Define Zygote

Fertilized egg

Describe how you were able to tell by observation when a sea urchin egg was fertilized

A fertilized membrane is present beneath the outer jelly coat.

fusion of male and female pronuclei

fertilization

a solid ball of embryonic cells

morula

process of rapid mitotic cell division w/o intervening growth periods

cleavage

Combination of egg and sperm

zygote

Process involving cell rearrangements to form the three primary germ layers

gastrulation

Embryonic stage in which the embryo consists of a hollow ball of cells

blastula

What is the importance of cleavage in embryonic development?

It provides a large number of smaller cells for morphogenesis

How is cleavage different from mitotic cell division, which occurs later in life?

During cleavage there are no intervening growth periods between the successive divisions. Therefore the cells get smaller & smaller, bu the embryonic mass remains essentially the same size.

Produces the embryonic body

inner cell mass

becomes the chorion and cooperates with uterine tissues to form the placenta

trophoblast

produces the amnion, yolk sac and allantois

inner cell mast

produces the primordial germ cells (an embryonic membrane)

yolk sac

An embryonic membrane that provides the structural basis for the body stalk or umbilical cord

allantois

A. Decidua basalis
B. Decidua capsularis
C. Uterine Cavity
D. Ectoderm
E. Mesoderm
F. Endoderm
G. Chorion
H. Chorionic villi
I. Body Stalk
J. Amnion

Explain the process and importance of gastrulation

It involves the migration, movement & rearrangement of embryonic cells, so that a 3-layer embryo is formed (3 primary germ layers)

What is the functionof the amnionand the amniotic fluid?

The amnion is a protective, fluid filled sac that surrounds the embryo. The fluid buffer protects theembryo from phsical trauma & prevents adhesion formation during rapid growth.

Describe the process of implantation, noting the role of the tropoblast cells

The tropoblast cells overlying the inner cell mass adhere to the endometrium. The trophoblast cells then secrete enzymes that erode the endometrial lining to reach the vascular supply beneath.

How many days after fertilization is implatation generally completed?

12-14

What event in the female menstrual cycle ordinarily occurs around mid cycle if implantation does not occur

Menses, because this is usually the 14th day after ovulation.

What name is given to the part of the uterine wall directly under the implanting embryo? What is surrounding the rest of the embryonic structure?

Decidua basalis; decidua capsularis

What does decidua mean?

"falls off" or is subject to periodic shedding

How is the term "deciduas" applied to pregnancy?

After birth they slough off and are flushed out of the uterus.

Which two organ systems are extensively developed in the very young embryo?

Nervous system and the circulatory system.

Describe the direction of development?

Fill in later

Does bodily control during infancy develop in the same direction? Think! Can an infant pick up a common pin (pincer grasp) or wave his arms earlier? is arm-hand or leg-foot control achieved earlier?

Fill in Later

Skeletal muscle develops from

mesoderm

The skeleton develops from

mesoderm

The gut lining develops from

endoderm

The respitory mucosa develops from

endoderm

The circulatory system develops from

mesoderm

The epidermis of the skin develops from

ectoderm

The nervous system develops from

ectoderm

The serosa membrane develops from

mesoderm

The liver, pancreas deveops from

endoderm

15. Fill in later

15. Fill in later

Where in the human uterus do implantation and placentation ordinarily occur?

High in the Uterus

Describe the functions of the placenta

Provides nutrients and oxygen to the fetus, removes fetal wastes and produces the hormones of pregnancy.

What embryonic membranes has the placenta more or less "put out of business"?

The placenta provides nutrients and oxygen to the fetus, removes fetal wastes, and produces the hormones of pregnancy. The yolk sac and allantois.

When does the embryo come to be called a fetus?

The 9th week of development

What is the usual and most desirable fetal position in utero? Why is this the most desirable position?

head down; because it makes it a whole lot easier on mom and fetus during birth.

Describe the gross structure of the human placenta

Smooth on the side from which the umbilecal cord issues; Torn, rough & bloody on the side that was united w/maternal tissues/blood rich.

What is the tissue origin of the placenta? Fetal, maternal or both?

Both

What are the placental barriers that must be crossed to exchange materials

The membranes of the villi & capillary walls of the fetal vascular supply.