Clinical aspect of abdomen
Surface markings and anatomy
Regions of abdomen 1 hypochrondriac 2 lumbar (flank) 3 paraumbilical 4 Iliac (iliac fossa) 5 suprapubic (hypogastric) 6 epigastric 8 transpyloric plane (L1) 9 subcostal plane 10 transtubercular plane (L5)
1 External oblique muscle of abdomen
Surface markings of abdominal organs
Anterior abdominal wall
This is the gateway to the abdominal cavity anteriorly. It exposes the true intraperitoneal structures such as the small intestine, stomach, distal duodenum, transverse colon and sigmoid colon
It is provided with the following layers
2. Superficial fascia
3. THERE IS NO DEEP FASCIA
4. Layer of muscles which are arranged in three strata
a. External oblique muscle of abdomen
b. Internal oblique muscle of abdomen
c. Transversus abdominis
The three layers correspond to the three layers of muscles in the intercostal spaces which are the external intercostal, internal intercostals and innermost intercostals muscles
5. Transversalis fascia
6. Parietal peritoneum
The skin of the anterior abdominal wall is lax. It is distensible also to accommodate the ever increasing abdominal cavity. It has Langer’s lines running transversely and incision made on those lines (e.g. Pfannenstiel) heals with minimum of scar tissue formation.
Superficial fascia of the anterior abdominal wall is divided into two and this is best seen below the umbilicus. It has no deep fascia.
The layers of muscles are separated by a rectus sheath which contains the rectus abdominis. The sheath is made up of the aponeurosis of the abdominal muscles. Hence we have the aponeuroses of external oblique muscle of abdomen, internal oblique muscle of abdomen and transverses abdominis.
External oblique muscle of abdomen
This muscle has an extensive origin from the external surfaces of the lower 8 ribs as digitations. It then runs downwards and forwards like the external intercostals muscles to reach the insertion at the linea alba. The linea alba is the white line which separates the two sides of the abdominal musculature and provides the insertion of all the aponeurosis of the abdominal muscles.
The external oblique has three free borders. |
Superior free border is formed at the anterior aspects of the 5th 6th and 7th costal cartilages.
Lumbar free border which forms part of the boundaries of the lumbar triangle.
Inferior free border is formed by the inguinal ligament which is just the inward rolling of the external oblique aponeurosis. This aponeurosis is formed at the lateral border of the rectus sheath at a point called the linea semilunaris.
The following are also points of insertion of the external oblique muscle and aponeurosis
1. Anterior superior iliac spine
2. Pubic tubercle
The above two will form the attachments of the inguinal ligament
IT is also attached to the anterior 2/3 of the outer lip of the iliac crest.
Internal oblique muscle of abdomen
This muscle takes its origin from the following parts
1. Anterior 2/3 of the intermediate lip of iliac crest
2. Lateral 2/3 of the inguinal ligament
3. Conjoint lamellae of thoracolumbar fascia.
It then runs upwards and forwards as the internal intercostals muscle. It then gains its attachment (insertion) to the linea alba by its aponeurosis and also to the costal margin.
Its lower fibers also gain insertion together with the transversus abdominis, to the conjoint tendon
This is the innermost layer. It runs from the following parts
1. From costal margin
2. From the innermost lip of the iliac crest at its anterior ˝
3. From the lateral 1/2 of inguinal ligament
4. Fascia covering the iliacus muscle
5. Conjoint lamellae of the thoracolumbar fascia
From these extensive origin, the fibers run into the linea alba after helping to form the posterior wall of the rectus sheath.
Some fibers gain attachment to the conjoint tendon with the internal oblique.
The rectus abdominis takes its origin from the front of the body of the body of pubis. It then runs a straight course to reach the anterior surfaces of the 5th, 6th and 7th costal cartilages where it is attached.
It has tendinous intersections which are prominent in the muscular individual
This muscle takes origin form the superior aspect of symphysis pubis and is inserted into the linea alba. It is small pyramidal shaped muscles and is not present in all individuals.
Nerve supply to muscles
T7-T12 spinal nerves and L1 nerve
But the pyramidalis has a special supply from T12 nerve- subcostal nerve.
Blood supply from lumbar arteries and anterior intercostal arteries
Venous drainage is also from the lumbar veins and special veins which form caput medusae pattern around the umbilicus. A prominent vein is the thoraco-epigastric vein. Anterior abdominal wall veins distend in portal hypertension forming the characteristic caput medusae.
