#teratology

• From the egg / From the very beginning — A Latin phrase derived from Horace's writings, meaning literally 'from the egg'. In embryology and developmental toxicology, it refers to analyzing a biological process, cellular mechanism, or the action of a teratogenic agent (malformation-inducing toxin) traced right from the egg-cell (zygote) stage or from the moment of fertilization to fully map fetal development disruptions.
• Ablepharia — The congenital partial or total absence of eyelids, studied in physical anthropology, comparative zoology, and developmental biology to understand evolutionary genetic mutations and structural anomalies in vertebrates. In paleoanthropological and animal population dynamics studies, this morphological trait is analyzed as an extreme recessive feature that affects adaptability and visual apparatus protection in environments with intense solar exposure.
• Abrachia — An extremely rare congenital malformation characterized by the complete absence or rudimentary development of the arms (upper limbs) in a fetus or developing organism; a severe anatomical anomaly within the category of limb agenesis, similar to or closely related to amelia and congenital abrachia.
• Abrachiocephalus — A teratological monster, fetus, or organism with severe congenital malformations, characterized by the simultaneous absence of both arms and the head, or by the abnormal and rudimentary fusion of cephalic structures in the complete absence of upper limbs; (adjectival) presenting the anatomical features of this embryonic developmental anomaly.
• Abrachiocephaly — A complex and extremely severe congenital malformation characterized by the simultaneous absence of both the head (acephalia) and both upper limbs (abrachia) in a fetus or developing organism; an early embryonic developmental anomaly, incompatible with life, studied within classical and experimental teratology.
• Acardia — A congenital absence of the heart or a complete cessation in the ontogenetic development of the cardiac structure in a fetus. This severe structural anomaly is incompatible with independent extrauterine life and is documented almost exclusively within monochorionic multiple pregnancies with asymmetric development (TRAP sequence), where the affected fetus's blood circulation is maintained solely by its twin's heart through placental vascular anastomoses.
• Adactyly — A rare congenital malformation characterized by the total or partial absence of fingers or toes. This structural anomaly of embryonic development can occur in isolation or as part of a complex malformativ syndrome, determined by genetic mutational factors or external teratogenic insults suffered by the embryo during the first weeks of pregnancy.
• Agenosomia — A severe congenital malformation of a teratological nature, characterized by the incomplete development or partial to total absence of external genital organs and the lower abdominal wall, frequently associated with visceral eventration. This severe structural anomaly is clinically investigated within fetal pathology and is commonly considered incompatible with long-term extrauterine survival.
• Amyelencephalus — A medical term from the field of teratology denoting a fetus or congenitally malformed organism structurally characterized by the total absence or severely impaired development of the spinal cord (amyelia) and the myelencephalon (embryonic medulla oblongata). This severe neurological anomaly is incompatible with life and is investigated within major neural tube defects.
• Amyelia — An extremely rare and severe congenital malformation within the neural tube defects spectrum, characterized by the total absence or complete developmental arrest of the spinal cord. This severe structural anomaly occurs during the first weeks of embryogenesis due to the failure of the posterior neuropore to close, being incompatible with extrauterine life and often associated with other major cranial malformations.
• Apneumia — An extremely rare congenital malformation characterized by the complete, structural, and anatomical absence of one or both lungs, resulting from an early developmental arrest of the respiratory bud during the embryonic stage. This severe anomaly is investigated within fetal pathology and is typically associated with other major systemic defects.
• Apodia — An extremely rare congenital malformation characterized by the complete, unilateral or bilateral, absence of feet or lower limbs at birth; a severe structural anomaly of embryonic development. In teratological practice, this condition is studied in close connection with dysmelia and phocomelia, representing the early developmental arrest of lower limb buds.
• Incomplete brain development — A rare and extremely severe congenital malformation characterized by the incomplete, faulty development or developmental arrest of the encephalon (specifically the cerebral hemispheres and telencephalon) during the embryonic period. This severe structural anomaly is frequently associated with major defects of the neural tube or cranial vault, being studied within clinical teratology.
• Automelia — A rare form of congenital morphological anomaly or teratological monstrosity in insects, characterized by the presence of one or more supernumerary appendages (legs, antennae) abnormally inserted onto their own thoracic or cephalic segments, often as a result of aberrant embryonic division. In structural entomology, this phenomenon is studied to understand homeotic mutations and the genes controlling segmentation and correct body axes development.
• Automorphosis — A morphological anomaly, spontaneous structural modification, or direct malformation occurring in a plant, caused exclusively by internal factors (genetic, physiological, intrinsic hormonal), independent of any direct action from the external environment or parasites. In plant histology, this phenomenon is studied to understand spontaneous deviations from the normal growth pattern and spontaneous somatic mutations within meristematic tissues.
• Autosite — The component in a pair of asymmetric double monsters or siamese twins that is anatomically fully developed and capable of independent life, sustaining metabolically the other rudimentary, parasitic, or incomplete twin attached to its body.