Activity 5: Ossification-Bone Formation and Growth in Length and Examining the Osteogenic Epiphyseal Plate
All bones of the body inferior to the skull, except for the ____, form in the embryo by the process of ____.
clavicles; endochondral ossification
Endochondral ossification uses ____ cartilage "bones" as a model for bone formation.
What are the 4 major steps of endochondral ossification?
1. Blood vessels invade the perichondrium covering the hyaline cartilage model and converts it to periosteum.
2. Osteoblasts at the inner surface of the periosteum secrete bone matrix around the hyaline cartilage model, forming bone collar.
3. Cartilage in the shaft center calcifies and then hollows out, forming an internal cavity.
4. A periosteal bud invades the cavity and forms spongy bone, which is removed by osteoclasts, thus producing the medullary cavity. Chondroblasts then lay down new cartilage matrix on the epiphyseal face of the epiphyseal plate, and it is eroded away and replaced by bony spicules on the diaphyseal face.
A periosteal bud is composed of what 5 structural components?
1. blood vessels
3. red marrow elements
The "periosteal bud" process proceeds in how many directions and from what center?
both directions from the primary ossification center
The process of chondroblasts laying down new cartilage matrix on the epiphyseal plate and having it eroded away and replaced by bone continues until when?
What 2 things happen to the medullary cavity as bones grow longer?
It gets larger and longer as well.
What are osteoblasts?
Osteoblasts are a special type of fibroblasts found in bones that secrete the bone matrix.
What are osteoclasts?
Cells responsible for the resorption of the bone matrix. They secrete hydrochloric acid to break down mineral components and lysosomal enzymes to break down organic components.
Osteocytes keep what healthy?
Function to keep the bone matrix healthy.
What are osteogenic cells?
Stem cells that differentiate to form osteoblasts.
The bone matrix secreted by the osteoblasts is called what?
Which 3 cells produce or help maintain bone tissue?
1. Osteogenic cells
Which cell re-absorbs the bone matrix?
If osteocytes die or are destroyed, what happens to the bone matrix?
The bone matrix is reabsorbed by the osteoclasts.
Growth in length of a long bone occurs at which location?
The side of the epiphyseal plate facing the epiphysis contains what type of cells?
Resting cartilage cells
Cells proximal to the resting area of the cartilage cells are arranged in what 4 zones?
Of the 4 zones that are arranged proximally to the resting cartilage cells, which is the youngest, and which is the oldest stage of growth?
What happens in the proliferation zone in regards to cartilage cells?
Cartilage cells undergo mitosis
What happens in the hypertrophic zone in regards to cartilage cells?
Older cartilage cells enlarge
What 3 things happen in the calcification zone in regards to the matrix and cartilage cells?
Matrix becomes calcified; cartilage cells die; matrix begins deteriorating.
What happens in the ossification zone?
New bone forms.
Name the missing features.