Pregnancy

M- endometrium N- cavity of uterus

M, N

Maternal and embryonic blood supplies do not intermix.

Maternal and embryonic blood supplies do not __________.

Membranes of the two pronuclei rupture and the chromosomes combine to form a zygote.

Membranes of the two pronuclei rupture and the chromosomes combine to form a __________.

extraembryonic membranes

amnion, chorion, yolk sac, and allantois forms during first 2-3 weeks

inner cell mass

becomes the embryonic disc (---> embryo and three of the embryonic membranes)

implantation

begins 6-7 days after ovulation

embryonic disc

blastocyte develops into a double layer of cells that will become the embryo

chorion

cells from the original inner cell mass give rise to a layer of extraembryonic mesoderm lining the inner surface of the trophoblast. Together, these become the __________. Outermost layer of the two membranes surrounding the embryo; it forms the fetal part of the placenta.

syncytiotrophoblast

cells in the outer layer lose their plasma membranes, invade and digest the endometrium

fetus

conceptus from week 9 through birth

decidua capsularis

endometrial cells that surround the implanted embryo

zygote (fertilized egg)

A

cleavage

A period of fairly rapid mitotic divisions of zygote after fertilization, without much growth between cells. - Results in progressively smaller cells.

cortical reaction

Caused by the calcium surge from the oocytes ER. Granules located just inside the plasma membrane spill their enzymes into the extracellular space beneath the zona pellucida.

blastocyst

fluid-filled hollow sphere composed of a single layer of large, flattened cells called trophoblast cells and a small cluster of 20 to 30 rounded cells, called the inner cell mass, located at one side

blastocyst

fluid-filled hollow sphere composed of a single layer of trophoblast cells and inner cell mass clinging on the inside.

placentation

formation of the placenta from embryonic and maternal tissues

embryonic period

from fertilization through the eighth week of development

Cleavage at 72 hours ---> morula (16 or more cells)

Cleavage at 72 hours ---> ____________________________

Early blasocyst

D - (morula hollows out, fills with fluid, and "hatches" from the zona pellucida-4 days)

gestation period

Development occurs during this time, which extends by convention from the last menstrual period until birth, approximately 280 days

cytotrophoblast (inner layer) and syncytiotrophoblast (outer layer)

During implantation, trophoblast cells proliferate and form two distinct layer which are ________ and ______.

During implantation: - Trophoblast adheres to a site with the proper receptors and chemical signals on the endometrium. - Produces enzymes that irritate the endometrium. - Inflammatory-like response occurs in the endometrium. - 2/3 fail to implant. 30% of implants spontaneously abort.

During implantation: - __________ adheres to a site with the proper receptors and chemical signals on the endometrium. - Produces enzymes that irritate the endometrium. - __________ response occurs in the endometrium. - 2/3 fail to implant. 30% of implants spontaneously abort.

Implanting blastocyst

E -(consists of a sphere of trophoblast cells and an ecentric cell cluster called the inner cell mass - 7 days)

ovulation

For successful fertilization to occur, coitus (sexual intercourse) must occur no more than 2 days before _________ and no later than 24 hours.

placenta is usually fully functional by the end of the third month of pregnancy

Generally speaking, when does the placenta become fully functional?

I- Oocyte (egg) J- ovulation K- ovary

I, J, K

maternal tissue

Identify the tissue: - Decidua basassi (stratum functionalis between chorionic villi and stratum basalis of endometrium) develops blood-filled lacunae.

embryonic tissue

Identify the tissue: - Mesoderm cells develop from the inner cell mass and line the trophoblast. - Together these form the chorion and chorionic villi.

Implantation - The implanted blastocyst is covered over by endometrial cells. - Implantation is completed by the 12th day after ovulation. - Trophoblast cells secrete human chorionic gonadotropin (hCG).

Implantation - The implanted blastocyst is covered over by __________. - Implantation is completed by the ____ day after ovulation. - Trophoblast cells secrete ____________________________.

