Week 1 - Abdomen

Question 1

What anatomical landmarks are used to divide the abdomen into quadrants and regions?

Answer 1

Quadrants

• transumbilical plane (level of L3/4 disc)
• median plane

Nine regions

Horizontal

• subcostal plane -> inferior borders of 10th costal cartilages
• transtubercular plane -> iliac tubercles (level of L5)

Vertical

• 2 x midclavicular plane -> midpoint of clavicles to mid-inguinal points

Question 2

Discuss the possible locations at which a pre-synaptic parasympathetic neuron can synapse with a post-synaptic parasympathetic neuron.

Answer 2

Synpase within terminal ganglia (located near or within target organ)

Question 3

Describe the foetal formation of the mouth and anus. In what week is this process completed?

Answer 3

• Endoderm fuses with ectoderm at the head and tail of the embryo
• Head - formation of oral membrane
• Tail - cloacal membrane
• These membranes break through the surface
• By week 8, the GI tract is a continous tube extending from the mouth to the anus
• It is open to the external environment at each end

Question 4

What is the portal circulation? How does it relate to the organs of the abdomen and the IVC?

Answer 4

• Special part of circulation that supplies the digestive system
• Nutrients broken down by stomach enter portal circulation
  
  • then, delivered to liver for absorption and packaging
  • blood travels via hepatic veins
  • then, blood enters inferior vena cava
• Portal vein = spenic vein and superior mesenteric vein

Question 5

List the organs found in each of the four quadrants

Answer 5

Question 6

What are the key differences between the abdominopelvic splanchnic nerves and the pelvic splanchnic nerves?

Answer 6

• Abdominopelvic
  
  • SNS
  • Supplies abdominopelvic viscera
  • T5-L3
  • Fight or flight function
• Pelvic Splanchnic
  
  • PNS
  • Supplies viscera not supplied by Vagus Nerve (CNX)
  • S2-S4
  • Rest and digest function

Question 7

Outline the attachments, nerve supply and actions of the External Oblique mm

Answer 7

Origin - external surfaces of ribs 5-12

Insertion - Linea alba, pubic tubercle, anterior 1/2 of iliac crest

Nerve supply - thoracoabdominal nerve and subcostal nerves

Action - flexion and trunk rotation; compression of viscera

Question 8

Define the greater omentum

Answer 8

4-layered fold of peritoneum that hangs down like an apron

Question 9

Define mesentery

Answer 9

Double layer of peritoneum, continuous with parietal and visceral peritoneum. It anchors organ to the posterior abdominal wall

Question 10

Describe the difference between an intraperitoneal and an extraperitoneal (retroperitoneal) organ

Answer 10

Intraperitoneal organs - almost completely covered with visceral peritoneum e.g. stomach

Extraperitoneal organs - only partially covered with peritoneum, usually one surface e.g. kidneys

Question 11

Outline the attachments, nerve supply and actions of the Rectus Abdominis mm

Answer 11

Origin - pubic symphysis and crest

Insertion - xiphoid process and costal cartilages 5-7

Nerve Supply - thoracoabdominal nerves

Action - flexes trunk; compresses and supports viscera

Question 12

In relation to GI tract development, how does the purpose of lateral folding differ to the purpose of head and tail folding?

Answer 12

• Head to tail folds appear after lateral folding
  
  • these folds establish the foregut, midgut and hindgut
• Lateral folding establishes the formation of the GIT

Question 13

List the embryological events that occur at: 17 days, 20 days, 22 days and 4 weeks

Answer 13

• Day 17 - Gastrulation, where two layered embryo becomes a three layered embryo (monte carlo biscuit!)
• Day 20 - Formation of neural tube (ectoderm begins folding, which later becomes spinal cord; Differentiation of mesoderm into somite (e.g. dermatome, myotome, sclerotome) intermediate and lateral mesoderm (splanchnic, somatic mesoderm)
• Day 22 - Undercutting begins, where there is lateral folding to form primitive gut
• 4 weeks - Undercutting is complete; formation of mouth and anus begins (this is later completed by week 8, when the endoderm and ectoderm fuse)

