Forgetful Surgeon Joke (With Grammar Explanations)

病人：“医生，你把剪刀留在我肚子里了。”
bìng rén: yīshēng, nǐ bǎ jiǎndāo liú zài wǒ dù zi lǐ le 
Patient: "Doctor, you have left a pair of scissors in my stomach." 

医生：“没关系，我还有一把。”
yī shēng: méi guān xì wǒ hái yǒu yī bǎ 
Doctor: "It does not matter, I have another one."

Grammar Points

1. Expressing Specific Location with 在 

在。。。里 / 下 / 上 
zài... lǐ/ xià/ shàng 

This grammar pattern is used to say where one object is in relation to another object. 

在我肚子里 - zài wǒ dù zi lǐ - in my stomach 
在桌子上 - zài zhuōzi shàng - on the table 
在树下 - zài shù xià - under the tree 

If this pattern is placed in the middle of the sentence (used as a subject), then 在 is obligatory. If the structure is at the beginning of a sentence, then you can omit 在. 
黑猫在房子里。- hēi māo zài fángzi lǐ - The black cat is in the house.
桌子上有苹果吗？-  zhuōzi shàng yǒu píngguǒ ma? - Are there apples on the table?
This grammar structure is commonly used with 方位词 [ fāng wèi cí ] - nouns of location: 

• 里面 [ lǐmiàn ] - inside 
• 里边 [ lǐbiān ] - inside 
• 上面 [ shàngmiàn ] - on top of 
• 下面 [ xiàmiàn ] - below 
• 旁边 [ pángbiān ] - next to

2. Sentences with 把

Subject + 把 (bǎ) + Object + Verb + ...

This grammar pattern is used when the object is obvious, and you need to describe what happened to it in some details (the verb alone is not enough, there should be some context). 把 sentence cannot be about general classes of things. Its object should be definite (known from context or clear to the speaker and the listener).
你把剪刀留在我肚子里了。
nǐ bǎ jiǎndāo liú zài wǒ dù zi lǐ le
You have left a pair of scissors in my stomach.
我把这个东西放在这里。
wǒ bǎ zhège dōng xī fàng zài zhè lǐ 
I put this stuff here.

3. 把 As a Measure Word

In the joke 把 is also used in this sentence: 我还有一把。
This is not a 把 sentence. In this case 把 is a specifier (a measure word). It is used to quantify objects with a handle and things that can be grasped (knives, umbrellas, toothbrushes, etc.).

• 两把刀 - liǎng bǎ dāo - two knives 
• 十把雨伞 - shí bǎ yǔ sǎn - ten umbrellas