Development of the Skeletal System in Embryology

All about the Development of the Skelatal System

1. DEVELOPMENT
OF THE
SKELETAL
SYSTEM
EMBRYOLOGY
EDHANE JUSTY DAGUPLO | BIO 3B

2. Outline
1. Introduction to the Skeletal System and its functions
2. Two types of Ossification
Endochondral Ossification
Intramembranous Ossification
3. Joint Formation
4. Development of the Skeleton
Axial Skeleton
Cranium
Vertebrae
Axial Bones
Appendicular Bones
5. Clinical Relevances and Birth Defects
TODAY'S DISCUSSION

3. QUESTION!
Which germ layer develops into the skeletal
system?
MESODERM
ECTODERM
ENDODERM

4. QUESTION!
Which germ layer develops into the skeletal
system?
MESODERM
ECTODERM
ENDODERM

5. INTRODUCTION
The skeletal system is the body system composed of bones and cartilage. The skeletal
system is the organ system that provides an internal framework for the human body.
It develops from the mesenchymal, which is Mesoderm in origin.
Chondroblasts
Osteoblasts
Fibrolasts

6. FUNCTIONS OF THE SKELETAL
SYSTEM
The skeletal system has many different functions that are necessary for human
survival.
supports the body
facilitates movement
protects internal organs
produces blood cells
stores and releases minerals and fat

7. TWO TYPES
OF
OSSIFICATION
A collection of mesenchymal cells
may group together and become
tightly packed (condensed), forming a
template for a future bone.
The formation of bones by
osteoblasts is called OSSIFICATION
Endochondral ossification
Intramembranous
ossification
An area of mesenchyme may form a
hollow sleeve roughly in the shape of
the future bone.

8. TWO TYPES OF OSSIFICATION
A collection of mesenchymal cells may group together and become
tightly packed (condensed), forming a template for a future bone.
Endochondral ossification

9. TWO TYPES OF OSSIFICATION
A collection of mesenchymal cells may group together and become
tightly packed (condensed), forming a template for a future bone.
Endochondral ossification

10. TWO TYPES
OF
OSSIFICATION
A collection of mesenchymal cells
may group together and become
tightly packed (condensed), forming
a template for a future bone.
The formation of bones by
osteoblasts is called OSSIFICATION
Endochondral ossification
Intramembranous
ossification
An area of mesenchyme may form a
hollow sleeve roughly in the shape of
the future bone.

11. TWO TYPES OF OSSIFICATION
An area of mesenchyme may form a hollow sleeve roughly in the shape of the future bone.
Intramembranous ossification

12. TWO TYPES OF OSSIFICATION
Intramembranous ossification
At birth, the skull and
clavicles are not fully
ossified nor are the
sutures of the skull
closed.

13. Fibrous, cartilaginous, and synovial joints also
develop from mesenchyme from 6 weeks onwards.
JOINT FORMATION
CHONDROCYTES -----> HYALINE CARTILAGE,
FIBROCARTILAGE JOINT MAY ALSO FORM, AS SEEN IN SOME MIDLINE JOINTS, FOR
EXAMPLE, THE PUBIC SYMPHYSIS.

14. Fibrous, cartilaginous, and synovial joints also
develop from mesenchyme from 6 weeks onwards.
JOINT FORMATION
EDGES OF THIS CENTRAL CONNECTIVE TISSUE MASS BECOME THE SYNOVIAL CELLS
THE CENTRAL CONNECTIVE TISSUE MASS ALSO FORMS MENISCI AND INTERNAL JOINT
LIGAMENTS SUCH AS THE CRUCIATE LIGAMENTS.

15. DEVELOPMENT OF THE SKELETON
Cells for the developing skeleton come from a variety of sources.
Somites and the subdivision of the Sclerotome - Joined by contributions from the
somatic mesoderm and migrating neural crest cells.
Development of the skeleton can be split into two parts
Axial skeleton
Appendicular skeleton of the limbs.

