Embryology Exam 1

What is the correct order of fertilization 1. Fusion of the oocyte and sperm cell membranes 2. Penetration of the corona radiata 3. Penetration of the zona pellucida a. 1, 2, 3 b. 2, 1, 3 c. 3, 1, 2 d. 2, 3, 1

d. 2, 3, 1 Phase 1 - Penetration of the corona radiata Phase 2 - Penetration of the zona pellucida Phase 3 - Fusion of the oocyte and sperm membranes

How many primary oocytes are ovulated during a woman's life time? a. 600,000 - 800,000 b. 400, 000 c. 15,000 d. 500

d. 500

What is the characteristic event of the third week that established the three germ layers of ectoderm, endoderm, and mesoderm?

gastrulation

What hormone is given off by the syncytiotrophoblast at implantation around day nine. This hormone triggers to corpus luteum to develop into the corpus luteum of pregnancy. This hormone indicates that the embryo has implanted.

hCG

What is caused by trophoblast cells with little to no embryonic tissue that form a mass of chorionic villi clusters. These secrete high levels of hCG and can cause benign or malignant tumors. These occur when an oocyte without a nucleus is fertilized by one or two sperm which replicate their DNA to make a 100% paternal genome.

hydatiform moles

The epiblast and hypoblast form from stem cells of the _____________?

inner cell mass

Large cavities that form in the extraembryonic membrane and group together, form the ?

new extraembryonic cavity or chorionic cavity

The beginning of gastrulation is marked by the formation of _______ on the dorsal surface of the epiblast?

primitive streak

What cells move into the primitive pit and then move cranially until they reach the prechordal plate?

pronotochordal cells

The extraembryonic mesoderm splits into what two layers?

somatic and splanchnic layers

What condition can occur when the blastocyst implants in an abnormal location outside the uterus?

ectopic pregnancy

Cells from the epiblast slipbeneath and displace the hypoblast forming what layer?

endoderm

All three germ layers originate from ?

epiblast

Cells between the exocoelomic cavity and the cytotrophoblast start to come together to form a loose connective tissue known as the ?

exocoelomic membrane

True or False. The secondary oocyte enters meiosis II, but arrests in anaphase about 3 hours before ovulation?

False. Arrests in metaphase.

True or False. After stimulation from LH, the theca externa produce androgens?

False. Theca interna produce angrodens (orostenedione and testosterone.

True or False. As opposed to mitosis, in meiosis centromeres do not divide. There are two sister chromatids that do not separate, they simply migrate together.

True

True or False. Gametes are derived from primordial germ cells that are formed in the epiblast during the second week and move to the wall of the yolk sac?

True

True or False. There are no replications of chromosomes prior to meiosis II.

True

True or False. When the sperm and egg meet, progesterone facilitates a more calm environment to allow to implantation.

True

True or false. Under the influence of FSH, androgens produced by the granulosa cells are converted to estrogens.

True

the trophoblast is made up of two sections. Th inner most layer of mononucleated cells is known as?

cytotrophoblast

During the second week of development, the trophoblast differentiates into: A. syncytiotrophoblast B. ectoderm C. intraembryonic mesoderm D. yolk sac (secondary)

A. syncytiotrophoblast The trophoblast gives rise to both the syncytiotrophoblast and the cytotrophoblast, as well as the extraembryonic mesoderm. The ectoderm is a derivative of the epiblast, and the secondary yolk sac comes from endoderm cells that line the exocoelomic cavity or the primitive yolk sac.

The first two intraembryonic germ layers to differentiate are the: A. ectoderm and hypoblast B. epiblast and hypoblast C. ectoderm and endoderm D. ectoderm and mesoderm

B. epiblast and hypoblast The epiblast and hypoblast develop from the inner cell mass during the 2nd week. During the 3rd week, the epiblast produces cells between itself and the hypoblast, called the mesoderm. Epiblast also replaces the hypoblast with endoderm cells. Epiblast then changes its name to ectoderm, completing the process of gastrulation.

During development, the notochordal process: A. arises from involuting endodermal cells B. extends from the prochordal plate to the primitive node C. is involved in the induction of the primitive gut D. becomes the appendicular skeleton

B. extends from the prochordal plate to the primitive node The notochordal process extends from the primitive node up to the prochordal plate. It develops into the notochord, around which the vertebral column forms. The notochord is not endodermal, and does not induce the primitive gut. It persists in the adult only as the nucleus pulposus of the intervertebral discs.

