Essay 4

Do not memorise these answers! These are guidelines. Be creative, devise your own expression and organisation! You can elaborate on the points in your own language.
Remember that there is no 'perfect' answer - a little shortfall in content is easily compensated by presentation.
You should aim at writing an essay in this examination in approximately 20 minutes.

The "descent" of the gonads.

Key features : The bulk of gonadal tissue comes from the intermediate mesoderm. The germ cells are endodermal and migrate into the intermediate mesoderm. The gonadal tissue descends from the lower thoracic-lumbar region to its final destination.

The descent of the gonad is controlled by a connective tissue structure called the gubernaculum ("the little governor"). In both sexes the caudal end of the gubernaculum is attached to the tissue around the external genitals (scrotum in the male, labia majora in the female).

In the male the gubernaculum shortens completely, dragging the testis into the scrotum. In the female it remains longer, and is represented by fibrous cords - ligament of the ovary connecting the ovary to the uterus, and the round ligament which passes from the uterus to the labium majus through the inguinal canal.

The descending gonads carry with them their arteries, veins, lymphatics and nerves. Thus the gonadal arteries are paired branches of the aorta, the veins drain into the inferior vena cava (indirectly through the renal vein on the left side) and the lymphatics drain into lymph nodes lateral to the aorta.