GI Anatomy of Abdominal Wall Flashcards
What is the abdominal wall subdivided into?
- The anterior wall
- Right and left lateral walls
- Posterior wall
Why is the term anterolateral abdominal wall used?
Because the boundary between the anterior and lateral walls is indefinite
What is the anterolateral abdominal wall bounded by superiorly?
- The cartilages of the 7th-10th ribs
- The xiphoid process of the sternum
What is the anterolateral abdominal wall bounded by inferiorly?
- The inguinal ligament
- The superior margins of the anterolateral aspects of the pelvic girdle
What are the anterolateral aspects of the pelvic girdle?
- Iliac crests
- Pubic crests
- Pubic symphysis
What does the anterolateral abdominal wall consist of?
- Skin
- Subcutaneous tissue
- Muscles and their aponeuroses
- Deep fascia
- Extraperitoneal fat
- Parietal peritoneum
What does the subcutaneous tissue of the anterolateral abdominal wall consist of?
Superficial fasica and fat
Label this diagram
- A - Skin (cut edge)
- B - Superficial fatty layer of subcutaneous tissue (Camper fascia)
- C - Deep membranous layer of subcutaneous tissue (Scarpa fascia)
- D - Investing (deep) fascia- superficial, intermediate, and deep
- E - Parietal peritoneum
- F - Endoabdominal (transversalis) fascia
- G - Extraperiteoneal fat
- H - Transversus abdominis
- I - Internal oblique
- J - Internal oblique
What is the umbilicus?
An obvious feature of the anterolateral abdominal wall at spinal level L3
What is the epigastric fossa also known as?
Pit of the stomach
What is the epigastric fossa?
Slight depression in the epigastric region
Where is the epigastric fossa found?
Just inferior to the xiphoid process
What is the epigastric fossa particularly noticeable?
When the person is in the supine position
Why is the epigastric fossa particularly noticeable when the person is in the supine position?
Because the abdominal organs spread out
What is commonly felt on the side of the epigastric fossa?
Heartburn
What forms the linea alba?
Aponeurosis of the abdominal muscles
What does the linea alba separate?
The left and right rectus abdominis
Who is the linea alba visible in?
Lean individuals
Why is the linea alba visible in lean individuals?
Because of the vertical skin groove superficial to it
What is the name of the condition where the linea alba is lax?
Divarication of recti
What happens in divarication of recti?
When the rectus abdominis contract, the muscles spread apart
What is the pubic crest?
The upper margins of the pubic bones
What is the pubic symphysis?
The cartilaginous joints that unite the pubic bones
Where can the pubic crest be felt?
At the inferior end of the linea alba
What is the inguinal groove?
A skin crease that is parallel
Where is the inguinal groove found?
Parallel and just inferior to the inguinal ligament
Where does the inguinal groove run?
Between the ASIS and pubic tubercle
What does the inguinal groove mark?
The division between the abdominal wall and the thigh
What are semilunar lines?
Tedinous line on either side of rectus abdominis
What shape are the semilunar lines?
Slightly curved
In whom are the tendinous intersections of rectus abdominis clearly visible?
In persons with well developed rectus muscles
As well as the tendinous intersections of the rectus abdominis, what else is visible in persons with well-developed rectus muscles?
The interdigitating bellies of the serratus anterior and external oblique muscles
What is the arcuate line also known as?
Douglas’ line
What is the arcuate line?
Where the fibrous sheath stops at the inferior limit of the posterior layer of the rectus sheath
Where is the arcuate line?
1/3 of the way from the umbilicus to the pubic crest
Label this diagram
- A - Site of xiphoid process
- B - Right costal margin
- C - Umbilicus
- D- Iliac crest
- E - Anterior superior iliac spine
- F - Inguinal ligament
- G - Site of pubic tubercle
- H - Epigastric fossa
- I - Site of linea alba
- J - Semilunar valves
- K - Site of pubic symphysis
- L - Serratus anterior
- M - External oblique
- N - Left rectus abdominis
- O - Location of linea alba
- P - Umbilicus (level of L3 vertebrae)
- Q - Location of inguinal ligament and groove
How many muscles are there in the abdominal wall?
5
How are the muscles in the anterolateral abdominal wall related to each other?
They are bilaterally paired
What shape are the muscles in the anterolateral abdominal wall?
