8/19 Gastrulation And Body Folding

Question 1

Describe how the he cell movements of gastrulation generate the three germ layers

Answer 1

Following the implantation of the blasicist into The endometrium of the uterus gastrulation begins, three distinct germ layers form. The ectoderm, the endoderm, and the mesoderm. These form by having the epiblast seperates from the tropoblast (forming the amniotic space) and then starts to invaginate inward to form the primitive streak and Hensen’s node (at the top of the primitive streak [this is the organizer]). Some cells migrate all the way to the hypoblast, displace it and form the endoderm. Some cells migrate to the middle and form the mesoderm, and the cells on the epiblast are now the ectoderm.

Question 2

Describe the cell movements of gastrulation

Answer 2

The epiblast vaginate inwards, creating the mesoderm and displacing the hypoblast to create the mesoderm

Question 3

Name the primary subdivisions of the axial mesoderm

Answer 3

The Prechordal plate, the Paraxial mesoderm of the head, lateral mesoderm, Paraxial mesoderm of the trunk, intermediate mesoderm of the trunk, lateral plate mesoderm of trunk, tail bud mesoderm.

Question 4

WHAT STRUCTURES DO THE PRIMARY SUBDIVISIONS OF THE ASIAL MESODERM CONTRIBUTE TO?

Answer 4

The Prechordal plate (minor contribute to head and brain patterning), the Paraxial mesoderm of the head (head muscle and some bone), lateral mesoderm (originate in head and forms the cardiac mesoderm), Paraxial mesoderm of the trunk (forms somites), intermediate mesoderm of the trunk (urogenital), lateral plate mesoderm of trunk (forms somatic and splanchnic mesoderm), tail bud mesoderm (contributes to posterior structures of the spinal cord and tail).

Question 5

Name malformations associated with defective gastrulation

Answer 5

Human dicephalus; craniopagus parasiticus (duplicate heads); holoprosencephaly (midline disorders); sirenimelia (fused lower limbs); atavistic tails

Question 6

Discuss how malformations associated with defective gastrulation arise.

Answer 6

Human dicephalus (over expression of goosecoid transcription factor normally found in prechordial plate); craniopagus parasiticus (duplicate heads)(movement of the organizer tissue); holoprosencephaly (midline disorders) (reduced function of the notochord often caused by disruption in sonic hedgehog signally); sirenimelia (fused lower limbs)(defective production of trunk mesoderm, Bmp7 and Tsg gene mutations affect Bmp signaling); atavistic tails (tail mesoderm defect)

Question 7

describe the partitioning of the coelom to form the plural, pericardial and peritoneal cavities of the body

Answer 7

the coeloem is seperated by the septum transversum just below the heart (a small shelf); The pleuroperitoneal fold will then grow into meet the septum transversum, this forms two seperate chambers for each of the lungs and seperates out the body cavities.

Question 8

name the major directional terms for the body.

Answer 8

Cranial/superior; Ventral/Anterior; Dorsal/Posterior; Caudal/Inferior; Lateral; Medial.

Question 9

Descirbe a defect of improper body folding

Answer 9

Gastroschisis: a condition where the body folds without the gut inside!

Question 10

Describe the prosess of Neurulation

Answer 10

The ectoderm over the dorsal midline becomes he neural plate (presumptive neural tissue). The tissue then folds inward forming a tube within the epidermis. this is the neural tube. associated neural crest cells are also released

Question 11

What are the mesodermal subdivisions of the trunk

Answer 11

lateral plate mesoderm (towards the outside edge of the mesoderm); Intermediate mesoderm (inbetween the outside edge and the midline); the somites near the midline; and the notochord just below the Neural tube at the midline!

Question 12

Name the three germ layers from dorsal to ventral

Answer 12

Ectoderm, mesoderm, endoderm.

Question 13

What structures does the Prechordal plate contribute to

Answer 13

minor contribute to head and brain patterning

Question 14

What Structures does the Paraxial mesoderm contribute to

Answer 14

head muscle and some bone

Question 15

What structures does the lateral mesoderm contribute to

Answer 15

originate in head and forms the cardiac mesoderm

Question 16

what structures does the paraxial mesoderm of the trunk contribute to

Answer 16

forms somites

Question 17

what structure would most likely be affected if there was a defect in the intermediate mesoderm of the trunk

Answer 17

urogenital

Question 18

what would a possible result of moving the organizer tissue be

Answer 18

craniopagus parasiticus (duplicate heads)

Question 19

What stuctures might be affected by a disruption in the lateral plate mesoderm of the trunk

Answer 19

forms somatic and splanchnic mesoderm

Question 20

What does the tail bud mesoderm contribute to?

Answer 20

contributes to posterior structures of the spinal cord and tail

Question 21

What would inappropriate partitioning of the coelom fail to form?

Answer 21

plural, pericardial and peritoneal cavities of the body

Question 22

Oh, no! you have over expressed goosecoid transcription factor in the prechordial plate, what unusual consequence might this have?

Answer 22

Human dicephalus (over expression of goosecoid transcription factor normally found in prechordial plate);

Question 23

A scientist has cleverly moved the organizing tissue to a different locatoin in the endoderm…what sydrome might this mimick in the resulting fetus?

Answer 23

Craniopagus parasiticus

Question 24

what molecular signal may play an important part in the development of the cyclops that tormented odysseus

Answer 24

sonic hedgehod signalling

Question 25

This affliction seems to be duplicated in mice that have two genes affecting Bmp signalling mutated, what is the disorder and what are the genes?

Answer 25

Sirenimelia; Bmp7 and Tsg genes