Embryology

Question 1

On what day does the primary heart field form?

Answer 1

16-18

Question 2

When does the secondary heart field develop?

Answer 2

Days 20-21

Question 3

What forms the primary heart field?

Answer 3

Migration of progenitor heart cells

Question 4

What does the primary heart field go on to form?

Answer 4

Atria, left ventricle and most of right ventricle

Question 5

What does the secondary heart field become?

Answer 5

Remainder of right ventricle and the outflow tract

Question 6

Where are the heart fields from?

Answer 6

Mesoderm

Question 7

What does the inner cell mass of the morula become?

Answer 7

Embryo proper

Question 8

What does the outer cell mass of morula become?

Answer 8

Trophoblast then placenta

Question 9

What does the inner cell mass of the blastocyst become?

Answer 9

Embryoblast

Question 10

What does the outer cell mass of the blastocyst become?

Answer 10

Trophoblast

Question 11

What are the 2 layers the trophoblast differentiates into on day 8?

Answer 11

Cytotrophoblast (mononucleate)
Syncytiotrophoblast

Question 12

What forms when the oocyte and spermatozoa fuse?

Answer 12

Zygote

Question 13

Where does fertilization take place?

Answer 13

Ampullary region of fallopian tube

Question 14

What are the two processes that must take place for fertilization?

Answer 14

Capacitation and Acrosome reaction

Question 15

What happens in capacitation?

Answer 15

In the female reproductive tract
Period of conditioning sperm
Glycoprotein coat and seminal plasma over the acrosome removed for easier enzyme release
Sperm must undergo this to be able to continue

Question 16

What happens in the acrosome reaction?

Answer 16

After binding to ZP, capacitated sperm can pass through corona radiata
Penetration of the ZP through enzyme release (e.g. acrosin)

Question 17

What are the phases of fertilization?

Answer 17

Penetration of corona radiata by capacitated sperm
Sperm release acrosin to penetrate ZP
Sperm contact oocyte
Enzymes released from oocyte cortical granules
Zona reaction initated by enzymes prevent more sperm entering by inactivating receptors
Sperm and egg plasma membranes fuse

Question 18

What is cleavage?

Answer 18

Series of fast mitotic divisions of zygote
Starts on Day 2 to reach 2 cell stage

Question 19

When does the 16-cell morula form?

Answer 19

Day 3

Question 20

What does the embryoblast differentiate into?

Answer 20

Hypoblast and epiblast

Question 21

What happens on day 9?

Answer 21

Lacunar stage of trophoblast development

Question 22

When is uteroplacental circulation established?

Answer 22

Day 12

Question 23

What does the epiblast give rise to?

Answer 23

The 3 germ layers

Question 24

What is gastrulation?

Answer 24

A process in week 3 that establishes the 3 germ layers

Question 25

What forms during gastrulation on day 15-16?

Answer 25

The primitive streak on the embryo

Question 26

What makes up the primitive streak?

Answer 26

Primitive node (containing pit) and groove Groove separates body into left and right

Question 27

What do the different cells of the trilaminar disc become?

Answer 27

Some epiblast displace ventral hypoblast and form endoderm Some other epiblast in groove from mesoderm Epiblast cells not in groove form ectoderm

Question 28

What happens on day 15?

Answer 28

Cranial and caudal ectoderm fuse with endoderm to form two bilaminar regions

Question 29

What does the cranial bilaminar region of ectoderm form?

Answer 29

Oropharyngeal membrane which disintegrates in week 4 to form mouth

Question 30

What does the caudal bilaminar region of the ectoderm form?

Answer 30

Cloacal membrane which disintegrates in week 7 to form anal opening and GU tracts

Question 31

What happens on day 17?

Answer 31

Mesoderm forms notochord which secretes SHH protein

Question 32

What happens on day 20?

Answer 32

Neurulation

Question 33

What happens in neurulation?

Answer 33

Ectoderm cells thicken and form neural plate Mesoderm differentiates

Question 34

What does the mesoderm differentiate into?

Answer 34

Paraxial, intermediate and lateral plate mesoderm

Question 35

What does the paraxial mesoderm form?

