Eggs Flashcards
What is the general purpose of eggs?
reproduction
What percent of the egg is comprised of the shell/shell membranes?
11%
What percent of the egg is composed of yolk?
31%
What percent of the egg is composed of albumen?
58%
What are some differences between bird eggs and mammalian eggs?
They differ in nutrient availability. Bird eggs are also larger than mammalian eggs.
What does altricial mean?
Altricial means that the offspring requires a large amount of parental care after hatching.
ex. baby birds
What does precocial mean?
The offspring require little parental care after hatching, and are able to function independently.
ex. chicks
What is the difference in egg content between altricial and precocial birds?
Altricial bird eggs tend to have less yolk and higher albumin contents than precocial birds.
What makes up the egg shell?
- cuticle layer
- spongy layer
- mammillary layer
- Shell membrane (inner and outer)
What is the egg cuticle?
The outermost layer of the shell
Which portion of the egg shell is the thickest?
the spongy (calcareous) layer
What are the functions of the egg shell?
- Strength
- Permitting gaseous exchange
- Preventing loss of egg contents and entrance of bacteria
- Serve as a nutrient source
Describe the strength of eggs shells.
The thickness of an egg shell correlates directly by the weight of the bird (i.e. bigger birds have thicker shells).
Calcium carbonate play a role in maintaining the structure, while the shell also has a cross-linked geometric design to further the shell’s integrity.
The egg shell must be thick enough to be sat on without breaking, and thin enough to be pecked through.
How do eggs perform gas exchange?
Via pores on the eggshell (around 10,000 pores per egg)
How is the eggshell a nutrient source for the developing embryo?
the shell serves as a small source of minerals
What is the shell membrane?
The shell membrane is made up of tough mats of protein fibers that help give the egg its structure.
There is an outer shell membrane that is closer to the shell, and an inner layer inside of the outer shell membrane.
What are air cells in eggs? How do they form? Where are they located? What purpose do they serve?
Air cells in eggs form when the membranes separate at the blunt end. The air cell forms as the egg cools, causing the liquids of the egg to retract and leave behind the air cell between the outer and inner shell membranes.
Location: blunt end of eggs between the outer and inner shell membrane
Purpose/function: supplies air to embryo when respiration is initiated
What are the functions of albumen?
- insulation
- shock absorption
- nutrient source
What percent of albumen is the outer thin layer?
23%
What percent of albumin is firm or dense?
57%
What percent of albumin is the inner thin layer?
17%
What percent of albumen is the chalaziferous layer (thick white; closest to the yolk)?
3%
What are chalazae?
The two twisted membranous strips that extend into the firm albumin to stabilize the yolk’s position in the egg by joining it to the ends of the shell.
What is the function of egg yolk?
to provide nutrients for the embryo
What is a blastodisk?
the unfertilized region of the egg yolk where embryos begin to develop; appears white, circular, and opaque
What is the blastoderm?
the fertilized region where the embryo develops; is oval shaped with a transparent center and opaque margins
Describe the components of the egg yolk.
The latebra is the tube-like structure where the embryo develops. It is surrounded by a layer of nutrients that deposit on the outside of this region. The vitelline membrane holds the yolk intact.
What is the latebra?
The tube-like structure where the embryo develops