Biology Chapter on Implantation

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Questions and Answers

What is the main function of the umbilical cord's single vein?

To carry nutrients from the fetus to the placenta

To provide oxygen to the fetus

To carry blood from the placenta to the fetus (correct)

To transport waste products from the fetus to the placenta

Which type of stem cells is capable of developing into any body cell type?

Totipotent stem cells (correct)

Multipotent stem cells

Pluripotent stem cells

Unipotent stem cells

What characterizes the rate of blood flow through the umbilical cord at term?

It increases dramatically to 500 mL/min

It is 350 mL/min and rapid (correct)

It decreases to 150 mL/min

It remains static without variations

In which direction does development proceed during zygote growth?

Cephalocaudal direction Signup and view all the answers

Which primary germ layer is responsible for forming nerve, brain, and skin cells?

Ectoderm Signup and view all the answers

How many arteries are present in the umbilical cord?

Two arteries Signup and view all the answers

What is the function of blood withdrawal from the umbilical vein?

To assess fetal well-being or for treatment Signup and view all the answers

Which statement about the umbilical cord is true?

Its structure includes one vein and two arteries. Signup and view all the answers

At what time after fertilization does implantation typically occur?

8 to 10 days Signup and view all the answers

Which layer of the inner cell mass is responsible for forming skin and the nervous system?

Ectoderm Signup and view all the answers

What term describes the process where the blastocyst attaches to the uterine endometrium?

Apposition Signup and view all the answers

What is the primary role of the mesoderm during embryonic development?

Forms bones, muscles, heart, and blood vessels Signup and view all the answers

What is a possible consequence of abnormal implantation?

Uterine cavity leakage of blood Signup and view all the answers

What happens to the blastocyst on approximately the 4th day after ovulation?

It sheds the last residues of the corona and zona pellucida Signup and view all the answers

What is the primary function of the trophoblast during implantation?

Develops into the placenta Signup and view all the answers

What occurs during the process of invasion in implantation?

The blastocyst settles into the endometrium Signup and view all the answers

What is the function of vernix caseosa during pregnancy?

To protect the skin from macerating in utero Signup and view all the answers

What indicates the presence of oligohydramnios?

A deficiency in fetal urine production Signup and view all the answers

At which week does urine begin to form in the fetus?

12th week Signup and view all the answers

What occurs if testosterone is deficient in male fetus development?

Development of female organs by the müllerian duct Signup and view all the answers

Which factor contributes to the fetus developing temporary passive immunity?

IgG maternal antibodies crossing the placenta Signup and view all the answers

What is the significance of the primitive tail during fetal development?

It regresses as the fetus develops Signup and view all the answers

What condition is indicated when the kidneys are present but not essential in the early weeks of pregnancy?

Kidneys are not yet functional Signup and view all the answers

Which disease is NOT mentioned as one for which the fetus will receive passive immunity from maternal antibodies?

Tuberculosis Signup and view all the answers

What is the primary function of Doppler umbilical velocity measurement?

To measure the velocity of red blood cells in fetal vessels Signup and view all the answers

How does B-mode scanning contribute to ultrasonography?

It produces a gray-scale image of anatomical structures. Signup and view all the answers

When can fetal ECGs typically begin to be recorded, according to standard practices?

As early as the 11th week of pregnancy Signup and view all the answers

What aspect of the placenta is primarily evaluated in placental grading?

The age of the placenta based on calcium deposits Signup and view all the answers

Why is fetal ECG considered inaccurate before the 20th week of pregnancy?

Fetal electrical conduction is too weak. Signup and view all the answers

At which week of development can the baby begin to hear?

Week 8 Signup and view all the answers

Which of the following organs begins to take shape by the end of the third week?

Liver Signup and view all the answers

What significant development occurs during Week 12?

All organ systems are functional. Signup and view all the answers

During which week does the fetal heart pump several quarts of blood every day?

Week 14 Signup and view all the answers

What can the baby do by Week 11 of development?

Grasp objects placed in its hand Signup and view all the answers

What occurs in the baby during the fourth month?

Bone marrow starts to form. Signup and view all the answers

What developmental milestone is achieved by the end of Month 4?

Legal viability if cared for is possible. Signup and view all the answers

By which week can the baby start to hiccup?

