BGDA Practical 12 - Third Trimester: Difference between revisions

From Embryology
 
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=== Third Trimester ===
=== Third Trimester ===
(Clinical Week 28)  
(Clinical Week 28) [[Third Trimester]]




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| Clinical third trimester
| Clinical third trimester
| [[File:Fetal_size_change.jpg|90px|link=Fetal Development]] [http://embryology.med.unsw.edu.au/Notes/Ear.htm Sense - Hearing] 3rd Trimester - vibration acoustically of maternal abdominal wall induces startle respone in fetus.
| [[File:Fetal_size_change.jpg|90px|link=Fetal Development]] [[Sensory_-_Hearing_and_Balance_Development|Hearing]] 3rd Trimester - vibration acoustically of maternal abdominal wall induces startle respone in fetus.


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| [http://embryology.med.unsw.edu.au/Notes/respire.htm Respire] Month 7 - respiratory bronchioles proliferate and end in alveolar ducts and sacs  
| [[Respiratory_System_Development|Respire]] Month 7 - respiratory bronchioles proliferate and end in alveolar ducts and sacs  


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[http://embryology.med.unsw.edu.au/Notes/genital.htm Genital] male gonad (testes) descending  
[[Genital_System_Development|Genital]] male gonad (testes) descending  


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| <center>32</center>
| <center>32</center>
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| [[Integumentary_System_-_Nail_Development|Nail Development]] fingernails reach digit tip


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| <center>33</center>
| <center>33</center>
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| [http://embryology.med.unsw.edu.au/Notes/neuron.htm Neural]  brain cortical sulcation - primary sulci present [http://www.ncbi.nlm.nih.gov/pubmed/11158907 PMID:11158907]
| [[Neural System Development|Neural]]  brain cortical sulcation - primary sulci present<ref name="PMID11158907"><pubmed>11158907</pubmed></ref>


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| <center>34</center>
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| &nbsp;
| [http://embryology.med.unsw.edu.au/Notes/neuron.htm Neural]  brain cortical sulcation - insular, cingular, and occipital secondary sulci present [http://www.ncbi.nlm.nih.gov/pubmed/11158907 PMID:11158907]
| [[Neural System Development|Neural]]  brain cortical sulcation - insular, cingular, and occipital secondary sulci present<ref name="PMID11158907" />


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| <center>36</center>
| <center>36</center>
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|  [[File:Frazer006_bw600.jpg|90px|link=Fetal Development]]
|  [[File:Frazer006_bw600.jpg|90px|link=Fetal Development]] [[Integumentary_System_-_Nail_Development|Nail Development]] toenails reach digit tip
 
[[Vision_-_Lens_Development|Lens Development]] - lens growth and interocular distance plateaus after 36 weeks of gestation<ref name ="PMID19541779"><pubmed>19541779</pubmed></ref>


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| [[File:Newborn.jpg|90px|link=Birth]] Clinical Week 40  
| [[File:Newborn.jpg|90px|link=Birth]] Clinical Week 40  


[http://embryology.med.unsw.edu.au/Notes/heart.htm Heart ] pressure difference closes foramen ovale leaving a fossa ovalis  
[[Cardiovascular System Development|Heart]] pressure difference closes foramen ovale leaving a fossa ovalis  


[http://embryology.med.unsw.edu.au/Notes/endocrine8.htm Thyroid ] TSH levels increase, thyroxine (T3) and T4 levels increase to 24 h, then 5-7 days postnatal decline to normal levels  
[[Endocrine_-_Thyroid_Development|Thyroid]] TSH levels increase, thyroxine (T3) and T4 levels increase to 24 h, then 5-7 days postnatal decline to normal levels  


[http://embryology.med.unsw.edu.au/Notes/endocrine9.htm Adrenal] - zona glomerulosa, zona fasiculata present  
[[Endocrine_-_Adrenal_Development|Adrenal]] - zona glomerulosa, zona fasiculata present  




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Revision as of 22:59, 22 May 2011

