Talk:Book - Embryology of the Pig 2

Gametes from Parent Generation

Fertilized Ovum

Somatic Cells

cells which continue to proliferate and by countless cell divisions and by divergent specialization give rise to the body. Vlth death of individual these cells cease to exist.'

gives rise to new individual*

Cleavage Divisions and indefinite number

of succeeding cell divisions during early growth of embryo

Certain cells become recognizable as

the Primordial Sex Cells

and become established in the gonads of the embryo.

Give rise to other units in the gonad similar to those indicated below.

Female Embryos become sexually differentiated

Male

In the growing ovary of embryo ovigerous cords and egg nests ~ arc formed

0og(

lonia

During youth odgonia remain quiescent.

In some cases oogonia 1 may be augmented in numbers during sexual maturity

Very slowly and only a few at a time oogonia grow

In the growing testes of the embryo seminiferous tubules are organized.

Spermatogonia

During youth spermatogonia remain relatively inactive.

y/V During sexual activity y-v spermatogonia augment their numbers by active division.

fVlmary Oocyte

Secondary Obeytes

/Body

rarely divides

Ootids Polar

In each maturation division Body all the stored food goes to one cell which is destined to be the ovum. The small cells receiving no yolk are called

S olar bodies, Thby never toone functional.

c/bmocx)Jb

Following the growth period of either spermatogonium or oSgonium. two maturation divisions rapidly succeed each other. In one of these divisions the species number of ohromosomes is reduced a half.

Mature

Ovum

Any spermatogonium may at any time cease dividing temporarily and grow into a

Primary Spermatocyte

which by first maturation division forms

Two Spermatocytes

second maturation division

Four Spermatids .

Without further divisions the spermatids beoome differentiated into

Spermla

Fertilisation of ovum by spermlum inltiatee development of new individual of filial generation*

(Speoios tniaiber of ohromosomee restored,)

Fig. 4. Chart outlining, for one generation, the history of the gametes and the germ plasm from which they are derived.