Human Anatomy Intestines + Spleen Quiz

What is the main function of the small intestine?

It is the main site of digestion and nutrient absorption.

What are the three parts of the small intestine in order?

Duodenum → jejunum → ileum.

Which part of the small intestine is the shortest?

Duodenum.

Approximately how long is the duodenum?

About 10 inches.

What proportion of the small intestine is assigned to the jejunum in the slides?

About 40%.

Approximately how long is the jejunum?

About 8 feet.

What proportion of the small intestine is assigned to the ileum in the slides?

About 60%.

Approximately how long is the ileum according to the slides?

About 10–12 feet

Which small-intestinal region is the last before the large intestine?

Ileum.

How does the diameter of the small intestine compare with the large intestine?

Small intestine ≈1 inch across; large intestine ≈2.5 inches across.

List the main small-intestinal wall layers from outside to inside.

Serosa → muscularis externa → submucosa → muscularis mucosae → mucosa (as presented on the slide).

What makes up the small intestine’s serosa?

Connective tissue and visceral peritoneum.

What is the muscularis externa of the small intestine?

Two layers of smooth muscle: longitudinal and circular.

What are the two smooth muscle layers of the small-intestinal muscularis externa?

Outer longitudinal and inner circular smooth muscle.

What does the small intestine’s submucosa contain?

Blood vessels and lymphatics.

What is the muscularis mucosae of the small intestine?

A thin smooth-muscle layer separating submucosa from mucosa.

What does the small-intestinal lamina propria contain?

Connective tissue with collagen and elastic fibers, blood vessels, lymphatics, and nerves.

What covers the small-intestinal mucosal surface?

Epithelial cells bearing microvilli.

What are microvilli in the small intestine?

Tiny cytoplasmic extensions of epithelial cells that increase the surface area for absorption.

What structural protein drives microvillus formation in the lecture explanation?

Actin pushing/organizing the cell membrane into extensions.

What type of epithelium is shown lining the small intestine in the figure?

Simple columnar epithelium, with microvilli along the luminal surface.

What is a lacteal within an intestinal villus?

A lymphatic capillary in the villus core, shown in the small-intestinal lining diagram.

What other vessels are shown in the core of an intestinal villus?

Blood capillaries alongside a central lymphatic/lacteal.

Which wall layer is labeled immediately superficial to the muscularis externa?

Submucosa.

Why is the small intestinal wall highly folded?

To increase surface area for absorption.

By approximately how much do the small-intestinal surface adaptations increase area, according to the slide?

By more than 600-fold.

What tissue folds to produce intestinal villi, as described in the slides?

The lamina propria.

What are intestinal villi?

Fingerlike folds/projections of intestinal mucosa that expand the absorptive area.

What lines the surfaces of intestinal villi?

Epithelial cells with microvilli.

What tissue layer folds to form plicae circulares, according to the lecture?

The submucosa (with overlying mucosa).

What is another name for plicae circulares?

Circular folds.

What is the purpose of plicae circulares?

Increase the surface area available for absorption.

Which is larger: plica circularis, villus, or microvillus?

Plica circularis (large fold) → villus (mucosal projection) → microvillus (cell-surface extension).

How do circular folds differ from villi?

Circular folds include submucosa with mucosa; villi are mucosal projections containing lamina propria.

What structure labeled as a circular fold is visible at the larger scale in the small intestine figure?

Plica circularis.

What structures project from the circular-fold surface in the diagram?

Intestinal villi.

What is segmentation in the small intestine?

Rhythmic local contractions of the circular smooth muscle surrounding the intestine.

Which smooth-muscle layer produces segmentation?

Circular smooth muscle.

How does chyme move during segmentation?

In both directions, back and forth.

How does segmentation improve absorption?

It exposes chyme to more of the intestinal lining, including the circular-fold surfaces.

What physical change increases segmentation?

Distension (stretching) of the small intestine.

What chemical/hormonal factor is listed as stimulating segmentation?

Gastrin from the stomach, as described in the slides.

Where does segmentation occur more frequently?

Duodenum and jejunum.

In which part does segmentation become less frequent?

Ileum.

Why does segmentation decrease in the ileum, according to the slides?

The ileum has thinner walls and less circular smooth muscle.

Overall, how does segmentation influence transit toward the large intestine?

It mixes chyme and moves it slowly toward the large intestine.

