms of consequences of inflammation?

Answer 64

Mobile parts of the abdominal contains, such as the ileum or appendix, will move with movement of the body and breathing. Diseases which cause inflammation of the surface of these organs will cause pain on moving and breathing. Organs, such as the kidney, which are in a fixed position will not produce pain with movement.

Question 65

With the patient in a supine position, where might fluid collect in the abdomen?

Answer 65

Posterior to the liver

Question 66

What embryological structure forms the ligamentum teres?

Answer 66

Remnant of the umbilical vein

Question 67

Where does the base of the appendix lie (surface marking and internally)?

Answer 67

Thebase of the appendix islocated 2 cm beneath the ileocecal valve that separates the large intestine from the small intestine. Its position within the abdomen corresponds to a point on thesurfaceknown as McBurney’s point.

Question 68

Which parts of the bowel have a mesentery?

Answer 68

Mesentery proper- from small intestine (jejunum and ileum)toposterior abdominal wall (containssuperior mesenteric artery, autonomic nerve plexuses, lymphatics, fat)
Transverse mesocolon- transverse colon -> posterior abdominal wall(middle colic artery)
Sigmoid mesocolon- sigmoid colon -> pelvic wall(sigmoid arteries,superior rectal artery)
Mesoappendix- mesentery of ileum ->appendix(appendicular artery)

Question 69

What is the greater omentum?

Answer 69

The greater omentum is similar but note that one edge of the greater omentum is attached to the greater curvature of the stomach and extends down in front of the rest of the bowel a variable distance. The other edge is attached to the under surface of the diaphragm and retro-peritoneum. The spleen is attached to the greater curvature of the stomach and to the posterior abdominal wall by folds of peritoneum forming part of the greater omentum.

Question 70

What structures lie behind the lesser sac?

Answer 70

lesser sac the pancreas, splenic artery and part of the duodenum, these are collectively referred to as the gastric bed.

Question 71

What is the issue with tumours in the stomach?

Answer 71

Tumours of the stomach are relatively common and may spread via lymphatics to the nodes surrounding the coeliac axis or via veins to the liver

Question 72

What is the Coeliac Trunk?

Answer 72

The Coeliac trunk is the artery to the fore gut; it branches off the front of the aorta just below the diaphragm and supplies from the lower third of the oesophagus to the 2nd part of the duodenum.
The liver and part of the pancreas develop from the fore gut and are also supplied by branches of the coeliac trunk.

Question 73

Where does venous blood drain into to travel to the liver?

Answer 73

Portal vein

Question 74

What innervation does the foregut receive?

Answer 74

The fore gut receives a sympathetic nerve supply from the greater splanchnic nerve (T5-T9) and a parasympathetic nerve supply from the vagal trunks (X cranial nerve).

Question 75

Where would one find the pyloric sphincter?

Answer 75

At the junction between the pylorus of the stomach and the duodenum

Question 76

What are the regions of the stomach?

Answer 76

The fundus, the body, the antrum, and the pyloric region

Question 77

Where do the branches of the anterior vagal trunk travel to supply the stomach?

Answer 77

Look for the branches of the anterior vagal trunk supplying the stomach in the region of the lesser curvature.

Question 78

What are the branches of right common hepatic artery?

Answer 78

• The hepatic artery has been dissected, trace it downwards to just behind the pylorus and first part of the duodenum and demonstrate that it arises from the common hepatic artery.
You will also find a branch passing behind the first part of the duodenum, the gastroduodenal artery. There is one other branch, the right gastric artery, and its branches, which runs along the lesser curvature of the stomach.

Question 79

What is the path of the left gastric artery?

Answer 79

On the right side of the abdominal oesophagus find the left gastric artery and follow it back to its origin from the coeliac trunk (axis). It gives a branch to the lower 1/3 of the oesophagus and then runs along the lesser curvature of the stomach to meet the right gastric artery running from the opposite end of the lesser curvature.