The notochord is replaced by the: A. ependyma B. nucleus pulposus C. spinal canal D. dorsal roots E. spinal cord

B. nucleus pulposus The notochord is the forerunner of the vertebral column. As it is replaced by the vertebral column, it degenerates. All that remains of the notochord in the adult is the nucleus pulposus in the intervertebral discs, surrounded by the sclerotome-derived annulus fibrosus.

Chorionic villi are designated as secondary chorionic villi when they: A. contact the decidua basalis B. are covered by syncytiotrophoblast C. develop a mesenchymal core D. give rise to branch villi E. none of the above

C. develop a mesenchymal core All chorionic villi possess an outer layer of syncytiotrophoblast. The cytotrophoblast shell is a feature of the mature chorion. Extraembryonic somatic mesoderm forms the core of secondary villi, becoming tertiary with vascular development. Primary villi, at 14 days, are syncytial processes with a core of cytotrophoblast.

The seven-day blastocyst: A. has a single layer of trophoblast at the embryonic pole B. has an amniotic cavity C. is attached to the endometrial epithelium D. is surrounded by a degenerating zona pellucida E. is called the hypoblast

C. is attached to the endometrial epithelium The decidual reaction of the endometrium creates a nourishing environment for the conceptus a it buries itself by invasion of the uterine endometrial wall. Progesterone produced by the corpus luteum stimulates glandular secretion in the endometrium during the secretory phase of menstruation or early pregnancy.

When chorionic villi become vascularized they are called _____ villi. A. branch B. stem C. tertiary D. anchoring E. mature

C. tertiary As secondary chorionic villi become vascularized, they become known as tertiary villi. Maturation of the villi involves thinning of the placental barrier, so that only a thin layer of syncytium, extracellular matrix and endothelium separates maternal and fetal blood.

The primitive streak first appears at the beginning of the _____ week. A. first B. second C. third D. fourth E. fifth

C. third Gastrulation, the process of formation of the three germ layers, occurs during the third week. Epiblast cells form a thickening called the primitive streak, with a primitive knot or node located at its cranial end. Epiblast cells invaginate from this streak to form the mesoderm layer and to replace hypoblast with endoderm.

The amniotic cavity develops: A. on the tenth day B. within the outer cell mass C. within the inner cell mass near the cytotrophoblast D. in extraembryonic mesoderm E. none of the above

C. within the inner cell mass near the cytotrophoblast The amniotic cavity begins to develop around the 8th ay as a slit-like area within the epiblast near the cytotrophoblast. It usually has a thin strip of epiblast cells, called amnioblasts, between it and the cytotrophoblast.

The part of the sperm containing proteolytic enzymes to digest the zona pellucida is the: A. capacitor B. head C. corona D. acrosome E. cumulus

D. acrosome The acrosome is the part of the sperm containing proteolytic enzymes to digest the zona pellucida. It is exposed by the process of capacitation. Then, under the influence of substances released by corona radiata cells, it releases its proteolytic enzymes and penetrates the oocyte.

The early stages of cleavage are characterized by: A. formation of a hollow ball of cells B. formation of the zona pellucida C. increase in the size of the cells in the zygote D. increase in the number of cells in the zygote E. none of the above

D. increase in the number of cells in the zygote The earliest stages of cleavage are marked by a series of mitotic divisions that increase the number of cells in the zygote without an increase in size. As the cleavage continues the zygote becomes a morula or a solid ball of 12-16 cels. A cavity forming within the morula transforms it into a blasocyst, at about day 4.

Capacitation of the sperm: A. is caused by the zona pellucida B. occurs in the male C. prevents polyspermy D. is essential for fertilization E. removes the head of the sperm

D. is essential for fertilization Capacitation involves removing the glycoprotein coat and seminal plasma proteins from the head of the sperm, exposing the acrosome and allowing the acrosome reaction to occur. Capacitation occurs within the female genital tract, and without its occurrence, fertilization could not occur.

The primitive streak: A. is derived from the outer cells of the morula B. is formed during the second week in development C. persists as the cloacal membrane D. is the site of involution of epiblast cells to form mesoderm E. was done in a bathing suit, for those who remember streaking

D. is the site of involution of epiblast cells to form mesoderm The primitive streak begins to form on the surface of the epiblast at the beginning of the third week. It is at the primitive streak that epiblast cells invaginate to form the mesoderm, through the process of gastrulation.

The ovulated mammalian oocyte is arrested at: A. prophase of meiosis I B. metaphase of meiosis I C. prophase of meiosis II D. metaphase of meiosis II E. none of the above

D. metaphase of meiosis II The long arrest in meiosis occurs in the primary oocyte. These descendants of oogonia begin meiosis before birth and stop dividing during prophase of the first division. Years later, this first division is completed just prior to ovulation. Ovulated secondary oocytes then stop at metaphase II until fertilized.

