|Year : 2021 | Volume
| Issue : 1 | Page : 46-50
A Comparative Study on Segmental Micro-Anatomy of the Human Fallopian Tube
Soumya Ramakrishnan1, Kumari Thoppilparambil Kunjunni2, Susan Varghese3
1 Assistant Professor, Department of Anatomy, Malabar Medical College Hospital and Research Centre, Kozhikode, Kerala, India
2 Professor, Department of Anatomy, Government Medical College, Thiruvananthapuram, Kerala, India
3 Additional Professor, Department of Anatomy, Government Medicval college, Kollam, Kerala, India
|Date of Submission||01-Oct-2020|
|Date of Decision||29-Oct-2020|
|Date of Acceptance||31-Dec-2020|
|Date of Web Publication||30-Jan-2021|
Villa No: 3, Silver Gardens, Kannadikkal, Kozhikode - 673 010, Kerala
Source of Support: None, Conflict of Interest: None
Background: The Fallopian tubes serve as a bridge between the ovary and uterus and is divided into infundibular, ampullary, isthmic, and intramural segments from lateral to medial. Each segment is structurally and functionally equipped to perform specific functions. The maintenance of normal micro-anatomy of each segment is very important for successful spontaneous pregnancy. This study has compared the histological features of the isthmus, ampulla, and infundibulum. Materials and Methods: Tissue bits were taken from isthmus, ampulla, and infundibulum of Fallopian tubes of 100 women of reproductive age group and these were subjected to routine histological processing, and slides were stained with hematoxylin and eosin. The mean value of the number of primary mucosal folds and muscle thickness of each segment was calculated and compared with each other. Results: In the ampullary and infundibular region, there were primary, secondary, and tertiary folds with a mean value of 33.42 ± 4.49 and 31.53 ± 4.92, respectively. In the region of the isthmus, there were few primary mucosal folds with a mean value of 8.31 ± 0.9. The muscular layer was found thickest inthe isthmus with a mean value of 7.72 ± 0.76 mm and in the region of ampulla and infundibulum, the mean values were 4.39 ± 0.57 mm and 3.43 ± 0.48 mm, respectively. Conclusion: The ampullary region has maximum number of branching mucosal folds which ensure close contact with the developing embryo and provides nutrition. At infundibulum also there were numerous mucosal folds which help in accommodating the large number of ciliated cells which plays a major role in ovum pick up and transport as the muscle layer was found to be very thin in this region. The peristaltic contraction of thick muscle layer in the isthmus plays a very important role in the transport of embryo as only a few mucosal folds were found in this region.
Keywords: Fallopian tube, mucosal folds, muscle thickness
|How to cite this article:|
Ramakrishnan S, Kunjunni KT, Varghese S. A Comparative Study on Segmental Micro-Anatomy of the Human Fallopian Tube. Natl J Clin Anat 2021;10:46-50
|How to cite this URL:|
Ramakrishnan S, Kunjunni KT, Varghese S. A Comparative Study on Segmental Micro-Anatomy of the Human Fallopian Tube. Natl J Clin Anat [serial online] 2021 [cited 2022 May 23];10:46-50. Available from: http://www.njca.info/text.asp?2021/10/1/46/308119
| Introduction|| |
The oviduct or Fallopian tube is the anatomical region where every new life begins in mammalian species. Effective tubal transport of ova, sperm, and embryo is a prerequisite for successful spontaneous pregnancy. Propulsion of gametes and embryo through the Fallopian tube is a complicated process achieved by the interaction between the ciliary activity of the cells accommodated in mucosal folds and muscular contractions. The Fallopian tube is not merely a passive conduit for gametes and embryo but an active organ where each segment is specialized to perform various functions that lead to fertilization. Starting from the ovarian end and proceeding toward the uterus it is divided into infundibular, ampullary, isthmic, and intramural segments. The secondary oocytes at metaphase 2 are released into the infundibulum during ovulation which are then transported to the ampulla. The isthmus of the Fallopian tube provides favorable environment for sperm motility, maturation, and capacitation. Ampulla provides an appropriate environment for fertilization. Thus, each segment of the Fallopian tube has got its own unique functions which may be attained by the versatile disposition of histological layers in each segment. Maintenance of the normal anatomy of each segment of the Fallopian tube is very essential for successful spontaneous pregnancy. In chronic salpingitis agglutination of mucosal folds occurs which affects the motility of gametes resulting in infertility, or in some cases, it may allow sperm to pass through, but prevent the transport of larger morula which may lead to ectopic pregnancy. The study of normal anatomy is very important in understanding the miraculous biology behind fertilization and embryo development. A pathologist should have a thorough knowledge of the normal architecture in each segment of the Fallopian tube to diagnose clinical conditions. Tubal ligation is a very commonly done surgical procedure and pathologists should verify the presence of a complete cross-section of the tube. Various pitfalls can occur from pathologist's side in diagnosing the Fallopian tube pathologies in the absence of lumen, as para tubal cyst with rudimentary plicae may mimic the Fallopian tube. This again points out the importance of knowing the normal histology. Various studies have either examined one segment of the Fallopian tube or conducted their studies in animal uterine tubes. Cyclical variations in tubal mucosa and various other aspects have been well studied, but the characteristics of each segment of the Fallopian tube are least studied. Hence, undertaking such a study appears to be worthwhile.
