Rectus
sheath : is formed by connective tissue which enclosing
the rectus abdominis muscle (and occationally
pyramidalis muscle )
It is formed by aponeurosis of three flat muscles of
anterior abdominal wall .
The entire anterior surface of rectus abdominis
muscle is covered by anterior part of rectus sheath but only middle 2/3 of
posterior surface of rectus abdominis muscle is covered by posterior part of
rectus abdominis muscle. The lower limit of posterior part of rectus sheath is
known as arcuate line . This line is situated in midpoint of the umbilicus and upper surface of pubis
symphysis . so posterior surface of rectus abdominis muscle are devoid of
rectus sheath at two places , above the costal margin and below the arcuate
line. Above the costal margin it is related with 5th , 6th
and 7th costal cartilage and below the arcuate line it is related
with fascia transversalis.
Internal oblique abdominis muscle of anterior
abdominal wall is an interesting muscle. Because its aponeurosis divide into
two part at the lateral surface of each rectus abdominis muscle and hold the
rectus abdominis muscles as testtube holder . So the aponeurosis of internal
oblique abdominis muscles, form both anterior and posterior part of rectus
sheath .
Arrangement
of anterior part of rectus sheath: arrangement are different in three places
,
1) above costal margin : this part is formed by one
aponeurosis: the aponeurosis of external
oblique abdominis
2) from costal margin to arcuate line : this part is
formed by two aponeurosis : the aponeurosis of external oblique abdominis and anterior
layer of aponeurosis of internal oblique abdominis
3) below the arcuate line : this part is formed by
three aponeurosis : the aponeurosis of external oblique abdominis, internal
oblique abdominis and transversus abdominis
Arrangement
of poterior part of rectus sheath: arrangement are different in three places ,
1) Above
costal margin : No rectus sheath . this part is related with 5-7 costal
cartilage
2) From costal margin to arcuate line : this part is
formed by two aponeurosis : posterior layer of aponeurosis of internal oblique abdominis and
transversus abdominis muscles
3) Below the arcuate line: no rectus sheath. This
part is related with fascia transversalis.
Tips
for memorization:
|
ant
part of rectus sheath
|
rectus
abdominis
|
Pos
part of rectus sheath
|
|
Above costal margin : 1 aponeurosis
(EOA)
|
|
no
rectus sheath
|
|
Costal margin to arcuate line : 2 aponeurosis (EOA & IOA)
|
2
aponeurosis
(IOA
& TA)
|
|
|
Below the arcuate line : 3 aponeurosis
(EOA,
IOA, TA)
|
no
rectus sheath
|
SN:
1) aponeurosis
of external oblique abdominis muscles are present in all level of anterior part
of rectus sheath
2) Aponeurosis
of internal oblique abdominis muscles are divided and hold the rectus abdominis muscles like test tube holder
and it forms both anterior and posterior part of rectus sheath
3) Below
arcuate line three aponeurosis of flat anterior abdominal wall muscles are present at the
anterior part of rectus sheath
Content of rectus sheath :
Two
Muscles : rectus abdominis
and pyramidalis
Two
arteries : superior epigastric artery and inferior epigastric artery
Two
veins : superior and inferior epigastric veins
Six
nerves: lower five intercostals nerves and subcostal nerve
Latest
view of rectus sheath formation:
Recent observation is all aponeurosis of flat anterior
abdominal muscles are divided into two layers . so three muscles have total six
aponeurosis , three aponeurosis present
in front and three aponeurosis present behind .
It is also observe aponeurosis of flat muscles are
not end in linea alba but they decussate and continued as contralateral
aponeurosis .
The
lateral part of rectus abdominis muscle produce a groove in the anterior
abdominal wall , is known as linea semilunaris.
This groove is important because medial to this groove and lateral to this groove the layers of anterior abdomnal wall
is different
Layers
of anterior abdominal wall, medial to the linea semilunaris (from before backward )
1) Skin
2) Superficial
fascia : fascia camper and fascia scarpa
3) Aponeurosis
of external oblique abdominis
4) Aponeurosis
of anterior layer of internal oblique abdominis
5) Rectus
abdominis muscle
6) Aponeurosis
of posterior layer of internal oblique abdominis
7) Aponeurosis
of transversus abdominis
8) Fascia
transversalis
9) Extraperitoneal
tissue
10)
Parietal layer of peritoneum
Layers of anterior abdominal wall, lateral to
the linea semilunaris (from before
backward )
1) Skin
2) Superficial
fascia : fascia camper and fascia scarpa
3) external oblique abdominis muscle
4) internal oblique abdominis muscle
5) transversus abdominis muscle
6) Fascia
transversalis
7) Extraperitoneal
tissue
8) Parietal
layer of peritoneum
SN:
Flat muscles have two
part fleshy part and fibrous part (aponeurosis ) . Fleshy part of anterior
abdominal wall muscles is present away from the median plan and fibrous /
aponeuroses are present at the middle part of abdomen. So the middle part of
anterior abdominal wall is made by three aponeurosis of flat abdominal wall
muscles. This is the weakest part of
abdomen and it is secured by rectus abdominis muscles which present two side of
linea alba ( the median groove of anterior abdominal wall ) and rectus
abdominis is secured by aponeurosis of three flat muscles of abdomen .
