International Journal of Anatomy and Physiology

International Journal of Anatomy and Physiology | Vol. 15, No. 9, September 2026 | pp. 281–292

DOI: 10.46882/2026/IJAP/000191

Article Type: Case Report

Title: Bilateral Presence of the Musculus Sternalis: An Uncommon Muscular Variant Discovered on Anterior Chest Wall Dissection

Names of Authors: Arthur J. Pendelton¹, Beatrice C. Vance²

Authors’ Affiliations: ¹Department of Anatomical Sciences, University of Manchester, Manchester, United Kingdom; ²Department of Plastic and Reconstructive Surgery, Manchester Royal Infirmary, Manchester, United Kingdom

Abstract:
The musculus sternalis is a rare anatomical variant of the anterior chest wall muscle layer, often misidentified as a malignant mass on routine screening mammograms or chest computed tomography scans. During a standard academic dissection of an 82-year-old female cadaver, a rare case of a well-developed, bilateral musculus sternalis was identified. The muscles were located superficial to the fascia of the pectoralis major muscle, running parallel to the lateral margins of the sternum. On the right side, the muscle bundle measured 12.4 cm in length and 1.8 cm in width, originating from the sheath of the rectus abdominis muscle and inserting into the sternal angle near the sternocleidomastoid tendon. On the left side, the muscle was slightly smaller, measuring 10.8 cm by 1.4 cm, with similar attachments. Both variant muscle strips were innervated by branches of the anterior thoracic nerves (medial and lateral pectoral nerves), suggesting a developmental embryological origin linked to the pectoral muscle mass. No other muscular anomalies were observed in the specimen. This case report highlights a classic anatomical trap for radiologists and surgeons, noting that awareness of this variant prevents false-positive tumor diagnoses and assists in muscle flap designs during reconstructive breast surgery.

Keywords: Sternalis Muscle, Pectoralis Major, Anatomical Variant, Mammography, Chest Wall Anatomy

Manuscript Timeline: Received: July 25, 2026; Revised: August 31, 2026; Accepted: September 14, 2026; Published: September 30, 2026

Citation: Pendelton J.A., & Vance B.C. (2026). Bilateral Presence of the Musculus Sternalis: An Uncommon Muscular Variant Discovered on Anterior Chest Wall Dissection. International Journal of Anatomy and Physiology, 15(9), 281–292. DOI: 10.46882/2026/IJAP/000191

International Journal of Anatomy and Physiology | Vol. 15, No. 9, September 2026 | pp. 293–304

DOI: 10.46882/2026/IJAP/000192

Article Type: Original Research Article

Title: Morphometric Study of the Human Bicipital Groove and its Clinical Implications in Shoulder Impingement Syndromes

Names of Authors: Chukwudi I. Amadi¹, Oluwaseun A. Olatunji²

Authors’ Affiliations: ¹Department of Anatomy, College of Medicine, University of Lagos, Lagos, Nigeria; ²Department of Physiology, Faculty of Basic Medical Sciences, Olabisi Onabanjo University, Shagamu, Nigeria

Abstract:
The bicipital groove of the humerus houses the long head of the biceps brachii tendon, a structure frequently implicated in chronic shoulder pain and instability. This study aimed to determine the morphometric characteristics of the bicipital groove within an African population to understand structural predispositions to tendon disease. Eighty dry human humeri (40 right and 40 left) of unknown sex were examined. Digital vernier calipers and a goniometer were used to measure the length, width, depth, and medial wall angle of the groove. The mean length of the groove was 52.4 ± 3.8 mm, the mean width was 10.2 ± 1.4 mm, and the mean depth was 4.8 ± 0.6 mm. The average medial wall angle was 48.5° ± 5.2°. Supratuberculous ridges of Meyer were identified in 18.5% of the specimens, which significantly reduced the effective depth of the proximal groove. A shallow groove depth (less than 3.0 mm) combined with a wide wall angle was strongly associated with a higher likelihood of long head biceps tendon subluxation. Statistical analysis showed no significant variations between right and left sides (p > 0.05). These quantitative parameters provide essential baseline dimensions for shoulder arthroplasty design and guide orthopaedic surgeons in managing biceps tendon pathologies and subacromial impingement syndromes.

Keywords: Bicipital Groove, Humerus, Biceps Tendon, Morphometry, Shoulder Impingement, Anatomical Variations

Manuscript Timeline: Received: July 24, 2026; Revised: September 02, 2026; Accepted: September 15, 2026; Published: September 30, 2026

Citation: Amadi C.I., & Olatunji O.A. (2026). Morphometric Study of the Human Bicipital Groove and its Clinical Implications in Shoulder Impingement Syndromes. International Journal of Anatomy and Physiology, 15(9), 293–304. DOI: 10.46882/2026/IJAP/000192

International Journal of Anatomy and Physiology | Vol. 15, No. 9, September 2026 | pp. 269–280

DOI: 10.46882/2026/IJAP/000190

Article Type: Original Research Article

Title: Variations in the Branching Pattern of the Human External Carotid Artery Within a Polish Sub-Population

