Concept Of Embryology

Question 1

What are the three reasons we study embryology

Answer 1

1) reduces body to its simplest form
2) medical reasons for looking at development
3) see what things are made of and how they develop etc.

Question 2

How do we study embryology

Answer 2

1) anatomical approach
2) experimental approach
3) developmental approach

Question 3

Anatomical approach

Answer 3

Careful observation

Question 4

Experimental approach

Answer 4

Intervention followed by observation

Question 5

Developmental approach

Answer 5

1) what parts of embryo make what organs

2) huge advances in microscopy

Question 6

Aristotle proposed what two ways

Answer 6

1) everything is preformed and gets bigger during development
2) new structures arise progressively

Question 7

What is the first law of Von Baer

Answer 7

General characteristics of the group which an embryo belong develops before special characteristics

Question 8

What is the second law of Von Baer

Answer 8

General structural relations are likewise formed before the most specific appear

Question 9

What is the third law of Von Baer

Answer 9

The form of any given embryo does not converge upon other definite forms but separates itself from them

Question 10

What is the fourth law of Von Baer

Answer 10

The embryo of a higher animal form never resembles the adult of another animal form, such as one less evolved, but only its embryo

Question 11

What is ontogeny

Answer 11

The entire sequence of events involved in the development of an individual organism

Question 12

What is phylogeny

Answer 12

The sequence of events involved in the evolutionary development of a species or taxonomic group of organisms

Question 13

What are the 8 stages involved with ontogeny and phylogeny

Answer 13

1) spermatozoon and oocyte
2) blastula
3) gastrula
4) formation of mesoderm
5) metamerism
6) yolk sac
7) amniotic sac
8) placenta

Question 14

The dorsal blastopore lip or “the organiser” induces what

Answer 14

An extra embryonic axis containing a new neural tube and eventually a second embryo forms that is linked to the host

Question 15

What are the three consecutive circles in the dorsal blastopore lip

Answer 15

Presumptive notochord, presumptive somites, presumptive endoderm

Question 16

What is gastrulation

Answer 16

Cell movements result in a massive reorganisation of the embryo from a simple spherical ball of cells, the blastula, into multi- layered organism

Question 17

What is the dorsal lip responsible for

Answer 17

Neural induction.

The tissue also has the ability to direct the development of host tissue to form a second neural tube.

Question 18

What is a blastopore

Answer 18

Opening of the archenteron to the exterior of the embryo at the gastrula stage.
Formed by the invagination of the blastula to form a gastrula

Question 19

What is the “neural tube”

Answer 19

A hollow structure from which the brain and spinal cord form

Question 20

Notochord

Answer 20

A cartilaginous skeletal rod supporting the body in all embryonic and some adult chordate animals

Question 21

Explain the experiment with frogs

Answer 21

• experimental approach
• initial group of cells called the organiser
• cut a bit out and stick it on the other side= secondary area of that differentiation of a 2nd body axis

Question 22

What is metamerism

Answer 22

An initial sub division of the embryonic body into an ordered series of equal segments (metameres)
It forms the basis of development of vertebrates

Question 23

What is the process of which somites are formed

Answer 23

Somitogenesis

Question 24

How are somites paired

Answer 24

They are paired bilaterally and form along the head-tail axis and subdivide

Question 25

What type of gene indicates where somites start

Answer 25

Hox genes

Question 26

What is induction (Hans spemann)

Answer 26

The process by which the identity of certain cells influences the developmental fate of surrounding cells

Question 27

What does the hox code help specify

Answer 27

The AP axis (anterior- posterior)

Question 28

What is the hox gene

Answer 28

A subset of homeotic genes which regulate the development of anatomical structures in various organisms

Question 29

How are hox genes identified

Answer 29

1) their protein product is a transcription factor
2) they contain a DNA sequence known as homeobox
3) in animals, the organisation of the hox genes in the chromosome is the same as the order of their expression along the ant-post axis of the developing animal and are thus said to display collinearity