1. Cytotrophoblast 2. Synctiotrophoblast

Implantation - Trophoblast cells proliferate and form 2 distinct layers:

Implantation - Uterine capillaries become permeable & leaky.

Implantation - Uterine capillaries become __________ & __________.

embryo

name of the conceptus from fertilization through week 8

fertilization

occurs when a sperm's chromosomes combine with those of an egg (secondary oocyte) to form a fertilized egg (zygote)

monospermy

only one sperm is allowed to penetrate the oocyte

pregnancy

refers to events that occur from the time of fertilization (conception) until the infant is born

placentation

the formation of a placenta

conceptus

the pregnant woman's developing offspring

fetal period

time from week 9 through birth

- epiblast (upper) - hypoblast (lower

two layers the inner mass subdivides into

oocyte membrane block and zona reaction

two mechanisms that help ensure monospermy

oocyte membrane block

when a sperm binds to sperm-binding receptor on oocyte, it causes oocyte to shed all other sperm-binding receptors - other sperm can no longer bind to oocyte plasma membrane

female pronucleus

when the oocyte goes through meiosis II (forms ovum nucleus and second polar body), the ovum nucleus swells, becoming the __________, and the two pronuclei replicate their DNA as they approach each other.

blastomeres

~ 36 hrs after fertilization - first cleavage division of the zygote producing two identical daughter cells which continuously divide

morula

~ 72 hrs after fertilization - loose collection of cells that form a berry-shaped cluster of 16 or more cells

morula

C (solid ball of blastomeres-3 days)

decidua basalis

- part of the endometrium that lies beneath the embryo - maternal portion of placenta

zona reaction

(also called the slow block to polyspermy) alters the physical characteristics of the zona pellucida - once sperm has entered the oocyte, waves of Ca+ are released by the oocyte's endoplasmic reticulum into its cytoplasm, which activates the oocyte to prepare for the second meiotic division

chorionic villi

- Grow into blood-filled lacunae (intervillous spaces). - Vascularized by umbilical arteries and veins. - Lie immersed in maternal blood.

human chrionic gonadotropin (hCG)

- LH -like hormone secreted by trophoblast cells - bypasses hypothalamic-pituitary-ovarian controls and prompts the corpus luteum to continue secreting progesterone and estrogen

trophoblast cells

- Single layer of cells - Surfaces have factors that are immunosuppressive - Participate in placenta formation

cleavage

- period of fairly rapid mitotic divisions of the zygote without intervening growth - goal is to produce small cells with a high surface-to-volume ratio that enhances their uptake of nutrients and oxygen and disposal of wastes. - provides large number of cells to serve as building blocks for constructing the embryo

trophoblast cells

- single layer of large flattened cells - surfaces have factors that are immunosuppressive - participate in placenta formation

inner cell mass

- small cluster of 20-30 rounded cells - becomes the embryonic disc - forms the embryo proper and 3-4 extraembryonic membranes

implantation

6-7 days after ovulation _________ begins.

male pronucleus

-swollen nucleus of sperm -migrates to center of cell

A sperm can now approach the oocyte: - An acrosomal process forms and binds to receptors. - Oocyte and sperm membranes fuse &the sperm cell nucleus is pulled into the cytoplasm of the oocyte. - Only one sperm is allowed to penetrate the oocyte (monospermy).

A sperm can now approach the oocyte: - An __________ process forms and binds to receptors. - __________ and __________ membranes fuse &the sperm cell nucleus is pulled into the cytoplasm of the oocyte. - Only ____ sperm is allowed to penetrate the oocyte (monospermy).

Accomplishing fertilization involves a process of weakening the sperm cell membrane to allow the release of hydrolytic acrosomal enzyme. - Secretions of the female tract weaken the sperm cell membrane.

