Chapter 1 - Anterior Abdominal Wall (until pyramidalis) Flashcards
Definition and position of umbilicus
- Normal scar on anterior abdominal wall
- Remnants of root of umbilical cord
- in anterior median line
- level of L3-L4
- lower in infants and persons with pendulous abdomen
Anatomical importance of umbilicus
- Lymph and venous blood flow upwards above umbilical plane and downwards below
- Skin around by T10 segment of spinal cord
- Portal veins anastamose with systemic veins
Embryological importance of umbilicus
- Meeting point of 4 folds of embryonic plate - 2 lateral, head, tail
- Meeting point of digestive, excretory, vascular system
Persistence of vitellointestinal duct
Patent - faecal fistula at umbilicus
Proximal part - Meckel’s diverticulum
Middle part - enterocoele
- May form raspberry red or cherry red tumors
Layers of superficial fascia
- Superficial, fatty layer - fascia of Camper
2. Deep, membranous layer - fascia of Scarpa
Fatty layer of superficial fascia
- continuous with superficial fascia of nearby parts
- in penis, devoid of fat
- in scrotum, replaced by dartos muscle
Membranous layer of superficial fascia
- continuous with membranous layer of superficial fascia of perineum - Colles fascia
- prevents passage of extravasted urine backwards into ischiorectal fossa due to rupture of urethra
- thickened in median plane to form suspensory ligament, fundiform ligament of penis/clitoris
- Above umbilicus, it merges with fatty layer
Line of attachment of membranous fascia
- Holden’s line
- Pubic tubercle
- Body of pubis
- Pubic arch
- Posterior border of perineal membrane
Anterior cutaneous N of AAW
Thoracic N - T7-T12, L1
- Enter abdominal wall from intercostal spaces
- pass b/w internal oblique and transversus
- pierce posterior lamina of internal oblique aponeurosis
- enter rectus sheath
- pierce rectus muscles
- divide into medial and lateral branches
- Iliohypogastric and ilioinguinal do not enter rectus sheath
- Subcostal supplies pyramidalis
Lateral cutaneous N of AAW
T10-T11 intercostal N
- pierce external intercostal
- divide into anterior andposterior branches
- supply skin on side of abdomen
lateral cutaneous branches of subcostal and iliohypogastric N (T12, L1)
- descend over iliac crest
- supply skin of gluteal region
Cutaneous A of AAW
- Anterior cutaneous A - from superior, inferior epigastric A
- Lateral cut. A - from lower intercostal A
- Superficial inguinal A - from femoral
- Superficial epigastric A - skin upto umbilicus
- Superficial external pudendal A - skin of external genitalia
- Superficial circumflex iliac A - skin of abdomen, thigh
Superior vena caval blockage vein path
Brachiocephalic -> Subclavian -> Axillary -> Lateral thoracic -> Thoracoepigastric -> Superficial epigastric -> Great saphenous -> Femoral -> IVC
Caput Medusae
- When portal vein, SVC or IVC are obstructed, superficial abdominal V dilate to provide collateral circulation
- Dilated V radiate from umbilicus forming caput medusae
- Mainly seen in portal obstructions
Origin of external oblique M
- As 8 slips from outer surface of shafts of lower 8 ribs
- Downward, forward, medially
Insertion of external oblique M
-Aponeurosis Xiphoid process Linea alba Pubic symphysis Pubic crest
Nerve supply of external oblique M
Lower 6 thoracic N
Properties of external oblique M
- Upper 4 slips interdigitate with serratus anterior, lower 4 with latissimus dorsi
- aponeurosis has free margin which forms inguinal ligament
- aponeurosis forms anterior wall of rectus sheath
- forms triangular superficial inguinal ring above pubic crest
Origin of internal oblique M
- Lateral 2/3 of inguinal ligament
- Anterior 2/3 of iliac crest
- Thoracolumbar fascia
- Upwards, forwards, medially
Insertion of internal oblique M
- Uppermost directly into lower 4 ribs
- Aponeurosis into:
- 7, 8, 9 costal cartilages
- xiphoid process
- linea alba
- pubic crest
- pectineal line of pubis
Nerve supply of internal oblique M
- Lower 6 thoracic N
- L1 N
Properties of internal oblique M
- In upper 3/4 aponeurosis splits into anterior, posterior lamina
- Anterior lamina passes in front of rectus abdominis and posterior lamina behind.
