Raftery Abdo and Perineum Flashcards
(177 cards)
1
Q
How many folds of peritoneum are there below the umbilicus and what are they?
A
Three
Median umbilical fold - obliterated urachus
Medial umbilical fold - obliterated umbilical artery
Lateral umbilical fold - inferior epigastric artery
2
Q
What are the relations of the omental bursa (lesser sac)?
A
Front - lesser omentum, stomach
Above - superior recess whose anterior border is the caudate lobe of liver
Below - projects downwards to transverse mesocolon
Left - spleen, gastrosplenic and lienorenal ligaments
Right - opens into greater sac via epiploic foramen
3
Q
What are the relations of the epiploic foramen (Foramen of Winslow)?
A
Front - free edge of lesser omentum
Back - IVC
Above - caudate process of liver
Below - 1st part of duodenum
4
Q
What are the contents of the epiploic foramen?
A
Right - bile duct
Left - hepatic artery
Behind - portal vein
5
Q
What separates the right and left subphrenic spaces?
A
Falciform ligament
6
Q
What are the boundaries of the right subhepatic space (renal well of Rutherford Morrison)?
A
Above - liver with attached gallbladder
Below - duodenum
Behind - posterior abdominal wall, kidney
7
Q
What is the left subhepatic space?
A
Lesser sac
8
Q
What are the bones in the posterior abdominal wall?
A
Bodies of lumbar vertebrae
Sacrum
Wings of ilium
9
Q
What are the muscles in the posterior abdominal wall?
A
Posterior part of diaphragm
Psoas major
Quadratus lumborum
Iliacus
10
Q
What are important structures on the posterior abdominal wall?
A
Abdominal aorta IVC Kidneys Adrenal glands Lumbar sympathetic chain
11
Q
What is the origin of psoas major?
A
Transverse processes of L1-5 and sides of bodies and intervening discs from T12-L5 vertebrae
12
Q
Where does the psoas major insert?
A
Tip of lesser trochanter of femur
13
Q
What is the nerve supply of psoas major?
A
L2-3
14
Q
What are the actions of psoas major?
A
Flexion and medial rotation of extended thigh
15
Q
What important structures lies on psoas major?
A
IVC
Ureters
Gonadal vessels
16
Q
What lies in front of psoas major?
A
Retrocaecal or retrocolic appendix
Psoas/Cope’s sign = RLQ pain with flexion of right hip against resistance in appendicitis
17
Q
What is the origin of quadratus lumborum?
A
Iliolumbar ligament and adjacent portion of iliac crest
18
Q
Where does quadratus lumborum insert?
A
Medial half of lower border of 12th rib and by 4 small tendons into the transverse process of L1-4
19
Q
What are some anterior relations of quadratus lumborum?
A
Colon
Kidney
Subcostal, ilioinguinal and iliohypogastric nerves
20
Q
What is the origin of iliacus?
A
Greater part of iliac fossa extending into sacrum
21
Q
What is the insertion of iliacus?
A
Lateral aspect of tendon of psoas major onto lesser trochanter of femur
22
Q
What is the nerve supply of iliacus?
A
Branch of femoral nerve (L2-3)
23
Q
What are the anterior relations of abdominal aorta (from up to down)?
A
Lesser omentum Stomach Coeliac plexus Pancreas Splenic vein Left renal vein 3rd part of duodenum Root of mesentery Coils of small intestine Aortic plexus Peritoneum
24
Q
What are posterior relations of abdominal aorta?
A
Bodies of L1-4 vertebrae
Left lumbar veins
Cisterna chyli
25
What structures are found on the right side of the abdominal aorta?
IVC
Thoracic duct
Azygous vein
Right sympathetic trunk
26
What structures are found on the left side of the abdominal aorta?
Left sympathetic trunk
27
What are the branches of the abdominal aorta and their levels?
