ileum
Enable an agent to identify an ileum, describe its anatomical and functional state, and determine what observations or assessments are justified by the available evidence.
Research draft, second pass
A second pass drafted this model: the structure a model of this thing needs, and what is known about it in the world. The line under this one says how the second half was obtained - researched against sources, or recalled without web access, in which case nothing here was read anywhere and every claim is a lead to verify. Unreviewed either way.
recalled by Codex without web access - no source was read
Researched by: Codex
Purpose and description
Enable an agent to identify an ileum, describe its anatomical and functional state, and determine what observations or assessments are justified by the available evidence.
The ileum is the distal portion of the small intestine, continuous proximally with the jejunum and, in humans, opening distally into the cecum at the ileocecal junction, where it contributes to nutrient absorption and intestinal immune function.
It can be Locate and annotate an ileal segment using anatomical continuity and supporting tissue features.; Map imaging findings, endoscopic observations and biopsies to specific ileal regions.; Compare local structure and function across time while preserving measurement conditions.; Record ileal resection, diversion and reconnection together with remaining anatomical continuity.; Flag evidence gaps that prevent conclusions about absorption, patency or viability.; Link observed abnormalities to separate diagnostic and procedure models for qualified review..
Distinguishing features
In human anatomy, the ileum follows the jejunum and terminates at the ileocaecal junction; a sharp external jejunum-ileum boundary is generally absent.
Compared with jejunum, distal ileum generally has less prominent circular folds and more conspicuous aggregated lymphoid tissue; these are supporting features rather than individually decisive tests.
Preserved ileal mucosa has small-intestinal villi, distinguishing it from normal adjacent colonic mucosa.
The terminal ileum has specialised roles in bile acid reclamation and intrinsic-factor-bound vitamin B12 absorption, although these functions cannot establish specimen identity by themselves.
The ileum is intestinal soft tissue with a lumen and layered wall; the similarly named ilium is part of the bony pelvis.
Scope
+ The ileal segment and its continuity with neighbouring intestinal regions
+ Ileal wall, mucosal surface, lymphoid tissue and mesenteric attachments
+ Absorption of bile acids and intrinsic-factor-bound vitamin B12
+ Local transport, perfusion, barrier integrity and tissue condition
+ Identification of ileal regions in imaging, endoscopy and specimens
- The complete digestive tract and whole-body nutritional regulation
- The jejunum, caecum, colon and appendix as independently modelled structures
- Crohn disease and other disease entities as diagnostic models
- Surgical procedures, endoscopic devices and treatment protocols
- The ilium, which is a pelvic bone
Characteristics
- Organism and reference anatomy
- Organism identifier, species and developmental stage Boundaries and expected features must be interpreted in the correct biological context.
- Ileal region and localisation
- Proximal ileum, distal ileum, terminal ileum or unspecified; localisation method required Functional specialisation and observation coverage vary along the segment.
- Distance from ileocaecal junction
- cm, with anatomical reference, measurement method and uncertainty Provides a reproducible location for lesions, biopsies and resections when the junction is identifiable.
- Segment length
- cm, distinguishing native, observed, resected and remaining length Prevents a specimen measurement from being mistaken for the amount of ileum retained in the organism.
- Wall thickness and luminal calibre
- mm, with modality, location and degree of distension Supports assessment of local structure without treating measurements from different conditions as equivalent.
- Mucosal and lymphoid features
- Observed villi, folds, ulcers and lymphoid aggregates; include method and unassessed features Supports tissue identification and characterisation of local mucosal condition.
- Absorptive competence
- Preserved, impaired, indeterminate or unassessed; specify substrate and evidence Bile acid handling and vitamin B12 uptake cannot be inferred reliably from gross appearance alone.
- Continuity and patency
- Native continuity, anastomosed, diverted or disconnected; patent, narrowed, obstructed or unassessed Records whether and where intestinal contents can traverse the ileal segment.
- Perfusion and viability
- Assessment with evidence, timestamp and uncertainty; unassessed permitted Local blood supply affects tissue integrity and the interpretation of functional observations.
Where this came from
wikidata · CC0 1.0
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 6 bundles · 11 layers · 17 findings · 27 questions.
Ileal identity and boundaries Establishes which intestinal segment is being represented and how its extent was determined.