- Posterior lamina ends to form linea semicircularis/ arucate line
- Lower 1/4 aponeurosis is single layer
- Forms conjoint tendon and cremaster muscle
Origin of transversus abdominis M
- Lateral 1/3 of inguinal ligament
- Anterior 2/3 of iliac crest
- Thoracolumbar fascia
- Inner surface of lower 6 costal cartilages
- Horizontally forwards
Insertion of transversus abdominis M
-Aponeurosis Xiphoid process Linea alba Pubic crest - Lowest fibres + internal oblique form conjoint tendon
Nerve supply of transversus abdominis M
- Lower 6 thoracic N
- L1 N
Properties of transversus abdominis M
- In upper 3/4, aponeurosis passes behind rectus muscle
- Lower edge contributes to arcuate line
- Lower 1/4, aponeurosis forms anterior wall of rectus sheath.
Origin of rectus abdominis M
- Lateral head - lateral part of pubic crest
- Medial head - Medial pubic crest, anterior pubic ligament
- Vertically upward
Insertion of rectus abdominis M
Xiphoid process
7th, 6th, 5th costal cartilages
Nerve supply of rectus abdominis M
Lower 6 thoracic N
Properties of rectus abdominis M
- It has 3 transverse fibrous bands that divide it into small parts
a. opp. umbilicus
b. opp. free end of xiphoid
c. b/w both - They make muscle powerful
Actions of muscles of AAW
- Tone of M provide firm, elastic support for abdominal viscera against gravity
- Can compress viscera for expulsive acts like vomiting, micturition, defecation, paturition
- External oblique and depress/compress lower thorax for forceful expiration, sneezing, coughing
- Movements of trunk:
a. Flexion of trunk/spine - rectus abdominis
b. Lateral flexion of trunk - obliques
c. Rotation of trunk - ext. oblique + opp. int. oblique
Formation and attachments of inguinal ligament
FORMATION - by lower border of ext. oblique - aponeurosis is thickened and folded upon itself - from anterior superior iliac spine to pubic tubercle ATTACHMENTS - Lower border - fascia lata - Lat 2/3 - Int. oblique - Lat 1/3 - transversus abdominis - Middle - Cremaster
Relations of inguinal ligament
Upper surface forms floor of inguinal canal
Lodges spermatic cord and round ligament of uterus
Extensions of inguinal ligament
- Lacunar ligament
- Ligament of Cooper
- Reflected part of inguinal ligament
- Intracrural fibres that arise from middle and arch over superficial inguinal ring
Lacunar ligament
- Triangular
- Ant: Medial end of inguinal ligament
- Post: pecten pubis
- Horizontal
- Supports spermatic cord
- Forma medial boundary of femoral ring
Ligament of Cooper
- Extension from post. part of lacunar ligament
- Attached to pecten pubis
Reflected part of inguinal ligament
- fibres pass upwards and medially from superficial inguinal ring(SIR)
- lies behind SIR and in front of conjoint tendon
Conjoint tendon
- fusion of lowest fibres of int. oblique and transversus
- attached to pubic crest, pecten pubis
- Medially, continuous with anterior wall of rectus sheath
- Laterally, free
- Strengthens abdominal wall at site where it is weakened by SIR
Cremaster muscle
- muscle fasiculi embedded in cremasteric fascia
- fasiculi form superficial loops from upper surface of inguinal ligament
- form deep loops from pubic crest, conjoint tendon
- fully developed only in male
- lies deep to external spermatic fascia
Nerve supply of cremasteric muscle
Genital branch of genitofemoral N
Action of cremaster
Helps suspend and elevate testes
Closes SIR when intra-abdominal pressure increases
Cremasteric reflex
- On stroking upper part of medial side of thigh, cremaster reflexively contracts
- More brisk in children
- In upper motor N leisions abover L1, reflex is lost
Pyramidalis
- small triangular
- from anterior surface of body of pubis
- fibres - upwards, medially
- inserted into linea alba
- supplied by subcostal N T12
- tensor of linea alba
