📖MRCS On The Go 👣/😎Free Notes/
🍫Paper 1 - Anatomy: Abdomen
🍫
Paper 1 - Anatomy: Abdomen
👩‍💻
Kindly note that this is just a brief preview of our MRCS Part A notes. You will be granted access to the full version upon subscribing.
😌
Please note that some of the text might be misaligned and the hyperlinks might not be working correctly due to the website’s format. Rest assured that the original notes when viewed on your browser (on any device) do not have such issues. Click the link here for a more accurate view of our Paper 1 - Anatomy: Abdomen sample!
 

Table of Contents

  • Arteries of the GIT - Celiac trunk, SMA, IMA; Abdominal aorta; IVC; Internal iliac artery
  • Portal vein; Stomach; Lesser omentum; Lesser sac of peritoneum
 
  • Duodenum; Jejunum and Ileum
  • Large intestine; Appendix; Cecum
  • Spleen; Pancreas; Liver; Extra-hepatic biliary passage; Kidney; Adrenal glands
  • Urethra; Bladder; Ureter
  • Posterior abdominal wall; Lumbar plexus
  • Rectum; Anal sphincter; Prostate gland; Uterus; Ischiorectal fossa and Pudendal canal
 

High-yield / Revision Questions

Tricky Q’s: 🌟
Q: Which of the following is true about the spleen? - Hematopoiesis in normal individual; Contains macrophages; Primary lymphoid organ; Contains medullary sinuses
  • Ans: Contains macrophages
  • Note that: - Hemopoiesis occurs in spleen in pediatric population - Medullary sinuses are found in LNN - Spleen is a secondary lymphoid organ – (bone marrow and thymus are primary lymphoid organ)
Q: At which level and surface anatomy of the abdomen is the gallbladder palpated? - Subcostal and linea semilunaris at mid-axillary line; Fourth ICS at mid-clavicular line; At junction of right costal margin and linea semilunaris; Subcostalmargin and mid-axillary line; Xiphoid process
  • Ans: At junction of right costal margin and linea semilunaris
 
Q: What structure is present anterior to the right adrenal gland?
  • IVC
      • Observe that the IVC and R-adrenal gland are in close proximity.
Q: What structure is present anterior to head of pancreas?
  • Pylorus of the stomach
      • Observe that the stomach pylorus is located anteriorly to pancreas head.
Q: What structure is felt on DRE, at 4cm posterolateraly from the anal verge?
  • Puborectalis muscle
Lymphatic drainage of the abdominal structures 🌟
LD of scrotum
  • superficial inguinal LNN
LD of testis
  • para-aortic LNN
LD of prostate
  • internal iliac LNN (memory aid: "prostate is inside → internal iliac")
LD of rectum (2)
Superior to dentate line
  • Mesorectal LNN
Inferior to dentate line
  • Superficial inguinal LNN
LD of ovaries
  • Para-aortic LNN
LD of uterus
uterine fundus
  • para-aortic LNN mostly; tho, some may drain into inguinal LNN
uterine body
  • Internal iliac LNN ("for organs that are located more posteriorly" since uterus is behind bladder..)
Abdominal Embryological Q’s: 🌟
Q: From which embryological structure is the ureter derived? - Uranchus; Cloaca; Vitello-intestinal duct; Mesonephric duct; None of the above
  • Ans: Mesonephric duct
    • The ureter develops from an outpouching that arises from the mesonephric duct.
Q: From which embryological structure is the pancreas derived?
  • Ans: Ventral and dorsal endodermal outgrowths of the duodenum
      • Note its embryological development: 🌠 (for part B) 1. Pancreas first appears at 5wk gestation as two outpouchings from endodermal lining of duodenum → known as ventral and dorsal buds. 2. At 6-7wks, buds continue to grow and the ventral bud slowly rotates dorsally. 3. The rotation is complete when the ventral bud is now present dorsally, below the dorsal bud. 4. At 8wk, fusion takes place, where ventral bud fuses with dorsal bud to form the pancreas - the ventral bud becomes uncinate process + lower head of pancreas (both draining thru main duct of Wirsung); a small remnant of dorsal duct may persist to form accessory duct of Santorini 5. Interestingly, when fusion takes place, superior mesenteric vessels become trapped; hence, they lie anteriorly to uncinate process but posteriorly to pancreatic neck 🌠
Q: The appendix is derived from which of the following embryological structures? - Vitello-intestinal duct; Urachus; Foregut; Midgut; Hindgut
  • Ans: Midgut - which explains why early appendicitis manifests as periumbilical pain
 
