Placenta (Structure, types and functions of placenta) | Zoology Optional Notes for UPSC PDF Download

Definition and Characteristics

1. Definition of Placenta:

   • The placenta is a transient organ crucial for nourishing and safeguarding the fetus during pregnancy. It develops alongside the fetus and is expelled during childbirth.
   • It is colloquially known as the "afterbirth" due to its expulsion after delivery.

2. Transient Circulatory Organ:

   • The placenta, unique to mammals, serves as a temporary circulatory organ connecting the fetal and maternal systems during pregnancy.
   • The umbilical cord links the fetus to the placenta, facilitating the transfer of materials.

3. Attachment to Uterus:

   • The placenta is typically attached to various parts of the uterus, including the top, bottom, side, front, or back.
   • An abnormal attachment, such as in placenta previa, can pose serious complications during pregnancy.

Clear all your UPSC doubts with EduRev Join for Free

Join for Free

Structure of Placenta

1. Finger-like Projections (Chorionic Villi):

   • Chorionic villi, projections from the chorion's outer surface, infiltrate the uterine tissue, forming the placenta.
   • This connective tissue serves as both embryonic and maternal, facilitating material exchange.

2. Role in Nutrient Exchange:

   • The developing embryo receives oxygen and nutrients from the mother through the placenta.
   • Simultaneously, waste products like carbon dioxide and nitrogenous waste are eliminated.

Types of Placenta

1. Based on Embryonic Tissue Involvement:

   • Yolk-Sac Placenta and Chorio-Allantok Placenta are classified based on the embryonic tissue's interaction with the uterine wall.

2. Villi Distribution:

   • Diffused, Cotyledonary, Zonary, and Discoidal Placenta exhibit variations in the distribution and formation of villi.

3. Villi's Relationship with Uterine Wall:

   • Deciduate and Indeciduate (Adeciduate) Placenta differ in the degree of villi attachment to the uterine wall and their persistence after birth.

4. Degree of Tissue Involvement:

   • Epitheliochorial, Haemochorial, Haemoendothelial, and Syndesmochorial Placenta are distinguished by the involvement of fetal and maternal tissues.

Download the notes Placenta (Structure, types and functions of placenta)

Download as PDF

Download as PDF

Function of the Placenta

1. Life Support Functions:

   • Gas exchange, nutrient acquisition, and waste removal are essential functions ensuring the fetus's well-being.

2. Barrier and Immunological Functions:

   • The placenta acts as a barrier, protecting the fetus from infections and filtering out potential threats.
   • Immunological protection is provided through the transfer of antibodies from the mother to the fetus.

3. Endocrine Function:

   • The placenta secretes hormones (estrogen, progesterone, HCG), maintaining a pregnancy-ready state in the mother.

Take a Practice Test Test yourself on topics from UPSC exam

Practice Now

Practice Now

Purpose of the Placenta

1. Nutrition and Storage:

   • Nutrient transfer from maternal to fetal blood, storage of glycogen and nutrients before liver development.

2. Endocrine Secretion:

   • The placenta functions as an endocrine gland, secreting hormones vital for pregnancy.

3. Protein Digestion and Excretion:

   • Trophoblasts in the placenta break down proteins for fetal circulation, and it aids in excreting nitrogenous wastes.

4. Respiration and Barrier Function:

   • Oxygen and carbon dioxide exchange between fetal and maternal blood, and the placenta acts as a barrier against harmful substances.

Understanding the multifaceted roles and structures of the placenta is crucial for comprehending its significance in fetal development and maternal-fetal interactions.