L1. Anatomy Of The Anterior Abdominal Wall Flashcards

1
Q

What are the main components of the anterior abdomen?

A

Abdominal walls
Peritoneal lined abdominal cavity
The abdominal contents

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2
Q

What is the structuring of the abdominal wall similar to? What are the layers? (5)

A

Similar to the thoracic wall

  1. Skin and superficial fascia
  2. 3 flat layers of abdominal muscle with 4th anterior muscle
  3. Deep fascia called the transversalis fascia
  4. Extraperitoneal fascia and fat
  5. Peritoneum
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3
Q

What is the muscle that differentiates the structure of the abdomen to the structure of the thorax? Where is it and how is it orientated?

A

An anterior muscle to the midline called the RECTUS ABDOMINUS. It is orientated verticallly

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4
Q

Describe the peritoneum

A

Similar to the pleura:
It lines the walls of the cavity (parietal) and from posterior wall reflects off at different points into the cavity to surround abdominal viscera (visceral peritonem)

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5
Q

What two landmarks do the anterior abdominal muscles bridge from and towards?

A

The costal margin superiorly

The pelvis inferiorly

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6
Q

Describe the main bony attachments of the anterior abdominal muscles on the pelvis

A

The superior aspect of the pelvis:

  • Iliac crest posteriorly
  • Pubic tubercle anteriorly
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7
Q

Because there are three fat layers of muscles attaching to the cage above, describe the specific arrangement so they all ‘fit’

A
  • Front: over the ribs above (overlaps anterior aspect of the cage)
  • Miiddle: edge to edge to costal margin
  • Deep: under the ribcage to the inner aspect of the rib cage (underlaps the costal margin)
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8
Q

What is the most deepest/most internal muscle of the anterior abdominal wall?

A

The diaphragm is continuous with the anterior abdominal wall and sits in the plane

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9
Q

Describe the general trend of the muscles in the anterior abdomen

A

The are fleshy laterally and apeoneurotic medially

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10
Q

What is aponeurosis?

A

A sheet of pearly white fibrous tissue which takes the place of a tendon in sheet-like muscles having a wide area of attachment

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11
Q

Where do the anterior muscles meet anteriorly and posteriorly?

A
  • The two aponeurotic extensions (left and right) aponesurosis meets in the midline.
    = Anteriorly the aponeurosis meet at the vertical raphe (LINEA ALBA) “a white line”
  • The muscles meet and interdigitate in the midline and go around around as far as the THORACOLUMBAR FASCIA posteriorly
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12
Q

What is the most external anterior abdominal muscle? How are the fibres orientated?

A

The external oblique muscle

Front pockets orientation: forwards and downwards

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13
Q

Describe the attachement of the external oblique muscle superiorly to the cage

A

It Extends onto the front of thoracic cage costal margin (overlaps the costal margin) up to (and edge to edge) of pectoralis major and serratus anterior

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14
Q

Describe the inferior attachment of the external oblique muscle to the pelvic bone

A

External oblique attaches onto anterior half of iliac crest (as far as the ASIS) and ‘jumps’ and attaches to pubic tubercle and pubic crest.

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15
Q

What is the inguinal ligament?

A

The free floating area of the external oblique between the ASIS and pubic tubercle that is not attached to anything.
It is a thickened and has a guttering that flaps under itself.

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16
Q

Describe the apneurotic connection of the external oblique with the pubic crest

A

There is a triangular opening in the aponeurotic part of the external oblique before the final attachment to the pubic crest (deficiency in attachment to the pubic bone).

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17
Q

Describe the internal oblique muscle fibre orientation

A

“Orientated Back Pockets”: downwards and backwards (like the inner intercostals)

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18
Q

How and to what does the internal oblique muscle attach to superiorly and in the horizontal plane.

A

Plug directly into the intercostal margin superiorly.

The two sides meet the each other in midline (linea alba) and extends as far as the thoroacolumbar fascia towards the back.

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19
Q

Describe the inferior attachment of the internal oblique muscle

A

Begins its attachment to the anterior half of the iliac crest to the ASIS. After the ASIS (lowermost fibres) they take origin from the lateral 2/3 of the inguinal ligament. (its origin continues from the ligament).