Ileal identity depends on anatomical context, and the proximal boundary is less definite than the distal junction.
Intestinal position
Places the segment within the organism's small intestine.
Jejunal and caecal continuity
Record continuity with jejunum and the ileocaecal junction, including any alteration by surgery or congenital anatomy.
- What evidence identifies this structure as ileum within the specified organism? definition
- Which native or surgically altered structures connect to its proximal and distal ends? boundary
Regional extent
Distinguishes the whole ileum from local observations and isolated specimens.
Ileal region and coverage
Record the convention used for regional names and the length or area actually examined.
- How is the proximal ileal boundary or the label terminal ileum defined in this record? boundary
- How much ileum was observed, and how was its position relative to the ileocaecal junction established? measurement
Ileal wall and mucosal defence Describes the layered intestinal wall, absorptive surface and associated lymphoid tissue.
Ileal recognition and local integrity require distinctions between mucosal, deeper-wall and lymphoid observations.
Wall and surface architecture
Records folds, villi, crypts and wall layers at the resolution available.
Observed ileal architecture
Represent surface and wall features without assuming that a superficial biopsy describes the entire wall.
- Which folds, villi, crypts and wall layers are visible or sampled? measurement
- Does the observation concern mucosa alone or include submucosa, muscle and outer covering? boundary
Lymphoid tissue and barrier
Records aggregated lymphoid tissue and evidence concerning mucosal integrity.
Peyer patches and integrity
Distinguish expected ileal lymphoid structures from documented inflammatory changes and surface defects.
- What evidence identifies observed lymphoid aggregates as Peyer patches or another tissue feature? provenance
- Where are erosions, ulcers or other barrier defects observed, and how extensive are they? measurement
Specialised ileal absorption Represents the ileum's roles in bile acid recycling and vitamin B12 uptake.
These functions distinguish ileal loss or dysfunction from a generic reduction in intestinal surface.
Bile acid reclamation
Connects terminal ileal function to enterohepatic bile acid recycling.
Bile acid uptake capacity
Record evidence of bile acid absorption separately from anatomical preservation and downstream symptoms.
- What direct or indirect evidence supports the assessment of ileal bile acid reclamation? provenance
- What terminal ileal tissue remains in continuity, and what evidence describes its functional condition? measurement
Vitamin B12 uptake
Represents absorption of intrinsic-factor-bound vitamin B12 in the terminal ileum.
B12 uptake and upstream dependencies
Distinguish ileal uptake capacity from upstream availability of vitamin B12 and intrinsic factor.
- What evidence concerns terminal ileal vitamin B12 uptake rather than systemic vitamin B12 status alone? provenance
- Which upstream dependencies are represented by linked models when interpreting apparent uptake impairment? boundary
Ileal transit and tissue support Describes passage of intestinal contents and the local support needed to sustain the segment.
An anatomically present ileum may have impaired transit or perfusion, each requiring distinct evidence.
Luminal passage
Records calibre, patency and observed movement through the ileum.
Patency and propulsion
Separate structural narrowing from observed motility and passage of contents.
- Where is luminal narrowing or dilatation measured, and under what distension conditions? measurement
- What observations distinguish impaired propulsion from a mechanical restriction to passage? provenance
Mesenteric support
Records attachments and local vascular relationships relevant to ileal condition.
Ileal perfusion and attachments
Link the segment to its mesenteric support and document the basis for any perfusion or viability assessment.
- Which mesenteric and vascular relationships have been identified for this ileal segment? boundary
- Which method and observation time support the recorded perfusion or viability state? provenance
Ileal alteration and assessment Tracks local abnormalities, surgical changes and the limits of available observations.
An agent must distinguish observed tissue changes from diagnoses and retain the history needed to interpret remaining ileum.
Local abnormalities
Maps abnormal findings to ileal regions and tissue depth.
Abnormality distribution and evidence
Record inflammation, strictures, masses or other observed changes without treating location alone as a diagnosis.
- What is the location, extent and observed tissue depth of each ileal abnormality? measurement
- Which findings are directly observed, and which interpretations come from a separately documented diagnostic assessment? provenance
Surgical history and observation limits
Records altered continuity and determines which conclusions the evidence can support.