Anterior unpaired supplying abdominal viscera:
1. Coeliac axis - T12
2. SMA - L1
3. IMA - L3
Lateral paired:
1. Suprarenal - L1
2. Renal - L1-2
3. Gonadal (testicular/ovarian) - L2
Paired to parietes:
1. Inferior phrenic - T12
2. 4 lumbar arteries - L1-4
Terminal branches
1. Common iliac - L4
2. Median sacral - L4 (slightly above aortic bifurcation)
28
What are the branches of the coeliac axis?
Left gastric artery
Common hepatic artery
Splenic artery
29
What are the branches of the superior mesenteric artery?
Ileocolic
Middle colic
Right colic
30
What are the branches of the inferior mesenteric artery?
Left colic
| Superior rectal
31
What are the anterior relations of common iliac artery?
Peritoneum
Small intestine
Ureters
Sympathetic nerves
32
Which artery runs along the brim of the pelvis on the medial side of psoas major?
External iliac artery
33
Inferior epigastric artery is a branch of?
External iliac artery
| branch given off immediately before passing below inguinal ligament
34
Which structure passes backwards and downwards into the pelvis between the ureter (anteriorly) and internal iliac vein (posteriorly)?
Internal iliac artery
35
Where does the internal iliac artery divide into its anterior and posterior branches?
At the upper border of the greater sciatic notch
36
What do the branches of the internal iliac artery supply?
Pelvic organs
Perineum
Buttock
Anal canal
37
At which level does the common iliac veins join to form the inferior vena cava?
L5
38
At which level does the IVC pass through the diaphragm?
T8
39
What are the anterior relations of IVC?
```
Mesentery
3rd part of duodenum
Pancreas
1st part of duodenum
Portal vein
Posterior surface of liver
Diaphragm
Arteries (from top to bottom): hepatic, right testicular, right colic, right common iliac
```
40
What are the posterior relations of IVC?
```
Vertebral column
Right crus of diaphragm and psoas major
Right sympathetic trunk
Right renal artery
Right lumbar arteries
Right suprarenal arteries
Right inferior phrenic artery
Right suprarenal gland
To the left: aorta
```
41
What are the tributaries of IVC?
```
Lumbar branches
Right gonadal vein
Right and left renal veins
Right suprarenal vein
Phrenic vein
Hepatic vein
```
42
Where does the lumbar sympathetic chain start?
Deep to the medial arcuate ligament of the diaphragm as a continuation of the thoracic sympathetic chain
43
What are the positions of the lumbar vessels relative to the lumbar sympathetic chain?
Lumbar arteries - lie deep to chain
| Lumbar veins - may cross superficial to it
44
What are the branches of the lumbar sympathetic chain?
```
Plexuses around abdominal aorta
Hypogastric plexus (presacral nerves) to supply the pelvic viscera distributed along internal iliac artery and its branches
```
45
What causes failure of ejaculation after resection of AAA or extensive pelvic dissection?
Removal of aortic and hypogastric plexuses
46
What may lumbar sympathectomy be carried out for?
Plantar hyperhidrosis or vasospastic conditions
Usually the 2nd-4th ganglia are excised with the intermediate chain
47
Muscles of the pelvic floor
Levator ani
| Coccygeus
48
Muscles of the pelvic wall
```
Piriformis (on front of sacrum)
Obturator internus (on lateral wall of true pelvis)
```
Both act on femur, described with LL muscles
49
Origins of levator ani
Back of body of pubis
Ischial spine
Between these from the fascia covering obturator internus along a thickening between the above 2 points
50
Insertion of levator ani
Perineal body - forms a sling around prostate (levator prostatae) or vagina (sphincter vaginae)
Puborectalis (deep part of anal sphincter at anorectal ring) - sling around rectum and anus
Sides of coccyx and a median fibrous raphe stretching between the apex of the coccyx and anorectal junction
51
Nerve supply of levator ani
Pelvic surface - perineal branch of S4
Perineal surface - branch of inferior rectal and perineal division of pudendal nerve (S2-3)
52
Actions of levator ani
Principal support of pelvic floor
Support pelvic viscera
Resist downward pressure of abdominal muscles
Sphincter action on rectum and vagina
Increase intra-abdominal pressure during defecation, micturition, parturition
53
What is the coccygeus?
