Model Answer
0 min readIntroduction
The placenta is a temporary physiological connection between the mother and developing fetus, providing oxygen, nutrients, and removing waste products. It also plays a crucial role in hormone production and immune protection. Its structure varies significantly across mammalian species, leading to different classifications. Understanding these variations is vital for comparative anatomy and reproductive physiology. Mammalian placentas are broadly categorized based on the extent of maternal and fetal tissue contact and the distribution of chorionic villi.
Types of Placenta
Mammalian placentas are classified into several types:
- Diffuse Placenta: Found in equines (horses, zebras). Chorionic villi are scattered throughout the uterine lining, lacking distinct cotyledons.
- Cotyledonary Placenta: Present in ruminants (cows, sheep, goats). The chorion forms distinct, rounded areas called cotyledons that attach to the caruncles of the uterus.
- Discoid Placenta: Characterized by a single, circular disc-shaped placenta, found in carnivores (dogs, cats) and primates (humans).
- Labyrinthine Placenta: Found in rodents (rats, mice). It has a complex, folded structure resembling a labyrinth, maximizing surface area for exchange.
| Placenta Type | Distribution of Villi | Mammalian Example |
|---|---|---|
| Diffuse | Scattered | Horse |
| Cotyledonary | Cotyledons & Caruncles | Cow |
| Discoid | Single disc | Human |
| Labyrinthine | Complex folds | Rat |
These variations reflect adaptations to different reproductive strategies and fetal development rates.
Conclusion
In conclusion, the placenta exhibits remarkable diversity across mammals, reflecting evolutionary adaptations to optimize nutrient and gas exchange. The classification into diffuse, cotyledonary, discoid, and labyrinthine types, based on structural features, provides a framework for understanding placental function and its significance in mammalian reproduction. Further research continues to refine our understanding of placental development and its impact on offspring health.
Answer Length
This is a comprehensive model answer for learning purposes and may exceed the word limit. In the exam, always adhere to the prescribed word count.