 
[more high-yield Q’s and tips in our notes]

Muscles of the Anterior abdominal wall

Image of the layers of anterolateral abdominal wall
Deep → Superficial: Extraperitoneal fat → Transversalis fascia → Muscular layer (lateral part(3mm.) vs. medial part(2mm.)) - Lat: Transversus abdominis, Internal oblique, External oblique; Med: Rectus abdominis and pyramidalis muscle.
6 Important points to note re: Layers of anterolateral abdominal wall 🌟
1. Rectus sheath is formed by ~(3) aponeuroses; together they encapsulate ~?:
  • Aponeuroses of transversus abdominis, external oblique and internal oblique muscles
  • These aponeuroses encapsulate the medial abdominal muscles - rectus abdominis & pyramidalis muscles
2. Two holes are present within the anterior abdominal walls - they are ~(2):
Deep (or internal) inguinal ring - present in ~fascia:
  • Transversalis fascia
Superficial (or external) inguinal ring - present in ~:
  • External oblique fascia
3. A canal connects these two holes, which is known as ~:
  • Inguinal canal
4. The lower border of the external oblique aponeurosis gives rise to the ~(structure):
  • Inguinal ligament
5. The conjoint tendon is formed by the fusion of (2) aponeuroses; it makes up the ~ and the ~ of the inguinal canal:
  • Internal oblique
  • Transversus abdominis
  • It makes up the roof and posterior wall of the inguinal canal
6. R and L rectus abdominis muscles fuse together in the midline to form ~(structure), and the lateral border of the rectus abdominis gives rise to ~(structure):
  • Linea alba
  • Linea semilunaris
 

Inguinal ligament🕺

It is the lower free border of the ~aponeurosis 🌟
  • External oblique aponeurosis
It attaches to~:
Laterally
  • The anterior superior iliac spine (ASIS)
Medially
  • Pubic tubercle
 
[more high-yield details in our notes]
 

Inguinal canal 🌟

→ an oblique passage thru the lower part of the anterior abdominal wall muscles
The inguinal canal contains:
In males
  • Spermatic cord
In females
  • Round ligament of the uterus
In both sexes = (~nerve)
  • Ilioinguinal nerve - hence, ilioinguinal nerve entrapment is often a cause of neuropathic pain following inguinal hernia surgery!
Begins at ~ring:
Deep (internal) inguinal ring - which is an opening in the ~aponeurosis:
Transversalis fascia - this ring is ~(location):
  • located half an inch above the mid-point of the inguinal ligament
Ends at ~ring:
Superficial (external) inguinal ring - it is a triangle opening in the ~aponeurosis:
External oblique aponeurosis - this ring is ~(location):
  • Just above and lateral to the pubic tubercle
 
Image of inguinal canal boundaries
^Note that the blank space in the middle = inguinal canal
Ant = External oblique Sup = Internal oblique + Transversus abdominis (forming Conjoint tendon, written in black, which attaches to pubic tubercle)
Inf / Floor = Inguinal ligament (note it is also derived from EO)
Post = Transversalis fascia
Boundaries of the inguinal canal: 🌟
Anterior wall - first (2)~:
  • External oblique aponeurosis
  • Internal oblique aponeurosis
Posterior wall (2):
  • Transversalis Fascia - lateral two-thirds of posterior wall
  • Conjoint Tendon (note that it is made of the fusion of internal oblique and transversus abdominis aponeuroses) - medial one-third of posterior wall
Roof (1)
  • (arching fibers of) Conjoint tendon (note that it is made of the fusion of internal oblique and transversus abdominis aponeuroses)
Floor (1)
  • Inguinal ligament
 

Inguinal triangle (Hesselbach triangle) 🔼

Image of inguinal triangle
Boundaries of the inguinal triangle: 🌟
Medially
  • Lateral border of rectus abdominis muscle
    • specifically the linea semilunaris (which is the lateral border of rectus sheath)
Laterally
  • Inferior epigastric vessels
Inferiorly
  • Inguinal ligament
 
