GI Anatomy Flashcards
1
Q
What is an aponeuroses?
A
The abdominal wall is formed from sheets of muscle and their corresponding sheets of tendon which we call aponeuroses.
2
Q
What is the function of the abdominal aponeuroses?
A
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.
3
Q
What is the mechanism of a hernia?
A
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.
4
Q
What is the position of the rectus abdominis muscle?
A
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.
5
Q
What three muscles lie lateral to the rectus abdominis and what are their directions?
A
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).
6
Q
What forms the rectus sheath?
A
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.
7
Q
What are the attachments for the external oblique?
A
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.
8
Q
What lies immediately superior to the inguinal ligament?
A
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
9
Q
What is the difference between a symptom and a sign?
A
a symptom is what the patient tells you is happening to them. A Sign is what the doctor finds by doing an examination.
10
Q
What are the bony landmarks for an abdominal examination?
A
- Xiphisternum
- Costal margin
- Iliac Crest
- Anterior Superior Iliac Spine
- Pubic Tubercle
- Pubic Symphysis
11
Q
What are the 9 regions of the abdomen?
A
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
12
Q
Describe the transpyloric plane of addison?
A
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.
13
Q
Describe the subcostal plane?
A
this plane lies at the lowest points of the costal margin(bottom of the ribcage).
14
Q
What is McBurney’s Point?
A
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.
15
Q
What is the clinical significance of the umbilicus?
A
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.
16
Q
What is the intertubercular plane?
A
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.
17
Q
What is the intercristal plane?
A
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
18
Q
What is unique about internal organ pain?
A
Pain arising from internal organs is felt as a poorly localised, diffuse sensation and can be felt somewhere other than where the organ lies
19
Q
Which nerve innervates the foregut and where is pain felt?
A
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.
20
Q
Which nerve innervates the midgut and where is pain felt?
A
Midgut pain, supplied by the lesser splanchnic nerve (T10 and T11) is referred to the periumbilical area
21
Q
Which nerve innervates the hindgut and where is pain felt?
A
Hind gut pain (lowest splachnic nerve, T12) is referred to the suprapubic area
22
Q
When is pain from the appendix felt directly above the appendix?
A
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.
23
Q
How is irritation in the diaphragm felt as pain in the shoulder?
A
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)
24
Q
What is the interrelationship between kidney and gonadal pain?
A
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.
25
What is the linea alba?
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).
26
What is the superior attachment of the external oblique?
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
27
Where in the abdominal wall would one see the intercostal nerves?
running in the space between internal oblique and transversus abdominis
28
Describe the rectus abdominus and the rectus sheath?
* 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
29
What is a typical history for appendicitis?
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’.
30
What is an aortic aneurysm and how does it relate to the abdomen?
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).
31
What is the presentation of shingles?
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).
32
What is the upper extent of the abdominal cavity?
The costal margin
33
Describe the nerve supply to the skin of the abdominal wall?
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
34
What is the surface marking of the aortic bifurcation?
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
35
Describe the anatomy of a six pack?
=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.
36
What is the name of the space behind the stomach?
The Lesser Sac
37
What are intraperitoneal viscera?
(Intraperitoneal organs are enveloped by visceral peritoneum, which covers the organ both anteriorly and posteriorly. Examples include the stomach, liver and spleen
38
What are retroperitoneal viscera?
Retroperitoneal organs are not associated with visceral peritoneum; they are only covered in parietal peritoneum, and that peritoneum only covers their anterior surface.
They can be further subdivided into two groups based on their embryological development:
Primarily retroperitoneal organs developed and remain outside of the parietal peritoneum. The oesophagus, rectum and kidneys are all primarily retroperitoneal.
Secondarily retroperitoneal organs 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 descending colon.
39
What is the pneumonic for remembering which abdominal viscera are retroperitoneal?
A useful mnemonic to help in recalling which abdominal viscera are retroperitoneal is SAD 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
40
What is the parietal peritoneum?
Where the peritoneum covers the inside of the abdominal wall it is called the parietal peritoneum
41
What is the visceral peritoneum?
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
42
What is ascites?
• 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.
43
Where would one find the urachus?
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
44
Describe the course of the remnants of the paired umbilical arteries?
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.
45
What would one find lateral to the remnants of the paired umbilical arteries?
identify the inferior epigastric artery and the deep inguinal ring lying lateral to it
46
What may be identified on the right upper flap of the retracted abdominal wall?
On the right upper flap, find the falciform ligament and palpate the remnant of umbilical vein; the ligamentum teres in its free edge
47
Where would you find and what is the left triangular ligament?
