Biology: Chapter 4: Embryogenesis

Question 1

what is fertilization

Answer 1

joining of a sperm and an ovum

Question 2

where does fertilization occur

Answer 2

ampulla of the fallopian tube

Question 3

What happens when a sperm penetrates the ovum

Answer 3

an acrosomal apparatus appears and the sperm injects its pronucleus; calcium is released to prevent other sperm from fertilizing the egg (cortical reaction)

Question 4

how do fraternal twins happen

Answer 4

result from the fertilization of two eggs by two different sperm

Question 5

how do identical twins happen

Answer 5

splitting of the zygote into two

Question 6

What happens after the first cleavage of the zygote

Answer 6

it becomes an embryo as it is no longer unicellular

Question 7

What is an indeterminate cleavage

Answer 7

results in cells that are capable of becoming any cell in the organism

Question 8

what is determinate cleavage

Answer 8

results in cells that are committed to differentiating into a specific type of cell

Question 9

what is the morula

Answer 9

solid mass of cells seen in early development

Question 10

what is the blastula (blastocyst)

Answer 10

has fluid filled center called a blastocoel with two different structures: trophoblast and inner cell mass

Question 11

what are trophoblasts

Answer 11

cells in the blastula that become placental structures

Question 12

what is the inner cell mass

Answer 12

cells in the blastula that becomes the organism

Question 13

where does the blastula implant

Answer 13

the endometrial lining

Question 14

what is the chorion

Answer 14

contains chorionic villi which penetrate the endometrium and create interface between maternal and fetal blood

Question 15

what supports the embryo before the placenta forms

Answer 15

yolk sac

Question 16

what is the allantois

Answer 16

involved in early fluid exchange between the embryo and the yolk sac

Question 17

what is the amnion

Answer 17

lies inside the chorion and produces amniotic fluid

Question 18

what happens during gastrulation

Answer 18

the archenteron is formed with a blastopore at the end; As the archenteron grows through the blastocoel it contacts the opposite side establishing three germ layers

Question 19

what is the ectoderm

Answer 19

becomes the epidermis, hair, nails, the epithelial of the nose and mouth, anal canal, lens of the eye and the nervous system (adrenal medulla)

Question 20

what is the mesoderm

Answer 20

becomes muscloskeletal, circulatory, excretory systems; gives rise to the gonads, muscular and connective tissue layers of digestive and respiratory systems and the adrenal cortex

Question 21

what is the endoderm

Answer 21

becomes epithelial linings of the respiratory and digestive tracts; parts of the pancreas, thyroid, bladder, and distal urinary tracts

Question 22

what happens during neurlation

Answer 22

the notocord induces a group of overlying ectodermal cells to form neural folds surrounding a neural groove; the folds fuse to form the neural tube; the tip of each neural fold contains neural crest cells

Question 23

what does the neural tube become

Answer 23

CNS

Question 24

what does the neural crest become

Answer 24

PNS

Question 25

what are teratogens

Answer 25

substances that interfere with development causing defects or death

Question 26

what is determination

Answer 26

commitment of the cell to a specific lineage

Question 27

what are morphogens

Answer 27

promote development of specific cell line; cell must have competency to respond to morphogens

Question 28

what is differentiation

Answer 28

refers to the changes of a cell due to selective transcription to take on appropriate characteristics of cell type

Question 29

what are totipotent stem cells

Answer 29

able to differentiate into all cell types; including placental structures and germ layers

Question 30

what are pluripotent stem cells

Answer 30

able to differentiate into all three of germ layers and their derivatives

Question 31

what are multipotent stem cells

Answer 31

able to differentiate only into a specific subset of cell types

Question 32

what is autocrine signaling

Answer 32

signals act on the same cell that released the signal

Question 33

what is paracrine signaling

Answer 33

signals acts on local cells

Question 34

what is juxtacrine signaling

Answer 34

signals act through direct stimulation of adjacent cells

Question 35

what is endocrine signaling

Answer 35

signals act on distant tissues after traveling through circulatory system

Question 36

what are growth factors

Answer 36

peptides that promote differentiation and mitosis in certain tissue

Question 37

what is reciprocal induction

Answer 37

two tissues both induce further differentiation in each other

Question 38

what is apoptosis

Answer 38

programmed cell death

Question 39

what is necrosis

Answer 39

cell death as result of an injury

Question 40

why is the placenta important

Answer 40

nutrient, gas, and waste exchange through concentration gradients

Question 41

what is fetal hemoglobin

Answer 41

has a higher affinity for oxygen to assist the transfer and retention of oxygen into the fetal circulatory system

Question 42

what is the placental barrier

Answer 42

serves as immune protection against pathogens and assists in antibody transfer

Question 43

what hormones does the placenta excrete

Answer 43

estrogen, progesterone, and human chorionic gonadotropin

Question 44

what are umbilical artieries

Answer 44

carries deoxygenated blood to the placenta from the fetus

Question 45

what are umbilical veins

Answer 45

carries oxygenated blood from the placenta to the fetus

Question 46

what is the importance of the foreman ovale

Answer 46

bypasses the lungs by connecting the right atrium to the left atrium

Question 47

what is the importance of the ductus arteriosus

Answer 47

bypasses the lungs by connecting the pulmonary artery to the aorta

Question 48

what is the importance of the ductus venous

Answer 48

bypasses the liver by connecting the umbilical vein to the inferior vena cava

Question 49

what is happens during the first trimester

Answer 49

organogenesis occurs (heart, eyes, gonads, limbs, liver, some of the brain)

Question 50

what happens during the second trimester

Answer 50

tremendous growth, movement begins, the face becomes human, and digits elongate

Question 51

what happens during the third trimester

Answer 51

rapid growth and brain development; transfer of antibodies to the fetus

Question 52

what happens during birth

Answer 52

1) cervix thins and amniotic sac ruptures 2) uterine contractions coordinated by prostaglandins and oxytocin 3) placenta and umbilical cord are expelled