6.1 Abdominal wall Flashcards
What are the components of the Abdominal wall and where does it extend from (boarders)
Partly bone, mainly muscle (multiple layers of muscles with various fibre directionality)
Superior: Thoracic cage (cartilages of ribs 7-10 + xiphoid process)
Inferior: Pelvis (inguinal ligament + superior margins of pelvic girdle)
From outside in what are the layers of the abdominal wall? (7)
1) skin
2) superficial fascia: 2 components
- Fatty ( Camper’s fascia)
- Membranous (Scarpa’s fascia)
3) Muscles
- external oblique
- internal oblique
- transversus abdominis
4) Transversalis fascia
5) Extraperitoneal fascia
6) Parietal peritoneum
7) Visceral peritoneum
What are the 5 muscles in the antero-latera; abdominal wall, how are they classified?
Classified as flat or vertical
3 Flat: External oblique, Internal oblique, Transversis Abdominis
2 Vertical: Rectus abdominis on either side
What is the innervation to the parietal and visceral peritoneum?
What is the reflection of the parietal peritoneum on the visceral peritoneum and what is contained here?
Parietal peritoneum:
- somatic innervation- perceive pain as being where it is
- lines the abdominal cavity
Visceral peritoneum:
- visceral innervation- referred pain
- surrounds abdominal viscera
When parietal peritoneum reflects off the abdominal wall and becomes visceral peritoneum surrounding organs, the reflection of the wall is known as mesentery (contains blood vessels, lymphatics, nerves)
List 4 functions of the 3 main abdominal muscles
1) protection and stability of abdominal viscera
2) urination and defecation
3) assist in breathing
4) labour and delivery during childbirth
5) coughing
Describe the orientation of fibres in the External Oblique muscle and where its aponeurosis converges
Describe what 2 things the inferior fibres of the external oblique form
Fibres pass in an inferior and medial direction
External oblique aponeurosis is a continuation of the muscle. It intertwines at the midline at the “linea alba” and continues untill the pelvis
Inferior fibres of the external oblique form:
- 1) superficial inguinal ring
- 2) Inguinal ligament
Where does the inguinal ligament stretch from and too?
Stretches from the anterior superior illiac spine (ASIS) to the pubic tuburcle
What is the superficial ingual ring?
Opening in the inferior fibres of the aponeurosis of the external oblique muscle
Describe the orientation of fibres in the Internal Oblique muscle and where its aponeurosis converges
Describe what is formed from the inferior fibres of the external oblique form and where this found
Fibres are multidirectional and the aponeurosis blends into the linea alba
- Superior fibres: posterior to superior direction
- Inferior fibres: fibres: superior to medial direction
The inferior fibres the of the Internal oblique AND the transversus abdominis form the conjoint tendon
This tendon forms the posterior wall of the inguinal canal and helps to strengthen the abdominal wall. It is located medial and posterior to the superficial inguinal ring
Describe the orientation of fibres in the Transversis abdominis muscle and where its aponeurosis converges
Describe what 2 things the inferior fibres of the transversis abdominis form
Fibres are transverse
Its inferior aponeurosis also contributes to formation of the conjoint tendon
Its Inferior boarder forms the deep inguinal ring
What is the deep inguinal ring?
What “triangle” does this structure contribute to?
Formed from the inferior boarder of the Transversis abdominis
- This is the entrance into the inguinal canal
It is located lateral to the inferior epigastric artery and vein which creates hasselbalch triangle which is is prone to herniation
Give 2 potential sites of weakness that are prone to herniation in the inferior part of the abominal wall
What is located in the area between these?
1) Superficial (external) inguinal ring
2) Deep (internal) inguinal ring
The area between them forms the inguinal canal through which structures leave and enter the abdominopelvic cavity
What are the boarders of Hesselbach’s triangle
Medial: lateral border of the rectus abdominis muscle
Lateral: inferior epigastric vessels
Inferior: inguinal ligament.
What is the transversalis facia and where is it located?
What specific line does this fascia create?
The transversalis facia is a continuous layer of deep fascia that lines the abdominal cavity and continues into the pelvic cavity.
Lines the deep surface of the transversus abdominis muscle and its aponeurosis
When the transversalis fascia is the ONLY covering remaining POSTERIOR to the rectus abdominus muscle this is known as the arcuate line (see image)
Where is the arcuate line located?
What is the significance of the arcuate line? (2)
The arcuate line is located at the level of the umbilicus
Arcuate line:
1) marks the point where the posterior wall of the rectus sheath ends
2) It is also where the inferior epigastric vessels perforate/ pierce the rectus abdominis
Where do the aponeuroses of all the lateral abdominal wall muscles merge and what do they form?
The aponeuroses of all the lateral muscles become entwined in the midline, forming the linea alba
What is the linea alba and were does it extend from and to?
a fibrous structure that extends from the xiphoid process of the sternum to the pubic symphysis
What covers the Rectus Abdominis
All lateral wall muscles form an aponeurosis which covers the vertical rectus abdominis muscle, this is known as the Rectus sheath/fascia
Describe the anterior and posterior part of the Rectus sheath
What marks the point where the posterior wall ends
Anterior wall: formed by the aponeuroses of the external oblique, and of half of the internal oblique.
Posterior wall: is formed by the aponeuroses of half the internal oblique and of the transversus abdominis
- its ending is marked the arcuate line (note: the anterior wall in still present!)
Dotted line in image represents the arcuate line, compare what is seen above to below this line
The arcuate It marks the point where the internal oblique and transversus abdominis aponeuroses of the rectus sheath start to pass anteriorly to the rectus abdominis muscle, leaving only the transversalis fascia posteriorly
ABOVE AL: all lateral wall muscles form rectus sheath anterior and posterior
BELOW AL: all lateral wall muscles pass anterior but ONLY transversalis fascia passes posteriorly
What is a Rectus sheath Haematoma?
