'You have 4 pairs of these air-filled passages, 2 in the forehead, 2 in the cheekbones'
sinuses
THE HUMAN BODY: You have 4 pairs of these air-filled passages, 2 in the forehead, 2 in the cheekbones
You have 4 pairs of these air-filled passages, 2 in the forehead, 2 in the cheekbones
You have 4 pairs of these air-filled passages, 2 in the forehead, 2 in the cheekbones
THE HUMAN BODY
sinuses
THE HUMAN BODY