Curious Centers Knockoff

Here's one based on your puzzling team efforts over the weekend. Find the words that have "sth" in the center with the following letter patterns. Some patterns may have more than one answer.

-1. -sth--
-2. -sth---
-3. --sth---
-4. --sth---
-5. --sth----
-6. ---sth---
-7. --sth----
-8. --sth-----
-9. ---sth----
-10. ---sth---- (2 related answers)

2. isthmus

9. prosthesis

1. asthma

Hi again.

8. posthumous

6. firsthand

10. anesthetic/anesthesia
prosthetic/prosthesis

3. Posthorn

Bernie

Great solves!

Cheryl, you got both for #10, which could also be for the same layout on #9 which Joan got. I didn't think of two solutions for that one.

Bernie, that's a new one for me. Good one. I had masthead.

7. posthaste

4. masthead

Yes

5. aesthetic

Looks good, Joan