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20
Q

There are 3 flat layers of abdominal muscle behaving in the same fashion. Where is the major difference between them? Why does this occur?

A

The INGUINAL REGION - comes about because there is a free inferior edge to external oblique which gives origin to the internal oblique.

21
Q

What is the innermost muscle of the anterior abdominal wall? How are the muscle fibres arranged?

A

TRANSVERSUS ABDOMINUS: Horizontally (transversally) orientated fibres

22
Q

What is the importance of the horizontal orientation of the transverse abdominus muscle?

A

STRENGTH (three different fibre directions) in contraction of the abdominal wall protects the abdominal viscera which are exposed (not protected by bone) and compressing abdominal contents and raising abdominal pressure (for coughing, urination, defecation, child birth, etc.)

23
Q

How does the transverse abdominus muscle relate to the thoracic cage superiorly? How does it behave in the horizontal plane?

A

Underlaps costal margin and becomes continuous and in the same plane as diaphragm. Also goes as far posteriorly as thoracolumbar fascia and meets at midline at the linea alba.

24
Q

Describe the inferior attachement of the abdominus muscle to the pelvis

A

It attaches onto the anterior half of the iliac crest and then the lowermost fibres continue to arise from the lateral part of the inguinal ligament (lateral third or maybe half of the inguinal ligament). These lower most fibres don’t go to the linea alba. They arch and inset (up, over, down) to inserts into the pubic crest - like the internal oblique

25
Q

The internal oblique and transverses abdominus are intimately linked. What is their relationship at the pubic crest?

A

They both insert into the pubic crest by a CONJOINED TENDON: formed by fibres of both internal oblique and transversus abdominus.

26
Q

What is the rectus abdominus muscle?

A

Another pair of vertically orientated muscles on either side of the midline

27
Q

Describe the origin and pathway of the rectus abdominus muscle and where it attaches to superiorly

A

Arises inferiorly from the pubic crest and as the fibres ASCEND they diverge (divergent muscle - gets wider as you go up) and crosses the anterior costal margin and attaches to costal cartilages (5,6,7) edge to edge with pectoralis major.

28
Q

What are and what is the function of the tendinous intersections of the rectus abdominus muscle?
Where are they?

A

There are tendinous intersections: horizontal fibrous disruptions to the vertical ascent to the fibres (3 of them) creates a muscle with many short fibres which is stronger than one with long fibres.

  1. At level of umblicus
  2. Xyphisternum
  3. halfway in between them
29
Q

How does the rectus abdominus muscle relate to the aponeurosis of the other three muscles in the midline?

A

The aponeurosis create an envelope (fascia or sheath) around rectus abdominus as they head to the midline. The sheath encloses rectus abdominus

There is an anterior sheath that covers the rectus and a posterior sheath (at least part of the way down) enclosing the rectus abdominus (Vessels also run in the posterior sheath)

30
Q

Describe the structure of the aponeurosis of the different muscles around the rectus abdominus muscle

A

External oblique aponeurosis runs in front of the rectus abdominus

The transverse abdominus aponeurosis behind it

The internal oblique splits with half going in front and half back

They make the a complete envelope surrounding the rectus abdominus muscle. They all reconvene in the midline as the linea alba

31
Q

What is the arcute line?

A

A line of of demarcation that where the complete envelope stops about an inch below the umblicus: Where all the aponeourosis form only an anterior aponeruosis and there is no posterior. It is always arched

32
Q

Through what muscles does the neurovacuslar plane run through?

A

Between intermediate and deep layers (internal oblique and transversus abdominus)

33
Q

What is the segmental innervation of the anterior abdomen?

A
  • T10 IS THE UMBILICUS and thus anything above (7,8,9)
  • And T11-12 between umbilius and groin
  • L1 IS THE GROIN
34
Q

Describe the blood supply to the anterior abdominal wall

A

The main arterial supply to anterior abdominal wall comes from a superior epigastric from above and inferior epigastric from below. These run in the RECTUS SHEATH deep to rectus abdominus in posterior part of the sheath

35
Q

What do the superior and inferior epigastric arteries branch off?