A small triangular muscle behind and in the same plane as levator ani
54
Origin of coccygeus
Ischial spine
55
Insertion of coccygeus
Side of coccyx and lowest part of sacrum
| Same attachments as sacrospinous ligament
56
Nerve supply of coccygeus
Perineal branch of S4
57
Action of coccygeus
Hold coccyx in natural forwards position
Pelvic fascia
Parietal pelvic fascia - strong membrane covering muscles of pelvic wall and attached to bones at margins of muscles, over fixed or non-distensible structures (e.g. prostate)
Visceral pelvic fascia - loose and cellular over moveable structures (e.g. levator ani, bladder, rectum)
58
Triangles of the perineum
```
Urogenital triangle (anterior perineum)
Anal triangle (posterior perineum)
```
59
What is the urogenital triangle?
Triangle formed by the ischiopubic inferior rami and line joining the ischial tuberosities passing just in front of anus
60
What is the perineal membrane?
Inferior fascia of the urogenital diaphragm - a strong fascial sheath attached to the sides of the urogenital triangle
61
Contents of deep perineal pouch
```
External urethral sphincter (striated muscle fibres surrounding membranous urethra)
Bulbourethral glands (of Cowper) - ducts pierce perineal membrane to open into bulbous ducts
```
62
Relations of the external urethral sphincter
Below - perineal membrane
| Above - indefinite layer of fascia i.e. superior fascia of urogenital diaphragm
63
Contents of superficial perineal pouch
Male:
1. Bulb of penis attached to undersurface of perineal membrane (bulbospongiosus covers corpus spongiosum)
2. Crura of penis attached at angle between insertion of perineal membrane and ischiopubic rami (each crus surrounded by ischiocarnous muscle)
3. Superficial transverse perineal muscle running transversely from perineal body to ischial ramus
64
What is the perineal body?
Fibromuscular nodule lying in the midline between anterior and posterior perineum
65
Attachments of perineal body
Anal sphincter
Levator ani
Bulbospongiosus
Transverse perineal muscle
66
What is the anal triangle?
Triangular area lying between ischial tuberosities on each side and coccyx
67
Contents of anal triangle
Anus and its sphincters
Levator ani
Ischiorectal fossa
68
What is the ischiorectal fossa?
Space between the anal canal and side wall of pelvis
69
Boundaries of ischiorectal fossa
Medial - fascia over levator ani, external anal sphincter
Lateral - fascia over obturator internus
Front - extends forwards as prolongation deep to urogenital diaphragm
Back - limited by sacrotuberous ligaments and origin of gluteus maximus from this ligament
70
What lies in the pudendal canal (of Alcock)?
Internal pudendal vessels and nerve
71
What is the pudendal canal (of Alcock)?
Tunnel of fascia continuous with fascia overlying the obturator internus
72
Parts of penis
Root
Body
Glans
73
Attachments of root of penis
Perineal membrane
Pubic rami by crura
Symphysis pubis by suspensory ligament
74
What does the body of the penis comprise?
Corpus cavernosum
| Corpus spongiosum
75
How is corpus cavernosum attached to the pubic symphysis?
By a suspensory ligament
76
Parts of male urethra (20cm long)
Prostatic
Membranous
Spongy
77
Layers/coverings of the testis
Scrotal skin
Dartos fascia and muscle
External spermatic, cremaster muscle in cremasteric fascia, internal spermatic fascia
Parietal and visceral layers of tunica vaginalis
Tunica albuginea
78
Blood supply of testicles
Testicular artery arising from aorta at level of renal vessels
79
Origin of blood supply of vas deferens and epididymis
Artery to the vas from inferior vesical branch of internal iliac artery
80
Venous drainage of testis
Pampiniform plexus of veins which become the testicular vein at deep inguinal ring
81
Drainage of testicular veins
Right testicular vein into IVC, left into left renal vein
82
Lymphatic drainage of testis
Accompany testicular veins into para-aortic nodes
83
At which level does the testis arise from on the posterior abdominal wall?