Question 80

Where does the right gastro-epiploic supply and where does it come from?

Answer 80

right gastro-epiploic artery where it branches from the gastroduodenal artery inferior to the pylorus.
• Trace the artery to the left and demonstrate it anastomoses with the left gastro-epiploic artery, a branch from the splenic artery.
It supplies the omentum

Question 81

Where would one find the short gastric arteries?

Answer 81

In the region of the fundus look for some short gastric arteries arising from the splenic artery

Question 82

Describe the extent of the lesser sac?

Answer 82

it is bound by the greater omentum from the greater curve of the stomach, the lesser omentum from the lesser curve of the stomach and the caudate lobe of the liver. Immediately behind the lesser sac lies the pancreas inferiorly and the diaphragm superiorly.

Question 83

What structures are visible in the lumen of the stomach?

Answer 83

lumen of the stomach to study the folds of mucous membrane in its interior; the rugae

Question 84

Explain what happens to the veins around the liver during cirrhosis?

Answer 84

Veins in the lower third of the oesophagus usually drain to the portal vein but they also join with veins in the chest which drain to the superior vena cava. In disease of the liver, eg. Cirrhosis, the portal venous channels in the liver become progressively smaller until they are insufficient for normal blood flow. The venous blood from the bowel will then flow up the veins of the oesophagus and into the superior vena cava, a porto-systemic shunt. The veins in the oesophagus distend to form oesophageal varices; varicose veins of the oesophagus which bleed easily

Question 85

Describe Pyloric stenosis in children?

Answer 85

Some children, in the first six weeks of life, over develop the pyloric sphincter and the stomach cannot empty into the duodenum (pyloric stenosis). After feeding, when the stomach contracts, food it forced out of the mouth, projectile vomiting. Because the child is not getting any nutrition they are always hungry and eager to feed

Question 86

How can a peptic ulcer cause brisk bleeding?

Answer 86

A common site for peptic ulcer is the posterior wall of the first part of the duodenum. If the ulcer erodes through the duodenal wall it may erode into the gastroduodenal artery and cause very brisk bleeding.

Question 87

At what vertebral level does the oesophagus pass through the diaphragm?

Answer 87

T10

Question 88

Which structure(s) passes through the diaphragm alongside the oesophagus?

Answer 88

The vagal trunks, inferior oesophageal artery and vein

Question 89

What structure attaches the stomach to the liver?

Answer 89

The Lesser Omentum

Question 90

Which structures lie in front of the stomach?

Answer 90

Left lobe of the liver, anterior abdominal wall

Question 91

Which structures lie behind the stomach?

Answer 91

Behind the stomach lies the lesser sac and behind the lesser sac the pancreas, splenic artery and part of the duodenum, these are collectively referred to as the gastric bed

Question 92

What is a porto-systemic anastomosis?

Answer 92

It is a vein which joins to the hepatic portal system (so can carry blood to the liver) to the systemic system. It can take blood from the bowel and bypass the liver to return the blood to the heart

Question 93

Is the duodenum mobile?

Answer 93

No it is fixed and constant

Question 94

Which parts of the small bowel are mobile and what issues arise from this?

Answer 94

The rest of the small intestine, the jejunum and ileum, is attached to the posterior of the abdomen by a mesentery and is relatively mobile. This means that this part of the bowel is often involved in hernias and can become twisted (volvulus).

Question 95

In what ways is the small intestine specialised for nutrient absorption?

Answer 95

The small bowel is the organ of nutrient absorption and needs a high surface area; it is long, the mucosa has multiple mucosal folds (plicae circulares), there are villi on the mucosal folds and microvilli on each individual epithelial cell.

Question 96

Where are plicae circularis more pronounced?

Answer 96

Plicae circularis are more pronounced in the jejunum than the ileum

Question 97

What are Peyer’s Patches and where are they present?

Answer 97

The ileum has large submucosal lymph nodules known as Peyer’s patches.

Question 98

Which food stuff is deposited more at the ileal end of the small intestine?

