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 Table of Contents  
Year : 2023  |  Volume : 12  |  Issue : 1  |  Page : 31-35

Morphological study of musculi pectinati and crista terminalis with its applied significance in the human adult cadaver

1 Assistant Professor, Department of Anatomy, Hi-Tech Medical College and Hospital, Rourkela, Odisha, India
2 Assistant Professor, Department of Anatomy, RIMS, Ranchi, Jharkhand, India

Date of Submission02-Dec-2022
Date of Decision19-Jan-2023
Date of Acceptance30-Jan-2023
Date of Web Publication21-Feb-2023

Correspondence Address:
Ravi Keshri
Flat No. 201, Anand Apartment, Bariatu Housing Colony, Ranchi - 834 009, Jharkhand
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/NJCA.NJCA_235_22

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Background: Morphological studies have highlighted the roles of the crista terminalis (CT) and musculi pectinati (MP) in the process behind cardiac arrhythmias. It is also intriguing to explore the notion that structural problems with the CT and MP may be the major anomaly in those who have atrial flutter and may also account for the incidence of atrial flutter even in people with atria that appear to be normal. The aim is to study the cumulative arrangement and morphology of CT and MP in the right atrium of formalin-fixed human cadavers. Methodology: Cross-sectional descriptive research was conducted on thirty hearts obtained from formalin-embalmed adult human cadavers of the age range between 25 and 65 years (22 males and 8 females). Anatomical course, arrangements, and variations of CT and MP were observed and noted. Results: After meticulous dissection of formalin-fixed human heart, variations associated with the morphological traits of the MP and taenia sagittalis (TS) were observed and recorded. According to the gross anatomical architecture of CT and associated MP, it was classified into six various patterns. Type 1 (MP oriented nearly 90° to CT) was found to be the most common variant, exhibited by 16 (53%) hearts, Type 2 (MP oriented parallel to CT) was noted in 1 (4%), 7 (22%) shown Type 3 (combination of Type 1 and Type 2), Type 4 (branching of the MP) was noted in 2 (7%), Type 5 (interlacing trabeculation) was seen in 3 (10%), whereas Type 6 (prominent muscular column of MP) was present in 1 (4%) of the heart. In addition, the observation on TS (prominent band of MP, seen emerging from CT) was also classified into three groups – Type A (TS was absent) was noted in 15 (50%) hearts was the most common variant, Type B (single trunk of TS) was present in 3 (10%) and Type C (multiple trunks of TS) in 12 (40%) hearts. Conclusion: Cardiovascular catheterization frequently results in injury to Type 6 MP and Type B/Type C TS, which have a more intricate arrangement of fibers. Henceforth, collectively the incidence of these clinically relevant variants was a little more than 50%.

Keywords: Crista terminalis, musculi pectinati, right atria, taenia sagittalis

How to cite this article:
Keshri R, Ranjan R. Morphological study of musculi pectinati and crista terminalis with its applied significance in the human adult cadaver. Natl J Clin Anat 2023;12:31-5

How to cite this URL:
Keshri R, Ranjan R. Morphological study of musculi pectinati and crista terminalis with its applied significance in the human adult cadaver. Natl J Clin Anat [serial online] 2023 [cited 2023 Mar 20];12:31-5. Available from: http://www.njca.info/text.asp?2023/12/1/31/370142

  Introduction Top

The right atrium of the heart contains a vertical fibromuscular ridge of smooth myocardium called the crista terminalis (CT), situated on the chamber's posterolateral wall, which stretches inferiorly from the right side of the superior vena cava (SVC) orifice to the same side of the inferior vena cava (IVC) valve.[1] Correspondingly, the sulcus terminalis, a shallow groove stretching between the right side of the aperture of the two venae cavae, marks the interface between the venous component (sinus venosus), and the atrium proper externally. The CT is an important anatomical landmark because of its connections to the sinoatrial (SA) nodal artery and the site of the musculi pectinati (MP) genesis. The MP is made up of myocardial ridges that run anteriorly and laterally from the CT to the auricle. Often, a prominent band-like bundle of MP is seen emerging from CT, extending in an anterosuperior direction termed as taenia sagittalis (TS).[2] From an embryological perspective, the fetal right atrium grows from two different sources:

  1. The right horn of the sinus venosus gives rise to the smooth area of the right atrium's wall known as the sinus venarum, and
  2. The right sinoatrial valve gives rise to the CT as well as the valves of both the IVC and coronary sinus. The primordial right atrium becomes the right auricle, a conical muscular pouch exhibiting MP.