Accomplishing fertilization involves a process of weakening the sperm cell membrane to allow the release of ______________________________. - __________ of the female tract weaken the sperm cell membrane.

Human Chorionic Gonadotropin (hCG)

Acts on the corpus lute to maintain its estrogen and progesterone production until the placenta can adequately support the developing fetus.

. The blastocyst secretes the hormone human chorionic gonadotropin, which is detectable in the urine

Amber, wondering if she is pregnant, buys an over-the-counter pregnancy test to assess this possibility. How will the blastocyst, if present, "make itself known"?

At day 3 or 4, the embryo of early blastocyst has reached the uterus.

At day 3 or 4, the embryo of early __________ has reached the uterus.

4-cell stage (2 days)

B

Early embryonic development begins after fertilization and continues as the embryo moves into the uterus where it will implant in the uterine wall. Significant events of this early embryonic period are cleavage,which produces a structure called a blastocyst, and implantation of the blastocyst.

Early embryonic development begins after _________ and continues as the embryo moves into the uterus where it will implant in the uterine wall. Significant events of this early embryonic period are _______,which produces a structure called a blastocyst, and _______ of the blastocyst.

Ejaculated sperm: - Leak out of the vagina immediately after deposition. - Are destroyed by the acidic vaginal environment. - Fail to make it through the cervical mucus. - Are dispersed in the uterine cavity or destroyed by phagocytes. - Few (100 to a few thousand) reach the uterine tubes.

Ejaculated sperm: - Leak out of the vagina immediately after __________. - Are destroyed by the ____________________. - Fail to make it through the __________ mucus. - Are dispersed in the __________ cavity or destroyed by __________. - Few (100 to a few thousand) reach the __________ tubes.

1. Membranes of the chorionic villi. 2. Endothelium of embryonic capillaries.

Embryonic placental barriers include:

polyspermy

Entry of several sperm into an egg

Zonal Inhibiting Proteins (ZIP's)

Enzymes released in the cortical reaction. Destroy sperm receptors, preventing sperm from further entering the oocyte.

gastrula

Even while implantation is occurring, the blastocyst is being converted to a _____, in which the three primary germ layers form, and the extraembryonic membranes develop.

amnion

Extraembryonic Membranes: epiblast cells form a transparent sac filled with amniotic fluid - provides buoyant environment that protects the embryo - helps maintain a constant homeostatic temperature - allows freedom of movement and prevents parts from fusing together - amniotic fluid comes from maternal blood, and later, fetal urine

F- sperm G- uterine tube H- fertilization (sperm meets and enters egg)

F, G, H

Lacunae or Intervillous spaces

Filled with blood. Are in the stratum functualis of the endometrium .

First cleavage at 36 hours ---> two daughter cells (blastomeres)

First cleavage at 36 hours ---> ____________________________

For fertilization to occur, coitus must occur no more than: - Two days before ovulation to 1 day after ovulation. - (Sperm is viable 24 to 48 hours after ejaculation & oocyte is viable for 12 to 24 hours)

For fertilization to occur, coitus must occur no more than: - __________ days before ovulation to 1 day after ovulation. - (Sperm is viable __________ to __________ hours after ejaculation & oocyte is viable for __________ to __________ hours)

O- trophoblast P- blastocyst cavity Q- inner cell mass

O, P, Q

Sperm binds to the zona pellucida and undergoes the acrosomal reaction. - Enzymes are released to digest holes in the zona pellucida. - Hundreds of acrosomes must release their enzymes to digest the zones pellucida.

Sperm binds to the __________ and undergoes the acrosomal reaction.

The Ca2+ surge triggers completion of meiosis II.

The Ca2+ surge triggers completion of __________.

ovum nucleus and second polar body.

The sperm penetrates the secondary oocyte and the secondary oocyte begins to have calcium surges. This triggers the completion of meiosis II forming the _________ and __________.

zygote

The true moment of fertilization occurs as the maternal and paternal chromosomes combine and produce the diploid __________, or fertilized egg.

chorionic villi

These are finger like projections that form the fetal portion of the placenta. By the 8th week, chorionic villi sampling is possible.

