Structure and length of transitional zone in the dog's external carotid artery was documented. Six normal adult male dogs were studied. The specimens were processed in the routine way by light and electron microscopy. It was established that the transitional zone with 17-mm length contains parallel and fenestrated elastic fibres. In the transitional zone, the elastic fibres in the extracellular space were greater in number than collagen fibres. However, in the non-transitional zone, the rows of smooth muscle cells were greater in number. There were more collagen fibres than elastic fibres in the extracellular space and the elastic fibres appeared to be fragmented. Therefore, the transitional zone showed a structure intermediate between those of elastic and muscular arteries. The involvement of a special structure of transitional zone in vascular disease such as atherosclerosis is suggested.
The proprioceptive system is actually a sensory system based on an individual's knowledge of the body. The aim of this study was to investigate the effect of estrogen and progesterone hormones on understanding and to recognize the proprioceptive sense the knee joint in healthy women during the menstrual cycle. Fifteen healthy women with regular menstrual cycles participated in this study. The estrogen and progesterone levels were evaluated during a cycle in the follicular, ovulation, and luteal phases. The effect on the sense of perception and cognition of the proprioceptive knee joint in two directions (extension and flexion), by target angle reconstruction at 30° was studied. The results showed that female sex hormones affect the knee active Joint Position Sense (JPS). In the extensions, the changes of the menstrual cycle affect the JPS in constant error during the ovulation phase. In the flexion, changes in the menstrual cycle affect the JPS in constant, absolute, and variable error during the luteal phase. The findings of this study show that the menstruation phases can change the active JPS at knee joint. Since the outbreak of joint problems, especially in the knee joint, is higher in women than in men, it was predicted that hormonal changes during the menstrual HIGHLIGHTS • The proprioceptive system provides a sense of body awareness and detects and controls force and pressure.• Menstruation is the regular, orderly shedding of the uterine wall, in response to the interactions of hormones produced by the hypothalamus, pituitary, and ovaries.• Estrogen is a steroid hormone and involved in the female reproductive organs, as well as numerous other biological systems including the neuroendocrine, vascular, skeletal, and immune systems.
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