The left horn of the sinus horn develops into the coronary sinus.[3]

An apparent CT on an echocardiogram may be mistaken for a tumor or thrombosis in the right atrium.[4],[5] Therefore, by understanding the anatomy and making the appropriate identifications, it is feasible to avoid a misdiagnosis.[6] The current study was designed and executed to explain the morphological pattern of the MP and TS, taking into account that there are only a few studies that assess the gross features of MP in connection to CT.[2]

Aims and objectives

  1. To note the gross arrangement and morphology of CT in the right atrium
  2. To observe the variants of MP and its orientation with respect to CT
  3. To note the presence of TS and the variants thereof.

  Materials and Methods Top

After getting approval from the institutional ethics committee (Approval number 29. Dated-June 03, 2018), the study was conducted in the Department of Anatomy of the Institute located in the central part of Jharkhand, a state situated in the eastern part of India. A cross-sectional descriptive study was conducted over a span of 24 months on 30 human hearts obtained from 30 (22 males and 8 females) formalin-preserved adult human cadavers of north Indian heritage with the age range between 25 and 65 years. The specimen included for the investigation had neither any signs of prior surgical operations, nor severe injuries, and no obvious or apparent pathology of any kind. To get a reliable view of the CT and MP, the SVC and IVC were cut open posteriorly along a line to reveal the interior of the right atrial chamber. Another incision was made right angles to the first cut, in line with the coronary sulcus, to preserve the near normal morphology of CT and MP. The remaining blood clots were removed by washing them under running tap water for clear visualization.

Gross anatomy of both MP and CT and their variant patterns were noted with the help of a magnifying glass with an emphasis on:

  1. Morphology of CT and MP
  2. Arrangement of MP emergence with respect to CT
  3. Presence of taenia saggitalis and its variations.

Each of these morphological variations and patterns was meticulously documented using photographs.

  Results Top

Based on the morphological characteristics of MP's emergence from Chordae Tendinae, their arrangements and orientations, MP was classified into six subtypes, similar to the classification described by Siddiqui et al.[7]

  1. Type 1: MP oriented diagonal to Chordae Tendinae with equidistant spacing [Figure 1]
  2. Type 2: MP emerging alongside Chordae Tendinae with equidistant spacing [Figure 2]
  3. Type 3: composite pattern of Type 1 and 2 with multiple muscle trunk [Figure 3]
  4. Type 4: MP exhibiting a branching pattern [Figure 4]
  5. Type 5: Nonuniform MP arranged in a random and trabecular manner with multiple interlacing crossovers [Figure 5]
  6. Type 6: MP exhibiting pronounced musculature columns [Figure 6].
Figure 1: MP emerging perpendicular to CT (MP Type 1). MP: Musculi pectiniti, CT: Crista terminalis

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Figure 2: Exhibiting MP emerging parallel to CT (MP Type 2). MP: Musculi pectiniti, CT: Crista terminalis

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Figure 3: Exhibiting a mixed variant (MP Type 3). MP: Musculi pectiniti, CT: Crista terminalis

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Figure 4: A branching pattern (MP Type 4). MP: Musculi pectiniti, CT: Crista terminalis

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Figure 5: Exhibiting Trabeculation with cross-over (MP Type 5). MP: Musculi pectiniti, CT: Crista terminalis

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Figure 6: Exhibiting prominent muscular column (MP Type 6). MP: Musculi pectiniti, CT: Crista terminalis

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Analysis indicates that 16 out of 30 specimens were of Type 1 variant (53%) and 1 (4%) fall into Type 2 category. Pronounced musculature columns (Type 6) were reported in 1 (4%) sample. Results are summarized in [Table 1].
Table 1: Exhibiting the variant patterns of musculi pectiniti (n=30)

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Furthermore, the prominent band-like bundle of MP wherever emerging from CT, i.e. TS is noted, and was subsequently divided into two categories.