Question 14

List the nerves that make up the abdominopelvic splanchnic nerves

Answer 14

• Greater splanchnic (T5-T9/10)
• Lesser splanchnic (T9-T10/11)
• Least splanchnic (T12)
• Lumbar splanchnic (L1-L3)

These supply the abdominal viscera

Question 15

Describe the function of visceral afferent fibres (provide some examples of the type of information conveyed by these fibres)

Answer 15

Provide information about the body’s internal environment (e.g. sensitive to sudden distension, spasms, chemical irritants, mechanical stimulation)

Question 16

What type of neurons form the cardiopulmonary splanchnic nerves? How does this differ to the abdominopelvic splanchnic nerves?

Answer 16

• Cardiopulmonary splanchnic nerves
  
  • formed by post-synaptic neurons located within cardiac pulmonary and oesophageal plexuses
• Abdominopelvic splanchnic nerves
  
  • formed by pre-synaptic neurons

Question 17

Discuss the possible locations at which a pre-synaptic sympathetic neuron can synapse with a post-synaptic sympathetic neuron.

Answer 17

• paravertebral ganglia
  
  • sympathetic trunks on each side of vertebral column
• prevertabral (preaortic) ganglia
  
  • surround origins of main branches of the abdominal aorta (e.g. CT, SMA, IMA)

Question 18

Name the four quadrants of the abdomen

Answer 18

Question 19

Which embryological germ layer gives rise to the peritoneum?

Answer 19

Somatic and visceral mesoderm

Question 20

Describe the tributaries of the inferior vena cava (IVC).

Answer 20

Tributaries correspond to the branches of abdominal aorta.

• Left renal vein
• left suprarenal vein (flows into left renal vein first)
• left gonadal vein (flows into left renal vein first)
• Left common iliac vein

Question 21

Outline the attachments, nerve supply and actions of the Transverse Abdominal mm

Answer 21

Origin - inferior surface of costal cartilages 7-12, thoracolumbar fascia, iliac crest, lateral 1/3 of inguinal ligament

Insertion - linea alba with aponeurosis of internal oblique, pubic crest, pectineal line (via conjoint tendon)

Nerve Supply - thoracoabdominal nerve and 1st lumbar nerve

Action - compresses and supports abdominal viscera

Question 22

Define peritoneal ligaments

Answer 22

Double-layered aspects of peritoneum that connects an organ to another organ, or to the abdominal wall

Question 23

How do visceral afferent fibres travel back to the central nervous system?

Answer 23

Accompay either sympathetic or parasympathetic fibres, where their impulses are travelling in the opposite direction

Question 24

List the regions of the primitive gut. How does these gut regions relate to the blood supply of the abdomen?

Answer 24

• Foregut (celiac trunk)
  
  • pharynx, oesophagus, stomach, D1, liver and biliary system, pancreas, lower respiratory tract
• Midgut (SMA)
  
  • D2-D4, jejunum, ileum, caecum, appendix, ascending colon, right 1/2 of transverse colon
• Hindgut (IMA)
  
  • Left 1/2 of transverse colon, descending colon, sigmoid colon, rectum and anal canal

Question 25

Name the nine regions of the abdomen

Answer 25

Question 26

What regions of the body does the IVC drain?

