Placenta: Structure, Functions, Hormones & MCQs in Biology

The placenta is an organ that is formed during pregnancy in the uterus of a female. The placenta is connected to the foetus by a tube-like structure called the umbilical cord. The placenta, through the umbilical cord, helps to provide nourishment and oxygen to the developing baby. It also helps in waste removal from the baby’s blood.

This Story also Contains

1. What is the Placenta?
2. Placenta Structure
3. Functions of the Placenta
4. Placental Barrier
5. Clinical Relevance of the Placenta
6. Recommended video on Placenta
7. MCQs on Placenta

The placenta is generally attached to the top, side, front or back of the uterus. If it gets attached anywhere in the lower area, it may block the passage, which acts as a passageway for the baby during parturition. If any severe condition happens, it causes a condition called placenta previa. The placenta is an important topic in the biology subject.

What is the Placenta?

The placenta is a vital organ that develops during pregnancy and acts as the interface between the mother and the fetus. In short, it takes over all the functions of the developing fetus, such as absorption of nutrients, elimination of waste products, and exchange of gases.

Placenta Structure

The placenta is a temporary organ that grows in the uterus during pregnancy. It anchors the fetus developing in utero to the uterine wall and furnishes the region for the exchange of nutrients, gases, and waste products between mother and fetus. The details are given below:

Chorionic Villus

• The placenta has many finger-like projections, called chorionic villi, which increase the surface area for exchange.

Maternal Blood Supply

• The placenta is richly supplied with maternal blood, which makes the transfer of oxygen and nutrients to the fetus easier.

Supply of Blood to the Fetus

• Blood vessels on the fetal side of the placenta take deoxygenated blood away from the fetus and return oxygenated blood.

Functions of the Placenta

The major functions of the placenta include the exchange of nutrients, gases, and waste products between the mother and fetus. The functions include:

Nutrient Transfer:

• The essential nutrients, like glucose, amino acids, and fatty acids, are passed on from the mother to the fetus through the placenta.

Exchanges of Gases:

• Oxygen is transferred from maternal blood to fetal blood, while carbon dioxide is removed from the fetus to the mother.

Waste Elimination:

• The placenta helps in the excretion of metabolic waste products from the fetal circulation.

Hormone Production:

• The placenta produces various hormones, hCG, progesterone, and estrogen, which play a vital role in maintaining pregnancy.

Placental Barrier

The placental barrier is necessary to filter out the substances that reach the foetus. The detailed explanation is given below:

Selective Permeability:

• The placenta acts as a barrier. It selectively permits the passage of certain substances while preventing most of the harmful agents.

Immune Function:

• The placenta protects the fetus from the maternal immunity and immune system, thereby preventing the fetus's rejection. It helps to protect the foetus from the maternal antibodies.

Clinical Relevance of the Placenta

The health of the placenta is essential for a healthy pregnancy. In conclusion, conditions such as placenta previa, placental abruption, and gestational diabetes are some conditions that may present risks to the mother and the fetus. During prenatal care, monitoring of the placental functioning should be essential.

Recommended video on Placenta

MCQs on Placenta

Q1. Despite the absence of definitive evidence regarding the cause of morning sickness, certain individuals believe that hormonal fluctuations, specifically the secretion of human chorionic gonadotropin (hCG), may contribute to these symptoms. Among the following options, which hormone changes exclusively occur during pregnancy?

Option 1: Estrogen production

Option 2: Progesterone production

Option 3: Reduction in prolactin levels by several folds.

Option 4: Significant rise in cortisol levels by several folds.

Correct answer: (4) Significant rise in cortisol levels by several folds.

Explanation:

Cortisol is a hormone produced by the adrenal glands and is involved in various physiological processes, including metabolism, immune response, and stress regulation. During pregnancy, the body undergoes significant changes, and hormonal fluctuations occur to support the growth and development of the fetus.

One of these changes is an increase in cortisol levels. The rise in cortisol during pregnancy is a natural response to the increased demands on the body and plays a role in regulating metabolism, managing stress, and supporting the developing fetus. Therefore, the significant rise in cortisol levels, as stated in option 4, is a hormone change that occurs exclusively during pregnancy.

Hence, the correct answer is Option (4) Significant rise in cortisol levels by several folds.

Q2. Which of the following is not the function of placenta?

Option 1: Facilitates removal of carbon dioxide and waste material from embryo

Option 2: Secretes oxytocin during parturition.

Option 3: Facilitates supply of oxygen and nutrients to embryo.

Option 4: Secretes estrogen

Correct answer: (2) Secretes oxytocin during parturition.

Explanation:

• The placenta facilitates the supply of oxygen and nutrients to the embryo and also the removal of carbon dioxide and excretory/waste materials produced by the embryo.

• The placenta is connected to the embryo through an umbilical cord which helps in the transport of substances to and from the embryo.

• The placenta also acts as an endocrine tissue and produces several hormones like human chorionic gonadotropin (hCG), human placental lactogen (hPL), estrogens, progestogens, etc.

Hence, the correct answer is option (2) Secretes oxytocin during parturition.

Q3. Which hormones are exclusively produced by the placenta, without involvement from the ovary in pregnant women?

Option 1: Prolactin, Estrogen

Option 2: hPL, Estrogen

Option 3: Progesterone , Estrogen

Option 4: hPL, Progesterone

Correct answer: (2)hPL, Estrogen.

Explanation:

Among the given options, hPL and Estrogen are the hormones produced exclusively by the placenta during pregnancy. These hormones play vital roles in maintaining the pregnancy, supporting fetal development, and regulating various physiological changes in the mother's body. It is important to note that while the placenta produces these hormones, the ovary also contributes to hormonal production during pregnancy, but these specific hormones mentioned are primarily synthesized by the placenta.

Hence, the correct answer is option (2) hPL, Estrogen.