International Journal of Anatomy and Physiology

International Journal of Anatomy and Physiology | Vol. 15, No. 9, September 2026 | pp. 64–72

DOI: 10.46882/2026/IJAP/001008

Research Article

Title: Spatial Distribution and Quantitative Density of Pyramidal Neurons in the Human Prefrontal Cortex Area 9: An Autopsy Study

Names of Authors: D. R. Novak¹, S. L. Bourassa², A. M. El-M基础³*

Authors’ Affiliations:
¹ Department of Anatomy, Charles University Second Faculty of Medicine, Prague, Czech Republic.
² Department of Neuropathology, McGill University, Montreal, Quebec, Canada.
³ Department of Anatomy and Embryology, Faculty of Medicine, Cairo University, Cairo, Egypt.

Abstract:
Pyramidal neurons in cortical layer III and V of the human prefrontal cortex (Brodmann Area 9) serve as the structural framework for higher cognitive executive functions, working memory, and goal-directed behaviors. Alterations in their cellular density or spatial organization are associated with neurodevelopmental and psychiatric disorders. This post-mortem study quantified the density and spatial distribution of pyramidal neurons within Area 9 of neurotypical adults. Brain tissues were obtained during autopsies of 18 individuals (9 males, 9 females; mean age 44.2 ± 6.8 years) with no history of neurological disorders. Coronal sections (20 μm thick) were stained with Nissl and analyzed via optical fractionator stereological methods. Pyramidal neurons were identified by their characteristic triangular somas and prominent apical dendrites. The mean neuronal density in cortical layer III was 24,500 ± 1,850 cells/mm³, which was significantly higher than the density observed in layer V (16,200 ± 1,420 cells/mm³; p < 0.01). No significant differences in density were found between the left and right hemispheres or between male and female brains. Spatial distribution analysis using the nearest-neighbor distance method revealed a regular, non-random columnar grouping pattern of pyramidal cells in layer III. These normative quantitative data regarding prefrontal cortical architecture provide a reliable anatomical reference baseline for future histopathological studies investigating psychiatric conditions like schizophrenia and major depressive disorder.

Keywords: Prefrontal cortex, Pyramidal neurons, Stereology, Brodmann Area 9, Neuronal density.

Manuscript Timeline: Received: May 15, 2026; Revised: July 19, 2026; Accepted: August 19, 2026; Published: September 29, 2026.

Citation: Novak DR, Bourassa SL, El-M基础 AM. Spatial Distribution and Quantitative Density of Pyramidal Neurons in the Human Prefrontal Cortex Area 9: An Autopsy Study. International Journal of Anatomy and Physiology. 2026; 15(9): 64–72. doi:10.46882/2026/IJAP/001008

International Journal of Anatomy and Physiology | Vol. 15, No. 9, September 2026 | pp. 55–63

DOI: 10.46882/2026/IJAP/001007

Research Article

Title: Morphometric Analysis of the Human Carotid Bifurcation and Intimal-Medial Thickness Using High-Resolution Ultrasonography

Names of Authors: M. E. Larsen¹, J. A. Nkosi², C. H. Choi³*

Authors’ Affiliations:
¹ Department of Clinical Medicine, Aarhus University, Aarhus, Denmark.
² Department of Human Anatomy, University of the Witwatersrand, Johannesburg, South Africa.
³ Department of Anatomy, Yonsei University College of Medicine, Seoul, South Korea.