  1. Type A: No TS [Figure 7]
  2. Type B: Solitary prominent bundle of TS [Figure 8]
  3. Type C: Two or more prominent bundles of TS [Figure 9].
Figure 7: A complete absence of (TS Type A). TS: Taenia sagittalis

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Figure 8: Exhibiting a single and prominent (TS Type B). TS: Taenia sagittalis

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Figure 9: Exhibiting multiple (TS Type C). TS: Taenia sagittalis

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TS was not present in the majority of cases. Results are summarized in [Table 2].
Table 2: Exhibiting the variant patterns of taenia sagittalis (n=30)

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Three out of 30 specimens (10%) revealed a solitary trunk of TS. The presence of several TS bundles was another intriguing finding that was made in 12 specimens (40%). [Figure 7], [Figure 8], [Figure 9] show the photographs of the results, which are summarized in [Table 2].

  Discussion Top

A common heart pathology that can be followed by serious cardiac disorders is atrial dysfunction. The development of effective therapeutic strategies will be greatly aided by a deeper comprehension of the fundamental mechanisms underpinning normal atrial anatomy, function, and dysfunction. Atrial excitation conduction appears to be significantly influenced by anatomical structure, interatrial and intra-linkage, rapid conduction bundles, and electrophysiological heterogeneity under both physiological and pathological situations. The SA node, CT, MP, and interatrial connections are the most crucial anatomical components for the genesis and continuance of atrial excitation. An effective and complementary technique for examining the dynamic behavior of atria is the precise anatomical model of human atria.[8]

Due to the intricacy of atrial geometry, natural barriers and orifices will inevitably limit the expansion of stimulation from the point of source of the cardiac impulse. According to physiological evidence, the CT serves as an obstruction to conduction across it at the occurrence of the typical atrial flutter.[9],[10] Even though the hindrance of the CT is thought to be anatomically static, tracing probes in animal models have revealed tangential propagation over the CT in healthy hearts.[11] Greater CT diameter was linked to the prevalence of atrial flutter, as reported by Mizumaki, et al.[12] in 2002. Studies have also suggested that structural anomalies of the CT and MP may be the main anomaly in atrial flutter patients with grossly normal atria.[9],[13]

Intercaval block is anatomically and electro-physiologically based on the direction of fibers from CT and MP. The excitatory impulse may propagate unevenly in MP with heavily trabeculated muscle fibers. This framework of the muscular fascicles causes these patients to be more susceptible to severe arrhythmias.[14] Large MP ridges are thought to act as an innate basis of intra-atrial re-entry and lengthen the lives of reentrant wavefronts, resulting in “flutter-like” or “fibrillation-like” phenomenon, respectively, in separated canine tissue of the atria. The current research also exhibited notable muscle columns of MP in 4% of specimens. Radiofrequency catheter excision is arguably among the most prevalent treatment modality to treat atrial flutter. The morphology of the MP is relevant during the ablation operation because it poses an iatrogenic hazard to the myocardial damage, notably in Type 6 MP, Type B TS, and Type C TS. Siddiqui et al. reported the incidence of these clinically relevant variants, i. e., prominent muscular column (Type 6) MP as 8%, single trunk (Type B) TS as 55% and multiple trunk (Type C) TS as 25%.[7]

Recent researches have identified the role of CT' function in the atrial arrhythmias (flutter/fibrillation) process. Moreover, it is enticing to consider the possibility that anatomical aberration of the CT and MP is probably the main malformation in patients with atrial flutter and could account for the occurrence of atrial flutter even in the person with anatomically normal atria.[9],[12],[13]

Henceforth, Type 6 MP, Type B/Type C TS possessing a more complex arrangement of fibers and the propensity to sustain damage during cardiac catheterization, the current study intended to offer an overview of the gross morphological structure of the main muscle fascicles for the interventional surgeon.

  Conclusion Top

The anatomic architecture of CT and MP has practical consequences for arrhythmias and electrophysiology and proper cardiac conduction. With regard to interventional catheterization procedures, CT is a crucial anatomic landmark. The present research suggests that hearts with Type 6 MP and Type B/Type C TS, which have a more complicated pattern of fibers, are more susceptible to sustain injury during cardiac catheterization, the incidence of which is more than fifty percent. Possibilities are that the tip of the cardiac catheter to become caught behind the TS or one of the MP branches when performing a catheterization, resulting in atrial arrhythmia (fibrillation/flutter).


