Torso in Spanish can be called el tronco, but in everyday speech people more often use specific body parts: back, chest, stomach, shoulders, arms. These words are especially useful when you need to describe pain, movement, or physical condition.
Back is la espalda. This is one of the most necessary words because back pain is a common complaint:
Me duele la espalda.
My back hurts.
Tengo la espalda cansada.
My back is tired.
Chest / rib cage is el pecho or la caja torácica. In everyday speech, el pecho is used more often. This word can mean the chest as a body area. In a medical context, you may see la caja torácica — rib cage.
Me duele el pecho.
My chest hurts.
La caja torácica protege los pulmones y el corazón.
The rib cage protects the lungs and the heart.
Stomach / abdomen is el abdomen or la barriga. El abdomen sounds more neutral and medical, while la barriga is conversational.
Me duele el abdomen.
My abdomen hurts.
Me duele la barriga.
My stomach hurts.
Shoulder is el hombro, arm is el brazo, and hand is la mano. In English, “arm” and “hand” are already different words, and Spanish also separates them clearly. El brazo is the part from the shoulder to the hand, while la mano is the hand.
Levanta el brazo.
Raise your arm.
Dame la mano.
Give me your hand.
Elbow is el codo, wrist is la muñeca, and fingers are los dedos. Interestingly, la muñeca also means “doll,” so the meaning depends on the context.