L2/3
84
How may a rapidly developing varicocoele be a presenting sign of tumour of left kidney?
Tumour of left kidney may invade the left renal vein, blocking the drainage of left testicular vein into the renal vein
85
Where does the vas deferens join the seminal vesicle ducts to form the common ejaculatory duct?
At the most superior and posterior aspect of the prostate gland
86
What does the common ejaculatory duct become?
Traverses the prostate to open into the prostatic urethra at the verumontanum on either side of the utricle
87
Start and end points of oesophagus
From lower border of cricoid cartilage (C6) to cardiac orifice of stomach (T11)
88
Parts of oesophagus
Cervical
Thoracic
Abdominal
89
Relations of cervical oesophagus
Anterior - trachea, thyroid
Posterior - lower cervical vertebrae, prevertebral fascia
Left - left common carotid artery, inferior thyroid, subclavian artery, thoracic duct
Right - right common carotid artery, recurrent laryngeal nerves that lie on either side in the groove between trachea and oesophagus
90
Where are the vagus nerves in relation to the thoracic oesophagus?
2 vagus nerves form a plexus on the surface of the oesophagus in the posterior mediastinum
Left vagus - anterior
Right vagus - posterior
91
Relations of the thoracic oesophagus
Anterior - left common carotid artery, trachea, left main bronchus, pericardium (separating it from left atrium and diaphragm)
Posterior - thoracic vertebrae, thoracic duct, hemiazygous vein, descending aorta below
Left - left subclavian artery, aortic arch, left vagus nerve and recurrent laryngeal, thoracic duct, left pleura
Right - right pleura, azygous vein
92
Where does the abdominal oesophagus lie?
In the groove on the posterior surface of the left lobe of liver with left crus of diaphragm behind
93
Blood supply of oesophagus
Cervical - inferior thyroid arteries
Thoracic - branches of aorta
Abdominal - left gastric and inferior phrenic arteries
94
Venous drainage of oesophagus
Cervical - inferior thyroid veins
Thoracic - azygous veins
Abdominal - azygous veins (systemic), partly to left gastric veins (portal)
95
Nerve supply of oesophagus
Upper 1/3 - parasympathetics via recurrent laryngeal nerve, sympathetics from middle cervical ganglion via inferior thyroid artery
Lower 2/3 (below root of lung) - vagus and sympathetics nerves contribute to oesophageal plexus
96
Layers of oesophagus
Mucous membrane lined by non-keratinised stratified squamous epithelium
Submucosa
Muscular layers - inner circular and outer longitudinal muscles
Muscularis externa upper 1/3 - striated muscle
Lower 2/3 - smooth muscle causing peristalsis
Adventitia
Outer layer of loose connective tissue
97
Lymphatic drainage of oesophagus
Cervical - deep cervical nodes
Thoracic - mediastinal nodes
Abdominal - gastric nodes
98
Surfaces of the stomach
Anterior
| Posterior
99
Curvatures of the stomach
Greater
| Lesser
100
Orifices of the stomach
Cardia
| Pylorus
101
What is the name of the notch that marks the junction of the body with pyloric antrum along the lesser curve?
Incisura angularis
102
What is attached to the lesser and greater curves of the stomach?
Lesser and greater omentum respectively
103
What marks the junction of the pylorus with the duodenum?