Abstract:
The geometric configuration of the carotid bifurcation influences local hemodynamic patterns, predisposing specific areas to atherosclerotic plaque development. This study evaluated the relationship between the geometric dimensions of the carotid bifurcation and carotid intima-media thickness (CIMT) in a healthy adult cohort. High-resolution B-mode ultrasonography was performed on 250 healthy volunteers (aged 20–60 years) to measure the diameters of the common carotid artery (CCA), internal carotid artery (ICA), and external carotid artery (ECA). The carotid bifurcation angle and the CIMT of the posterior CCA wall were quantified. The mean bifurcation angle across the cohort was 54.2° ± 8.6°. A statistically significant positive correlation was identified between wider bifurcation angles (>60°) and higher mean CIMT values (0.78 ± 0.11 mm vs. 0.62 ± 0.08 mm in angles <50°; p < 0.01). The ratio of the combined cross-sectional area of the ICA and ECA to that of the CCA (area ratio) averaged 1.15 ± 0.14. Lower area ratios (<1.0) correlated with elevated ICA intimal thickness, likely due to altered wall shear stress. Stepwise multiple regression analysis confirmed that the carotid bifurcation angle is an independent predictor of regional intima-media thickening, even after adjusting for age and gender. Mapping these anatomical dimensions using non-invasive ultrasound assists in identifying individuals with geometrically unfavorable vascular structures who may have a higher risk of developing carotid vascular diseases.

Keywords: Carotid bifurcation, Intima-media thickness, Ultrasonography, Hemodynamics, Carotid artery.

Manuscript Timeline: Received: June 22, 2026; Revised: August 01, 2026; Accepted: August 22, 2026; Published: September 26, 2026.

Citation: Larsen ME, Nkosi JA, Choi CH. Morphometric Analysis of the Human Carotid Bifurcation and Intimal-Medial Thickness Using High-Resolution Ultrasonography. International Journal of Anatomy and Physiology. 2026; 15(9): 55–63. doi:10.46882/2026/IJAP/001007

International Journal of Anatomy and Physiology | Vol. 15, No. 9, September 2026 | pp. 37–45

DOI: 10.46882/2026/IJAP/001005

Research Article

Title: Electromyographic and Anatomical Evaluation of the Accessory Soleus Muscle and Its Clinical Implications

Names of Authors: F. G. Santos¹, H. I. Takahashi², K. M. O’Connor³*

Authors’ Affiliations:
¹ Department of Morphology, Federal University of São Paulo, São Paulo, Brazil.
² Department of Anatomy, Osaka University Graduate School of Medicine, Osaka, Japan.
³ Department of Physical Therapy, Marquette University, Milwaukee, Wisconsin, USA.

Abstract:
The accessory soleus muscle is a rare anatomical variant located in the deep posterior compartment of the leg, which can present as a soft tissue mass in the posteromedial ankle region. It can cause chronic pain, swelling, or tarsal tunnel syndrome during physical activity. This study combined cadaveric dissection and surface electromyography (sEMG) to characterize the morphology and functional behavior of this muscle variant. Dissection of 80 formalin-fixed lower limbs revealed an accessory soleus muscle in 3 extremities (3.75%). All instances originated from the anterior surface of the soleus muscle and inserted into the medial surface of the calcaneus via a distinct tendon. In the clinical phase, five symptomatic athletes diagnosed with an accessory soleus via Magnetic Resonance Imaging (MRI) underwent sEMG evaluation during various ankle movements. Muscle activity was recorded during plantarflexion, dorsiflexion, inversion, and eversion, and compared against ten healthy controls. The sEMG findings demonstrated that the accessory soleus muscle displayed a high root-mean-square (RMS) voltage during sustained isometric plantarflexion, contributing significantly to joint torque but exhibiting premature fatigue compared to the normal soleus (p < 0.05). The co-activation of this anomalous muscle during forced ankle movements suggests that its hypertrophy and structural location can limit space in the posterior compartment, compressing the tibial nerve. Clinicians should consider this variant in cases of exertional ankle pain.

Keywords: Accessory soleus muscle, Anatomical variant, Dissection, Surface electromyography, Tarsal tunnel syndrome.

Manuscript Timeline: Received: June 03, 2026; Revised: July 15, 2026; Accepted: August 10, 2026; Published: September 19, 2026.

