GI Anatomy Flashcards
1
Q
How is the abdominal cavity separated from the thorax?
A
By the diaphragm.
2
Q
Which organs does the abdominal cavity contain?
A
- Stomach.
- Small and large intestines.
- Liver.
- Gallbladder.
- Kidneys.
- Ureters.
- Pancreas.
- Adrenal glands.
- Spleen.
- Great vessels and their branches.
3
Q
What are the anterior, lateral, and posterior walls of the abdomen composed of?
A
Skin, subcutaneous tissue, muscles and their associated aponeuroses (flat tendons).
4
Q
How many and which type of vertebrae contribute to the posterior wall of the abdominal cavity?
A
Five lumbar vertebrae.
5
Q
What are the functions of the abdominal wall?
A
- Protect the abdominal viscera.
- Increase intra-abdominal pressure (e.g. childbirth and defecation).
- Maintain posture and move the trunk.
6
Q
What is the internal aspect of the abdominal wall lined with?
A
Serous membrane called parietal peritoneum.
7
Q
What are the key bony landmarks for defining the borders of the abdominal cavity?
A
- Xiphisternum.
- Costal margin.
- Iliac crests.
- Anterior superior iliac spines (ASIS).
- Pubic tubercles.
- Pubic symphysis (a fibrocartilaginous joint).
8
Q
Describe the four quadrants of the anterior abdominal wall.
A
- Right upper q, left upper q, right lower q, left lower q.
- RUQ, LUQ, RLQ, LLQ.
- Vertical line runs down the midline through the lower sternum, umbilicus, and pubic symphysis.
- Horizontal line runs across the abdomen through the umbilicus.
9
Q
Describe the nine regions of the anterior abdominal wall.
A
- Right hypochondrium, epigastrium, left hypochondrium, right flank, umbilical region, left flank, right iliac fossa, suprapubic region, left iliac fossa.
- Vertical left and right midclavicular lines extending to the mid-inguinal points.
- Horizotal subcostal line, through the inferior-most parts of the costal margins.
- Horizontal intertubercular line, through the tubercles of the iliac crests and the body of L5.
10
Q
Describe the transpyloric plane.
A
- Horizontal line, passes through tips of the ninth costal cartilages.
- Transects the pylorus of the stomach, the gallbladder, the pancreas, and the hila of the kidneys.
11
Q
Describe the transumbilical plane.
A
- Unreliable landmark.
- Position varies on amount of subcutaneous fat present.
- Slender individual = around the level of L3.
12
Q
Describe the intercristal plane.
A
- Horizontal line, between highest points of iliac crests.
- Cannot be palpated anteriorly, used to guide back procedures.
13
Q
Describe McBurney’s point.
A
- Surface marking of the base of the appendix.
- Lies 2/3 along a line from the umbilicus to the right anterior superior iliac spine.
14
Q
What are the four pairs of muscles that comprise the anterolateral abdominal wall? What are the orientations of their fibres?
A
- External oblique (diagonal; medially and inferiorly).
- Internal oblique (diagonal: medially and superiorly).
- Transversus abdominis (horizontal).
- Rectus abdominis (straight).
15
Q
Describe the positions of the four pairs of muscles that comprise the anterolateral abdominal wall?
A
- Right and left rectus abdominis muscles lie either side of the linea alba.
- Lateral lie three sheets of muscles:
- External oblique (EO) = most superficial.
- Internal oblique (IO) = deep to EO.
- Transversus abdominis = deep to IO.
16
Q
What happens when the four pairs of muscles that comprise the anterolateral abdominal wall contract together?
A
They increase intra-abdominal pressure.
17
Q
What happens when oblique muscles act alone?
A
Act as lateral flexors of the lumbar spine.
18
Q
What are the attachments of the rectus abdominis?
A
- Sternum and costal margin superiorly.
- Pubis inferiorly.
- Surrounded by an aponeurotic rectus sheath.
19
Q
What happens to the four pairs of muscles that comprise the anterolateral abdominal wall anteriorly?
A
- Become aponeurotic (flat tendons).
- Fibres fuse, and in the midline, fuse with the opposite aponeuroses, forming a rough midline raphe (seam) called the ‘linea alba’ (white line).
- Also form the rectus sheath.
20
Q
How is a ‘six-pack’ formed?
A
- Right and left rectus abdominis muscles are composed of muscle segments interspersed with horizontal tendinous bands.
- Segments hypertrophy with exercise = bulge either sides of the bands.
21
Q
What is the relationship between the rectus abdominis and the lumbar spine?
A
The rectus abdominis acts as a flexor of the lumbar spine.
22
Q
How is the rectus sheath formed?
A
- Aponeuosis of IO splits into anterior and posterior layers.
- EO aponeurosis and anterior layer of the IO aponeurosis = anterior wall of rectus sheath.
