10 Questions
What is the function of the chalaza in an egg?
To maintain the orientation of the blastodisc for thermoregulation
What is the term for the region containing the nucleus in a mature ovum?
Nucleus-containing region
What is the purpose of the accessory layers in an egg?
To protect the egg cell from external damage
What is the term for the bulging yellow cells in the ovarian epithelium?
Ovarian follicle
Why is the egg difficult to beat?
Due to the presence of the chalaza
What is the term used to describe the cleaving blastodisc?
Blastoderm
What is unique about the oviduct in birds compared to other vertebrates?
It is relatively longer in proportion to the body
If an egg is to be fertilized, when must it occur?
Before the addition of accessory coverings
What is the purpose of injecting hormones into hen layers?
To hasten ovulation
What is a result of simultaneous ovulation in hen layers?
Two oocytes are released and receive shared accessory coverings
Study Notes
Ovarian Structure
- Mature eggs move towards the wall of the ovarian epithelium
- Ovarian follicle/ovum is characterized by bulging yellow large cells
Egg Composition
- Egg cell is surrounded by accessory layers for protection, including:
- Egg shell
- Egg white
- Thicker albumin
Mature Ovum Structure
- Contains three main regions:
- Yolk
- Region containing the nucleus
- Region containing the active cytoplasm
Egg White and Yolk
- Whitish, sticky jelly-like liquid structure outside the yellow yolk is called the white yolk
- Albumin is the substance attached to the yolk
Chalaza Function
- Chalaza ensures the blastodisc is always oriented on top for thermoregulation
- Allows the mother hen to sit on top of the egg, keeping the blastodisc in the correct position
Development of Chick Embryo
- An unfertilized cleaving blastodisc is called a blastoderm.
- The blastoderm will give rise to the chick embryo, but not the whole yolk.
Characteristics of Aves
- Aves have the longest oviduct relative to their body size among all vertebrates.
- The oviduct is divided into four regions: infundibular region, magnus region, shell region, and shell gland region.
Fertilization and Ovulation
- Fertilization of the egg must occur before the accessory coverings are added.
- In some cases, such as VitaLink PH, hen layers are injected with hormones to hasten ovulation, allowing two oocytes to be released simultaneously and receive accessory coverings together.
This quiz covers the structure and composition of ovarian follicles, including the ovum, yolk, and accessory layers.
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