Citation: Santos FG, Takahashi HI, O’Connor KM. Electromyographic and Anatomical Evaluation of the Accessory Soleus Muscle and Its Clinical Implications. International Journal of Anatomy and Physiology. 2026; 15(9): 37–45. doi:10.46882/2026/IJAP/001005

International Journal of Anatomy and Physiology | Vol. 15, No. 9, September 2026 | pp. 19–27

DOI: 10.46882/2026/IJAP/001003

Review Article

Title: Histological and Physiological Adaptations of the Human Myocardium in Response to Chronic Endurance Exercise

Names of Authors: G. R. Müller¹, A. L. Rossi²*

Authors’ Affiliations:
¹ Institute of Cardiology and Sports Medicine, German Sport University Cologne, Cologne, Germany.
² Department of Physiology, University of Bologna, Bologna, Italy.

Abstract:
Chronic endurance exercise triggers extensive physiological and anatomical remodeling of the human heart, collectively referred to as the athlete’s heart. This review synthesizes current literature on the underlying histological, molecular, and physiological adaptations of the myocardium in response to prolonged aerobic training. Endurance training induces eccentric hypertrophy, characterized by a proportional increase in left ventricular chamber size and wall thickness. At the cellular level, cardiomyocytes undergo elongation through the serial addition of sarcomeres, accompanied by a balanced increase in myofibrillar density and mitochondrial biogenesis. Physiological changes include enhanced vagal tone, leading to resting bradycardia and an increased stroke volume via the Frank-Starling mechanism. Myocardial capillary density increases to match the structural hypertrophy, ensuring a balanced myocardial oxygen supply and preventing tissue ischemia. Furthermore, molecular signaling pathways involving insulin-like growth factor 1 (IGF-1) and phosphoinositide 3-kinase (PI3K) are up-regulated, steering physiological hypertrophy away from pathological pathways driven by angiotensin II. Myocardial interstitial collagen content remains stable or undergoes organized remodeling, avoiding the diffuse fibrosis seen in hypertensive heart disease. Understanding these adaptations is vital to distinguishing benign physiological remodeling from cardiomyopathy, ensuring accurate screening and prevention of sudden cardiac death in elite athletes.

Keywords: Myocardium, Cardiomyocyte, Eccentric hypertrophy, Endurance exercise, Physiological adaptation.

Manuscript Timeline: Received: April 15, 2026; Revised: June 30, 2026; Accepted: August 02, 2026; Published: September 12, 2026.

Citation: Müller GR, Rossi AL. Histological and Physiological Adaptations of the Human Myocardium in Response to Chronic Endurance Exercise. International Journal of Anatomy and Physiology. 2026; 15(9): 19–27. doi:10.46882/2026/IJAP/001003

International Journal of Anatomy and Physiology | Vol. 15, No. 9, September 2026 | pp. 10–18

DOI: 10.46882/2026/IJAP/001002

Research Article

Title: Variations in the Origin and Branching Pattern of the Celiac Trunk Evaluated by Computed Tomography Angiography

Names of Authors: L. K. Chen¹, S. M. Patel², R. E. Dubois³*

Authors’ Affiliations:
¹ Department of Anatomy, National Taiwan University College of Medicine, Taipei, Taiwan.
² Department of Radiology, All India Institute of Medical Sciences, New Delhi, India.
Department of Anatomy, Faculty of Medicine, Sorbonne University, Paris, France.

Abstract:
Anatomical variations of the celiac trunk are frequent and clinically relevant for surgeons performing liver transplantations, gastrectomies, and transcatheter arterial chemoembolization. This study evaluated the variations in the origin, length, diameter, and branching patterns of the celiac trunk using computed tomography (CT) angiography. Contrast-enhanced abdominal CT scans of 400 adult patients (210 males, 190 females) were retrospectively reviewed. The classic trifurcation into the splenic, common hepatic, and left gastric arteries (Haller's triad) was observed in 86.5% of cases. Variations were recorded in 13.5% of the subjects. The most common variation was a hepatosplenic trunk (5.2%), where the left gastric artery arose directly from the abdominal aorta. A celiac-mesenteric trunk, where the celiac trunk and superior mesenteric artery shared a common origin, was found in 1.8% of cases. The mean length of the celiac trunk was 12.4 ± 3.2 mm, and the mean diameter was 6.8 ± 1.1 mm. Statistically significant differences in diameter were noted between males and females (p < 0.05). The celiac trunk originated at the level of the T12-L1 intervertebral disc in 78% of individuals. This study confirms that while the classic trifurcation remains dominant, significant vascular variations exist within the study population. Detailed preoperative CT angiography mapping is highly recommended to prevent inadvertent vascular ligation or hemorrhagic complications during upper abdominal surgeries.