Answer 98

Lipids are deposited in the small bowel mesentery in increasing amounts towards the ileal end

Question 99

What is Meckel’s Diverticulum?

Answer 99

Occasionally the ileum bears a blind-ended diverticulum about 1 meter from its termination (Meckel’s diverticulum) this is an embryonic remnant of the attachment of the mid gut loop to the yolk sac.

Question 100

What is the artery to the midgut?

Answer 100

The artery to the mid-gut is the superior mesenteric artery, it is a branch off the front of the aorta just below the coelic trunk and supplies from the 3rd part of the duodenum to two thirds of the way along the transverse colon

Question 101

Where would one find the arterial arcades and vasa rectae?

Answer 101

Remove the peritoneum from the upper surface of the mesentery and define the arterial arcades and vasa rectae.

Trace the arterial arcades back to the main trunk of the superior mesenteric artery where it runs over the third part of the duodenum, at the base of the transverse colon mesentery.

Compare the arterial arcades in the upper jejunum and lower ileum (and to the caecum and right colon).

Note that the arteries have accompanying veins, trace these upwards to where they pass over the third part of the duodenum, here they pass through the pancreas, join the splenic vein to form the portal vein, and pass onto the liver

Question 102

What lies to the right of the main superior mesenteric artery, what are the branches?

Answer 102

to the right of the main superior mesenteric artery there are branches to the colon; the ileo-colic, right colic and middle colic branches, dissect these out, they often anastomose with each other close to the colonic wall.

Question 103

What is the positioning of the large bowel?

Answer 103

It alternates between a retroperitoneal and a mesenteric disposition; the ascending and descending colon are normally retroperitoneal, the transverse and sigmoid colon lie on a mesentery.

Question 104

Describe the outer surface of the large intestine?

Answer 104

The outer, longitudinal, muscle layer forms three bands, the taenia coli, which start at the base of the appendix, run the length of the colon and then broaden out and fuse to form a continuous layer at the recto sigmoid junction.

Between the longitudinal taenia coli the circular inner layer bulges repeatedly between them to form characteristic ‘sacculations’.

Away from the mesentery there are two rows of ear-like pads of fat; known as appendices epiploicae, these mark where the blood vessels penetrate the muscles of the bowel wall to supply the mucosa and sub mucosa.

Question 105

Does the Caecum have a mesentery?

Answer 105

No

Question 106

Which artery supplies the hindgut?

Answer 106

The hind gut extends from the distal third of the transverse colon to one third of the way down the anal canal and is supplied by the inferior mesenteric artery which arises from the lower aorta just above the bifurcation

Question 107

Where is the aortic bifurcation?

Answer 107

its bifurcation just above the sacral promontory

Question 108

What is the root of the inferior mesenteric artery and what does the inferior mesenteric arterty supply?

Answer 108

Follow the aorta cephalid and approximately 2-3cm above the bifurcation find the inferior mesenteric artery branching off the anterior wall and running caudally and to the left towards the left iliac fossa. Dissect the inferior mesenteric artery from the surrounding adipose tissue and follow its branches forming arcades which supply the sigmoid colon and the superior rectal artery which enters the pelvis to supply the rectum and upper anal canal.

Question 109

What is the pathway of the superior rectal artery?

Answer 109

• Notice that the superior rectal artery enters the pelvic cavity posterior to the rectum and lies in the mesorectum between the rectum and the sacrum.
  
  • Within the mesorectum it divides into three branches. The branches of the inferior mesenteric artery anastomose with each other and with a branch of the middle colic artery to form a vessel which runs along the wall of the colon, the marginal artery of Drummond.

Question 110

What is the path of the inferior mesenteric vein?

Answer 110

trace it to where it passes beneath the transverse colon mesentery; from here it passes upwards behind the pancreas to join the splenic vein

Question 111

Where is the ileocaecal orifice and the orifice of the appendix?

