Fetal Development Week by Week Overview

Summary

The script outlines the critical stages of human embryonic development from conception through week 38. It details the formation of vital organs, the establishment of bodily systems, and the physical changes that occur as the embryo evolves into a fetus. Key milestones include the development of the brain and spinal cord, the initiation of a heartbeat, the emergence of limbs, and the maturation of the lungs. By week 12, sexual differentiation is apparent, and by week 20, the fetus shows active movements. The summary covers the progression of fetal growth, highlighting the transition from a tiny embryo to a fully formed, viable human being ready for birth at term.

Takeaways

• 🚀 The embryonic stage starts at day 15 post-conception and lasts until week 8, marking the initial development of major body structures.
• 🧠 By week three, the brain, spinal cord, and heart begin to form, with the neural tube emerging as the precursor to the spinal cord.
• 🔍 In week four, the brain starts to differentiate, and limb buds grow, with the heart beginning to beat rhythmically by week five.
• 🫁 Week six sees the commencement of lung formation and the establishment of fetal circulation, along with the liver's initiation of red blood cell production.
• 👶 By week seven, the trunk straightens, and features like nipples, hair follicles, elbows, and toes start to form, with arms and legs showing more movement.
• 🌀 In week eight, the intestines rotate, and the embryo's facial features further develop, with the heart's development nearing completion.
• 🦷 From weeks 9 to 12, sexual differentiation continues, and the digestive system shows activity, with the head constituting nearly half the fetus's size.
• 👶🏻 By week 12, the fetus's limbs are long and thin, digits are well-formed, and fetal gender can be determined via ultrasound.
• 👀 Between weeks 13 and 16, lanugo hair develops, and the fetus makes active movements, swallowing amniotic fluid, with external genitalia becoming recognizable.
• 🧠 Weeks 17 to 20 are marked by rapid brain growth, with fetal heart tones audible via stethoscope and the kidneys secreting urine into the amniotic fluid.
• 👁️‍🗨️ From weeks 21 to 24, the fetus develops a hand grasp and startle reflex, with alveoli beginning to form in the lungs and the production of surfactant commencing.

Q & A

At what stage does the embryonic development begin and how long does it last?

The embryonic stage of development begins at day 15 after conception and continues through week 8.

What are some of the key developments that occur during the embryonic stage?

During the embryonic stage, the basic structures of all major body organs and the main external features are completed, including the development of the brain, spinal cord, heart, gastrointestinal tract, and limb buds.

When does the heart begin to beat a regular rhythm during fetal development?

The heart begins to beat a regular rhythm in week five of fetal development.

What significant developments occur in the fetal brain during week six?

In week six, the formation of the lungs begins, fetal circulation is established, the liver starts producing red blood cells, and the brain develops further with the central nervous system becoming detectable with brain waves.

What changes are observed in the fetus during week seven of development?

In week seven, the trunk straightens, nipples and hair follicles form, elbows and toes develop, arms and legs move more frequently, and the diaphragm is formed.

How does the fetus's appearance change by the end of week eight?

By week eight, the intestines rotate, facial features continue to develop, heart development is complete, and the embryo begins to resemble a human being.

What are some of the developments that occur in the fetus between weeks 13 and 16?

During weeks 13-16, lanugo develops on the head, the skin becomes almost transparent as bones harden, the fetus makes active movements, and external genitalia become recognizable. Fingernails and toenails are also present as the fetus's weight quadruples.

When can fetal movement, or quickening, be detected by the mother?

Fetal movement, or quickening, is usually detected by the mother during the phase of weeks 13-16.

What are some of the key milestones in fetal development between weeks 21 and 24?

Between weeks 21 and 24, eyebrows and eyelashes are well-formed, the fetus has a hand grasp and startle reflex, alveoli begin forming in the lungs, and the lungs start to produce surfactant.

How does the fetus's brain and nervous system develop during weeks 25 to 28?

During weeks 25-28, there is rapid development of the brain, eyelids are able to open and close, the nervous system can control some of the fetus's functions, and fingerprints are set.

What are the notable developments in the fetus during weeks 29 to 32?

In weeks 29 to 32, there is a rapid increase in body fat, increased central nervous system control over body functions, rhythmic breathing is established, and the fetus stores iron, calcium, and phosphorus.

What are the final preparations for birth that the fetus undergoes between weeks 33 and 38?

Between weeks 33 and 38, the fetus's lanugo begins to disappear, body fat increases, earlobes form and become firm, fingernails reach the end of the fingertips, and small breast buds are present on both sexes. The fetus is also supplied with antibodies against disease by the mother.