the intestines Flashcards
What are the three parts of the small intestine?
Duodenum
Jejunum
Ileum
Where does the small intestine extend from and to?
It extends from the pylorus of the stomach to the ileocaecal junction (where the ileum joins the caecum).
What are the 8 main parts of the large intestine?
Caecum
Appendix
Ascending colon
Transverse colon
Descending colon
Sigmoid colon
Rectum
Anal canal
What is the shape and position of the duodenum?
The duodenum forms a C-shaped loop in the right upper quadrant, extending between L1 and L3 levels. (Use the first diagram from the slide here.)
How are the jejunum and ileum arranged?
The jejunum and ileum coil into a loop and span across all quadrants of the abdomen
How does the large intestine relate to the small intestine?
The large intestine forms a frame around the small intestine, enclosing it within its loop.
What is the duodenum, and what is its function?
The first part of the small intestine, responsible for nutrient absorption. It has a C-shaped loop that curves around the head of the pancreas.
Where does the duodenum begin and end?
Starts at the pylorus of the stomach.
Ends at the duodenojejunal flexure (L2 level, left of midline).
Is the duodenum retroperitoneal?
Yes, except for the first part, which is covered by the hepatoduodenal ligament.
What are the four parts of the duodenum, and their vertebral levels?
How is the mucosa of the duodenum similar to the stomach?
It has circular folds, which increase surface area for digestion and absorption.
What is the major duodenal papilla, and what is its function?
The site where bile and pancreatic juice enter the duodenum, aiding in digestion.
What anatomical landmark marks the transition from the foregut to the midgut?
The major duodenal papilla is the boundary between the foregut and midgut.
What are the two duodenal papillae, and what do they do?
Major duodenal papilla – Receives bile and pancreatic enzymes via the common bile duct and major pancreatic duct.
Minor duodenal papilla – Receives secretions from the accessory pancreatic duct.
Which arteries supply the duodenum?
Superior pancreaticoduodenal artery (SPDA) – from gastroduodenal artery (coeliac trunk).
Inferior pancreaticoduodenal artery (IPDA) – from superior mesenteric artery (SMA).
How is the duodenum’s blood supply divided between the foregut and midgut?
Proximal to major duodenal papilla → SPDA (Coeliac trunk, foregut).
Distal to major duodenal papilla → IPDA (SMA, midgut).
Where does venous drainage of the duodenum occur?
Drains into hepatic portal vein, superior mesenteric vein, or splenic vein.
How much of the small intestine is made up by the jejunum and ileum?
Jejunum: 2/5 of the small intestine length.
Ileum: 3/5 of the small intestine length.
How do the vasa recta (straight arteries) differ in the jejunum and ileum?
Jejunum: Long vasa recta.
Ileum: Short vasa recta.
How do the arterial arcades differ between the jejunum and ileum?
Jejunum: Few large loops.
Ileum: Many short loops.
Where is there more fat in the mesentery – jejunum or ileum?
Jejunum: Less fat.
Ileum: More fat.
How do circular folds differ between the jejunum and ileum?
Jejunum: Prominent and tightly packed.
Ileum: Sparse, almost absent in the distal part.
Which part of the small intestine has more lymphoid tissue?
Jejunum: Few lymphoid tissues.
Ileum: Many lymphoid follicles.
What is the mesentery, and what does it do?
A fan-shaped fold of peritoneum that attaches the jejunum and ileum to the posterior abdominal wall.
What 2 structures are found between the layers of the mesentery?
Superior mesenteric vessels (SMA and its branches).
Autonomic nerves.
Which arteries supply the jejunum and ileum?
Jejunal and ileal branches of the superior mesenteric artery (SMA).
Where does the superior mesenteric artery (SMA) arise?
From the abdominal aorta at L1.
1 cm inferior to the coeliac trunk.
What is the primary function of the large intestine?
The large intestine absorbs water from indigestible residues, forming semi-solid stool or feces.
What are omental (epiploic) appendages?
Small, fatty projections of the peritoneum found on the large intestine.
What are teniae coli, and what is their function?
Three longitudinal bands of smooth muscle that help in the peristaltic movement of the colon.
What are haustra, and what do they do?
Sacculations of the large intestine wall that allow for segmentation and movement of stool.
What is the caecum, and where is it located?
The caecum is the first part of the large intestine, a blind-ended pouch that is continuous with the ascending colon. It is located inferior to the ileocaecal junction.
What is the appendix, and where does it arise from?
The appendix is a blind intestinal diverticulum containing lymphoid tissue. It arises from the posteromedial aspect of the caecum.
Are the caecum and appendix intraperitoneal or retroperitoneal?
Both the caecum and appendix are intraperitoneal organs.
Which artery supplies the caecum?
The ileocolic artery, a branch of the superior mesenteric artery (SMA).
Which artery supplies the appendix?
The appendicular artery, a branch of the ileocolic artery.
Where does the ascending colon extend from and to?
It extends from the caecum to the right colic flexure and is retroperitoneal.
Where does the transverse colon extend from and to?
It extends from the right to the left colic flexure and is intraperitonea
Where does the descending colon extend from and to?
It extends from the left colic flexure to the sigmoid colon and is retroperitoneal.
Where does the sigmoid colon extend from and to?
It forms an S-shaped loop linking the descending colon to the rectum and is intraperitoneal.
How is the colon divided based on embryonic origin?
Midgut-derived: 2/3 of the transverse colon and parts before it.
Hindgut-derived: 1/3 of the transverse colon and parts after it.
What are the two main arteries supplying the colon?
Superior mesenteric artery (SMA): supplies the midgut portion of the colon.
Inferior mesenteric artery (IMA): supplies the hindgut portion of the colon.
What is the marginal artery, and what does it supply?
It is formed by branches of the colic arteries and sigmoid arteries, running along the length of the colon.
Where do the midgut and hindgut portions of the colon drain?
Midgut portion drains into the superior mesenteric vein.
Hindgut portion drains into the inferior mesenteric vein
At what vertebral level does the inferior mesenteric artery (IMA) arise?
L3 vertebral level.
What is the most common anatomical position of the appendix?
Retrocaecal (64% of cases)
Where is McBurney’s point located?
One-third of the way along the oblique line between the right anterior superior iliac spine (ASIS) and the umbilicus.
Why does appendicitis initially cause vague pain around the umbilicus?
Stretching of the visceral peritoneum triggers pain referred to the T10 dermatome (periumbilical region).
Why does appendicitis later cause severe pain in the lower right quadrant?
Inflammation irritates the parietal peritoneum, localizing pain to the right lower quadrant.
