Early Embryology 1

Question 1

Define pre-embryonic, embryonic and foetal periods of development

Answer 1

Pre-Embryonic: Week 1-2 > cell production
Embryonic: Week 3-8 > building complex systems
Foetal: Week 9-38 > growth

Question 2

What changes take place as the zygote moves down the Fallopian tube?

Answer 2

• Oocyte fertilised by sperm in Ampulla to form a zygote

- Cells in zygote continue to divide when travelling along the Fallopian tube

Question 3

Define: Zygote, Cleavage, Zona Pellucida and Morula

Answer 3

Zygote - An oocyte fertilised by a sperm, diploid cell
Cleavage - Furrow that forms during Mitosis division
Zona Pellucida - Glycoprotein shell that protects egg from further sperm invasion
Morula - Ball of totipotent cells

Question 4

Define Ovary, Fallopian Tube and Uterus

Answer 4

Ovary - Female reproductive organ in which ova are produced
Fallopian Tube - One of a pair of tubes along which ova travel from the ovaries to the uterus
Uterus - Site where a fertilised egg implants and develops into a foetus

Question 5

How does a blastocyst form?

Answer 5

A fluid filled cavity that opens up in the morula during cell division

Question 6

What are the initial stages of implantation?

Answer 6

• Morula differentiates into mass of pluripotent cells
• Blastocyst hatches from Zona Pellucida
• Can now interact and implant to the uterine surface
• Embryo and Placenta are formed

Question 7

Define blastocyst, trophoblast and inner cell mass

Answer 7

Blastocyst - Mass of differentiated cells 5-6 days post fertilisation that helps implantation
Trophoblast - Layer of cells on the outside of the blastocyst supplying structure and nourishment
Inner Cell Mass - Collection of embryoblast cells attached on one wall of the trophoblast layer

Question 8

Define implantation, cytotrophoblast and syncytiotrophoblast

Answer 8

Implantation - Process of a blastocyst joining to the uterine surface
Cytotrophoblast - Inner layer of the trophoblast
Syncytiotrophoblast - Transport barrier and outer layer of the trophoblast (multi-nucleated sheet)

Question 9

How does the embryonic disc form from the inner cell mass?

Answer 9

Inner cell mass differentiates into bilaminar disc made of epic lasts and hypoblasts below an amniotic cavity

Question 10

Define: bilaminar disc and germ layer

Answer 10

Bilaminar Disc - Layer of epiblasts and hypoblasts evolved from the embryoblast
Germ Layer - Group of cells in an embryo that contribute to formation of organs and tissues

Question 11

Define ectoderm, mesoderm and endoderm

Answer 11

Ectoderm - Outermost layer of cells or tissues of an embryo in early development
Mesoderm - Middle layer of cells or tissues of an embryo
Endoderm - Innermost layer of cells or tissues of an embryo

Question 12

Define Primitive Streak and Gastrulation

Answer 12

Primitive Streak - Transient structure whose formation marks the start of gastrulation
Gastrulation - Process by which the inner cell mass is converted into the trilaminar disc

Question 13

What is a trilaminar embryonic disc?

Answer 13

When an embryo exists as3 different germ layers - ectoderm, mesoderm and endoderm

Question 14

What are the derivatives of the ectoderm layer?

Answer 14

• Nervous system

- Epidermis

Question 15

What are the derivatives of the mesodermal layer?

Answer 15

• Heart
• Kidneys
• Bones
• Muscle
• Connective tissue

Question 16

What are the derivatives of the endoderm layers?

Answer 16

• Digestive tract
• Respiratory tract
• Urinary tract