GI anatomy Flashcards
1
Q
What is the peritoneal cavity?
A
A potential space between the parietal and visceral peritoneum
2
Q
What does peritoneal fluid consist of?
A
Water, electrolytes, leukocytes, and antibodies
3
Q
Why is there peritoneal fluid present between parietal and visceral peritoneum?
A
Acts as a lubricant, enabling free movement of the abdominal viscera and the antibodies in the fluid fight infection
4
Q
What are the two compartments of the greater sac?
A
Supracolic and infracolic
5
Q
Where is the supracolic compartment of the greater sac and what does it contain?
A
Lying above the transverse mesocolon, containing the stomach, liver and spleen
6
Q
Where is the infracolic compartment and what does it contain?
A
Lies below the transverse mesocolon, contains the small intestine, ascending and descending colon
7
Q
How are the supracolic and infracolic compartments of the abdomen connected?
A
Via the paracolic gutters which lie between the posterolateral abdominal wall and the lateral aspect of the ascending or descending colon
8
Q
What are the subphrenic recesses?
A
Potential spaces in the supracolic compartment of the greater sac. They are located between the diaphragm and the liver. There are left and right subphrenic spaces, separated by the falciform ligament of the liver.
9
Q
Why are subphrenic abscesses more common on the right side?
A
Increased frequency of appendicitis and ruptured duodenal ulcers
10
Q
What is the omental bursa?
A
The lesser sac
11
Q
How is the omental bursa connected with the greater sac?
A
An opening in the omental bursa- the epiploic foramen. It is situated posterior to the free edge of the lesser omentum
12
Q
Where is Calot’s triangle located?
A
At the porta hepatis of the liver- where the hepatic ducts and neurovascular structures enter/ exit the liver
13
Q
What are the borders of Calot’s triangle?
A
Medial – common hepatic duct.
Inferior – cystic duct.
Superior – inferior surface of the liver.
14
Q
What are the contents of Calot’s triangle?
A
The right hepatic artery
The cystic artery
The lymph node of Lund
Lymphatics
15
Q
What are the roles of the abdominal peritoneum?
A
To support the viscera, and provide pathways for blood vessels and lymph to travel to and from the viscera
16
Q
What are the two layers of abdominal peritoneum?
A
Parietal (lining the internal surface of the abdominopelvic wall) and visceral (covering the majority of the abdominal viscera)
17
Q
What are the layers of abdominal peritoneum embyologically derived from?
A
Parietal- Somatic mesoderm
Visceral- Splanchnic mesoderm
18
Q
Why is pain from parietal peritoneum well localised?
A
It recieves the same somatic nerve supply as the region of the abdominal wall it lines.
19
Q
What are each of the layers of peritoneum sensitive to?
A
Parietal- Pressure, pain, laceration and temperature
Visceral- Stretch and chemical irritation
20
Q
Why does the visceral peritoneum have a poorly localised pain response?
A
The visceral peritoneum has the same autonomic nerve supply as the viscera it covers
21
Q
What is the peritoneal cavity?
A
A potential space between the parietal and visceral peritoneum. It normally only contains a small amount of lubricating fluid
22
Q
How can damage to the abdominal peritoneum occur?
A
Infection, Surgery, or injury
23
Q
What does intraperitoneal mean?
A
The organ is enveloped by a visceral peritoneum, which covers the organ both anteriorly and posteriorly.
24
Q
What are examples of intraperitoneal organs?
A
The stomach, liver, and spleen
25
What does retroperitoneal mean?
The organ is not associated with visceral peritoneum. They are only covered in parietal peritoneum, and that peritoneum only covers their anterior surface.
26
What are the primarily retroperitoneal organs?
Organs developed and remaining outside of the parietal peritoneum. The oesophagus, rectum and kidneys.
27
What are the secondarily retroperitoneal organs?
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.
28
Which of the abdominal viscera are retroperitoneal?
```
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
By TeachMeSeries Ltd (2020)
```
29
What is a mesentery?
A double layer of visceral peritoneum. It connects an intraperitoneal organ to (usually) the posterior abdominal wall. It provides a pathway for nerves, blood vessels and lymphatics to travel from the body wall to the viscera.
