Fertilization, Gestation, Growth & Development

Flashcards based on lecture notes about human development and reproduction.

What triggers an erection?

Mechanical stimulation, erotic sights, smells, thoughts, and sounds leading to vasodilation of arterioles in erectile tissue.

What type of innervation causes vasodilation of arterioles in erectile tissue, leading to an erection?

Parasympathetic innervation.

Ejaculation is caused by what type of stimulation?

Sympathetic stimulation.

Which muscles contract to force semen out during ejaculation?

Bulbospongiosus, ischiocavernosus, and superficial transverse perineal muscles.

What is capacitation?

Increased motility and physiological changes to allow sperm to penetrate the oocyte.

What is fertilization?

Merging of genetic information from haploid sperm and haploid secondary oocyte.

How do sperm travel to reach the oocyte?

Swim from the vagina to the cervix, pass through the uterus and uterine tubes mainly due to contractions of the walls of these structures.

What two layers must sperm penetrate for fertilization to occur?

Penetrate the corona radiata and the zona pellucida.

What is the receptor for sperm in the zona pellucida?

Glycoprotein ZP3.

What occurs during the acrosomal reaction???

Acrosomal enzymes are released to digest a path in the zona pellucida.

What does the haploid nucleus in the head of the sperm become?

Male pronucleus.

What does the haploid nucleus of the fertilized ovum become?

Female pronucleus.

What is formed when the male and female pronuclei merge (syngamy or amphimixis)?

Diploid zygote.

How long does gestation (pregnancy) typically last?

Approximately 38 weeks.

What time period defines the embryonic period?

From fertilization to the end of the 8th week.

What time period defines the fetal period?

Begins at week 9 and lasts until delivery (birth).

What is development in embryology?

Cell division and increase in cell size.

What is differentiation in embryology?

As cells divide, subgroups activate different combinations of genes to grow and function in different and unique ways (become specialized).

What type of division does the zygote undergo after fertilization?

Mitotic division called cleavage.

Successive cleavage divisions in the zygote yield smaller and smaller cells, what are these cells called?

Blastomeres.

What is the cluster of cells called by the fourth day, resembling a mulberry?

Morula.

What nourishes the morula when it enters the uterine cavity?

Uterine milk, a glycogen-rich secretion from endometrial glands.

At the 32-cell stage, fluid rearranges the blastomeres creating a large, fluid-filled cavity. What is this mass now called?

Blastocyst.

As the blastocyst forms, what two different cell populations arise?

Embryoblast (inner cell mass) and trophoblast (outer cell mass).

What will the embryoblast (inner cell mass) develop into?

Will develop into the embryo.

What will the trophoblast (outer cell mass) develop into?

Will develop into the outer chorionic sac surrounding the fetus, and the fetal portion of the placenta.

When does the blastocyst implant in the endometrium?

About 6 days after fertilization.

About 8 days after implantation, the trophoblast develops into which two layers?

Syncytiotrophoblast and cytotrophoblast.

Around 8 days, the embryoblast also develops into which two layers?

Hypoblast (primitive endoderm) and epiblast (primitive ectoderm).

Cells of the hypoblast and epiblast form a flat disc, what is this called?

Bilaminar embryonic disc.

From which layer does the amniotic cavity form?

Epiblast.

Cells from which embryonic disc layer form the yolk sac (umbilical vesicle)?

Hypoblast.

On the 9th day, small spaces form, what are these called?

Lacunae.

As embryonic tissue invades the uterine wall and erodes uterine blood vessels, what fills the lacunae?

Blood fills spaces called lacunae.

What is the term for the transformation of the two-layered embryonic disc into a trilaminar (three-layered) embryonic disc?

Gastrulation.

What are the three germ layers formed during gastrulation?

Ectoderm, mesoderm, endoderm.

The first step in gastrulation is the formation of what structure?

Primitive streak.

What structures are produced by the endoderm?

Epithelial lining of digestive canal (except anal canal) and epithelium of its glands; epithelial lining of urinary bladder, gallbladder, and liver; epithelial lining of pharynx, auditory tubes, tonsils, tympanic cavity, larynx, trachea, bronchi, and lungs.

What structures are produced by the mesoderm?

All skeletal and cardiac muscle tissue and most smooth muscle tissue; cartilage, bone, and other connective tissues; blood, red bone marrow, and lymphatic tissue; blood vessels and lymphatic vessels.

What structures are produced by the ectoderm?

All nervous tissue; epidermis of skin; hair follicles, arrector muscles of the hair, nails, epithelium of skin glands (sebaceous and sudoriferous), and mammary glands.

By the end of the 3rd week, blood vessels develop in the chorionic villi and connect to the embryonic heart via what structure?

Connecting stalk.

Vessels connect to the heart via the connecting stalk, specifically through which vessels?

Umbilical arteries and umbilical vein.

During what time frame do all major organs develop (organogenesis)?

Between the 4th through 8th weeks.

During which week does embryonic folding occur, when the flat embryo folds into a three-dimensional cylinder?

4th week.

What is the process of forming the placenta called?

Placentation.

By the beginning of the 12th week, the placenta has what two parts?

Fetal portion (chorionic villi) and maternal portion (decidua basalis of the endometrium).

Which teratogen is the most common cause of developmental defects?

Alcohol.

What period begins at the 9th week after fertilization?

The fetal period.

What primarily occurs during the fetal period?

Tissues and organs that developed during the embryonic period grow and differentiate.

Control of contractions during labor occurs via what type of feedback cycle?

Positive feedback cycle.

What are the three stages of true labor?

Stage of dilation, Stage of expulsion, Placental stage.

Which hormone primarily stimulates milk production?

Prolactin (PRL).

Which hormone causes the release of milk into the mammary ducts via the milk ejection reflex?

Oxytocin.

List the stages of postnatal development.

Neonatal (Birth to 1 month), Infancy (1 month to 2 years), Childhood (2 years to adolescence), Adolescence (beginning at puberty and extending to physical adult maturity), Maturity (Period after physical maturity to senescence), Senescence (Approx. age 30 until death).