Cpm Study Cards: Embryology & Fetal Development

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Fetal development: 42 weeks

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post-term/ post-dates

vernix decreases, skin may dry/peel, weight loss or placental insufficiency may occur

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Fetal development: 37-41 weeks

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considered term for most babies

majority of babies born within this time frame

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pulmonary surfacants

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lecithin & sphingomyelin

aid alveoli in air retention & keeps them from collapsing after birth

amniocentisis can test L/S ration if premature delivery is likely

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Fetal development: 34-37 weeks

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fetal lungs mature

critical that pulmonary surfacants are adequate to prevent respiratory distress at birth

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Fetal development: 24-34 weeks

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testicles begin decent in male fetus

additional fat is stored

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Fetal development: 22-24 weeks

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considered age of viability although mortality and morbidity are high

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brown fat

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subcutaneous adipose tissue

important for temperature regulation and heat production

when neonate is cold, brown fat is metabolized to create heat

limited resource

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Fetal development: 16-20 weeks

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quickening usually occurs

vernix and lanugo present

eyebrows and eyelashes form

brown fat forms

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fetal development: 12-16 weeks

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slow eye movement

bright pink skin

more facial features discernible

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fetal development: 8-12 weeks

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fingernails and toenails begin

hair begins development

ossification continues

fetus moves, swallows amniotic fluid, & urinates

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fetal development: 8 weeks

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embryo now a fetus

blood vessels and organs begin to form

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fetus

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embryo is known as a fetus at 8 weeks

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decidua vera

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3rd layer of the decidua, lining the majority of pregnant uterus

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decidua capsularis

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decidua layer surrounding the embedded ovum

as embryo grows, this layer distends

at week 12, the fetus grows enough to contact the decidua vera and the capsilaris degenerates and disappears

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decidua basalis

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decidua layer beneath the embedded ovum

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decidua

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the endometrium after fertilization

3 layers: decidua basalis, decidua capsularis, decidua vera)

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embryonic timeline

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1. ovum/ ovulation
2. ovum + spermatozoa join and produce a diploid cell. fertilization occurs in the fallopian tube.
3. zygote = diploid cell
4. day 1: zygote has 2 cells
5. day 3: zygote has 16 cells; now a morula
6. day 4: 58 cells; now a blastocyst (made of blastomeres and a blastocele)
7. day 3-5: enters the uterus
8: week 2: implantation into endometrium. now an embryoblast

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amnion

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sac surrounding the fetus, creating amniotic cavity where the blastocele was

fused to the chorion

creates the BOW

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chorion

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will surround the blastocyst

will form part of placenta; will fuse with amnion to become the 2-layered fetal membrane on the maternal side

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allantois

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vascularized membrane whose blood vessels will, in the umbilical cord, aid maternal-fetal circulation

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extra embryonic mesoderm

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layer of cells that does not contribute to the formation of the embryo itself

peels off to become the chorion, amnion, allantois, and yolk sac

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chorionic villi

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developed from the trophoblast (the outer layer of the blastocyst)

finger-like projections which grow out and "plant" into the decidua, eventually forming the placenta

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blastocyst

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5 days after fertilization, the morula begins to enter the uterine cavity and has formed a hallow ball of cells called the blastocyst

surrounded by a fluid-filled cavity called the blastocele

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endoderm

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forms epithelial cells lining the digestive, respiratory, and urinary systems, and glandular cells of the organs such as the liver and pancreas

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mesoderm

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forms the muscle, skeleton, derms of the skin, connective tissue, the urogenital glands, blood vessels, and blood & lymph cells

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ectoderm

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start of the tissue that covers most surfaces of the body, epidermis layer of the skin, hair, & nails, and forms the nervous system

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trophoblast

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the outer cell mass of the blastocyst

becomes the placenta and chlorion

implants into the decidua on week 2

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embryoblast

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inner cell mass of the blastocyst

becomes the embryo, amnion, chorion, and umbilical coard

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blastulation

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process from the development of the blastocyst from the morula (day 4)

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blastocele

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fluid filled cavity

develops in morula on day 4

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cavitation

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in pre-embryonic period, (day 3-4) the outermost cells of morula secrete fluid and a fluid-filled cavity (blastocele) appears in the morula

results in formation of the blastocyst

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compaction

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the process of tightly binding zygotic cells together

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morula

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"mulberry"

the zygote on day 3, now has 16 cells

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pre-embryonic period

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first 2 weeks after fertilization

includes implantation of the zygote into the endometrium

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blastomeres

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formation of smaller zygotic cells during the pre-embryonic period