- Transversus abdominis aponeurosis and posterior layer of the IO aponeurosis = posterior wall of rectus sheath.
23
Q
Describe the locations of the transversalis fascia and parietal peritoneum.
A
Transversalis fascia = deep to transversus abdominis, deep to the fascia = parietal peritoneum.
24
Q
How is the inguinal ligament formed?
A
Most inferior part of EO aponeurosis attached to anterior superior iliac spine laterally, and pubic tubercle medially.
25
Describe the blood supply of the anterolateral abdominal wall?
- Musculophrenic artery (branch of internal thoracic artery).
- Superior epigastric artery (continuation of the internal thoracic artery, descends in rectus sheath).
- Inferior epigastric artery (branch of external iliac artery, ascends in rectus sheath, and anastomoses with superior epigastric).
- Also deep veins, and an extensive network of superficial veins.
26
Describe the innervation of the anterior abdominal wall?
- Thoraco-abdominal nerves T7 -> T11 (essentially continuations of intercostal nerves T7 -> T11). Contain sensory and motor fibres.
- Subcostal nerve, originates from T12 spinal nerve.
- Iliohypogastric and ilioinguinal nerves, both branches of L1 spinal nerve.
27
Describe the inguinal canal.
- Oblique passageway , around 5cm long in the adult.
- Passes through the muscles of the anterior abdominal wall medially and inferiorly.
- Extends from deep inguinal ring laterally (aperture in transversalis fascia), to the superficial inguinal ring medially (aperture in EO aponeurosis).
28
Describe the anterior border of the inguinal canal.
- EO aponeurosis
- Laterally only: IO aponeurosis.
29
Describe the posterior border of the inguinal canal.
- Transversalis fascia.
- Medially only: medial fibres of the aponeurosis of the IO and transversus abdominis (conjoint tendon).
30
Describe the roof of the inguinal canal.
- Transversalis fascia.
- Arching fibres of IO and transversus abdominis.
31
Describe the floor of the inguinal canal.
- Inguinal ligament (lower border of EO aponeurosis).
32
What are some clinical relevancies of the abdomen, abdominal wall, and the inguinal canal?
- Abdominal wall hernias.
- Laparotomy.
- Abdominal aortic aneurysm (AAA).
- Inguinal hernias.
33
Describe the visibility and innervation of the parietal peritoneum.
- Can be seen with the naked eye.
- Innervated by somatic nerves that supply overlying muscles and skin of the abdominal wall.
34
Describe pain from the parietal peritoneum.
Usually sharp, severe, and well-localised.
35
Describe the visibility and innervation of the visceral peritoneum.
- Cannot be seen with the naked eye.
- Innervated by visceral sensory nerves, which convey painful sensations -> CNS along the path of sympathetic nerves that innervate the organ/structure it covers.
36
Describe pain from the visceral peritoneum.
- Can be severe, usually dull and diffuse (difficult to pinpoint location).
- Pain sensations may be perceived as nausea or distension.
37
What lies between the parietal and visceral peritoneum? Are these two layers continuous?
- Peritoneal cavity, usually containing a thin film of peritoneal fluid.
- Continuous with each other.
38
What does it mean if an abdominal viscera is described as intraperitoneal?
Almost completely covered by peritoneum e.g. the stomach.
39
What does it mean if an abdominal viscera is described as retroperitoneal?
Posterior to the peritoneum, so only covered by it on their anterior surface e.g. pancreas, and abdominal aorta.
40
What does it mean if an abdominal viscera is described as secondarily retroperitoneal?
Was intraperitoneal in early development, but became 'stuck down' onto posterior abdominal wall.
41
Describe mesenteries.
- Folds of peritoneum that contain fat.
- Suspend the small intestine, and parts of the large intestine, from the posterior abdominal wall.
- The arteries that supply the intestines, and the veins that drain the gut, are embedded within.
42
Describe the omenta.
The greater and lesser omenta are folds of peritoneum that are usually fatty and connect the stomach to the other organs.
43
Describe the greater omentum.
- Hangs from great curvature of the stomach.
- Lies superficial to the small intestine.
44
Describe the lesser omentum.
- Connects stomach and the duodenum to the liver.
- Hepatic artery, hepatic portal vein, and bile duct (the portal triad), are embedded within its free edge.
45
Describe ligaments.
- Folds of peritoneum that connect organs to each other or to the abdominal wall.
46
Describe the falciform ligament.
Connects anterior surface of the liver to the anterior abdominal wall.
47
Describe the coronary and triangular ligaments.
Connect the superior surface of the liver to the diaphragm.
48
Describe the peritoneal folds.
- Raised from the internal aspect of the lower abdominal wall.
- Created by the structures they overlie, like carpet over a cable.
- Sometimes difficult to see.
49
Describe the median umbilical fold.
- Lies in the midline.
- Represents the remnants of the urachus (embryological structure connecting the bladder to the umbilicus).
