The dissertation work is devoted to researching prenatal development and syntopy of intercostal space (ICS) structures of the person. The dissertation established individual and age anatomical variability of the skeleton of the thorax, fascial and muscular as well as neurovascular formations of ICS in the fetal period of human ontogenesis.
The study was conducted on 118 specimens of human embryos, prefetuses and fetuses without external signs of either anatomical abnormalities or abnormalities in the skeleton development of the thorax and structures of the ICS. The material was divided into age groups according to the period classification of human ontogenesis and periodization of fetal development on the basis of parietal-coccygeal length measurements (PCL).
The results of the conducted study showed that the formation process and prenatal development of the morpho-functional system of human ICS occurs in close correlation with embryogenesis and stage-by-stage complication of bone structures (thoracic vertebrae, ribs, sternum), fascial and muscular, first of all, intercostal muscles, and neurovascular structures of ICS.
Development peculiarities of intercostal nerves (ICN) and the complication of the nerve-tissue relationships in the 5-week-old human embryos play an important role in the normal formation process of both components of ICS and thorax morphogenesis as a whole. Formation of ICN branching (formation of connections, connective, bypass and muscle branches as well as branches to the internal thoracic artery (ITA), etc.)) begins at the 6th week of fetal life (embryos 9.5-10.0 mm PCL) and precedes the formation of their stem structure in the 9-week-old prefetuses (34.0-37.0 mm PCL).
The study established asymmetry of the right and left thoracic neurovascular bundles in human fetuses, which consists in the length and syntopy differences of the internal thoracic vessels and the thoracic nerve as well as asymmetry of the ITA beginning and variability of branch topography in its rib section. From the 4th to the 10th month of fetal development (FD) the length of the right ITA increases from 19.07 ± 3.30 mm to 77.00 ± 4.47 mm, and the length of the left ITA from 18.71 ± 2.52 mm up to 74.94 ± 3.78 mm, increasing, on average, by 4 times. Starting at the costal cartilage of the VII rib to the IV-III ICS (on the right) and to the III-II ICS (on the left) ITA are accompanied, as a rule, by two veins of the same name. In fetuses aged 7-10 months, the fusion of medial and lateral internal thoracic veins (ITV) into the common vein trunk on the right and left is mostly asymmetric and occurs at different skeletotopic levels: in the III ICS (61.9% on the right and 64.29% on the left), in the II ICS (14.29% on the right, 25% on the left), in the IV ICS (23.81% on the right and 7.14% on the left), in the I ICS (3.57% on the left).
The study has revealed the variability of the topography and asymmetry of ICN trunks and their branches, anterior and posterior intercostal vessels on the right and left during the fetal period of human ontogenesis. The components of the intercostal neurovascular bundle, depending on the ordinal number of the ICS and sections of the thoracic or abdominal walls, have their own topographic and anatomical features. The trunks of adjacent ICN and posterior intercostal vessels are connected by connecting branches. Connecting branches also lead from nodes of thoracic part of a sympathetic trunk to the ICN. ICN branch mainly at the level of the middle axillary line into anterior and lateral musculoskeletal branches.
Morphometric examination revealed the greatest width of the II ICS; during the human fetal period, the width of the right II ICS along the thoracic line increases from 2.14 ± 0.24 mm to 8.69 ± 0.92 mm, and the width of the left ICS from 1, 97 ± 0.26 mm to 8.14 ± 0.93 mm, increasing by 4.1 times. The greatest width of the following ICS was established: in fetuses of 4-6 months - of three upper ICS on the right and left thoracic lines; in fetuses of 7-10 months - of the II and III ICS on the thoracic and midclavicular lines, the II, IV and VII ICS on the posterior axillary and scapular lines. The width of the aforementioned ICS exceeds the height of the corresponding ribs along the above-mentioned lines. Ribs possess the greatest height on the midclavicular lines, while the fetuses of 4-5 months revealed the greatest height value of the III rib, and the fetuses of 6-10 months - the VII rib. The maximum length values of the rib cartilage and the length of the bone part were noted in the VII rib, and the lowest length values of the rib cartilage were noted in the I rib and the length of the bone part in the XII rib.