Keywords: Celiac trunk, Hepatosplenic trunk, Computed tomography angiography, Vascular variation, Abdominal aorta.

Manuscript Timeline: Received: May 20, 2026; Revised: July 11, 2026; Accepted: August 11, 2026; Published: September 8, 2026.

Citation: Chen LK, Patel SM, Dubois RE. Variations in the Origin and Branching Pattern of the Celiac Trunk Evaluated by Computed Tomography Angiography. International Journal of Anatomy and Physiology. 2026; 15(9): 10–18. doi:10.46882/2026/IJAP/001002

International Journal of Anatomy and Physiology | Vol. 15, No. 9, September 2026 | pp. 1–9

DOI: 10.46882/2026/IJAP/000211

Article Type: Research Article

Title: Immunophysiological Response and Microstructural Alterations in Hepatic and Renal Tissues of Mus musculus Following Exposure to Bacterial Endotoxins

Names of Authors: Subbiah Poopathi¹*, S. Abidha¹

Authors’ Affiliations:
¹Unit of Microbiology and Immunology, Vector Control Research Centre (Indian Council of Medical Research), Medical Complex, Indira Nagar, Puducherry - 605006, India.

Abstract:
Bacterial endotoxins synthesized by insecticidal microorganisms exert distinct cellular stresses when introduced into mammalian models. This study evaluated the systematic immunophysiological responses and accompanying microstructural changes in the hepatic and renal systems of Swiss albino mice (Mus musculus) following sub-acute exposure to isolated crystal endotoxins. A total of 32 mice were allocated into four experimental groups, receiving varied concentrations (0.0, 2.5, 5.0, and 10.0 mg/kg body weight) via intraperitoneal injection over 14 consecutive days. Serum biomarkers, hematological profiles, and organ histopathology were evaluated. Exposure to the highest concentration induced significant physiological stress, indicated by a 2.4-fold increase in serum alanine aminotransferase (ALT) and a 1.8-fold rise in blood urea nitrogen (BUN) levels (p < 0.01). Histological examination of hepatic tissue sections revealed prominent sinusoidal congestion, vacuolar degeneration of hepatocytes, and focal infiltration of mononuclear leukocytes. In renal tissues, glomerular shrinkage, widening of Bowman's space, and acute tubular necrosis were documented. Furthermore, differential leukocyte counts revealed a marked shift toward neutrophilia (68.4 ± 4.2% vs 22.1 ± 1.8% in controls), highlighting a robust acute-phase inflammatory reaction. These findings indicate that while insecticidal bacterial endotoxins demonstrate high specificity toward target vectors, elevated systemic exposure triggers distinct pathological transformations and physiological imbalances in mammalian metabolic organs. This highlights the importance of thorough biosafety evaluations during the formulation of microbial vector control agents.

Keywords: Endotoxins, Hepatotoxicity, Nephrotoxicity, Cellular physiology, Histopathology, Mus musculus.

Manuscript Timeline: Received: July 18, 2026; Revised: August 20, 2026; Accepted: September 02, 2026; Published: September 29, 2026.

Citation: Poopathi, Q. S., & Abidha, S. (2026). Immunophysiological Response and Microstructural Alterations in Hepatic and Renal Tissues of Mus musculus Following Exposure to Bacterial Endotoxins. International Journal of Anatomy and Physiology, 14(9), 1–9.