embryology

Question 1

describe the steps of ovulation

Answer 1

1. Increased production of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) from anterior pituitary gland, a follicle begins to mature
2. Graafian follicle matures (with the oocyte completing Meiosis I and initiating Meiosis II)
3. LH causes contraction and then rupture of ovarian wall, releasing the oocyte
4. Fimbriae sweep oocyte into fallopian tube
5. Contraction of fallopian tube, along with mucosal cilia, move oocyte towards uterus (takes 3 to 4 days)
6. At site of rupture, the corpus luteum is formed. These cells secrete progesterone, which prepares
   Gratian
   follick
   the uterus for pregnancy
   most mahre

Question 2

describe the steps of fertilisation

Answer 2

Fertilisation occurs in ampulla of fallopian tube

Phase 1: Penetration of the corona radiata

Phase 2: Penetration of the zona pellucida

Phase 3: Fusion of sperm and oocyte membranes

Formation of the zygote, aka the fertilised ovum

Question 3

cleavage

describe the steps of mitosis and implantation

Answer 3

Now we have reached ‘Day 1’ and the future embryo begins a process called cleavage

Cleavage describes the division of cells after fertilisation:
Day 1: Single cell zygote
Day 2: Two-cell stage (zygote)
Day 3: Four-cell stage (zygote)
Day 3-4: Eight-cell stage (early morula)
By Day 4: 16-cell stage (late morula)

Each cell is known as a blastomere

By day 4, cells in the morula separate into two cell masses:
the inner cell mass (embryoblast)
the outer cell mass (trophoblast)

A fluid cavity, known as the blastocoele, is formed and the embryo is now a blastocyst

Question 4

what is the trophoblast

Answer 4

it is the future placenta

Question 5

embryoblast cells differentiate into…

Answer 5

epiblast, hypoblast and the anterior visceral endoderm

Question 6

in week 3 the formation of the trilaminar disc is formed by a process called…

Answer 6

gastrulation

Question 7

epiblast becomes the 1.

epiblast cells that invaginate through the primitive streak become the 2.

hypoblast cells become the 3.

Answer 7

1. ectoderm
2. mesoderm

3.endoderm

Question 8

ectoderm forms 1.

mesoderm forms 2.

endoderm forms 3.

Answer 8

1. forms skin and neural tissue.

2.forms connective tissue, muscle and blood vessels.

3. forms tubes of the body i.e guts and airways.

Question 9

What does the paraxial mesoderm form into…

Answer 9

Musculoskeletal system

Question 10

What does the intermediate mesoderm turn into…

Answer 10

Urogenital system

Question 11

The lateral plate mesoderm is form by 2 layers which are:

Answer 11

Parietal layer and visceral layer

Question 12

What is the condition called If neural tube fails to close in the cranial region

Answer 12

Anencephaly (lethal)

Question 13

What is the condition called if the neural tube fails to close from cervical region caudally

Answer 13

Spina bifida