Fertilization and Amniotic Membranes

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Questions and Answers

What is the main difference between reproductive cloning and therapeutic cloning?

Reproductive cloning uses pluripotent cells, while therapeutic cloning uses multipotent cells.

Reproductive cloning is focused on organ regeneration, while therapeutic cloning is aimed at cloning entire organisms.

Reproductive cloning creates an identical infant, while therapeutic cloning allows for the growth of pluripotent stem cells. (correct)

Reproductive cloning involves egg fertilization, while therapeutic cloning does not.

Which primary germ layer arises from the yolk sac?

Ectoderm

Neuroderm

Entoderm (correct)

Mesoderm

What congenital defects are associated with the entoderm germ layer?

Heart and kidney defects

Nervous system disorders

Limb malformations

Esophageal and tracheal fistula (correct)

Which of the following is a correct implication related to the primary germ layers?

Each primary germ layer contributes to specific body systems, and defects often arise from the same layer. Signup and view all the answers

Why is rubella infection serious during pregnancy?

It may lead to congenital anomalies in all three primary germ layers. Signup and view all the answers

During which stage does the developing entity transition from being called a zygote to an embryo?

From fertilization to implantation Signup and view all the answers

What is the maximum lifespan of an ovum after being released for fertilization?

24 hours Signup and view all the answers

What role does the corona radiata play in relation to the ovum?

It acts as a protective layer around the ovum. Signup and view all the answers

What physical action helps propel the sperm through the female reproductive tract?

Peristaltic action of the fallopian tubes Signup and view all the answers

What is the critical time span for successful fertilization?

48 hours before and 24 hours after ovulation Signup and view all the answers

What is the typical amount of sperm per ejaculation?

2.5 ml Signup and view all the answers

Which structure increases the bulk of the ovum and protects it from injury?

Zona Pellucida Signup and view all the answers

In how much time can sperm generally reach the outer fallopian tube after ejaculation?

5 minutes Signup and view all the answers

What primary role does the smooth chorion play once it is formed?

It supports the sac containing amniotic fluid Signup and view all the answers

Which statement is true regarding the amniotic fluid's absorption?

Fetal swallowing is the major method of absorption Signup and view all the answers

What condition is indicated by a significant increase in amniotic fluid volume?

Hydramnios Signup and view all the answers

How does the amniotic fluid protect the fetus?

It shields against physical pressure and temperature changes Signup and view all the answers

What initiates uterine contractions before labor?

Prostaglandins produced by the amnion Signup and view all the answers

What is a common cause of oligohydramnios?

Fetal kidney dysfunction Signup and view all the answers

What is the typical pH level of amniotic fluid?

7.2 Signup and view all the answers

Which statement about the amnion is incorrect?

It has a nerve supply Signup and view all the answers

What is the primary function of the umbilical cord?

To transport oxygen and nutrients from the placenta to the fetus Signup and view all the answers

Which characteristic describes the structure of the umbilical cord?

It is about 53 cm in length at term Signup and view all the answers

What does the presence of Wharton’s jelly in the umbilical cord do?

It provides body structure and prevents pressure on blood vessels Signup and view all the answers

Which statement about the umbilical arteries is true?

They help in hemostasis after birth through muscle constriction Signup and view all the answers

What percentage of births present a nuchal cord condition?

20% Signup and view all the answers

Which type of stem cells occurs during the first 4 days of life?

Totipotent stem cells Signup and view all the answers

At what stage does a zygote begin to show differentiation and become an embryo?

After 4 days of life Signup and view all the answers

Which characteristic does NOT describe the umbilical cord?

It is primarily solid and lacks any fluid Signup and view all the answers

At what week can a baby start to grasp objects placed in its hand?

Week 11 Signup and view all the answers

What significant development occurs by the end of the fourth month?

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

Which of the following abilities does a baby have by week 12 of development?

Experiencing pain Signup and view all the answers

What marks the onset of kidney secretion during fetal development?

Week 12 Signup and view all the answers

At which week can the baby's heartbeat be audibly detected using a Doppler?

Week 12 Signup and view all the answers

What emerges by week 20 during fetal development?

Recognition of the mother’s voice Signup and view all the answers

By what gestational week can a fetus potentially be saved if born prematurely?

Week 24 Signup and view all the answers

During which week does the baby begin to have REM sleep?

