Developmental Biology (Embryology)

Home , Intermediate mesoderm, Primitive node

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 Thomas W. Sadler, Langman's Medical Embryology, LWW 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 ) 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 NEURULATION

Neural tube Neural crest Epidermis

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 Vessels formation vasculogenesis – vessels sprout from existing ones

Endoderm derivatives

Thomas W. Sadler, Langman's Medical Embryology, LWW 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 Pharyngeal arches

Somites on each side of neural tube (see next slide)

Thomas W. Sadler, Human embryo (CRL 10 mm, 5th week) Langman's Medical Embryology, LWW Somites - segmented series of tissue blocks on each side of neural tube from paraxial mesoderm

Thomas W. Sadler, Langman's Medical Embryology, LWW neural somite tube

lateral plate mesoderm - chorda lateral plate mesoderm - somatic splanchnic

Transverse section through somites

Thomas W. Sadler, Langman's Medical Embryology, LWW Each somite forms: myotome dermatome sclerotome

Thomas W. Sadler, Langman's Medical Embryology, LWW