The tissue through which gases are exchanged between the blood and the air in the lungs is  

  The arrector pili muscle is attached to  

  The wall of the heart is made up of three layers, including the middle layer responsible for the heart’s pumping action. These layers are all the same tissue type, epithelium.  

  Aging affects the appearance of the skin producing wrinkles and sagging due to decreased collagen and elastin formation.  

  Acne is a disorder of the  

  The type of intercellular junction that forms tubular channels is  

  The tissue that forms the inner lining of the respiratory passages is  

  Apocrine sweat glands are most abundant on or in the  

  The differences among merocrine, apocrine, and holocrine secretions are the  

  Muscle cells with more than one nucleus are