Week 5 Signup and view all the answers

Study Notes

Implantation

Implantation occurs approximately 8 to 10 days after fertilization
The blastocyst sheds the last residues of the corona and zona pellucida after 3 or 4 days of free floating
The blastocyst brushes against the rich uterine endometrium
The trophoblast attaches to the surface of the endometrium and settles down into its soft folds
The inner cell mass forms the fetus

Inner Cell Mass

The inner cell mass has three layers
- Ectoderm which forms skin and nervous system
- Mesoderm which forms bones, muscles, heart and blood vessels
- Endoderm which forms mucous membranes and glands

Implantation Bleeding

Maternal blood fills the cavities in the trophoblast just before it is completely covered
Some blood might leak into the uterine cavity

Amniotic Membrane

The amniotic membrane has no nerve supply
It is covered with amniotic fluid

Umbilical cord

The umbilical cord contains one vein and 2 arteries
The vein carries blood from the placental villi to the fetus
The arteries carry blood from the fetus back to the placental villi
Blood can be withdrawn from the umbilical vein or transfused into the vein during intrauterine life

Fetal Circulation

The blood flow rate at term is 350 mL/min
The cord is unlikely to twist or knot due to its rapid flow

Fetal Development

Development proceeds in a cephalocaudal direction
Primary germ layers form
- Ectoderm arises from the amniotic cavity
- Entoderm arises from the yolk sac

Fetal Growth

The fetus has soft downy hairs called lanugo
The fetus is covered in a cheese-like substance called vernix caseosa which aids lubrication and prevents skin maceration

Immune System

Maternal IgG antibodies cross the placenta
They provide temporary passive immunity for the fetus
This protects the fetus from illnesses like polio, rubella, rubeola, diphtheria, tetanus, infectious parotitis, hep B, and pertussis
The fetus is susceptible to herpes virus as there is little or no immunity
The level of immunity peaks at birth and decreases over the next 8 months
Immunization is started as passive immunity declines

Urinary System

Kidneys form at the end of week 4
Urine is formed by week 12
Urine is excreted into the amniotic fluid by week 16
The fetus excretes 500 mL of urine/day at term
Oligohydramnios suggests fetal issues

Fetal Growth Milestones

Fertilization (day 1) - all human chromosomes are present and unique human life begins
Day 6: embryo begins implantation in the uterus
Day 22: heart begins to beat with the child's own blood
Week 3: backbone, spinal column and nervous system are forming
Week 4: Length: 0.75 to 1 cm; Weight : 400 mg
Week 5: eyes, legs, and hands begin to develop
Week 6: brain waves are detectable; mouth and lips are present; fingernails are forming
Week 7: eyelids, toes form, nose distinct; the baby is kicking and swimming
Week 8: every organ is in place, bones begin to replace cartilage, and fingerprints begin to form; Length : 2.5 cm; Weight : 20 g
Week 9 and 10: teeth begin to form, fingernails develop. The baby can turn his head, and frown; the baby can hiccup
Weeks 10 and 11: the baby can "breathe" amniotic fluid and urinate; the baby can grasp objects placed in its hand; all organ systems are functioning; The baby has a skeletal structure, nerves, and circulation
Week 11: the baby can grasp objects placed in its hand; all organ systems are functioning
Week 12: the baby has all of the parts necessary to experience pain, including nerves, spinal cord, and thalamus; Vocal cords are complete; The baby can suck its thumb; Length : 7 to 8 cm; Weight :45 g; sex is distinguishable by outward appearance; Kidney secretion has begin
Week 14: the heart pumps several quarts of blood through the body every day; arms and legs are developed
Week 15: the baby has an adult's taste buds; pupils are capable of reacting to light;
Month 4: bone marrow is now beginning to form; the heart is pumping 25 quarts of blood a day; the baby will be 8-10 inches in length and will weigh up to half a pound

Ultrasound

Ultrasound image depends on the type of process used
B-mode scanning produces a sonogram
It allows patterns to merge and form a picture

Doppler Umbilical Velocity

Measures the speed or rate of red blood cells in the uterine and fetal vessels
Assesses blood flow through uterine blood vessels
Decreased velocity is an important predictor of poor neonatal outcome

Electrocardiography (ECG)

Fetal ECGs may be recorded as early as the 11th week of pregnancy
ECG is inaccurate before the 20th week
It is rarely used unless specific heart anomaly is suspected

Placental Grading

Placental grading is based on the amount of calcium deposits in the base of the placenta

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Description

This quiz covers the key concepts related to implantation in human development, including the role of the blastocyst, inner cell mass layers, and the formation of the umbilical cord. Additionally, it addresses implantation bleeding and the amniotic membrane. Test your understanding of these essential biological processes.