The axon initial segment (AIS) is an axonal subdomain integral to neuronal excitability, yet its geometrical diversity within the hippocampus is poorly understood. This study provides a detailed examination of the variability of proximal cell morphology across murine hippocampal neurons, analyzing molecular and geometrical parameters such as AIS length and position, dendrite shape, soma, and apical dendrite size across dorsal-ventral, superficial-deep, and proximal-distal axes. We observed significant differences in AIS characteristics, with CA3 neurons displaying longer AIS and more distal origins compared to CA1 and subicular neurons. Neurons with dendritic axon origins (AcDs) showed region-specific prevalence, particularly in the intermediate and ventral hippocampus. Despite strong correlations among most morphological parameters, AcDs had minimal correlation with cell morphology. To assess the functional impact of AIS variability, we simulated the signal integration and firing behaviors of 3,326 characterized cells using NEURON. Preliminary results suggest that morphological diversity of axon onset and heterogeneity of the AIS may influence neuronal homeostasis and functional diversity, potentially affecting hippocampal network dynamics. We further demonstrate that AcD morphology is also abundant in human hippocampus. Our findings highlight the complex relationship between neuronal structure and function, emphasizing the need for further investigation into the role of AIS heterogeneity in neuronal excitability and signal integration.