Ch. 24 - Pregnancy and Development

Question 1

Differentiate between an embryo and a foetus

Answer 1

Until the end of the 8th week of development, the offspring is called is called an embryo.

At this point, the basic structural form of the human body is recognisable.

Starting with the eighth week and lasting until birth, the offspring is called a foetus, with simple versions of all organs present.

These organs and other structures enlarge and become more specialised as the foetus develops.

Growth occurs rapidly during this period, with body proportions beginning to appear more like those of a normal infant.

Growth of the head begins to slow as growth of the body increases.

Question 2

Discuss the birth process

Answer 2

Birth process can begin hrs or days before the actual act of giving birth(Labour) occurs:

Stages of Labour.

• Rhythmic muscular contraction begin moving from the top to the bottom of the uterus.
• In normal position, the foetus’ head is forced against the cervix stimulating even stronger labour contractions.
• Positive feedback causes an increase in uterine contraction strength.
• Abdominal wall muscles contract, helping to force the foetus through the cervix and vagina.

Labour/childbirth is broken down into 3 stages:

1. Dilation of the cervix.
2. Expulsion of the Foetus(foetus emerges from the vagina/birth)
3. Placental Birth(the placenta is expelled from the uterus

Question 3

Explain the role of hormones in the birth process

Answer 3

Changing hormone levels in the foetus signal the placenta, initiating labour.

The placenta begins to produce prostaglandins, causing the uterus to contract, which pushes the foetus downwards.

Pressure from the baby’s head against the cervix signals the mothers hypothalamus, which in turn signals the posterior pituitary gland to release oxytocin.

Oxytocin (and prostaglandins) cause the uterus to continue contracting.

After delivery of the baby, and the placenta, oxytocin compresses the bleeding/damaged vascular tissues, caused by the seperation from the uterine wall.

Later, breast feeding will stimulate the posterior pituitary gland to release more oxytocin, contributing to returning the uterus to its original size.

Question 4

Labour contractions and hormones(diagram)

Answer 4

Question 5

3 stages of labour(diagram)

Answer 5

Question 6

Hormones stimulating labour(diagram)

Answer 6