Fetal Period

Question 1

6 Characteristics of an Embryo at Week 3

Answer 1

(1) A notochord forms in the center of the embryonic disk
(2) Gastrulation commences
(3) A neural groove (future spinal cord) forms over the notochord with a brain bulge at one end
(4) ) Somites, the divisions of the future vertebra, form
(5) Primitive heart tube is forming
(6) The crown-rump length is about 0.2 inches.

Question 2

9 Characteristics of an Embryo at Week 4

Answer 2

(1) The embryo measures 4 mm (1/8 inch) and begins to curve into a C shape.
(2) The heart bulges; begins to beat
(3) Branchial arches, that will form structures of the face and neck, form.
(4) The neural tube closes.
(5) Arm buds and a tail are visible.
(6) Pulmonary primordium appears.
(7) Hepatic plate, first traits of liver appear.
(8) Oropharyngeal membrane ruptures to form the future mouth.
(9) Anterior and posterior horns differentiate in the spinal cord

Question 3

8 Characteristics of an Embryo at Week 5

Answer 3

(1) The embryo measures (1/4 inch) in length.
(2) Lens pits and optic cups form the start of the developing eye.
(3) Nasal pits form.
(4) The brain divides into 5 vesicles
(5) Leg buds form and hands form as flat paddles on the arms.
(6) Rudimentary blood moves through primitive umbilical vessels connecting to the umbilical cord.
(7) The metanephros, precursor of the definitive kidney, starts to develop.
(8) The initial stomach differentiation begins.

Question 4

5 Characteristics of an Embryo at Week 6

Answer 4

(1) The embryo measures (1/2 inch) in length.
(2) Lungs begin to form.
(3) The brain continues to develop.
(4) Arms and legs have lengthened with foot and hand areas distinguishable.
(5) The hands and feet have digits, but may still be webbed.

Question 5

6 Characteristics of an Embryo at Week 7

Answer 5

(1) The embryo measures (3/4 inch) in length.
(2) Fetal heart tone (the sound of the heart beat) can be heard using Doppler.
(3) Nipples and hair follicles begin to form.
(4) Location of the elbows and toes are visible.
(5) Spontaneous limb movements may be detected by ultrasound.
(6) All essential organs have at least begun.

Question 6

10 Things that happen in weeks 8-10

Answer 6

(1) Intestines rotate.
(2) Facial features continue to develop.
(3) The eyelids are more developed.
(4) The external features of the ear begin to take their final shape.
(5) The head comprises nearly half of the fetus’ size.
(6) The face is well formed
(7) The limbs are long and thin.
(8) The fetus can make a fist with its fingers.
(9) Genitals appear well differentiated.
(10) Red blood cells are produced in the liver.

Question 7

When are all major external and internal structures are established? (the embryo has a distinctly human appearance)

Answer 7

During the 4th to 8th weeks

Question 8

What are teratogens?

Answer 8

are agents such as drugs and viruses that produce or increase the incidence of birth defects

Question 9

When is the CNS susceptible?

Answer 9

Weeks 3-20

Question 10

When are the limbs susceptible?

Answer 10

Weeks 4-7

Question 11

When is the heart susceptible?

Answer 11

Weeks 3-6

Question 12

When are the eyes and ears susceptible?

Answer 12

Weeks 4-8

Question 13

What are the 5 methods used to estimate fetal age?

Answer 13

) Crown-rump Length; 2) Head Circumference; 3) Length of Femur; 4) Length of Foot; 5) Abdominal Circumference

Question 14

What is the size of the embryo at week 4?

Answer 14

1/8 inch

Question 15

What is the size of the embryo at week 5?

Answer 15

1/4 inch

Question 16

What is the size of the embryo at week 6?

Answer 16

1/2 inch

Question 17

What is the size of the embryo at week 7?

Answer 17

3/4 inch (weighs 1 gram)

Question 18

What is a notable change that occurs during the fetal period?

Answer 18

There is a relative slowdown in the growth of the head compared with the rest of the body

Question 19

How much do “preterm” infants weigh?

Answer 19

750-1500 grams

Question 20

When can the genitalia of the fetuses be recognized ?

Answer 20

12-14 weeks

Question 21

When does the fetal period begin?

Answer 21

8 weeks after fertilization

Question 22

When does head hair appear?

Answer 22

By the beginning of the 20th week

Question 23

Around what time is the fetus is usually capable of extrauterine existence?

Answer 23

Approximately 26 weeks

Question 24

When does fat rapidly develop?

Answer 24

During the 26th to 29th weeks

Question 25

Describe the two components of the placenta

Answer 25

• A fetal part that develops from the chorionic sac, the outermost fetal membrane
• A maternal part that is derived from the endometrium, the mucous membrane comprising the inner layer of the uterine wall

Question 26

5 Functions and Activities of the placenta and fetal membranes

Answer 26

1) protection
2) nutrition
3) respiration
4) excretion
5) hormone production

Question 27

When is development of the maternal blood supply to the placenta complete?

Answer 27

By the end of the 1st trimester (12-13 weeks)

Question 28

What are the layers in which nutrients and oxygen from the mother must pass through in order to get to the fetus?

Answer 28

Syncytiotrophoblast
Cytotrophoblast
Mesoderm
Capillary endothelium
Basement membrane

Question 29

How many veins and arteries does the umbilical cord have?

Answer 29

2 Umbilical Arteries and 1 Umbilical Vein

Question 30

Describe Umbilical Arteries

Answer 30

They carry deoxygenated and nutrient poor blood AWAY from the fetus

Question 31

Describe Umbilical Veins

Answer 31

They carry oxygenated and nutrient rich blood TOWARD the fetal heart

Question 32

Describe fetal circulation from the placenta to the brain

Answer 32

Placenta –> Umbilical Vein –> Inferior Vena Cava –> Right Atrium –> Foramen Ovale –> Left Atrium –> Left Ventricle –> Head, Neck and Brain

Question 33

Blood bypasses the liver and lungs by of ______.

Answer 33

ductus arteriosus

Question 34

In utero what side of the heart is the “high pressure side”?

Answer 34

Right side

Question 35

How does typical circulation occur at birth?

Answer 35

The baby takes in a breath, which opens the lungs and clears its passages of fluid. Now the left side of the heart is the high pressure side, which closes the foramen ovale.