30
What is omentum?
Sheets of visceral peritoneum that extends from the stomach and proximal part of the duodenum to other abdominal organs
31
How many layers of visceral peritoneum are in the greater omentum?
4
32
Where does the greater omentum attach?
It descends from the greater curvature of the stomach and proximal part of the duodenum, then folds back up and attaches to the anterior surface of the transverse colon
33
What is the role of the greater omentum?
It has a role in immunity
34
How many layers of visceral peritoneum are in the lesser omentum?
2
35
Where does the lesser omentum attach?
To the lesser curvature of the stomach and the proximal part of the duodenum to the liver
36
What are the two parts of the lesser omentum?
The hepatogastric ligament (the flat, broad sheet) and the hepatoduodenal ligament (the free edge, containing the portal triad)
37
What is a peritoneal ligament?
A double fold of peritoneum that connects viscera together or connects viscera to the abdominal wall
38
What is in the foregut?
oesophagus, stomach, pancreas, liver, gallbladder and the duodenum (proximal to the entrance of the common bile duct).
39
What is in the midgut?
duodenum (distal to the entrance of the common bile duct) to the junction of the proximal two thirds of the transverse colon with the distal third.
40
What is in the hindgut?
distal one third of the transverse colon to the upper part of the anal canal.
41
What are the borders of the inguinal triangle?
Medial- Lateral border of the rectus abdominis muscle
Lateral- Inferior epigastric vessels
Inferior- Inguinal Ligament
42
What is a hernia?
The protrusion of an organ or fascia through the wall of a cavity that normally contains it.
43
What happens in a direct inguinal hernia?
Bowel herniates through a weakness in the inguinal triangle, and enters the inguinal canal. Bowel can then exit the canal via the superficial inguinal ring and form a lump in the scrotum or labia majora.
44
What happens in an indirect inguinal hernia?
Where bowel enters the inguinal canal via the deep inguinal ring
45
How many vertibrae are in the lumbar spine?
5
46
Describe the vertibral bodies of the lumabr spine
They are large and kidney-shaped. They are deeper anteriorly than posteriorly, producing the lumbosacral angle. The vertebral foramen is trianglular in shape.
ransverse processes are long and slender.
Articular processes have nearly vertical facets.
Spinous processes are short and broad.
Accessory processes can be found on the posterior aspect of the base of each transverse process. They act as sites of attachment for deep back muscles.
Mammillary processes can be found on the posterior surface of each superior articular process. They act as sites of attachment for deep back muscles.
47
Where are the two types of joint in the lumbar spine?
Between vertebral bodies
| Between vertebral arches
48
What are iliolumbar ligaments?
Fan-like ligaments radiating from the transverse processes of the L5 vertebra to the ilia of the pelvis
49
What is the cauda equina and where does it begin?
A bundle of lumar, sacral and coccygeal nerve roots. It begins at the level of L1
50
How many layers are in the abdominal fiscia?
Above the umbilicus- a single sheet of connective tissue
| Below the umbilicus- a superficial fatty layer, and the membranous layer
51
What is the linea alba?
A fibrous structure that extends from the xiphoid process of the sternum to the pubic symphysis
52
What are the attachments of the external oblique?
Originates from ribs 5-12, and inserts into the iliac crest and pubic tubercle
53
What are the functions of the external oblique?
Contralateral rotation of the torso
54
What is the innervation of the external oblique?
Thoracoabdominal nerves (T7-T11) and subcostal nerve (T12)
55
Which way do the fibres of external oblique run?
Inferomedially (hands into pockets)
56
What are the attachments of the internal oblique?
Originates from the inguinal ligament, iliac crest and lumbodorsal fascia, and inserts into ribs 10-12.
57
What are the functions of the internal oblique?
Bilateral contraction compresses the abdomen, while unilateral contraction ipsilaterally rotates the torso.
58
What is the innervation of the internal oblique?
Thoracoabdominal nerves (T7-T11), subcostal nerve (T12) and branches of the lumbar plexus.