50
Describe the medial umbilical folds.
- Lateral to the median umbilical fold.
- Represent the remnants of the paired umbilical arteries (returned venous blood to the placenta in foetal life).
51
Describe the lateral umbilical folds.
- Lateral to the medial umbilical folds.
- Inferior epigastric arteries lie deep to these folds, they supply the anterior abdominal wall.
52
How is the peritoneal cavity divided?
- Two regions of unequal size:
- Lesser sac (AKA the omental bursa), smaller and lies posterior to the stomach and anterior to the pancreas.
- Greater sac, remaining part of the peritoneal cavity.
53
How do the lesser and greater sacs communicate with each other?
Via a passageway that lies posterior to the free edge of the lesser omentum called the epiploic foramen (aka omental foramen).
54
Where does the GI system develop?
In the embryonic gut tube, which lies in the midline of the abdominal cavity, suspended from the posterior abdominal wall by the dorsal mesentery.
55
What travels through the dorsal mesentery?
Major branches of the abdominal aorta that supply the developing gut tube.
56
What is the role of the ventral mesentery?
- Connecting the stomach to the anterior abdominal wall.
- As the liver grows within it, the anterior part of the ventral mesentery becomes the falciform ligament, and the posterior part becomes the lesser omentum.
57
What is responsible for the formation of the lesser sac?
Growth, migration, and rotation of organs during development.
58
What are some clinical relevancies of the peritoneal cavity and the peritoneum?
- Peritonitis.
- Peritoneal adhesions.
- Ascites.
59
What does the oesophagus pass through, and at what level, to enter the abdomen? What is the function of this entrance?
- The oesophageal hiatus.
- At the level of T10.
- Muscles form a sphincter that prevents reflux of stomach contents into the oesophagus.
60
How long is the abdominal segment of oesophagus?
Less than 2cm long.
61
Which artery supplies the distal oesophagus?
The left gastric artery.
62
Describe the venous drainage of the distal oesophagus. Describe the clinical significance of this.
Drains towards both the systemic system of veins (via oesophageal veins that drain into the azygos vein), and to the portal venous system (via the left gastric veins).
Therefore the distal oesophagus is a site of portosystemic anastomoses.
63
What is the shape of the stomach, and how many parts is it described in?
J-shaped sac, described in 4 parts.
64
How does the stomach break down food? What is food broken down to?
- Chemically and mechanically breaks down food.
- Breaks down food into chyme.
65
What are the four parts of the stomach?
- Cardia.
- Fundus.
- Body.
- Pyloric part.
66
Which part of the stomach is the oesophagus continuous with?
The cardia.
67
Which is the most superior part of the stomach? Describe it.
- The fundus.
- It is superior to the level of entry of the oesophagus, and usually filled with gas.
68
Which is the largest part of the stomach?
The body.
69
Which part of the stomach is distal to the body? Describe it.
- The pyloric part.
- Pyloric antrum is wide, and tapers towards the pyloric canal, which is narrow and contains the pyloric sphincter.
70
Describe the pyloric sphincter and its role.
- Formed of circular smooth muscle.
- Regulates the passage of chyme into the duodenum.
71
What are the left and right borders of the stomach called?
Right (shorter) = lesser curvature.
Left (longer) = greater curvature.
72
Where does the stomach lie in relation to the four quadrants?
Left upper quadrant.
73
What is the anterior surface of the stomach related to?
- Anterior abdominal wall.
- Diaphragm.
- Left lobe of the liver.
74
What does the posterior surface of the stomach form?
The anterior wall of the lesser sac.
75
What does the lesser omentum connect in relation to the stomach?
Connects the liver to the lesser curvature of the stomach.
76
Where does the greater omentum lie in relation to the stomach?
Hangs from the great curvature of the stomach.
77
What does the free edge of the lesser omentum contain?
- Hepatic artery.
- Hepatic portal vein.
- Bile duct.
78
Where can the entrance to the lesser sac be found?
Posterior to the free edge of the lesser omentum.
79
Describe the general blood supply to the stomach.
- Suppled by arteries that branch from the coeliac trunk (short stump).
- This is 1/3 large unpaired vessels that leave the anterior aspect of the abdominal aorta at T12 to supply abdominal viscera derived from the embryological foregut.
- Three branches of the coeliac trunk: left gastric, common hepatic, and splenic artery.
80
Which arteries run along the lesser curvature of the stomach and anastomose with each other? Where do they arise from?
- Left and right gastric arteries.
- Left arises from coeliac trunk.
- Right may arise from common hepatic artery or hepatic artery proper.
81
Which arteries run along the greater curvature of the stomach and anastomose with each other? Where do they arise from?
- Left and right gastro-omental (gastroepipolic) arteries.
- Left arises from splenic artery.
- Right arises from gastroduodenal artery, a branch of the common hepatic artery.
