Inadequate cell nutrition around vessels causes degeneration of tunica adventitia . 血管周围细胞的营养不足,引起外膜的变性。
The wall of digestive tube was composed of mucous membrane , thin submucosa , tunica muscularis and tunica adventitia , but duodenal gland in duodenum was not found 消化壁一般分为4层,由内向外为粘膜、粘膜下层、肌层和外膜,其中粘膜下层很薄,十二指肠粘膜下层无十二指肠腺。