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
48
does the stomach lie deep or superficial to the left lobe of the liver?
Deep
49
Can the left lobe of the liver be palpated transabdominally?
Notice that the entire left lobe of the liver is above the costal margin and cannot be palpated trans-abdominally.
50
What lies on the inferior surface of the right lobe of the liver?
Gall bladder (stained green)
51
Can the right lobe of the liver be palpated?
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
52
What is the lesser omentum?
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.
53
What is the porta hepatis and where can it be palpated?
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).
54
Describe the anatomical position of the spleen and can it normally be palpated?
* 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
55
What are the borders of the greater omentum?
* 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.
56
What is the only way from the peritoneal sac to the lesser sac?
Through the epiploic foramen
57
What structure is attached to the deep surface of the greater omentum?
The transverse colon
58
What is the location of the duodenal-jejunal flexure?
just below the transverse colon mesentery
59
Where is the ileocaecal junction?
In the right iliac region, where the terminal ileum curves upwards and forms the caecum
60
Where is the appendix and where does its mesentery attach?
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.
61
What is the pathway from the pyloric sphincter to the rectum?
Duodenum, Duodenal-jejunal flexure, jejunum, ileum, ileocaecal junction, caecum, ascending colon, hepatic flexure, transverse colon, splenic flexure, descending colon, sigmoid colon, rectum
62
What is the issue with infection in the abdomen?
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.
63
What is the clinical significance of the semi-permeability of the peritoneum?
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
64
Explain the difference between fixed and mobile parts of the abdomen in terms of consequences of inflammation?
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.
65
With the patient in a supine position, where might fluid collect in the abdomen?
Posterior to the liver
66
What embryological structure forms the ligamentum teres?
Remnant of the umbilical vein
67
Where does the base of the appendix lie (surface marking and internally)?
The base of the appendix is located 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 the surface known as McBurney's point.
68
Which parts of the bowel have a mesentery?
Mesentery proper - from small intestine (jejunum and ileum) to posterior abdominal wall (contains superior 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)
69
What is the greater omentum?
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.
70
What structures lie behind the lesser sac?
lesser sac the pancreas, splenic artery and part of the duodenum, these are collectively referred to as the gastric bed.
71
What is the issue with tumours in the stomach?
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
72
What is the Coeliac Trunk?
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.
73
Where does venous blood drain into to travel to the liver?
Portal vein
74
What innervation does the foregut receive?
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).
75
Where would one find the pyloric sphincter?
At the junction between the pylorus of the stomach and the duodenum
76
What are the regions of the stomach?
The fundus, the body, the antrum, and the pyloric region
77
Where do the branches of the anterior vagal trunk travel to supply the stomach?
Look for the branches of the anterior vagal trunk supplying the stomach in the region of the lesser curvature.
78
What are the branches of right common hepatic artery?
• 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.
79
What is the path of the left gastric artery?
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.
80
Where does the right gastro-epiploic supply and where does it come from?
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
81
Where would one find the short gastric arteries?
In the region of the fundus look for some short gastric arteries arising from the splenic artery
82
Describe the extent of the lesser sac?
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.
83
What structures are visible in the lumen of the stomach?
lumen of the stomach to study the folds of mucous membrane in its interior; the rugae
84
Explain what happens to the veins around the liver during cirrhosis?
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
85
Describe Pyloric stenosis in children?
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
86
How can a peptic ulcer cause brisk bleeding?
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.
87
At what vertebral level does the oesophagus pass through the diaphragm?
T10
88
Which structure(s) passes through the diaphragm alongside the oesophagus?
The vagal trunks, inferior oesophageal artery and vein
89
What structure attaches the stomach to the liver?
The Lesser Omentum
90
Which structures lie in front of the stomach?
Left lobe of the liver, anterior abdominal wall
91
Which structures lie behind the stomach?
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
92
What is a porto-systemic anastomosis?
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
93
Is the duodenum mobile?
No it is fixed and constant
94
Which parts of the small bowel are mobile and what issues arise from this?
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).
95
In what ways is the small intestine specialised for nutrient absorption?
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.
96
Where are plicae circularis more pronounced?
Plicae circularis are more pronounced in the jejunum than the ileum
97
What are Peyer's Patches and where are they present?
The ileum has large submucosal lymph nodules known as Peyer’s patches.
98
Which food stuff is deposited more at the ileal end of the small intestine?
Lipids are deposited in the small bowel mesentery in increasing amounts towards the ileal end
99
What is Meckel's Diverticulum?
