anterior abdominal wall and GI tract Flashcards
how is the abdomen divided?
(1st - four quadrants, UL, UR, LL, LR)
then into nine regions:
Horizontal lines -
the transpyloric line (9th costal cartilage, going through pylorus of stomach, or L1)
Second horizontal line is intertubercular line, going through the pelvic tubercules
Goes through L5
Vertical lines -
Two midclavicular lines
from top to bottom, on the left and right side, you’ve got hypochondrium, lumbar and iliac
then the middle column goes epigastric, umbilical and hypogastric
thew abdominal wall has two groups of muscles, flat and vertical.
Explain the flat group of muscles
Lie laterally (on the sides) on the abdomen, in order of front to back:
External oblique - most superficial, fibres run medially and downwards to midline (same direction as external intercostal muscles). rotation and twisting
Internal oblique - deep to external one, fibre perpendicular to external oblique (medially and upwards). causes flexion of the trunk
transversus abdominis - named as such because the fibres run horizontally
Deep to internal oblique
Can also see the posterior wall of rectus sheath. transversalis fascia runs beneath. supports back?
what is the rectus sheath?
a multi-layered aponeurosis (an aponeurosis is flat thin sheaths of connective tissue where muscle can attach/insert, similar-ish to tendon but not the same).
It’s the big white-ish bit in the centre of the abdomen.
***Encloses the rectus abdominis muscles
the rectus sheath - what is it composed of (anterior and posterior walls)?
The rectus sheath has an anterior and posterior wall
these walls are composed of a fusion of the aponeuroses (they have their own) of the three flat muscles mentioned
Anterior wall = aponeuroses of external oblique + half of internal oblique
Posterior wall = aponeuroses of other half of internal oblique, and all of transversus abdominis.
They fuse at the midline, linea alba
there are two vertical muscles of the abdominal wall -
explain the one we need to know
Rectus abdominis - the long muscle spanning the entire Ant. Abd. wall, either side of the midline.
it extends from the xiphoid process to the pubic crest
Has fibrous bands intersected within, known as tendinous intersections (horizontal ab marks of six pack)
Rectus abdominis lies within the rectus sheath
flexion of the lumbar spine
define the location of the abdomen
inferior to diaphragm and above the pelvic rim
which nerves innervate the muscles of the anterior abdominal wall?
spinal nerves T8-T12
blood supply of the anterior abdominal wall -
anteriorly?
laterally?
laterally the abdominal wall is supplied by segmental lumbar arteries arising directly from the abdominal aorta
anteriorly, the abdominal wall is supplied by the sup. and inf. epigastric arteries, arising form the int. and ext. iliac arteries respectively
what are the functions of the anterior abdominal wall muscles?
● Protect the abdominal viscera from injury
● Form a firm but flexible wall keeping the abdominal viscera within the cavity
● Assist in quiet and forced expiration
● Increase intra abdominal pressure during coughing, vomiting, micturition and defecation
peritoneum of the peritoneal cavity - what is it made up of and how is it structured?
Defined as a serous lining of the abdomen. Both layers are made up of simple squamous epithelial cells (mesothelium)
Has two layers -
Parietal lines inner aspect of the wall
Visceral peritoneum covers the structure and organs (so visceral is deeper)
Peritoneal cavity between the two layers - contains small amount of peritoneal fluid to allow smooth movement of organs sliding past each other
how does the peritoneum develop to have two layers?
pain and peritoneum?
Duct tube pushes through the peritoneum, and the bit it takes with it, that invaginates, is then the visceral peritoneum
Pain from the visceral peritoneum is referred to areas of skin (dermatomes) which are supplied by the same sensory ganglia and spinal cord segments
define intraperitoneal and retroperitoneal organs
Intraperitoneal organs -
enveloped by visceral peritoneum, which covers the organ both anteriorly and posteriorly. Examples include the stomach, liver and spleen
Retroperitoneal organs -
Retroperitoneal organs are not associated with visceral peritoneum; they are only covered in parietal peritoneum, and that peritoneum only covers their anterior surface
what are the retroperitoneal organs?