Answer 111

The ileocaecal orifice is the opening leading to the caecum from the ileum and the orifice of the appendix is the opening at the ileocaecal junction which leads to the appendix

Question 112

What is the risk of a carcinoma of the colon and rectum?

Answer 112

Carcinoma of the colon and rectum are common in the western world. They spread directly via the blood stream, through the portal circulation, to the liver but also through the lymph vessels to regional lymph nodes.

Question 113

What causes Meckel’s Diverticulum?

Answer 113

In embryology the yolk sac is attached to the bowel exactly half way along its length. In 2% of adults the connection persists as a diverticulum (blind tube) attached 2 feet from the ileo-caecal junction, it is often 2 inches long. Histologically it can contain gastric mucosa and is a site for peptic ulcers and causes abdominal pain. It is known as Meckel’s diverticulum.

Question 114

What can happen when bowel on the mesentery twists?

Answer 114

• Bowel which is on a mesentery may twist round on itself and cause blockage of the draining vein. The result is an increase in capillary hydrostatic pressure, fluid leakage into the tissue and eventually death of the tissue. It most commonly occurs in the sigmoid colon.

Question 115

Which vein drains blood from the colon and where does it flow to?

Answer 115

Inferior mesenteric vein drains into the splenic vein

Question 116

Where does lymph from the small bowel drain?

Answer 116

Into the cisterna chyli and to the thoracic duct

Question 117

Which foodstuffs are absorbed through the lymphatic system?

Answer 117

Lipids

Question 118

Where is the junction between the mid gut and the hind gut?

Answer 118

2/3 of the way along the transverse colon

Question 119

How do you distinguish a loop of large intestine from that of small intestine?

Answer 119

Large intestine has appendices epiploicae and tenia coli. The small bowel is centrally located and the colon round the sides

Question 120

Which part of the bowel is supplied by sacral nerves 2, 3 and 4?

Answer 120

The hind gut

Question 121

What are the branches of the coeliac trunk?

Answer 121

The coeliac trunk gives rise to three major branches; the left gastric artery which supplies the lesser curvature of the stomach and the lower third of the oesophagus; the common hepatic artery to the liver, gall bladder, stomach, first two parts of the duodenum and pancreas; and the splenic artery to the pancreas, stomach and spleen.

Question 122

Which part of the duodenum is not retroperitoneal?

Answer 122

only the duodenal cap (1st part) within the lesser omentum

Question 123

Where is the head and the tail of the pancreas?

Answer 123

The head of the pancreas lies in the curvature of the duodenum with the tail extending to the left to reach the hilum of the spleen.

Question 124

What is the involvement between the superior mesenteric artery and vein and the pancreas?

Answer 124

The superior mesenteric artery and vein pass between the head and the uncinate process of the pancreas and then anterior to the third part of the duodenum to enter the small bowl mesentery.

These vessels mark the axis of rotation of the mid gut during foetal development.

Question 125

What is the first anterior branch of the abdominal aorta?

Answer 125

The first anterior branch of the abdominal aorta is the coeliac trunk.

Question 126

Define the four parts of the duodenum?

Answer 126

The first part commences at the pylorus of the stomach and passes to the right and slightly upwards; at its highest point it becomes the second part, which passes down and slightly to the right, and finishes where the bile duct and pancreatic duct enters the duodenum. The third part starts at the common bile duct, passes down and to the left, and finishes where the superior mesenteric artery passes in front of the duodenum. The fourth part starts at the end of the third part and finishes where the bowel develops a mesentery, which by definition, is the duodenal-jejunal junction, it passes to the left and upwards.

Question 127

What are the four parts of the pancreas?

Answer 127

Head, neck, body, tail

Question 128

What may be found in the grove between the head of the pancreas and the duodenum?

Answer 128

In the grove between the head of the pancreas and the duodenum you may be able to identify the small inferior and superior pancreaticoduodenal vessels.

Question 129

Where would one find the duodenal papillae?