This is the collection of the aponeurosis of the anterior abdominal wall muscle
1. Above the costal margin- we have the posterior wall formed by the 5-7th costal cartilages, anterior surfaces. It has only external oblique aponeurosis as its anterior wall
2. Below the costal margin, we have the regular sheath with the external oblique aponeurosis and internal oblique anterior lamella. The posterior wall is formed by the transversus abdominis and the posterior lamella of the internal oblique.
3. Below the arcuate line- there is no posterior wall of rectus sheath.
This canal is small one running for about 4cm from the superficial (external) inguinal ring to the deep inguinal ring
It has the following boundaries.
Floor- this is made up of the inguinal ligament. This ligament is the inward rolling externally of the aponeurosis of the external oblique muscle.
Anterior wall. This is made up of the skin, superficial fasciae of Camper's and Scarpa's. Then the external oblique aponeurosis and finally the internal oblique at its lateral 1/3.
Roof is formed by the conjoint muscle of the internal oblque and transversus abdominis muscles. They run form their attachments to the inguinal ligament (lat 1/3 for transversus abdominis, lat ˝ for internal oblique muscle).
Posterior wall is formed medially by the conjoint tendon of the internal oblique and transversus abdominis as they run from the roof to the posterior wall. They form an arch which interconnects the anterior to the roof and to the posterior walls. Laterally the posterior wall is formed by the transversalis fascia.
Medial wall is formed by lacunar ligament
Content. For the ease of description we say the content is mainly spermatic and ilioguinal nerve in the male and round ligament of uterus and ilioinguinal nerve in the female.
If we however follow the rule of three we come up with the following
Content is the spermatic cord. It has 3 coverings, 3 arteries, 3 nerves and 3 others
1. External spermatic fascia . This is derived from the external or superficial inguinal ring.
2. Internal spermatic fascia. This is derived from transversalis fascia. It is the most internal of the coverings.
3. Cremasteric muscle and fascia, which are derived from the internal oblique muscle in the inguinal canal. It is the intermediate covering.
1. Testicular artery
2. Cremasteric artery
3. Artery of vas deferens
1. Genital branch of genitofemoral nerve
2. Ilioinguinal nerve
3. Autonomic nerves (Sympathetic fibers)
1.Pampiniform plexus of veins which become the testicular vein or ovarian vein at the external inguinal ring
3. Fat and ductus (vas) deferens
A hernia is an abnormal protrusion through a normal or abnormal space or opening. In the case of the inguinal hernia, it is an abnormal protrusion through the normal inguinal canal opening. It may be congenital and if so , it may extend through the embryological processus vaginalis into the scrotal sac forming the so called congenital inguino-scrotal hernia.
The inguinal canal is formed as an oblique opening through the muscles of the anterior abdominal wall. It extends from the superficial inguinal ring (external oblique aponeurosis) to the deep inguinal ring (transversalis fascia). It is about 4cm long. The hernia is usually a viscus, such as small or large intestine, urinary bladder, appendix, omentum etc. It passes through the deep inguinal ring acquiring the similar covering of internal spermatic fascia. It also acquires the covering of cremasteric fascia in the inguinal canal. In order to separate it therefore from the spermatic cord, the line of cleavage with the above fasciae must be sought for. It may extend from the deep inguinal ring to the superficial inguinal ring, in which case it is called the indirect or oblique hernia. If it enters through the posterior wall made up of conjoint tendon (medially) and transversalis fascia (laterally), it is called a direct hernia.
A hernia is repaired by removing the hernial sac after the reduction of the hernia and then reconstructing the inguinal canal using stitches that reduce its size.
Other types of hernia exist in the anterior abdominal wall. All anterior abdominal wall hernias are said to be external hernias as opposed to the internal hernias which occur in the peritoneal and other cavities of the body.
Other external hernia includes
Interstitial hernia (passes through the muscle fibers )
Epigastric hernias – through linea alba above the umbilicus
Lumbar hernia (found a the lumbar triangle)
.Blood supply to the anterior abdominal wall
From Mahran Z El-Din MN El-Eishi H Surgical, surface and radiological Anatomy. Cairo: University Book House, 1974, p 15
Electronic School of Medicine
Creator: Oluwole Ogunranti