2031 continued: the abdomen

What are the divisions of the anterior abdominal wall?

four quadrants and nine regions

What divides the quadrants of the abdominal wall?

a median and transumbilical plane

What divides the regions of the abdominal wall?

• 2 vertical planes (midclavicular to midinguinal points)

• 1 upper horizontal plane (transpyloric)

• 1 lower horizontal (transtubercular)

What are the quadrants of the abdomen?

right and left upper quadrant + right and left lower quadrant

What are the regions of the abdomen?

midline: epigastric, umbilical, hypogastric

R and L: hypochondriac, lumbar, inguinal

What are the layers of the anterior abdominal wall?

1. skin

2. superficial fascia (camper’s: fatty, scarpa’s: membranous)

3. muscles and fascia (lateral and anterior)

4. transversalis fascia

5. extraperitoneal fatty tissue

6. parietal peritoneum

What are the lateral muscles of the abdomen?

external oblique, internal oblique, transversus abdominus

What are the anterior muscles of the abdomen?

anterior rectus sheath, rectus abdominus, posterior rectus sheath

What are the attachments of external oblique (abdomen)?

origin: lower 8 ribs

insertion: iliac crest, pubic tubercle and linea alba

What are the attachments of internal oblique (abdomen)?

origin: thoracolumbar fascia, iliac crest and inguinal ligament

insertion: 10-12th rib, linea alba, pubic crest

What are the attachments of transversus abdominus (abdomen)?

origin: 7th-12th rib, thoracolumbar fascia, iliac crest, inguinal ligament

insertion: xiphisternum, linea alba, pubic crest

What is the orientation of fibres of the external oblique (abdomen)?

down and medial

What is the orientation of fibres of the internal oblique (abdomen)?

up and medial

What is the role of rectus abdominus?

flexes the trunk

What are the attachments of rectus abdominus?

origin: pubic symphysis and pubic crest

insertion: ziphoid process and 5-7th costal cartilage

What is the rectus abdominus?

the ‘six pack’ with tendinous ridges

What are the features of the anterior rectus sheath (in front of rectus abdominus?

external oblique aponeurosis (2 layers) and internal oblique aponeurosis (posterior layer)

What are the features of the posterior rectus sheath (behind rectus abdominus)?

internal oblique aponeurosis (anterior layer) and transverse abdominus aponeurosis (2 layers)

What part of the abdomen is the rectus sheath divided into anterior and posterior?

upper 3/4

What is the arcuate line?

free lower margin of deficiency in lower fourth of rectus sheath as aponeurosis of all 3 muscles pass in front of rectus abdominus

What are some features of the peritoneum?

thin, transparent, serous membrane of the abdominopelvic cavity

2 layers: parietal and visceral

What is the nerve supply of the anterior abdominal wall?

• intercostal nerves (T7-T11): lateral and anterior cutaneous nerves

• subcostal nerve (T12)

• first lumbar nerve (L1): iliohypogastric and ilioinguinal

Where do the intercostal nerves run in the abdomen?

between 2nd and 3rd layers (internal oblique and transversus abdominus)

What is the blood supply of the anterior abdominal wall?

• femoral artery (superficial circumflex iliac and superficial epigastric)

• external iliac artery (deep circumflex iliac and inferior epigastric)

• aorta (posterior intercostal, subcostal, lumbar)

• internal thoracic artery (superior epigastric and musculophrenic)

What is the venous drainage of the anterior abdominal wall?

• thoracoepigastric vein (lateral thoracic→ axillary and superficial epigastric→ femoral)

• tributaries of great saphenous vein

• umbilical plexus

• superior and inferior epigastric veins

• posterior intercostal and subcostal veins

• lumbar veins

What is the lymphatic drainage of the anterior abdominal wall?

umbilical watershed (in 4 directions) communicates with other regions

What is the inguinal canal?

a tunnel passing obliquely through the layers of the abdominal wall (formed by deficiencies in muscles)

Where does the inguinal canal start and end?

start: deep inguinal ring (in transversalis fascia)

end: superficial inguinal ring (split in external oblique fascia)

What are the boundaries of the inguinal canal?

roof: lower arching edge of internal oblique and transversus abdominis

floor: lower edge of external oblique fascia (forming inguinal ligament)

anterior: external oblique and internal oblique

posterior: transversalis fascia and conjoint tendon

What is the function of the inguinal canal?

provides a passage for developing testes to reach scrotum (male)

What does the inguinal canal transmit in the female?

round ligament of uterus and ilioinguinal nerve (and vessels)

What does the inguinal canal transmit in the male?

spermatic cord and ilioinguinal nerve (and vessels)

What is the peritoneal cavity?

a potential space between the 2 layers of peritoneum (parietal and visceral) → it is a potential space because the organs are packed closely together

What are the intraperitoneal viscera?

mobile and unpaired organs that have invaginated into the peritoneal cavity and have a mesentery (supply systems)

What are the retroperitoneal viscera?

fixed paired and unpaired viscera that lie behind the peritoneum (the deepest organs against the posterior abdominal wall)

What organs are unpaired intraperitoneal?

• gut (alimentary canal)

• liver and gall bladder

• spleen

What organs are unpaired retroperitoneal?

• most of duodenum

• pancreas

• ascending and descending colon

What organs are paired retroperitoneal?

• adrenal glands

• kidneys and ureters

What is a mesentry?

a double fold of peritoneum connecting an organ to the body wall which allows neurovascular communication and enables the viscera to be mobile

What are some of the mesenteries?

• the mesentery (jejunum and ileum)

• transverse mesocolon (transverse colon)

• sigmoid mesocolon (sigmoid colon)

• mesoappendix (appendix)

What is the omentum?

a double layered extension of visceral peritoneum passing from one organ to another organ or structure

What are the omentums in the abdominal cavity?

