Anterior Abdominal Wall Abdomen Pelvis Perineum Unit Lecture

Anterior Abdominal Wall Abdomen, Pelvis & Perineum Unit Lecture 1 ﺣﻴﺪﺭ ﺟﻠﻴﻞ ﺍﻷﻌﺴﻢ. ﺩ

Abdomen It is the region of trunk that lies between diaphragm above and pelvic inlet below. Circumferentially, it is bounded by abdominal wall. The abdominal wall is bordered as follows: • Superiorly by xiphoid process and costal margins. • Posteriorly by vertebral column. • Inferiorly by upper parts of the pelvic bones.

Anterior Abdominal Wall Abdominal wall is divided into Anterior and Posterior walls. Structure of Anterior Abdominal Wall: 1. Skin 2. Superficial fascia 3. Deep fascia 4. Muscles 5. Extraperitoneal fascia 6. Parietal peritoneum

Skin is loosely attached to the underlying structures except at the umbilicus (tethered to scar tissue). The natural lines of cleavage in the skin are constant and run almost horizontally around the trunk. The umbilicus is a scar representing the site of attachment of umbilical cord in the fetus; it is situated in the linea alba

Superficial Fascia – fatty layer It is divided into an outer fatty layer (Camper’s fascia) and a deep membranous layer (Scarpa's fascia). Camper's fascia contains fat and is continuous with superficial fat over the rest of the body. In men’s scrotum, the fatty layer of superficial fascia loses its fat and represented as a thin layer of smooth muscle (dartos muscle). In women, this superficial layer retains some fat and is a component of the labia majora.

Superficial Fascia – Membranous layer Scarpa's fascia is thin membranous layer & has the following relations Laterally, continuous with superficial fascia of the back. Superiorly, continuous with superficial fascia of the thorax. Inferiorly, fuses with the deep fascia of thigh (fascia lata) one fingerbreadth below the inguinal ligament. In the midline inferiorly, the membranous layer of fascia is not attached to the pubis but forms a tubular sheath for the penis (or clitoris).

Superficial Fascia – Membranous layer In the perineum, fuses with perineal superficial fascia (Colles' fascia) and with perineal body and posterior margin of the perineal membrane. In men, it blends with fatty layer as they both pass over the penis, forming the superficial fascia of the penis, before they continue into the scrotum to form dartos fascia. In women, it continues into labia majora and anterior part of the perineum.

Deep Fascia of Anterior Abdominal Wall It is merely a thin layer of connective tissue covering the muscles and lies immediately deep to the membranous layer of superficial fascia

Muscles of Anterior Abdominal Wall They consist of three broad thin sheets of muscles that are aponeurotic in front (external oblique, internal oblique & transversus abdominis). There is also a wide vertical muscle (rectus abdominis)on either side of the midline.

Muscles of Anterior Abdominal Wall As aponeuroses of these three sheets pass forward, they enclose rectus abdominis to form rectus sheath. Lower part of rectus sheath may contain a small muscle (pyramidalis)

External Oblique Shape: broad, thin, muscular sheet. Origin: from outer surfaces of lower eight ribs Insertion: xiphoid process, linea alba, pubic crest, pubic tubercle, and anterior half of the iliac crest. A triangular-shaped defect in external oblique aponeurosis lies above and medial to pubic tubercle known as superficial inguinal ring. Between anterior superior iliac spine and pubic tubercle, lower border of the aponeurosis is folded backward on itself, forming inguinal ligament. From the medial end of the ligament, lacunar ligament extends backward and upward to pectineal line on the superior ramus of the pubis. Deep fascia of the thigh (fascia lata) is attached to the inferior rounded border of the inguinal ligament

Internal Oblique Shape: broad, thin, muscular sheet. Origin: lumbar fascia, anterior 2/3 of iliac crest, lateral 2/3 of inguinal ligament. Insertion: lower borders of lower three ribs (10 th, 11 th & 12 th) & their costal cartilages, xiphoid process, linea alba & symphysis pubis. Its fibres run at right angles to external oblique fibres (upward and forward).

Internal Oblique It has a lower free border that arches over spermatic cord (or round ligament of uterus) and attached to pubic crest and pectineal line. The lowest tendinous fibers are joined by similar fibers from transversus abdominis to form conjoint tendon As the spermatic cord (or round ligament of the uterus) passes under the lower border of the internal oblique, it carries with it some of the muscle fibers that are called cremaster muscle. The cremasteric fascia is the term used to describe the cremaster muscle and its fascia.

