Histology of Small Intestine

Structures within Wall of Duodenum

• Unlike the stomach, what is present in both lamina propria and submucosa

• What is villi

  • What forms villi

  • Shape of villi

  • Function

  • Between 2 villis are

• What is plicae circulares

  • Contains

  • Function

• How does the absorbed nutrients move into circulation

• Brunner’s gland in submucosa secrete what in

  • Pig and horse

  • Ruminant and dog

  • Cat

• Function of chyme

Unlike the stomach, what is present in both lamina propria and submucosa: Glands

What is villi: Finger-like projections

• What forms villi: Epithelium and lamina propria

• Shape of villi: Leaf shape

• Function: Increase surface area to increase absorption

• Between 2 villi are:

  • Crypts of Leiberkuhn in lamina propria (intestinal glands)

  • Brunner’s gland in submucosa

What is plicae circulares: Numerous folds of mucous membrane

• Contains: Tiny projections of villi and microvilli

• Function: Further increase SA for absorption

How does the absorbed nutrients move into circulation: By blood capillaries, lacteals or lymphs

Brunner’s gland in submucosa secrete what in:

• Pig and horse: Serous secretions

• Ruminant and dog: Mucous secretions

• Cat: Seromucous secretions

Function of chyme: Induces Brunner’s gland to secrete alkaline mucus to neutralize gastric acid and pepsin

Histology of Duodenum: Mucosa

• Epithelium

  • What does it have for absorption

  • What does it have for protection

  • Why are epithelial cells in base of crypt in constant mitosis

• Lamina propria

  • Loose CT contains

  • Base of glands of Lieberkuhn are

  • Arrangement of lymphocytes

  • Pyramid shaped cells produce

• Muscularis mucosa

  • Layer of

  • Why is muscle layer not continuous

    • As glands of Lieberkuhn continue into submucosa, it turns to

Epithelium:

• Absorption: Tall columnar with microvilli

• Protection: Goblet cells

• Epithelial cells in constant mitosis: To replace desequamated cells at tip of villi

Lamina propria:

• Loose CT contains:

  • Glands of Lieberkuhn

  • Lacteals

• Base of glands of Lieberkuhn: Have Panneth cells

• Arrangement of lymphocytes: Single or aggregations

• Pyramid shaped cells produce: Peptidase and lysoenzyme (antibacterial compound)

Muscularis mucosa:

• Layer of: Smooth, circularly arranged muscle cells

• Muscle layer not continuous: Because it’s interrupted by glands of Lieberkuhn

  • As glands of Lieberkuhn continue into submucosa, it turns to: Brunner’s gland

Histology of Duodenum: Submucosa

• Loose CT contains

• Alveolar mucous glands

  • Describe nucleus

  • Smallest in

  • Largest in

Loose CT contains:

• Brunner’s gland (protection)

• Alveolar mucous gland

• Lymph nodes (non-capsulated lymph node)

Alveolar mucous glands:

• Describe nucleus: Flat, basal nucleus

• Smallest in: Pig

• Largest in: Goats

Histology of Duodenum: Muscularis Externa #ffb300

• Layers

• In between layers are

Layers: Of smooth muscle cells

• Inner circular

• Outer longitudinal

In between layers are: Myentric plexus

Histology of Duodenum: Serosa #a700ff

• Loose CT bounded by

• What empties into the duodenum

Loose CT bounded by: Simple squamous epithelium

What empties into duodenum:

• Secretions by

  • Gland of Lieberkuhn

  • Brunner’s gland

• Secretion of bile from liver and pancreatic juice

Regional Variation in Small Intestine

• Duodenum

  • Glands?

  • Structures present

  • Characteristic of villi

  • Characteristic of goblet cells

• Jejunum

  • Glands?

  • Lymphoid nodules?

  • Villi?

• Ileum

  • Glands?

  • Structures present

  • Characteristic of villi

Duodenum:

• Glands: Present, Brunner’s glands

• Structures present:

  • Plicae circulares

  • Leaf like villi

  • Lacteal

  • Chyme

• Characteristic of villi: Longest

• Characteristic of goblet cells: Highest number

Jejunum:

• Glands: No

• Lymphoid nodules: Present but not as prominent as Peyer’s patches in ileum

• Villi: Finger-like

Ileum:

• Glands: No glands

• Structures present:

  • Peyer’s patches

  • Goblet cells

• Characteristic of villi: Shorter

Jejunum

• Shape of villi

• Glands?

• Name the 6 structures in the image

Shape of villi: Finger-like

Glands: Absent

Structures:

1. Tunica mucosa

2. Tunica submucosa

3. Tunica muscularis

4. Tunica serosa

5. Villi

6. Glands (crypts) iin the lamina propria of mucosa

Ileum

• What structure is present in submucosa

• Length of villi

• Number of goblet cells

• Name the structures 1-8

Structure in submucosa: Permanent aggregated lymphoid nodules

Length of villi: Shortest

Number of goblet cells: More

Structures:

1. Tunica mucosa

2. Tunica submucosa

3. Tunica muscularis

4. Tunica serosa

5. Villi

6. Epithelium of mucosa (covers villi)

7. CT of the lamina propria

8. Glands (crypts) in the lamina propria of mucosa