Answer 35

Develops into pairs of somites, 3 pairs a day. Somites can be split into sclerotome, myotome and dermatome

Question 36

What do the different regions of somites form? (paraxial mesoderm)

Answer 36

Sclerotome: bones and cartilage Myotome: muscle Dermatome: dermis

Question 37

What does the intermediate mesoderm form?

Answer 37

Adrenal cortex, kidneys, testes, ovaries (UG structures)

Question 38

What does the lateral plate mesoderm give rise to?

Answer 38

Serous membranes CVS system and thoracic and abdominal cavities Pleura Soft tissues of arms and legs Muscular gut wall

Question 39

What does the ectoderm form?

Answer 39

Otic placode (cranial): cochlear and inner ear Lens placode: lens and cornea Sensory epithelium Glands (sweat, pituitary, mammary)

Question 40

What does the endoderm form?

Answer 40

Epithelial lining of gut tube Tonsils Thyroid and parathyroid glands Parts of liver Pancreas and gallbladder Urinary bladder and epithelial lining of urethra

Question 41

What is the gut tube divided into?

Answer 41

Foregut Midgut Hindgut

Question 42

What happens in 3rd week of development?

Answer 42

notochord appears in the mesoderm

Question 43

What does the notochord do?

Answer 43

secretes growth factors which stimulate the differentiation of the overlying ectoderm into neuroectoderm – forming a thickened structure known as the neural plate

Question 44

What do the lateral edges of the neural plate form?

Answer 44

Neural folds

Question 45

What forms the neural tube?

Answer 45

The 2 neural folds meeting in the midline

Question 46

What does the neural crest give rise to?

Answer 46

melanocytes, craniofacial cartilage and bone, smooth muscle, peripheral and enteric neurons and glia

Question 47

What is neuralation?

Answer 47

formation of neural tube achieved by end of week 4

Question 48

When does pronephros appear?

Answer 48

4th week of development

Question 49

What are pronephros, the mesonephros, and the metanephros derived from?

Answer 49

Urogenital ridge

Question 50

What forms the definitive kidney?

Answer 50

Metanephros

Question 51

What is the collecting system of the kidney derived from?

Answer 51

Uteric bud

Question 52

What is the excretory system of the kidney derived from?

Answer 52

metanephric blastema

Question 53

What does the collecting system form?

Answer 53

ureter, renal pelvis, major and minor calyces and collecting tubules

Question 54

What does the excretory system form?

Answer 54

nephron

Question 55

In weeks 4-7, what does the urorectal septum divide the cloaca into?

Answer 55

Urogenital sinus Anal canal

Question 56

What does the urogenital sinus form?

Answer 56

Bladder Urethra Reproductive tract

Question 57

What is the respiratory system derived from?

Answer 57

primitive gut tube

Question 58

What forms the R and L bronchi?

Answer 58

Buds from the respiratory diverticulum

Question 59

What does the ductus arteriosus do?

Answer 59

shunts blood from the pulmonary artery directly to the aortic arch

Question 60

What are type 1 pneumocytes?

Answer 60

basic simple squamous epithelial cells comprise 90% of the alveolus.

Question 61

What are type 2 pneumocytes?

Answer 61

simple cuboidal cells which comprise the remaining 10% and are responsible for the production of surfactant

Question 62

What does surfactant allow?

Answer 62

expand our lungs with minimal effort

Question 63

When do the alveoli start to develop?

Answer 63

Week 26

Question 64

What are the 6 regions of the primitive heart tube

Answer 64

Aortic roots (Arterial poles) Truncus arteriosus Bulbus cordis Ventricle Atrium Sinus venosus (Venous poles)

Question 65

What 2 things are responsible for the r to l shunt in developing atria?

Answer 65

ostium secundum and foramen ovale

Question 66

What does the septum primum do?

Answer 66

Splits atria into 2

Question 67

What is the adult remnant of the foramen ovale?

Answer 67

Fossa ovalis

Question 68

What is the adult remnant of the ductus arteriosus?

Answer 68

Ligamentum arteriosum

Question 69

What is the adult remnant of the ductus venosus?

Answer 69

Ligamentum venosum

Question 70

What is the adult remnant of the umbilical vein?

Answer 70

Ligamentum teres