Constant prepyloric vein of Mayo, which crosses it vertically
104
Relations of the stomach
Anterior (left to right) - diaphragm, abdominal wall, left lobe of liver
Posterior - separated from diaphragm, aorta, pancreas, spleen, left kidney and suprarenal gland, transverse mesocolon and colon by lesser sac of peritoneum
105
Arterial supply of stomach
Left gastric artery (from coeliac axis) - runs along lesser curve and anastomoses with right gastric branch of common hepatic artery
Right gastroepiploic artery (from gastroduodenal branch of hepatic artery) - anastomoses along greater curve with left gastroepiploic artery (from splenic artery)
Short gastric arteries (from splenic artery)
106
Venous drainage of stomach
Follows arteries, into the portal vein
107
Lymphatic drainage of stomach
Cardiac area - drains along left gastric artery to coeliac nodes
Area supplied by splenic artery - drains via nodes accompanying that artery to LN at hilum of spleen then to those along upper border of pancreas, eventually to coeliac nodes
Rest of stomach:
1. Via branches of hepatic artery through nodes along lesser curve to coeliac nodes
2. Through nodes along right gastroepiploic vessels to subpyloric nodes, then to coeliac nodes
108
Nerve supply of stomach
Anterior vagus nerve close to oesophageal wall - gives off hepatic branch and pyloric branch to pyloric sphincter
Posterior vagus nerve further from oesophageal wall - gives off coeliac branch passing to coeliac axis before sending a gastric branch to posterior surface of stomach
Gastric divisions of both vagi (nerves of Latarjet) reach the stomach at the cardia and descend along the lesse curve between the anterior and posterior peritoneal attachments of the lesser omentum
109
What is the surface of gastric mucosa covered by?
Columnar epithelial cells which secrete mucus and alkaline fluid to protect the epithelium from mechanical injury and gastric acid
110
What are the 3 areas of gastric mucosa?
Cardiac gland via area gastro-oesophageal junction - contains mucus-secreting cells
Acid-secreting region (oxyntic gland area) - contains parietal (oxyntic) cells and chief (zymogen) cells
Pyloric end area (distal 30% of stomach) - contains 'G' cells producing gastrin with mucus-secreting cells
111
In a retrograde spread of gastric carcinoma, what can happen with regards to the lymphatic drainage?
Spread may occur into the hepatic LNs at porta hepatis - enlargement of these nodes may cause external compression of bile ducts resulting in obstructive jaundice
112
Contents of femoral triangle
```
(Medial to lateral)
Femoral vein
Femoral artery
Femoral nerve
Deep and superficial inguinal LNs
Lateral cutaneous nerve
Great saphenous vein
Femoral branch of genitofemoral nerve
```
113
In the lesser pelvis, where does the obturator nerve lie?
Lateral to the internal iliac vessels and ureter
Joined by the obturator vessels lateral to the ovary and ductus deferens
114
What does the obturator nerve supply?
Medial compartment of thigh
| Muscles: external obturator, adductor longus/brevis/magnus (lower part by sciatic nerve), gracilis
115
What does the cutaneous branch of the obturator nerve supply?
Note: cutaneous branch is often absent.
When present, it passes between gracilis and adductor longus near middle part of thigh.
Supplies skin and fascia of distal 2/3 of medial aspect.
116
What is the obturator canal and its contents?
Connects the pelvis and thigh.
Contains: obturator artery and vein, nerve which divides into anterior and posterior branches.
117
What is the spermatic cord formed by?
Vas deferens
118
Layers of spermatic cord and their origins
External spermatic fascia - external oblique aponeurosis
Cremasteric fascia - internal oblique aponeurosis
Internal spermatic fascia - transversalis fascia
119
Contents of the spermatic cord
3 arteries - testicular (from AA), cremasteric (from inferior epigastric), artery to vas deferens (from inferior vesical, anterior division of internal iliac artery)
3 nerves - genital branch of genitofemoral nerve (to cremaster), sympathetic nerves (lies on arteries), ilioinguinal nerve (lies on cord, not within)
3 others - pampiniform plexus veins (drain to R/L testicular vein), vas deferens, lymphatics (to lumbar and para-aortic nodes)
120
Arterial supply of scrotum
Anterior and posterior scrotal arteries
121
Lymphatic drainage of scrotum
Inguinal lymph nodes
122
Innermost layer of scrotum
Parietal layer of tunica vaginalis
123
Lymphatic drainage of testes
Para-aortic nodes
124
Where does the iliacus muscle lie?
Posterior to the femoral nerve in femoral triangle
125
Where does the femoral sheath lie?
Anterior to the iliacus and pectineus muscles
126
Femoral nerve root values
L2-4
127
What does the femoral nerve innervate?
