--- module: 075-01 language: en chapter: 75 title: "Anatomical Language, Body Plans, Fascia, Compartments, and Imaging Anatomy" module_title: "Anatomical orientation, body organisation, variation, and relationships" source_sha256: adc45201e0e6258f5e0bc8d9b9595fbfe321dfc6e334d8b45f5212cc14ac8472 --- # Anatomical orientation and relationships ## Relational language ### Supports physiology and clinical localisation ### Consistent across position, plane, organ shift ### Conventions, not the observer's viewpoint ## Anatomical position and planes ### Upright, facing forward, palms anterior ### Right and left refer to the subject #### Prone position or rotated image changes nothing ### Paired directional terms #### Superior-inferior, anterior-posterior #### Medial-lateral relative to the midline #### Proximal-distal need a stated origin #### Superficial-deep measure distance from surface ### Internal-external: inside or outside a structure #### Not generally medial and lateral ### Deep and lateral are independent relations ### Sagittal, coronal, transverse, oblique planes #### Section appearance depends on plane and convention ### Imaging display conventions #### Axial viewed from feet: right on viewer's left #### Coronal viewed facing the patient #### Sagittal needs orientation markers ## Movement about joints ### Flexion decreases, extension increases angle ### Dorsiflexion and plantarflexion at the ankle ### Abduction and adduction relative to midline ### Rotation around a longitudinal axis #### Supinated palm anterior, pronated posterior #### Inversion and eversion of the sole ### Opposition and reposition of the thumb ### Elevation, depression, protraction, retraction ### Circumduction combines movements in a cone ### Terms give direction, not muscle or force #### Path set by geometry, ligaments, muscles, load ## Regions and cavities ### Axial body versus appendicular limbs ### Abdominal quadrants or nine regions #### Organs cross boundaries and shift ### Cranial and vertebral cavities hold the CNS ### Ventral cavity divided by the diaphragm #### Thorax: two pleural cavities and mediastinum ### Peritoneal cavity is a potential space #### Intraperitoneal organs suspended by mesentery #### Retroperitoneal organs: primary or secondary ### Serous membranes: parietal and visceral layers #### Air, blood, or fluid expands the spaces ##### Organ function impaired ## Tissue layers and continuity ### Superficial fascia permits skin movement ### Deep fascia invests muscles, forms compartments ### Tendons, aponeuroses, ligaments ### Raphe, retinaculum, bursa: form and function ### Arteries leave the heart regardless of oxygen ### Anastomoses may provide collateral flow #### Presence does not guarantee capacity ### Lymphatics return fluid via regional nodes #### Explain oedema, infection spread, metastasis #### Sentinel node, but pathways can change ## Organs by surfaces and relations ### Relations predict structures at risk ### Hilum: where vessels and ducts enter ### Mesenteries carry vessels, allow movement ### Adventitia blends, serosa gives free surface ### Hollow organ wall layers #### Mucosa, submucosa, muscle, outer layer #### Arrangement predicts spread of disease ## Anatomical variation ### Vessels, muscles, nerves, organs, ducts, skeleton ### Most asymptomatic, some alter procedure risk ### Variant versus anomaly: prevalence and function ### Malformation, disruption, deformation, dysplasia ### Laterality: organ reversal to heterotaxy ### Plan on the patient's actual anatomy ### Averages are not rigid categories #### Gender identity does not establish organs ## Surface anatomy as a probabilistic map ### Palpable bones, tendons, pulses, creases ### Projections shift with breathing and position ### Ultrasound gives direct visual guidance ### Dermatomes and nerve territories overlap #### Sensory loss rarely follows drawn lines ### Myotomes: predominant root contribution ### Translate among body, dissection, diagram, image