International Journal of Anatomy and Physiology

International Journal of Anatomy and Physiology | Vol. 15, No. 9, September 2026 | pp. 221–232

DOI: 10.46882/2026/IJAP/000186

Article Type: Original Research Article

Title: Anatomical Relationship of the Deep Branch of the Ulnar Nerve to the Hook of Hamate: A High-Resolution Morphometric Cadaveric Study

Names of Authors: Pierre-Yves Dupont¹, Jean-Luc Moreau²

Authors’ Affiliations: ¹Laboratory of Anatomy, Faculty of Medicine, University of Lille, Lille, France; ²Department of Hand Surgery, University Hospital Center of Lille, Lille, France

Abstract:
Compression of the deep branch of the ulnar nerve (DBUN) within Guyon’s canal leads to isolated motor deficits, commonly resulting from hook of hamate fractures or ganglion cysts. This study established precise morphometric measurements of the DBUN’s pathway relative to the hook of hamate to optimize surgical safety zones. Fifty formaline-fixed human cadaveric hands (25 left, 25 right) were carefully dissected under magnification. The shortest distance from the radial border of the hook of hamate to the main trunk of the DBUN was determined using a digital caliper. The branching sequence to the hypothenar muscles, interossei, and musculus adductor pollicis was recorded. The DBUN orbited around the distal tip of the hook of hamate at an average distance of 3.4 ± 0.6 mm. In 76.0% of specimens, the nerve gave off its primary motor branch to the musculus opponens digiti minimi before crossing the hook, while in 24.0% the branching occurred directly adjacent to the hook. The mean diameter of the DBUN trunk at the hamate level was 1.82 ± 0.21 mm. No significant differences were found between left and right hands (p > 0.05). These quantitative parameters map a narrow iatrogenic danger zone, providing hand surgeons with specific boundaries to protect the ulnar motor trunk during hook excision or tunnel release.

Keywords: Ulnar Nerve, Guyon's Canal, Hook of Hamate, Morphometry, Hand Anatomy, Entrapment Neuropathy

Manuscript Timeline: Received: July 11, 2026; Revised: August 20, 2026; Accepted: September 03, 2026; Published: September 18, 2026

Citation: Dupont P.Y., & Moreau J.L. (2026). Anatomical Relationship of the Deep Branch of the Ulnar Nerve to the Hook of Hamate: A High-Resolution Morphometric Cadaveric Study. International Journal of Anatomy and Physiology, 15(9), 221–232. DOI: 10.46882/2026/IJAP/000186

International Journal of Anatomy and Physiology | Vol. 15, No. 9, September 2026 | pp. 209–220

DOI: 10.46882/2026/IJAP/000185

Article Type: Original Research Article

Title: Respiratory Muscle Electromyographic Adjustments and Ventilatory Kinetics During Incremental Hypercapnic Stimulation

Names of Authors: Liam O. O'Connor¹, Siobhan M. Gallagher²

Authors’ Affiliations: ¹School of Medicine, Physiology Section, University College Dublin, Dublin, Ireland; ²Department of Respiratory Physiology, Galway University Hospital, Galway, Ireland

Abstract:
The neural regulation of respiratory muscles adapts dynamically to rising carbon dioxide levels to stabilize arterial blood gases. This study characterized the recruitment patterns of primary and accessory respiratory muscles during incremental hypercapnic stimulation. Twenty-four healthy subjects (12 males, 12 females, aged 20 to 25 years) underwent a modified Read rebreathing protocol using a gas mixture of 7% CO2 and 93% O2 for 6 minutes. Surface electromyography (sEMG) recorded neural activation of the musculus diaphragm (intercostal spaces), musculus sternocleidomastoideus (SCM), and musculus rectus abdominis. Root mean square (RMS) values of sEMG were calculated and synchronized with ventilation parameters. At baseline (partial pressure of end-tidal CO2, PetCO2 = 38.4 ± 1.2 mmHg), diaphragmatic activity drove tidal ventilation while accessory muscle activity was minimal. When PetCO2 exceeded a threshold of 46.5 ± 1.8 mmHg, a significant exponential increase in diaphragmatic RMS activity was observed (p < 0.01). Recruitment of the SCM muscle rose sharply at PetCO2 levels above 52.0 ± 2.1 mmHg, showing a 4.2-fold increase in electrical activity at peak hypercapnia. Minute ventilation (Ve) correlated strongly with SCM activation (r = 0.84, p < 0.001) in the advanced stages of rebreathing. These electromyographic data demonstrate a tiered activation cascade within the respiratory musculature during hypercapnia, marking the precise chemical thresholds where accessory networks are recruited to support ventilatory demands.

