Week 1 - Abdomen Flashcards
What anatomical landmarks are used to divide the abdomen into quadrants and regions?
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
Discuss the possible locations at which a pre-synaptic parasympathetic neuron can synapse with a post-synaptic parasympathetic neuron.
Synpase within terminal ganglia (located near or within target organ)
Describe the foetal formation of the mouth and anus. In what week is this process completed?
- 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
What is the portal circulation? How does it relate to the organs of the abdomen and the IVC?
- 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
List the organs found in each of the four quadrants
What are the key differences between the abdominopelvic splanchnic nerves and the pelvic splanchnic nerves?
- 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
Outline the attachments, nerve supply and actions of the External Oblique mm
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
Define the greater omentum
4-layered fold of peritoneum that hangs down like an apron
Define mesentery
Double layer of peritoneum, continuous with parietal and visceral peritoneum. It anchors organ to the posterior abdominal wall
Describe the difference between an intraperitoneal and an extraperitoneal (retroperitoneal) organ
Intraperitoneal organs - almost completely covered with visceral peritoneum e.g. stomach
Extraperitoneal organs - only partially covered with peritoneum, usually one surface e.g. kidneys
Outline the attachments, nerve supply and actions of the Rectus Abdominis mm
Origin - pubic symphysis and crest
Insertion - xiphoid process and costal cartilages 5-7
Nerve Supply - thoracoabdominal nerves
Action - flexes trunk; compresses and supports viscera
In relation to GI tract development, how does the purpose of lateral folding differ to the purpose of head and tail folding?
- Head to tail folds appear after lateral folding
- these folds establish the foregut, midgut and hindgut
- Lateral folding establishes the formation of the GIT
List the embryological events that occur at: 17 days, 20 days, 22 days and 4 weeks
- 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)
List the nerves that make up the abdominopelvic splanchnic nerves
- Greater splanchnic (T5-T9/10)
- Lesser splanchnic (T9-T10/11)
- Least splanchnic (T12)
- Lumbar splanchnic (L1-L3)
These supply the abdominal viscera
Describe the function of visceral afferent fibres (provide some examples of the type of information conveyed by these fibres)
Provide information about the body’s internal environment (e.g. sensitive to sudden distension, spasms, chemical irritants, mechanical stimulation)
What type of neurons form the cardiopulmonary splanchnic nerves? How does this differ to the abdominopelvic splanchnic nerves?
- Cardiopulmonary splanchnic nerves
- formed by post-synaptic neurons located within cardiac pulmonary and oesophageal plexuses
- Abdominopelvic splanchnic nerves
- formed by pre-synaptic neurons
Discuss the possible locations at which a pre-synaptic sympathetic neuron can synapse with a post-synaptic sympathetic neuron.
- 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)
Name the four quadrants of the abdomen
Which embryological germ layer gives rise to the peritoneum?
Somatic and visceral mesoderm
Describe the tributaries of the inferior vena cava (IVC).
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
Outline the attachments, nerve supply and actions of the Transverse Abdominal mm
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
Define peritoneal ligaments
Double-layered aspects of peritoneum that connects an organ to another organ, or to the abdominal wall
How do visceral afferent fibres travel back to the central nervous system?
Accompay either sympathetic or parasympathetic fibres, where their impulses are travelling in the opposite direction
List the regions of the primitive gut. How does these gut regions relate to the blood supply of the abdomen?
- 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
Name the nine regions of the abdomen
What regions of the body does the IVC drain?
- Drains the lower limbs, most of the posterior abdominal wall and abdominopelvic viscera
Define the lesser omentum
Two-layered fold of peritoneum that connects lesser curvature of stomach and proximal part of duodenum to liver
Name the unpaired and paired branches of the abdominal aorta
- 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)
Outline the attachments, nerve supply and actions of the Internal Oblique mm
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
Name the boundaries (walls, roof, floor), openings and contents of the inguinal canal
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
In relation to the gastrointestinal tract, compare the nervous distribution of CNX (Vagus) to that of the pelvic splanchnic nerves
- Vagus nerve (oesophagus to left colic flexure)
- Pelvic splanchnic nerve (left colic flexure to superior 1/3 of anal canal)
List the layers of the abdominal wall (from superficial to deep) and summarise the function of each layer.
- 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)
What is normally located in the peritoneal cavity? Name two disease process that might affect the contents of the peritoneal cavity.
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
Describe the cutaneous nerve supply of the anterolateral abdominal wall. (e.g. name the nerve and root)
How do the accessory glands of the GI tract (liver, gall bladder, and pancreas) develop from the primitive gut?
- 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
Explain how the IVC returns to the thoracic cavity. What structure does it communicate with in the mediastinum?
- Vena caval hiatus drains thoracic cavity
- Right antrium drains mediastinum
Name the two layers of the peritoneum (also indicate the blood and nerve supply of each layer).
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
Describe the aetiology, clinical features, complications and management of an abdominal aortic aneurysm
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