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cleavage

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the rapid cell division occurring after fertilization

by day 3, there are 16 cells

mitotic process

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cortical reaction

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chemical reaction occurring upon penetration of the zona pellucida by a single spermatozoa

makes the ovum impenetrable to other sperm

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zygote

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the new diploid cell formed after the joining of the ova and spermatozoa haploid cells (fertilization)

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dizygotic twins

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"fraternal twins"

when 2 spermatozoa fertilize two ovum in the same cycle

more common than monozygotic twins

can be hereditary

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monozygotic twins

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when fused pronuclei divide, creating two separate by identical structures.

may or may not share an amnion and placenta

not hereditary

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corona radiata

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outmost layer of the zona pellucida of the ovum

once penetrated by a spermatozoa, the ovum immediately develops a fertilization membrane, barring all other sperm from entering

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zona pellucida

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gelatinous covering surrounding the ovum

consists of several layers of cells

broken down by sperm enzymes

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oogenesis

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creation of the ovum

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pronucleus

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nucleus of sperm or egg cell after sperm enters the egg

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cytokenisis

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process of splitting a binucleate cell in 2

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corona radiata

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surrounds ova, provides protein

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nidation

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implantation of embryo into the uterine lining

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gametes

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ova/egg & sperm

germ cells

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meiosis

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the reproductive process involving 2 successive divisions of a cell resulting in 4 daughter cells

daughter cells not identical

process which creates germ cells

daughter cells have half the number of chromosomes as a normal cell

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spermatocyte

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a cell of the seminiferous tubule that is engaged in meiosis

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spermatogenesis

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production of spermatozoa

mitotic cell division which produces 2 daughter cells: one is spermatogonium; the other is a primary spermacyte that will begin the meiosis process

takes place in the seminiferous tubules

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spermatazoon/ spermatozoa

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spermatozoon- sperm, plural

spermatozoon- sperm, singular

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spermiogenesis

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the last step of spermatogenesis in which spermatid mature into single spermatazoon

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spermatid

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immature male gamete

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order of spermatogenesis

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1. mitosis of spermatogonia
2. DNA replication
3. synapsis and tetrads form
4. meiosis 1 (primary spermacytes)
5. meiosis 2 (secondary spermacytes)
6. spermiogenesis- spermatids transform into mature spermatozoa

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parts of a spermatzoon

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head- contains nucleus with densely packed chromosomes

acromosal cap- membranes compartment at tip of head; has enzymes for fertilization

middle piece- site of mitochondrial activity

tail- only flagellum in the human body. uses whip-like action to propel the sperm towards the ovum

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sperm count

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ranges from 20 million to 100 million spermatazoon per mL of semen

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smegma

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waxy material secreted by the preputial glands of the penis

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oogenesis

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production of ovum begins before a woman's own birth, accelerates at puberty, and ends at menopause

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oogenia

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stem cells in females

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primary oocytes

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mitosis is complete before birth, creating daughters cells called primary oocytes

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polar bodies

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byproducts of oogenesis

non-functional cells produced in the meiosis process that later disintegrate

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egg nests

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clusters of primary oocytes and their follicle cells located in the outer portion of the ovarian cortex

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primordial follicle

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the primary oocyte and its follicle cells

after puberty, a different group of primordial follicles is activated each month during the follicular phase of the ovarian cycle

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primary follicles

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created when, in activated primordial follicles, the follicular cells enlarge and undergo repeated divisions to create several layers of follicle cells around the oocyte

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granulosa cells

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the follicular cells of the primary follicles after they enlarge and undergo several divisions; rounds in appearance

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thecal cells

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formed in the ovarian stroma around the follicle as the granulosa cells enlarge and multiply

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follicular fluid

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secreted by granulosa cells as the walls of the follicle thicken

accumulates in small pockets that gradually expand and separate inner and outer layer of follicle

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secondary follicle

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primary follicle after the accumulation of follicular fluid

enlarges rapidly as the fluid accumulates

8-10 days after start of ovarian cycle, only 1 secondary follicle is destined to develop

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tertiary follicle

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on the 10-14th day of the ovarian cycle, the secondary follicle has become a tertiary follicle

mature graafian follicle is approximately 15mm in diameter

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male climacteric

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aka: andropause

period of declining reproductive function, corresponding to perimenopause in women

generally occurs between the ages of 50 and 60