<< Chapter < Page Chapter >> Page >
By the end of this section, you will be able to:
  • Explain the function of cartilage
  • List the steps of intramembranous ossification
  • List the steps of endochondral ossification
  • Explain the growth activity at the epiphyseal plate
  • Compare and contrast the processes of modeling and remodeling

In the early stages of embryonic development, the embryo’s skeleton consists of fibrous membranes and hyaline cartilage. By the sixth or seventh week of embryonic life, the actual process of bone development, ossification    (osteogenesis), begins. There are two osteogenic pathways—intramembranous ossification and endochondral ossification—but bone is the same regardless of the pathway that produces it.

Cartilage templates

Bone is a replacement tissue; that is, it uses a model tissue on which to lay down its mineral matrix. For skeletal development, the most common template is cartilage. During fetal development, a framework is laid down that determines where bones will form. This framework is a flexible, semi-solid matrix produced by chondroblasts and consists of hyaluronic acid, chondroitin sulfate, collagen fibers, and water. As the matrix surrounds and isolates chondroblasts, they are called chondrocytes. Unlike most connective tissues, cartilage is avascular, meaning that it has no blood vessels supplying nutrients and removing metabolic wastes. All of these functions are carried on by diffusion through the matrix. This is why damaged cartilage does not repair itself as readily as most tissues do.

Throughout fetal development and into childhood growth and development, bone forms on the cartilaginous matrix. By the time a fetus is born, most of the cartilage has been replaced with bone. Some additional cartilage will be replaced throughout childhood, and some cartilage remains in the adult skeleton.

Intramembranous ossification

During intramembranous ossification    , compact and spongy bone develops directly from sheets of mesenchymal (undifferentiated) connective tissue. The flat bones of the face, most of the cranial bones, and the clavicles (collarbones) are formed via intramembranous ossification.

The process begins when mesenchymal cells in the embryonic skeleton gather together and begin to differentiate into specialized cells ( [link] a ). Some of these cells will differentiate into capillaries, while others will become osteogenic cells and then osteoblasts. Although they will ultimately be spread out by the formation of bone tissue, early osteoblasts appear in a cluster called an ossification center    .

The osteoblasts secrete osteoid    , uncalcified matrix, which calcifies (hardens) within a few days as mineral salts are deposited on it, thereby entrapping the osteoblasts within. Once entrapped, the osteoblasts become osteocytes ( [link] b ). As osteoblasts transform into osteocytes, osteogenic cells in the surrounding connective tissue differentiate into new osteoblasts.

Osteoid (unmineralized bone matrix) secreted around the capillaries results in a trabecular matrix, while osteoblasts on the surface of the spongy bone become the periosteum ( [link] c ). The periosteum then creates a protective layer of compact bone superficial to the trabecular bone. The trabecular bone crowds nearby blood vessels, which eventually condense into red marrow ( [link] d ).

Questions & Answers

the study of the human body structure and how the parts are organised.
Charles Reply
Anatomy
Favour
Sokiri awe be serious... you guys
Josefs
Structure of human body?
Esther Reply
levels of organization of the human body
Deesh Reply
how do we calculate for GFR, what formula is used and some examples py
ATIM
the smallest cell in body
what is the function of stomach?
Bilal
the sperm is smallest cell in body
asma
anatomical description of human heart
Luceno Reply
what is human heart in anatomical perspective?
Luceno
Heart is a hollow muscular organ situated in the between the lungs in a space called mediastinum
Rukayya
Ooooh thanks l didn't know
Esther
How many cells are there in the body?
Esther
different between primary and secondary healing
Gilbert Reply
hello ,I'm new here I'm I welcome?
Nadesh Reply
what are the components of e cell
Nadesh
hi same i just downloaded this app yesterday and still haven't used it
purple
hello, am new here hope am welcome
Jessica
Yesssss please feel welcomed friends 🙏
jeniffer
every one.. welcome
Hussein
i downloaded last week and vow to use it.
Mikal
so, hello A&P family.
Mikal
Ur welcom
Muhasa
Am also new... I hope am fully welcome
Esther
Okay welcome
Toila
I am new as well guys
SURENDRA
hello guy
amj
hi
Payal
hi
that's a good response from everyone
SURENDRA
hi Hussein
I want ask questions
is that mycoplasma cell smaller than sperm cell .,hussein
types of cell divisions
Gladys Reply
meiosis n mitosis
shanique
Amitosis: cell division without replication of dna or disappearance of nuclear membrane. Mitosis: Process whereby a parent cell divides to form 2 or more genetically identical daughter cells. (occurs in most body cells except neurons)
Favour
Meiosis: Process whereby a parent cell divides to form 4 or more genetically unidentical daughter cells each being haploid ( having half the original number of dna as the parent cell)
Favour
Types of living things
Evah Reply
search up "taxonomy"
Favour
there are many kingdoms: animal, plants, fungi, and more
Favour
a better question would be "What are the various classifications of living organisms?"
Favour
learn to ask questions that aren't too vague
Favour
what is the largest bone of human?
Aicon Reply
thats a google question
Favour
search "largest bone in skeletal system"
Favour
femour
mnayeem
The skull
William
femur in thighs
Muhammad
femur
Akec
femur
Ceyni
femur
Ceyni
femur
odero
fumar
Sundus
Femure
John
femur
AbdFatai
femur
cc
fumer
selam
tigh bone (femur)
Samuel
femur
Godfrey
femur
Par
Femur
luanne
the diagram of cell membrane
Teboh Reply
***bit.ly/3kfrdfV Link to cell membrane diagram and more info... Remember, you can search the A&P book.
Favour
describe diffusion as used in body fluid movement
brenda Reply
how was the movement?
Jenelyn
classify joint function with example
James Reply
go to Google or YouTube bro
Prabin
James, the internet is your friend... use him well.
Favour
Structural Classification: Fibrous Joints (Joined by fibrous tissue) Cartilaginous Joints (Joined by Cartilage) Synovial Joints (Joined and surrounded by a joint cavity) Functional Classification: Synarthroses (Immovable) Diarthroses (Freely Movable) Amphiarthroses (Guess what this means...)
Favour
cytoskeleton diagram
Miriam Reply
two types of cells biological name
Miriam
eukaryotic and prokaryotic
Emraan
Difference between extracellular and intracellular
Eli Reply
extra (exit) outside the cell, intra inside the cell
Amy
extracellular is 1/3 of total body water...intracellular 2/3 of total body water
Favour
what is culture?
Nepi
is the way of life of people
Senior
He meant in the context of biology...as in "tissue culture".
Favour
what does depolarization mean...in terms of the cardiovascular system?
Tracy
depolarization means contraction
Abhishek
Depolarization, in the context of nerve and muscle tissue, is the decrease in membrane potential (the separation of charge between the extracellular and intracellular compartments). Basically, the charge in the cell becomes more positive when depolarization occurs.
Favour
In fact, the word 'polarize' used to mean dividing into extremes or opposite sides. The opposite is true for 'depolarize'
Favour
intracellular fluid is the fluid compartment of the body consisting of all water present within the cell...while extracellular fluid is water present out of the cell
brenda
Why apoptosis is important?
Duchess Reply
so that the body can be reorganised or reoriented by losing the older segment and formation of new segment
Prabin

Get the best Anatomy & Physiology course in your pocket!





Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Anatomy & Physiology' conversation and receive update notifications?

Ask