Pectineus
Sartorius
Quadriceps and rectus femoris
Vastus lateralis/medialis/intermedius
128
Branches of femoral nerve
Medial and intermediate cutaneous nerves of thigh
| Saphenous nerve
129
Which muscle does the femoral nerve penetrate?
Psoas major
130
How does the femoral nerve exit the pelvis?
By passing under the inguinal ligament to enter the femoral triangle
131
What is the location of femoral nerve relative to the femoral artery and vein?
Lateral to femoral artery and vein
132
Posterior relations of ascending colon
Iliacus
Quadratus lumborum
Perirenal fascia over lateral aspect of kidney
133
How is the transverse colon attached to the anterior border of pancreas?
By the transverse mesocolon
134
Relations of transverse colon
Anterior - greater omentum
Posterior - kidneys, 2nd part of duodenum, pancreas, small intestine
Superior - liver, gallbladder, greater curvature of stomach, spleen
Inferior - small intestine
135
What lies between the splenic flexure and diaphragm?
Phrenicocolic ligament, a fold of peritoneum
136
Relations of descending colon
Anterior - small intestine
| Posterior - Left kidney, quadratus lumborum, iliacus
137
Which structures does the root of sigmoid colon cross over?
External iliac vessels
| Left ureter
138
What are taenia coli?
3 flattened bands of longitudinal muscle passing from caecum to rectosigmoid and converging at base of appendix
139
What are appendices epiploicae?
Fat-filled tags scattered over the surface of the colon, most numerous in sigmoid colon (absent in appendix, caecum, rectum)
140
Commonest positions of appendix
Retrocaecal - 75%
Pelvic - 20%
Preileal or postileal - 5%
141
Arterial supply of appendix
Appendicular artery (from ileocolic artery)
142
Start and end points of rectum
~12cm long, starts anterior to 3rd segment of sacrum and ends ~2.5cm in front of coccyx
143
What is the transition between sigmoid and rectum marked by?
Disappearance of taenia coli
144
Extraperitoneal parts of rectum
Upper 1/3 - posterior
Middle 1/3 - posterior and lateral
Lower third - whole thing, lie below pelvic peritoneum
145
What is the extraperitoneal rectum surrounded by?
Mesorectal fat containing lymph nodes
Note: this layer is removed during rectal cancer surgery (total mesorectal excision)
146
Fascial layers surrounding rectum
Denonviliers fascia - anterior (prostate)
| Waldeyers fascia - posterior (sacrum)
147
Lateral inflexions of rectum
Left, right then left
| Each inflexion is capped by valve of Houston
148
Relations of rectum
Anterior (M) - rectovesical pouch, bladder, prostate, seminal vesicles
Anterior (F) - rectouterine pouch (Douglas), cervix, vaginal wall
Posterior - sacrum, coccyx, middle sacral artery, lower sacral nerves
Lateral - levator ani, coccygeus
149
Arterial supply of rectum
Superior rectal artery (from IMA) - whole rectum and upper half of anal canal
Middle rectal artery (from internal iliac) - small, only muscle coats of rectum
Inferior rectal artery (from internal pudendal) - lower half of anal canal
150
Venous drainage of rectum above vs below dentate line
Above - superior rectal vein (portal venous system)
Below - inferior rectal vein (systemic)
Note: site of portosystemic anastomosis
151
Lymphatic drainage of rectum above vs below dentate line
Above dentate line - mesorectal nodes along superior rectal vessels draining into internal iliac nodes
Below dentate line - superficial inguinal nodes
152
Epithelium above vs below dentate line
Above - columnar (adenocarcinoma
Below - non-keratinised stratified squamous (SCC) (until Hilton's white line where anal verge becomes continuous with perianal skin containing keratinised epithelium)
153
Embryological origin above vs below dentate line
Above - endoderm
Below - ectoderm
154
Arterial/venous supply above vs below dentate line
Above - superior rectal
Below - middle and inferior rectal (venous only inferior)
155
Nerve supply above vs below dentate line
Above - inferior hypogastric plexus (autonomic), not sensitive to pinprick
Below - inferior rectal nerves (somatic), sensitive to pinprick (relevant when injecting haemorrhoids)
156
At which vertebral level does the left colon become the sigmoid?
