ABAS 3450 - Embryology
ABAS 3450 - Embryology ABAS 3450
Popular in Anatomy and Physiology of Domestic Animals
Popular in Agricultural & Resource Econ
This 7 page Class Notes was uploaded by Allison Collins on Saturday March 26, 2016. The Class Notes belongs to ABAS 3450 at Middle Tennessee State University taught by Dr. Kevin Downs in Winter 2016. Since its upload, it has received 31 views. For similar materials see Anatomy and Physiology of Domestic Animals in Agricultural & Resource Econ at Middle Tennessee State University.
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Date Created: 03/26/16
3/24 – Embryology Purpose of the egg: to protect and nourish the embryo Embryos incubate for 21 days (remember: incubation, not gestation) Protection – the shell • Made of calcium; formed in the uterus • Arch shape – difficult to break from outside, easy from inside • First line of defense against microbes – however, they can still enter through the pores • Inner and outer shell membrane o Fused together; formed in isthmus o Made of protein o Second line of defense against microbes • Air cell – only place inner and outer membrane aren’t fused o At wide end of the egg o Gets larger as incubation progresses o Embryo breaks into it and starts to breath air, then continues to break through cell when hatching • Cuticle – light outer protein layer that dries quickly after the cell is laid Nourishment – the yolk • Was originally a follicle in the ovary • Majority of composition: nutrients for the embryo • Albumen – egg white – composed of protein and water o Thick albumen: from magnum o Thin albumen: from uterus • Chalazae – on either pole of yolk – spun-‐out protein fibers from thick albumen, formed when yolk twists • Vitelline membrane – thin membrane that surrounds the yolk, is inside the yolk sac • Germinal disc – where embryo develops if fertilized 2 o Blastoderm – fertile disc – looks like a donut with a dark middle o Blastodisc – infertile disc – indescript white spot • Dark/light yolk layers – daytime/nighttime – hen eats during the day and the nutrients give pigmentation to the yolk • Latebra – tunnel created from germinal disc to center of yolk – unsure of function 3 extra-‐embryonic membranes • Amnion – very thin fluid-‐containing membrane surrounding embryo o Protects embryo by absorbing shock o Not as important for human embryos – only needed before implantation of egg cell o Gets tighter around embryo as incubation progresses 3 • Yolk sac – enables embryo to absorb nutrients from the yolk o Meckel’s diverticulum – remnant of yolk sac attachment o Retains shape and size as incubation progresses • Chorio-‐allantois – lines the shell o Enables embryo to breathe – oxygen/carbon dioxide exchange § Gases travel through pore à chorio-‐allantois à blood à embryo o Store waste and absorb calcium o Spreads over entire inside of shell as incubation progresses 4 Hatch position: assumed at 18 days • Correct: head toward air sac (wide end of egg), head under right wing 5 Shell/yolk layers from outside to inside: Cuticle à shell à outer shell membrane à inner shell membrane à chorio-‐allantois à albumen à yolk sac à yolk à amnion à amnionic fluid à embryo ß 5 days 6 7