Transversus Abdominis Shape: thin sheet of muscle. Origin: from deep surface of lower six costal cartilages (interdigitating with the diaphragm), lumbar fascia, anterior two thirds of iliac crest, and lateral third of inguinal ligament. Insertion: into xiphoid process, linea alba, and symphysis pubis. It lies deep to internal oblique, and its fibers run horizontally forward. The lowest tendinous fibers join similar fibers from internal oblique to form conjoint tendon. Posterior borders of internal oblique and transversus muscles are attached to lumbar spines by lumbar fascia.

Rectus Abdominis Shape: long strap muscle extending along anterior abdominal wall. Origin: by two heads, from the front of symphysis pubis and pubic crest. Insertion: into 5 th, 6 th & 7 th costal cartilages and xiphoid process. When it contracts, its lateral margin forms a curved ridge (linea semilunaris) that extends from tip of 9 th costal cartilage to pubic tubercle. It is divided into distinct segments by three transverse tendinous intersections: one at the level of xiphoid process, one at the level of umbilicus, and one halfway between these two. These intersections are attached to anterior wall of rectus sheath only. Rectus abdominis muscle is enclosed in rectus sheath formed by aponerosus of other Flat muscles.

Pyramidalis It is often absent and arises by its base from anterior surface of pubis and is inserted into linea alba. It lies in front of lower part of the rectus abdominis muscle.

Rectus Sheath It is long fibrous sheath that encloses rectus abdominis muscle and pyramidalis muscle. It is formed mainly by aponeuroses of the three lateral abdominal muscles (External Oblique, Internal Oblique & Transversus Abdominis. Contents of rectus sheath: Rectus abdominis muscle, Pyramidalis muscle, anterior rami of lower six thoracic nerves and superior and inferior epigastric vessels and lymph vessels.

Rectus Sheath Rectus sheath walls are formed of different components according to three levels. Above costal margin, anterior wall is formed by aponeurosis of external oblique. Posterior wall by thoracic wall (5 th, 6 th & 7 th costal cartilages & intercostal spaces). Between costal margin and level of anterior superior iliac spine, internal oblique aponeurosis splits to enclose rectus muscle; external oblique aponeurosis is directed in front of the muscle, and transversus aponeurosis is directed behind muscle. Between the level of the anterosuperior iliac spine and the pubis, aponeuroses of all three muscles form the anterior wall. The posterior wall is absent. The posterior wall has a free, curved lower border called arcuate line; where inferior epigastric vessels enter rectus sheath and anastomose with superior epigastric vessels.

Fascia Transversalis It is a thin layer of fascia that lines transversus abdominis muscle and is continuous with a similar layer lining the diaphragm and the iliacus muscle. The femoral sheath for the femoral vessels in the lower limbs is formed from fascia transversalis and fascia iliaca that covers the iliacus muscle.

Extraperitoneal Fat It is a thin layer of connective tissue that contains a variable amount of fat and lies between fascia transversalis and parietal peritoneum.

Nerve Supply of Abdominal Wall 1 - Anterior rami of lower six thoracic (lower five intercostal & subcostal nerves) pierce posterior wall of rectus sheath to supply rectus muscle & pyramidalis (T 12 only) 2 - First lumbar nerves (iliohypogastric & ilioinguinal nerves). They do not enter rectus sheath but iliohypogastric nerve pierces external oblique aponeurosis and ilioinguinal nerve emerges through superficial inguinal ring. They supply skin above inguinal lig. & symphysis pubis. They all pass in an interval between internal oblique and transversus muscles. T 7 Dermatome is located in the epigastrium over xiphoid process. T 10 Dermatome includes the umbilicus L 1 Dermatome lies just above inguinal ligament & symphysis pubis.

Blood Supply of Abdominal Wall Arteries: Skin near the midline: by superior & inferior epigastric arteries. Skin of the flanks: by intercostal, lumbar & deep circumflex iliac arteries. Skin in inguinal region is supplied by femoral artery (superficial epigastric & superficial circumflex iliac arteries). Veins: Superficial Veins: they form a network that radiates out from the umbilicus. Above, they are drained into axillary vein via lateral thoracic vein and, below, into femoral vein via superficial epigastric and great saphenous veins. Deep Veins: Superior & Inferior epigastric, and deep circumflex iliac veins (drain into internal thoracic & external iliac veins. Posterior intercostal veins drain into azygos Lumbar veins drain into the inferior vena cava

Lymph Drainage of the Abdominal Wall Superficial Lymph Vessels of Anterior abdominal wall: Above the umbilicus: anterior axillary (pectoral) group of nodes. Below the umbilicus: superficial inguinal nodes. Superficial Lymph Vessels of back: Above the iliac crests: posterior axillary group of nodes Below the iliac crests: Superficial inguinal nodes. Deep Lymph Vessels They follow the arteries and drain into internal thoracic, external iliac, posterior mediastinal & para-aortic (lumbar) nodes.

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