The human skeleton steadily changes structure and mass during life because of a variety of internal and external factors. Extracellular substance and bone cells get old, characteristic structural remodeling occurs with age and these age-related changes are important in the discrimination between pathological and physiological changes. Perhaps 20 percent of the bone mass is lost between the fourth and the ninth decades, osteoblasts function less efficiently and gradual loss of bone substance is enhanced by delayed mineralization of an increased surface area of thin and relatively less active osteoid seams. After the fifth decade, osteoclasia and the number of Howship's lacunae increase, and with age, the number of large osteolytic osteocytes increases as the number of small osteocytes declines and empty osteocyte lacunae become more common. The result is greater liability to fracture and diminished healing or replacement of injured bone.

Video footage from the KXAS-TV/NBC station in Fort Worth, Texas, to accompany a news story.

B-roll video footage from the KXAS-TV/NBC station in Fort Worth, Texas, to accompany a news story.

Video footage from the KXAS-TV/NBC station in Fort Worth, Texas, covering a news story about a press hearing with Jim Mattox about American involvement with Ugandan pilots and Uganda President Idi Amin, specifically in Georgia. This story aired at 10:00 P.M.

Student newspaper of the University of Oklahoma in Norman, Oklahoma that includes national, local, and campus news along with advertising.

Interview with Robert Saunders, U.S. Army veteran, concerning his experiences at Schofield Barracks with the 35th Infantry Regiment, 3rd Battalion, M Company during the Japanese attack at Pearl Harbor on December 7, 1941.

Daily newspaper from Perry, Oklahoma that includes local, state, and national news along with advertising.

Photograph used for a newspaper owned by the Oklahoma Publishing Company. Caption: "Mr. and Mrs. Bill Campbell of Norman"

Photograph used for a story in the Daily Oklahoman newspaper. Caption: "Children gather around Jessie Hayes, center, OSAF Instructor, to make decorations."

Photograph used for a story in the Daily Oklahoman newspaper. Caption: "That seems to be the question on the mind of 5-year-old Kyle Henson, one of the youngsters who tried his hand at creating an original Christmas bauble."

Photograph used for a story in the Oklahoma Times newspaper. Caption: "Mike Hudson makes a diving save on his dig shot."

Photograph used for a story in the Daily Oklahoman newspaper. Caption: "BALANCING ACT is performed by Perry Lambird, front, and Bill Gummer-son, who joined other patrons and area residents in assembling elaborate playground equipment Saturday at Wilson Elementary School, 600 NW 22."

Photograph used for a story in the Daily Oklahoman newspaper. Caption: "Mrs. Carl Taggart, Mrs. Guy B. Treat and Mrs. Inez Gose Lee share reminiscences about the Overholser Mansion as they pose in the living room of the spacious house during the Chafing Dish Society's party."

Photograph used for a story in the Daily Oklahoman newspaper. Caption: "Mrs. Harry Koenig wearing a magnificent velvet and gold craftan she got in the middle east, and Wendell admire one of the many Christmas trees lighting up the historic Overholser Mansion for the holiday season."

Photograph used for a story in the Daily Oklahoman newspaper. Caption: "(Norman attorney) John M. Luttrell became the president-elect of the Oklahoma Bar Association Friday brfore the group ended its three-day annual convention in Oklahoma City."

Photograph used for a story in the Oklahoma Times newspaper. Caption: "Russ Miller prepares to pop a serve."

Photograph used for a story in the Daily Oklahoman newspaper. Caption: "A weary Karen Mills who showed her school-girl spunk by trudging through the snowy Rocky Mountain wilderness to find aid for her companions after their small plane crashed last week, returned Saturday to her Nichols Hills home."

Photograph used for a story in the Oklahoma Times newspaper. Caption: "It's that time again when Oklahoma University and Oklahoma State footballers collide in their annual cross-state contest Saturday in Stillwater."

Photograph used for a story in the Daily Oklahoman newspaper. Caption: "Riding into the glare of spotlights,Mildred Farris,Eddington,carries Old Glory during opening ceremonies at the National Finals Rodeo in Oklahoma City."

Photograph used for a story in the Daily Oklahoman newspaper. Caption: "Riding into the glare of spotlights,Mildred Farris,Eddington,carries Old Glory during opening ceremonies at the National Finals Rodeo in Oklahoma City."

Photograph used for a newspaper owned by the Oklahoma Publishing Company.

Photograph used for a newspaper owned by the Oklahoma Publishing Company.

Photograph used for a newspaper owned by the Oklahoma Publishing Company.

Photograph used for a story in the Daily Oklahoman newspaper. Caption: "In the nursery at the Overholser Mansion, Mr. and Mrs. John Griffen Weinmann pose with a mannequin wearing a lace dress which once belonged to Mrs. Weinmann's grandmother."