Names of Authors: Janusz K. Kowalski¹, Agnieszka M. Wiśniewska²

Authors’ Affiliations: ¹Department of Anatomy, Jagiellonian University Medical College, Kraków, Poland; ²Department of Anatomy and Embryology, Medical University of Gdańsk, Gdańsk, Poland

Abstract:
The external carotid artery (ECA) exhibits rich branching variations that complicate radical neck dissections, carotid endarterectomies, and transcatheter embolizations. This study categorized the branching sequences and anatomical landmarks of the ECA within a Polish population group. One hundred lower neck specimens from fifty adult cadavers were examined using traditional dissection methods. The origin level of the ECA relative to the thyroid cartilage was identified, and the prevalence of common trunks, such as the linguofacial and thyrolingual trunks, was assessed. The bifurcation of the common carotid artery occurred at the level of the upper border of the thyroid cartilage in 64.0% of cases. A high bifurcation (above the hyoid bone) was observed in 28.0%, while a low origin occurred in 8.0% of specimens. The superior thyroid, lingual, and facial arteries arose as separate branches in 72.0% of cases. A linguofacial trunk was identified in 18.0% of limbs, whereas a thyrolingual trunk appeared in 6.0%. A rare common thyrolinguofacial trunk was documented in 4.0% of the cases. These anatomical distributions confirm that variations in the proximal branches of the ECA are highly prevalent, emphasizing the need for meticulous vascular mapping prior to plastic reconstruction or oncological resections in the anterior neck.

Keywords: External Carotid Artery, Anatomical Variations, Linguofacial Trunk, Carotid Bifurcation, Cadaveric Dissection

Manuscript Timeline: Received: July 22, 2026; Revised: August 29, 2026; Accepted: September 11, 2026; Published: September 28, 2026

Citation: Kowalski J.K., & Wiśniewska A.M. (2026). Variations in the Branching Pattern of the Human External Carotid Artery Within a Polish Sub-Population. International Journal of Anatomy and Physiology, 15(9), 269–280. DOI: 10.46882/2026/IJAP/000190

International Journal of Anatomy and Physiology | Vol. 15, No. 9, September 2026 | pp. 257–268

DOI: 10.46882/2026/IJAP/000189

Article Type: Original Research Article

Title: Histomorphometric Profile of the Human Sural Nerve: Evaluating Nerve Fiber Density and Aging Alterations

Names of Authors: Ananth R. Subramanian¹, Meenakshi S. Sundaram²

Authors’ Affiliations: ¹Department of Anatomy, Madras Medical College, Chennai, India; ²Department of Physiology, Jawaharlal Institute of Postgraduate Medical Education and Research, Puducherry, India

Abstract:
The sural nerve is frequently utilized for autologous nerve grafting and diagnostic biopsies, making baseline population data on its fiber microarchitecture crucial. This study analyzed the histomorphometric profile and age-related changes in the human sural nerve. Sural nerve specimens were harvested from 36 post-mortem donors, categorized into a Young cohort (aged 18 to 35 years, n = 18) and an Elderly cohort (aged 60 to 78 years, n = 18). Cross-sections were processed, embedded in araldite, stained with Toluidine Blue, and evaluated using digital image software. The young cohort demonstrated an average total fascicular area of 0.84 ± 0.11 mm², containing a mean myelinated nerve fiber density of 8450 ± 620 fibers/mm². In contrast, the elderly cohort exhibited a significant reduction in fiber density (5620 ± 410 fibers/mm², p < 0.001), indicating a loss of myelinated axons over time. The thickness of the myelin sheath decreased significantly by 26.4% in the older group (p < 0.01), with a corresponding increase in the g-ratio from 0.62 ± 0.03 to 0.71 ± 0.04. Furthermore, endoneurial connective tissue area expanded by 35.8% in elderly specimens, pointing to age-dependent interstitial fibrosis. These quantitative data define distinct structural declines in axonal preservation, providing critical reference points for peripheral neuropathology diagnostics and reconstructive nerve surgeries.

Keywords: Sural Nerve, Histomorphometry, Myelinated Axons, Myelin Sheath, Aging, Post-Mortem

Manuscript Timeline: Received: July 20, 2026; Revised: August 27, 2026; Accepted: September 10, 2026; Published: September 25, 2026

Citation: Subramanian A.R., & Sundaram M.S. (2026). Histomorphometric Profile of the Human Sural Nerve: Evaluating Nerve Fiber Density and Aging Alterations. International Journal of Anatomy and Physiology, 15(9), 257–268. DOI: 10.46882/2026/IJAP/000189

mInternational Journal of Anatomy and Physiology | Vol. 15, No. 9, September 2026 | pp. 245–256

DOI: 10.46882/2026/IJAP/000188

Article Type: Review Article

Title: Functional Anatomy and Molecular Pathways Governing Hypoxic Pulmonary Vasoconstriction: A Review of Cellular Feedback Loops

