Fetal Development Week by Week Overview
Summary
TLDRThe 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
- š The embryonic stage starts at day 15 post-conception and lasts until week 8, marking the initial development of major body structures.
- š§ By week three, the brain, spinal cord, and heart begin to form, with the neural tube emerging as the precursor to the spinal cord.
- š In week four, the brain starts to differentiate, and limb buds grow, with the heart beginning to beat rhythmically by week five.
- š« 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.
- š¶ 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.
- š In week eight, the intestines rotate, and the embryo's facial features further develop, with the heart's development nearing completion.
- š¦· From weeks 9 to 12, sexual differentiation continues, and the digestive system shows activity, with the head constituting nearly half the fetus's size.
- š¶š» By week 12, the fetus's limbs are long and thin, digits are well-formed, and fetal gender can be determined via ultrasound.
- š Between weeks 13 and 16, lanugo hair develops, and the fetus makes active movements, swallowing amniotic fluid, with external genitalia becoming recognizable.
- š§ 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.
- šļøāšØļø 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.
Outlines
š¶ Embryonic Development Overview
The embryonic stage, commencing at day 15 post-conception and extending to week 8, is a critical period for the formation of the body's major organs and external features. By week three, the brain, spinal cord, heart, and gastrointestinal tract start developing. The neural tube, precursor to the spinal cord, also forms. Limb buds emerge and grow, and by week four, the brain's differentiation advances alongside limb development. Week five marks the onset of the heart's regular rhythm, with initial eye and ear structures becoming apparent. The brain continues to develop in week six, with the lungs beginning to form and fetal circulation being established. The liver starts producing red blood cells, and brain waves become detectable. In week seven, the body straightens, and features like nipples, hair follicles, elbows, and toes form. The fetus begins to move more, and the diaphragm develops. Tooth buds and facial features become visible. Week eight sees the intestines rotating and further facial development, with the heart's completion and the embryo starting to resemble a human. The subsequent weeks through 12 are marked by sexual differentiation, development of teeth buds, and maturation of the digestive and urogenital systems. The fetus's head constitutes nearly half its size, and by week 12, gender determination via ultrasound is possible, revealing long limbs and well-formed digits. From weeks 13-16, lanugo hair develops, and bones harden as the skin remains transparent. The fetus becomes more active, swallowing amniotic fluid, and external genitalia become recognizable. Fingernails and toenails form, and the fetus's weight increases significantly. Fetal movements, or 'quickening,' are typically felt by the mother during this phase. Weeks 17-20 are characterized by rapid brain growth, audible fetal heart tones, and the kidneys' active secretion of urine. The fetus is covered in vernix caseosa, and eyebrows and head hair may appear. Muscles are well developed, and nails are present on fingers and toes. During weeks 21-24, eyebrows and eyelashes are fully formed, and the fetus exhibits a hand grasp and startle reflex. Alveoli start forming in the lungs, and the skin remains translucent. The fetus's eyelids are sealed, but surfactant production begins. By weeks 25-28, the fetus reaches approximately 15 inches in length, with significant brain development and functional nervous system control. Fingerprints are established, and subcutaneous fat becomes visible. Blood formation shifts from the spleen to bone marrow, and the fetus usually adopts a head-down position. From weeks 29 to 32, body fat increases rapidly, and the central nervous system's control over body functions strengthens. Rhythmic breathing is established, though the lungs are not yet fully mature. The fetus stores iron, calcium, and phosphorus. In weeks 33-38, the male fetus's testes descend into the scrotum, and lanugo begins to disappear. The fetus's hand grasp reflex is strong, and body fat continues to increase. Earlobes form and firm up, and fingernails reach the fingertips, with small breast buds present in both sexes. The mother provides the fetus with antibodies for disease protection, and by 38 weeks, the fetus is considered full-term, filling the entire uterine space.
š¤° Maternal and Fetal Development at Term
The final paragraph discusses the maternal supply of antibodies to the fetus, which is crucial for disease protection. It emphasizes that by 38 weeks, the fetus is considered full-term, having filled all available space within the uterus. This stage signifies the completion of the fetal development process, with the fetus being fully prepared for birth and life outside the womb.
Mindmap
Keywords
š”Embryonic stage
š”Neural tube
š”Limb buds
š”Brain differentiation
š”Fetal circulation
š”Red blood cells
š”Sexual differentiation
š”Lanugo
š”Quickening
š”Vernix caseosa
š”Fetal reflexes
š”Surfactant
Highlights
The embryonic stage begins at day 15 after conception and lasts through week 8.
By week 3, the brain, spinal cord, heart, and gastrointestinal tract begin to develop.
During week 4, limb buds grow, and the brain starts differentiating.
In week 5, the heart begins a regular rhythm, and early structures of the eyes and ears are noticeable.
Week 6 marks the formation of the lungs, and fetal circulation is established.
Brain waves are detectable, and the primitive skeleton forms in week 6.
By week 7, the embryo shows a straightening of the trunk, and arm and leg movements become more frequent.
In week 8, the embryo starts to resemble a human, and heart development is complete.
By week 12, sexual differentiation continues, and the face and neck are well formed.
In weeks 13-16, the fetus's bones harden, and lanugo (fine hair) develops.
