Which type of gland can become blocked and form a "blackhead? "?

The type of gland that can become blocked and form a blackhead is: Sebaceous

Sebaceous funcion's is to lubricate and waterproof the skin and hair of mammals with an oily substance.
Sometimes, this oily substance could block the pores of your skin, which caused the dirt to gathered in that pores and forming a blackhead.

Anxiety, stress, or something like that

Answeralong with the tissue lining,the blood,tissue,and unfertilized egg leave the uterus,going through the vagina on the way out of the body,(menstrual period);