Gross Anatomy of Small Intestine & Large Intestine, (Rectum, Anal Canal)

Question 1

What are the three parts of the small intestine?

Answer 1

Duodenum, jejunum, and ileum.

Question 2

What are the four parts of the duodenum?

Answer 2

Superior, descending, inferior (horizontal), and ascending.

Question 3

What roles does the duodenum play in digestion?

Answer 3

Neutralizes stomach acid, emulsifies fats with bile, and receives pancreatic enzymes for chemical digestion.

Question 4

How do the jejunum and ileum increase surface area for absorption?

Answer 4

Through circular folds (plicae circulares), villi, and microvilli.

Question 5

Which artery supplies the small intestine?

Answer 5

Superior mesenteric artery.

Question 6

What are the main functions of the large intestine?

Answer 6

Absorbs water and salts, reduces indigestible residue to feces, and eliminates waste via defecation.

Question 7

What are the distinguishing features of the large intestine?

Answer 7

Taeniae coli, haustra, omental appendices, and wider diameter.

Question 8

Where is the appendix located, and what is its clinical significance?

Answer 8

Attached to the posteromedial side of the cecum; inflammation causes appendicitis (McBurney’s point tenderness).

Question 9

Name the sections of the colon in order.

Answer 9

Ascending, transverse, descending, and sigmoid colon.

Question 10

What are the key features of the rectum and anal canal?

Answer 10

Rectum has transverse folds; anal canal has internal/external sphincters and the pectinate line (divides embryonic origins).

Question 11

Which arteries supply the large intestine?

Answer 11

Proximal: Superior mesenteric artery. Distal: Inferior mesenteric artery

Question 12

How is the small intestine innervated?

Answer 12

Sympathetic (T8-T10), parasympathetic (vagus nerve).

Question 13

A patient has periumbilical pain. Which part of the intestine is likely involved?

Answer 13

Small intestine (e.g., duodenum or jejunum).

Question 14

What is the function of the mesentery?

Answer 14

: Suspends intestines, provides blood vessel/nerve passage, and prevents tangling.

Question 15

How is the rectum drained venously?

Answer 15

Superior rectal vein (to IMV), middle rectal vein (to internal iliac), and inferior rectal vein (to pudendal).

Question 16

What structure does the duodenum curve around?

Answer 16

The head of the pancreas.

Question 17

Which parts of the intestines are retroperitoneal?

Answer 17

Duodenum (except proximal 2 cm), ascending/descending colon, rectum.

Question 18

What structures pass through the mesentery?

Answer 18

Blood vessels, nerves, and lymphatic vessels.

Question 19

What is the function of taeniae coli?

Answer 19

Thickened longitudinal muscle bands that create haustra (pouches) for segmentation.

Question 20

What is the most common position of the appendix?

Answer 20

Retrocecal (behind the cecum).

Question 21

Where is McBurney’s point located, and what does tenderness here indicate?

Answer 21

1/3 distance from ASIS to umbilicus; sign of appendicitis.

Question 22

How does the epithelium change above/below the pectinate line?

Answer 22

Above: columnar (hindgut). Below: stratified squamous (ectoderm).

Question 22

What is the purpose of transverse rectal folds (valves)?

Answer 22

Support fecal weight and prevent involuntary defecation.

Question 23

Which parasympathetic nerves supply the distal colon?

Answer 23

Pelvic splanchnic nerves (S2–S4).

Question 24

What demarcates the transition between SMA and IMA supply?

Answer 24

Proximal 2/3 of transverse colon (SMA) → distal 1/3 (IMA).

Question 25

Where do lymphatics from the intestines drain?

Answer 25

Follow arteries → celiac/SMA/IMA nodes → cisterna chyli → thoracic duct.

Question 25

What is the "fat apron" attached to the stomach?

Answer 25

Greater omentum (from greater curvature).

Question 25

What structures does the lesser omentum connect?

Answer 25

Lesser curvature of stomach to the liver.

Question 26

Why does the colon have haustra?

Answer 26

Due to taeniae coli muscle tone; aids in slow fecal movement.

Question 27

Why does early appendicitis cause periumbilical pain?

Answer 27

Visceral pain referred from T10 (midgut embryologic origin).

Question 28

What type of muscle comprises each anal sphincter?

Answer 28

Internal: smooth muscle (involuntary). External: skeletal muscle (voluntary).

Question 29

Why is rectal venous drainage clinically significant?

Answer 29

Portosystemic anastomosis (e.g., hemorrhoids in portal hypertension).

Question 30

Which ganglia supply sympathetic fibers to the intestines?

Answer 30

Celiac, superior mesenteric, and inferior mesenteric ganglia.

Question 31

How does vagal innervation reach the hindgut?

Answer 31

It doesn’t; pelvic splanchnic nerves (S2–S4) take over.

Question 32

What divides the midgut and hindgut?

Answer 32

: Distal 1/3 of transverse colon (near splenic flexure).

Question 33

A patient has crampy periumbilical pain and alternating diarrhea/constipation. What are 3 possible causes?

Answer 33

Irritable bowel syndrome (IBS), Crohn’s disease, small intestinal bacterial overgrowth (SIBO).

Question 34

Why is the sigmoid colon prone to volvulus?

Answer 34

Mobile mesentery and fixed points at rectosigmoid junction.

Question 35

Which artery blockage would affect the splenic flexure?

Answer 35

"Watershed area" between SMA and IMA (vulnerable to ischemia).

Question 36

Why do anal fissures typically occur posteriorly?

Answer 36

Poor blood supply in the posterior midline.

Question 37

What embryologic defect causes Hirschsprung’s?

Answer 37

Absence of ganglion cells (parasympathetic innervation) in distal colon.