Embryology

Question 1

What happens in week 1

Answer 1

• A zygote forms and divides into a blastocyte
• Moves through the uterine tube to reach the uterine cavity
• The first division takes 36 hours but it takes less and less time after that
• Day 5 or 6 the blastula has reached the uterine cavity ready to implant into it

Question 2

What is an ectopic pregnancy and when does it happen

Answer 2

a pregnancy that occurs outside of the uterus: could occur if the cilia function is abnormal

Question 3

What are the main thing that happen in week 2?

Answer 3

• Implantation occurs in the uterine endodermal layer and the placenta begins to develop
• Cells that later form the embryo form a bilaminar disc
• Membranes sacs and cords begin to form

Question 4

What does the chorion do?

Answer 4

• The implantation process (chronic villi)
• Forms part of the placenta in due coarse
• Secretes human chronic gonadotropium (HCG) (this is what is detected during pregnancy). It tells the body to continue to produce oestrogen etc. so that the endometrium doesn’t get shed (increases until around 12 weeks in pregnancy)

Question 5

Describe the bilaminar disc and the cavities around it

Answer 5

• Amniotic cavity
• Epiblast (first layer of disc)
• Hypoblast (bottom layer of disc)
• Yolk sac

Question 6

What does the allantoic sac do?

Answer 6

collect waste (it gets bigger during pregnancy)

Question 7

What are the main functions of the placenta?

Answer 7

• Foetal nutrition
• Transportation of waste and gases
• Immune etc.

Question 8

What are the main events that happen in week 3?

Answer 8

• Formation of the germ layers
• Formation of the neural tube
• Development of somites
• The early development of the cardiovascular system

Question 9

What are the three germ layers?

Answer 9

• Ectoderm
• Mesoderm
• Endoderm

Question 10

What happens in weeks 4-8?

Answer 10

• Folding into a tube which starts as soon as the third week is complete due to heavy lateral mesoderm
• Heart starts to beat on day 24
• Gut formation in the endoderm
• Urogenital system formed from the intermediate mesoderm

Question 11

When does the trachea and the lung buds start do develop?

Answer 11

week 4

Question 12

What is a fistula?

Answer 12

An abnormal or surgically made passage between a hollow or tubular organ and the body surface, or between two hollow organs, TOF is a congenital disorder

Question 13

What is an atresia?

Answer 13

A condition where a passage or an orifice in the body is (usually abnormally) closed or absent

Question 14

Where is the visceral pleura from?

Answer 14

The splanchnic mesoderm

Question 15

What is the parietal pleura developed from?

Answer 15

The somatic mesoderm

Question 16

What is the embryonic period?

Answer 16

• Appears around the 26th day in the form of a respiratory diverticulum in the ventral part of the digestive tract
• The respiratory diverticulum creates a median trachea and two lateral pockets
• Simultaneously a vascular connection develops. The pulmonary arteries individuate at the 6th aortic arch

Question 17

What are the three stages of development of the lungs?

Answer 17

• The embryonic period (3-8 weeks)
• The foetal stage (7-40 weeks)
• The alveolar stage (32 weeks to 8 years)

Question 18

What are the stages of lung morphogenesis?

Answer 18

• Embryonic (3-8 weeks)
• Pseudo-glandular (5-17 weeks)
• Canalicular (16-26 weeks)
• Saccular (24-38 weeks)
• Alveolar (36 weeks to about 2-8 years)

Question 19

What congenital diseases can happen in the embryonic stage?

Answer 19

• Tracheal, laryngeal stenosis (narrowing of the airway)
• Pulmonary agenesis (failure if development of the primitive lung bud)
• Tracheal-esophageal fistula

Question 20

What congenital diseases can happen in the Pseudo glandular stage?

Answer 20

• Pulmonary seqestration (malformation of the lower respiratory tract
• Cyst adenomatoid malformation (pulmonary airway malformation)
• Cyst formation