The aim of this study is to compare the number of primary mucosal folds and muscle thickness of isthmic, ampullary, and infundibular segments of the Fallopian tube. Due to technical difficulties, the intramural part of the tube could not be included in this study.
| Materials and Methods|| |
Study design and duration
For this descriptive cross sectional study. A total of 100 samples of Fallopian tubes were obtained from women undergoing hysterectomy in Sree Avittom Thirunal Hospital, Thiruvananthapuram, Kerala. These samples were collected from the Department of Pathology, Government Medical College Thiruvananthapuram, from June 2014 to May 2015 where the specimens were sent for biopsy. Women of reproductive age group ranging from 32 to 45 years were selected for the study. Those specimens in which tubectomy was done, and suspected cases of ectopic pregnancy, Fallopian tube neoplasms, and pelvic inflammatory disease were not considered for this study. The tissue bits were taken from the midpoint of the isthmus, ampulla, and infundibulum of each Fallopian tube and collected in separate bottles containing 10% formalin. After 24 h of fixation, the specimens were subjected to routine histological processing which included dehydration, clearing, impregnation, and paraffin embedding. The paraffin blocks thus obtained were sectioned at a thickness of 5 μ using a rotary microtome. These sections were incubated for 1 h and stained with hematoxylin and eosin. Stained slides were mounted in DPX. The mounted sections were observed under the light microscope. Each of the slides was examined under ×4 objective and the number of primary mucosal folds whose basal attachments were seen were counted. The thickness of the muscle layer was measured at the area of maximum thickness using image pro. 3DS 6.1 software. Statistical analysis was performed using SPSS version 17 (SPSS Inc., Chicago). The mean value of mucosal folds and muscle thickness of each segment was calculated and compared with each other. Inorder to demonstrate the arrangement of muscle fibers in isthmic, ampullary, and infundibular segments of the Fallopian tube, Masson's Trichrome stain was used.
The study protocol was approved by Ethical Committee and Research Committee of Government Medical College, Thiruvananthapuram (letter no. IEC.No. 01/45/2014/MCT dated 17/01/2014).
| Results|| |
Of the Fallopian tubes studied 29% of them belonged to women of age group 32–36, 28% belonged to age group 37–40 years and 43% belonged to age group 41–44 years.
Comparision of isthmic, ampullary, and infundibular mucosal folds
The number of mucosal folds found were least in the isthmus and maximum in the ampulla. The mean number of mucosal folds in the ampullary region was 4.8 ± 0.55 times the mean number of mucosal folds in the isthmic region. The mean number of ampullary mucosal folds was 1.07 ± 0.09 times greater than the mean number of infundibular mucosal folds. The mean number of infundibular mucosal folds was 4.53 ± 0.68 times greater than the mean number of isthmic mucosal folds [Table 1] and [Figure 1], [Figure 2].
|Figure 1: Ampullary region of the Fallopian tube showing numerous mucosal folds (H and E, ×40)|
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|Figure 2: Infundibular region of the Fallopian tube showing numerous mucosal folds (H and E, ×40)|
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|Table 1: Comparison frequency of distribution of isthmic, ampullary, and infundibular mucosal folds|
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It is the middle layer of the Fallopian tube and consists of inner circular and the outer longitudinal layer which are held together by connective tissue [Figure 3]. With Masson's Trichrome the cytoplasm stained pink resulting in pink color of smooth muscles and epithelium, collagen fibers-stained blue, and nuclei-stained black.
|Figure 3: Longitudinal muscles of ampulla region of the Fallopian tube (H and E, ×100)|
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Comparision of the thickness of the muscular layer in isthmus, ampulla, and infundibulum
The thickness of the muscular layer was maximum in the isthmus and least in infundibulum. The mean muscle thickness at isthmus was found to be 2.27 ± 0.23 times than that of the infundibulum and 1.77 ± 0.13 times than that of the ampulla. The mean thickness of the muscular layer at ampulla was 1.29 ± 0.1 times than that of the infundibulum [Table 2] and [Figure 4], [Figure 5].
|Figure 5: Infudibulum region of the Fallopian tube showing thin muscle layer (H and E, ×100)|
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|Table 2: Comparison of the thickness of the muscular layer in the isthmus, ampulla, and infundibulum of fallopian tube|
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In the slides stained with Masson's Trichrome, it was found that in the region of isthmus the muscular layer consists of densely packed muscle fibers which stained pink in color, with few collagen fibers in between which stained blue color. In the region of the ampulla, the muscle fibers were less dense compared to that of the isthmus with a moderate amount of collagen fibers in between. In the region of infundibulum, the muscle fibers were scanty with abundant collagen fibers in between [Figure 6],[Figure 7],[Figure 8].
