Embryonic Development

Question 1

Blastocyst

Answer 1

An embryo which has been left to develop until day 5 or 6 and presents a complex cellular structure formed by approximately 200 cells. Development stage prior to implantation of the embryo in the mother’s uterus.

Question 2

Trophoblast

Answer 2

Cells forming the outer layer of a blastocyst, which provide nutrients to the embryo and develop into a large part of the placenta.

Question 3

Zona pellucida

Answer 3

In human development, during the first week of development following fertilization the zona pellucida remains surrounding the blastocyst from which it “hatches” to commence implantation.

Question 4

Internal cell mass (description)

Answer 4

Forms within the blastocyst prior to its implantation within the uterus as a cellular mass on one side of the hollow interior of the round embryo. After the blastocyst stage of embryonic development, the inner cell mass of the blastocyst goes through gastrulation and becomes organized into the three germ layers

Question 5

Internal cell mass (other names)

Answer 5

embryoblast

Question 6

Gut tube

Answer 6

primitive precursor of both the respiratory and digestive systems

Question 7

Neural plate

Answer 7

A strip of ectoderm, above the notochord, that lies along the central axis and develops into the central nervous system. The neural plate folds and forms the neural tube.

Question 8

Mesoderm (what it gives rise to)

Answer 8

the dermis of the skin, the heart, the muscle system, the urogenital system, the bones, and the bone marrow (and therefore the blood).

Question 9

Ectoderm (what it gives rise to)

Answer 9

Epidermis and nervous system

Question 10

Endoderm (what it gives rise to)

Answer 10

Lining of the GI tract and respiratory tract

Question 11

Yolk sac (what it gives rise to)

Answer 11

Gut tube and umbilical cord

Question 12

Yolk sac (description)

Answer 12

Membranous sac attached to an embryo, formed by cells of the hypoblast adjacent to the embryonic disk; where primordial germ cells are obtained from

Question 13

Septum transversum

Answer 13

a thick mass of cranial mesenchyme, formed in the embryo, that gives rise to parts of the thoracic diaphragm and the ventral mesentery of the foregut

Question 14

Septum transversum (how it moves)

Answer 14

Begins in front of the mouth and brain; is carried by the head folds down into the chest cavity

Question 15

Time to gastrulation from fertilization

Answer 15

14 days

Question 16

Somite

Answer 16

One of a longitudinal series of block-like segments of mesoderm that will eventually differentiate into dermis, skeletal muscle, cartilage, tendons, and vertebrae

Question 17

Notocord

Answer 17

flexible rodlike structure of mesodermal cells that is the principal longitudinal structural element that will become the spinal column

Question 18

Gastrulation (description)

Answer 18

The process by which the germ layers are formed