|Year : 2017 | Volume
| Issue : 1 | Page : 7-11
A cadaveric study on morphological variations of fissures and lobes in the human lungs and its clinical significance
K Gopalakrishna1, S Deepalaxmi1, SC Somashekara2, BS Rathna1
1 Department of Anatomy, Malabar Medical College and Research Centre, Kozhikode, Kerala, India
2 Department of Pharmacology, Malabar Medical College and Research Centre, Kozhikode, Kerala, India
|Date of Web Publication||9-Aug-2017|
Department of Anatomy, Malabar Medical College and Research Centre, Modakkallur, Atholi, Kozhikode - - 673 323, Kerala
Source of Support: None, Conflict of Interest: None
Background: Knowledge of the anatomy and variations of the major fissures are essential to recognize pulmonary abnormalities, for segmental lung resection and radiological interpretations.
Objective: To study the morphological variations of fissures and lobes in the human cadaveric lungs.
Materials and Methods: One hundred specimens of formalin-fixed adult lungs of unknown gender were studied and the following parameters were measured bilaterally: (a) presence or absence of complete or incomplete fissure, (b) presence of accessory fissure, and (c) length of fissures. The observations and measurements were recorded, compiled, and tabulated and the result was compared with the other studies.
Results: Length of oblique fissure was 29.36 ± 5.61cm with range of 17.9 - 42.0 cm on the right side and 26.81 ± 8.18 cm with range of 10.8–38.9 cm on the left side. Length of horizontal fissure was 10.2 ± 8.4 cm with range of 6.1–12.8 cm on the right side. Oblique fissure was complete in 84.0% cases on the right side and was in 82.0% cases on the right side. It was incomplete or absent in 16% (R) and 18% (L) cases. Horizontal fissure was complete in 74% and incomplete or absent in 26% of cases. Accessory fissure
was found in a total of eight lung specimens.
Conclusions: The knowledge of anatomy of fissures of the lung provides information on lobar anatomy with variations. The present study result and its comparison with other researches confirmed that lobar architecture is not constant. It emphasizes its usefulness in the diagnostic and surgical field.
Keywords: Bronchopulmonary segments, lung fissures, lung resection
|How to cite this article:|
Gopalakrishna K, Deepalaxmi S, Somashekara S C, Rathna B S. A cadaveric study on morphological variations of fissures and lobes in the human lungs and its clinical significance. J Exp Clin Anat 2017;16:7-11
|How to cite this URL:|
Gopalakrishna K, Deepalaxmi S, Somashekara S C, Rathna B S. A cadaveric study on morphological variations of fissures and lobes in the human lungs and its clinical significance. J Exp Clin Anat [serial online] 2017 [cited 2018 Mar 17];16:7-11. Available from: http://www.jecajournal.org/text.asp?2017/16/1/7/212645
| Introduction|| |
The lungs are the essential organs of respiration. Fissures are an integral part of the human lung. The oblique fissure divides the left lung into superior and inferior lobes. The right lung has both oblique and horizontal (transverse) fissures dividing it into superior, middle, and inferior lobes. The transverse fissure passes from the oblique fissure near the mid-axillary line horizontally forward toward the anterior border and then passes backward to the hilum on the mediastinal surface (Standring, 2008). The fissures facilitate the movement of the lobes in relation to one another, which accommodates greater distention and movement of the lobes during respiration. Thus, they help in more uniform expansion of the whole lung (Garg et al., 2013). The fissures may be complete when the lobes remain held together only at the hilum by the bronchi and pulmonary vessels, or they may be incomplete when there are areas of parenchymal fusion between the lobes, or they may be absent altogether (Rosse and Gaddum-Rosse, 1997). In addition to these fissures, accessory fissures may exist which are indicating junction between bronchopulmonary segments. Godwin and Tarver (1985) defined them as superior accessory fissure, inferior accessory fissure, or left minor fissure. An incomplete major fissure may lead to disease spread, collateral air drift, or “incomplete fissure sign” or postoperative air leakage for pulmonary resection (Hayashi et al., 2001).
For the description and comparison of different surgical techniques, Craig and Walker have proposed a fissural classification based on both the degree of completeness of the fissures and the location of the pulmonary artery at the base of the oblique fissure (Craig and Walker, 1997).
