La 20 de saptamani de sarcina, fatul masoara acum intre 15,2 cm si 15,9 cm de la cap pana la sold si cantareste aproximativ 255 g. Picioarele au aproximativ 3 cm lungime. In acest stadiu, fatul are aproximativ lungimea unei banane si greutatea a doua banane.
Vernix caseosa continua sa se dezvolte si sa acopere intregul corp. Aceasta substanta alba, uleioasa, protejeaza fatul de efectele imersiunii prelungite in lichidul amniotic si, de asemenea, ajuta la procesul nasterii.
Frecventa inghititurilor creste, pregatind sistemul digestiv pentru perioada postpartum. Cand lichidul amniotic este inghitit, fatul este capabil sa simta aromele alimentelor pe care le consuma mama.
Dezvoltarea musculara continua intr-un ritm rapid. Aceasta perioada a sarcinii este marcata de cea mai mare activitate fetala datorita dezvoltarii musculaturii scheletice ce permite miscari complexe si datorita cantitatii mari de lichid amniotic si spatiului disponibil in uter.
Creierul se dezvolta si se formeaza din ce in ce mai multe celule nervoase, aproximativ 200.000 de celule cerebrale fiind create in fiecare minut. Pentru ca creierul sa poata creste in acest ritm, oasele craniene nu se unesc decat mai tarziu si prezinta spatii numite fontanele. Acest lucru ajuta, de asemenea, copilul in timpul nasterii. Exista doua puncte deschise, fontanela posterioara se inchide in jurul a 6-8 saptamani, iar fontanela anterioara pana la varsta de 2 ani. Conexiunile neuronale dintre creier si restul corpului sunt complet functional dupa 18 saptamani. In plus, doua structuri cerebrale importante pentru procesarea durerii includ diencefalul si talamusul. Pana la mijlocul sarcinii, mai multe structuri ale creierului incep sa capete o forma recognoscibila. In jurul saptamanii 20, hipocampul, o regiune centrala a memoriei, incepe sa semene cu structura sa adulta. In acelasi timp, apar asimetrii subtile intre emisferele creierului, cu o crestere suplimentara in regiunile care vor procesa ulterior limbajul. Cortexul cerebral se organizeaza, de asemenea, rapid.
La 20 de saptamani de sarcina, pielea a dezvoltat foliculi de par si glande sudoripare timpurii.
Desi pleoapele sunt lipite intre 10 si 22 de saptamani, ochii continua sa se dezvolte. Partea din spate a ochiului, numita retina, care transforma lumina in semnale neuronale, este stratificata, fiecare strat avand o functie diferita. Centrul ochiului se maturizeaza inaintea marginilor exterioare.
La 20 de saptamani, corzile vocale vibreaza deja in timp ce fatul imita plansul in uterul mamei. Uneori fatul deschide gura inainte de a-si aduce mainile catre aceasta, anticipandu-si propriile miscari.
Pana in saptamana 20, structurile din spatele sistemelor senzoriale sunt dezvoltate, chiar daca nu sunt inca pe deplin operationale. Limba continua sa dezvolte papilele gustative, iar lichidul amniotic se deplaseaza prin nasul fetal, permitand mirosurilor sa interactioneze cu neuronii receptori olfactivi.
Canalul auditiv este deschis pana la 20 de saptamani, iar majoritatea structurilor pentru detectarea sunetului sunt complet formate. Pana la 20 - 21 de saptamani, aproximativ jumatate dintre copiii nenascuti raspund la un sunet puternic cu o modificare a ritmului cardiac. Aceste reactii la sunetele externe arata ca fatul este constient de mediul extern.
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Week 20 of pregnancy (Days 140-146), HCA Healthcare UK official website
Weeks 19 & 20, Charlotte Lozier Institute official website
Pregnancy Week 20, MAM Babyartikel GmbH official website
Autor: Farmacist Marza Andreea Simona
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