|Figure 6: Isthmus region of Fallopian tube showing muscle layer (Masson's Trichrome staining, ×100)|
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|Figure 7: Ampulla region of Fallopian tube (Masson's Trichrome staining, ×40)|
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|Figure 8: Infundibulum region of Fallopian tube showing thin muscle layer (Masson's Trichrome staining, ×100)|
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| Discussion|| |
In the present study, the number of primary mucosal folds in the isthmus, ampulla, and infundibulum were counted. The number of mucosal folds was found maximum in the ampulla and minimum in the region of the isthmus. In ampullary and infundibular sections there were primary, secondary, and tertiary foldings of the mucosa, but in the region of isthmus only primary mucosal folds were present. The number of mucosal folds reported in our study is inline with the Tripathy study, in which he mentioned that in the ampulla the mucosal folds were maximum, and in the region of isthmus there were few longitudinal folds. Crum has also described the arrangement of mucosal folds in different parts of the Fallopian tube, the mucosal folds being maximum in the ampulla, and least in the isthmus. In the study conducted by Hiroyuki also he has described elaborate mucosal folds of the ampulla which were more numerous than that of the infundibulum. In the region of the isthmus as described by him, the folds were short and less branched. As cited by Brosens the mucosa of the ampulla and infundibulum is highly folded and in isthmic region the folds decrease drastically to about 4–5 in number. Mutter and Prat have described mucosal folds forming complicated maze-like pattern in the ampulla, which become less complex towards medial end forming a stellate lumen in the isthmus. Weidner et al. have also described numerous, slender, long, complex plicae at ampulla which changes in its architecture and number to few, blunt plicae at the isthmus.
The thickness of the muscle layer reported in our study is inline with study conducted by Pauerstein and Eddy. According to Mutter and Prat, the tubal musculature is thinnest at the distal end of the tube and thicker as the cornua is approached. Tripathy has also mentioned about the muscular layer to be well developed in the isthmus and thinning out near fimbrial end. According to Weidner et al. also the muscle layer is thick in the isthmic region. The findings in the present study were in accordance with descriptions given by other authors where muscle layer was thickest in the isthmic region and thinnest in the infundibulum. The thick muscle layer at the isthmus has its own functional importance. It is mainly by the peristaltic contractions of the muscle layer at isthmus that the gametes and embryo are transported, as mucosal folds are minimal in this segment. The thick muscle layer also acts as a sphincter which helps to retain the embryo in the ampulla for a period of 48–72 h to expose the embryo to nutritious oviductal fluid and to delay the entry of the embryo to the uterus until it is well prepared to nourish the developing embryo. Thus, it is the highly convoluted mucosal folds at the infundibular region that plays a major role in effective capture and transport of ovum towards ampulla as the muscle layer is not well developed here for effective peristaltic contractions. In the ampulla which is the site of fertilization, the mucosal folds were found maximum in number which ensures close contact between the embryo and the cells of the tube so that the embryo gets its best possible nutrition. The muscle layer was found thickest in the isthmus where peristaltic contractions of this layer aid in the transport of embryo towards uterus as mucosal folds are not well developed here. This thick musculature also acts as a sphincter for some time to delay the entry of embryo to the uterus until the uterus is well prepared to receive the developing embryo. Once the endometrium of the uterus is decidualised the isthmic sphincter is relaxed and then the peristaltic contractions of thick musculature aid in embryo transport.
There has been a significant rise in the incidence of ectopic pregnancy in recent years from 3–4 per 1000 to 16/1000 of which tubal pregnancy accounts for 95% of cases. Salpingoscopy and falloscopy done on these cases revealed a reduction in number, flattening, and distortion of mucosal folds. American fertility Society has even proposed a scoring system for the prognosis of fertility outcomes based on many factors of which the percentage of mucosal folds forms an important one. Salpingitis Isthmic Nodosa which has a strong association with tubal pregnancy is characterized by diverticula of tubal epithelium surrounded by hypertrophied smooth muscle. Although the most common site of tubal pregnancy is in the ampulla (70%), pregnancies at the isthmic region are more prone for rupture as a thick muscle layer at the region prevents the expansion, leading to inability to accommodate the growing fetus. Surgical outcomes after tubal repair surgeries are inversely proportional to the degree of mucosal damage and tubal thickness.
Limitation of the study
Due to less hysterectomies done below the age of 30 years, the sample from this age group was not represented in this study. Hence, Fallopian tube histological evaluation of the present study may not depict the functional outcomes.
| Conclusion|| |
We conclude that each segment of the Fallopian tube is unique in its histological characteristics in the aspects of the number of mucosal folds and muscle thickness. In ampullary and infundibular regions, there was the large number of mucosal folds. The muscle layer was found to be very thin in the infundibular region with a slight increase as we move toward the ampullary region and thickest at the isthmus.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8]
[Table 1], [Table 2]