Creature "Armed" Unarmed Attacks and Attacks of Opportunity

Question

Ok, I'm stuck in a rules question, and I can't decide on the answer. This is from a Rise of the Runelords campaign that's reached Fort Rannick. My players went up against the Ogre Fighters and one of my players has whips that he's used to disarm them. The Ogres then tried to punch him and we can't decide if their punches provoke attacks of opportunity or not, and if they do and he winds up tripping them, what then happens to their attack.

These are the relevant rules:

Unarmed Attacks: Striking for damage with punches, kicks, and head butts is much like attacking with a melee weapon, except for the following:

Attacks of Opportunity: Attacking unarmed provokes an attack of opportunity from the character you attack, provided she is armed. The attack of opportunity comes before your attack. An unarmed attack does not provoke attacks of opportunity from other foes, nor does it provoke an attack of opportunity from an unarmed foe. An unarmed character can’t take attacks of opportunity (but see “Armed” Unarmed Attacks, below).

“Armed” Unarmed Attacks: Sometimes a character’s or creature’s unarmed attack counts as an armed attack. A monk, a character with the Improved Unarmed Strike feat, a spellcaster delivering a touch attack spell, and a creature with natural physical weapons all count as being armed (see natural attacks).

Natural Attacks: (relevant section) Some fey, humanoids, monstrous humanoids, and outsiders do not possess natural attacks. These creatures can make unarmed strikes, but treat them as weapons for the purpose of determining attack bonuses, and they must use the two-weapon fighting rules when making attacks with both hands. See Table 3–1 for typical damage values for natural attacks by creature size.

Do the Ogre's fists count as "natural physical weapons" listed in the "Armed Unarmed Attacks" rule or not? I can make a case for both in this instance. I would count them as weapons to determine their attack bonus, and I would roll damage for them based off of the Natural Attacks by Size chart (I assume they fall under the "Other" listing), so for both attack and damage they count as physical weapons, but do they also count as such for attacks of opportunity?

Secondly, if they do provoke an AoO, and he then uses his whips and trips them, what happens to their attacks? The trip AoO would happen before the punch, so they fall prone. Does that then stop their punch completely and they lose their action, or do they get to still try to punch him while prone (with the penalty to attack roll)?

Answer 1

A creature's fists can be a natural attack called slam (see the table in the link) or, as it is written below the table, they can be just old, plain unarmed attacks.

Some creatures do not have natural attacks. These creatures can make unarmed strikes just like humans do.

The Ogre has no slam attack, just club and javelin attacks, so their fists are unarmed attacks and, as with all unarmed attacks, they are subject to attack of opportunity when they hit someone with them.

Nothing in their stat block says that their fists are treated as weapons, so their fists don't benefit from the "Armed unarmed attacks" rule.

So what happens is that they attack with their fists, and if the opponent threatens their squares (not a given since most weapons capable of AoO don't have reach while the ogre does), they can get attacked and tripped.

Being tripped does not prevent the attack (if it did, it would be written in the Trip description) but it gets the malus for being prone, because the AoO happens first.