59
In which direction do the fibres of the internal oblique run?
Superomedially
60
What are the attachments of the transversus abdominis?
Originates from the inguinal ligament, costal cartilages 7-12, the iliac crest and thoracolumbar fascia. Inserts into the conjoint tendon, xiphoid process, linea alba and the pubic crest.
61
What are the functions of the transversus abdominis?
Compressio of abdominal contents
62
What is the innervation of the transversus abdominis?
Thoracoabdominal nerves (T7-T11), subcostal nerve (T12) and branches of the lumbar plexus.
63
What are the attachments of the rectus abdominis?
Originates from the crest of the pubis, before inserting into the xiphoid process of the sternum and the costal cartilage of ribs 5-7.
64
What are the functions of the rectus abdominis?
As well as assisting the flat muscles in compressing the abdominal viscera, the rectus abdominis also stabilises the pelvis during walking, and depresses the ribs.
65
What is the innervation of rectus abdominis?
Thoracoabdominal nerves (T7-T11).
66
What are the attachments of the pyramidalis?
Originates from the pubic crest and pubic symphysis before inserting into the linea alba.
67
What are the functions of the pyramidalis?
It acts to tense the linea alba.
68
What is the innervation of pyramidalis?
Subcostal nerve (T12).
69
What are the vertical lines dividing the 9 abdominal regions?
The mid-clavicular lines
70
What are the horizontal lines dividing the 9 abdominal regions?
The transpyloric plane and the intertubercular plane
71
What are the 9 abdominal regions?
```
Right hypochondrium
Epigastrium
Left hypochondrium
Right flank
Umbilical
Left flank
Right groin
Pubic
Left groin
```
72
In which of the 9 abdominal areas is the liver in?
Mainly in the right hypochondrium and epigastric areas, and extending into the left hypochondrium
73
Describe the diaphragmatic surface of the liver
The anterosuperior surface of the liver. It is smooth and convex, fitting snugly beneath the curvature of the diaphragm. The posterior aspect of the diaphragmatic surface is not covered by visceral peritoneum, and is in direct contact with the diaphragm itself.
74
Describe the visceral surface of the liver.
The posteroinferior surface of the liver. With the exception of the fossa of the gallbladder and porta hepatis, it is covered in peritoneum. It is moulded by the shape of the surrounding organs, making it irregular and flat. It lies in contact with the right kidney, right adrenal gland, right colic flexure, transverse colon, first part of duodenum, gallbladder, oesophagus and the stomach.
75
Describe the falciform ligament
this sickle-shaped ligament attaches the anterior surface of the liver to the anterior abdominal wall and forms a natural anatomical division between the left and right lobs of the liver. The free edge of this ligament contains the ligamentum teres, a remnant of the umbilical vein.
76
Describe the coronary ligament
attaches the superior surface of the liver to the inferior surface of the diaphragm and demarcates the bare area of the liver The anterior and posterior folds unite to form the triangular ligaments on the right and left lobes of the liver.
77
Describe the triangular ligaments
The left triangular ligament is formed by the union of the anterior and posterior layers of the coronary ligament at the apex of the liver and attaches the left lobe of the liver to the diaphragm.
The right triangular ligament is formed in a similar fashion adjacent to the bare area and attaches the right lobe of the liver to the diaphragm.
78
What are the hepatic recesses?
Subphrenic spaces
Subhepatic space
Morison's pouch
79
What is Glisson's capsule?
The fibrous layer covering the liver
80
What are the four lobes of the liver?
Left
Right
Caudate
Quadrate
81
What is the porta hepatis?
A deep transverse fissure that seperates the caudate and quadrate lobes. It transmits all the vessels, nerves and ducts entering or leaving the liver with the exception of the hepatic veins
82
What is found in the portal triad?
Arteriole (A branch of the hepatic artery)
Venule (A branch of the hepatic porta vein)
Bile duct
Lymphatic vessels
Vagus nerve
83
What percentage of blood is from each of the hepatic veins?
25% is from the hepatic artery proper
| 75% is from the hepatic portal vein
84
What is the hepatic artery derived from?