Names of Authors: Dmitry V. Ivanov¹, Svetlana A. Petrova²

Authors’ Affiliations: ¹Department of Human Anatomy, I.M. Sechenov First Moscow State Medical University, Moscow, Russia; ²Research Institute of Human Physiology, Saint Petersburg State University, Saint Petersburg, Russia

Abstract:
Hypoxic pulmonary vasoconstriction (HPV) is a highly specialized local autoregulatory mechanism that shunts blood flow from poorly ventilated segments of the lung toward well-oxygenated zones, thereby optimizing ventilation-perfusion matching. This review examines the complex functional anatomy of pulmonary smooth muscle cells (PASMCs) and the intracellular signaling pathways that trigger HPV. The unique structural composition of pre-capillary pulmonary arteries, which display high expression levels of oxygen-sensing proteins, is central to this mechanism. The primary sensor involves mitochondrial complex III, which alters reactive oxygen species (ROS) output in response to drops in alveolar oxygen tension (PAO2 < 60 mmHg). Alterations in ROS generation suppress voltage-gated potassium channels (KV1.5 and KV2.1) in the PASMC sarcolemma. This suppression induces membrane depolarization, which subsequently opens L-type voltage-gated calcium channels (VGCCs), driving a rapid influx of extracellular Ca2+. Concurrently, calcium sensitization via the RhoA/Rho-kinase (ROCK) signaling loop maintains prolonged contraction without requiring high intracellular calcium levels. Disruptions within these pathways contribute to the development of chronic hypoxic pulmonary hypertension. Analyzing these molecular dynamics illuminates targeted pharmacological windows, guiding the production of selective pulmonary vasodilators for neonatal and adult respiratory distress syndromes.

Keywords: Hypoxic Pulmonary Vasoconstriction, Pulmonary Smooth Muscle, Calcium Channels, Potassium Channels, Rho-Kinase, Mitochondria

Manuscript Timeline: Received: July 18, 2026; Revised: August 25, 2026; Accepted: September 08, 2026; Published: September 23, 2026

Citation: Ivanov D.V., & Petrova S.A. (2026). Functional Anatomy and Molecular Pathways Governing Hypoxic Pulmonary Vasoconstriction: A Review of Cellular Feedback Loops. International Journal of Anatomy and Physiology, 15(9), 245–256. DOI: 10.46882/2026/IJAP/000188

International Journal of Anatomy and Physiology | Vol. 15, No. 9, September 2026 | pp. 233–244

DOI: 10.46882/2026/IJAP/000187

Article Type: Original Research Article

Title: Gastroprotective Mechanisms of Garcinia kola Seed Extract Against Indomethacin-Induced Gastric Ulceration in Rats

Names of Authors: Olumide A. Adefegha¹, Blessing I. Nwosu²

Authors’ Affiliations: ¹Department of Physiology, College of Medicine, University of Ibadan, Ibadan, Nigeria; ²Department of Anatomy, Faculty of Basic Medical Sciences, Delta State University, Abraka, Nigeria

Abstract:
Non-steroidal anti-inflammatory drugs (NSAIDs) such as indomethacin frequently induce mucosal erosions due to prostaglandin depletion and oxidative injury. This study investigated the gastroprotective mechanisms of Garcinia kola seed extract (GKSE) against indomethacin-induced gastric ulcers in Wistar rats. Thirty adult rats were randomized into five groups (n = 6). Group I (normal control) received saline; Group II (ulcer control) received 40 mg/kg indomethacin orally; Group III received misoprostol (20 μg/kg); Groups IV and V were pretreated with GKSE at 250 mg/kg and 500 mg/kg for 14 days prior to indomethacin administration. Gastric secretions were collected to analyze pH and total acidity, and macroscopic mucosal lesions were scored to compute the ulcer index (UI). Indomethacin induced severe mucosal necrosis with a UI of 5.82 ± 0.44 in Group II. Pretreatment with 500 mg/kg GKSE significantly decreased the UI to 1.34 ± 0.22 (p < 0.001), showing a protective efficacy comparable to misoprostol (1.12 ± 0.15). GKSE increased gastric juice pH from 2.15 ± 0.20 to 4.65 ± 0.35, while significantly reducing total acid output (p < 0.01). Histological sections confirmed that GKSE preserved mucosal gland structural alignment and minimized neutrophil filtration. These findings reveal that Garcinia kola protects the gastric mucosa by suppressing acid secretion and preserving epithelial architecture against NSAID-induced oxidative stress.

Keywords: Garcinia kola, Gastric Ulcer, Indomethacin, Gastroprotection, Acid Output, Wistar Rats

Manuscript Timeline: Received: July 15, 2026; Revised: August 22, 2026; Accepted: September 05, 2026; Published: September 21, 2026

Citation: Adefegha O.A., & Nwosu B.I. (2026). Gastroprotective Mechanisms of Garcinia kola Seed Extract Against Indomethacin-Induced Gastric Ulceration in Rats. International Journal of Anatomy and Physiology, 15(9), 233–244. DOI: 10.46882/2026/IJAP/000187