Developmental Origins of Disease - Symposia Part 1

Question 1

Embryology = …

Answer 1

Embryology- Study of the Embryo (Pre Natal Development)

Question 2

Why study embryology and development?

Answer 2

• how normality arises
• how abnormality arises
• position and relevance of anatomy
• basis of obstetric and paediatric practice

Question 3

Fertilization- Day 1

• Sperm and Ovum meet in … … (usually …) how many hours after ovulation?
• Penetration of … radiate and Zona …
• Fusion and 2nd … division
• … reaction makes ovum … to other sperm
• End- Zygote- has diploid (… chromosomes)

Answer 3

• Sperm and Ovum meet in Uterine Tube (usually ampulla) 12-24 hours after ovulation.
• Penetration of Corona radiate and Zona pellucida
• Fusion and 2nd meiotic division
• Acrosome reaction makes ovum impermeable to other sperm
• End- Zygote- has diploid (46 chromosomes)

Question 4

Fertilization - Days 2-3

• … is the rapid process of mitotic divisions
• First mitotic division is around … hours post fertilization.
• By day 3 … cell embryo
• Each cell is known as a ….
• Solid sphere is known as a ….

Answer 4

• Cleavage is the rapid process of mitotic divisions
• First mitotic division is around 30 hours post fertilization.
• By day 3 16 cell embryo
• Each cell is known as a blastomere.
• Solid sphere is known as a morula.

Question 5

Fertilization- Days 4-5

• Morula develops a cavity and becomes known as a …
• The outer layer of the … thins out and becomes the … - this helps form the placenta
• The rest of the cells move (are pushed up) to form the inner cell mass. This creates an embryonic …
• The … has now reached the uterine … and is ready for implantation.

Answer 5

• Morula develops a cavity and becomes known as a blastocyst.
• The outer layer of the blastocyst thins out and becomes the trophoblast this helps form the placenta
• The rest of the cells move (are pushed up) to form the inner cell mass. This creates an embryonic pole.
• The blastocyst has now reached the uterine lumen and is ready for implantation.

Question 6

Fertilization - Days 6-7

• Bilaminar Disc- As the embryo starts to implant it forms two layers.
• Inner cell mass differentiates into two layers: … and …
  
  • These two layers are in contact.
• … forms extraembryonic membranes
• … forms embryo
• … cavity develops within the … mass

Answer 6

• Bilaminar Disc- As the embryo starts to implant it forms two layers.
• Inner cell mass differentiates into two layers: epiblast and hypoblast.
  
  • These two layers are in contact.
• Hypoblast forms extraembryonic membranes
• Epiblast forms embryo
• Amniotic cavity develops within the epiblast mass

Question 7

Primary Yolk Sac Day 6-8

• Derived from the … is the exocoelomic membrane.
  
  • (Also known as: Extraembryonic …/membrane)
• This creates a cavity known as the Yolk Sac
• The Yolk Sac contains nutrients that supply the embryo before the … functions.

Answer 7

• Derived from the hypoblast is the exocoelomic membrane.
  
  • (Also known as: Extraembryonic hypoblast/membrane)
• This creates a cavity known as the Yolk Sac
• The Yolk Sac contains nutrients that supply the embryo before the placenta functions.

Question 8

Fertilization - Week 3 plus

• At the start of week 3 the embryo (bilaminar disc) develops further by forming 3 distinct layers (this process is known as …).
• Initiated by … streak.
• Two layers have already formed (epiblast and hypoblast).
• The epiblast becomes known as …
• The hypoblast is replaced by cells from the epiblast and becomes …
• The epiblast gives rise to the third layer the ….
• The hypoblast …. The epiblast gives rise to all three germ layers.

Answer 8

• At the start of week 3 the embryo (bilaminar disc) develops further by forming 3 distinct layers (this process is known as gastrulation).
• Initiated by primitive streak.
• Two layers have already formed (epiblast and hypoblast).
• The epiblast becomes known as ectoderm
• The hypoblast is replaced by cells from the epiblast and becomes endoderm
• The epiblast gives rise to the third layer the mesoderm.
• The hypoblast degenerates. The epiblast gives rise to all three germ layers.

