Bones that originate within sheetlike layers of connective tissues. (ex: flat bones of the skull, clavicles, sternum, and some facial bones)
Bones that begin as masses of hyaline cartilage later replaced by bone tissue. (ex: most bones of the skeleton)
Bone-forming cells; deposit bony matrix around themselves, forming spongy bone.
When osteoblasts become surrounded by bone matrix, and then enclosed in lacunae (tiny chambers in bone matrix), they are known as what?
Tough vascular covering that comes from cells of the connective tissue outside the developing bone; osteoblasts on the inside of the _____ form a layer of compact bone over the surface of the newly formed spongy bone.
The process of replacing connective tissue to form an intramembranous bone.
Masses of cartilage that begin the development of endochondral bones.
The process of forming an endochondral bone by the replacement of hyaline cartilage.
The region in the center of the diaphysis of the long bone where bone develops; bone tissue begins to replace hyaline cartilage and bone develops from it toward the ends of the cartilaginous structure.
Primary Ossification Center
The regions in the epiphyses of the long bone where spongy bone forms in all directions as the epiphyses remain cartilaginous and continue to grow.
Secondary Ossification Centers
A band of cartilage between the primary and secondary ossification centers; in the long bone, the diaphysis is separated from the epiphysis by it.
How does Vitamin D influence bone development?
It's needed for absorption of calcium in the small intestine
What happens if you don't have enough Vitamin D?
Calcium is poorly absorbed and the inorganic salt portion of bone matrix lacks calcium, softening and deforming bones
How does Vitamin A influence bone development?
It's necessary for osteoblast and osteoclast activity during normal development
What happens if you don't have enough Vitamin A?
Bone development will slow down
How does Vitamin C influence bone development?
It's necessary for collagen synthesis
What happens if you don't have enough Vitamin C?
Osteoblasts cannot produce enough collagen in the extracellular matrix of the bone tissue, so bones are abnormally slender and fragile
How does a growth hormone influence bone development?
It stimulates division of cartilage cells in the epiphyseal plates
What happens if you lack a growth hormone?
The long bones of the limbs fail to develop normally, resulting in pituitary dwarfism
What happens if too much growth hormone is released before the epiphyseal plates ossify?
It will result in pituitary gigantism; for an adult, it causes acromegaly, in which the hands, feet, and jaw enlarge
How do sex hormones influence bone development?
At puberty, the hormones are abundant, causing the long bones to grow considerably; they also stimulate ossification of epiphyseal plates, which then stops bone lengthening
How does physical stress influence bone development?
When skeletal muscles contract, they pull at their attachments on bones, and the resulting stress stimulates the bone tissue to thicken and strengthen (hypertrophy)
What happens if you don't have enough physical stress?
With lack of movement, the bone tissue wastes, becoming thinner and weaker (atrophy)
What happens when levels of blood calcium are too high?
Excess calcium is deposited into the bones through a negative feedback mechanism of calcium homeostasis
What happens when levels of blood calcium are too low?
Calcium is released from bone though a positive feedback mechanism of calcium homeostasis
Senses the increased blood calcium and releases calcitonin; part of negative feedback mechanism of calcium homeostasis.
Secreted by the thyroid gland, stimulates osteoblasts to form bone tissue; part of negative feedback mechanism of calcium homeostasis.
Stimulated by calcitonin to form bone tissue; part of negative feedback mechanism of calcium homeostasis.
Senses the decreased blood calcium and secretes the parathyroid hormone; part of positive feedback mechanism of calcium homeostasis.
Secreted by parathyroid glands, stimulates osteoclasts to break down bone tissue; part of positive feedback mechanism of calcium homeostasis.
Stimulated by the parathyroid hormone to break down bone tissue; part of positive feedback mechanism of homeostasis.