- Grade I: Complete fissure with entirely separate lobes
- Grade II: Complete visceral cleft but parenchymal fusion at the base of the fissure
- Grade III: Visceral cleft evident for a part of the fissure
- Grade IV: Complete fusion of lobes with no evident fissure line.
The fissures form the boundary of lobes, and it is necessary for the appreciation of lobar anatomy and to locate the bronchopulmonary segments.
| Materials and Methods|| |
This descriptive study design has received research approval (MMCRC/IEC/2014/dated June 20, 2014) from the Institutional Ethical Committee of Malabar Medical College and Research Centre, Calicut. A total of 100 specimens (right side 50, left side 50) of formalin-fixed adult lungs of unknown gender were collected from the Department of Anatomy and were used for conducting the research.
Specimens in good physical condition without damage were included in the study.
The specimens having pathological lesions, marks of previous surgery, damaged during removal with gross abnormalities were not included in the study.
Vernier calipers (least count 0.01 mm), magnifying lens, metallic probe, steel scale, divider and measuring tape, routine dissection instruments were used during the study.
Following parameters were measured bilaterally by direct inspection:
- Presence or absence of complete or incomplete fissure
- Presence of accessory fissure
- Length of fissures.
All the specimens were preserved in 10% formalin solution. The specimens were serially numbered. Every morphological detail of the natural fissures present in the lungs was recorded in a study worksheet. The anatomical classification proposed by Craig and Walker was followed to classify and determine the presence and completeness of fissures. The depth of oblique fissure was noted by introducing a rigid metallic probe perpendicular to the surface of the lung and then measuring it to the nearest millimeter. The depth was measured at upper end, lower end, and middle. The maximum depth was recorded. In the specimens where the oblique fissure was found to be incomplete, the obliterated distances were measured from the nearest point of the hilum. The measurements were taken independently three times by the same person and mean was recorded for further analysis. All the observations and measurements were carefully recorded, compiled, and tabulated and statistical analysis was done. Result was compared with those from other researchers.
From the above measurements, mean ± standard deviation, median, range, and mode were calculated.
| Results|| |
In the present study, following observations were made and are presented in [Table 1], [Table 2], [Table 3] and [Figure 1]. Length of oblique fissure was 29.36 ± 5.61 cm with range of 17.9 - 42.0 cm on the right side and 26.81 ± 8.18 cm with range 10.8–38.9 cm on the left side. Length of horizontal fissure was 10.2 ± 8.4 cm with range of 6.1–12.8 cm on the right side. Oblique fissure was complete in 84.0% cases on the right side and was in 82.0% cases on the right side. It was incomplete or absent in 16% (R) and 18% (L) cases. Horizontal fissure was complete in 74% and incomplete or absent in 26% of cases. Accessory fissure was found in a total of eight lung specimens (6 on right side and 2 on left side) on the costal surface.
|Table 1: Incidence of anatomical variations of fissures of right and left lungs (n=100)|
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|Table 2: Incidence and classification of fissures according to Craig and Walker criteria|
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|Figure 1: Right lung with only oblique fissure with accessory fissure in inferior lobe|
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| Discussion|| |
Comparative prevalence of anatomical variations of fissures of lung is given in [Table 4]. Any deviation from the normal developmental process occurring around 28 days of postfertilization will result in variation in the lobes and fissures morphology of the lungs (Sadler, 2010).
|Table 4: Comparison of results of different studies on variation of lung fissures|
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Incidence of absent or incomplete horizontal fissure of the right lung was 6% and 20% in the present study [Figure 2]. The study done in Andhra Pradesh, India, reported higher incidence of absent (14%) and lesser incidence of incomplete (8%) horizontal fissure (Nene et al., 2011). This result was different from other studies done in various regions of India, where they reported a higher incidence of both absent and/or incomplete horizontal fissure of the right lung. The magnitudes of absent fissure were 18%, 11.11%, 7.1%, 45.2%, 21.0%, and 34.62% and of incomplete were 25.0%, 50.0%, 17.1%, 67.0% and 38.89%, respectively (Drake and Wayne, 2010;Quadros et al., 2014; Prakash et al., 2010; Medlar, 1947; Bergman et al., 2010; Dutta et al., 2013).