Answer 129

About halfway down the descending duodenum find the duodenal papillae

Question 130

Where is the origin of the hepatic portal vein?

Answer 130

find the hepatic portal vein and trace it downwards behind the neck of the pancreas to its origin; the confluence of the splenic and superior mesenteric veins.

Question 131

How may gall stones cause jaundice, liver failure and pancreatitis?

Answer 131

Small gall stones may pass down the cystic duct into the common bile duct. However, they may be too large to pass through the sphincter of Oddi. They may block the bile duct pancreatic duct or both. Blockage of the bile duct leads to the build-up of pigments in the blood and the patient becomes jaundiced (yellow), it progresses to liver failure. Blockage of the pancreatic duct will cause high pressure in the duct and digestive enzymes will leak out of the duct and start digesting the pancreas; pancreatitis. It is fatal in 10% of cases. Fortunately, a small knife can be passed down the endoscope to widen the sphincter and let the stone pass through

Question 132

What is a psuedocyst and how does it relate to pancreatitis?

Answer 132

In patients who survive pancreatitis the pancreas may leak fluid into the lesser sac. This will compress the stomach from behind and cause difficulty eating. It is known as a pseudocyst; a cyst is a fluid filled structure with an epithelial lining, this cyst has a mesothelial lining so it is a pseudocyst.

Question 133

Describe the effect of carcinoma of the head of the pancreas?

Answer 133

Carcinoma of the head of the pancreas can invade the bile duct or pancreatic duct and cause the same problems as gall stones described above. It can also grow round the portal vein stopping blood flow from the bowel to the liver, currently this situation is untreatable

Question 134

What structures might a tumour of the head of the pancreas involve?

Answer 134

The hepatic portal vein, bile duct or pancreatic duct

Question 135

What structures join to form the common bile duct and what is its course?

Answer 135

The common hepatic and cystic duct. The common bile duct runs in the free edge of the lesser omentum and behind the first part of the duodenum, onto the posterior of the pancreas where it enters the pancreas to run alongside the pancreatic duct before opening into the duodenum

Question 136

Where is the sphincter of Oddi located?

Answer 136

On the medial wall of the duodenum between the second and third parts

Question 137

Which artery lies behind the first part of the duodenum?

Answer 137

Gastroduodenal artery

Question 138

What lies between the pancreas and the stomach?

Answer 138

The lesser sac

Question 139

How many pancreatic ducts are there? What is the embryological significance?

Answer 139

Two; one from the ventral pancreatic bud and one from the dorsal pancreatic bud.

Question 140

Describe the 9 abdominal regions?

Answer 140

Divisions:
• For the purposes of clinical examination, the abdomen can be split into a
‘noughts-and-crosses’ board of 9 regions.
• The two longitudinal lines are the midclavicular lines.
• The upper horizontal line is the subcostal plane.
• The lower horizontal line is the inter-tubercular plane.

Right Hypochondrium:
Top right of the abdomen, the liver and gallbladder are located here.

Epigastrium: • Top central region, the stomach and left lobe of the liver are located here.
• Pain from foregut structures is referred to this region.

Left Hypochondrium:
Top left of the abdomen, the spleen is located here.

Right Flank: Right side of the abdomen. Pain from kidneys and ureters is often felt here.

Umbilical: • Central region, the majority of the small intestines are located here.
• Pain from midgut structures is referred to this region.

Left Flank: Left side of the abdomen. Pain from kidneys and ureters is often felt here.

Right Iliac Fossa:
Bottom right of the abdomen, the appendix is located here.

Suprapubic: • Bottom central region, the bladder is located here.
• Pain from hindgut structures is referred to this region.

Left Iliac Fossa: Bottom left of the abdomen, the sigmoid colon is located here.

Question 141

Describe the abdominal wall muscles?

Answer 141

External Oblique:
Most superficial lateral muscle layer. Fibres run ‘down and in’ from lateral to medial.

Internal Oblique: Second lateral muscle layer. Fibres run ‘up and in’ from lateral to medial.

