Developmental Anatomy: Extraembryonic Membranes

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Questions and Answers

What structure is formed by the complex of cotyledons and caruncles?

Diffused placenta

Zonary placenta

Discoid placenta

Placentome (correct)

Which type of placenta retains all six layers intact?

Epitheliochorial (correct)

Endotheliochorial

Synepitheliochorial

Hemochorial

Which type of placenta is specifically found in carnivores such as cats and dogs?

Zonary

Epitheliochorial

Endotheliochorial (correct)

Hemochorial

In which type of placenta does only one maternal layer remain intact?

Endotheliochorial Signup and view all the answers

Which of the following species typically have a diffuse placenta?

Pigs and Horses Signup and view all the answers

Which type of placenta is characterized by a band of tissue surrounding the fetus?

Zonary placenta Signup and view all the answers

What term describes the contact sites formed by the maternal tissue in placentary anatomy?

Caruncles Signup and view all the answers

Which of the following layers would be absent in a hemochorial placenta?

Maternal connective tissue Signup and view all the answers

What distinguishes viviparous animals from oviparous animals?

They give birth to live young after internal development. Signup and view all the answers

Which extraembryonic membrane functions primarily in gas exchange and liquid waste collection?

Allantois Signup and view all the answers

What is a primary function of the amniotic sac?

Contains the embryo and protects it from injury. Signup and view all the answers

What is the role of the chorion in embryonic development?

Forms the fetal part of the placenta. Signup and view all the answers

Which statement accurately describes the yolk sac?

It serves as a nutrient supply in early development phases. Signup and view all the answers

What is the significance of the decidua in placentation?

It's the maternal part rich in blood vessels supplying oxygen and nutrients. Signup and view all the answers

Which extraembryonic membrane is involved in maintaining the fetus's body temperature?

Amnion Signup and view all the answers

How does the umbilical cord function in fetal development?

It connects the fetus to the maternal blood supply. Signup and view all the answers

What occurs during the implantation phase of mammalian embryonic development?

The blastocyst adheres and invades the uterine lining. Signup and view all the answers

What is the main characteristic of ovoviviparous animals?

They retain eggs that hatch inside the mother's body. Signup and view all the answers

What type of implantation involves the blastocyst becoming completely cut off from the uterine lumen?

Interstitial implantation Signup and view all the answers

Which type of implantation is commonly observed in rodents?

Eccentric implantation Signup and view all the answers

What is histotroph commonly referred to as?

Uterine milk Signup and view all the answers

Which of the following mammals lack a placenta?

Duckbilled platypus Signup and view all the answers

What term describes the vascular organ that develops inside the uterus of most pregnant mammals?

Placenta Signup and view all the answers

Which of the following structures is part of fetal membranes?

Allantoic endothelium Signup and view all the answers

What type of placentation involves the entire surface of the allantochorion participating in the formation of the placenta?

Diffuse Signup and view all the answers

Which type of nutrient absorption occurs through the allantochorion?

Hemotroph absorption Signup and view all the answers

Study Notes

Animal Reproductive Strategies

Oviparous: Animals that lay eggs; development occurs outside the mother's body.
Viviparous: Animals give birth to live young; embryos develop inside the mother, typically through a placenta.
Oviviparous: Eggs hatch inside the mother's body, resulting in live births.

Extraembryonic Membranes

Yolk Sac: Provides nutrients early in development, disappears later.
Allantois:
- Ventral outgrowth in reptiles, birds, and mammals.
- Vestigial in humans; contains umbilical arteries and veins.
- Functions in waste collection and gas exchange.
Amnion/Amniotic Sac:
- Surrounds the fetus, containing amniotic fluid.
- Protects the fetus, allows movement, prevents adherence, and maintains temperature.
Chorion:
- Outer trophoblast layer that forms the fetal part of the placenta.
- Involved in nutrient absorption, gas exchange, and hormone production.

Placenta Anatomy

Decidua: Maternal portion rich in blood vessels, expelled at birth.
Umbilical Cord/Urachus: Connects fetus to placenta; delivers oxygenated, nutrient-rich blood.

Embryonic Development and Implantation

Implantation: Phase where the blastocyst embeds into the endometrium of the uterus.
Endometrium: Inner uterine lining where implantation occurs.

Types of Implantation

Interstitial Implantation: Blastocyst implants within the uterine wall (e.g., primates, guinea pigs).
Centric/Superficial Implantation: Blastocyst enlarges to fill most of the uterine cavity (e.g., ungulates, carnivores).
Eccentric Implantation: Blastocyst lodges in a fold of the uterine lumen (e.g., rodents).

Early Nutrition

Embryotroph: Early nourishment comprising:
- Histotroph: Uterine milk for early nutrition before placenta is established.
- Hemotroph: Nutrition derived from maternal blood through allantochorion or vitellochorion.

Comparative Placentation

Placentation: The formation, type, and structure of placentas.
Most mammals have a placenta except monotremes (e.g., platypus) and marsupials (e.g., kangaroos).
Placenta Functions: Supplies oxygen/nutrients, removes waste, expelled after birth.

Types of Placenta Based on Appearance

Diffuse: Involves almost the entire placenta surface (e.g., pig, horse).
Cotyledonary: Features discrete attachment areas called cotyledons (e.g., ruminants).
Zonary: Forms a band of tissue around the fetus (e.g., cats, dogs).
Discoid: A single, disc-shaped placenta (e.g., humans, mice).

Types of Placenta Based on Morphology

Epitheliochorial: All six layers intact; no maternal tissue loss (e.g., horse, pig, cow).
Synepitheliochorial: Five layers intact; some maternal tissue loss (e.g., sheep, goat).
Endotheliochorial: Four layers intact; includes maternal endothelial cells (e.g., carnivores).
Hemochorial: Only three fetal layers intact; uterine blood vessels are exposed (e.g., rodents, primates, humans).

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Description

This quiz covers extraembryonic membranes and comparative placentation in animal reproductive strategies. Explore the differences between oviparous, viviparous, and oviviparous animals. Test your understanding of these concepts and their significance in developmental anatomy.