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Practical 12: Embryo to Fetus | Second Trimester | Third Trimester | Birth | Neonatal | Abnormalities



Introduction

Historic drawing of the fetus in the uterus at 8 months compared to non-pregnant uterus size.
  • Fetal Neural
  • Fetal Respiratory
  • Fetal Cardiovascular
  • survival issues for early delivery
  • fetal weight
  • fetal origins hypothesis

Week 24+

  • Earliest potential survival expected if born
  • Respiratory Week 24 to 40 lung histology - terminal sac, end month 6 alveolar cells type 2 appear and begin to secrete surfactant
    • saccule - a large thin-walled airspace lined by flattened epithelium present from about 28 weeks gestation to 2 months after birth
  • Gonad - male gonad (testes) descending (week 30) Development Animation - Testis Descent
    • 10 to 23 weeks - (9.45%) had migrated from the abdomen and were situated in the inguinal canal
    • 24 to 26 weeks - (57.9%) had migrated from the abdomen
    • 27 to 29 weeks - (16.7%) had not descended to the scrotum
Testis 001 icon.jpg Testis Descent Failure of descent (cryptorchidism) either unilateral or bilateral testicular descent, occurring in up to 30% premature and 3-4% term males.


References: Sampaio FJ, Favorito LA. Analysis of testicular migration during the fetal period in humans. J Urol. 1998 Feb;159(2):540-2. | Malas MA, Sulak O, Ozturk A. The growth of the testes during the fetal period. BJU Int. 1999 Oct;84(6):689-92.

Fetal Weight

Fetal weight change.jpg

Fetal Birth

Most of the serious illness and mortality is concentrated in the 1 to 2 percent of infants who are born at less than 32 weeks of gestation (week 30) and who weigh less than 1500 g.


Teratogens - Infant Drug Clearance

Drug clearance rates

Teratogen (Greek, teraton = monster) Any agent that causes a structural abnormality following exposure during pregnancy. The overall effect depends on dosage and time of exposure.

The drug clearance data below are only approximate calculated rates for the fetus and infant from NZ Drug Safety in Lactation

Post-conceptual Age (weeks) Clearance of Drug (percentage of adults)
24-28 5%
28-34 10%
34-40 33%
40-44 50%
44-68 66%
> 68 100%


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Practical 12: Embryo to Fetus | Second Trimester | Third Trimester | Birth | Neonatal | Abnormalities

Additional Information

The following information is a detailed timeline of third trimester development and content does not form part of the current practical class.

Third Trimester

(Clinical Week 28) Third Trimester


Week
Stage
 Event
Clinical third trimester Fetal size change.jpg Hearing 3rd Trimester - vibration acoustically of maternal abdominal wall induces startle respone in fetus.
27
  
28
   Respire Month 7 - respiratory bronchioles proliferate and end in alveolar ducts and sacs
29
  
30
    

Genital male gonad (testes) descending

31
  
32
   Nail Development fingernails reach digit tip
33
   Neural brain cortical sulcation - primary sulci present[1]
34
   Neural brain cortical sulcation - insular, cingular, and occipital secondary sulci present[1]
35
    
36
   Frazer006 bw600.jpg Nail Development toenails reach digit tip

Lens Development - lens growth and interocular distance plateaus after 36 weeks of gestation[2]

37
    
38
 Birth Newborn.jpg Clinical Week 40

Heart pressure difference closes foramen ovale leaving a fossa ovalis

Thyroid TSH levels increase, thyroxine (T3) and T4 levels increase to 24 h, then 5-7 days postnatal decline to normal levels

Adrenal - zona glomerulosa, zona fasiculata present





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Cite this page: Hill, M.A. (2024, June 8) Embryology BGDA Practical 12 - Third Trimester. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/BGDA_Practical_12_-_Third_Trimester

What Links Here?
© Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G
  1. ↑ 1.0 1.1 <pubmed>11158907</pubmed>
  2. ↑ <pubmed>19541779</pubmed>
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