Abdominal wall & omentum Flashcards
Describe the 9 regions of the abdominal cavity
Divided along mid-clavicular, subcostal and trans-tubercular planes.
Right/Left Hypochondrium
Epigastric
Right/Left Lumbar (flank)
Umbilical
Right/Left Inguinal (iliac fossa)
Pubic (suprapubic)
Describe the 4 quadrants
Divided along median and trans-umbilical planes.
Right/Left Upper Quadrants
Right/Left Lower Quadrants
Describe the antero-abdominal wall
Musculo-aponeurotic, posteriorly formed by lumbar region of vertebral column and the muscles attached. Superiorly bounded by the cartilages of 7th–10th ribs, xiphoid process; inferiorly by iliac crest, inguinal ligament, pubic crests, and pubic symphysis.
Skin, subcutaneous tissue with varying amount of fat. Inferior to umbilicus, deep part to fat a fibrous layer is present. 2 layers: superficial fatty layer (Camper fascia) & deep membranous layer (Scarpa fascia) of subcutaneous tissue. Thin investing layer of deep fascia over the three layers of muscles. Fascia transversalis, Extraperitoneal fat, Parietal peritoneum.
All three flat muscles are continued anteriorly and medially as strong, sheet-like aponeuroses. Between midclavicular line and midline, the aponeuroses form aponeurotic, rectus sheath enclosing the rectus abdominis muscle. The aponeuroses then interweave with the opposite side, forming a midline raphe the linea alba (L. white line), which extends from xiphoid process to pubic symphysis. In thin muscular people, a groove is visible in the skin overlying the linea alba.
Rectus abdominis- long, broad, vertical strap-like muscle, separated by linea alba, lateral margin linea semilunaris. Tendinous intersections anchor transversely the muscle with the anterior layer of the rectus sheath (three or more, at xiphoid, umbilicus and midway between two). In muscular people, the intersections are indicated by grooves in the skin and muscle between the tendinous intersections bulge outward when tensed.
Describe the inguinal ligament
Marks anterior boundary between the abdomen and thigh. An inferior thickening of the external oblique muscle. The thickened, inrolled free inferior margin of external oblique aponeurosis extends between ASIS and pubic tubercle as the inguinal ligament (Poupart ligament). It serves as a retinaculum (retaining band) for the muscular and neurovascular structures passing deep to it to enter the thigh.
Describe the inguinal canal
Formed embryologically - 4 cm long oblique passage through the anterior abdominal wall in the inguinal regions. Extends between a deep and superficial inguinal ring.
Deep inguinal ring: opening in fascia transversalis, located superior to the midpoint of the inguinal ligament.
Superficial inguinal ring: opening in external oblique aponeurosis, lies superolateral to the pubic tubercle.
Each canals floor is the medial half of the inguinal ligament
Describe the formation of the inguinal canal
The testes develop in the extraperitoneal connective tissue in the lumbar region of the posterior abdominal wall. Gubernaculum is a fibrous tract connecting the primordial
testis to the future site of descent. A peritoneal diverticulum, the processus vaginalis, traverses the developing inguinal canal, carrying muscular and fascial layers of the anterolateral abdominal wall before it as it enters the primordial scrotum.
Describe the boundaries of the inguinal canal
Anterior wall: external oblique aponeurosis, internal oblique muscle.
Posterior wall: transversalis fascia, conjoint tendon (combination of IO & TA aponeurosis)
Roof: transversalis fascia, arches of IO & TA aponeurosis
external oblique aponeurosis
Floor: gutter of infolded inguinal ligament, medially by lacunar ligament.
What is inguinal hernia and what causes it?
Inguinal canal causes weakness of abdominal wall.
Increased intra-abdominal pressure due to:
chronic cough
chronic constipation
occupational lifting of heavy weights
athletic effort
Unilateral or bilateral, direct or indirect
Describe the peritoneum
Thin, transparent, semi-permeable, serous membrane. Lines the walls of the abdominopelvic cavity and organs - parietal and visceral layers are continuous.
Parietal: supplied by somatic nerves, sensitive to pressure, pain, heat and cold, and laceration.
Visceral: supplied by visceral nerves, insensitive.
Peritoneal cavity: potential space of capillary thinness between the parietal and visceral layers of peritoneum - peritoneal fluid.
At its inferior aspect, peritoneum drapes over the superior aspect of the pelvic organs - sub-peritoneal
Forms pouches - male: rectovesical pouch, female: vesico-uterine pouch, recto-uterine pouch.
These pouch are part of the greater sac.
What are intra-peritoneal organs?
Almost completely covered by visceral peritoneum, does not mean inside the peritoneal cavity. Minimally mobile.
eg stomach, liver, jejunum, ileum, & spleen.
What are retroperitoneal organs?
Partially covered with peritoneum (usually one surface eg anterior surface). Located in retroperitoneum.
eg kidney, pancreas
What are organs covered with mesentery?
Covered in visceral peritoneum - forms double layer (mesentery). Mesentery suspends the organ from the posterior abdominal wall - very mobile.
State the components of the GI tract
Oesophagus
Stomach
The small intestine is around 7m long and, from proximal to distal, made up of:
The duodenum (short)
The jejunum (~3m)
The ileum (~4m)
The large intestine, from proximal to distal, is made up of:
Caecum
Appendix
Colon
Ascending colon
Transverse colon
Descending colon
Sigmoid colon
The rectum
The anal canal
The anus
Describe the peritoneal attachments
Double layer folds of peritoneum.
Attach organs to each other or to abdominal wall
Act as pathway for neurovascular structures going to supply the organ/wall
Secondary to growth and rotation of GI tract during embryology
Visible during dissection and surgery
Caecum - intraperitoneal
ascending colon - secondarily retroperitoneal
transverse mesocolon & transverse colon - intraperitoneal - highly mobile, has own mesentery
descending colon - secondarily retroperitoneal
sigmoid mesocolon
sigmoid colon - intraperitoneal - quite mobile, has own mesentery
Describe the peritoneal cavity
The omenta divide the peritoneal cavity into a greater sac and a lesser sac. The 2 sacs communicate through the omental foramen/epiploic foramen.
Portal triad (hepatic artery, bile duct, portal vein): lies in free edge of lesser omentum.
Describe paracentesis/abdominocentesis
Collection of excess fluid in peritoneal cavity - ascitic - patient has ascites. Can be drained.
Needle must be placed lateral to the rectus sheath and superior to ASIS - avoids inferior epigastric artery - ascends in anterior abdominal wall (deep to rectus abdominis)
Inferior epigastric arises from the external iliac - just medial to the deep inguinal ring.
Use ultrasound guidance if available
Describe the appendix & caecum
Both lie in the right iliac fossa. Position of appendix is variable:
most often retrocaecal, variety accounts for the different ways in which patients can present with appendicitis.
Appendiceal orifice on posteromedial wall of caecum - corresponds to McBurney’s point on anterior abdominal wall - 1/3rd of the way between right ASIS to umbilicus. Maximum tenderness in case of appendicitis (in theory).
Describe the sigmoid colon
Lies in left iliac fossa. Has a long mesentery (sigmoid mesocolon) - gives considerable degree of movement.
Disadvantage: sigmoid colon at risk of twisting around itself - sigmoid volvulus. Clinically results in bowel obstruction - risk of infarction if left untreated.
