Question on manual transmissions & oil

[InnerDragon10]

So I replaced the oil in my rear diff as well as my transmission this weekend. I used Red Line oils, so I bought everything online. Well, I ran out of transmission oil to fill the gearbox up with . I filled it with 3 quarts and still didn't have any overflowing out. Unfortunately, I had to button it all back up and rush order some oil (arriving today).

I started wondering about how oils circulate in manual transmissions. Is it just a sump that the gears run in, slinging oil around? Anyone have an idea as to how submerged everything is in the box when you have the proper oil level? I'm doing my best not to drive the car until I have the proper oil level in the box, but I'm wondering if I'm at any real risk of starving gearing/bearings if I'm missing less than half a quart (supposedly what it takes to properly fill the gearbox up).