A stronger scene is shown in the film depicting a man struggling, choking and coughing up blood. This scene is very graphic and bloody.
In another scene, which is the most infamous scene in the whole film, a man's finger is bent backwards and broken. This scene is intense, terrifying and shocking.
Several time blood drops/globs are seen floating around in the ship.
Several instances of corpses floating (non graphic - just a body)
The alien feeds on blood (kind of like a vampire bat). Not super graphic other than blood leaving the victim and floating around
A rat is kept "tied down" in the science room (no experimentation happens to him). It does eventually get attacked and "dissolved & digested" by the alien, its mildly graphic and intense but not super gory.