Week 17 Signup and view all the answers

Study Notes

Fertilization

The union of an ovum and a spermatozoon occurs in the outer third of a fallopian tube (ampullar portion)
Fertilization must occur within 24 hours of ovulation, otherwise the ovum atrophies
The critical time span for successful fertilization is about 72 hours
Ovum is protected by the Zona Pellucida and Corona radiata
The ovum is propelled into the fallopian tube by the fimbriae
Normal amount of semen per ejaculation is 2.5 ml, containing 50-200 million sperm per ml (average 400 million per ejaculation)
Sperms can fertilize for 3-4 days after ejaculation
Normal life span of sperm is 7 days
Sperms reach the cervix within 90 seconds after ejaculation and the fallopian tube within 5 minutes
Spermatozoa move by flagella (tails) and uterine contractions

Amniotic Membranes

Chorionic villi on the medial surface of the trophoblast thin, leaving the surface smooth (smooth chorion)
Smooth chorion becomes the chorionic membrane - the outermost fetal membrane
Amnion forms beneath the chorion and covers the fetal surface of the placenta
Amniotic membrane lacks nerve supply and ruptures spontaneously at term
Amniotic fluid is constantly being renewed and is slightly alkaline (pH 7.2)
Amniotic fluid is absorbed by the fetus and through the fetal intestine
Amount at term - 800-1,200 ml
Hydramnios - excessive amniotic fluid (more than 2,000 ml), commonly due to esophageal atresia, anencephaly, or diabetes
Oligohydramnios - reduction in amniotic fluid (less than 300 ml), due to disturbances in fetal kidney function

Functions of Amniotic Fluid

Protection for the fetus
Shields against pressure or blows to the mother's abdomen
Regulates temperature
Aids in muscular development
Protects the umbilical cord from pressure

Umbilical Cord

Formed from the fetal membranes (amnion and chorion)
Provides circulatory pathway connecting the embryo to the chorionic villi of the placenta
Transports oxygen and nutrients from the placenta to the fetus
About 53 cm (21 in) in length at term
2 cm ( ¾ in ) thick
Consists of gelatinous mucopolysaccharide "Wharton's jelly" for support
Outer surface covered with the amniotic membrane
Contains one vein (carrying blood from the placenta to the fetus) and two arteries (carrying blood from the fetus to the placenta)
Number of veins and arteries is assessed at birth
Blood can be withdrawn from the umbilical vein or transfused during intrauterine life for assessments or treatment
Rate of blood flow is 350 ml/min at term
Cord is unlikely to twist or knot due to rapid blood flow
Nuchal cord (loop found around the fetal neck) is present in 20% of births
Wall of umbilical cord arteries have smooth muscle for hemostasis
Lacks nerve supply

Stem Cells

Totipotent stem cells (zygote cells) present during the first 4 days of life, can form a complete human being
Pluripotent stem cells present after 4 days of implantation, have the potential to become specific body cells
Multipotent stem cells are specific and have a set path to become a particular body organ

Types of Cloning

Reproductive cloning: nucleus of an adult cell is transferred into an oocyte, creating an embryo identical to the donor
Therapeutic cloning: pluripotent stem cells are removed to grow in a laboratory, potentially supplying any body cell needed by the donor

Zygote Development

Growth proceeds in a cephalocaudal direction

Primary Germ Layers

Ectoderm: arises from the amniotic cavity, the largest
Entoderm: arises from the yolk sac, a smaller cavity. Provides nourishment after implantation and produces red blood cells until the embryo's system matures.
Mesoderm: the third layer
Each germ layer develops into specific body systems
Coexisting congenital defects usually arise from the same germ layer

Fetal Development Week-by-Week

Week 9-10: Teeth begin to form, fingernails develop, baby can turn head and frown
Week 10 - 11: Baby can breathe amniotic fluid and urinate
Week 11: Baby can grasp objects, all organ systems function, has a skeletal structure, nerves, and circulation.
Week 12: (First Trimester) all body parts needed for experiencing pain are developed, vocal cords are complete, baby can suck thumb
Week 14: Heart pumps several quarts of blood daily
Week 15: Baby has adult taste buds
Month 4: Bone marrow development begins, heart pumps 25 quarts of blood daily, baby is 8-10 inches long and weighs half a pound
Week 17: Baby can have dream-like sleep
Week 19: Babies can be saved after 21-22 weeks, and sometimes earlier.
Week 20: Earliest stage for Partial Birth Abortion, baby recognizes mother's voice
Week 24: (Second Trimester End) Baby practices breathing by inhaling amniotic fluid. Most mothers feel increased fetal movement
Month 7-9: Eyeteeth present, baby opens and closes eyes, baby can distinguish between waking and sleeping
Month 9: Baby uses four senses (vision, hearing, taste, touch)

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Description

This quiz covers the critical processes of fertilization, including the journey of the sperm and ovum, as well as the formation of amniotic membranes. Learn about the timelines, protective structures, and physiological changes that occur during these stages. Test your knowledge on these essential aspects of human reproduction.