82
Where do the veins that accompany the arteries running down the curvatures of the stomach drain into?
- The hepatic portal vein (HPV).
83
Briefly describe the hepatic portal vein.
A large vein that carries nutrient-rich venous blood from the GI tract to the liver.
84
Which cranial nerve conveys parasympathetic fibres to the stomach?
The vagus nerve (CN X).
85
What does parasympathetic stimulation of the stomach promote?
Peristalsis and gastric secretion.
86
Which nerve conveys sympathetic fibres to the stomach?
The greater splanchnic nerve.
87
Describe the greater splanchnic nerve.
- Formed of preganglionic sympathetic fibres that leave spinal cord segments T5 -> T9, and pass through the sympathetic trunk without synapsing.
- Fibres synapse in prevertebral ganglia around the coeliac trunk.
- Postganglionic fibres travel to the stomach.
88
What does sympathetic stimulation of the stomach promote?
Inhibition of peristalsis and gastric secretion.
89
Give some clinical relevancies of the distal oesophagus, the stomach and the lesser sac.
- Hiatus hernia.
- Gastric ulcer.
- Pyloric stenosis.
- Gastric cancer.
90
What are the three parts of the small intestine?
- The duodenum.
- The jejunum.
- The ileum.
91
Describe the location and shape of the duodenum.
- Continuous with the pylorus of the stomach.
- Short and curved into a C-shape around the head of the pancreas.
92
What is the major duodenal papilla, and where can it be found?
- Opening of the bile duct and the main pancreatic duct into the duodenum.
- Found around halfway along the internal wall of the duodenum.
93
Describe the embryological origin of the duodenum.
- First half develops from embryological foregut.
- Second half develops from embryological midgut.
94
Describe the blood supply of the duodenum.
- First half = arterial branches from the coeliac trunk.
- Second half = superior mesenteric artery.
95
Which parts of the small intestine are retroperitoneal or intraperitoneal?
Duodenum = retro.
Jejunum and ileum = intra.
96
Describe the location of the jejunum and ileum.
- Jejunum continuous with duodenum, ileum continuous with jejunum.
- Suspended from posterior abdominal wall by mesentery of the small intestine.
- Jejunum = LUQ.
- Ileum = RLQ.
97
Where are the blood vessels that supply the small intestine found?
Embedded within the mesentery.
98
Describe the embryological origin of the jejunum and ileum.
Both derived from the embryological midgut.
99
How can you determine the difference between jejunum and ileum?
- Externally = very difficult.
- Internally = jejunum have more pronounced plicae (mucosa folds), ileum characterised by Peyer's patches (large submucosal lymph nodules).
100
What is the terminal ileum continuous with, and where does this occur?
- The caecum (first part of the large intestine).
- At the ileocaecal junction in the right iliac fossa.
101
What is the function of the large intestine?
Reabsorbs water from faecal material to form semi-solid faeces.
102
What are the eight components of the large intestine?
- Caecum.
- Appendix.
- Ascending colon.
- Transverse colon.
- Descending colon.
- Sigmoid colon.
- Rectum.
- Anal canal.
103
Is the large intestine retroperitoneal or intraperitoneal?
Some segments are retro, others are intra.
104
Describe the caecum.
- First part of large intestine.
- Distended, blind-ended 'pouch'.
- Intraperitoneal, but no mesentery.
105
Describe the appendix.
- Small diverticulum arising from the caecum.
- Contains lymphoid tissue.
- Surface marking of the base = McBurney's point.
- Varies in length, and tip position is variable.
- Connected to caecum by mesoappendix (a small mesentery).
106
Describe the ascending colon.
- Continuous with the caecum.
- Runs vertically, right side of the posterior abdominal wall, in the right paracolic gutter.
- Retroperitoneal (secondarily).
107
Describe the connection between the ascending and transverse colon.
- Ascending makes a 90 degree turn left in the RUQ, becoming continuous with the transverse colon.
- This bend is called the hepatic fixture.
108
Describe the transverse colon.
- Continuous with ascending colon.
- Runs horizontally in the upper abdomen, but often hangs inferiorly.
- Intraperitoneal and suspended from the posterior abdominal wall by the transverse mesocolon.
109
Describe the embryological significance of the transverse colon.
- Marks transition of embryological midgut and hindgut.
- Proximal 2/3 = midgut.
- Distal 1/3 = hindgut.
- Therefore two parts supplied by different blood vessels and nerves.
110
Describe the connection between the transverse and descending colon.
- Transverse makes a 90 degree turn inferiorly in the LUQ, becoming continuous with the descending colon.
- This bend is called the splenic flexure.
- Splenic flexure tethered to the diaphragm by the phrenicocolic ligament.
111
Describe the descending colon.
- Continuous with the transverse colon.
- Runs vertically on left side of posterior abdominal wall, in the left paracolic gutter.
- Retroperitoneal (secondarily).
112
Describe the sigmoid colon.
