= Solution
\b[A lymphatic gland is a <lymph node>; a Lieberkühnian gland is an <intestinal crypt>; a <Brunner gland> is a predominantly mucous duodenal gland.] The first is a lymphoid organ with traversing lymphatic channels; the other two are epithelial glands opening towards the intestinal lumen. Similar historical terminology must not erase that difference.
A <lymph node> has a fibrous <connective tissue> capsule sending trabeculae into the organ and an internal reticular framework supporting mobile <cells>. Its outer cortex contains lymphoid follicles, whose appearance changes with immune activity; activated secondary follicles have paler <germinal centres> surrounded by more densely packed <lymphocytes>. The deeper cortex or <paracortex> lies between follicular cortex and medulla. The medulla contains branching cellular cords separated by medullary sinuses. A <hilum> provides the entry and exit of the main <blood vessels> and the exit of efferent lymphatics.
Afferent <lymphatic vessels> enter at the convex surface and deliver <lymph> to the subcapsular sinus. Flow then passes through cortical or trabecular channels into medullary sinuses and out through efferent vessels near the <hilum>. <Macrophages> and the reticular arrangement bring carried material into contact with the cellular apparatus. The node's <blood circulation> is distinct from that lymphatic route. In modern terms, follicles are predominantly <B cell> territories, the <paracortex> is rich in <T cells>, and medullary cords contain many antibody-producing <plasma cells>. Those cellular classifications go beyond an ordinary 1865 microscopic description.<Histology, Lymph Nodes (StatPearls)>[Structure; Function; Histochemistry and Cytochemistry: cortex, paracortex and medulla]{ref}
Thin stained sections show the overall architecture, while a silver stain highlights the supporting reticular fibres rather than every <lymphocyte>. The fibres include <type III collagen>; the thicker capsule has a different connective-tissue organization. One must not interpret the meshwork itself as an epithelial secretory tube, or assume a section missing the <hilum> proves that the node has no efferent vessel.<Lymphatic Tissues: Lymph Nodes by Columbia University>[Slides 22 and 31: silver-stained reticulum, sinuses, capsule, hilum and postcapillary venules]{ref}
The <intestinal crypts> are simple tubular epithelial invaginations opening between the <intestinal villi> in the <small intestine>. Their bases approach the <muscularis mucosae>, remaining within the mucosa and surrounded by <lamina propria>. Each gland has a lumen continuous with the intestinal surface and a lining supported by a <basement membrane>. It contains columnar epithelial <cells> at different stages of differentiation, <goblet cells> producing mucus, endocrine <cells> and, in small-<intestinal crypt> bases, conspicuous granular <Paneth cells>. A proliferative compartment supplies replacement <cells> that move towards the surface; this modern <cell>-renewal account explains why dividing <cells> are common in the crypts. Crypts also occur in the <colon>, whose mucosa lacks ordinary small-intestinal villi. One should therefore specify the region rather than make villi part of every crypt's definition.
A <Brunner gland> lies chiefly in the submucosa of the proximal <duodenum>, below the <muscularis mucosae>. It is a branched, compound tubular gland with pale mucus-rich secretory <cells>, basal nuclei and small lumina. Its ducts pass through the <muscularis mucosae> and commonly join overlying <intestinal crypts> before opening into the lumen. Its alkaline, mucus-rich secretion helps protect the mucosa from acidic gastric contents. The position below the <muscularis mucosae> distinguishes it particularly well from a <Lieberkühn gland> in the mucosa.<GI Tract Notes by Duke University>[Small Intestine; regional differences: crypts, cell types and submucosal Brunner glands with ducts joining crypts]{ref}
The most useful comparison is consequently one of compartments: a reticular lymphoid organ containing sinuses, a mucosal epithelial tube, and a branched submucosal secretory system. Recognition of the capsule, epithelial lining, <muscularis mucosae> and duct connections establishes those distinctions more securely than a name alone.
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