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Development of bone

Ossification , or osteogenesis, is the process of bone formation by osteoblasts. Ossification is distinct from the process of calcification; whereas calcification takes place during the ossification of bones, it can also occur in other tissues. Ossification begins approximately six weeks after fertilization in an embryo. Before this time, the embryonic skeleton consists entirely of fibrous membranes and hyaline cartilage. The development of bone from fibrous membranes is called intramembranous ossification; development from hyaline cartilage is called endochondral ossification. Bone growth continues until approximately age 25. Bones can grow in thickness throughout life, but after age 25, ossification functions primarily in bone remodeling and repair.

Intramembranous ossification

Intramembranous ossification is the process of bone development from fibrous membranes. It is involved in the formation of the flat bones of the skull, the mandible, and the clavicles. Ossification begins as mesenchymal cells form a template of the future bone. They then differentiate into osteoblasts at the ossification center. Osteoblasts secrete the extracellular matrix and deposit calcium, which hardens the matrix. The non-mineralized portion of the bone or osteoid continues to form around blood vessels, forming spongy bone. Connective tissue in the matrix differentiates into red bone marrow in the fetus. The spongy bone is remodeled into a thin layer of compact bone on the surface of the spongy bone.

Endochondral ossification

Endochondral ossification is the process of bone development from hyaline cartilage. All of the bones of the body, except for the flat bones of the skull, mandible, and clavicles, are formed through endochondral ossification.

In long bones, chondrocytes form a template of the hyaline cartilage diaphysis. Responding to complex developmental signals, the matrix begins to calcify. This calcification prevents diffusion of nutrients into the matrix, resulting in chondrocytes dying and the opening up of cavities in the diaphysis cartilage. Blood vessels invade the cavities, and osteoblasts and osteoclasts modify the calcified cartilage matrix into spongy bone. Osteoclasts then break down some of the spongy bone to create a marrow, or medullary, cavity in the center of the diaphysis. Dense, irregular connective tissue forms a sheath (periosteum) around the bones. The periosteum assists in attaching the bone to surrounding tissues, tendons, and ligaments. The bone continues to grow and elongate as the cartilage cells at the epiphyses divide.

In the last stage of prenatal bone development, the centers of the epiphyses begin to calcify. Secondary ossification centers form in the epiphyses as blood vessels and osteoblasts enter these areas and convert hyaline cartilage into spongy bone. Until adolescence, hyaline cartilage persists at the epiphyseal plate    (growth plate), which is the region between the diaphysis and epiphysis that is responsible for the lengthwise growth of long bones ( [link] ).

Questions & Answers

state any one specialized animal cell and it's function
Pascal Reply
sperm cell: Fertilization
Tshering
Can DNA and RNA be praticalized
Oyewale Reply
you can make models of them and show how they replicate
Oswald
what is dentition
Tisa Reply
Study of teeths and their functions
Stanisla
what are the function
Tisa
it's not teeths. teeth is plural as well as singular noun. the function of the teeth is to cut and grind food for easier swallowing and for increasing the surface area if the fish as the substrate in which digestive enzymes work
Oswald
dentition is not the study of teeth but the arrangement of teeth in the mouth of species or individuals
Oswald
what are the two types of teeth
Tisa
Function of probosis
Adeola Reply
why do we study biology?
SYDNEY Reply
where biology began
Alhaji
What are chromesome
Talkmore Reply
condensed DNA wrapped with histone
Elias
what is chromosome?
Royd Reply
How can a person who has been in the vascular disease repairs his or her DNA
Rabson Reply
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Shaf Reply
Of wat
John
explanation for wat
Christian
Of war na so dat I can provide
John
Is d process which food is converted into substance dat can be utilize by d body
John
the meaning of disgestion
Charity Reply
because they are considered to be proteins ..lipids,fats, and nucleic acids
Geeta Reply
what is osmosis
Festus Reply
Is the movement of solvent molecules from the region of a higher concentration to the region of lower concentration
Muhammad
It is the movement of solvent from the region of lower concentration to the region of higher concentration through a semi-permeable membrane.
Helen
and diffusion
Prudent
it is the movement of water molecules fro region of higher conc. to the region of lower conc.thro a semi-permeable membrane.
Chansa
Diffusion is the movement of solute molecules from a region of higher concentration to a region of lower concentration.
Quartey
osmosis is the movement of water molecule from the region higher water potential to a region of lower water potential
Pascal
what is the function of Nerve cell?
Pascal
Hello Everyone!! Any good study app recommendations?
HONNEA Reply
For which subject
Sinyinza
Biology:)
HONNEA
Hello everyone!! I want to be sure does exoskeleton consist of endoskeleton? plz help right nw
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Try this one and also biology Olevels
Sinyinza
Thanks!
HONNEA
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Adeetya Reply
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Sinyinza
Thanks for the clarification.
Adeetya
WhAt are the differences between prokaryotic cell and eukaryotic cell
oluwapelumi Reply
Prokaryotic cell is a single celled organism that do not have membrane -bound nuclei.
Quartey
prokaryotes also lack other cell organelles whereas eukaryotes possess an organized nucleus with nuclear envelope and also they have complex locomotory and cytoskeletal structures
Pepper
genetic material is found in cytoplasm in prokaryotic cell while in eukaryotes genetic material is found in nucleus
shams
What cells are the basic unit of life?
Agyeman

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Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
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