Incidence of incomplete oblique fissure of the right lung was 14%, which is higher in the present study. Lower percentages were observed in other regions of India 6.0%, 10.0%, and 5.5%, respectively (Nene et al., 2011, Drake and Wayne, 2010;Quadros et al., 2014). In contrast, higher percentages of 39.3%, 25.6%–30%, 31.0%, and 61.54% were reported from the South Indian population and the studies from other countries (Prakash et al., 2010; Medlar, 1947; Bergman et al., 2010; Dutta et al., 2013).
Incidence of absent and incomplete oblique fissure of the left lung was 6.0% and 8.0%, respectively [Figure 3]. This study was in agreement with the similar observation from a study in South India (Drake and Wayne, 2010). In contrast, higher values of 12.0%, 35.7%, 10.6%, 30.0%, and 48.0% were observed in incomplete fissure South Indian population and the studies from other countries (Nene et al., 2011;Prakash et al., 2010; Medlar, 1947; Bergmann et al., 2010; Dutta et al., 2013).
Comparison of fissure classification
Fissures observed in the present study were classified by Craig and Walker criteria [Table 2] (Craig and Walker, 1997). They are nearer to the values observed in a study by Nene et al., 2010. The normal fissure enhances uniform expansion of lung and their position will serve as landmarks in locating the lesions within the lungs (Kent and Blades, 1942).
It is more common in infants (Rosse and Gaddum-Rosse, 1997), and commonly observed fissures are inferior accessory fissure, superior accessory fissure, and left minor fissure (Godwin and Tarver, 1985). The difference in the incidence of normality and laterality of fissures among populations may be due to variety of genetic and environmental factors.
Lung is a composite of endodermal and mesodermal tissues. The endoderm of the lung bud gives rise to the mucosal lining of the bronchi and to the epithelial cells of the alveoli. The vasculature of the lung, the muscles and cartilage supporting the bronchi are derived from the foregut splanchnopleuric mesoderm, which covers the bronchi as they grow out from the mediastinum into the pleural space. The respiratory diverticulum or lung bud develops from the foregut. After 28 days of fertilization, it divides into tracheobronchial tree which will develop into the right and left lungs (Sadler, 2010).
All the spaces between individual bronchopulmonary segments get obliterated, except along the line of division of principal bronchi, where deep complete fissures remain dividing the right lung into three lobes and left lung into two lobes (Hema, 2014). These fissures are oblique and horizontal in position on the right lung whereas oblique in position on the left lung (Larsen et al., 2001).
Along these fissures, the visceral pleura is reflected and covers individual lobes on all sides. Absence or incompleteness of a fissure could be due to obliteration of these fissures either completely or partially, indicating that partial fusion between lobes is common and more than half of the pulmonary fissures are incomplete. Accessory fissures are due to nonobliteration of spaces which normally are obliterated. The branching of stem bronchi accounted for them is often found in adult lung (Cronin et al., 2010).
Studies have recorded the importance of fissural anatomy in explaining various radiological appearances of interlobar fluid, extension of fluid into an incomplete fissure, or spread of diseases through them. Recognition of laterality of fissure in the lung improves understanding of pneumonia, pleural effusion, collateral air drift along with disease, carcinoma spreading within lung, postoperative air leakage in incomplete fissure and misinterpretation of accessory fissure as atelectasis or consolidation, and segmental localization of the lung for thoracic, cardiothoracic surgeons for planning segmental resections or pulmonary lobectomy. From a radiological point of view, an accessory fissure may commonly be misinterpreted as a lung lesion. On computed tomography scans, accessory fissures are seen as high attenuation curvilinear band. This simple study concurs and corroborates well with the previous study results (Berkmen et al., 1994; Ariyurek et al., 2001; Meenakshi et al., 2004).
| Conclusions|| |
The knowledge of anatomy of fissures of the lung provides information on lobar anatomy with variations. It is essential for segmental lung resection, for proper radiological interpretations, and for recognizing the abnormalities. The present study results and its comparison with other researches confirmed that lobar architecture is not constant. It emphasizes its usefulness in diagnostic and surgical field.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3], [Table 4]