Foundations Lecture - Introduction to Human Development
|Embryology - 5 Apr 2020 Expand to Translate|
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- 1 Introduction
- 2 Embryology Education Support
- 3 Human Reproductive Cycle
- 4 First Trimester
- 5 Second and Third Trimester
- 6 Postnatal Development
- 7 Abnormal Development
- 8 Additional Information
- 9 Glossary Links
Human development is one of the most exciting topics to study not only as a medical student, but also for our fundamental understanding of the human body. Of all health issues in Medicine, fertility and reproduction is a topic that will affect everyone. This lecture is going to take you briefly through key biological concepts in human development, these will later be explored in more detail through the BGD course. I will be using simplified terms in the lecture slides (with developmental term in brackets).
- Australian Statistics On 2 January 2017, the resident population of Australia is projected to be 24,317,037 (2016 - 24,001,781).
The lecture will be followed by a practical class introducing online resources for independent study and working through similar embryology concepts.
|Other Foundations links|
Four Basic Tissue Types
In histology you have heard that tissues and organs of the body consist of combinations of 4 basic tissue organisations:
- Where do they come from?
- How do they develop?
- What are their relationships with each other?
Human Development Timeline
|Last Menstrual Period (LMP) first day was today -> Birth Date - January 18, 2018|
|Gestation Calculation (based upon a normal 28 day cycle)
Embryology Education Support
UNSW Embryology Online
Using these resources (online navigation, organization and printing) will be covered in the introduction to the associated Practical class.
- A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | Numbers | Symbols
- There are many different excellent embryology textbooks
- I have included below embryology textbooks accessible online through the UNSW Library that cover the clinical topics as well.
- As an introduction try the chapter in The Developing Human - Introduction to the Developing Human
|The Developing Human: Clinically Oriented Embryology (10th edn)|
UNSW Students have online access to the current 10th edn. through the UNSW Library subscription (with student Zpass log-in).
|Ebook - Kyoto Collection (1st edn)|
|UNSW students can download this free iBook that describes embryos from the first 8 weeks of development showing whole embryos, histological features, movies and high resolution 3D scans. The iBook also contains a linked glossary with descriptions of embryology terminology, and related terms.
Note - Only available for the Apple iPhone, iPad and laptop and desktop computers. No PC version currently available.
Human Reproductive Cycle
- Meiosis in gonad produces haploid gametes
- testis the sperm (spermatozoa)
- ovary the egg (oocyte)
- there are several differences in when and how gametes are formed in the male and female gonad.
- Menstrual Cycle a regular cycle of reproduction (28 days)
- begins at puberty
- release of 1 egg (oocyte) every cycle
- Endocrine controlled (HPG axis)
- begins at puberty
- continuous production of sperm (spermatozoa, human male 2,000/second)
- release millions of spermatozoa (require activation, capacitation)
- Paired organs
- lying in the peritoneal cavity
- Divide the pregnancy into 3 "blocks" of about 3 months (trimesters)
- First Trimester - embryonic period (organogenesis)
- Second and Trimester - fetal period (growth)
- Embryonic Period - Week 1 to 8 (first trimester)
- Establish the basic structure of organs and tissues (Organogenesis)
- development and growth of the placenta (Placentation)
- the process of the 2 haploid gametes (egg and sperm) fusing and combining genetic material.
- conceptus - the entire product of fertilisation
- occurs freely floating in uterus
- occurs during week 1 following fertilization
- last menstrual period (LMP) week 3
- mitosis to form solid ball of cells (morula), then hollow ball (blastocyst)
- Implantation - initial attachment to uterine wall, and then invasion of the uterine wall.
