Foundations Lecture - Introduction to Human Development
- 1 Introduction
- 2 Aims
- 3 Human Development Timeline
- 4 UNSW Embryology Online
- 5 Textbooks
- 6 Four Basic Tissue Types
- 7 Human Reproductive Cycle
- 8 Ovary
- 9 Ovulation
- 10 Fertilization
- 11 Early Development
- 12 Week 1 Development
- 13 Week 2 Development
- 14 Pregnancy
- 15 Implantation Sites
- 16 Placenta
- 17 Embryonic Development
- 18 Week 3
- 19 Week 4
- 20 Week 4-8
- 21 Week 9 - 38
- 22 Birth
- 23 Critical Periods of Development
- 24 Revision Notes
- 25 Textbooks
- 26 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).
This Lecture is under revision for 2013.
The lecture will be followed by a practical class introducing online resources for independent study and working through similar embryology concepts.
|Other Foundations links|
- Purpose of learning embryology
- Basic facts about early human development
- Appreciate differences between the conceptus, embryo and fetus
- General understanding of the term “critical periods” of development
Concepts: Fertilization, Early conceptus, Germ layers, Embryo, Tissue origins, Timetable/stages of development, Fetus, Placenta
Background Lectures: Cell Structure (structure and function), Cell Division (mitosis, meiosis, lifespan, cell death), 4 Basic Tissues (Epithelial, Connective, Muscular, Nervous)
Human Development Timeline
UNSW Embryology Online
|<mediaplayer width='360' height='410' image="http://php.med.unsw.edu.au/embryology/images/6/61/Human_development_001_icon.jpg">File:Human development 001.mp4</mediaplayer>||
|Movies||Original Website||New Website||Annotated movie|
Using these resources (online navigation, organization and printing) will be covered in the introduction to the associated Practical class.
- There are many different excellent embryology textbooks
- I have included 2 that cover the clinical topics as well. More Textbooks?
The Developing Human: Clinically oriented embryology
Citation: Keith L. Moore, T.V.N. Persaud, Mark G. Torchia. (2011). The Developing Human: clinically oriented embryology (9th ed.). Philadelphia: Saunders.
The following chapter links only work with a UNSW connection.
Larsen's human embryology
Citation: Larsen's human embryology 4th ed. Schoenwolf, Gary C; Larsen, William J, (William James). Philadelphia, PA : Elsevier/Churchill Livingstone, c2009.
The following chapter links only work with a UNSW connection.
- Links: More Embryology Textbooks
Four Basic Tissue Types
Tissues and organs of the body consist of combinations of 4 basic tissue organisations:
- Where do they come from?
- How do they develop?
Human Reproductive Cycle
- Meiosis in gonad produces haploid gametes (egg and sperm)
- 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
- the process of the 2 haploid gametes (egg and sperm) fusing and combining genetic material.
- conceptus - the entire product of fertilization
- occurs during week 1 following fertilization
- last menstrual period (LMP) week 3
- mitosis to form solid ball of cells (morula), then hollow ball (blastocyst)
Week 1 Development
- occurs freely floating in uterus
Week 2 Development
- Implantation - initial attachment to uterine wall, and then invasion of the uterine wall.
- Clinically can be detected following implantation (week 2)
- Last Menstrual Period (LMP) - today ? ....... Birth Date - January 25, 2013
- First pregnancy (primipara) 274 days, just over 39 weeks
- Subsequent pregnancies (multipara) 269 days, 38.4 weeks
Median duration of gestation assumed from ovulation to delivery
- Historic - Franz Carl Naegele (1777-1851), first rule for estimating pregnancy length
- Current - Ultrasound, the most accurate staging method
- Divide the pregnancy into 3 "blocks" of about 3 months (trimesters)
- First Trimester - embryonic period (organogenesis)
- Second and Trimester - fetal period (growth)
- 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)
- Uterine body
- posterior, anterior, superior, lateral (most common posterior)
- inferior implantation - placenta overlies internal os of uterus Placenta Previa
- 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
- Materno/fetal organ
- No exchange of blood
- Many different roles
- can be "sampled" as part of a prenatal diagnostic test
- Embryonic Period - Week 1 to 8 (first trimester)
- Establish the basic structure of organs and tissues (Organogenesis)
- development and growth of the placenta (Placentation)
- 3 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)
- Mesoderm (connective tissue)
- Endoderm (epithelium)
- simplified explanation of the 3 layer contributions
- forms the central and peripheral nervous system and epithelium of the skin
- forms gastrointestinal tract organs and the epithelium of the gastrointestinal and respiratory tracts
- forms the body connective tissues: blood, bone, muscle, connective tissue skin, gastrointestinal and respiratory tracts
- segmentation of the mesoderm
- forms the axial body plan
- segmentation of the ectoderm
- separates the neural tissue from the skin (epidermis)
- heart formation (cardiogenesis)
- first functioning organ
- early development of the other organs, tissues and limbs
Week 9 - 38
- Fetal Period - Second and Third Trimester
- 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
- 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.
|Moore, K.L. & Persuad, T.V.N. (2008). The Developing Human: clinically oriented embryology (8th ed.). Philadelphia: Saunders.
|Schoenwolf, G.C., Bleyl, S.B., Brauer, P.R. and Francis-West, P.H. (2009). Larsen’s Human Embryology (4th ed.). New York; Edinburgh: Churchill Livingstone.
The following chapter links only work with a UNSW connection and can also be accessed through this UNSW Library connection.
|Hill, M.A. (2011) UNSW Embryology (11th ed.). Sydney:UNSW.|
- 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 3) 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