Week 4 to 8 - Organogenetic Period

Question 1

During the fourth to eighth weeks period the embryo will develop the ___, the tissues will differentiate fast, so any exposure to teratogens during this period may cause congenital anomalies.

Answer 1

main organ systems

Question 2

Nervous and cardiovascular systems will begin to develop during weeks ______ which is important to support a live fetus.

Answer 2

4-8

Question 3

agents such as drugs and viruses that produce or increase the incidence of congenital anomalies.

Answer 3

Teratogens

Question 4

The normal development of an embryo can be divided into three phases, which are interrelated:

Answer 4

Growth, Morphogenesis, and Differentiation

Question 5

First phase: consists of cell division

Answer 5

Growth

Question 6

Second phase: _______, the development of shape, size, or other features of a particular organ or part of the whole of the body.

Answer 6

Morphogenesis

Question 7

Third phase: maturation of physiologic processes.

Answer 7

Differentiation.

Question 8

During the fourth week of development a significant event is the establishment of body form by folding of the flat trilaminar disc into a cylindrical embryo.

Answer 8

“Folding of the embryo”

Question 9

The fast growth of the embryo is responsible for the folding of the _____ and ______ planes.

Answer 9

median and horizontal

Question 10

Folding at the cranial and caudal ends occurs simultaneously. This causes constriction at the junction of the embryo and _______

Answer 10

umbilical vesicle (yolk sac).

Question 11

As the embryo’s head folds, heart will be dorsally pushed to directly above the ____. This is important for proper location of the heart. It is rare to see heart beating outside of chest.

Answer 11

diaphragm

Question 12

HEAD FOLD: During week 4, the neural folds in the cranial region thickened forming the _____ of the brain

Answer 12

primordium

Question 13

HEAD FOLD: The developing embryo projects into the ____ and as development advances it grows beyond the oropharyngeal membrane and overhangs the developing heart.

Answer 13

amniotic cavity

Question 14

The _______, primordial heart, pericardial coelom, and oropharyngeal membrane move onto the ventral surface of the embryo. After folding the septum transversum lies caudal to the heart where later it will develop into the central tendon of the diaphragm.

Answer 14

septum transversum or transverse septum

Question 15

After folding, the pericardial coelom lies ventral to the heart and cranial to the septum transversum and the intraembryonic coelom communicates on each side with the ______

Answer 15

extraembryonic coelom

Question 16

In week four of development, the heart is located outside of the chest. There is no space or _______ cavity because it is folding.

Answer 16

Pericardial

Question 17

Head Fold: During folding, part of the endoderm of the umbilical vesicle goes into the embryo as the ____ (primordium of pharynx, esophagus, etc).

Answer 17

foregut

Question 18

Head fold: The foregut lies between the brain and heart, and the ____.

Answer 18

oropharyngeal membrane

Question 19

Head fold: The ____ will form the digestive track from the esophagus to a portion of the anus.

Answer 19

Endoderm

Question 20

Head fold: From the foregut, a small attachment comes interior to the esophagus, forming the ____. The embryo will begin swallowing.

Answer 20

Trachea

Question 21

Tail fold: The growing of the ______ (spinal cord primordium) causes the tail to grow.

Answer 21

neural tube

Question 22

The ______ or tail region projects over the cloacal membrane.

Answer 22

caudal eminence

Question 23

The future site of the anus is called the

Answer 23

cloacal membrane

Question 24

The ____ or the primordium of the descending colon is incorporated to the embryo during folding and is part of the endodermal layer.

Answer 24

hindgut

Question 25

The ___ or primordium of the urinary bladder and the rectum forms when the terminal part of the hindgut dilates slightly.

Answer 25

cloaca

Question 26

The ____ or primordium of the umbilical cord is now attached to the ventral surface of the embryo, and a diverticulum of the umbilical vesicle called the allantois, is partially incorporated into the embryo.

Answer 26

connecting stalk

Question 27

During ___ the three layers that will give rise to the primordia of all tissues and organs are formed: Ectoderm, Mesoderm and Endoderm.

Answer 27

gastrulation

Question 28

This germ layer gives rise to the CNS, PNS, sensory epithelia of the eye, ear, and nose. Epidermis and its appendages; mammary glands; pituitary gland and enamel of teeth

Answer 28

Ectoderm

Question 29

Neural crest cells derived from ___ gives rise to the cells of the spinal and cranial nerves.

Answer 29

neuroectoderm

Question 30

Germ layer that gives rise to connective tissue; cartilage; bone; striated and smooth muscles; heart blood and lymphatic vessels; kidneys; ovaries; testes; genital ducts; serous membrane lining the body cavities and cortex of suprarenal glands.

Answer 30

Mesoderm

Question 31

Mesoderm forms the \_\_\_, which forms primordia for muscle cells. This will migrate and help information for all of the muscles.

Answer 31

somite

Question 32

Reproductive system development occurs at week ___ in the male and around week ___ in the female.

Answer 32

7,12

Question 33

This germ layer gives rise to the epithelial lining of the gastrointestinal and respiratory tracts, parenchyma of tonsils, thyroid and parathyroid glands, thymus, liver and pancreas, epithelial lining of the urinary bladder; urethra, tympanic cavity and pharyngotympanic or auditory tube.

Answer 33

Endoderm

Question 34

Which germ layer are all digestive tubes a part of?