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.
100
What is the artery to the midgut?
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
101
Where would one find the arterial arcades and vasa rectae?
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
102
What lies to the right of the main superior mesenteric artery, what are the branches?
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.
103
What is the positioning of the large bowel?
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.
104
Describe the outer surface of the large intestine?
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.
105
Does the Caecum have a mesentery?
No
106
Which artery supplies the hindgut?
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
107
Where is the aortic bifurcation?
its bifurcation just above the sacral promontory
108
What is the root of the inferior mesenteric artery and what does the inferior mesenteric arterty supply?
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.
109
What is the pathway of the superior rectal artery?
* 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.
110
What is the path of the inferior mesenteric vein?
trace it to where it passes beneath the transverse colon mesentery; from here it passes upwards behind the pancreas to join the splenic vein
111
Where is the ileocaecal orifice and the orifice of the appendix?
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
112
What is the risk of a carcinoma of the colon and rectum?
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.
113
What causes Meckel's Diverticulum?
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.
114
What can happen when bowel on the mesentery twists?
• 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.
115
Which vein drains blood from the colon and where does it flow to?
Inferior mesenteric vein drains into the splenic vein
116
Where does lymph from the small bowel drain?
Into the cisterna chyli and to the thoracic duct
117
Which foodstuffs are absorbed through the lymphatic system?
Lipids
118
Where is the junction between the mid gut and the hind gut?
2/3 of the way along the transverse colon
119
How do you distinguish a loop of large intestine from that of small intestine?
Large intestine has appendices epiploicae and tenia coli. The small bowel is centrally located and the colon round the sides
120
Which part of the bowel is supplied by sacral nerves 2, 3 and 4?
The hind gut
121
What are the branches of the coeliac trunk?
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.
122
Which part of the duodenum is not retroperitoneal?
only the duodenal cap (1st part) within the lesser omentum
123
Where is the head and the tail of the pancreas?
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.
124
What is the involvement between the superior mesenteric artery and vein and the pancreas?
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.
125
What is the first anterior branch of the abdominal aorta?
The first anterior branch of the abdominal aorta is the coeliac trunk.
126
Define the four parts of the duodenum?
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.
127
What are the four parts of the pancreas?
Head, neck, body, tail
128
What may be found in the grove between the head of the pancreas and the duodenum?
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.
129
Where would one find the duodenal papillae?
About halfway down the descending duodenum find the duodenal papillae
130
Where is the origin of the hepatic portal vein?
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.
131
How may gall stones cause jaundice, liver failure and pancreatitis?
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
132
What is a psuedocyst and how does it relate to pancreatitis?
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.
133
Describe the effect of carcinoma of the head of the pancreas?
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
134
What structures might a tumour of the head of the pancreas involve?
The hepatic portal vein, bile duct or pancreatic duct
135
What structures join to form the common bile duct and what is its course?
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
136
Where is the sphincter of Oddi located?
On the medial wall of the duodenum between the second and third parts
137
Which artery lies behind the first part of the duodenum?
Gastroduodenal artery
138
What lies between the pancreas and the stomach?
The lesser sac
139
How many pancreatic ducts are there? What is the embryological significance?
Two; one from the ventral pancreatic bud and one from the dorsal pancreatic bud.
140
Describe the 9 abdominal regions?
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.
141
Describe the abdominal wall muscles?
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
142
Describe the Splanchnic nerves?
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).
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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).
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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).
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143
Describe Visceral Peritoneum?
* 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.
144
Describe peritoneal peritoneum/parietal peritoneum?
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.
145
What is the Transversalis
| Fascia?
Deepest layer of fascia before reaching the peritoneum.
| • Lies between the Transversus Abdominis and Parietal Peritoneum
146
What is the ligamentum teres?
• 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’).
147
What is the falciform ligament?
• 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
148
What are the umbilical artery remnants?
• 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
149
What is the urachus?
Remnant of a structure that used to drain the foetal bladder into the
umbilical cord in the foetus.
• No function in adulthood.
150
What is the greater omentum?
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.
151
What is the small bowel mesentery?
• 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.
152
What is the foregut, midgut, and hindgut?
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
153
What is an appendicitis?
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
154
Describe the blood supply, rugae and pyloric sphincter of the stomach?
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.
155
Describe the features of the small intestine?
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.
156
Compare the jejunum and the ileum?
```
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.
```
157
Describe the features of the large intestine?
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).
158
Describe the lesser omentum?
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.
159
Describe the Lesser Sac?
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.