- Three flat
- Two vertical
What are the flat muscles in the anterolateral abdominal wall?
- External oblique
- Internal oblique
- Transversus Abdominis
What are the vertical muscles in the anterolateral abdominal wall?
- Rectus Abdominis
- Pyramidalis
What orientation are the fibres in the flat muscles in the anterolateral abdominal wall?
Varying orientation;
- Fibres of obliques run diagonally and perpendicular to each other
- Fibres of transversus running transversely
Label these diagrams
- A - Free posterior border of external oblique
- B - Internal oblique
- C - Anterior superior iliac spine
- D - External oblique
- E - Rectus sheath (anterior layer)
- F - Inguinal ligament
- G - External oblique (cut)
- H - Attachment of external oblique to iliac crest
- I - Internal oblique
- J - Inguinal ligament
- K - External oblique (cut)
- L - Thoracolumbar fascia
- M - Cut attachments of internal oblique
- N - Transversalis abdominis
What is the origin of the external oblique muscle?
External surfaces of the 5th to 12th ribs
What is the insertion of the external oblique muscle?
- Linea alba
- Pubic tubercle
- Anterior half of iliac crest
What is the origin of the internal oblique?
- Thoracolumbar fasica
- Anterior two thirds of iliac crest
- Connective tissue deep to lateral third of inguinal ligament
What is the insertion of the internal oblique?
- Inferior borders of the 10th to 12th ribs
- Linea alba
- Pectin pubis via conjoint tendon
What is the origin of the transversus abdominis?
- Internal surfaces of the 7th to 12th costal cartilages
- Thoracolumbar fascia
- Iliac crest
- Connective tissue deep to lateral third of inguinal ligament
What is the insertion of the transversus abdominis?
- Linea alba with aponeuroses of internal oblique
- Pubic crest
- Pectin pubis via conjoint tendon
What happens to all three of the flat muscles of the anterolateral abdominal wall?
They are continued anteriorly and medially as strong, sheet-like aponeuroses
What happens to the aponeuroses of the flat muscles of the anterolateral abdominal wall?
They form the tough, aponeurotic, tendinous rectus sheath
Where is the rectus sheath formed?
Between the mid-clavicular line and the midline
What does the rectus sheath enclose?
The rectus abdominis
Label these diagrams
- A - Fibres of left external oblique aponeurosis, which run deep on the right side and running superficially on the left side
- B - Umbilical ring
- C - Deep fibres of right external oblique aponeurosis
- D - Deep fibres of left external oblique aponeurosis
- E - Right external oblique muscles
- F - Fibres of right external oblique aponeurosis
- G - Fibres passing from superficial to deep at linea alba
- H - Fibres of left internal oblique aponeurosis
- I - Left internal oblique muscle
What happens once the aponeuroses’ of the flat muscles of the anterolateral abdominal wall have formed the rectus sheath?
They interweave with their fellows of the opposite side
What is formed when aponeuroses interweave?
The linea alba
Where does the linea alba extend?
From the xiphoid process to the pubic symphysis
What is the interweaving of aponeuroses between?
- Between right and left sides
- Between intermediate and deep layers
Label this diagram
- A - Linea alba
- B - Rectus abdominis
- C - Rectus sheath
- D - Linea alba, with fibres passing from superficial to deep, and vice versa
- E - Linea alba
- F - Rectus sheath
- G - Aponeurosis of transversus abdominis muscle
- H - Parietal peritoneum
- I - Transversalis fascia
- J - Transversus abdominis muscle
- K - Internal oblique
- L - External oblique
- M - Subcutaneous tissue
- N - Aponeurosis of external oblique
- O - Laminae of external oblique
- P - Skin
- Q - Parietal peritoneum
- R - Extraperitoneal fat
- S - Transversalis fascia
- T - Membraneous layer
- U - Fatty layer
What is contained within the rectus sheath?
The two vertical muscles of the anterolateral abdominal wall;
- Rectus abdominis
- Pyramidalis
Label this diagram
- A - 12th rib
- B - Quadratus lumborum (posterior abdominal wall)
- C - Rectus abdominis
- D - Costal cartiages
- E - Tendinous intersections
- F - Pubic crest
What do we want when designing an incision?