Which part of the small intestine is widest?

Duodenum.

Where does the duodenum begin?

At the pyloric sphincter of the stomach.

In which abdominal quadrant does the duodenum begin?

Right upper quadrant (RUQ).

What is the shape of the duodenum?

C-shaped.

Which nearby organ does the duodenum curve around?

The head of the pancreas.

Where does the duodenum end?

At the duodenojejunal flexure (junction with the jejunum).

How sharply does the small intestine turn at the duodenojejunal flexure?

Almost 90 degrees, per the slide.

How many parts does the duodenum have?

Four.

Name the four duodenal parts in order.

Superior → descending → inferior/horizontal → ascending.

What is another name for the inferior duodenal part?

Horizontal part.

Which duodenal part follows the superior part?

Descending part.

Which duodenal part follows the descending part?

Inferior (horizontal) part.

Which duodenal part precedes the duodenojejunal flexure?

Ascending part.

Why is the duodenum especially important for fat digestion?

The bile duct and pancreatic duct open into it.

What two ducts open into the duodenum?

Bile duct and pancreatic duct.

What glands characterize the duodenum in the slide comparison?

Submucosal glands.

What do duodenal submucosal glands secrete?

Alkaline mucus.

Why does the duodenum secrete alkaline mucus?

To protect its cells from stomach acid.

Which duodenal part lies immediately after the pylorus?

Superior part.

What is the point where duodenum joins jejunum labeled in the figure?

Duodenojejunal junction/flexure.

Where does most intestinal absorption occur?

In the jejunum.

Why does the jejunum look reddish?

It has a rich blood supply.

In which abdominal quadrant is most jejunum located?

Left upper quadrant (LUQ).

How is jejunal vascularity compared with ileal vascularity?

Jejunum is more richly vascularized.

Which small-intestinal segment has the most plicae circulares?

Jejunum.

How do jejunal circular folds compare with ileal folds?

Jejunum has more plicae circulares; ileum has fewer.

Which segment is the thinnest part of the small intestine?

Ileum.

In which abdominal quadrants is the ileum located?

Both left lower quadrant (LLQ) and right lower quadrant (RLQ).

What color does the ileum appear relative to the jejunum?

More pinkish, because it is less vascular.

Why does the ileum appear less red than the jejunum?

It is less vascular.

What lymphoid structures are characteristic of the ileum?

Peyer’s patches.

Where are Peyer’s patches located?

In the submucosa of the ileum, as specified by the lecture.

What are Peyer’s patches made up of?

Collections of lymphocytes (white blood cells).

What is the main protective role of Peyer’s patches?

Defend the small intestine against bacteria from the large intestine.

What additional function of Peyer’s patches is mentioned?

Prevent the growth of pathogenic bacteria in the intestine.

Which region has fewer plicae circulares and prominent Peyer’s patches?

Ileum.

What attaches the jejunum and ileum to the posterior abdominal wall?

Mesentery of the small intestine.

Where is the mesentery of the small intestine attached?

To the posterior abdominal wall; it supports the jejunum and ileum.

Which region has the densest circular folds in the small-intestine gross-anatomy comparison?

Jejunum.

What junction connects the small and large intestines?

The ileocecal valve, connecting terminal ileum and cecum.

Where does the ileocecal valve project?

Into the cecum.

When does the ileocecal valve open?

When intestinal contents are pushed forward.

What tissue forms the ileocecal valve?

Thickened wall of the terminal ileum.

What is the ileal orifice?

The opening of the terminal ileum at the ileocecal junction.

What is the normal contraction state of the ileal orifice, according to the lecture?

It is constantly contracted.

What does the contracted ileal orifice form?

The ileal papilla.

Why does the ileocecal region help protect the small intestine?

It prevents bacteria from the colon entering the nutrient-rich small intestine.

What is the protruding structure at the ileal opening called?

Ileal papilla.

What structure opens into the cecum below the ileal opening?

Appendix (opening/orifice of appendix).

What is the primary function of the large intestine emphasized in these slides?

Reabsorb water from chyme to form semisolid stool/feces.

What is produced as the large intestine removes water from chyme?

Semisolid stool (feces).

What happens to feces before defecation?

They are stored until defecation.

What is the approximate diameter of the large intestine?

About 2.5 inches.

What is the approximate diameter of the small intestine for comparison?

About 1 inch.