- Uterine body
- posterior, anterior, superior, lateral (most common posterior)
- inferior implantation - placenta overlies internal os of uterus Placenta Previa
- Ectopic Sites
- external surface of uterus, ovary, bowel, gastrointestinal tract, mesentery, peritoneal wall
- If not spontaneous then, embryo has to be removed surgically
- Uterine - tubal pregnancy (most common ectopic)
- Clinically can be detected following implantation (week 2)
- Last Menstrual Period (LMP) - today ? ....... Birth Date - January 30, 2014
|Pregnancy test (maternal urine)||Ovary - corpus luteum secretes hormone (hCG) to support pregnancy|
- 4 Key processes commence
- the formation of the 3 layer embryo (trilaminar embryo)
- All tissues of the body are formed from these 3 embryonic tissue layers (germ layers)
- Ectoderm (epithelium) - forms the central and peripheral nervous system and epithelium of the skin
- Mesoderm (connective tissue) - forms the body connective tissues: blood, bone, muscle, connective tissue skin, gastrointestinal and respiratory tracts
- Endoderm (epithelium) - forms gastrointestinal tract organs and the epithelium of the gastrointestinal and respiratory tracts
- segmentation of the mesoderm into somites
- forms the axial body plan
- segmentation of the ectoderm
- separates the neural tissue from the skin (epidermis)
- folding of the whole embryonic disc
- all edges of the disc fold ventrally
- left and right of the disc come together to form a "tube" of the 3 layers
- top and bottom of the disc bend to form a "C" shaped embryo.
Week 5 to 8
- early development of the other organs, tissues and limbs
|Week 5||Week 8|
- Materno/fetal organ
- No exchange of blood
- Many different roles
- can be "sampled" as part of a prenatal diagnostic test
- interaction between implanting conceptus and uterine wall (endometrium)
- The uterine lining following implantation (Decidua)
- forms 3 distinct regions, at approx 3 weeks
- Decidua Basalis - implantation site
- Decidua Capsularis - enclosing the conceptus
- Decidua Parietalis - remainder of uterus
- uterine cavity is lost by 12 weeks
Second and Third Trimester
- Week 9 to 37 - Fetal Development
- Continuing growth and differentiation of organs formed in embryonic period
- some organs have a later development - neural, genital, respiratory, bones
- some continue to develop after birth - neural, genital, respiratory, bones
- growth in size, length (Second Trimester)
- growth in weight (Third Trimester)
- birth (parturition) is a complex physiological process between the fetus and mother
- thought to be initiated by the fetus
Maternal Birth Stages
- Lung function - Fluid drainage, Gas exchange, muscular activity
- Circulatory changes - Closure of 3 vascular shunts
- Thermoregulation - metabolic rate, fat metabolism
- Nutrition - gastrointestinal tract function, peristalsis
- Waste - kidney function
- Endocrine function - loss of placenta, maternal hormones
Critical Periods of Development
Three main causes:
- First trimester most critical
- Different effect depending on time of insult (teratogen)
- Prenatal diagnosis - number of different techniques (non-invasive, invasive) for determining normal development
- Neonatal diagnosis (APGAR test, Guthrie test)
- Maternal diagnosis - often pregnancy will expose maternal health problems
- Gutherie card icon.jpg
|Additional Information - Content shown under this heading is not part of the material covered in this class. It is provided for those students who would like to know about some concepts or current research in topics related to the current class page.|
- You don't need to know everything today, this is an introduction.
- Use the glossary to help understand new terms.
- Don't confuse "germ cell layers" (ectoderm, mesoderm, endoderm) with "germ cells" (egg, spermatazoa).
- Remember the difference between "clinical weeks" (last menstral period) and "embryonic weeks" (from ovulation/fertilisation, 2 weeks later).
- With abnormalities
- think about the types of prenatal dianostic techniques that are now available
- the 2 major types (genetic and environmental)
- the effect of maternal age/health/lifestyle.
|Hill, M.A. (2019). UNSW Embryology (19th ed.) Retrieved April 5, 2020, from https://embryology.med.unsw.edu.au|
|Citation: Moore, K.L., Persaud, T.V.N. & Torchia, M.G. (2015). The developing human: clinically oriented embryology (10th ed.). Philadelphia: Saunders.
UNSW Students have online access to the current 10th edn. through the UNSW Library subscription.
Chapter 1 - Introduction to the Developing Human
|Schoenwolf, G.C., Bleyl, S.B., Brauer, P.R., Francis-West, P.H. & Philippa H. (2015). Larsen's human embryology (5th ed.). New York; Edinburgh: Churchill Livingstone.
UNSW students have full access to this textbook edition through UNSW Library subscription (with student Zpass log-in).
Read the introduction before Chapter 1.
- Glossary: A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | Numbers | Symbols | Term Link
Cite this page: Hill, M.A. (2020, April 5) Embryology Foundations Lecture - Introduction to Human Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Foundations_Lecture_-_Introduction_to_Human_Development
- © Dr Mark Hill 2020, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G