Ch. 3: Embryogenesis and Development

Question 1

What occurs during fertilization?

Answer 1

occurs in the widest part of the fallopian tube – ampulla
sperm binds to secondary oocyte and release acrosomal enzymes that allow the head of the sperm to penetrate the corona radiata and zona pellucida
there is a release of calcium ions which prevents additional sperm from fertilizing the egg and increases the metabolic rate of the zygote – cortical reaction

Question 2

What is the difference between fraternal/dizygotic twins and identical/monozygotic twins?

Answer 2

fraternal twins are a result of ferilization of two different eggs by two difference sperm
identical twins result from splitting a zygote in two

Question 3

What is cleavage?

Answer 3

early division of cells in the embryo
after the first cleavage, the zygote becomes an embryo as it is no longer unicellular
indeterminate cleavage - cells that may become any organism
determinate cleavage - cells that are committed to a specific differentiation

Question 4

What is the morula?

Answer 4

solid mass of cells seen in early development

Question 5

What is a bastula?

Answer 5

morula undergoes blastulation
hollow ball of cells with a fluid filled inner cavity
trophoblast cells give rise to the placenta (on the outside)
inner mass cells give rise to the organism itself

Question 6

What occurs during implantation?

Answer 6

the blastula burrows into the endometrium in the uterus
trophoblastic cells give rise to the chorion, an extraembryonic membrane which turns into the placenta and there are chorionic vila that are small projections taht penetrate the endometrium

Question 7

What does the umbilical cord consist of?

Answer 7

two arteries and one vein encased in gelatinous substance

Question 8

What is the yolk sac?

Answer 8

supports embryo before the placenta is functional and is the site of early blood cell development

Question 9

What is the allantois?

Answer 9

membrane that is involved in early fluid exchange between the embryo and the yolk sac

Question 10

What is the amnion?

Answer 10

surrounds the allantois
thin, tough membrane filled with amniotic fluid and acts as a shock absorber for the embryo

Question 11

What is gastrulation?

Answer 11

generation of three distint cell layers
the archenteron is formed with a blastopore and three primary germ layers are formed

Question 12

Germ layer

What is the ectoderm?

Answer 12

“attracto” (things that attract us to others)
outermost layer that gives rise to epidermis, hair, nails and epithelia of many things, lens of eye, nervous system

Question 13

Germ layer

What is the mesoderm?

Answer 13

“means” (the means of getting around)
muscles, bones, circulatory system, gonads, connective tissue layers of digestive and respiratory systems

Question 14

Germ layer

What is the endoderm?

Answer 14

linings of “endermal” (inner) organs
forms linings of digestive and repiratory tracts as well as many organs attached to these systems

Question 15

Where is the adrenal cortex derived from?

Answer 15

mesoderm

Question 16

Where is the adrenal medulla derived from?

Answer 16

ectoderm (contians some nervous tissue

Question 17

Explain nerulation.

Answer 17

development of the nervous system after the germ layers are formed
1. rod of mesodermal cells - notochord - forms
2. induces group of overlying ectodermal vells to slide in to form neural folds that surround a neural groove
3. neural folds grow toward each other until fusing into neural tube
4. neural tube gives rise to CNS with the tip of each neural fold (neural crest cells) becomeing the peripheral nervous system

Question 18

What are teratogens?

Answer 18

substances that interfere with embryo development
Ex. alcohol, drugs, viruses, bacteria, environmental chemicals

Question 19

What is specification?

Answer 19

first stage of cell specilization
cell is reversibly designated as a specific cell type

Question 20

What is determination?

Answer 20

cell commits to a particular function
may be cause by asymmetric distribution of mRNA and proteins during cleavage or due to secretion of specific molecules from nearby cells (morphogens - molecules that cause cells to follow a particular developmental pathway)

Question 21

What is differentiation?

Answer 21

stem cells change their structure, function, and biochemistry ot match a cell type

Question 22

What are totipotent cells?

Answer 22

greatest potency
differentiate into any cell type

Question 23

What are pluripotent cells?

Answer 23

cells can differentiate into any cell type except for hose found in placental structures

Question 24

What are multipotent cells?

Answer 24

cells that can differntiate into multiple types of cells within a particular group

Question 25

Explain the types of cell-cell communication.

Answer 25

1. autocrine signals - act on the same cell that secreted the signal
2. paracrine signals - act on cells in local area
3. juxtacrine signals - cell directly stimulating receptors of an adjacent cell
4. endocrine signals - secred hormones that travel through the bloodsream to a distant target

Responder - cell that is induced (responsive cell)
Competent - responder must be able to respond to inducing signal

Question 26

What is reciprocal induction?

Answer 26

two tissues both induce further differentiation in each other

Question 27

Explain the umbilical arterties and the umbilical vein.

Answer 27

the umbilical arteries carry deoxygenated blood with waste products away from the fetus to the placenta
the umbilical vein carries oxygenated blood with utrients toward the fetus from the placenta

Question 28

How does fetal hemoglobin (HbF) differ from adult hemoglobin (HbA)?

Answer 28

HbF has a higher affinity for oxygen that helps transfer and retain oxygen in the fetal circulatory system

Question 29

Explain some functions of the placenta.

Answer 29

• forms a barrier for immune protection against pathogens
• secretes estrogen, progesterone, and human chorionic gonadotropin (hCG)

Question 30

Explain the three shunts in the fetal circulatory system.

Answer 30

1. foramen ovale - connects the right atrium to the left atrium (no lungs)
2. ductus arteriosus - connects pulmonary artery to the aorta (no lungs)
3. ductus venosus - connects umbilical vein to the inferioir vena cava (no liver)

Question 31

What happens in the first trimester?

Answer 31

organogenesis occurs
hear, eyes, gonads, limbs, liver, brain

Question 32

What happens in the second trimester?

Answer 32

growth occurs, movement begins, face becomes human, digits elongate

Question 33

What happens in the third trimester?

Answer 33

rapid growth and brain development, transfer of antibodies to fetus

Question 34

What happens during birth?

Answer 34

• cervix thins
• amniotic sac ruptures
• uterine contractions due to prostaglandins and oxytocin
• birht of fetus
• placenta and umbilical cord are expelled