- In the LLQ.
- Sinuous shape hence its name.
- Continuous with the descending colon.
- As it approaches the midline, it makes a 90 degree turn inferiorly into the pelvis.
- This bend is called the rectosigmoid junction.
- Intraperitoneal, with sigmoid mesocolon.
113
Describe the rectum and anal canal.
- Rectum lies in pelvis.
- Retroperitoneal.
- Continuous with the rectosigmoid junction (level of S3).
- Anal canal is continuous with the rectum.
114
What is the function of the rectum?
Stores faeces until it is convenient to defecate.
115
Which three large unpaired arteries supply the GI tract? Where do these come from?
- Coeliac trunk.
- Superior mesenteric artery (SMA).
- Inferior mesenteric artery (IMA).
- Come from abdominal aorta.
116
Which part of the embryological gut does the coeliac trunk supply with its branches? Which organs/structures does it therefore supply?
Foregut:
- Oesophagus.
- Stomach
- First 1/2 duodenum.
- Liver.
- Gallbladder.
- Bile ducts.
- Pancreas.
- Spleen.
117
Which part of the embryological gut does the superior mesenteric artery supply with its branches? Which organs/structures does it therefore supply?
Midgut:
- Second 1/2 duodenum.
- Small intestine.
- Large intestine; as far as, and including, the proximal 2/3 of the transverse colon.
- Parts of the pancreas.
118
What are the five major branches of the superior mesenteric artery? What do these supply?
- Jejunal branches; several branches to the jejunum.
- Ileal branches; several branches to the ileum.
- Ileocolic artery; supplies the caecum, appendix, and ascending colon.
- Right colic artery; supplies ascending colon.
- Middle colic artery; supplies the transverse colon.
119
Where can the jejunal and ileal branches be found? What happens when the anastomose?
- Embedded in mesentery of small intestines.
- Anastomose to form loops of arteries called arcades.
- From arcades, run the vasa recta (straight vessels), which supply the intestinal wall.
120
Which part of the embryological gut does the inferior mesenteric artery supply with its branches? Which organs/structures does it therefore supply?
Hindgut:
- Distal 1/3 transverse colon.
- Descending colon.
- Sigmoid colon.
- Rectum.
- Upper part of anal canal.
121
What are the three major branches of the inferior mesenteric artery? What do these supply?
- Left colic artery; supplies transverse colon and descending colon.
- Sigmoid branches; supplies sigmoid colon.
- Superior rectal artery; terminal branch of IMA, supplies the rectum.
122
Where do the middle colic artery (from SMA) and left colic artery (from IMA) anastomose? What does this form?
- Anastomose along the distal 1/3 of the transverse colon and the splenic flexure.
- Forms the marginal artery.
123
Which other branches anastomose in the blood supply of the GI tract?
- Branches of left colic and sigmoid arteries.
124
Describe the blood supply of the rectum.
- Superior rectal artery (terminal branch if IMA).
- Middle and inferior rectal arteries (branch from internal iliac arteries in pelvis).
- Middle and inferior rectal arteries anastomose with branches of the superior rectal artery.
125
At what level does the coeliac trunk leave the AA?
T12.
126
At what level does the superior mesenteric artery leave the AA?
L1.
127
At what level does the inferior mesenteric artery leave the AA?
L3.
128
Where does venous blood from the gut ultimately reach?
The inferior vena cava (IVC), and returns to the heart.
129
What happens to the venous blood from the gut before it can return to the heart via the IVC?
Contains nutrients, so first enters the liver via the portal venous system.
130
Describe the inferior mesenteric vein (IMV) and its drainage.
- Accompanies IMA.
- Drains the hindgut.
- Ascends on left side of abdomen.
- Typically drains into splenic vein.
131
Describe venous drainage from the rectum.
Drains into both the portal system via the IMV, and into the systemic system via internal iliac veins.
132
Describe the superior mesenteric vein (SMV) and its drainage.
- Accompanies SMA.
- Drains the midgut.
- Ascends and unites with splenic vein close to the liver.
- This unity forms the hepatic portal vein.
133
Describe the hepatic portal vein and the hepatic veins.
- Hepatic portal vein enters liver.
- Nutrients removed from blood.
- Blood enters small hepatic veins, which unite to form two or three large hepatic veins.
- Large hepatic veins enter the IVC as it passes posterior the liver.
134
Which nerves do the parasympathetic fibres travel down to reach the foregut and midgut?
The vagus nerves (CN X).
135
Which nerves do the parasympathetic fibres travel down to reach the hindgut? Describe the formation of these nerves.
- The pelvic splanchnic nerves.
- Formed by axons of parasympathetic neurons that lie in the sacral spinal cord.
- Cell bodies of preganglionic parasympathetic neurons lie in S2 -> S4 segments.
- Axons leave the spinal cord and form pelvic splanchnic nerves.