The coeliac trunk
85
What do the hepatic veins drain into?
The inferior vena cava
86
What innervates the liver?
The parenchyma of the liver is innervated by the hepatic plexus which contains sympathetic (coeliac plexus), and parasympathetic (vagus nerve) fibres.
Glissons capsule is innervated by the branches of the lower intercostal nerves
87
What is the lymphatic drainage of the liver?
The anterior aspect of the liver drains into hepatic lymph nodes.
The posterior aspect of the liver drains into the phrenic and posterior mediastinal nodes
88
What are the three parts of the gallbladder?
Fundus (rounded, distal portion), Body (the largest part), neck (where it tapers to become continuous with the cystic duct)
89
Describe the route of bile down the biliary tree
Bile is secreted from the hepatocyte and drains via canaliculi, intralobular ducts and collecting ducts into the left and right hepatic ducts. These merge to form the common hepatic duct. This is then joined by the cystic duct which allows bile to flow in and out of the gall bladder. It is joined by the main pancreatic duct forming the heppatopancreatic ampulla (ampulla of Vater) which empties into the duodenum via the major duodenal papilla which is regulated by the sphincter of Oddi.
90
What is the storage capacity of the gall bladder?
30-50 ml
91
What is the arterial supply of the gallbladder?
The cystic artery- a branch of the right hepatic artery
92
What is the venous drainage of the gallbladder?
Cystic veins, which drain directly into the portal vein
93
What is the innervation of the gallbladder?
The coeliac plexus which carries sympathetic and sensory fibres, and the vagus nerve which delivers parasympathetic innervation
94
What is the lymphatic drainage of the gallbladder?
Lymph drains into the cystic lymph nodes, situated at the gallbladder neck. These empty into the hepatic lymph nodes and ultimately the coeliac lymph nodes
95
What is choleithiasis?
Uncomplicated gallstones
96
In which of the nine abdominal regions is the pancreas located?
Epigastrium and left hypochondrium region
97
What are the five parts of the pancreas?
```
Head
Uncinate process
Neck
Body
Tail `
```
98
Describe the route of the digestive enzyme precursors from the exocrine pancreas to the hepatopancreatic ampulla of Vater?
The intercalated ducts unite with draining adjacent lobules and drain into a network of intralobular collecting ducts which in turn drain into the main pancreatic duct. These then run the length of the pancreas and unites with the common bile duct, forming the hepatopancreatic ampulla of Vater
99
What is the arterial supply to the pancreas?
The splenic artery. The head is additionally supplied by the superior and inferior pancreaticoduodenal arteries which are branches of the gastroduodenal and superior mesenteric arteries respectively
100
What is the venous drainage of the pancreas?
The head is drained by the superior mesenteric branches of the hepatic portal vein. The pancreatic veins draining the rest of the pancreas do so via the splenic vein.
101
What is the lymphatic drainage of the pancreas?
The pancreas is drained by the lymphatic vessels that follow the arterial supply. They empty into the pancreaticosplenal nodes and the pyloric nodes, which in turn drain into the superior mesenteric and coeliac lymph nodes.
102
What are the causes of pancreatitis?
```
GET SMASHED
Gall stones
Ethanol
Trauma
Steroids
Mumps
Autoimmune
Scorpion stings
Hypertriglyceridema, hypercalcaemia, and hyperparathyroidism
ERCP
Drugs
```
103
What are the symptoms of pancreatitis?
Severe epigastric pain which often radiates to the back, nausea, vomiting, and diarrhoea
104
What are the roles of the spleen?
Blood filter, removing old red cells. Also both cell-mediated and humoral immune responses
105
What is the gastrosplenic ligament?
Anterior to the splenic hilum, connects the spleen to the greature curvature of the stomach
106
What is the splenorenal ligament?
Posterior to the splenic hilum, connects the hilum of the spleen to the left kidney. The splenic vessels and tail of the pancreas lie within the ligament.
107
What is the arterial supply to the spleen?
Mainly the splenic artery- arising from the coeliac trunk.
108
What is the venous drainage of the spleen?