Remaining ileum and assessment coverage
Distinguish removed, diverted and functioning ileal segments and preserve gaps in examination coverage.
- What ileal regions were removed, diverted or reconnected, and what records establish the remaining anatomy? provenance
- Which unresolved question requires additional imaging, endoscopic, histological or functional assessment by a qualified professional? action
Evidence and external alignment What the world already says about this thing, gathered so the model can be checked against it.
A model that cannot be lined up against existing standards, identifiers and practice cannot be adopted by anyone who already uses them.
Reported evidence
Findings from the breadth pass, kept separate from the structural claims.
Check these first
Recalled without web access and unsourced; every item is a lead to verify.
- The description assumes human anatomy; ileal boundaries and organization differ among animal species.
- The three-fifths convention is approximate; absolute length varies with the individual and measurement method.
- This is recalled anatomical knowledge, not a source-verified account.
- Which of these check these first hold for the sense of ileum this model covers, and on what evidence? provenance
Identifiers and schemes
Recalled without web access and unsourced; every item is a lead to verify.
- Terminologia Anatomica - ileum - Standard anatomical name; not to be confused with ilium, a pelvic bone.
- Which of these identifiers and schemes hold for the sense of ileum this model covers, and on what evidence? provenance
Standards and regulation
Recalled without web access and unsourced; every item is a lead to verify.
- Terminologia Anatomica, maintained by the Federative International Programme for Anatomical Terminology (FIPAT), standardizes anatomical nomenclature.
- Which of these standards and regulation hold for the sense of ileum this model covers, and on what evidence? provenance
Real-world use
Recalled without web access and unsourced; every item is a lead to verify.
- Absorbs bile acids for return to the liver through enterohepatic circulation, particularly in the terminal ileum.
- Absorbs vitamin B12 bound to intrinsic factor, particularly in the terminal ileum.
- Continues absorption of nutrients, water and electrolytes.
- Supports intestinal immune surveillance through lymphoid tissue, including Peyer's patches.
- Provides tissue for selected reconstructive operations, including ileal pouches and urinary conduits.
- Which of these real-world use hold for the sense of ileum this model covers, and on what evidence? provenance
Typical measurements
Recalled without web access and unsourced; every item is a lead to verify.
- Approximate proportion of the human jejunoileal small intestine - Conventionally described as the distal three-fifths - fraction of length
- Which of these typical measurements hold for the sense of ileum this model covers, and on what evidence? provenance
Failure modes and hazards
Recalled without web access and unsourced; every item is a lead to verify.
- Crohn disease can cause ileal inflammation, strictures and fistulas.
- Obstruction or loss of blood supply can damage ileal tissue.
- Terminal ileal disease or resection can impair vitamin B12 absorption.
- Impaired ileal bile acid absorption can cause bile acid diarrhea; extensive loss can also impair fat absorption.
- Meckel's diverticulum is a congenital ileal outpouching that can cause bleeding, inflammation or obstruction.
- Which of these failure modes and hazards hold for the sense of ileum this model covers, and on what evidence? provenance
Neighbouring kinds and how to tell them apart
Recalled without web access and unsourced; every item is a lead to verify.
- jejunum - The jejunum precedes the ileum; their transition is gradual, without a sharp external boundary.
- cecum - The cecum belongs to the large intestine and receives the ileum at the ileocecal junction.
- terminal ileum - The terminal ileum is the distal segment of the ileum, not a separate organ or a synonym for its entire length.
- small intestine - The ileum is one subdivision of the small intestine, which also includes the duodenum and jejunum.
- ilium - The ilium is part of the pelvic bone; the ileum is part of the intestine.
- Which of these neighbouring kinds and how to tell them apart hold for the sense of ileum this model covers, and on what evidence? provenance
What the second pass must settle
- Does the registry intend a human anatomical model or a comparative model covering ilea across animal taxa?
- Which operational conventions should define the jejunum-ileum boundary and the extent of terminal ileum in each observation context?
- Which reference ranges for ileal dimensions and tissue features are appropriate by age, modality, specimen preparation and distension?
- What evidence and confidence criteria should justify classifying ileal absorptive competence, perfusion or viability?
- Which existing Vercy models own the ileocaecal junction, Peyer patches and mesentery, and how should this model reference them?