• Developmental biology (Embryology)
Length of pregnancy ?
- 280 days (40weeks) after the onset of last normal menstrual period
- 266 (38weeks) after fertilization
46 chromosomes (diploid), DNA
20 000 genes
meiosis: germ cells gamets (haploid) : oocyte, sperms
fertilization- diploid again
Developmental biology (Embryology)
Early development (1.- 2. week)
importants terms: fertilization, zygote, cleavage, blastocyst,
implantation
Period of organogenesis = embryonic period (3.- 8. week)
- 3 germ layers: ectoderm, entoderm, mesoderm
- most major organs and organ systems are formed-Size of the embryo – CRL = crown rump length (mm)
importants terms: gastrulation, neurulation, neural crest, paraaxial
mesoderm, somite, intermedial mesoderm., lateral plate mesoderm,
Fetal period - from the 9th week
-maturation and rapid growth -Size of the fetus – CHL = crown heel length (mm)
• genetic background of development
• Genes and gene families: HOX, FGF,
FGFR, BMP, BMPR, PAX, SHH
Teratology - study of abnormalities of physiological development (birth defects).
The term stems from the Greek τέρας teras (genitive τέρατος teratos), meaning 'monster' or 'marvel',
and λόγος logos, meaning 'the word' or, more loosely, 'the study of' . (http://en.wikipedia.org/wiki/Teratology )
Thomas W. Sadler, Langman's Medical Embryology, LWW
Gastrulation – beginning of the 3rd week
Important tems: primitive streak, primitive node, epiblast, hypoblast
Invagination of epiblast 3 germ layers
Thomas W. Sadler, Langman's Medical Embryology, LWW
• 1/ ECTODERM
• EPIDERMIS [INCLUDING HAIR ,NAILS]
• NERVOUS SYSTEM
• NEURAL CREST AND ITS DERIVATIVES
•
•
• 2/MESODERM:
• CONNECTIVE TISSUE
• MUSCLES
• BONES
• CARDIOVASCULAR and LYMPHATIC system
• UROGENITAL system
SEROUS LINING (membranes) OF BODY CAVITIES(peritoneal, pleural)
•
• 3/ENDODERM :
• GUT (digestive) TUBE EPITHELIUM AND DERIVATIVES
• + LIVER and PANCREAS
• LUNG
Neural tube
Neural crest
Epidermis
NEURULATION
Scott F. Gilbert, Developmental Biology, Sinauer
Thomas W. Sadler, Langman's Medical Embryology, LWW
Thomas W. Sadler, Langman's Medical Embryology, LWW
Defects of neurulation anencephalus , spina bifida
Keith L. Moore, Before We Are Born: Essentials of Embryology and Birth Defects, Elsevier
MESODERM
• 1) paraxial mesoderm
• 2) intermediate mesoderm
• 3) lateral plate mesoderm
- parietal layer – body wall, serous mambranes
- visceral layer – gut, blood vessels
Thomas W. Sadler, Langman's Medical Embryology, LWW
angiogenesis – vessels form from blood islands
vasculogenesis – vessels sprout from existing ones
Thomas W. Sadler, Langman's Medical Embryology, LWW
Vessels formation
Endoderm derivatives
Pharyngeal (branchial ) arches – bars of mesenchymal tissue separated by clefts.
No.1,2,3,4-6. A lot of important head and neck structures are derivatives of them
Thomas W. Sadler, Langman's Medical Embryology, LWW
Human embryo (CRL 10 mm, 5th week)Thomas W. Sadler,
Langman's Medical
Embryology, LWW
Pharyngeal arches
Somites on each
side of neural tube
(see next slide)
Somites - segmented series of tissue blocks on each side of neural tube
from paraxial mesoderm
Thomas W. Sadler, Langman's Medical Embryology, LWW
Transverse section through somites
somiteneural
tube
chordalateral plate mesoderm -
somatic
lateral plate mesoderm -
splanchnic
Thomas W. Sadler, Langman's Medical Embryology, LWW
Each somite forms:
myotome
dermatome
sclerotome
Thomas W. Sadler,
Langman's Medical
Embryology, LWW