Keywords: Electromyography, Hypercapnia, Diaphragm, Sternocleidomastoideus, Ventilatory Kinetics, Rebreathing

Manuscript Timeline: Received: July 08, 2026; Revised: August 18, 2026; Accepted: September 01, 2026; Published: September 16, 2026

Citation: O'Connor L.O., & Gallagher S.M. (2026). Respiratory Muscle Electromyographic Adjustments and Ventilatory Kinetics During Incremental Hypercapnic Stimulation. International Journal of Anatomy and Physiology, 15(9), 209–220. DOI: 10.46882/2026/IJAP/000185

International Journal of Anatomy and Physiology | Vol. 15, No. 9, September 2026 | pp. 197–208

DOI: 10.46882/2026/IJAP/000184

Article Type: Original Research Article

Title: Histomorphometric and Vascular Density Transformations of the Human Fallopian Tube Mucosa throughout the Menstrual Cycle

Names of Authors: Camila R. Silva¹, Mateo L. Fernandez²

Authors’ Affiliations: ¹Department of Anatomy, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo, Brazil; ²Department of Obstetrics and Gynecology, Faculty of Medicine, University of Buenos Aires, Buenos Aires, Argentina

Abstract:
The fallopian tube mucosa undergo delicate structural adjustments to facilitate gamete transport and fertilization. This study quantified changes in epithelial cell height, ciliation index, and microvascular density within the human fallopian tube during distinct phases of the menstrual cycle. Fallopian tube tissue samples were obtained from 48 premenopausal women (aged 28 to 44 years) undergoing elective benign total hysterectomy. Samples were categorized into follicular (n = 22) and luteal (n = 26) phases based on endometrial histology. Sections from the ampulla and isthmus were stained with Hematoxylin and Eosin (H&E) and CD31 immunohistochemistry for digital microvascular analysis. The mean epithelial height in the ampulla reached its peak during the late follicular phase (32.4 ± 2.1 μm) compared to the late luteal phase (21.5 ± 1.8 μm, p < 0.01). The ciliation index (percentage of ciliated cells) was significantly higher in the follicular phase than in the luteal phase (54.2% vs 41.8%, p < 0.05). CD31 immunostaining revealed that microvascular area density in the mucosal plicae was significantly elevated during the follicular phase (8.4 ± 1.1% vs 5.2 ± 0.7% in the luteal phase, p < 0.01). These results indicate that cyclical changes in ovarian steroids regulate mucosal structural remodeling and microvascular blood volume, maximizing anatomical support during the fertilization window.

Keywords: Fallopian Tube, Oviduct Mucosa, Histomorphometry, Cilia, Menstrual Cycle, CD31 Immunohistochemistry

Manuscript Timeline: Received: July 04, 2026; Revised: August 14, 2026; Accepted: August 29, 2026; Published: September 14, 2026

Citation: Silva C.R., & Fernandez M.L. (2026). Histomorphometric and Vascular Density Transformations of the Human Fallopian Tube Mucosa throughout the Menstrual Cycle. International Journal of Anatomy and Physiology, 15(9), 197–208. DOI: 10.46882/2026/IJAP/000184

International Journal of Anatomy and Physiology | Vol. 15, No. 9, September 2026 | pp. 185–196