SAD PUCKER
S = Suprarenal (adrenal) Glands
A = Aorta/IVC
D =Duodenum (except the proximal 2cm, the duodenal cap)
P = Pancreas (except the tail)
U = Ureters
C = Colon (ascending and descending parts)
K = Kidneys
E = (O)esophagus
R = Rectum
which are the intraperitoneal organs?
stomach, spleen, liver, first and fourth parts of the duodenum, jejunum, ileum, transverse, and sigmoid colon, tail of pancreas
what is mesentery?
organs that are m______ have it
what does it contain?
Suspends from posterior abdominal wall, it’s a double layer of visceral peritoneum, connecting an intraperitoneal organ (SI and part of LI) to the posterior abdominal wall
Required for mobile organs
Contains fat, makes it identifiable as seen in image
Contains BVs, lymphatics and nerves for an organ
grater and lesser omentum?
gastrocolic ligament?
mesentery?
suspensory ligament?
transverse mesocolon?
greater and lesser omentum = double peritoneal folds (not mesentery i think) on lesser and greater curves (not fundus?) of stomach)
greater omentum connects to stomach and loosely to transverse colon, with thew gastrocolic ligament in the middle
mesentery seems to just be for jejunum and ileum
suspensory ligament = peritoneal folds at the duodenojejunal flexure
transverse mesocolon = mesentery of the transverse colon (and there’s the sigmoid mesocolon)
define the three regions of the gastrointestinal tract
foregut = oesophagus, stomach and first half of duodenum (can include organs like liver, pancreas and gallbladder too)
Midgut = second half of duodenum, the jejunum and the ileum, cecum and ascending colon, the first 2/3s of transverse colon
Hindgut = distal ⅓ of transverse colon, descending colon, sigmoid colon and rectum, ending at the upper anal canal
which branches of the abdominal aorta supply what?
Celiac trunk supplies foregut
Superior mesenteric artery supplies midgut
Inferior mesenteric artery supplies hindgut
the first section of the small intestine is the duodenum.
what is it’s structure (four sections), location and associations?
C shaped, continues on from pylorus of stomach, has the widest lumen.
Has four parts :
*Superior (the only intraperitoneal part)
*Descending- where the major duodenal papilla is (opening of the bile duct and main pancreatic duct) , *Inferior (3rd part crosses IVC, aorta and vertebral column
*Ascending
Location - above level of the umbilicus
Most of its length is retroperitoneal (just not the proximal 2cm, duodenal cap)
Associations -
Inferior vena cava and abdominal aorta lie posterior to the duodenum
jejunum - location and blood supply?
ileum?
second part of small intestine beginning at duodenojejunal flexure, located in upper left quadrant
entirely intraperitoneal
supplied by jejunal arteries form the SMA
ileum is in lower right quadrant
ileal and ileocolic arteries form SMA
what are the four main differences between the jejunum and ileum?
Hard to tell apart externally
- Jejunum has more plicae circulares (mucosa folds with microvilli for nutrients absorption) compared to ileum, as more absorption of nutrients occurs in J
2.Jejunum has longer vasa recta (straight arteries)
- Arteries form loops called arterial arcades. Jejunum has LESS of these than ileum
Internal ileum has lymph nodules known as Peyer’s patches found more at terminal end
***All have mesentery and are intraperitoneal
what are the regions of the large intestine and where does it start?
what is found at it’s terminal end?
Goes caecum -ascenidng colon - transverse colon - Descending colon -Sigmoid colon
Start = ileocecal valve, in the right iliac region (fossa)
Towards the terminal end of is the appendix which also has mesentery and is therefore quite mobile
go along the large intestine, explaining it’s parts.
cecum - up, the ascending colon
Bends at the hepatic flexure - becomes transverse colon (now has/enters mesentery so suspends from posterior abd. Wall)
Bends again at splenic flexure to become descending colon (leaving the mesentery) -
S shape at end of that is the sigmoid colon which enters the pelvis
Continuous into the rectum, continues into the anal canal
which parts of the large intestine are intra vs retroperitoneal?
Ascending and descending are retroperitoneal, the transverse and sigmoid are intra as they also have mesentery
