Third month to birth, the fetus and placenta

Embryology Exam 3

Period from beginning of the 9th week to birth:

fetal period

What occurs in the fetal period?

Maturation of tissues and organs, rapid growth of body

How is the fetus measured?

Crown rump length (CRL) or Crown-heel length (CHL)

Weight growth is most rapid in the:

last 2 months

Length growth is most rapid in the:

3rd, 4th, 5th months

Length of pregnancy is considered how many days/weeks after onset of last normal menstrual period?

280 days/40 weeks

If pregnancy is measured after fertilization, how many days/weeks is it?

266 days/38 weeks

At the beginning of the 3rd month, the ___ constitutes for half of the CRL.

head

By the beginning of the 5th week, the head is:

1/3 of CHL

By birth, the head is how much of the CHL?

1/4

Core monthly changes in the 3rd month of pregnancy (face):

1. Face appears more human

2. Eyes move to ventral aspect of the face

3. Ears come to lie close to correct position of the head

4. Limbs reach relative length in comparison to the rest of the body

5. Lower limbs are a little shorter/less developed than upper limbs

In the 3rd month, primary ossification centers present in the long bones and skull by what week?

Week 12

The external genitalia develop in this week of pregnancy, so sex of the fetus can be determined by an ultrasound.

Week 12

By week 12, the intestinal loops have:

withdrawn into the abdominal cavity

At birth, the umbilical cord is how long?

½ in diameter

50-60 cm

A false knot of the umbilical cord is also known as:

tortuous

If the umbilical cord is too long, what can happen?

Encircle neck

If the umbilical cord is too short, what can happen?

Difficulties during delivery by pulling the placenta from attachment in the uterus

The two-vessel cord has a 20% chance of what?

cardiac and vascular defects

Tears in the amnion can result in:

amniotic bands

Why are amniotic bands dangerous?

May encircle a part of the fetus, limbs or digits. It can cause amputations, ring constritctions, and other defects can occur

the large sac containing amniotic fluid (what the fetus is suspended in):

Amniotic cavity

Amniotic fluid is replaced how often?

Every 3 hours

What are the 3 main functions of the amniotic cavity?

1. Absorb jolts

2. Allow for fetal movements

3. Prevents adherence of embryo to amnio

Excess amniotic fluid is also known as:

Polyhydraminos, hydraminos

Polyhydraminos or hydraminos is associated with:

Anencephaly and esophageal atresia

Insufficient fluid is known as:

Oligohydraminos

Oligohydraminos is related to:

renal agenesis

the umbilical cord is surrounded by amnion and contains:

2 umbilical arteries

1 umbilical vein

Wharton jelly (protective cushion vessels)

An example of Rh compatibility:

Baby Rh+ and mom Rh-

If there is an Rh incompatibility, the mothers antibodies will do what?

Attack and hemolyze fetal red blood cells

Rarely anemia becomes very severe, leading to (from Rh incompatibility):

Fetal hydrops

Fetal hydrops is:

edema and effusions into body cavities

Function of the placenta:

1. Exchange of gases

2. Exchange of nutrients and electrolytes

3. Transmission of maternal antibodies, providing fetus with passive immunity

4. Production of hormones

5. Detoxification of some drugs

Cotyledons receive blood through what?

Spiral arteries that enter intervillous spaces at regular intervals

The maternal blood in the intervillous lakes is renewed how often?

3-4 times per minute

As pressure decreases, blood flows toward the decidua and enters the:

endometrial veins (back into material circulation)