DOI: 10.46882/2026/IJAP/000183

Article Type: Original Research Article

Title: Variations in the Configuration of the Circle of Willis in an East Asian Population: A 3D Magnetic Resonance Angiography Study

Names of Authors: Kenji Sato¹, Takashi Abe²

Authors’ Affiliations: ¹Department of Anatomy and Neurobiology, Kyoto University Graduate School of Medicine, Kyoto, Japan; ²Department of Radiology, Tokyo Medical and Dental University, Tokyo, Japan

Abstract:
The anatomical completeness of the Circle of Willis (CoW) determines collateral blood flow configuration during ischemic cerebrovascular events. This study assessed the prevalence of classic and variant CoW architectures in a large cohort using three-dimensional time-of-flight magnetic resonance angiography (3D-TOF-MRA). Brain MRA scans of 620 healthy adult subjects (aged 20 to 75 years) were retrospectively examined. A complete symmetrical CoW was observed in only 42.3% of the cases (n = 262). Variant configurations were identified in 57.7% of the subjects (n = 358). The most common variant in the anterior circulation was hypoplasia or absence of the anterior communicating artery (ACoA), which occurred in 11.8% of individuals. In the posterior circulation, a fetal-type posterior cerebral artery (fPCA)—where the PCA originates directly from the internal carotid artery—was observed unilaterally in 14.5% and bilaterally in 4.8% of scans. Hypoplasia of the pre-communicating (P1) segment of the PCA was strongly associated with fPCA presence (p < 0.001). Asymmetry and hypoplasia were significantly more prevalent in the posterior circulation (38.2%) than in the anterior circulation (19.5%). These findings show that a complete CoW is absent in more than half of this East Asian sub-population, highlighting the value of non-invasive MRA screening to evaluate vascular resilience before neurosurgical or interventional neuroradiological procedures.

Keywords: Circle of Willis, Anatomical Variations, Magnetic Resonance Angiography, Fetal Posterior Cerebral artery, Collateral Circulation

Manuscript Timeline: Received: July 01, 2026; Revised: August 12, 2026; Accepted: August 28, 2026; Published: September 11, 2026

Citation: Sato K., & Abe T. (2026). Variations in the Configuration of the Circle of Willis in an East Asian Population: A 3D Magnetic Resonance Angiography Study. International Journal of Anatomy and Physiology, 15(9), 185–196. DOI: 10.46882/2026/IJAP/000183

International Journal of Anatomy and Physiology | Vol. 15, No. 9, September 2026 | pp. 173–184

DOI: 10.46882/2026/IJAP/000182

Article Type: Original Research Article

Title: Histological Changes and Oxidative Stress Biomarkers in the Testes of Adult Rats Exposed to Food-Grade Titanium Dioxide Nanoparticles

Names of Authors: Ahmed M. Al-Ghamdi¹, Youssef S. Ramadan²

Authors’ Affiliations: ¹Department of Anatomy, College of Medicine, King Saud University, Riyadh, Saudi Arabia; ²Department of Medical Physiology, Faculty of Medicine, Cairo University, Cairo, Egypt

Abstract:
Titanium dioxide nanoparticles (TiO2-NPs) are widely utilized as whitening agents in food, cosmetics, and pharmaceuticals, yet their reproductive safety remains controversial. This study evaluated the structural damage and oxidative stress within the testicular tissues of Wistar rats following sub-chronic oral exposure to food-grade TiO2-NPs. Thirty-cc adult male rats were divided into three equal groups (n = 12). Group I received distilled water; Groups II and III received 50 mg/kg and 100 mg/kg body weight of TiO2-NPs daily via oral gavage for 60 consecutive days. Serum testosterone levels were quantified, and right testes were processed for histological assessment using Hematoxylin and Eosin (H&E). Left testes were homogenized to measure malondialdehyde (MDA) and superoxide dismutase (SOD) activity. The 100 mg/kg group showed a significant decrease in serum testosterone levels (2.14 ± 0.32 ng/mL vs 5.68 ± 0.45 ng/mL in controls, p < 0.01). Histological sections from treated rats revealed severe disorganization of the seminiferous epithelium, loss of spermatogenic cells, and detachment of the basement membrane. The mean seminiferous tubule diameter decreased significantly by 22.4% (p < 0.01). Biochemical analysis revealed a 2.4-fold increase in MDA concentration, coupled with a 45.1% reduction in SOD activity. These data suggest that sub-chronic exposure to food-grade TiO2-NPs triggers severe testicular microstructure degeneration, driven by elevated oxidative stress and compromised antioxidant pathways.