Question 9

Fertilization - Week 4 plus

• By 4th week the flat disc has to fold into 2 directions
  
  • … (cephalocaudal) (day …) begins so that head and tail are brought closer.
  • … (transverse) (day …) brings the amniotic cavity down, creating the future … tube inside the peritoneal cavity.

Answer 9

• By 4th week the flat disc has to fold into 2 directions
  
  • Longitudinal (cephalocaudal) (day 21) begins so that head and tail are brought closer.
  • Lateral (transverse) (day 18) brings the amniotic cavity down, creating the future gut tube inside the peritoneal cavity.

Question 10

Mesoderm

• Either side of the … is the mesoderm.
• It is formed in three parts (…, … and … plate)

Answer 10

• Either side of the notocord is the mesoderm.
• It is formed in three parts (paraxial, intermediate and lateral plate)

Question 11

Paraxial Mesoderm- Somites

• Paraxial mesoderm undergoes further differentiation into paired blocks of tissue- somites
• …-… pairs eventually formed
• Somites undergo differentation to form … and …
  
  • … form connective tissue and skeletal muscle
  • … form bone and cartilage- vertebral arch

Answer 11

• Paraxial mesoderm undergoes further differentiation into paired blocks of tissue- somites
• 42-44 pairs eventually formed
• Somites undergo differentation to form dermomyotomes and sclerotomes
• Dermomyotomes form connective tissue and skeletal muscle
• Sclerotomes form bone and cartilage- vertebral arch

Question 12

Somites undergo differentation to form dermomyotomes and sclerotomes:

• … form connective tissue and skeletal muscle
• … form bone and cartilage- vertebral arch

Answer 12

Somites undergo differentation to form dermomyotomes and sclerotomes:

• dermomyotomes form connective tissue and skeletal muscle
• sclerotomes form bone and cartilage- vertebral arch

Question 13

Intermediate Mesoderm- Urogenital system

• Gives rise to – …, …, … ducts and associated glands

Answer 13

• Gives rise to – kidneys, gonads, urogenital ducts and associated glands

Question 14

Label the picture (somites)

Answer 14

Question 15

Lateral Plate Mesoderm- parietal and visceral layers

• Continuous with the … sac and … sac.
  
  • … sac mesoderm- Parietal or somatic layer
  • … sac mesoderm- Splanchnic layer
• … cells will become the membranes of the body (pericardium, pleura, peritoneum)

Answer 15

• Continuous with the amniotic sac and yolk sac.
  
  • Amniotic sac mesoderm- Parietal or somatic layer
  • Yolk sac mesoderm- Splanchnic layer
• Mesodermal cells will become the membranes of the body (pericardium, pleura, peritoneum)

Question 16

• Amniotic sac mesoderm- … or … layer
• Yolk sac mesoderm- … layer

Answer 16

• Amniotic sac mesoderm- Parietal or somatic layer
• Yolk sac mesoderm- Splanchnic layer

Question 17

Intraembryonic coelom

• All cavities become lined with lateral plate mesoderm to form the parietal layer (… mesoderm) and the visceral layer (… mesoderm)
• Initially a horseshoe shaped cavity
• Intraembryonic cavity is … shaped.
• Bend in the … becomes … cavity.
• Limb of … becomes 2 cavities … (pleural) and … cavities.

Answer 17

• All cavities become lined with lateral plate mesoderm to form the parietal layer (somatic mesoderm) and the visceral layer (splanchnic mesoderm)
• Initially a horseshoe shaped cavity
• Intraembryonic cavity U shaped.
• Bend in the U becomes pericardial cavity.
• Limb of U becomes 2 cavities pericardioperitoneal (pleural) and peritoneal cavities.

Question 18

Fertilization Overview

Answer 18

Question 19

Somites undergo differentiation to form: (which one?)

• Paraxial mesoderm
• Lateral plate mesoderm
• Dermomyotomes
• Neural crest
• Pronephros

Answer 19

• Dermomyotomes- that forms connective tissue and skeletal muscle
• Also sclerotomes- bone and cartilage- vertebral arch