- Preganglionic axons synapse with a second neuron in a ganglion.
- The ganglia are located very close to/within the walls of the viscera.
136
Describe sympathetic innervation of the foregut, midgut, and hindgut.
- Greater splanchnic carries fibres from T5 -> T9, and innervates the foregut.
- Lesser splanchnic carries fibres from T10 -> T11, and innervates the midgut.
- Least splanchnic carries fibres from T12, and innervates the hindgut.
137
Describe the formation of the greater, lesser, and least splanchnic nerves.
- Preganglionic sympathetic fibres pass through sympathetic trunk without synapsing.
- Synapse in ganglia that lie in the abdomen, clustered around the three major unpaired arteries, and the AA.
- Postganglionic fibres from visceral nerves that innervate the gut.
138
How does parasympathetic innervation affect the gut?
Stimulates peristalsis and secretions.
139
How does sympathetic innervation affect the gut?
Inhibits peristalsis and secretions.
140
What type of fibres are sympathetic and parasympathetic?
Visceral motor fibres.
141
What fibres innervate the gut other than visceral motor fibres? What do these fibres do?
- Visceral sensory fibres.
- Convey sensory information to the CNS.
- Doesn't usually reach consciousness, but can.
142
What is the rule regarding visceral sensory fibres and there sensation effects?
- Travel with sympathetic = convey painful sensations.
- Travel with parasympathetic = convey information that maintains internal environment, and elicits reflex responses.
143
Where do painful sensations from the different sections of the gut enter the spinal cord?
Foregut = T5 -> T9.
Midgut = T10 -> T11.
Hindgut = T12.
144
Which regions of the spinal cord receive somatic sensory information from which parts of the abdominal wall?
Segments T5 -> T9; receive info from dermatomes T5 -> T9 (upper abdomen and epigastrium).
Segments T10 -> T11; dermatomes T10 -> T11 (umbilical region).
Segment T12; dermatome T12 (suprapubic region).
145
In clinical practice, which regions of abdominal wall pain suggest which area of gut pathology?
- Epigastric suggests foregut.
- Central abdo/umbilical suggest midgut.
- Lower abdo/suprapubic suggests hindgut.
146
Give some clinical relevancies of the small and large intestines.
- Appendicitis.
- Mesenteric ischaemia.
- Inflammatory bowel disease.
- Colon cancer.
- Volvulus.
147
Where can the liver be found in the abdomen?
RUQ and epigastrium.
148
How is the liver protected?
By the ribs.
149
How does the liver move during inspiration?
Inferiorly, so the lowermost part may be palpable below the right costal margin in inspiration.
150
What transports the products of digestion to the liver from the gut?
The hepatic portal vein.
151
Which digestive product is not transported to the liver?
Lipids.
152
What does the liver produce? Where is it stored?
Bile, transported to the gallbladder to be stored.
153
What is the role of bile?
Emulsifies lipids in the chyme entering the duodenum from the stomach.
154
What are the two surfaces of the liver, where do they lie?
Diaphragmatic - anterosuperior, related to inferior surface of diaphragm.
Visceral - posteroinferior, related to other organs.
155
Which areas of the liver are not covered by visceral peritoneum?
- Bare area of liver: region of the posterior surface that lies in contact with the diaphragm.
- Region where the gallbladder lies in contact with the liver.
- Region of the porta hepatis (equivalent of the hilum of the lung).
156
How many lobes is the liver made up of?
Two anatomical lobes - a large right, and small left lobe.
(Separated by the falciform ligament).
Two accessory lobes (don't represent internal, functional organisation of the liver) - caudate and quadrate, on the posteroinferior surface.
157
Internally, how many functional segments is the liver divided into? Describe how these are served.
Eight, each served by their own branch of the hepatic artery and portal vein, and by their own hepatic duct.
158
How many recesses are related to the liver? What are these called?
2: the hepatorenal recess, and the left and right subphrenic recesses.
159
What are 3 anatomical connections of the liver?
Diaphragm - by coronary and triangular ligaments.
Anterior abdominal wall - by falciform ligament.
Stomach and duodenum - by the lesser omentum.
160
What makes up the portal triad? Where does it lie?
- Hepatic artery, hepatic portal vein, and the bile duct.
- In the free edge of the lesser omentum.
161
What is the epiploic foramen?
The entrance into the lesser sac.
162
What forms the anterior border of the epiploic foramen?
The portal triad and the free edge of the lesser omentum.
163
Which part of the embryological gut does the liver develop from?
The foregut.
164
What does the free edge of the falciform ligament contain? Explain its foetal significance.
- The round ligament of the liver (the ligamentum teres).
- Remnant of the umbilical vein (which carried oxygenated blood from placenta -> foetus).
165
Describe the ligamentum venosum.
- Lies on posterior surface of the liver.
- In the groove between the caudate lobe and left lobe of the liver.
