Bone Physiology and Ossification Review

Question and answer flashcards covering structural bone types, Wolff's law, endochondral and intramembranous ossification, bone marrow distribution, appositional growth, and calcium homeostasis feedback loops.

How is the butterfly-shaped sphenoid bone categorized structurally?

It is categorized as an irregular bone due to its complex and unique shape.

What is a sesamoid bone, and what is the main example in the human body?

A sesamoid bone is a structural category of bone that forms within a tendon during development, with the patella being the primary example.

What principle does Wolff's Law describe regarding bone remodeling?

Wolff's Law states that bones remodel and grow thicker or stronger in response to mechanical stress or usage ("use it or lose it").

What progression of changes do chondrocytes undergo at the growth plate as they migrate toward the diaphysis?

Chondrocytes undergo proliferation (mitosis), hypertrophy (getting large), and finally apoptosis (cell death).

How do osteoblasts ossify the cartilage matrix at the growth plate?

Osteoblasts invade the empty lacunae left by dead chondrocytes and secrete bony matrix to replace the cartilage.

What occurs during the second step of fetal endochondral ossification?

Osteoblasts secrete matrix around the outside of the diaphysis to form a periosteal collar.

Where does the primary ossification center form during fetal long bone development?

It forms in the center of the diaphysis after a blood vessel invades the hyaline cartilage model.

Where do secondary ossification centers form during fetal endochondral ossification?

They form in the epiphyses of the bone when blood vessels invade them with bone cells.

What type of bone marrow is stored in the medullary cavity of the diaphysis, and what is its composition?

Yellow bone marrow, which consists primarily of fat storage.

Where is red bone marrow located in a child's long bone, and what is its function?

Red bone marrow is located between the trabeculae of spongy bone in the epiphyses and is responsible for blood formation.

What is appositional growth?

Appositional growth is the process where bone grows in width or thickness by adding bone matrix to the external surface of existing bone.

How does intramembranous ossification differ from endochondral ossification?

Intramembranous ossification converts fetal mesenchyme directly into bone (such as flat bones) without using a hyaline cartilage step.

In the negative feedback loop for low blood calcium, what serves as the control center?

The parathyroid gland.

What is the efferent signal and effector in response to low blood calcium levels?

Parathyroid hormone (PTH) is the efferent signal, and osteoclasts in the bone act as the effectors to break down bone matrix and release calcium into the blood.