To fertilize an egg, sperm must be capacitated before they can penetrate the oocyte.

To fertilize an egg, sperm must be __________ before they can penetrate the oocyte.

placenta

Together, the chronic villi and decidua basalis form the disc-shaped _____.

corona radiata and zona pellucida

Two oocyte coverins sperm must break through

Upon entry of a sperm, a Ca2+ surge from the oocyte's ER into the cytoplasm causes the cortical reaction. - Cortical granules release enzymes ( zonal inhibiting proteins, or ZIPs) - ZIPs destroy sperm receptors. - Spilled fluid from granulocytes bind water and swells, detaching other sperm (slow block to polyspermy)

Upon entry of a sperm, a __________ surge from the oocyte's ER into the cytoplasm causes the cortical reaction.

The decidua basalis cooperates with the chorionic villi to form the placenta.

What endometrial decidua cooperates with the chorionic villi to form the placenta?

Acrosomal reaction - Binding of the sperm to the receptors in the zona pellucida causes Ca+ levels within the sperm to rise, triggering acrosomal reaction. - Acrosomal enzymes from many sperm digest holes through the zona pellucida, clearing a path to the oocyte membrane

What event is occurring?

Binding - The sperm's membrane binds to the oocyte's sperm-binding receptors

What event is occurring?

Blocks to polyspermy. - Oocyte sperm-binding membrane receptors are shed. Ca2+ levels in the oocyte's cytoplasm rise, triggering the cortical reaction (exocytosis of cortical granules). - As a result, the zona pellucida hardens and the zona pellucida's sperm-binding receptors are clipped off.

What event is occurring?

Fusion - Sperm and oocyte plasma membranes fuse. Sperm contents enter the ooctye

What event is occurring?

Before they can penetrate an oocyte, sperm must be capacitated, and an oocyte's zona pellucida must be eroded by the acrosomal enzymes of many sperm. - (Involves a process of weakening the sperm membrane to allow the release of hydrolytic acrosomal enzymes) - (secretions of the female tract weaken the sperm cell membrane)

What has to happen before ejaculated sperm can penetrate an oocyte?

The chorion develops from the trophoblast and a layer of extraembryonic mesoderm

What is the composition of the chorion?

- The cortical reaction involves the release of enzymes from cortical granules to the oocyte exterior,. - accomplishes destruction of the zona pellucida sperm-binding receptors and also the detachment of any sperm still bound to these receptors. These events help ensure monospermy.

What is the cortical reaction and what does it accomplish?

synctiotrophoblast

Which portion of the trophoblast accomplishes implantation?

The blastocyst is only slightly larger than the zygote because, although cell division has been going on (cleavage divisions), there is essentially no time for growth between divisions, so the resulting cells get smaller and smaller. The result is a large number of cells with a high surface-to-volume ratio. - or in other words, there are no additional nutrients being added to the blastocyst as it divides.

Why is the multicellular blastocyst only slightly larger than the single-celled zygote?

polyspermy

__________ (fertilization by more than one sperm cell) leads to a lethal number of chromosomes and must be prevented.

Early embryonic development begins after fertilization and continues as the embryo moves into the uterus, where it will implant in the uterine wall.

____________________ begins after fertilization and continues as the embryo moves into the uterus, where it will implant in the uterine wall.

placenta

a temporary pancake-shaped organ that originates from both embryonic and maternal (endometrial) tissues

cytotrohpoblast (cellular trophoblast)

inner layers of cells

acrosomal reaction

involves the release of acrosomal enzymes (hyaluronidase, acrosin, proteases, and others) that digests holes through the zona pellucida

Syncytiotrophoblast

lining of villi; produces hCG and human placental lactogen - produces estrogen and progesterone of pregnancy