The process of
prenatal development occurs in three main stages and they are listed in order;
<span>1. </span>Germinal Stage - begins at conception when the
sperm and egg cell joined in one of the two fallopian tubes.
<span>2. </span>Embryonic Stage - begins at the beginning of
the third week after conception. This stage plays an important role in the
development of the brain.
<span>3. </span>Fetal Stage - begins during the ninth week
and lasts until birth.
The ribs articulate with the (a) thoracic vertebrae.
There exists 12 pairs of ribs. Each rib is a thin flat bone attached dorsally to the vertebral column as well as ventrally to the sternum.
First seven pairs of ribs are known as 'true ribs'. They articulate with the thoracic vertebrae dorsally and are ventrally attached to the sternum by means of of hyaline cartilage.
The 8th, 9th as well as 10th pairs of ribs do not articulate directly with the sternum but unite with the 7th rib with the support of hyaline cartilage. These are called 'false ribs'.
Remaining two pairs i.e. the 11th and 12th pairs of ribs are not attached ventrally and are thus, termed as 'floating ribs'.
To learn more about thoracic vertebrae here
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the private area of a man produces sperm
Answer:
d) topographical variation
Explanation:
