Conceptus/Embryo - Weeks 0-3

Question 1

define the anatomical terms cephalic/cranial

Answer 1

relating to the head/skull

Question 2

define the anatomical terms rostral/caudal

Answer 2

relating to the lower part of the body

Question 3

define the anatomical terms anterior/ventral

Answer 3

relating to the front of the body

Question 4

define the anatomical terms posterior/dorsal

Answer 4

relating to the back of the body

Question 5

describe gametogenesis

Answer 5

consisting of mitosis and meiosis
this leads to genetic variation and diversity via exchange of genetic information at the chiasmata and random assortment of chromatids

Question 6

describe fertilisation

Answer 6

fusion of sperm and oocyte to form zygote (diploid, single celled embryo)

Question 7

describe cleavage

Answer 7

rapid mitotic cell division with no increase in size due to the zona pellucida surrounding the cells
occurs in days 1-4, forming morula and then blastocyst

Question 8

define the trimesters of pregnancy

Answer 8

first trimester - week 1 to 12
second trimester - week 13 to 26
third trimester - week 27 to end of pregnancy

Question 9

define the term teratogen

Answer 9

substance or process that induces the formation of developmental abnormalities in a fetus

Question 10

define the term mutagen

Answer 10

an external agent that when applied to cells can increase the rate of mutation

Question 11

explain trisomy 21

Answer 11

down syndrome

an additional cope of chromosome 21, typically caused by nondisjunction during oocyte formation

Question 12

describe morula

Answer 12

formed during cleavage, 16+ cells

Question 13

describe blastocyst

Answer 13

final product of cleavage

Question 14

briefly describe the foetus period

Answer 14

growth and weight gain
fetus’ main growth in length is during the 2nd trimester, and most weight is gained during the 3rd trimester
tissues also become mature and functional, overt sexual differentiation and bone is laid down; connections made in CNS

Question 15

describe the primary processes that occur during embryonic development

Answer 15

Cell division - increase in number of cells
differentiation - specialisation, change in appearance/structure, adoption of new functions
cell attachment - physical/functional linkages, formation of tissues, mesenchyme and epithelial tissue
apoptosis - programmed cell death
induction - ability of one cell type to cause another to differentiate (directly or at a distance)
cell migration - movement from one location to another

Question 16

describe how development of the embryo is regulated

Answer 16

genetic - gene expression is tightly regulated in time and space
epigenetic - preferential expression of either maternal or the paternal copy of a gene
environmental

Question 17

briefly describe the foetus period

Answer 17

growth and weight gain
fetus’ main growth in length is during the 2nd trimester, and most weight is gained during the 3rd trimester
tissues also become mature and functional, overt sexual differentiation and bone is laid down; connections made in CNS

Question 18

describe the secondary processes that occur during embryo development

Answer 18

the reason our organs are the way they are
axis formation/polarity - ‘rolling up’/changing of shape, cells need to know where they are in relation to each other and the embryo as a whole
folding/rotation - entire embryo or structures within it, gives embryo its 3D form, allows the formation of complex organ structures (heart, gut)
developing heart - begins as a simple tube