The splenic vein. It combines with the superior mesenteric vein to form the hepatic portal vein.
109
What is the innervation of the spleen?
The coeliac plexus
110
What are the three major branches of the coeliac trunk?
Left gastric, splenic and common hepatic arteries
111
What does the proper hepatic artery give rise to?
The right gastric, right and left hepatic and cystic arteries
112
What are the branches of the gastroduodenal artery?
Right gastroepiploic and superior pancreaticicoduodenal
113
What are the major branches of the superior mesenteric artery?
Inferior pancreaticoduodenal artery
Jujunal and ileal arteries
Middle and right colic arteries
Ileocolic artery
114
What are the major branches of the inferior mesenteric artery?
Left colic artery
Sigmoid arteries
Superior rectal artery
115
What are the to anastomoses of the superior mesenteric artery?
Marginal artery and arc of Riolan
116
Approximately how long is the oesophagus?
25cm
117
At what levels does the oesophagus start and end?
C6-T11
118
What is the level of the oesophageal hiatus?
T10
119
What is peristalsis?
Rhythmic contractions of the muscles
120
Describe the oesophageal sphincter
The upper sphincter is an anatomical, striated muscle sphincter at the junction between the pharynx and oesophagus. It is produced by the cricopharyngeus muscle. Normally, it is constricted to prevent the entrance of air into the oesophagus.`
121
Describe the lower oesophageal Sphincter
The lower oesophageal sphincter is a physiological sphincter located in the gastro-oesophageal junction (junction between the stomach and oesophagus). The gastro-oesophageal junction is situated to the left of the T11 vertebra, and is marked by the change from oesophageal to gastric mucosa.
122
What are the four phenomena forming the lower oesophageal sphincter?
The oesophagus enters the stomach at an acute angle.
The walls of the intra-abdominal section of the oesophagus are compressed when there is a positive intra-abdominal pressure.
The folds of mucosa present aid in occluding the lumen at the gastro-oesophageal junction.
The right crus of the diaphragm has a “pinch-cock” effect.
123
What are the four physiological contrictions in the lumen of the oesophagus?
Arch of aorta
Bronchus
Cricoid Cartilage
Diaphragmatic hiatus
124
What is the arterial supply to the oesophagus?
Thoracic- Branches of the thoracic aorta and the inferior thyroid artery
Abdominal- Left gastric artery and left inferior artery.
125
What is the venous drainage of the oesophagus?
Thoracic- To the systemic circulation via branches of the azygous veins and inferior thyroid vein
Abdominal- to the portal system via left gastric vein and to the systemic circulation via the azygous vein
126
What is the innervation of the oesophagus?
The oesophageal plexus which is formed of the parasympathetic vagal trunks and sympathetic fibres from the cervical and thoracic sympathetic trunks
127
What is the lymphatic drainage of the oesophagus?
Superior third – deep cervical lymph nodes.
Middle third – superior and posterior mediastinal nodes.
Lower third – left gastric and celiac nodes.
128
What type of muscle is found in the oesophagus?
Superior third – voluntary striated muscle
Middle third – voluntary striated and smooth muscle
Inferior third – smooth muscle
129
What is Barrett's oesophagus?
The metaplasia of lower oesophageal squamous epithelium to gastric columnar epithelium. It is caused by chronic acid exposure due to a malfunctioning lower oesophageal sphincter. The most common symptom is a long-term burning sensation of indigestion.
130
What are the clinical features of oesophageal carcinomas?
Dysphagia
| Weight loss
131
In which of the nine anatomical regions is the stomach found in?
The epigastric and umbilical region
132
What are the four main anatomical divisions of the stomach?
Cardia- Surrounding the superior opening of the stomach
Fundus- The rounded portion superior to and left of the cardia
Body- The large central portion
Pylorus- The area connecting the duodenum to the stomach
133
Describe the greater curvature of the stomach
The long, convex, lateral border of the stomach. It is supplied by the short gastric arteries and the left gastro-omental arteries
134
Describe the lesser curvature of the stomach
The shorter, concave, medial surface of the stomach. It is supplied by the left gastric artery and right gastric branch of the hepatic artery
135
Describe the pyloric sphincter
It lies between the pylorus and the first part of the duodenum. It controls the exit of chyme. It is an anatomical sphincter, containing smooth muscle, which constricts to limit the discharge of the stomach contents.
