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By the end of this section, you will be able to:
  • Describe the two processes by which mesenchyme can give rise to bone
  • Discuss the process by which joints of the limbs are formed

Joints form during embryonic development in conjunction with the formation and growth of the associated bones. The embryonic tissue that gives rise to all bones, cartilages, and connective tissues of the body is called mesenchyme. In the head, mesenchyme will accumulate at those areas that will become the bones that form the top and sides of the skull. The mesenchyme in these areas will develop directly into bone through the process of intramembranous ossification, in which mesenchymal cells differentiate into bone-producing cells that then generate bone tissue. The mesenchyme between the areas of bone production will become the fibrous connective tissue that fills the spaces between the developing bones. Initially, the connective tissue-filled gaps between the bones are wide, and are called fontanelles. After birth, as the skull bones grow and enlarge, the gaps between them decrease in width and the fontanelles are reduced to suture joints in which the bones are united by a narrow layer of fibrous connective tissue.

The bones that form the base and facial regions of the skull develop through the process of endochondral ossification. In this process, mesenchyme accumulates and differentiates into hyaline cartilage, which forms a model of the future bone. The hyaline cartilage model is then gradually, over a period of many years, displaced by bone. The mesenchyme between these developing bones becomes the fibrous connective tissue of the suture joints between the bones in these regions of the skull.

A similar process of endochondral ossification gives rises to the bones and joints of the limbs. The limbs initially develop as small limb buds that appear on the sides of the embryo around the end of the fourth week of development. Starting during the sixth week, as each limb bud continues to grow and elongate, areas of mesenchyme within the bud begin to differentiate into the hyaline cartilage that will form models for of each of the future bones. The synovial joints will form between the adjacent cartilage models, in an area called the joint interzone    . Cells at the center of this interzone region undergo cell death to form the joint cavity, while surrounding mesenchyme cells will form the articular capsule and supporting ligaments. The process of endochondral ossification, which converts the cartilage models into bone, begins by the twelfth week of embryonic development. At birth, ossification of much of the bone has occurred, but the hyaline cartilage of the epiphyseal plate will remain throughout childhood and adolescence to allow for bone lengthening. Hyaline cartilage is also retained as the articular cartilage that covers the surfaces of the bones at synovial joints.

Chapter review

During embryonic growth, bones and joints develop from mesenchyme, an embryonic tissue that gives rise to bone, cartilage, and fibrous connective tissues. In the skull, the bones develop either directly from mesenchyme through the process of intramembranous ossification, or indirectly through endochondral ossification, which initially forms a hyaline cartilage model of the future bone, which is later converted into bone. In both cases, the mesenchyme between the developing bones differentiates into fibrous connective tissue that will unite the skull bones at suture joints. In the limbs, mesenchyme accumulations within the growing limb bud will become a hyaline cartilage model for each of the limb bones. A joint interzone will develop between these areas of cartilage. Mesenchyme cells at the margins of the interzone will give rise to the articular capsule, while cell death at the center forms the space that will become the joint cavity of the future synovial joint. The hyaline cartilage model of each limb bone will eventually be converted into bone via the process of endochondral ossification. However, hyaline cartilage will remain, covering the ends of the adult bone as the articular cartilage.

