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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

name the 5 layers of skin
Monika Reply
stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, stratum corneum
those are the layers of epidermis,, then we have the dermis which has got two layers that is papillary dermis and reticular dermis.. beneath the dermis we have the hypodermis( subcutaneous layer) which is not considered as a layer of skin
what's a feedback
ivhil Reply
is the information or comment about something that one have done
may be you mean negative or positive feedback mechanism... in general, they mean body response its changes by hormones
what is endocrin?
Asim Reply
why should there be an inhibition to the process of gastric production in the intestinal phase
endocrine is a system through which the secretions of cell directly poured into blood.
why should there be an inhibition to the process of gastric production in the intestinal
Gloria Reply
what is a stimuli
Emily Reply
environment factor that cause a cell to respond
name the two types of melanin
Laila Reply
deference between RNA and DNA
.DNA stands for Deoxyribonucleic Acid. The sugar portion of DNA is 2-Deoxyribose.RNA stands for Ribonucleic Acid.  The sugar portion of RNA is Ribose.2.The helix geometry of DNA is of B-Form (A or Z also present).The helix geometry of RNA is of A-Form.3.DNA is a double-stranded molecule consisting o
DNA consists of nucleotide but RNA consists of nucleoside DNA is double standard but RNA is single standard.In DNA at the nitrogen bases adinine,guanine,cytocin and thymine is present but in case of RNA instead of thymine uracil is present.
what are rdna
what is a heart
walker Reply
A heart is an organ in the circulatory system that pumps blood throughout the systemic regions
what is anatomy
Anatomy is the study of internal and external structures and the relationship among body parts. (the study of structure).
what is the physiology of the heart
guys help me with a pathophysiology of asthma
asthma is a lungs related disorder in which there is difficulty in breathing due to some allergic factors, their is inflamation of alveoli of respiratory part of lungs.also decreases the surface area.
what is meaning of brain strock and its types?
the pathophysiology of asthma is complex and involves airway inflammation and bronchial hyperresponsiveness pathogenesis of asthma
skin infection please explain
Hamza Reply
what is malignant melanoma
Akon Reply
cancerous cells 🙄
yes benign is non-cancerous malignant is cancerous.
that's a simple way of explaining it however you're different processes like mitosis etc a person can be at risk for developing cancer etc
you can tell by an unusual growth of a mole, or change in size coloration with melanoma. which is abnormal growth of your squamous cells.
Types of wandering connective tissues
Hassan Reply
what are the meaning of skin
study of external structure of human body is known as anatomy
what is Tau?
Vicki Reply
what is sliva
Saqlain Reply
what is gross
Kiran Reply

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