Answer 34

endoderm

Question 35

At the beginning of week ___ the embryo has four to 12 somites. The neural tube is formed opposite the somites, widely open at the rostral and caudal neuropores, which are openings at the cranial and caudal regions.

Answer 35

four

Question 36

In a 24 days old embryo the first two ___ are visible. The first arch is the mandibular arch and will give rise to mandible or lower jaw and the maxilla or upper jaw. The second arch or hyoid arch. The heart produces a large ventral prominence and pumps blood.

Answer 36

pharyngeal arches

Question 37

The forebrain produces a prominent elevation of the head, called the\_\_\_\_.

Answer 37

forebrain prominence.

Question 38

By day 26, the ___ are seen as small swellings of the ventrolateral body walls

Answer 38

limb buds

Question 39

The \_\_\_, which are the primordia of the internal ears, are also visible by day 26.

Answer 39

otic pits

Question 40

The \_\_\_\_, are ectodermal thickenings and they indicate the future lenses of the eyes. (day 26)

Answer 40

lens placodes

Question 41

Towards the end of week four, there is rapid development of the

Answer 41

forebrain

Question 42

By day 28, \_\_\_, the caudal eminence, which is a long tail-like, becomes a characteristic feature.

Answer 42

Carnegie stage 13

Question 43

At day 28 a rudimentary ____ system, is established.

Answer 43

cardiovascular

Question 44

By the end of the fourth week, the caudal ___ is usually closed

Answer 44

neuropore

Question 45

During the fifth week, changes occur mostly on the head, which changes fast due to the growing of the ___ and facial prominences.

Answer 45

brain

Question 46

In the fifth week, the second ____ overgrows the third and fourth arches, forming a lateral ectodermal depression on each side the cervical sinus.

Answer 46

pharyngeal arch

Question 47

A six week embryo already show reflex response to \_\_\_.

Answer 47

touch

Question 48

During the sixth week, the upper limbs differentiate and show the elbow, large handplates, and the primordia of the fingers, called \_\_\_

Answer 48

digital rays.

Question 49

The lower limbs develop \_\_\_days after the upper limbs.

Answer 49

4 to 5

Question 50

In the sixth week the ____ and the external acoustic ___ form.

Answer 50

auricular hillocks meatus

Question 51

During the sixth week, the intestines enter the extraembryonic coelom in the proximal part of the \_\_\_.

Answer 51

umbilical cord.

Question 52

The ____ in the sixth week of development is common in embryos this age, and is because the abdominal cavity is too small at this age.

Answer 52

umbilical herniation

Question 53

The hernia formed during week six in most embryos is very thick, but by week ___ the diameter decreases significantly.

Answer 53

8

Question 54

The 7th week of development is characterized by the changes on the \_\_\_

Answer 54

limbs.

Question 55

During the 7th week, ___ appear between the digital rays in the handplates, indicating the future fingers

Answer 55

Notches

Question 56

In week 7, the communication between the ___ and umbilical vesicle is reduced.

Answer 56

primordial gut

Question 57

Ossification of the bones of the upper limbs begins during week

Answer 57

7

Question 58

Cartilage and bone will ossify during week 7. The ___ ossifies first, followed by the femur. The length of the femur is usually measured and compared with other babies of same age.

Answer 58

clavicle

Question 59

The 8th week marks the end of the ___ period.

Answer 59

embryonic

Question 60

During the eighth week, digits of the hand are separated, but \_\_\_

Answer 60

webbed

Question 61

The ____ is still present at week 8, but very small

Answer 61

caudal eminence

Question 62

The ___ appears during week 8 and forms a band around the head.

Answer 62

scalp vascular plexus

Question 63

Ossification begins in the ___ at week 8

Answer 63

femur

Question 64

The ___ start closing during week 8

Answer 64

eyelids

Question 65

In week 8, the ____ are still in the proximal portion of the umbilical cord.

Answer 65

intestines

Question 66

During the eighth week of development, ____ begins to appear

Answer 66

external genitalia

Question 67

ONLY after week 8 you will be able to know if formation of __ and ___ is complete

Answer 67

hands and limbs

Question 68

Obstetricians date pregnancy from the first day of the LNMP= Last Normal Menstrual Period. This is the \_\_\_

Answer 68

gestational age.

Question 69

The \_\_\_, begins at fertilization, two weeks after the LNMP

Answer 69

embryonic age

Question 70

Errors in establishing the LNMP in woman who become pregnant after cessation of oral contraception are frequent, due to the fact that the \_\_\_affect the time of ovulation.

Answer 70

hormones

Question 71

\_\_\_ assessment of the size of the chorionic (gestational) cavity and its embryonic contents enables clinicians to obtain an accurate estimate of the date of conception.

Answer 71

Ultrasound

Question 72

Around week four of development, transvaginal US you will see gestational sac. As the embryo grows, cavity of gestational sac will \_\_\_\_

Answer 72

Decrease

Question 73

\_\_\_\_ to ____ length is used to determine the age and expected date of delivery

Answer 73

crown to rump

Question 74

Estimation of the age of embryos recovered after a \_\_\_\_, is determined from their external characteristics and measurements of their length.

Answer 74

spontaneous abortion

Question 75

The appearance of the developing ____ is a helpful criterion for estimating embryonic age.

Answer 75

limbs

Question 76

You count the number of ___ after a spontaneous abortion to estimate embryonic age.

Answer 76

somites