Histogenesis 151 Course 5: Cells and tissue development

Course 5: Development 137 Case report: Thalidomide 138 Basic morphogenetic processes 139 Regeneration and reparation 140 Female reproductive system 142 Gametogenesis and fertilization 144 Genetic determination of the sex 145 Signalization in development 146 Blastogenesis, notogenesis 149 Notogenesis, neurulation 150 Embryonic period 151 Histogenesis 152 Human reproductive genetics 153 Developmental toxicology 154 Ageing 141 Female reproductive system 143 Male reproductive system 147 Extraembryonic organs 148 Early embryonic development, chick

Aim histogenesis – the origin and development of specialised tissues and organs – the derivates of: ectoderm mesoderm endoderm

blastogenesis embryonic period fetal period Histogenesis, organogenesis

Ontogenesis mechanisms operate…at different levels cells - differentiation cell populations - morphogenesis - structure development cell populations set - morphogenetic system – realizes structure and function programme in organ or part of the body – basic morphogenetic processes

1. Cell level – differentiation – mesenchymal cell mesenchymal cell chondroblastlipoblastfibroblastosteoblastmyoblast cartilagefat connective tissue, ligaments, tendons bonemuscle endothelium blood cells hemocytoblast

Cell level – differentiation – neuroepithelim

2. Cell populations level development of structures/ organs - morphogenesis 1. induction – one cell population induces the change of the fate in another cell population epithelial-mesenchymal interactions examples: limbs, lens, nephrons, teeth cross-talk 2. cell-signalling, signalising cell x target cell (must be sensitive to this signal) paracrine interactions, contact interactions

induction neuroectoderm / surface ectoderm – lens placode

Induction in gonad – indifferent stage induction – primordial germ cells/ testes, ovary induction – coelomic epithelium / mesenchyme

3. Morphogenetic systems level = group of cell populations relize the developmental programme basic morphogenetic processes - 4 processes play out at the cell population level to essentially create the final organism proliferation migration asociation programmed cell death - apoptosis

Morphogenetic system level neural tube differentiation in CNS development

Histogenesis EPIBLAST is the maternal of 3 germ layers ectoderm and endoderm are epithelia Expression CAM + mesoderm is connective tissue – primary mesenchyme No Expression CAM -

Origin of 3 germ layers

Germ layers derivates nervous systeme senses connectives skin circulatory s. hematopoesis, immune s. endocrine s. Epiblast ectoderm mesoderm endoderm urogenital sytem mesenchyme digestive s. respiratory s

Ectoderm and its differentiation 1.neuroectoderm (neural tube a neural crest) 2. surface ectoderm 1.neuroectoderm 2. surface ectoderm neuroectoderm: NT, neural crest placodes surface ectoderm: epidermis

Neural tube – region of the future brain (segmentation- neuromers- brain vesicles)

induction neuroectoderm / surface ectoderm placodes - otic placodes and lens placodes

Neuroectoderm - neural crest – definitive derivates connectives, cartilage, bone, dermis of the head cranial nerves ganglia odontoblasts, Schwann cells melanocytes, C-cells of thyroid autonomic ganglia adrenal medulla

Ectoderm derivates mediate the contact between body and outer environment CNS PNS sensory epithelium of the ear, nose, eye epidermis and its derivates – hairs, nails glands of the skin, mammary gland hypophysis enamel

Endoderm and its differentiation yolk sac roof and wall, primitive gut

Endoderm-lined cavity and its position during cephalo-caudal folding sagittal midline section

Endoderm and its derivates gastrointestinal tract – epithelium respiratory sytem – epithelium parenchyme of the liver, pancreas, thyroid reticular stroma of tonsils and thymus epithelium of salivary glands epithelium of urinary bladder, urethra epitel of middle ear and Eustachian tube

Mesoderm and its early differentiation axial, paraxial, intermediate, lateral

Mesoderm – mesenchyme – embryonic connective tissue

Somite differentiation sclerotome, dermatome, myotome epiteloid arrangement of somite sclerotome – connectives coating spinal cord dorsolateral cells migrate to the limb bud - muscles Dorsomedial cells – myotome –trunk muscles dorsally - dermatom – beneath ectoderm – dermis in the skin

Somites, 42 – 44 pairs. 1.pair in occipital region, 20ED Material: paraxial mesoderm Segmentation: Notch, WNT, segmentation genes Retinoic acid, FGF8, cranio-caudal gradient S

Intermediate mesoderm – derivates urogenital sytem in cervical, and thoracal region – segmented in nephrotomes abdominal – nefrogenic blastema

Excretory units of kidney and gonad primordium

Lateral mesoderm – splanchnic/ splanchnopleura and somatic/ somatopleura

splanchnopleura – wall of gut (CT, muscle) somatopleura – serous membrane – inner lining of coelom transversal section 3week4week

Mesoderm and its derivates connectives (connective tissue proper, cartilage, bone) blood mesothel and endothel– the only epithelia kidneys gonads mesothel – simple squamous epithel of the visceral peritoneum /splanchnopleura in peritoneal cavity

Tissues family tree