Several bones of the skull contain air-filled chambers
called sinuses. Sinuses have two major functions: (1) They
make a bone weigh less than it would otherwise, and (2) the
mucous membrane lining them produces mucus that moistens
and cleans the air in and adjacent to the sinus.
(Fundamentals of Anatomy & Physiology - Frederic H. Martini, Ph.D. & Judi L. Nath, Ph.D.)
Does the underlined part make sense to you? Am I right in saying that "them" should be omitted? It doesn't make sense to me with "them".
Thank you in advance.
called sinuses. Sinuses have two major functions: (1) They
make a bone weigh less than it would otherwise, and (2) the
mucous membrane lining them produces mucus that moistens
and cleans the air in and adjacent to the sinus.
(Fundamentals of Anatomy & Physiology - Frederic H. Martini, Ph.D. & Judi L. Nath, Ph.D.)
Does the underlined part make sense to you? Am I right in saying that "them" should be omitted? It doesn't make sense to me with "them".
Thank you in advance.