Ch 29: Development

Question 1

What are the steps of fertilization?

Answer 1

• Sperm meets egg and secretes acrosome
• Digestive enzymes of acrosome degrades protective zona pellucida layer
• Sperm penetrates and delivers nuclueus
• Zona pellucida instantly hardens becoming impermeable to any other sperm
• Meoisis 2 is completed

Question 2

Cleavage begins immediately at _____ and consists of what 3 stages?

Answer 2

• Fertilization
• 2-cell, 4-cell, and 8-cell stages.

Question 3

Cleavage is the…

Answer 3

rapid mitosis/division of the zygote upon fertilization

Question 4

Cells during the cleavage stage are _____.

Answer 4

pleuripotent.

Question 5

If a cell is pleuripotent, it means…

Answer 5

that it has the potential to develop to be any cell in the body.

Question 6

Cell pleuripotentcy is lost at what stage of cleavage?

Answer 6

8-cell

Question 7

What occurs during the 2-cell stage of cleavage?

Answer 7

• Proteins shift to one side
• Cell splits in two
• Protein per side may differ

Question 8

What do the proteins in zygote regulate?

Answer 8

• Gene expression
• The ability of cells to make certian proteins

Question 9

What are the characteristics of differentiation and determination?

Answer 9

• Fate of what cells will become is determined
• Some genes are turned off
• This gives cells identity and function

Question 10

True or False

As rapid mitosis occurs, the zygote continues to grow.

Answer 10

False

It stays the same size

Question 11

What are the three stages of prenatal development?

Answer 11

1. Preembryonic stage
2. Embryonic stage
3. Fetal stage

Question 12

The preembryonic stage is subdivided into what four parts?

Answer 12

1. Zygote
2. Cleavage
3. Morula
4. Blastocysts

Question 13

Define:

Zygote

Answer 13

A single diploid cell formed by the union of egg and sperm

Question 14

Define:

Cleavage

Answer 14

• Mitotic division of the zygote into smaller, identical blastomeres

Question 15

Define:

Morula

Answer 15

A speroidal stage consisting of 16 or more blastomeres

Question 16

Define:

Blastocyst

Answer 16

• Fluid filled, spheroidal stage with an outer mass of trophoblast cells and inner mass of embryoblast cells
• Becomes implanted nt he endometrium
• Inner cell mass forms embryonic disc and
• differentiates into three primary germ layers

Question 17

Define:

Embryonic stage

Answer 17

• A stage in which the primary germ layers differentiate into organs and organ systems
• Ends when all organ systems are present

Question 18

Define:

Fetal stage

Answer 18

A stage in which organs grow and mature at a cellular level to the point of being capable of supporting life independently of the mother.

Question 19

The morula cells secrete fluid to form a _____, which form __ to __ days after fertilization.

Answer 19

blastocysts, 4-16

Question 20

In a blastocyst, the inner layer is called the _____ and will become the ____. The outer cell layer consists of _____, which will become the _____.

Answer 20

inner cell mass, embryo, trophoblasts, embryonic membrane

Question 21

What are the four extra embryonic membranes? Give description of each.

Answer 21

1. Chorion; outermost layer which fuses with endometrium upon implantation and will become placenta
2. Amnion; fluid filled sac around embryo
3. Yolk sac; non-functional
4. Allantois; non-functional

Question 22

In its early development, the zygote gets its nutrients directly from the _____.

Answer 22

endometrium

Question 23

At what part of the preembryonic stage does implantation occur?

Answer 23

blastocyst

Question 24

Around day 15, the embryonic disc forms a thickened cell layer called the _____ along the midline.

Answer 24

primitive streak

Question 25

Cells migrate toward and into the primative streak to form...

Answer 25

three germ layers.

Question 26

Name the 3 primary germ layers that form from the primative streak.

Answer 26

1. Ectoderm 2. Mesoderm 3. Endoderm

Question 27

The ectoderm germ layer is the _____ layer and will become \_\_\_\_\_.

Answer 27

outer, skin and nervous system

Question 28

The mesoderm germ layer is the _____ layer and will become \_\_\_\_\_.

Answer 28

middle, connective tissues and muscles

Question 29

The endoderm germ layer is the _____ layer and will become \_\_\_\_\_.

Answer 29

inner, digestive system

Question 30

The end of gastrulation is at __ days, and the zygote becomes \_\_\_\_.

Answer 30

16, an embryo

Question 31

Gastrulation is the start of the formation of the...

Answer 31

gastric/digestive system.

Question 32

Neurulation is....

Answer 32

the development of the nervous sytem

Question 33

Organogensis is...

Answer 33

the formation of the organs

Question 34

What are the characteristics of neurolation?

Answer 34

* Begins in ectoderm * Primitive strek folds into a neural tube that runs the length of the embryo * Top becomes brain, rest is spinal cord * Ends around 3 weeks

Question 35

In organogensis, what occurs during the first four weeks?

Answer 35

* Heart is formed and detectable by 3 weeks * Formation of limb buds * Eye development has started

Question 36

In organogensis, what occurs in weeks 5-7?

Answer 36

* Full head development * Full eye development * Ears * Digits

Question 37

What has occured by the end of week 8?

Answer 37

Full species specific traits have been acquired.

Question 38

What are the developmental traits of the second trimester?

Answer 38

* Facial movements * Sucking reflex * Hair * Eyelids and lashes by the end at six months

Question 39

What are the characteristics of the third trimester?

Answer 39

* At 7 months * Eyes open * Little body fat * Underdeveloped lungs * Premature birth range * 8-9 months is when most growth occurs and systems mature for birth

Question 40

What are the characteristics of the premature birth range?

Answer 40

* Begins at 7 months * Baby will require medical attention * Have underdeveloped lungs * Will require respiraters and heaters

Question 41

Birth is also known as \_\_\_\_\_/

Answer 41

Parturition

Question 42

What are the steps of fetal delivery?

Answer 42

* Increasing levels of estrogen and progesterone from placenta, uterine stretching and pressure on cervix eventually lead to the secretion of oxytocin * Oxytocin initiates contractions * Continual pressure causes oxytocin secretion to continue creating positive feedback loop * Contractions continue in strength pushing fetus into birth canal and out of the body. * Placent is then delivered.

Question 43

Mammary glands produce _____ for the first __ to __ days after birth.

Answer 43

colostrum, 1-3.

Question 44

Colostrum contains the antibody \_\_\_\_\_. Why is this important?

Answer 44

* IgA * Provides systemic immunity for the first few days until mothers milk takes over

Question 45

What does prolactin do?

Answer 45

stimulates mammary gland to produce milk

Question 46

Secretion of prolactin starts in week \_\_, and continues to...

Answer 46

5, increase during pregnancy

Question 47

By the end of pregnancy, prolactin levels are __ times than they were at start.

Answer 47

20 times

Question 48

What role does ocytocin play in nursing?

Answer 48

* Causes milk ejection * Initiated by sucking * If no production, milk production will stop * If producing, volume will grow with baby to meet its needs