Placenta Structure and Functions

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Questions and Answers

What is the typical duration of the third stage of labour?

30-45 minutes

20-30 minutes

15-20 minutes (correct)

5-10 minutes

What is the function of oxytocin in the birth process?

Increases oestrogen levels in the mother

Promotes contraction of the uterine wall (correct)

Stimulates the growth and development of mammary glands

Regulates the dilation of the cervix

What happens to the umbilical cord after birth?

It is left intact to allow for further growth

It is tied and cut, and the part connected to the baby will shrivel up and become the belly button (correct)

It is left attached to the placenta

It is removed and discarded

What is the primary function of the placenta during pregnancy?

To provide oxygen and nutrients to the baby Signup and view all the answers

What is the primary reason for a Caesarean section?

To reduce the risk of maternal and/or foetal distress Signup and view all the answers

What is the role of oestrogen in the development of mammary glands?

It stimulates the growth and development of milk glands and milk ducts Signup and view all the answers

What is the main function of the umbilical vein?

Carries oxygenated blood and nutrients from the mother to the foetus Signup and view all the answers

What happens to the placenta at the end of pregnancy?

It becomes less efficient, leading to the need for birth to occur Signup and view all the answers

What is the primary function of the placenta in regards to the foetus?

To provide the foetus with oxygen and nutrients Signup and view all the answers

What is the process by which the foetus, surrounding membrane, and placenta are expelled from the mother's body?

Parturition Signup and view all the answers

What is the purpose of the amniotic fluid surrounding the foetus?

To cushion and protect the foetus from external injury or impact Signup and view all the answers

What is the function of the umbilical arteries?

Carry waste products from the foetus to the mother's bloodstream Signup and view all the answers

What is the function of the yolk sac?

Forms the umbilical cord Signup and view all the answers

During what stage of pregnancy does the majority of differentiation occur?

Embryonic period Signup and view all the answers

What is the function of the trophoblast?

Relates to feeding and develops into the placenta Signup and view all the answers

What is the purpose of the placenta?

Supplies the fetus with oxygen and nutrients Signup and view all the answers

During what stage of pregnancy does the fetus receive antibodies from the mother?

Foetal period Signup and view all the answers

What is the function of the amnion?

Is a membrane that fills with fluid Signup and view all the answers

During what stage of pregnancy does the heart begin to beat?

Embryonic period Signup and view all the answers

What is the purpose of the umbilical cord?

All of the above Signup and view all the answers

What is the function of the villi in the placenta?

Grows into the endometrium to form the placenta Signup and view all the answers

During what stage of pregnancy does the fetus turn, with its head pointing towards the cervix?

Foetal period Signup and view all the answers

Study Notes

Labour and Birth

2-3 weeks prior to birth, the foetus moves into position, with the head pointing down towards the cervix
High levels of oestrogen in the mother's body cause the pituitary gland to secrete oxytocin, promoting uterine contractions
Stage 1 of labour: dilation of the cervix; myometrium starts contracting, becoming more frequent and intense, causing the cervix to dilate up to 10cm
At 10cm, the amniotic fluid is released, and the cervix is fully dilated
Stage 2: delivery of the baby; powerful contractions of the uterus and abdominal muscles push the baby out through the vagina, usually head first
Stage 3: expulsion of the placenta, which usually occurs within 20 minutes after birth and lasts for around 15 minutes

Birth Options

Vaginal birth: natural or assisted with medication
Caesarean section: surgical delivery, usually performed if there are complications and the mother and/or foetus are at risk

Mammary Glands

Produce milk; contain milk-secreting glands
Lactation: milk production stimulated by oestrogen and progesterone, which develop milk glands and ducts
Oxytocin promotes milk letdown

Placenta

Develops from chorion and villi that penetrate the endometrium
Villi provide a large surface area for exchange of substances with maternal blood supply
Functions:
- Oxygen and dissolved nutrients pass from mother to foetal blood
- Waste products pass from foetus to mother for excretion
- Maternal antibodies pass to foetus, providing passive immunity
- Acts as a barrier, preventing harmful substances from entering the foetus
- Produces progesterone and oestrogen, maintaining uterine changes during pregnancy
- Later in pregnancy, secretes relaxin, which relaxes joints and ligaments for delivery

Amnion and Amniotic Fluid

Amnion: membrane surrounding the embryo and foetus
Amniotic fluid: surrounds the foetus, protecting it from external injury and providing a medium for breathing and swallowing movements
Functions:
- Supports foetal development
- Cushions and protects the foetus
- Holds urine released by the foetus
- Regulates temperature and prevents dehydration

Umbilical Cord

Flexible cord connecting the foetus to the placenta
Contains two umbilical arteries and one umbilical vein
Umbilical arteries: carry waste from the foetus to the mother's bloodstream
Umbilical vein: carries oxygenated blood and nutrients from the mother to the foetus

Human Reproduction: Pregnancy and Birth

Copulation and Fertilization

Copulation: sexual intercourse, transferring sperm into the vagina
Fertilization: fusion of the sperm nucleus with the egg nucleus, forming a diploid zygote

Gestation (Pregnancy)

Time between conception and birth (280 days or 40 weeks)
Embryo and foetus develop in the uterus

Early Development (0-2 months)

Fertilization: fusion of sperm and egg nuclei
Blastocyst formation: morula develops into a hollow fluid-filled ball of cells
Implantation: blastocyst sinks into the endometrium

Early Development (3rd-8th week)

Formation of embryo and amnion
Yolk sac forms part of the umbilical cord
Trophoblast develops into the chorion, forming villi that penetrate the endometrium to form the placenta
Embryo develops into three layers: ectoderm, endoderm, and mesoderm

Later Development (Foetal period)

From week 9 to birth, the foetus grows rapidly
Bones ossify, subcutaneous tissue forms, and antibodies enter the foetus via the placenta
Foetus turns, with the head pointing towards the cervix

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Description

Learn about the structure and functions of the placenta, including the role of villi, capillary networks, and maternal blood supply in facilitating the exchange of substances between the mother and fetus. Understand the importance of the placenta in providing oxygen and essential nutrients to the fetus.