The vagina is often showed to be one long tube, that is the same from top to bottom, which it is not. I’m sure if you are reading this and have a vagina, or have interacted with one, you may think that sounds obvious, come to think of it.
The Bottom or Base of the Vagina
The internal clitoral bulbs either side of the vagina may enjoy a gentle stretching through the inside of the vagina, only once you are feeling really turned on though. This is why penetrating the vaginal opening with fingers, a toy or penis can feel good, as it pushes the internal clitoral bulbs apart causing a pleasurable pressure. A rhythmic stimulation or stroke can also be enjoyable. Again, usually only when the owner of the clitoris feels aroused and the vagina opening is moist to the touch.
Disclaimer Note; these physical changes happen in their own time, and don't like, or need to be rushed. They often don’t happen rapidly, or always at the same time, each individual, in each different circumstance may respond differently. Psychology and emotions are important and influence arousal.
The Deep Vagina
When a person is feeling very aroused, the uterus, (and with it the cervix) moves forward towards the belly button, and very top or back of the vagina is then exposed.
This area at the top or ‘deep’ in the vagina (shown in the illustration) is usually covered by the cervix, has a dense patch of nerves that can be very pleasurable and intense. The cervix is the front part of the uterus, that has a small opening, called the O’s, this is where menstrual blood leaves and baby’s come out of into the vaginal canal.
When people talk about ‘cervical orgasms’, when there is penetration of this deep vagina area, this is usually what they refer to; the deep, top part of the vagina wall rather than the actual cervix.
If the person isn’t fully aroused, or not quite in the mood and/or the cervix hasn’t moved forward, out of the way, any penetration may bump against the cervix, which can be painful.
However you can always go to you doctor if you are concerned about pain.