Home > Anatomy, Biology > Introduction to Human Anatomy Lecture 63 Notes: Human Embryology

Introduction to Human Anatomy Lecture 63 Notes: Human Embryology


Well, we are running out of classes from Ratfink.  He has a series on embryology which we’ll begin today.  This opening lecture costs 63 minutes.


Embryology is prenatal development.  Sexual reproduction is the fusion of haploid sex cells.  Fertility issues are becoming more common; IVF is a common solution.

The egg is much larger than the sperm.  The egg is the largest of all human cells while the sperm is the smallest.

Diploid number of chromosomes is 46.  All body cells are genetically identical.  Formed by mitosis.

Gametes have the haploid number of chromosomes, 23.  Meiosis forms them and they are genetically unique.

Sperm are produced within the testes.  The head has a nucleus and acrosome.  The tail is how it transports itself.

Meiosis involves two consecutive cell divisions from 92 into 23 chromosomes.  The egg divides unequally making a large egg and 3 small polar bodies.  The egg needs to be large because the woman is more invested in the embryo.

The cervix into the vagina into the uterus into the ovicuts/fallopian tubes to the ovary.  When the egg pops out, it enters the fallopian tubes.  The egg cannot move on its own; cilia move it.  Endometrium is the inner layer of the vagina; the myometrium of the uterus is the outer layer and it exists to contract.

The blood vessels of the endometrium are shed during menstruation.  An egg needs many sperm around it to “capacitate” or activate the egg for one to enter.

The gamete has 22 autosomes and 1 sex chromosome.

3 Phases:

Pre Embryonic

The first 3 weeks of development.  The zygote is the first body cell.  An ectopic pregnancy is when the zygote stays in the fallopian tubes.

Morella is a “raspberry” stage of 16 cells.  After that comes the blastocyst.

During the first week, the zygote is fed by the egg itself.  In the first day and a half, the egg becomes two cells.

The trophoblast is the outer layer of the blastocyst.  At one end is inner cell mass.

Amnion or amniotic sac is where the chick grows up.  the yolk of an egg.  Waste products into the alantoic sac.  The belly button is where the umbilical used to connect.

The corionic villi are fingerlike projections that connect the egg to the placenta.  The decidua basalsa of the endometrium contains maternal blood vessels.

In time, the ICM becomes the ectoderm, mesoderm, endoderm.  The endoderm becomes the alimentary canal or digestive tract.  The mesoderm becomes the muscles and the ectoderm becomes the skin.

Amniocentesis or CVS corionic villi sampling are used to test for genetic defects in the baby.

By week 4, all major organs are formed.

amnion: membrane of amniotic sac

chorion: membrane of chorionic sac


Cellular transportation: microvilli, flagellum, cilia

C elegans: the developmental fate of every somatic cell is known.  959 in hermaphrodite.  Dauer stage.

Strong bases make poor leaving groups.  Good leaving groups form stable ions or molecules.

The higher the pKa of the conjugate acid, the better the nucleophile.

Stable cations favor SN1 reactions.  SN2 reactions are concerted and require little steric hinderance.

Acids are corrosive, bases are caustic

Protic solvents form hydrogen bonds.  They produce a cation and anion during the reaction and favor SN1.

3 minutes without air – 3 hours without shelter – 3 days without water – 3 weeks without food.

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