Answer 26

* Drains the lower limbs, most of the posterior abdominal wall and abdominopelvic viscera

Question 27

Define the lesser omentum

Answer 27

Two-layered fold of peritoneum that connects lesser curvature of stomach and proximal part of duodenum to liver

Question 28

Name the unpaired and paired branches of the abdominal aorta

Answer 28

* Unpaired visceral branches * Celiac trunk (level of T12) * Superior mesenteric artery (L1) * Inferior mesenteric artery (L3) * Paired visceral branches * Suprarenal artery (L1) * Renal artery (L1/2) * Gonadal artery (ovarian or testicular) (L2)

Question 29

Outline the attachments, nerve supply and actions of the Internal Oblique mm

Answer 29

Origin - thoracolumbar fascia, anterior 2/3 of iliac crest, lateral 1/2 of inguinal ligament Insertion - inferior borders of ribs 10-12, linea alba, pectineal line via conjoint tendon Nerve Supply - thoracoabdominal nerve and subcostal nerves Action - flexion and rotation of trunk; compression of viscera

Question 30

Name the boundaries (walls, roof, floor), openings and contents of the inguinal canal

Answer 30

Walls - anterior: aponeurosis of external oblique mm - posterior: transversalis fascia, conjoint tendon of IO mm and TA mm - floor: inguinal ligament - roof: fibres of IO mm and TA mm Contents - male = spermatic cord - female = round ligament of uterus, nerves, vessels and lymphatics

Question 31

In relation to the gastrointestinal tract, compare the nervous distribution of CNX (Vagus) to that of the pelvic splanchnic nerves

Answer 31

* Vagus nerve (oesophagus to left colic flexure) * Pelvic splanchnic nerve (left colic flexure to superior 1/3 of anal canal)

Question 32

List the layers of the abdominal wall (from superficial to deep) and summarise the function of each layer.

Answer 32

- skin (protection, sensation, temperature regulation, immunity) - subcutaneous tissue (provides warmth) - external oblique and aponeurosis (flexion of trunk and compression of viscera) - internal oblique and aponeurosis (flexion of trunk and compression of viscera) - transverse abdominis and transversalis fascia (compression of viscera) - extraperitoneal fat (insulation, support of viscera) - parietal peritoneum (anchor organs to each other) - visceral peritoneum (protective layer)

Question 33

What is normally located in the peritoneal cavity? Name two disease process that might affect the contents of the peritoneal cavity.

Answer 33

No organs are located within the peritoneal cavity. Some fluid aids in reduced friction between the two layers. Peritonitis = associated with a fibrous exudate that causes peritoneal layers to adhere (when excessive, this can cause pain and dysfunction) Ascites = accumulation of fluid within the peritoneal cavity

Question 34

Describe the cutaneous nerve supply of the anterolateral abdominal wall. (e.g. name the nerve and root)

Answer 34

Question 35

How do the accessory glands of the GI tract (liver, gall bladder, and pancreas) develop from the primitive gut?

Answer 35

* Soon after the formation of the primitive gut, glandular organs of GI tract bud out from the **mucosa** at various points * These glands retain their connections with the GI tract and develop into ducts

Question 36

Explain how the IVC returns to the thoracic cavity. What structure does it communicate with in the mediastinum?

Answer 36

* Vena caval hiatus drains thoracic cavity * Right antrium drains mediastinum

Question 37

Name the two layers of the peritoneum (also indicate the blood and nerve supply of each layer).

Answer 37

Parietal peritoneum Nerve supply and arterial supply is same as the region that it lies on Visceral peritoneum Nerve supply and arterial supply is the same as the organ it covers

Question 38

Describe the aetiology, clinical features, complications and management of an abdominal aortic aneurysm

Answer 38

Aetiology Any factor that disrupts collagen and elastin fibres within an arterial wall predisposes it to dilation e.g. atherosclerosis (plaque formation erodes wall and contributes to inflammation that further weakens the vessel) Clinical Features Asymptomatic until they leak or rupture \>5 cm diameter (pulsatile mass in abdomen) Pressure on surrounding organs = dysphagia, dyspnoea Rupture = acute abdominal pain Classic presentation = Male, hypertensive, smoker, age \>50 years old Management * _Surgery for large or ruptured AAA_: insertion of prosthetic graft * _Medical management for early AAA_: anti-hypertensive drugs, smoking cessation