GI Session 3- Abdomen And Hernias Flashcards
What are the main functions of the abdominal wall?
Forms a firm, flexible wall which keeps the abdominal viscera in the abdominal cavity
Protects abdominal viscera from injury
Maintains anatomical position of abdominal viscera against gravity
Assists in forceful expiration by pushing the abdominal viscera upwards
Involved an action that increases intra abdominal pressure
What are the layers of the abdominal wall? (Ex to in)
Skin
Superficial fascia
Muscles and associated fascia
Parietal peritoneum
How does the composition of the superficial fascia differ depending on its location?
Above umbilicus- single sheet of connective tissue
Below umbilicus- divided into 2 layers, fatty superficial layer (camper’s fascia) and membranous deep layer (scarpa’s fascia). Superficial vessels and nerves run between the 2 layers of fascia.
How many muscles are there in the abdominal wall and what groups can they be divided into?
2 vertical muscles
3 flat muscles
Name the 3 flat muscles and where they are located
External oblique, internal oblique and transversus abdominis
Located laterally in the abdominal wall stacked upon one another
What movement are the flat muscles responsible for?
Flex, laterally flex and rotate the trunk
Describe the external oblique muscle
Larges and most superficial
Fibres run inferomedially, as fibres approach the midline they for a an aponeurosis
What is the linea alba?
Fibrous structures that extends from the xiphoid process of the sternum to the pubic symphysis
Where all the aponeuroses of the flat muscles become entwined
Describe the internal oblique muscle
Lies deep to the external oblique
Smaller and thinner in structure
Fibres run superomedially
Describe the transversus abdominis muscle
Deepest of the flat muscles
Transversely running fibres
Deep to this muscle is the transversalis fascia
Name the 2 vertical muscles
Rectus abdominis
Pyramidalis
Describe the rectus abdominis muscle
Long paired muscle found either side of the midline in the abdominal wall
It is split in 2 by the linea alba
Lateral border creates the linea semilunaris
Tendinous intersections connect to linea alba and create 6 pack
What is the function of the rectus abdominis?
Compressing abdominal viscera
Stabilises pelvis during walking
Depresses the ribs
Describe the pyramidalis and its function
Small triangle shaped muscle
Superficial to the rectus abdominus
Located inferiority- base on pubis bone and apex of the triangle attached to the linea alba
Acts to tense linea alba
What is the rectus sheath?
Formed by the aponeuroses of 3 flat muscles and encloses rectus abdominis and pyramidalis muscles
What forms the anterior and posterior walls of the rectus sheath?
Anterior wall- aponeuroses of external oblique and half internal oblique
Posterior- aponeuroses of half internal oblique and transversus abdominis
Halfway between umbilicus and pubic symphysis all aponeuroses move to anterior wall so no posterior wall
What is the area of transition between posterior wall and no posterior wall called?
Arcuate line
What must be considered by a surgeon when deciding on an incision?
Direction of muscle fibres
Location of nerves
Ease of access to desired viscera
Describe the 2 vertical incision that can be made
Median- through linea alba, can be extended the whole length of the abdomen curving round umbilicus
Paramedian- lateral to linea alba
What are the advantages of a median incision?
Minimal blood loss
Major nerves avoided
Used for any procedure requiring access to the abdominal cavity
What are the advantages/disadvantages of paramedian incision?
Provides access to more lateral structures
Ligates blood and nerve supply to muscles medial to the incision, resulting in their atrophy
Describe the different transverse incisions that can be used
Transverse- inferior and lateral to umbilicus
Suprapubic- 5cm superior to pubic symphysis
Subcostal- inferior to xiphoid process, and extents inferior parallel to costal margin
McBurney- grid iron incision, 2 perpendicular lines at McBurneys point
Where is McBurneys point?
1/3 of the distance between ASIS and umbilicus
What are the different transverse incisions used for?
Transverse- colon, duodenum and pancreas
Suprapubic- pelvic organs
Subcostal- gall bladder (R), spleen (L)
McBurney- appendicectomies
What advantages/disadvantages do the different transverse incisions have?