In the third week of human embryonic development: A. the amnion appears B. a bilaminar embryonic disc is formed C. the body stalk moves ventrally and joins with the yolk sac stalk to form the umbilical cord D. the neural plate is induced by the notochordal process and associated mesoderm E. the uteroplacental circulation is established

D. the neural plate is induced by the notochordal process and associated mesoderm It is during the third week that the notochordal process and its associated mesoderm induce the neural plate. The hollow notochordal process eventually becomes the solid notochord, the forerunner of the axial skeleton.

. The first week of human development is characterized by formation of the: A. inner cell mass B. hypoblast C. trophoblast D. blastocyst E. all of the above

E. all of the above At four days, the blastocyst cavity of blastocele forms within the morula. Trophoblast are outer cells of the blastocyst, while a knot of cells appears, protruding into the blastocele. This is the inner cell mass. Trophoblast becomes 2 layers: syncytiotrophoblast and cytotrophoblast. Inner cell mass becomes epiblast and hypoblast.

Somites: A. differentiate into myotomes which give rise to skeletal muscle in trunk and limbs B. differentiate into sclerotomes which give rise to vertebrae C. arise from segmentation of the paraxial mesoderm D. differentiate into myotomes which give rise to skeletal muscle of the limbs E. all of the above are correct

E. all of the above are correct. Somites differentiate into sclerotomes, myotomes and dermatomes. The sclerotomes give rise to the vertebrae. The myotomes give rise to skeletal muscle of the trunk and limbs. The dermatomes give rise to the dermal skin component. The skeletal muscle of the face arises from the pharyngeal arches.

During implantation, the blastocyst: A. implants in the endometrium B. usually attaches to endometrial epithelium at its embryonic pole C. usually implants in the posterior wall of the body of the uterus D. causes change in the endometrial tissues E. all of the above are correct

E. all of the above. Implantation occurs when the trophoblast cells at the embryonic pole secrete proteolytic enzymes that allow the blastocyst to penetrate the wall of the uterus, usually the posterior wall. The endometrial lining responds to implantation through the decidua reaction, by which it becomes more succulent for nourishing the blastocyst.

The most distinctive characteristic of a primary chorionic villus is its: A. outer syncytiotrophoblastic layer B. cytotrophoblastic shell C. extraembryonic somatic mesodermal core D. bushy appearance E. cytotrophoblastic core

E. cytotrophoblastic core All chorionic villi possess an outer layer of syncytiotrophoblast. The cytotrophoblast shell is a feature of the mature chorion. Extraembryonic somatic mesoderm forms the core of secondary villi, becoming tertiary with vascular development. Primary villi, at 14 days, are syncytial processes with a core of cytotrophoblast.

Haploid nuclei that fuse at fertilization are called: A. homunculi B. mitotic figures C. centrioles D. nucleoli E. pronuclei

E. pronuclei After the sperm reaches the ovum, it deposits its genetic load, the male pronucleus, into the cytoplasm of the egg. After finally completing the meiotic division that had begun years before, the female pronucleus fuses with the male pronucleus to create the diploid nucleus of the zygote.

The luteal phase is characterized by the presence of ? a. corpus luteum b. primordial follicle c. corpus albicans d. secondary follicles

a. corpus luteum When a mature egg is ovulated (released from the follicle), the remaining follicle becomes vascularized (supplied with blood), and become yellow. The space that the ovum was previously previously present becomes solidified and is now called the corpus luteum.

2. What represents the # of copies of each unique dsDNA molecule in the nucleus?' a. "N" number b. Aneuploid c. Euploid d. Ploidy

a. "N" number

Without fertilization the oocyte usually degernates how many day(s) after ovulation? a. 1 day b. 7 days c. 9 days d. 14 days

a. 1 day (24 hours)

During meiosis when does a cell become haploid? a. During its first meiotic division. b. During its second meiotic division c. After fertilization

a. During its first meiotic division.