136
What is the arterial supply to the stomach?
The celiac trunk and its branches. (inc right and left gastric arteries which astamose on the lesser curvature, and the right and left gastro-omental arteries which astamose on the greater curvature)
137
What is the venous drainage of the stomach?
Right and left gastric veins which drain into the hepatic portal vein, the short gastric vein, left and right gastro-omental veins drain into the superior mesenteric vein
138
What is the innervation of the stomach?
Parasympathetic nerve supply from the anterior and posterior vagal trunks (derived from the vagus nerve)
Sympathetic nerve supply from the T6-T9 spinal chord segments and passes to the coeliac plexus via the greater splanchnic nerve.
139
What is the lymphatic drainage of the stomach?
Lymphatic vessels travel with the arteries along curvatures. Lymph fluid drains into the gastric and gasto-omental lymph nodes found at the curvatures.
140
What are the three main causes of reflux disease?
Dysfunction of the lower oesophageal sphincter
Delayed gastric emptying
Hiatal hernia
141
What are the symptoms of GORD?
Dyspepsia, dysphagia, and an unpleasant sour taste in the mouth
142
What is a hiatus hernia?
When part of the stomach protrudes into the chest through the oesophageal hiatus in the diaphragm
143
Approximately how long is the small intestine?
6.5m
144
What are the three anatomical sections of the small bowel?
The duodenum
The jejunum
The ilium
145
What are the four parts of the duodenum?
Superior, descending, inferior and ascending
146
How is the superior part of the duodenum attached to the liver?
The hepatoduodenal ligament
147
Which part of the small bowel has the major duodenal papilla?
The descending duodenum
148
What is the sharp turn joining the aorta to the jejunum?
The duodenojejunal flexure
149
What is the suspensory muscle of the duodenum?
A slip of muscle located at the duodenojejunal junction. Contraction of this muscle widens the angle of the flexure and aids movement of the intestinal contents into the jejunum
150
What are the most common causes of duodenal ulcers?
Helicobacter pylori infection and chronic NSAID therapy
151
Where is the appendix found?
Attached to the posteromedial end of the cecum
152
How many main locations of the appendix are there?
7
153
What is the most common position of the appendix?
Retrocecal (behind the cecum)
154
What is the arterial supply of the appendix?
The appendicular artery (derived from the ileocolic artery, a branch of the superior mesenteric artery)
155
What is the venous drainage of the appendix?
The appendicular vein
156
What is the ileocecal valve?
A structure between the cecum and ilium which prevents reflux of the large bowel contents into the ileum during peristalsis and is thought to function passively
157
What is the arterial supply of the cecum?
The ileocolic artery, a branch of the superior mesenteric artery. It subsequently divides into anterior and posterior cecal arteries, which directly supply the cecum.
158
What is the venous drainage of the cecum?
The ileocolic vein, and empties into the superior mesenteric vein.
159
What is the innervation of the cecum and appendix?
The ileocolic branch of the superior mesenteric plexus
160
What is the lymphatic drainage of the cecum?
Lymph drains into the ileocolic lymph nodes
161
What are the four parts of the colon?
Ascending, transverse, descending and sigmoid
162
What is the right colic flexure (or hepatic flexure)?
The 90 degrees turn where the ascending colon meets the transverse colon
163
What is the left colic flexure (or splenic flexure)?
The 90 degrees turn where the transverse colon meets the descending colon.
164
How is the transverse colon attached to the diaphragm?
The phrenicocolic ligament
165
Which parts of the colon are retroperitoneal?
Ascending
| Descending
166
How long is the sigmoid colon?
Roughly 40cm
167
What are the paracolic gutters?
Two spaces between the ascending/descending colon and the posterolateral abdominal wall
168
What are omental appendices?
Small pouches of peritoneum, filled with fat, attached to the surface of the large intestine
169
What are teniae coli?