- Remnant of the ductus venosus (diverts blood from umbilical vein -> IVC, shunting oxygen-rich blood to the heart and bypassing the liver).
166
Describe the blood supply/drainage of the liver.
Supplied by right and left hepatic arteries, entering at the porta hepatis, which ultimately derive from the coeliac trunk.
Exits via two or three large hepatic veins within the liver, which unite with the inferior vena cava as it passes posterior to the liver.
167
Describe the branching of the coeliac trunk -> hepatic arteries.
Coeliac trunk -> left gastric, splenic, and common hepatic arteries.
Common hepatic artery -> gastroduodenal artery, the common hepatic becomes the hepatic artery proper.
Hepatic artery proper bifurcates -> right and left hepatic arteries.
168
Describe the difference between the hepatic veins and the hepatic portal vein.
Hepatic veins take blood from the liver to the IVC.
Hepatic portal vein transports nutrient-rich venous blood from the gut to the liver.
169
Where does the hepatic portal vein receive blood from?
The superior and inferior mesenteric veins, and the splenic vein.
170
Describe the hepatic plexus.
Serves the liver, formed of parasympathetic fibres from the vagus nerves, and sympathetic fibres.
Fibres follow the path of the hepatic vessels and ducts of the biliary tree.
171
What is the role of the gallbladder?
Stores and concentrates bile.
172
Where does the gallbladder lie?
On the posteroinferior (visceral) surface of the liver, and close to the duodenum.
173
How many parts does the gallbladder consist of? What are these called?
3: the fundus, the body, and the neck.
174
Describe the 3 parts of the gallbladder?
Body - main part, sits in the gallbladder fossa on the visceral surface of the liver.
Neck - body tapers towards the neck, which communicates with the cystic duct.
Fundus - rounded end of the gallbladder, typically extends to the inferior border of the liver.
175
What is the surface marking of the fundus of the gallbladder?
The tip of the 9th costal cartilage, where the right midclavicular line intersects with the right costal margin.
176
Which cells produced bile continuously? Where are these?
Hepatocytes in the liver.
177
Where is bile first excreted into?
Small channels called bile canaliculi.
178
Describe the gradual formation of the right and left hepatic ducts. Where do these ducts leave he liver?
Canliculi drain into bile ducts of increasing calibre, ultimately converging to form the right and left hepatic ducts, which exit the liver at the porta hepatis.
179
Describe the formation of the common bile duct.
Right and left hepatic ducts -> common hepatic duct.
Common hepatic duct receives cystic duct -> common bile duct.
180
Describe the location of the common bile duct.
- Runs in the free edge of the lesser omentum.
- Descends posterior to the superior part of the duodenum, and posterior to the head of the pancreas.
- Enters the duodenum.
181
If bile leaving the liver is not needed for digestion, where does it go and how? What happens when it is then needed?
Enters the gallbladder via the cystic duct.
When needed, bile flows from the gallbladder, via the cystic duct, to the common bile duct and the duodenum.
182
Where does the spiral fold/valve lie?
At the junction between the gallbladder neck and the cystic duct.
183
Describe the blood supply/drainage of the gallbladder.
- Blood supplied via the cystic artery, which typically arises from the right hepatic artery.
- Drained by cystic veins that pass directly into the liver, or join the hepatic portal vein.
184
Describe the innervation of the gallbladder.
Parasympathetic and sympathetic fibres.
185
Where is the location of referred pain of the liver?
The epigastrium.
186
Where is referred pain of the gallbladder usually felt (3 places)?
The epigastrium (visceral afferents -> CNS with the sympathetic fibres).
Right shoulder (pathology irritates the diaphragm -> phrenic nerve, C3 -> 5, shares segments with somatic sensory info from the skin of the shoulder).
Right hypochondrium (pathology irritates parietal peritoneum, innervated by somatic nerves).
187
Give some clinical relevancies of the liver and the gallbladder.
- Hepatomegaly.
- Liver metastases.
- Cirrhosis of the liver.
- Portal hypertension and portosystemic anastomoses.
- Gallstones, biliary colic, and cholecystitis.
188
Which structures does the left gastric artery supply?
- Distal oesophagus.
- Lesser curvature of the stomach.
189
Which structures does the common hepatic artery supply?
Branches supply:
- Liver.
- Stomach.
- Duodenum.
190
Which structures does the splenic artery supply?
Branches supply:
- Stomach.
- Pancreas.
- Spleen.
191
How does the duodenum fit around the pancreas?
Forms a C-shape that cups the head of the pancreas.
192
How many parts is the duodenum described as? What are these called?
4: superior (1st), descending (2nd), inferior (3rd), and ascending (4th).
193
Which 3 structures lie posterior to the superior part of the duodenum?
- The common bile duct.
- The gastroduodenal artery.
- The hepatic portal vein.
194
Which artery lies anterior to the inferior part of the duodenum?