Transverse- least damage to nerve supply, heals well
Suprapubic- can perforate bladder as fascia thins around bladder area
McBurney- excellent healing as muscle fibres not cut
Name the 9 regions the abdomen can be split into
R and L hyperchondrium Epigastric R and L flank Umbilical R and L groin Pubic
How is the abdomen split into 9?
2 horizontal and 2 vertical planes
What are the 2 horizontal planes?
Transpyloric plane- horizontal line halfway between xiphoid process and umbilicus, passing through pyloris of the stomach
Intertubecular plane- horizontal line joining iliac crests
Where do the 2 vertical planes lie?
Run vertically from the mid clavicle to mid inguinal point
Called mid clavicular lines
Name some developmental defects of the abdominal wall
Ectopic cordis- heart develops outside chest
Patent urachus
Urachal cyst
Patent vitellointestinal duct
Exampholos- viscera covered by peritoneum and amnion
Gastroschisis- vertical defect to right of umbilicus, viscera not covered by peritoneum and amnion
What is somatic referred pain?
Pain caused by a noxious stimulus to the proximal part of a somatic nerve that is perceived in the distal dermatome of the nerve
What is visceral referred pain?
In the thorax and abdomen, visceral afferent pain fibres follow sympathetic fibres back to the same spinal cord segments that gave rise to the preganglionic sympathetic fibres. CNS perceives visceral pain as coming from the somatic portion of the body supplied by the relevant spinal cord segments
What can cause visceral pain?
Ischaemia
Abnormally strong muscle contraction
Inflammation
Stretch
What are the 2 potential sites of weakness in the abdominal wall?
Inguinal canal
Femoral canal
Umbilicus
Previous incisions
Describe the inguinal canal
Oblique passage that extends in a downward and medial direction
Begins at deep inguinal ring a and continues for 4cm ending at superficial inguinal ring
What are the boundaries of the inguinal canal?
Anterior wall- aponeurosis of external oblique, and reinforced by internal oblique muscle laterally
Posterior wall- transversalis fascia
Roof- transversalis fascia, internal oblique and transversus abdominis
Floor- inguinal ligament, and thickened medially by lacunar ligament
What are the contents of the inguinal canal?
In men- spermatic cord passes through
In women- round ligament of uterus traverses through the canal
Define hernia
The protrusion of an organ or fascia through the wall of cavity that normally contain it
What is a direct/indirect hernia?
Indirect- where the peritoneal sac enters the inguinal canal through the deep inguinal ring
Direct- where the peritoneal sac enters the inguinal canal through the posterior wall of the inguinal canal. Bulges through Hesselbach’s triangle
How is an indirect inguinal hernia formed?
Congenital origin- failure of processes vaginalis to regress
Degree of herniation depends on the amount of processes vaginalis still present. As sac moves through canal it acquires same 5 coverings as contents of canal
How is a direct inguinal hernia formed?
Acquired in origin due to weakening in abdominal musculature
Peritoneal sac originates from an area medial to epigastric vessels and bulges into the inguinal canal via posterior wall
What is the anatomical difference between direct and indirect inguinal hernias?
Indirect inguinal hernia- lateral to the inferior epigastric vessels
Direct inguinal hernia- medial to inferior epigastric vessels
Describe a femoral hernia
More common in females as they have wider hips
Can easily become incarcerated or strangulated
Describe an umbilical hernia
- Congenital omphalocele
Contents herniated into umbilical cord
Has peritoneal covering
Different to gastrochisis - Acquired infantile- contents herniated through weakness in scar of umbilicus
- Acquired adult- goes through linea alba in region of umbilicus, more likely in females
Describe an epigastric hernia
Occurs through linea alba between xiphoid process and umbilicus
Usually starts with small hernia
Chronic straining forces more fat out which can eventually pull peritoneum through
What are the symptoms of an epigastric hernia?
Based around what happens if loops of bowel get trapped
-pain, vomiting, sepsis
Define incarcerated
‘Stuck’, irreducable
Define strangulated
Blood supply is disrupted- can lead to tissue necrosis
