case 4 anatomy Flashcards
small intestine
The small intestine consists of the duodenum, jejunum and ileum. It extends from the pyloric sphincter to the ileocecal junction where it opens into the large intestine. It is the main site of digestion and absorption. A number of structural adaptations are present in the small intestine to increase the surface area for absorption.
plicae circulares
circular folds in the mucosa that can be seen. It increases the surface area and helps slow food for more absorption time. its not present in the large intestine. mainly in the jejunum.
microvilli
microscopic protrusions from the luminal surface of the intestinal cells
villi
finger like projections of the mucosa
mesentery
Most of the small intestine is suspended from the posterior abdominal wall by the mesentery. This arrangement ensures that the coils of the jejunum and ileum are freely mobile. The root of the mesentery is approximately 15cm long. Blood vessels, lymphatics and nerves enter at the root of the mesentery and pass through it to supply the small intestine. This arrangement prevents tangling and trapping of the neurovascular structures.
The root of the mesentery is attached to the posterior wall along a line that extends from the left side of the second lumbar vertebra to the region of which joint?
sacroiliac
duodenum
The duodenum is the first part of the small intestine and the main site of digestion. It is a C-shaped tube that is approximately 25cm long (12 finger breadths) that extends from the pyloric sphincter to the jejunum. The duodenum is divided into four parts
four parts of the duodenum
first part is the superior. second is the descending, third is the horizontal and fourth is the ascending. the first part is the forgut, 2,3,4 midgut. minor and major papillae open into D2, this is also the last part of the forgut.
relations of the duodenum
the head of the pancreas sits in the Cshape of the duodenum, and the common bile duct opens into D2. It lies inferior to the superior part medial to the descending part and sup to the inf part.
Anterior relations of the duodenum
superior part: Quadrate lobe of liver and gallbladder
Descending part: fundus of gallbladder, right lobe of liver, transverse colon, coils of small intestine.
Horizontal part: root mesentery, coils of jejunum.
Ascending part: beginning of root of mesentery and coils of jejunum
posterior relations of the duodenum
Superior part: lesser sac, GDA, bile duct, portal vein, IVC
Descending part: hilus of right kidney
Horizontal part: right ureter, IVC, aorta
Ascending part: left margin aorta
Which part of the duodenum has part of the lesser omentum attached to its superior border and part of the greater omentum attached to its inferior border?
superior
Which part of the duodenum is supported by the suspensory muscle of the duodenum (ligament of Treitz)?
ascending
Which part of the duodenum has an intraperitoneal section?
ascending
blood supply to the duodenum
The first two parts of the duodenum are foregut structures and the third and fourth parts are midgut structures therefore the duodenum receives arterial blood from both the coeliac trunk and the superior mesenteric artery.
The parts of the duodenum proximal to the major duodenal papilla are supplied by a branch of the gastroduodenal artery which arises from the coeliac trunk. What is the name of this branch?
superior pancreatoduodenal artery
The parts of the duodenum distal to the major duodenal papilla are supplied by a branch of the superior mesenteric artery. What is the name given to this branch?
inferior pancreatoduodenal artery
jejunum and ileum
The jejunum extends from the duodenojejunal junction; it is approximately 2.5m long. The ileum extends from the distal end of the jejunum to the ileocaecal junction; it is approximately 3.6m long.
Most absorption occurs in the jejunum but the terminal ileum is the only site of absorption for which substance?
vitamin b12
blood supply to the jejunum and ileum
The jejunum and ileum are supplied by the superior mesenteric artery. The superior mesenteric artery enters the mesentery at the root of the mesentery and divides into about 15-18 branches. The arteries unite to form loops termed arcades. The arcades give rise to straight vessels, vasa recta, which project to the intestinal wall.
structural differences between the jejunum and ileum
Jejunum: in left upper quadrant of infracolic compartment. less fat in mesentery. redder. Fewer large arcades. More vascular.
Ileum: mostly in the right lower quadrant of infracolic compartment. Short vasa recta. narrower. paler. Mainly short and looped arcades. More fat in mesentery. Thinner walled.
Histologically the duodenum can be differentiated from other parts of the small intestine by the presence of
brunners glands