• lesser omentum (from lesser curvature of stomach)

• greater omentum (from greater curvature of stomach)

What are the ligaments of the peritoneum?

a double layer of peritoneum connecting an organ with another organ to the abdominal wall

What are the features of the GI tract?

a muscular wall of the alimentary canal that extends from the mouth to the anus and consists of 3 muscle layers

What are the associated intra-abdominal organs of the GI tract?

• spleen

• pancreas

• liver

• gall bladder

What are the sections of the abdominal GI tract?

foregut, midgut and hindgut

What are the components of the foregut?

• lower oesophagus

• stomach

• duodenum (proximal)

• (spleen pancreas, liver, gall bladder)

What are the components of the midgut?

• distal duodenum

• jejunum and ileum

• proximal large intestine (approx 2/3 until near end transverse colon)

What are the components of the hindgut?

• distal large intestine (approx 1/3)

What is the arterial supply of the foregut?

celiac trunk (splenic artery, common hepatic, left gastric)

What is the arterial supply of the midgut?

superior mesenteric

What is the arterial supply of the hindgut?

inferior mesenteric

What are the sites of digestion?

stomach and duodenum

What are the sites of absorption?

smal intestine

What are the sites of reabsorption?

ascending colon

What vertebral level does the celiac trunk commence?

T12

What vertebral level does the superior mesenteric artery commence?

L1

What vertebral level does the inferior mesenteric artery commence?

L3

What are the features of the oesophagus?

muscular 25cm long tube that transmits a bolus of food from the laryngopharynx to the stomach

What level does the oesophagus begin?

C6

What level does the oesophagus pierce the diaphragm?

T10

What are the features of the stomach?

a J-shaped muscular bag in the epigastric and umbilical regions with 2 curvatures (greater and lesser)

What is on the internal muscular surface of the stomach?

rugae (longitudinal ridges)

What are the parts of the small intestine?

• duodenum

• jejunum

• ileum

What are the features of the duodenum?

shortest, widest and most fixed part of small intestine that is horseshoe shaped and encloses the head of the pancreas

What are the features of the jejunum?

begins at the duodenojejunal flexure and lies mostly in the umbilical region, it is wider and thicker walled and deep red in colour

What are the features of the ilium?

end in right iliac fossa at ileocecal junction, lies in hypogastric and right iliac regions, it is narrower and thin walled and pale pink in colour

What are the features of the large intestine?

extends from caecum to anus

• teniae coli (3 thickened bands of longitudinal muscle)

• haustra (sacculatios betwen teniae)

• epiploic/omental appendices (small fat filled pouches of omentum)

What is the caecum?

1st part of large intestine that is continues with the ascending colon and located in the right iliac quadrant

What is the vermiform appendix?

a worm shaped tube that joins the caecum inferior to the ileocecal junction

What is the order of the parts of the colon?

• caecum

• ascending colon

• transverse colon

• descending colon

• sigmoid colon

What are the features of the spleen?

largest lymphatic organ that is roughly the shape and size of a clenched fist

What is the function of the spleen?

proliferation of WBC and filteration of RBC

What are the features of the pancreas?

digestive gland that has a head, neck and tail and opens into the duodenum (which is lies within the ‘C’ loop of)

What is the function of the pancreas?

release digestive juice to gut and secretes insulin

What are the features of the liver?

largest gland in the body

What is the function of the liver?

stores glycogen and secretes bile, filters toxins from blood

What are the features of the gall bladder?

pear shaped bag in the gall bladder fossa on the visceral surface of the liver

What is the function of the gall bladder?

stores and concentrates bile secreted by liver

What forms the portal vein?

union of superior mesenteric and splenic veins

What does the portal vein drain?

• spleen

• pancreas

• gall bladder

• abdominal GI tract

What is the function of the portal vein?

carries blood to the liver to be detoxified (it then enters the IVC via 3 hepatic veins)

What are the sites of the portal/systemic anastomes?

• lower end of oesophagus

• umbilicus

• rectum

What is the innervation of the foregut?

celiac plexus and vagal trunks

What is the innervation of the midgut?

superior mesenteric plexus and vagal trunks

What is the innervation of the hindgut?

inferior mesenteric plexus and pelvic splanchnic nerves

Where might pain from the foregut refer to?

T7-T9 epigastric quadrant

Where might pain from the midgut refer to?

T10 umbilical quadrant

Where might pain from the hindgut refer to?

T11-L1 hypogastric quadrant

What features/organs are in the R hypochondriac quadrant?

• liver

• gallblader

• right kidney

• small intestine

What features/organs are in the L hypochondriac quadrant?

• spleen

• colon

• left kidney

• pancreas

What features/organs are in the epigastric quadrant?

• stomach

• liver

• pancreas

• duodenum

• spleen

• adrenal glands

What features/organs are in the R lumbar quadrant?

• gallbladder

• liver

• right colon

What features/organs are in the L lumbar quadrant?

• descending colon

• kidney

What features/organs are in the R iliac quadrant?

• appendix

• caecum

What features/organs are in the L iliac quadrant?

• descending colon

• sigmoid colon

What features/organs are in the umbilical quadrant?

• umbilicus

• duodenum

What features/organs are in the hypogastric quadrant?

• urinary bladder

• sigmoid colon

• female reproductive organs

What is the bony framework of the posterior abdominal wall?

5 lumbar vertebrae, ilium and 12 ribs

What are the muscular components of the posterior abdominal wall?

• psoas major

• quadratus lumborum

• iliacus

• transversus abdominis

• diaphragm (roof)