The superior mesenteric artery.
195
What does the ascending part of the duodenum meet? At which flexure?
The jejunum, at the duodenojejunal flexure.
196
What can be found approximately halfway along the internal wall of the duodenum?
The major duodenal papilla.
197
What does the major duodenal papilla mark?
The point at which bile and digestive pancreatic secretions enter the duodenum.
198
Describe the blood supply of the duodenum.
First half - foregut derivative, therefore coeliac trunk.
Second half - midgut derivative, therefore SMA.
Branches that supply the duodenum are derived from:
- The gastroduodenal artery (from the common hepatic artery, hence the coeliac trunk).
- The inferior pancreaticoduodenal arteries (from the superior mesenteric artery).
199
Describe the veinous drainage of the duodenum.
Veins follow the arteries, and are tributaries of the hepatic portal vein.
200
Where can the pancreas be found? Describe its appearance.
Lies horizontally on the posterior abdominal wall at the level of L1, and is retroperitoneal. Doesn't have a capsule so is bumpy rather than smooth.
201
How many parts is the pancreas composed of? What are these called?
4: the head, neck, body, and tail.
202
What is the uncinate process?
A hook-like projection off the head of the pancreas.
203
Describe where the head and tail of the pancreas can be found in relation to other abdominal viscera?
Head - cupped by the C-shaped duodenum.
Tail - extends to the hilum of the spleen.
204
What does the pancreas form in terms of the lesser sac?
Part of the posterior wall of the lesser sac.
205
Which artery is embedded in the upper border of the pancreas? Where is it heading?
The splenic artery, running towards to the spleen.
206
Where does the splenic vein run in relation to the pancreas?
Posterior to the pancreas.
207
Which two ducts can be found within the substance of the pancreas?
- The main pancreatic duct.
- The accessory pancreatic duct.
208
What is the endocrine function of the pancreas?
It synthesises and secretes insulin and glucagon. Insulin is released in response to high levels of glucose in the blood.
209
What is the exocrine function of the pancreas?
Produces pancreatic juice that contains digestive enzymes. This is transported through the main pancreatic duct and the accessory pancreatic duct to the duodenum. These ducts usually communicate with each other.
210
Where do the common bile duct and main pancreatic duct merge?
The hepatopancreatic ampulla.
211
Where does the hepatopancreatic ampulla open into?
At the major duodenal papilla, about halfway along the internal wall of the duodenum.
212
What is the hepatopancreatic ampulla surrounded by?
Smooth muscle - the hepatopancreatic sphincter (aka the sphincter of Oddi).
213
What does contraction of the hepatopancreatic sphincter prevent?
Reflux of duodenal contents into the common bile duct and main pancreatic duct.
214
Where does the accessory pancreatic duct empty pancreatic juice into the duodenum?
At the minor duodenal papilla, which lies just proximal to the major duodenal papilla.
215
Describe the blood supply of the pancreas.
- The splenic artery (major branch of coeliac trunk) runs along the upper border, giving rise to pancreatic arteries.
- The gastroduodenal artery (from common hepatic, hence coeliac trunk) gives rise to the superior pancreaticoduodenal arteries.
- The SMA gives rise to the inferior pancreaticoduodenal arteries.
216
Describe the venous drainage of the pancreas.
Veins follow the arteries.
The splenic vein drains the pancreas, and unites with the SMV to form the hepatic portal vein posterior to the neck of the pancreas.
217
Describe the spleen and its location.
- A haemotopoietic and lymphoid organ.
- Lies in the LUQ.
- Protected by ribs 9 -> 11.
- Covered with visceral peritoneum.
218
Give some of the functions of the spleen.
- Breakdown of old RBCs.
- Storage of RBCs and platelets.
- Various immune responses, including production of IgG.
219
What are the two surfaces of the spleen, where do they lie?
Diaphragmatic - adjacent to diaphragm.
Visceral - in contact with the stomach, left kidney, and colon (splenic vessels enter/exit at the hilum on this surface).
220
Name and describe the four borders of the spleen.
Anterior - notched.
Superior - notched.
Posterior - smooth.
Inferior - smooth.
221
Is a spleen usually palpable below the costal margin?
No. If it is palpable, it is enlarged by at least 3 times its normal size.
222
Describe the blood supply of the spleen.
- Supplied by the splenic artery, a branch of the coeliac trunk.
- This runs along the superior border of the pancreas, embedded within it.
- Artery divides into approximately 5 branches at the hilum.
223
Describe the venous drainage of the spleen.
Via the splenic vein, which runs posterior to the pancreas.
It unites with the SMV to form the hepatic portal vein.
224
Give some clinical relevancies of the duodenum, pancreas, and spleen.
- Duodenal ulcer.
- Pancreatitis.
- Pancreatic cancer.
- Diabetes mellitus.
- Splenomegaly.
- Splenic rupture.
