Small Intestine (21-22)

Question 1

The small intestine extends from the

Answer 1

Pylorus of the stomach to the ileocecal junction

Question 2

Its inner surface is covered with

Answer 2

Mucosal folds called Plicae Circulares

Question 3

There are 3 parts of the small intestine

Answer 3

Duodenum, Jejunum, and Ileum

Question 4

Duodenum (12 inches)

Answer 4

C-shaped and cradles the head of the pancreas

Question 5

The Duodenum has 4 parts

Answer 5

Superior, descending, horizontal and ascending

Question 6

The common bile duct and main pancreatic duct

Answer 6

empty together into the left side of the descending (2nd) part of the duodenum at the major duodenal papilla

Question 7

Duodenum is

Answer 7

Retroperitoneal

Question 8

Jejunum is continuous with

Answer 8

duodenum proximally and the ileum distally

Question 9

Jejunum has no clear demarcation from ileum;

Answer 9

it is the proximal 2/5 of combined length of jejunum and ileum

Question 10

Ileum is continuous with

Answer 10

Jejunum proximally; cecum distally

Question 11

Ileum is the distal

Answer 11

3/5 of combined length of jejunum and ileum

Question 12

Jejunum and ileum are

Answer 12

Intraperitoneal organs attach to the posterior abdominal wall by the mesentery

Question 13

The function of the small intestine is

Answer 13

secretion of enzymes and hormones and nutrient absorption

Question 14

Lining of the small intestine forms visible to the naked eye folds called

Answer 14

Plicae circulares (circular folds). They are formed by mucosa and submucosa

Abundant in jejunum and disappear in distal ileum

Their purpose is to increase the surface area of the small intestine

Question 15

Epithelium and lamina propria form

Answer 15

Finger-like projections into the lumen called villi

Question 16

Between the villi, the epithelium deepens into lamina propria and forms tubular glands called

Answer 16

Intestinal glands (crypts) or Crypts of Lieberkuhn

They extend from the muscular mucosal cells of the epithelial lining

Question 17

Enterocytes

Answer 17

Tall absorptive cells forming simple columnar epithelium. The apex of each cell is covered with microvilli –> increase surface area of epithelium

Together, microvilli form the brush (striated) border

The Enterocytes absorb nutrients from the lumen of the small intestine

Sugars and proteins pass into the blood capillaries while the lipids pass into the central lacteal into the core of the villus

Question 18

Goblet Cells

Answer 18

Scattered between enterocytes, increasing in the number as the more distal small intestine is approached

These cells have a basally located nucleus and greatly expanded apical portion containing larger numbers of secretory granules

The granules contain acid glycoprotein which are secreted onto the luminal surface and lubricate and protect the lining of of the intestine

Goblet cells are joined to the intestinal absorptive cells by tight junctions

Question 19

Lamina Propria

Answer 19

Loose connective tissue with blood and lymph vessels and nerve fibers

They make the core of each intestinal villus

Question 20

Muscular Mucosae

Answer 20

Inner circular and outer longitudinal smooth muscle.

Smooth muscles extend into the villi facilitating their rhythmic movements

Question 21

Submucosa

Answer 21

Connective tissue rich in collage and elastic fibers. Meissner’s plexus is present

In the duodenum, the submucosa contains Bruner’s glands

in the Ileum, Peyer’s patches extend into the submucosa

Question 22

Muscular externa

Answer 22

Inner circular and outer longitudinal layers of smooth muscles. Auerbach’s myenteric plexus lies between the two layers

Question 23

Outer Layer - which could be either:

Answer 23

Adventita- outer layer of the major part of duodenum (retrop organ)

Serosa- outer layer of jejunum and ileum, they are invested by the mesentery proper and are (intrp organs) therefore the outer layer is a serosa

Jejunum + Ileum = Mesenteric intestine