Transversus Abdominis:
Deepest lateral muscle layer. Fibres run horizontally.

Rectus Abdominis:
• Central longitudinal muscle made of 4 quadrilateral-shaped sections on each side, separated by 3 ‘tendinous intersections’ horizontally and the
Linea Alba vertically.

The Rectus Sheath:
• The fascial covering of Rectus Abdominis is actually made of the sheet-like tendons (Aponeuroses) of the 3 lateral abdominal wall muscles.
• In the upper abdominal wall, the aponeurosis of the external oblique runs
in front of rectus abdominis, and the aponeurosis of transverses abdominis
runs behind it, whilst the aponeurosis of internal oblique splits into two
thinner halves with half passing in front and half behind.
• In the lower abdominal wall, all 3 aponeuroses pass in front of rectus
abdominis

Question 142

Describe the Splanchnic nerves?

Answer 142

Description:
• 3 large nerves (on each side) that originate from the sympathetic chain.
• Supply the peritoneal structures with sympathetic nerve supply and pain
sensation.

Referred Pain:
• Each part of the skin in supplied with pain fibres via a specific nerve root, e.g. the lateral shoulder area is supplied by C5, the nipples by T4, the umbilicus by T10, the medial knee by L3 etc.
• When pain is felt in parts of the gut, it is transmitted to the brain via the splanchnic nerves, which each take origin from specific nerve roots.
• Pain from the gut is poorly interpreted by the brain and not easily localised to its origin.
• Therefore, the brain interprets this pain as coming from the areas of skin
(‘dermatomes’) supplied by the nerve roots that contribute to the specific
splanchnic nerve transmitting the painful stimuli.

Greater Splanchnic Nerve:
• Originates from T5-T9 nerve roots. Supplies foregut structures.
• Pain from these structures is referred as poorly-localised pain in the epigastric region (T5-T9 dermatomes).

Lesser Splanchnic Nerve:
• Originates from T10-T11 nerve roots. Supplies midgut structures.
• Pain from these structures is referred as poorly-localised pain in the
umbilical region (T10-T11 dermatomes).

Least Splanchnic Nerve:
• Originates from T12 nerve root. Supplies hindgut structures.
• Pain from these structures is referred as poorly-localised pain in the
suprapubic region (T12 dermatome).

Question 143

Describe Visceral Peritoneum?

Answer 143

• Layer of very thin tissue that lies on the surface of the organs of the peritoneal cavity.
• Innervated by the splanchnic nerve of the whichever part of the gut it is on the surface of.

Question 144

Describe peritoneal peritoneum/parietal peritoneum?

Answer 144

Smooth, shiny layer of fibrous tissue that forms the lining of the peritoneal
cavity.
• Innervated by the thoracoabdominal nerves which also supply the overlying muscles and skin.
• Pain from the parietal peritoneal lining is well localised.

Question 145

What is the Transversalis

Fascia?

Answer 145

Deepest layer of fascia before reaching the peritoneum.

• Lies between the Transversus Abdominis and Parietal Peritoneum

Question 146

What is the ligamentum teres?

Answer 146

• Remnant of the umbilical vein which transmitted oxygenated blood from
the placenta to the foetus via the umbilical cord, and into the IVC through
the liver.
• In newborns, the umbilical vein (before it closes shortly after birth) can be
used for intravenous access if necessary.
• In adulthood, only serves to tether the liver to the anterior abdominal wall.
• In adulthood, in patients with increased intra-hepatic pressure (i.e. in
cirrhosis of the liver), the ligament teres can ‘re-open’ to allow passage of
blood (see ‘Caput Medusae’).

Question 147

What is the falciform ligament?

Answer 147

• Sheet-like ligament that runs vertically down the middle of the anterior liver
from the diaphragm to the Ligamentum Teres.
• Tethers the liver to the anterior abdominal wall

Question 148

What are the umbilical artery remnants?