Fetal movement (quickening) is often detected by the mother during weeks 13-16.
During weeks 17-20, the fetus experiences rapid brain growth, and fetal heart tones can be heard with a stethoscope.
Weeks 21-24 see the development of the hand grasp and startle reflex, and alveoli begin forming in the lungs.
In weeks 25-28, the brain undergoes rapid development, and the fetus's nervous system begins controlling some functions.
By week 38, the fetus is considered full-term, filling all available space in the uterus.
Transcripts
The embryonic stage of development begins at dayĀ 15 after conception and continues through week 8.Ā Ā
Basic structures of all major body organs and theĀ main external features are completed during thisĀ Ā
time period, including internal organs. By weekĀ three the brain spinal cord and heart begin toĀ Ā
develop along with the gastrointestinal tract.Ā Here, the neural tube forms which later becomesĀ Ā
the spinal cord. Also, leg and arm buds begin toĀ appear and grow out from the small body. In weekĀ Ā
four the brain begins to differentiate and theĀ limb buds grow and develop more. In week five,Ā Ā
the heart now begins to beat a regular rhythm.Ā Beginning structures of the eyes and ears areĀ Ā
noticeable. Some cranial nerves are now visibleĀ and muscles connect to nerves. In week six,Ā Ā
the formation of the lungs beginsĀ and fetal circulation is established.Ā Ā
The liver begins producing red blood cells andĀ the brain develops further. Here, the primitiveĀ Ā
skeleton forms and the central nervous systemĀ is now detectable with brain waves. In week 7,Ā Ā
we see a straightening of the trunk. Nipples andĀ hair follicles form, along with elbows and toes.Ā Ā
Arms and legs begin to move more frequentlyĀ and the diaphragm is formed. The mouth andĀ Ā
lips become visible along with early tooth buds.Ā In week 8, there is a rotation of the intestinesĀ Ā
and facial features continue to develop. TheĀ heart development is now complete and the embryoĀ Ā
begins to resemble a human being. In weeksĀ through 12, sexual differentiation continues.Ā Ā
Buds for all 20 temporary teeth are now laid downĀ and the digestive system shows activity. In thisĀ Ā
stage, the head makes up nearly half the size ofĀ the fetus. The face and neck are well formed andĀ Ā
the urogenital tract completes its development.Ā Red blood cells are produced in the liver andĀ Ā
urine begins to be produced and excreted. TheĀ fetal gender can be determined by week 12 usingĀ Ā
an ultrasound, which will also reveal limbs thatĀ are long and thin and digits that are well-formed.Ā Ā
In weeks 13-16, a fine hair called lanugo developsĀ on the head. The fetal skin is almost transparentĀ Ā
as bones become harder. The fetus makes activeĀ movements and sucking motions are made with theĀ Ā
mouth. The fetus swallows amniotic fluid andĀ external genitalia are recognizable at thisĀ Ā
stage. Fingernails and toenails are alsoĀ present as the fetus's weight quadruples.Ā Ā
It is usually during this phase thatĀ fetal movement, also known as quickening,Ā Ā
is detected by the mother. Weeks 17-20 show aĀ rapid brain growth with fetal heart tones thatĀ Ā
can be heard with a stethoscope. The kidneys willĀ continue to secrete urine into the amniotic fluid.Ā Ā
The vernix caseosa, which is a white greasy film,Ā now covers the fetus. The eyebrows and head hairĀ Ā
may appear and brown fat is deposited to helpĀ maintain the fetus's temperature. Muscles areĀ Ā
well developed and nails are present onĀ both fingers and toes. During weeks 21-24,Ā Ā
eyebrows and eyelashes are well-formed. TheĀ fetus has a hand grasp and startle reflex.Ā Ā
Alveoli begin forming in the lungs and skinĀ remains translucent and red. The eyelidsĀ Ā
still remain sealed and the lungs begin to produceĀ surfactant. During weeks 25-28, the fetus reachesĀ Ā
a length of about 15 inches. There is a rapidĀ development of the brain and eyelids are able toĀ Ā
open and close. The nervous system is now ableĀ to control some of the functions of the fetus.Ā Ā
Fingerprints are also set. Subcutaneous fat isĀ now visible under the skin. Blood formation shiftsĀ Ā
from the spleen to bone marrow and the fetusĀ usually assumes a head down position. In weeksĀ Ā
29 to 32, there is a rapid increase in the amountĀ of body fat. There is an increased central nervousĀ Ā
system control over body functions and rhythmicĀ breathing is now established. However, the lungsĀ Ā
are not fully mature. Pupillary light reflex isĀ now present and the fetus stores iron, calcium,Ā Ā
and phosphorus. During weeks 33-38, the testesĀ are in the scrotum of the male fetus. LanugoĀ Ā
begins to disappear. The fetus has a good strongĀ hand grasp reflex and increases in body fat.Ā Ā
Earlobes are formed and firm. Fingernails reachĀ the end of the fingertips and small breast budsĀ Ā
are present on both sexes. The mother supplies theĀ fetus with antibodies against disease. The fetusĀ Ā
is considered full-term at 38 weeks, when theĀ fetus fills all the available space in the uterus.
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