L3-4
157
What is the name of the artery that forms as a result of anastomoses between branches of SMA and IMA along length of colon?
Marginal artery (of Drummond) - from right colon
Weakest near splenic flexure. Can cause ischaemic colitis.
Contribution from the marginal artery becomes significant when IMA is surgically divided (e.g. during AAA repair).
158
Position of rectal veins
1 on left, 2 on right
This explains the 3, 7 and 11 o'clock positions of haemorrhoids when anal canal is viewed with patient in lithotomy position.
159
Where do the efferent vessels from nodes near origins of SMA and IMA drain into?
Cisterna chyli
160
What can be found at the midpoint of the anal canal?
Vertical columns in the mucosa (columns of Morgagni)
161
What can be found at the distal end of the vertical columns in the anal canal?
Valve-like folds (anal valves of Ball)
162
Muscles of anal sphincters
Internal anal sphincter - smooth muscle continuous above with circular muscle of rectum, surrounds upper 2/3 of rectum, supplied by sympathetic nerves
External - striated muscle that surrounds the internal anal sphincter but extends further distally
163
Parts of external anal sphincter
3 parts:
- subcutaneous
- superficial, attached to coccyx behind and perineal body in front
- deep, continuous with puborectalis of levator ani
164
What is the anorectal ring?
The deep part of external anal sphincter where it blends with levator ani together with internal sphincter
Note: anorectal ring is palpable with finger in anal canal where it forms a ring, immediately above which the finger enters the ampulla of the rectum
165
What is the subcutaneous part of the external anal sphincter traversed by?
Fan-shaped expansion of longitudinal muscle fibres of anal canal
166
Nerve supply of external anal sphincter
Inferior rectal branch of pudendal nerve (S2-3)
Perineal branch of S4
167
Relations of 1st part of duodenum
Anterior - liver, gallbladder
| Posterior - portal vein, CBD, gastroduodenal artery (IVC behind all these)
168
Relations of 2nd part of duodenum
Anterior - transverse colon
| Posterior - right kidney and ureter
169
Relations of 3rd part of duodenum (longest part, ~10cm)
Anterior - root of mesentery, superior mesenteric vessels
| Posterior - IVC, aorta, L3 vertebra
170
How may the DJ flexure be identified during surgery?
| At DJ flexure, small intestine leaves posterior abdo wall and acquires a mesentery
By presence of suspensory ligament of Treitz - a peritoneal fold descending from the right crus of diaphragm to termination of duodenum
171
Arterial supply of duodenum
Superior pancreaticoduodenal artery (from gastroduodenal)
Inferior pancreaticoduodenal (from SMA)
These 2 arteries lie in the curve between duodenum and head of pancreas, supplying both structures
172
Average length of small intestine
6 metres
173
Length of mesentery of small intestine
About 15cm, attached across posterior abdominal wall
174
Start and end points of small intestine
Starts at DJ flexure to the left of L2 vertebra, passes obliquely downwards to right sacroiliac joint
175
Relations of root of mesentery of small intestine
```
(Left to right)
3rd part of duodenum
Aorta
IVC
Right psoas major
Right ureter
Right gonadal vessels
Right iliacus
```
176
Contents of mesentery of small intestine
Superior mesenteric vessels (enter mesentery anterior to 3rd part of duodenum)
LNs draining small intestine
Autonomic nerve fibres
177
How do you distinguish between jejunum and ileum at surgery?
Jejunum has a thicker wall due to valvulae conniventes or plicae circularis (i.e. circular folds of mucosa) - larger and more numerous than in ileum
Jejunum has greater diameter
Final straight arteries to ileum shorter and more numerous than in jejunum
Mesentery becomes thicker and more fat-laden from above downwards
Jejunum most likely to be found at/above level of umbilicus while ileum tends to lie below umbilicus in the hypogastrium and pelvis