A

The internal thoracic running either side of the sternum inside the thoracic cage - it gives off the superior epigastric which continues down as a branch (supplying the walls of the cavity).

The inferior epigastric artery is a branch of the external ileac artery

36
Q

Describe the venous drainage of the anterior abdominal wall. What is important about this feature to pathology?

A

There is a dual venous drainage of abdominal structures: portal and systemic venous systems

There are sites of overlap between them and they become important when a patient has portal hypertension. The anterior abdominal wall is one site of portal-systemic anastomoses.

37
Q

Describe the two other ligaments arising off the inguinal ligament in the pelvic region

A

There is a cresentic extension of the ingunal ligament towards the towards pectoneal line of the pubic bone (the line on the pubic bone that marks the pelvic inlet). This is called the LACUNAR LIGAMENT.

There is another linear extension off the lacunar ligament called the PECTINEAL LIGAMENT

38
Q

Where do the testes develop? What does this mean?

A

The TESTES develop in the extraperitoneal fat: on the posterior abdominal wall (quite high up). They need to descend to the scrotum.

It means they need to get through all layers of skin and superficial fasia (which are continuous with the scrotum)

39
Q

Describe the layers the testes need to descend through to get to their target

A

ORIGIN: extraperitoneal fat (testes in development) -> transversalis fascia -> transversus abdominus —> internal oblique —> external oblique —> superficial fascia and skin (TARGET)

40
Q

Describe the pathway down the abdomen of the testes down to the scrotum

A
  1. Through fascia transversalis (through a deficiency created halfway between ASIS and pubic tubercle a fingers breath above inguinal ligament - this ‘hole’ created by the testes (called the DEEP INGUINAL RING)
  2. It then needs to pass the transversus abdominus and internal oblique. These muscles arch upwards over and to the midline to the pubic crest (to form the conjoined tendon) so the testes can move under this INGUINAL CANAL - (the ‘floor’ is the inguinal ligament)
  3. There is a hole in External Oblique (triangular gap before it attaches to pubic crest) for it to get into the skin and superfascia = the EXTERNAL/SUPERFICIAL INGUINAL RING
41
Q

What forms the spermatic cord and how does it arise?

A

As it descends, it drags with it the arterial supply, nerves, veins, lymphatics and duct (vas deferens) with it and they form the SPERMATIC CORD. It also includes the three layers of covering

42
Q

What happens to the contents of the spermatic cord as it descends down the anterior abdominal wall?

A

As the testes descend through each layer of anterior abdominal wall they GET A LAYER OF COVERING (three layers so they are very well protected)

43
Q

Describe the three layers of the spermatic fascia and how they are derived

A
  1. Gain the INTERNAL SPERMATIC FASCIA through the deep inguinal ring through fascia transversalis
  2. They turn medially, passing under the: CREMASTERIC FASCIA (from the cremaster muscle fibres associated with it internal oblique mainly)
  3. They go through the superficial ring (External oblique) and gain the EXTERNAL SPERMATIC FASCIA
44
Q

What happens to the contents of the abdomen when there is a contraction of the anterior abdominal muscles?

A

The intra-abdominal wall pressure rises: and thus the contents become very crowded inside.
= Thus these abdominal wall contents have the propensity to want to escape (look for sites of weakness)

45
Q

What is an abdominal hernia? Where do they occur?

A

The abnormal protrusion of abdominal contents through the abdominal wall. They occur at any site of weakness in the wall that can be congenital or post-operative

46
Q

What is one of the most attractive sites for abdominal hernias?

A

The inguinal region (canal) because it is an opening of the abdominal cavity: forming an INGUINAL HERNIA
The abdominal contents follow the path of the developed testes - it is an INDIRECT HERNIA

47
Q

What is a Bilateral Direct Inguinal Herniae

A

A protrusion forwards into the inguinal canal through an area of weakness in the abdominal wall

48
Q

Where is the area of weakness in the anterior abdominal wall?

A

The inguinal region:
Between the inferior epigastric artery (medial to it) and rectus abdominus is the weakest point of anterior called the INGUINAL TRIANGLE