16. Neurocranium
DAY 27 TO BIRTH
AXIAL SKELETON - CRANIUM, VERTEBRAL COLUMN, RIBS AND STERNUM
CRANIUM
NEUROCRANIUM
VISCEROCRANIUM
Occipital somites and neural crest fuse
and ossify forming:
1. Sphenoid
2. Ethmoid
3. Occipital bones and the petrous part
of the temporal bone

17. Neurocranium
DAY 27 TO BIRTH
AXIAL SKELETON - CRANIUM, VERTEBRAL COLUMN, RIBS AND STERNUM
CRANIUM
NEUROCRANIUM
VISCEROCRANIUM
The parietal and frontal bones form from
the membranous part of the neurocranium
The membranous parts ossify into flat
bones and are connected by connective
tissue sutures.

18. Neurocranium
DAY 27 TO BIRTH
AXIAL SKELETON - CRANIUM, VERTEBRAL COLUMN, RIBS AND STERNUM
CRANIUM
NEUROCRANIUM
VISCEROCRANIUM
Fontanelle - Where more than two bones
meet in the foetal skull. Occurs where the
frontal and parietal bone meets,

19. CRANIUM
NEUROCRANIUM
VISCEROCRANIUM
Viscerocranium
DAY 27 TO BIRTH
AXIAL SKELETON - CRANIUM, VERTEBRAL COLUMN, RIBS AND STERNUM
Cartilaginous - forms the stapes, malleus and
incus bones of the middle ear, and the hyoid
bone and laryngeal cartilages.
Membranous - squamous part of the temporal
bone, the maxilla, mandible and zygomatic
bones
has

20. Vertebrae
WEEK 4
AXIAL SKELETON - CRANIUM, VERTEBRAL COLUMN, RIBS AND STERNUM
The vertebral column developed from
the sclerotome compartment of the
somite

21. Vertebrae
WEEK 4
AXIAL SKELETON - CRANIUM, VERTEBRAL COLUMN, RIBS AND STERNUM
The vertebral column developed from the sclerotome compartment of the somite

22. Axial Bones (Ribs and Sternum)
AXIAL SKELETON - CRANIUM, VERTEBRAL COLUMN, RIBS AND STERNUM
RIbs form from the sclerotome
Sternum is from somatic mesoderm

23. Appendicular Bones
APPENDICULAR SKELETON OF THE LIMBS
Endochondral ossification of the long bones begins at
the end of week 7.

24. Appendicular Bones
APPENDICULAR SKELETON OF THE LIMBS
Ossification of the diaphysis of most long bones is
completed by birth, and secondary centers of ossification
appear in the first few years of life within the epiphyses

25. Appendicular Bones
APPENDICULAR SKELETON OF THE LIMBS
the cartilaginous growth plate (or epiphyseal plate)
remains as a region of continuing endochondral
ossification.

26. Pregnant women require higher quantities of calcium and phosphorous due to
fetal and bone development.
CLINICAL RELEVANCE
Pregnancy and lactation can cause a 3-10%
decrease in maternal bone density, which
recovers after weaning.

27. Vitamin D is required for calcium absorption across the gut.
CLINICAL RELEVANCE
Lack of vitamin D leads to
deformities such as bowed legs and
curvature of the spine. This is
called rickets

28. CRANIOSYNOSTOSIS
CLINICAL RELEVANCE
Early closure of cranial sutures, causing an
abnormally shaped head. This is a feature of over
100 genetic syndromes including forms of
dwarfism. It may also result in underdevelopment
of the facial area.

29. CRANIAL SKELETAL MALFORMATIONS
CLINICAL RELEVANCE
Treacher Collins Syndrome Robin Sequence Syndrome

30. CRANIAL SKELETAL MALFORMATIONS
CLINICAL RELEVANCE
DiGeorge Syndrome

31. VERTEBRAE MALFORMATIONS
CLINICAL RELEVANCE
Spina Bifida Occulta Spina Bifida Cystica
Spina Bifida - failure of the vertebral arches to fuse in the lumbosacral region.

32. VERTEBRAE MALFORMATIONS
CLINICAL RELEVANCE
Scoliosis Klippel-Feil Syndrome
Spina Bifida - failure of the vertebral arches to fuse in the lumbosacral region.

33. THANK
YOU!
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