The authors sincerely thank those who donated their bodies to medical science so that anatomical research could be performed. Results from such a study can potentially increase humanity's overall knowledge, improving patient care. Therefore, these donors and their families deserve our highest gratitude.[15]

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Ho SY, Anderson RH, Sánchez-Quintana D. Gross structure of the atriums: More than an anatomic curiosity? Pacing Clin Electrophysiol 2002;25:342-50.  Back to cited text no. 1
Loukas M, Tubbs RS, Tongson JM, Polepalli S, Curry B, Jordan R, et al. The clinical anatomy of the crista terminalis, pectinate muscles and the teniae sagittalis. Ann Anat 2008;190:81-7.  Back to cited text no. 2
Moore KL, Persaud TV, Torchia MG. The Developing Human: Clinically Oriented Embryology. 10th ed. Philadelphia, PA: Elsevier; 2016. p. 371-80.  Back to cited text no. 3
D'Amato N, Pierfelice O, D'Agostino C. Crista terminalis bridge: A rare variant mimicking right atrial mass. Eur J Echocardiogr 2009;10:444-5.  Back to cited text no. 4
Gaudio C, Di Michele S, Cera M, Nguyen BL, Pannarale G, Alessandri N. Prominent crista terminalis mimicking a right atrial mixoma: Cardiac magnetic resonance aspects. Eur Rev Med Pharmacol Sci 2004;8:165-8.  Back to cited text no. 5
Salustri A, Bakir S, Sana A, Lange P, Al Mahmeed WA. Prominent crista terminalis mimicking a right atrial mass: Case report. Cardiovasc Ultrasound 2010;8:47.  Back to cited text no. 6
Siddiqui AU, Daimi SR, Gandhi KR, Siddiqui AT, Trivedi S, Sinha MB, et al. Crista terminalis, musculi pectinati, and taenia sagittalis: Anatomical observations and applied significance. ISRN Anat 2013;2013:803853.  Back to cited text no. 7
Seemann G, Höper C, Sachse FB, Dössel O, Holden AV, Zhang H. Heterogeneous three-dimensional anatomical and electrophysiological model of human atria. Philos Trans A Math Phys Eng Sci 2006;364:1465-81.  Back to cited text no. 8
Olgin JE, Kalman JM, Fitzpatrick AP, Lesh MD. Role of right atrial endocardial structures as barriers to conduction during human type I atrial flutter. Activation and entrainment mapping guided by intracardiac echocardiography. Circulation 1995;92:1839-48.  Back to cited text no. 9
Schumacher B, Jung W, Schmidt H, Fischenbeck C, Lewalter T, Hagendorff A, et al. Transverse conduction capabilities of the crista terminalis in patients with atrial flutter and atrial fibrillation. J Am Coll Cardiol 1999;34:363-73.  Back to cited text no. 10
Ortiz J, Niwano S, Abe H, Rudy Y, Johnson NJ, Waldo AL. Mapping the conversion of atrial flutter to atrial fibrillation and atrial fibrillation to atrial flutter. Insights into mechanisms. Circ Res 1994;74:882-94.  Back to cited text no. 11
Mizumaki K, Fujiki A, Nagasawa H, Nishida K, Sakabe M, Sakurai K, et al. Relation between transverse conduction capability and the anatomy of the crista terminalis in patients with atrial flutter and atrial fibrillation: Analysis by intracardiac echocardiography. Circ J 2002;66:1113-8.  Back to cited text no. 12
Ellis WS, SippensGroenewegen A, Auslander DM, Lesh MD. The role of the crista terminalis in atrial flutter and fibrillation: A computer modeling study. Ann Biomed Eng 2000;28:742-54.  Back to cited text no. 13
Wu TJ, Yashima M, Xie F, Athill CA, Kim YH, Fishbein MC, et al. Role of pectinate muscle bundles in the generation and maintenance of intra-atrial reentry: Potential implications for the mechanism of conversion between atrial fibrillation and atrial flutter. Circ Res 1998;83:448-62.  Back to cited text no. 14
Iwanaga J, Singh V, Ohtsuka A, Hwang Y, Kim HJ, Moryś J, et al. Acknowledging the use of human cadaveric tissues in research papers: Recommendations from anatomical journal editors. Clin Anat 2021;34:2-4.  Back to cited text no. 15


  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9]

  [Table 1], [Table 2]


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