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Small Intestine Histology & Functional Specializations - Coggle Diagram
Small Intestine Histology & Functional Specializations
The Mucosa: Villi & Lamina Propria Core (4 Epithelial & Villus Core Cells)
Villous Epithelium (4 Cell Types)
M Cells (Microfold / Antigen delivery)
Specialized antigen-presenting cells sitting over lymphoid follicles; deliver captured luminal antigens directly to underlying immunocompetent lymphocytes and macrophages via deep basolateral plasma membrane invaginations
Goblet Cells (Mucus-secreting)
Unicellular mucous glands flaring upward like a goblet; apical two-thirds stored with mucin granules, displacing the triangular nucleus basally
Enterocytes (Striated brush border)
Columnar cells (~25 µm tall) with an apical striated (brush) border formed by ~3,000 dense microvilli (1–2 µm long) :
Basal third
Contains the nucleus and metabolic organelles
Function
Specialized in active nutrient absorption
Endocrine Cells (APUD system)
Diffuse neuroendocrine cells capable of
A
mine
P
recursor
U
ptake and
D
ecarboxylation (yielding serotonin, histamine, dopamine, and norepinephrine)
Lamina Propria (Core)
Central Lacteal (Lymphatic core)
Muscle of Brücke (Longitudinal smooth muscle from muscularis mucosae for villous motility)
Neurovascular Triad (Arterioles, Capillaries, Venules)
Glands Of LIEBERKÜHN (Intestinal Crypts) & Galt
Crypt Cell Dynamics & Secretions
APUD / Endocrine Secretions
Secretin
Stimulates pancreatic HCO₃⁻ secretion and inhibits gastric HCl
Gastric Inhibitory Peptide (GIP)
Inhibits gastric HCl while stimulating glucose-dependent insulin release
Cholecystokinin (CCK)
Stimulates gallbladder contraction and pancreatic enzyme release
Paneth Cells
Reside strictly at the base of the crypts. Serous, basophilic cells packed with large eosinophilic apical granules containing lysozyme, peptidases, and antimicrobial peptides to control intestinal microflora
Undifferentiated (Stem) Cells
Situated at the crypt-villus junction; act as the progenitor pool for continuous epithelial turnover every 4–5 days
Gut-Associated Lymphoid Tissue (GALT) & Peyer's Patches
GALT
Lymphoid infiltrates scattered throughout the lamina propria, particularly surrounding the bases of the crypts
Peyer's Patches
Prominent lymphoid aggregates restricted to the distal half of the ileum
Form massive, dome-like lymphoid nodules that bulge into the intestinal lumen, causing overlying villi and crypts to become sparse or absent
Submusosa, Muscularis Externa & Regional Variations
Muscularis Mucosae & Muscle of Brücke
Fine muscle bundles ascend into the core of each villus to form the Muscle of Brücke, producing rhythmic villous pumping movements that drive lymph through the central lacteal.
Consists of an inner circular and outer longitudinal smooth muscle layer
Muscularis Externa & Serosa / Adventitia
Muscularis Externa
Inner circular layer (thick) + Outer longitudinal layer, sandwiching Auerbach's Myenteric Plexus for intrinsic peristaltic motor control
Outer Layer
Covered by Serosa (visceral peritoneum) throughout the mobile jejuno-ileum, but replaced by Adventitia along retroperitoneal segments of the duodenum