Answer 148

• Visible on the interior face of the of the lower abdominal wall as two
diagonal structures running upwards from the iliac vessels to the umbilicus.
• Most of the artery on each side obliterates after birth and serves no
purpose, but the origin of the umbilical arteries near the internal iliac
arteries become part of the artery that supplies the bladder in the adult

Question 149

What is the urachus?

Answer 149

Remnant of a structure that used to drain the foetal bladder into the
umbilical cord in the foetus.
• No function in adulthood.

Question 150

What is the greater omentum?

Answer 150

Sheet of fatty, lymph-rich tissue that hangs like an apron from the greater
curvature of the stomach, covering the majority of the small and large
intestine.
• Will migrate and stick to areas of inflammation in the peritoneal cavity, e.g.
colonic cancer, colitis, appendicitis.

Question 151

What is the small bowel mesentery?

Answer 151

• Fan-shaped sheet of tissue that attaches to the posterior abdominal wall
and fans out to attach to the small intestine.
• At its origin on the posterior abdominal wall, it is only approx. 15 cm long,
but it fans out to attach to the entire small intestine (approx. 3-5 m long).
• Made of two layers of peritoneum stuck together, with blood vessels,
nerves and lymph trapped in between.

Question 152

What is the foregut, midgut, and hindgut?

Answer 152

Embryologically, the gut forms in three parts.
• The Foregut is from the oesophagus to the first half of the duodenum. This
also includes the stomach, liver, gallbladder, spleen and pancreas.
• The Midgut is from the second half of the duodenum to 2/3 of the way
along the transverse colon. This also includes the jejunum, ileum, caecum,
ascending colon and appendix.
• The Hindgut is from the distal 1/3 of the transverse colon to the rectum.
This also includes the descending and sigmoid colon.
• Each part has its own splanchnic nerve and its own arterial blood supply

Question 153

What is an appendicitis?

Answer 153

The characteristic pain from appendicitis helps to understand the innervation of the abdominal organs and peritoneum.
• The appendix is a midgut structure, so is innervated by the Lesser Splanchnic Nerve, which originates from the T10-T11 nerve roots.
• Pain from appendicitis is therefore referred to the umbilical region as a dull, vague, aching pain.
• When the appendix becomes very inflamed, or even bursts, it may come into contact with the parietal peritoneum.
• The parietal peritoneum is innervated by the same nerves that supply the skin, so when it is exposed to a painful stimulus (like inflammation from
appendicitis), it transmits the pain as sharp, well-localised pain over the specific site that is affected (in this case, the right iliac fossa).
• The typical presentation of appendicitis is several hours of dull, vague umbilical pain, which then seems to migrate to the right iliac fossa and become sharp and well-localised.

Foregut
• From the lower 1/3 of the oesophagus to the major duodenal papilla in the
duodenum.
• Also includes the stomach, liver, gallbladder, spleen and pancreas.
• Nerve Supply: Greater Splanchnic Nerve.
• Arterial Supply: Coeliac Trunk

Midgut
• From the major duodenal papilla in the duodenum to 2/3 of the way along
the transverse colon.
• Also includes the jejunum, ileum, caecum, appendix and ascending colon.
• Nerve Supply: Lesser Splanchnic Nerve.
• Arterial Supply: Superior Mesenteric Artery.

Hindgut
• From the distal 1/3 of the transverse colon to the rectum.
• Also includes the descending and sigmoid colon.
• Nerve Supply: Least Splanchnic Nerve.
• Arterial Supply: Inferior Mesenteric Artery

Question 154

Describe the blood supply, rugae and pyloric sphincter of the stomach?

Answer 154

Blood Supply
• Lesser Curvature:
• Left Gastric Artery (direct branch of Coeliac Trunk).
• Right Gastric Artery (branch of Common Hepatic Artery).
• Greater Curvature:
• Left Gastroepiploic Artery (branch of Splenic Artery).
• Right Gastroepiploic Artery (branch of Gastroduodenal Artery).
• Short Gastric Artery (branch of Splenic Artery).
Rugae • Folds of mucosa allowing for greater surface area for stretching of the
stomach to accommodate food.
Pyloric
Sphincter
• Strong circular sphincter that separates the stomach from the duodenum
and controls passage of partially-digested food into the duodenum.