One that will closer and provide long-lasting strength
What is the importance of designing an incision that will provide long lasting strength?
Minimising the incidence of incisional herniae
What happens if we try to sew muscle together?
The sutures will ‘cut out’
When is a midline incision used abdominally?
Surgeons suture the linea alba together
When is a transverse incision used abdominally?
Surgeons suture the external oblique aponeuroses together
Where are incisions made for an appendicectomy?
- McBurney’s Point
- 2/3rds of the distance between the umbilicus and ASIS
How is the incision through 2/3 of the distance between the umbilicus and the ASIS made?
Throguh a ‘gridiron’ muscle-splitting incision
How is a girdiron incision conducted?
Put scissors in, and open and close them to separate out the muscle fibres, followed by the next two layers
What muscle fibres have to be seperated out when performing an appendectomy?
Those of the external and internal oblique’s, and the transversalis
Give 6 disorders that are consequences of developmental defects in the abdominal wall
- Patent Urachus
- Gastroschisis
- Omphalocoele
- Problems of the Vitelline duct resulting in:
- Meckel’s Diverticulum
- Vitelline cyst
- Vitelline fistula
What is the most common GI abnormality?
Meckel’s Diverticulum
When does a patent urachus present?
Can present at birth, or later in life in men
What can cause a patent urachus to present later in life?
A bladder outflow obstruction
What causes a bladder outflow obstruction that can cause a patent urachas to present later in life?
Benign prostatic hypertrophy
What does the persistance of a vitelline duct result in?
A number of different abnormalities
What is Meckel’s Diverticulum also known as?
Ilieal Diverticulum
What is Meckel’s Diverticulum?
A ‘cul-de-sac’ in the ileum
What rule does Meckel’s Diverticulum follow?
The rule of 2’s
Why is it said that Meckel’s Diverticulum follows the rule of 2’s?
- 2% of population affected
- 2 feet from ileocecal valve
- 2 inches long
- Usually detected in under 2’s
- 2:1 male:female
What can Meckel’s Diverticulum contain?
Ectopic gastric or pancreatic tissue
What will the ectopic tissue in Meckel’s Diverticulum do?
Secrete enzymes and acids into tissue not protected from them
What is the result of the secretion of enzymes and acid from Meckel’s Diverticulum?
Causes ulceration
Draw a diagram illustrating Meckel’s Diverticulum
What happens in a vitelline cyst?
The vitelline duct forms fibrous stands at either end
Draw a diagram illustrating a vitelline cyst
What happens in a vitelline fistula?
There is direct communication between the umbilicus and the intestinal tract
What is the result of a vitelline fistula?
Faecal matter comes out of the umbilicus
Draw a diagram illustrating a vitelline fistula
What is omphalocoele?
The persistance of physiological herniation
What happens in omphalocoele?
A part of the gut tube fails to return to the abdominal cavity following its normal herniation into the umbilical cord
What covers the defect in omphalocoele?
An epithelial layer
Why does an epithelial layer cover the defect in omphalocoele?
Since the umbilical cord is covered by a reflection of the amnion
Draw a diagram illustrating omphalocoele
What is gastroschisis?
Failure of closure of the abdominal wall during folding of the embryo, leaving the gut tube and its derivatives outside of the body cavity
What covers the gut tube and its derivatives in gastroschisis?
Nothing
Where do the gut tube and its derivatives herniate in gastroschisis?
Directly into the abdominal cavity
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
Give an example of a condition that gives somatic reffered pain?
Shingles
Why does shingles cause somatic referred pain?
Shingles affects nerves, and pain is felt distally along the nerves from the problem
How does the CNS perceive visceral pain?
As coming from the somatic portion of the body supplied by the relevant spinal cord segments
Why does the CNS perceive viseceral pain as coming from a somatic portion of the body?
Because in the thorax, visceral afferent pain fibres follow sympathetic fibres back to the same spinal cord segments that give rise to the preganglionic sympathetic fibres
What causes visceral pain?
- Ischaemia
- Abnormally strong muscle contractions
- Inflammation
- Stretching
What does not cause visceral pain?
- Touch
- Burning
- Cutting
- Crushing
Draw a diagram illustrating how visceral reffered pain may arise?
Where is pain originating from the foregut referred to?
Epigastric region
Where is pain originating from the midgut referred to?
Periumbilical region