[more high-yield details in our notes]
 

Inguinal hernia 🌟

→ two types: Direct vs. Indirect inguinal hernia
Image of direct and indirect inguinal hernias:
In direct hernia, the defect occurs ~(location):
In the inguinal triangle - this is ~relative to the inferior epigastric artery:
Medial to the inferior epigastric artery; note its association with the scrotum:
  • It never enters the scrotum!
In indirect hernia, the defect occurs ~(location):
Through the deep inguinal ring - this is ~relative to the inferior epigastric artery:
Lateral to the inferior epigastric artery; note its a/w the scrotum:
  • It may sometimes enter the scrotum
 
Tricky Q’s re: Hernias and anatomical landmarks: 🌟
Q: How does a surgeon identify the superficial inguinal ring? Via ~landmark:
  • Presence of Intercrural fibers
      • Intercrural fibers act as a visible landmark for the superficial inguinal ring 🌠
Q: A 25yo man presents with a painful, tender swelling inferior and lateral to his right pubic tubercle - what hernia does he have?
  • Femoral hernia
      • Note that location of femoral hernia is inferior to the pubic tubercle!
Q: A 19yo man presents with an indirect inguinal hernia. He undergoes surgery. The deep inguinal ring is exposed, where a retractor is held at its medial aspect. What structure lies directly under the retractor? - Ureter; Inferior epigastric artery; Internal iliac vein; Femoral artery; Lateral border of rectus abdominis
  • Ans: Inferior epigastric artery
  • Recap boundaries of the deep inguinal ring:
    • Superolaterally → Transversalis fascia
    • Inferomedially → Inferior epigastric artery
  • Note that the deep inguinal ring is closely related to the inferior epigastric artery, which forms part of the structure = Hesselbach’s triangle.
 

Rectus sheath

→ An aponeurosis that envelops the rectus abdominis and pyramidalis muscles
Its formation differs depending on location: 🌟
Above the xiphoid process
  • Anterior wall: External oblique aponeurosis
  • Posterior wall: 5th-7th costal cartilages
Between xiphoid process & arcuate line
  • Anterior wall: External oblique aponeurosis and (anterior lamina of) internal oblique aponeurosis
  • Posterior wall: (posterior lamina of) internal oblique, transversus abdominis aponeurosis and transversalis fascia
Below arcuate line 🌟
Anterior wall:
  • All 3 aponeuroses (transversus abdominis, internal and external oblique)
Posterior wall:
  • Transversalis fascia
Location of arcuate line
 

Spermatic cord

→ a group of structures that pass to or from the testis, which are surrounded by a tubular covering; it can be found in scrotum and inguinal canal
It is formed by (3) fascia layers - note their respective origins: 🌟
External spermatic fascia → originate from:
  • External oblique aponeurosis
Cremasteric muscle & fascia → originate from: 🌟
  • Internal oblique aponeurosis
Internal spermatic fascia → originate from:
  • Transversalis fascia
 
The spermatic cord contains (8) structures: 🌟
(which can be divided into groups of 4)
  • Vas deferens - aka. Ductus deferens
Artery of vas deferens - arises from ~artery:💡
  • Testicular artery
  • Pampiniform plexus (aka. venous plexus) → drains into R/L testicular veins!
  • Cremasteric artery
Genital branch of genitofemoral nerve - supplies ~structure:
  • Cremaster muscle
      • Note that the genitofemoral nerve has 2 branches that supply different areas - and only the genital branch enters the spermatic cord!
    • Note that cremaster muscle is derived from internal oblique muscle 🌟
  • Sympathetic nerve fibers
  • Lymphatic vessels
or via mnemonic "Papers Don't Contribute To A Good Specialist Level" 💡
  • Pampiniform plexus
  • vas Deferens
  • Cremasteric artery
  • Testicular artery
  • Artery of vas deferens
  • Genital branch of genitofermoral nerve
  • Sympathetic nerve fibers
  • Lymphatic vessels
 
 
[more high-yield details in our notes]
 
📄 Back to Table of Contents
😎 Back to Samples
 
 

Ready to tackle the MRCS Part A with our comprehensive study notes at your fingertips?

🛒 MRCS On The Go - Plans & Pricing