Question 155

Describe the features of the small intestine?

Answer 155

Major Duodenal Papilla:
• Nipple-shaped lump on the inside of the duodenum where the common
bile duct and pancreatic duct open.
• Located half way along the duodenum, between the 2nd and 3rd parts.
• Marks the end of the foregut and start of the midgut.

Ampulla of Vater:
• Very small channel formed inside the Major Duodenal Papilla as the common bile duct and pancreatic duct merge, just before they release their
bile/juices into the duodenum.

Sphincter of Oddi:
• Sphincter that controls release of bile & pancreatic juices from the Ampulla of Vater into the duodenum.

Plicae Circularis: • Internal folds of mucosa that allow for greater surface area for absorption.
• Also known as Valvulae Conniventes.

Vasa Recta & Arcades:

• Vasa Recta: long straight blood vessels that extend along the mesentery
from the arcades towards the small intestine.
• Arcades: semicircles of anastomosing small arteries in the proximal mesentery that give rise to the vasa recta.

Blood Supply: • As the distal duodenum, jejunum and ileum are all midgut structures, they are all supplied by branches of the superior mesenteric artery.

Question 156

Compare the jejunum and the ileum?

Answer 156

Jejunum vs.
Ileum
• Location:
• Jejunum: mainly in the top-left of the abdominal cavity.
• Ileum: mainly in the bottom-right of the abdominal cavity.
• Walls:
• Jejunum: thicker wall and wider lumen.
• Ileum: thinner wall and thinner lumen.
• Plicae Circularis:
• Jejunum: more frequent and thicker.
• Ileum: less frequent and thinner.
• Vasa Recta & Arcades:
• Jejunum: longer vasa recta, fewer arterial arcades.
• Ileum: shorter vasa recta, more numerous & larger arterial arcades.
• Peyer’s Patches (lymph follicles):
• More numerous in the ileum.

Question 157

Describe the features of the large intestine?

Answer 157

Caecum:
• Largest, bulbous part of large intestine at the very start of the ascending
colon.
• The appendix protrudes from the external wall of the caecum inferiorly.

Haustral Folds:
• Equivalent to the Plicae Circularis of the small intestine.
• Folds of mucosa that divide the large intestine into individual sections
called ‘Haustra’.
• Spaced much further apart and don’t fully wrap around the circumference
of the intestine (which helps to differentiate them from Plicae Circularis).

Teniae Coli:
• 3 longitudinal bands of muscle that run the length of the large intestine up
to the sigmoid colon.
• Contractions of the these bands shorten the large intestine, playing a role
in peristalsis.

Epiploic Appendages:
• Small clumps of fat that hang from the teniae coli along the length of the
large intestine.
• Don’t seem to have a specific role, but do help in differentiating large from
small intestine.

Blood Supply:
• From caecum to 2/3 of the way along transverse colon: Superior
Mesenteric Artery (branches: ileocolic, right colic and middle colic).
• From 2/3 along transverse colon to rectum: Inferior Mesenteric Artery
(branches: left colic, sigmoid branches, superior rectal artery).

Question 158

Describe the lesser omentum?

Answer 158

Smaller sheet of fatty tissue that hangs from the lesser curvature of the stomach and extends to the liver.
• The Hepatic Artery Proper, Portal Vein and Common Bile Duct all travel along the right-side free edge of the lesser omentum to reach the liver.

Question 159

Describe the Lesser Sac?

Answer 159

Also known as the ‘Omental Bursa’.
• Small pocket of space hidden behind the stomach and underneath the
lesser omentum.
• Can be entered via the Foramen of Winslow (aka Epiploic Foramen).
• Formed due to twisting of the foregut during embryological development.