The digestive tract's immune system is often referred to as gut-associated lymphoid tissue (GALT) and works to protect the body from invasion. GALT is an example of mucosa-associated lymphoid tissue.

Contents 1 Function 2 Components 3 Additional images 4 References 5 External links

[edit] Function

About 70% of the body's immune system is found in the digestive tract. The GALT is made up of several types of lymphoid tissue that store immune cells, such as T and B lymphocytes, that carry out attacks and defend against pathogens.

New research indicates that GALT may continue to be a major site of HIV activity, even if drug treatment has reduced HIV count in the peripheral blood.^[1][2]

[edit] Components

Lymphoid tissue in the gut comprises the following:

• Tonsils (Waldeyer's ring)
• Adenoids (Pharyngeal tonsils)
• Peyer's patches
• Lymphoid aggregates in the appendix and large intestine
• Lymphoid tissue accumulating with age in the stomach
• Small lymphoid aggregates in the oesophagus
• Diffusely distributed lymphoid cells and plasma cells in the lamina propria of the gut

[edit] Additional images

Lymphatics of colon.

Section of the human esophagus.

Transverse section of human vermiform process. X 20.

Section of mucous membrane of human rectum. X 60.

[edit] References

[edit] External links

• Histology at BU 12502loa - "Digestive System: Alimentary Canal: colon, taenia coli"
• Histology at BU 11102loa - "Digestive System: Alimentary Canal: esophageal/stomach junction"

v • d • e Anatomy of torso, digestive system: Gastrointestinal tract, excluding mouth (TA A05.3-7, GA 11.1141) Upper GI Hypo- pharynx Piriform sinus spaces: Peripharyngeal space (Retropharyngeal space, Parapharyngeal space) · Retrovisceral space (Retropharyngeal space, Danger space) · Prevertebral space Pterygomandibular raphe · Pharyngeal raphe · Buccopharyngeal fascia · Pharyngobasilar fascia Pharyngeal muscles Esophagus UES, LES Stomach Gastric rugae · gastric pits · cardia/gland · fundus/gland · pylorus/gland · pyloric antrum · pyloric canal · greater curvature · lesser curvature · angular incisure Lower GI Intestine: small Duodenum (Suspensory muscle, Major duodenal papilla, Minor duodenal papilla, Duodenal cap) • Duodenojejunal flexure • Jejunum • Ileum (Terminal ileum) • Ileocecal valve continuous (intestinal villus, crypts of Lieberkühn, circular folds) Intestine: large Vermiform appendix • Cecum • Colon (ascending colon, hepatic flexure, transverse colon, splenic flexure, descending colon, sigmoid colon) continuous (taenia coli, haustra, epiploic appendix) Termination Rectum: Houston valve • rectal ampulla • pectinate line Anal canal: anal valves • anal sinuses • anal columns • Hilton's white line Anus: Sphincter ani internus muscle • Sphincter ani externus muscle Lymph GALT: Peyer's patches (M cells) digestive system navs: anat of tract,glands,perit,diaphragm/physio/dev, noncongen/congen/congen of d+w/neoplasia, symptoms+signs/eponymous, proc

v • d • e Immune system: Lymphatic system (Lymph, Lymphocytes, Lymph vessels) (TA A13.1-2, GA 8) Primary Bone marrow · Thymus (Hassall's corpuscles) Secondary Spleen (process blood) structural: Hilum · Trabeculae Red pulp (Cords of Billroth, Marginal zone) White pulp (Periarteriolar lymphoid sheaths, Germinal center) blood flow: Trabecular arteries · Trabecular veins Lymph nodes (process extracellular fluid) lymph flow: Afferent lymph vessels · Cortical sinuses · Medullary sinuses · Efferent lymph vessels T cells: High endothelial venules B cells: Primary follicle/Germinal center · Mantle zone · Marginal zone layers: Capsule/Trabeculae · Subcapsular sinus · Cortex · Paracortex · Medulla (Medullary cord) · Hilum MALT (process mucosa) GALT · Peyer's patches · Germinal center lymphatic organ navs: anat, physio, lymphatic disease/splenic disease/thymus disorders/thymus neoplasia/vascular tumors, proc