We learned to draw blood and put in IV’s on each other. Hernia checks, testicular exams, DREs, breast and pelvic exams were learned by practicing on paid instructors - I wouldn’t call them volunteers, since a) they were paid and b) they weren’t just there to be passive subjects but had their own training so as to give useful feedback and guidance. The male patients got a fraction of the pay of the females; something like 25% as I recall. For our exams, we used a prostate simulator with a silicone anus/rectum and swappable healthy/diseased prostates.
We also learned nasogastric tube placement by practicing on each other. Some students did arterial lines on each other, I thought that that was pretty stupid actually.
Intubation can be practiced on mannequins; my wife practiced neonatal intubation on kittens. Surgical techniques can in some cases be practiced on simulators, both physical and computer-based - this is mostly the case for laparoscopic techniques. Others can be taught with living, anesthetized pigs - at the beginning of my residency a group of four residents used one pig to learn chest tubes, vascular cutdowns, suture ligation of bleeding vessels, operation of surgical staplers and other instruments, etc. Those pigs were pretty well used up by the end of the day. I doubt that they still do that kind of training, though. Incisions and suturing can be practiced using pig’s feet or pork bellies or oranges. Orthopods practice new techniques using cadaver parts, like a severed leg for knee procedures.
Many invasive things like central lines, chest tubes, endoscopy, bronchoscopy, etc are learned by doing them on patients: preferably initially in the OR, ICU, or ER on anesthetized patients and under direct supervision. Doing your first invasive procedure on an awake patient without supervision brings a new level of stress to the situation.
