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A woman has conceived and implantation h...

A woman has conceived and implantation has occurred in her uterus. Explain the sequence of changes upto parturition which take place within her body.

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After implantation the chorionic villi and uterine tissue become interdigitated to form placenta. Placenta facilitates supply of `O_2` and nutrients to the embryo and removes `CO_2` and excretory materials produced by the embryo. Increased production of hormones like estrogen, progesterone, prolactin are essential for supporting foetal growth, metabolic changes in the mother and maintenance of pregnancy. The inner cell mass differentiates into three distinct germ layers mesoderm, ectoderm and endoderm) which given rise to all tissues (organs) in adults After one month of pregnancy the embryo's heart is formed By the end of the second month of pregnancy the foetus develops limbs and digits. By the end of 12 weeks (first trimester) most of the major organ systems are formed.By the end of 24 weeks (second trimester) the body is covered with fine hair. eyelids separate and eyelashes are formed. The signals for parturition originate from the fully developed foetus and the placenta which induce mild uterine contractions called foetal ejection reflex The triggers release of oxytocin from maternal pituitary along with stimulatory reflex resulting in stronger contractions leads to parturition.
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Knowledge Check

  • If the composition of the system does not change with time, the system is said to be in chemical equilibrium. itis the state in which net reaction of a system Is zero. in another words we can say that in reversible reactions, a stage is reached when the rate of transformation of reactants into products equals the rate of transformation of products into reactants. At this stage, the composition of reactants and products does not change with time. This does not mean that the reaction has ceased, as both reverse and forward reactions are still taking place but with equal speed. Such equilibria are called dynamic equilibria, Let us consider a reaction of the type A_(g) + B_(g) iff C_(g) + D_(g) K_c = ([C][D])/([A][B]) where K_c is equilibrium constant when the ratio of the concentrations of the product to reactants K_p = (P_C xx P_O)/(P_A xx P_B) where K_P is the equilibrium constant for the ratio of partial pressure of products to reactants. The relation between K_P and K_C is as follows K_P = K_C(RT)^(Deltan) The mass ratio of steam and hydrogen is found to be 1:2 at equilibrium. 3 Fe(s) + 4H_2O(g) iff Fe_3O_4(s) + 4H_2(g) The value of equilibrium constant (K_C) for the above reaction is

    A
    `3.05 xx 10^3`
    B
    `1.05 xx 10^5`
    C
    `0.75 xx 10^2`
    D
    `2.42 xx 10^7`

  • If the composition of the system does not change with time, the system is said to be in chemical equilibrium. itis the state in which net reaction of a system Is zero. in another words we can say that in reversible reactions, a stage is reached when the rate of transformation of reactants into products equals the rate of transformation of products into reactants. At this stage, the composition of reactants and products does not change with time. This does not mean that the reaction has ceased, as both reverse and forward reactions are still taking place but with equal speed. Such equilibria are called dynamic equilibria, Let us consider a reaction of the type A_(g) + B_(g) iff C_(g) + D_(g) K_c = ([C][D])/([A][B]) where K_c is equilibrium constant when the ratio of the concentrations of the product to reactants K_p = (P_C xx P_O)/(P_A xx P_B) where K_P is the equilibrium constant for the ratio of partial pressure of products to reactants. The relation between K_P and K_C is as follows K_P = K_C(RT)^(Deltan) For the reaction NH_2COONH_4(s) iff 2NH_3(g) + CO_2(g) The equilibrium constant K_p = 2.9 xx 10^-5 atm^3 . The total pressure of gases at equilibrium when 1 mole of reactant was heated will be

    A
    0.0194 atm
    B
    0.0388 atm
    C
    0.0580 atm
    D
    0.0667 atm

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