Keywords: Titanium Dioxide Nanoparticles, Testicular Histology, Spermatogenesis, Oxidative Stress, Testosterone, Wistar Rats

Manuscript Timeline: Received: June 28, 2026; Revised: August 10, 2026; Accepted: August 25, 2026; Published: September 09, 2026

Citation: Al-Ghamdi M.M., & Ramadan Y.S. (2026). Histological Changes and Oxidative Stress Biomarkers in the Testes of Adult Rats Exposed to Food-Grade Titanium Dioxide Nanoparticles. International Journal of Anatomy and Physiology, 15(9), 173–184. DOI: 10.46882/2026/IJAP/000182

International Journal of Anatomy and Physiology | Vol. 15, No. 9, September 2026 | pp. 161–172

DOI: 10.46882/2026/IJAP/000181

Article Type: Original Research Article

Title: High-Resolution Ultrasound Mapping of the Superficial Peroneal Nerve in the Distal Leg: An Anatomical Guide for Surgical Approaches

Names of Authors: Min-Ji Kim¹, Dong-Hyun Seo²

Authors’ Affiliations: ¹Department of Anatomy, Yonsei University College of Medicine, Seoul, South Korea; ²Department of Orthopedic Surgery, Severance Hospital, Seoul, South Korea

Abstract:
Iatrogenic injury to the superficial peroneal nerve (SPN) frequently complicates lateral malleolar fixations, ankle arthroscopies, and compartment decompressions. This study utilized high-resolution ultrasound (HRUS) to precisely trace the exit point and branching patterns of the SPN relative to bony landmarks. One hundred healthy lower limbs from fifty volunteers (25 males, 25 females) were scanned using a 15-MHz linear transducer. The point where the SPN pierced the deep crural fascia was measured relative to the tip of the lateral malleolus. The nerve's bifurcation into the medial dorsal cutaneous nerve (MDCN) and intermediate dorsal cutaneous nerve (IDCN) was mapped. The SPN pierced the crural fascia at a mean distance of 7.4 ± 1.2 cm proximal to the lateral malleolus. In 84.0% of limbs, the nerve emerged in the anterior intermuscular septum (Type Type I), while in 16.0% it pierced the peroneus longus belly (Type II). Bifurcation into the MDCN and IDCN occurred subfascially in 28.0% of cases and extrafascially in 72.0%. The mean distance from the bifurcation to the lateral malleolus tip was 4.8 ± 0.9 cm. No significant correlation was noted between side or gender and nerve position (p > 0.05). These ultrasonic measurements offer reliable anatomical boundaries, allowing surgeons to non-invasively locate the SPN and mitigate nerve injury risk during distal leg procedures.

Keywords: Superficial Peroneal Nerve, High-Resolution Ultrasound, Anatomical Variations, Crural Fascia, Lateral Malleolus

Manuscript Timeline: Received: June 25, 2026; Revised: August 06, 2026; Accepted: August 23, 2026; Published: September 07, 2026

Citation: Kim M.J., & Seo D.H. (2026). High-Resolution Ultrasound Mapping of the Superficial Peroneal Nerve in the Distal Leg: An Anatomical Guide for Surgical Approaches. International Journal of Anatomy and Physiology, 15(9), 161–172. DOI: 10.46882/2026/IJAP/000181