Questions & Answers

Card 5 / 12: For whom would an appreciation of the structural characteristics of the human heart come more easily: an alien who lands on Earth, abducts a human, and dissects his heart, or an anatomy and physiology student performing a dissection of the heart on her very first day of class? Why?
Gelowe Reply
what are regular shaped cells with granules in the cytoplasam
Kabita Reply
PMNL
Dinu
I need sylubuss of clinical officers book
Omary Reply
cholesterol normal value is
BISWANATH Reply
less than 200mg/dl
Ashis
100 to159mg/dL
Dinu
Early this wk. I had some "A & P" questions & answers unfortunately didn't save them, Is there any way I can have them back ,so as 2 save them?. Thnx.
Kechi
what are the functions of the female reproductive system
Lister Reply
it produces the female egg necessary for reproduction, called the Ova or Oocytes. The system is designed to transport the Ova to the site of fertilization.
Kechi
Female reproductive system was mainly functioned to produce ova(ovum) (female eggs) Into which will be fertilized by male gamete to produce zygote
Omary
absolutely right
nimco
wa qalad nimco rage iska hubi
Khaliil
waxwalba ka fikirbay ubaahantahay
Ahmed
ha wayo jawabtoda wa qabyo nimco wey ku raacdat
Khaliil
ha wayo jawabtoda wa qabyo nimco wey ku raacday
Khaliil
wxayaabaha qaarkood waaa in aan u feejignaano
Ahmed
asc if I try female reproductive system has two function the first is to produce egg cell and the second is to protact and nourish the offspring until birth
Muriidi
what is stercobilinogen
Hancerich Reply
fecal urobilinogen. Created by bacteria in the gut. a chemical that gives feces brown color.
Blayne
next question pls.
Kechi
The rate of diffusion increases if the
stella
What's the answer?
Kechi
it's a breaking down of haemoglobin and it's a chemical made by bacteria
Dev
Thnx Dev Raj.
Kechi
yup so any more
Dev
yes I sure do need more "Questions" & "Answers". I'm learning whole lot. Thnx.
Kechi
what is the greatest muscle of the body
Lungu Reply
gluteus maximus
ABDULLAH
pls!!! more "A&P" questions & answers. Thnx.
Kechi
Gluteus maximus
THE
Describe anatomy of cardiovascular system?
cardiovascular system is a group of organs coming together to perform the circulation of blood. The organs invoked are the heart and the blood vessels with blood being the tissue. The heart is a pump and it pumps oxygenated blood through the systemic circuit and deoxygenated blood through the pulmon
bernard
pulmonary circuit.
bernard
more A&P questions pls. Thnx.
Kechi
If an ANOVA yields a significant F value, you could rely on ________ to test significant differences between group means.
Dane Reply
what's ANOVA
Cassandra
analysis of variance
Blayne
plz what you mean with "ANOVA" first
Fatima
anova means analysis of variance, a statistical method in which the variation in a set of observations is divided into distinct components.
Blayne
M value ot test
ABDULLAH
What does it mean by M value ot test?
Orpha
formation of red blood cells
Biketi Reply
explain why... lower back pain in ovarian cancer
Srijoni Reply
we says that protoplasm is the living part of us How?
Muzamil Reply
is the leaving part of our cellular structure.
Eric
it is the leaving part of our blood cellular structure also
ABDULLAH
what is receptor?
Preity Reply
an organ or cell able to respond to light, heat, or other external stimulus and transmit a signal to a sensory nerve.
Jessi
Has anyone taken the first exam?
Sandra
yes
yahye
yes
Allan
hey what is the process after your food is swallowed? how long does it take to get to the stomache until it is released as waste?
Fednise Reply
that is such a broad question. as you begin to swallow its various doses down the alimentary canal that brings the food into your stomach.then depending on whether it's a protein carbohydrate fat that dictates what function takes place in your stomach. these are all steps of digestion.
Joseph
typo sorry it's peristalsis , wave-like projections that push food down your alimentary canal etc. digestion starts in your mouth ends in your large intestines (colon anus)
Joseph
some of the many processes of digestion include hydrolysis dehydration synthesis denaturation of proteins etc. you have to be more specific.
Joseph
there's many different contributing factors the how long it takes food to convert into waste. remember fats, triglycerides proteins and carbohydrates all breakdown two different monomers and structures. you should be looking up metabolic processes.
Joseph
depending how much fiber you have in your diet dictates how much water is brought to your intestines that has to do with excretion whether fiber is insoluble or soluble. this is an anatomy and physiology app. to simply say the stomach will empty its contents in 2 to 3 hours would do you a disservice
Joseph
can the study of anatomy relate to medical technologies
Lean Reply
yes
Khh
absolutely
Jessi
yes...
Sherif
how can I understand micro biology and anatomy better.
Cassandra
yes
Kevin
someone to help me understand glycogeneogenesis
abel
what are the major branches of the aorta?
Kevin
look youtube video
Jessi

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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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