Three strips of muscle running longitudinally along the surface of the large bowel. They are called the mesocolic, free and omental coli.
170
What are haustra?
Sacculations in the wall of the bowel
171
What is the embryonic derivatives of the colon?
Ascending colon and proximal 2/3 of the transverse colon – derived from the midgut.
Distal 1/3 of the transverse colon, descending colon and sigmoid colon – derived from the hindgut.
172
What is the arterial supply to the ascending colon?
Two branches of the superior mesenteric artery; the ileocolic and right colic arteries.
173
What is the arterial supply to the transverse colon?
Right colic artery (from the superior mesenteric artery)
Middle colic artery (from the superior mesenteric artery)
Left colic artery (from the inferior mesenteric artery)
174
What is the arterial supply to the descending colon?
The left colic artery (a branch of the inferior mesenteric artery)
175
What is the arterial supply to the sigmoid colon?
The sigmoid arteries (branches of the inferior mesenteric artery)
176
What is the venous drainage of the ascending colon?
ileocolic and right colic veins, which empty into the superior mesenteric vein.
177
What is the venous drainage of the transverse colon?
middle colic vein, which empties into the superior mesenteric vein.
178
What is the venous drainage of the descending colon?
left colic vein, which drains into the inferior mesenteric vein.
179
What is the venous drainage of the sigmoid colon?
drained by the sigmoid veins into the inferior mesenteric vein.
180
What is the innervation of the colon?
Midgut-derived structures (ascending colon and proximal 2/3 of the transverse colon) receive their sympathetic, parasympathetic and sensory supply via nerves from the superior mesenteric plexus.
Hindgut-derived structures (distal 1/3 of the transverse colon, descending colon and sigmoid colon) receive their sympathetic, parasympathetic and sensory supply via nerves from the inferior mesenteric plexus:
Parasympathetic innervation via the pelvic splanchnic nerves
Sympathetic innervation via the lumbar splanchnic nerves.
181
What is the lymphatic drainage of the colon?
The lymphatic drainage of the ascending and transverse colon is into the superior mesenteric nodes. The descending colon and sigmoid drain into the inferior mesenteric nodes.
182
What are the two major flexures of the rectum?
Sacral flexure – anteroposterior curve with concavity anteriorly (follows the curve of the sacrum and coccyx).
Anorectal flexure – anteroposterior curve with convexity anteriorly. This flexure is formed by the tone of the puborectalis muscle, and contributes significantly to faecal continence.
183
What is the ampulla and its role?
The final segment of the rectum. It relaxes to accumualate and temporarily store faeces until defecation occurs.
184
What is the arterial supply to the rectum?
Superior rectal artery
Middle rectal artery
Inferior rectal artery
185
What is the venous drainage of the rectum?
Superior, middle, and inferior rectal veins. Superior rectal vein drains into the portal venous system, whilst the middle and inferior drain into the systemic venous system.
186
What is the innervation of the rectum?
Sympathetic nervous supply to the rectum is from the lumbar splanchnic nerves and superior and inferior hypogastric plexuses. Parasympathetic supply is from S2-4 via the pelvic splanchnic nerves and inferior hypogastric plexuses. Visceral afferent (sensory) fibres follow the parasympathetic supply.
187
What is the lymphatic drainage of the rectum?
The pararectal lymph nodes and the internal iliac lymph nodes.
188
What are the two anal sphincters?
Internal anal sphincter – surrounds the upper 2/3 of the anal canal. It is formed from a thickening of the involuntary circular smooth muscle in the bowel wall.
External anal sphincter – voluntary muscle that surrounds the lower 2/3 of the anal canal (and so overlaps with the internal sphincter). It blends superiorly with the puborectalis muscle of the pelvic floor.
189
What is the anorectal ring?
A muscular ring found at the junction of the rectum and the anal canal. It is formed by the fusion of the internal anal sphincter, external anal sphincter and puborectalis muscle
190
What is the pectinate line?
An irregular circle of anal valves. It divides the anal canal into upper and lower parts which differ in both structure and neurovascular supply.
