Human Development Chapter 6

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Questions and Answers

At what point does maternal Immunoglobulin G (IgG) begin to be transported from mother to fetus?

14 weeks (correct)

10 weeks

12 weeks

8 weeks

What developmental structure gives rise to the primitive umbilical cord?

Amnion and connecting stalks (correct)

Yolk sac stalk

Chorionic plate

Intestinal loops

What causes the physiological umbilical hernia during fetal development?

Enlargement of the amniotic cavity

Rapid growth of intestinal loops (correct)

Failure of the abdominal cavity to grow

Increased pressure from the yolk sac

What structure occupies the space between the amnion and the chorionic plate?

Yolk sac proper Signup and view all the answers

What characteristic feature of umbilical arteries aids in their rapid constriction after the cord is tied off?

Presence of many elastic fibers Signup and view all the answers

What is a common change in the villi at the end of pregnancy?

Increase in fibrous tissue in the core of the villus Signup and view all the answers

What characteristic of the fetus is observed at the beginning of the sixth month?

Skin appears reddish and wrinkled due to lack of connective tissue. Signup and view all the answers

Which change can lead to the appearance of a whitish cotyledon?

Excessive fibrinoid formation causing infarction Signup and view all the answers

At 37 weeks, how much amniotic fluid is typically present?

800 - 1,000 mL Signup and view all the answers

At what length is the CRL approximately at 6 to 7 months of pregnancy?

Approximately 25 cm. Signup and view all the answers

What is the primary reason a fetus born early in the sixth month struggles to survive?

Lack of developed respiratory and nervous system coordination. Signup and view all the answers

What primarily contributes to the production of amniotic fluid?

Maternal blood Signup and view all the answers

What structural change occurs in the basement membranes of fetal capillaries towards the end of pregnancy?

Thickening of basement membranes Signup and view all the answers

What significant change occurs in the last two months of pregnancy regarding the fetus's appearance?

The fetus gains well-rounded contours from subcutaneous fat deposition. Signup and view all the answers

How long is the length of pregnancy calculated from the last normal menstrual period (LNMP)?

280 days. Signup and view all the answers

What is Vernix caseosa and when does it appear on the fetus?

A fatty substance found on the skin by the end of intrauterine life. Signup and view all the answers

What is the approximate weight of the fetus at 6 to 7 months of pregnancy?

Around 1,100 grams. Signup and view all the answers

What structural change occurs in the trophoblast during the sixth month?

Formation of more secondary and tertiary villi. Signup and view all the answers

What is the primary method by which the fetus exchanges gases with the maternal circulation?

Simple diffusion across the fetal membrane Signup and view all the answers

How much oxygen does the fetus typically extract from the maternal circulation per minute at term?

20 to 30 ml Signup and view all the answers

Which structure is NOT mentioned as passing through the primitive umbilical ring at the 5th week of development?

Amniotic membrane Signup and view all the answers

What is critical to ensuring an adequate oxygen supply to the fetus?

Placental blood flow Signup and view all the answers

Which category of substances is NOT listed as rapidly exchanged between the mother and fetus?

Proteins Signup and view all the answers

What is the first stage of labor?

Effacement and Dilation of the Cervix Signup and view all the answers

What does Small for Gestational Age (SGA) indicate?

Below 10th percentile for their gestational age Signup and view all the answers

Which of the following is a risk associated with SGA infants?

Perinatal asphyxia Signup and view all the answers

What physiological change occurs in the myometrium during the last weeks of gestation?

Thickening of the myometrium in the upper region Signup and view all the answers

Which factor is considered a major growth promoter during development?

Insulin-like growth factor-1 (IGF-1) Signup and view all the answers

Which complication is not directly related to SGA infants?

Normal development milestones Signup and view all the answers

What is the typical interval for the onset of contractions during labor?

10 minutes apart Signup and view all the answers

What distinguishes symmetric growth restriction from asymmetric growth restriction in SGA infants?

Symmetric growth restriction affects all parts of the body equally Signup and view all the answers

Study Notes

Fetal Development Stages

Maturation of tissues and organs occurs, with rapid body growth by the sixth month.
Fetal skin appears reddish and wrinkled due to insufficient underlying connective tissue.
Fetuses born at the early sixth month face significant survival challenges.
Crown-rump length (CRL) and crown-heel length (CHL) are crucial measurements of fetal size.

Pregnancy Timeline

Pregnancy lasts approximately 280 days (40 weeks) from the last normal menstrual period (LNMP).
More accurately, it is about 266 days (38 weeks) after fertilization.

Fetal and Maternal Interactions

By six to seven months, CRL reaches around 25 cm, and weight is approximately 1,100g, with a 90% survival chance for infants born at this stage.
Trophoblast development includes numerous secondary and tertiary villi, giving a radial appearance.
Blood flow through the placenta is critical for oxygen uptake; the fetus extracts 20 to 30 ml of oxygen per minute.

Exchange Mechanisms

Gases, nutrients, and electrolytes are exchanged rapidly, increasing as pregnancy progresses.
Key nutrients include amino acids, free fatty acids, carbohydrates, and vitamins.
Maternal antibodies, particularly IgG, begin transferring to the fetus around 14 weeks.

Umbilical Structures

The primitive umbilical ring is formed at about five weeks, containing the connecting stalk and yolk stalk.
The connecting stalk houses the allantois and umbilical vessels (two arteries and one vein).

Amniotic Fluid Dynamics

Amniotic fluid volume increases significantly throughout pregnancy, from approximately 30 mL at 10 weeks to between 800 – 1,000 mL by 37 weeks.

Changes in Pregnancy

Structural changes occur in the placenta toward the end of pregnancy, including increased fibrous tissue and thickening of membranes.
Excessive fibrinoid formation can lead to placental infarction, impacting fetal health.

Parturition Process

Parturition, or childbirth, involves tissue changes during the final weeks of gestation, including myometrial thickening and cervical softening.
The process of labor includes three stages: effacement and dilation, delivery of the fetus, and delivery of the placenta.

Small for Gestational Age (SGA)

SGA is defined as being below the 10th percentile for gestational age; may be pathologically small or constitutionally small.
SGA infants face risks such as perinatal asphyxia and hypoglycemia.

Insulin-like Growth Factor-1 (IGF-1)

IGF-1 is essential for growth during fetal development due to its mitogenic and anabolic effects.

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Explore the physical changes and growth that occur during the sixth month of fetal development. Delve into the appearance of the fetus, including skin characteristics and the challenges faced by early births. This quiz enhances your understanding of human maturation processes.