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EMBRYOLOGY WK 1-4
HAE QUIZ 1
29
Anatomy
Graduate
08/25/2011

Additional Anatomy Flashcards

 


 

Cards

Term

week 1

stage and main events

Definition

pre-implantation (pre-embryonic) period

 

formation of morula; development of morula into a blastocyst; implantation

Term

week 2-8

stage and main events

Definition

embryonic period (period of greatest sensitivity to teratogens (environmental factors that cause birth defects))

 

formation of germ layers that give rise to major body systems (gastrulation); formation of central nervous system (neurulation); formation of the general body form (embryonic folding); formation of major body systems

Term

week 8 - 38

stage and main events

Definition

fetal period

 

structural and functional growth of major body systems 

Term
fertilization
Definition
beginning of human development when a sperm invades an ovum, which usually occurs in the uterine tube
Term
zygote
Definition
fertilized cell
Term
cleavage
Definition

rapid mitotic cell division without increasing in size; continues until there are 16 daughter cells (blastomeres) contained within the zona pellucida

Term
blastomeres
Definition
Any of the cells resulting from the cleavage of a fertilized ovum during early embryonic development
Term
zona pellucida
Definition
The strong membrane that forms around an ovum as it develops in the ovary. The membrane remains in place during the egg's travels through the Fallopian tube. To fertilize the egg, a sperm must penetrate the thinning zona pellucida. If fertilization takes place, the membrane disappears as it becomes a blastocyst to permit implantation in the uterus.
Term
morula
Definition

compact sphere of cells resulting from cleavage of zygote

 

~4days

Term
blastocyst
Definition
the morula becomes a blastocyst as it enters the uterine cavity because a fluid-filled space (blastocoele or blastocyst cavity) forms within the sphere of cells
Term
blastocoele
Definition

(aka blastocyst cavity)

fluid-filled center region of a blastocyst

Term
embryoblast
Definition
inner cell mass concentrated at the embryonic pole of the blastocyst and will form the embryo proper
 
Term
trophoblast
Definition
the outer cell mass, which surrounds the embryoblast and blastocyst cavity, will contribute to the placenta
Term
ectopic pregnancy
Definition
when implantation occurs outside the uterine cavity, usually due to the slow transit of the ovum along the uterine tube. 
Term
Implantation
Definition
Implantation continues for about a week as the blastocyst sinks into the endometrium. The trophoblast differentiates into two layers and the embryoblast differentiates into two layers that together form a flat bilaminar disc.
Term
syncytiotrophoblast
Definition
outer layer of trophoblast that invades the endometrium, and eventually forms lacunae that make contact with maternal blood vessels (sinusoids), establishing utero-placental circulation
Term
cytotrophoblast
Definition
inner single layer of trophoblast that provides new cells for the syncytiotrophoblast.
Term
hypoblast
Definition
layer of embryoblast that differentiates into cells adjacent to the blastocyst cavity.
Term
epiblast
Definition
layer of embryoblast that differentiates into cells adjacent to the cytotrophoblast.
Term
amniotic cavity
Definition
Develops within the epiblast. Epiblast cells adjacent to the cytotrophoblast at the embryonic pole specialize to secrete amniotic fluid, and are called amnioblasts.
Term
exocoelomic membrane
Definition
The hypoblast sends out a layer of cells that form the exocoelomic (Heuser’s) membrane along the inner surface of the blastocyst cavity. The cavity lined by the membrane is now called the exocoelomic cavity or primary yolk sac (the source of nutrition for the embryo before the placenta is functional).
Term
extraembryonic mesoderm
Definition
a layer of loose connective tissue produced by the exocoelomic membrane, which fills the space between the cytotrophoblast, and the primary yolk sac and amniotic cavity. 
Term
extraembryonic coelom
Definition

Lacunae form within the extraembryonic mesoderm, which coalesce to form the extraembryonic coelom. 

This space (now called the chorionic cavity) grows to completely surround the bilaminar germ disc (developing embryo), primitive yolk sac, and amniotic cavity. 

Term
secondary yolk sac
Definition
Growth of the chorionic cavity “pinches off” the primary yolk sac and a smaller secondary or definitive yolk sac is created. 
Term
connecting stalk
Definition

The connecting stalk is the extension of extraembryonic mesoderm that connects the embryo to the cytotrophoblast, and forms the umbilical cord.

 
Term
Gatrulation
Definition
Gastrulation is the process that results in the formation of three embryonic germ layers. 
Term

primitive streak

+ 3 main body axes of the embryo

Definition

 

Gastrulation begins with the formation of the primitive streak, a thickened line at the caudal (posterior) end of the epiblast that establishes three main body axes of the embryo – craniocaudal, dorsoventral, left-right

Term
primitive node
Definition
The primitive node is a raised area that surrounds the primitive pit at the cranial (anterior) end of the streak.
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