In various bones from 40-50 year old men, numerous osteons were found in spongy trabeculae. As the bones examined are subjected to different mechanical loads, and, in all samples, the osteon frequency appeared to increase with the increase in the trabecular thickness, the endotrabecular osteons was supposed to improve the deep-seated cell metabolism. Because the architecture of the spongiosa changes with age, we studied the endotrabecular osteons in the same bone but in individuals of different age. Human femurs from the collection of our Institute were divided into three groups, corresponding to the 3rd, 5th, and 7th decade of life. Trabeculae were dissected from the proximal end in correspondence of the head, lateral and medial arrangement of the neck. On the serially transverse section the thickness of trabecular tracts with or without osteons, the distance of the deep-seated osteocytes from filtering surfaces, and the orientation of the collagen fibres have been analysed. The mean thickness of the trabeculae decreases with age in the head and lateral arrangement but not in the medial one. The trabecular tracts with osteons are, on the average, significantly thicker than those without them. Almost all endotrabecular osteons show alternate lamellae, notwithstanding that the trabeculae examined are subjected to different type of mechanical forces. These findings would confirm our previous hypothesis that the presence of osteons in the trabeculae responds to metabolic request rather than to mechanical one.

Adult↗

PubMedDate not supplied

Post-natal bone growth in the semicircular canals of the dog.

Dogs from the same litter, divided into three groups aged 10, 25, and 50 days, received an intraperitoneal injection of tetracycline for two successive days. The temporal bones were fixed, embedded in methylmethacrylate, sectioned in to a single 100 microns thick section along the main axis of the anterior and lateral semicircular canals, grounded by hand to 30 microns and observed at UV light. The new bone tissue is laid down both at the endosteal and endochondral bone of the anterior and lateral semicircular canals. The bone deposition decreases with the age of the animal and earlier at the endosteum than at the endochondral bone.

Aging↗