Rectus Sheath Haematoma is caused by a bleed within the rectus sheath or within the muscle itself (this is a very tight space due to the facial covering)
This causes the blood to accumulate within the muscle causing large amounts of pressure to be built up, this can be very painful
The CT scans show blood being poured into the rectus abdominus
What forms the inguinal ligament?
List 2 structures in both male and female that pass through the inguinal canal
The inferior part of the aponeurosis of the external oblique muscle forms the inguinal ligament.
This then forms the inguinal canal which is an oblique passageway for structures to pass
Inguinal canal in males: illioinguinal nerve, spermatic cord
Inguinal canal in females: illioinguinal nerve, round ligament of the uterus
List where the following hernias occur:
Inguinal hernias
Umbilical hernias
Femoral hernias
Epigastric hernias
Incisional hernias
Inguinal hernias: Indirect and Direct
Umbilical hernias: through the umbilical ring, a gap within the foetus linea alba
Femoral hernias: through the femoral canal, appears in the upper thigh
Epigastric hernias: In epigastric region through the linea alba, (midline between xiphoid process and umbilicus)
Incisional hernias: protrusion of abdominal viscera through surgical incision if doesn’t heal correctly
What is a diaphragmatic hernia, which specific type of these has 2 subtypes?
Defects in the diaphragm may allow intestines to herniate into chest. Hiatus hernia are a specific type of diaphragmatic hernias and can be 2 types:
1) Sliding hiatus hernia: the gastro-oesophageal junction may slide through the diaphragm into the chest
2) Rolling hiatus hernia: part of the fundas of the stomach may pass into the chest alongside the oesophagus
What is an Inguinal hernia and what are the 2 types?
Which is a medical emergency and why?
1) Direct: bowel enters inguinal canal “directly” through a weakness in Hesselbach’s triangle. Seen as a bulge in the inguinal region
2) Indirect (common): bowel enters inguinal canal via deep inguinal ring. Appears in scrotum or labia majora ➞ arise from incomplete closure of the processus vaginalis (during decent of the testis)
* Indirect hernia is a medial emergency as it can cause severe damage to structures it passes through
The skin, muscle and parietal peritoneum of the anterior and lateral abdominal wall are all supplied by what nerve(s)? Include nerve roots
Give 3 named nerves that are branches of this one, state their supply
How can these nerves be damaged and what may this result in?
The Intercostal nerves (T7 - T11) which give off lateral cutaneous branchs along its pathway
Main named branches:
- subcostal nerve: below the rib cage (exits at the costal margin)
- Iliohypogastric: mons pubis + some of the external superior genitalia
- Ilioinguinal nerve: mons pubis and external genitalia
All nerves can be damaged by trauma/surgery which can cause weaking of the abdominal wall, increasing risk of a hernia
Give the 4 main arteries that supply the abdomen + where each arises from
What does each supply?
1+2) Intercostal arteries and lumbar arteries: both branch of the abdominal aorta and supply lateral wall muscles
3) Superior epigastric: branch off Internal thoracic artery and supplies superior parts of the rectus abdominis
4) Inferior epigastrci: branch of the external Iliac and supplies inferior parts of the rectus abdominis (lateral boarder or H triangle)
Superior + Inferior anastamose
What is the watershed line?
At T10 at the level of the umbilicus is the watershed line, this helps indicate SUPERFICIAL lymphatic drainage of the abdomen
- Above this line all lymphatic drainage goes to the auxiliary nodes
- Below this line it goes to the superficial inguinal lymph nodes.
What implication does the watershed line have for Infection spread?
There are a group of nodes concentrated around the abdominal aorta. Alot of the abdominal viscera and abdominal wall its-self drain into these nodes and follows the deep arteries back to the:
1) Parasternal nodes
2) Pre-Aortic Lymph nodes: Celia, SM node and IM node
3) External Iliac nodes along external iliac artery
Presence of these node involvement may help indicate location of infection
When choosing a location for an abdominal incision what MUST we consider (5) and why?
Can make anywhere, but incision must be able to be CLOSED and provide long-lasting STRENGTH to minimise incidence of incisional hernia
Must consider the following:
- pre-op diagnosis
- speed at which operation must be performed
- status of patient
- previous abdominal operations
- potential placements of stomas
What are Langer Lines? (Hint: incisions)
These are lines drawn on a map of the human body that correspond to the natural orientation of collagen fibers in the dermis
Ideally the incision should be made in the direction of the lines of cleavage in skin so a hairline scar results
Give 5 benifits to midline or paramedian Incisions and state why
1) almost bloodless
2) No muscle fibres divided
3) Nerves at lower risk of injury
4) Good access to upper abdomen
5) Very quick to make
Most of these are because this location corresponds/is close to the linea alba hence risks are low
State the type of incision each is in the image
State when A and E are commonly used
A: Kocher Incision
- of value in obese patients
- exposes gall bladder and biliary tract
- cholecystectomy
E: Pfannenstiel Incision
- often used for C-section
What is a Cholecystectomy and which incision would be used?
Gall Bladder removal
Kocher’s incision (now normally performed laparoscopically)
When making an incision, along with Langer lines what other lines must we consider?
What is a Gridiron approach? Give an example of when it is used
Must consider the direction of the underlying muscles
A Gridiron approach: is a muscle-splitting decision
- in this we don’t divide the muscles as such, but spread them apart to access abdomen
eg. choice for most appendectomies (unless done laparoscopically)