Where do the primordial cells come from? a. Epiblast b. Hypoblast c. Mesoderm d. Ectoderm

a. Epiblast

Starting at the onset of puberty the ovary alternates between what two phases? a. Follicular phase and Luteal phase b. Follicular phase and primordial phase c. Luteal phase and FSH phase d. Primordial phase and LH phase

a. Follicular phase and Luteal phase

What hormone is needed for release of the oocyte during ovulation? a. LH b. FSH c. Progesterone d. Estrogen

a. LH

What hormone is responsible for follicular eruption and ovulation? a. LH b. Progesterone c. estrogen d. FSH

a. LH

What hormones causes the primary oocyte to finish meiosis I? a. LH b. FSH c. GnRH d. Estrogen

a. LH

Which cycle is a complex of cyclic changes involving the ovaries, the uterine endometrium, the cervix, the vagina, and the mammary glands? a. Menstrual cycle b. Ovarian cycle c. Uterine cycle d. FSH cycle

a. Menstrual cycle

Progesterone with estrogens stimulate the uterine mucosa to go into the ______ phase in preparation for implantation of the embryo if fertilization occurs? a. Secretory (Progestational) b. Luteinization c. Ovulation d. Estrogenization

a. Secretory (Progestational)

Any chromosome number not euploid (trisomy or monosomy)? a. aneuploid b. nondisjunction c. anaploidy d. noploidy

a. aneuploid

If fertilization does not occur, the corpus luteum reaches maximum development at 9 days. After the corpus luteum shrink from the degeneration of the lutein cells it results in massive fibrotic scar tissue, called the ______. a. corpus albicans (white) b. corpus fibrosus c. theca interna d. granulosa cells

a. corpus albicans (white)

Fusion of the two haploid gametes results in the ______ number of chromosomes? a. diploid (46) b. aneuploid c. euploid d. haploid (23)

a. diploid

In a developing embryo, neural crest cells form adjacent to the neural tube. These neural crest cells then undergo migration. Which of the following structures is derived from these migrating cells? a. Dorsal root ganglion b. Dura mater c. Epidermis covering the back d. Intervertebral disk e. Paravertebral muscle f. Sclerotomes

a. dorsal root ganglion Neural crest develops lateral to the notochord, and neural crest cells migrate widely. They give rise to ganglia and to a variety of neuroendocrine cells in various organs.

Inner cells of the morula constitute the inner cell mass, and surrounding the cells compose the outer cell mass. This inner cell mass gives rise to tissues of the _____, and the outer cells mass forms the ________. Which later contribute to the placenta. a. embryo proper; trophoblast b. trophoblast, embryo proper c. hypoblast; trophoblast d. trophoblast; hypoblast

a. embryo proper; trophoblast

At what stage is the sex of the fetus determined? a. fertilization b. in the sperm prior to fertilization c. 18 weeks d. 20 weeks

a. fertilization

What organ controls the menstrual cycle? a. hypothalmus b. thyroid c. adrenal gland d. posterior lobe of pituitary gland

a. hypothalmus

What is the female maturation from primitive germ cell to mature gamete, which begins before birth? a. oogenesis b. spermatogenesis c. gametogenesis d. mitosis

a. oogenesis

What is it called when the granulosa cells increase in number and become cuboidal? a. primary follicle b. oogonia c. primary oocyte d. seconday follicle

a. primary follicle

The loss of the _________ allows for implantation to begin? a. zona pellucida b. corona radiata c. morula d. blastocele

a. zona pellucida

What two cavities form during the second week of development?

amniotic and yolk sac

How many cells are formed after the completion of meiosis I? a. 1 b. 2 c. 4 d. 8

b. 2 daughter cells Forms the secondary oocyte and the polar body (little cytoplasm).

What is the average length of the ovarian cycle? a. 14 days b. 28 days c. 30 days d. 7 days

b. 28 days

What marks the start of the menstrual phase? a. Uterine cycle b. Ovarian cycle c. FSH cycle d. LH cycle

b. Ovarian cycle

What happens when the primordial cells reach the gonads? a. They become secondary follicles. b. They become oogonia. c. They become primary gonadocytes. d. They become primary follicles.

b. They become oogonia

What occurs after the sperm binds to the zona pellucida? a. zona reaction b. acrosome reaction c. capacitation d. progestation

b. acrosome reaction

Which phase begins at the end of the menstrual phase, and is under the influence of estrogen, and parallels growth of the ovarian follicles? a. menstrual phase b. follicular (proliferate phase) c. secretory phase d. progestational phase

b. follicular (proliferative phase)

An ovum is fertilized. After 3 weeks a blastocyst implanted on the endometrium has an inner embryoblast and an outer trophoblast. Which of the following is the next step in forming a 3-layered embryonic disk? a. Decidualization b. Gastrulation c. Lateralizaton d. Neurulation e. Placentation

b. gastrulation The 3 germ layers form in the process of gastrulation in the 3rd week of embryonic development.

What organ controls the production of GnRH? a. pituitary gland b. hypothalamus c.thyroid d. adrenal gland

b. hypothalamus The hypothalamus produces GnRH which stimulate the anterior lobe of the pituitary glad toe secrete gonadotropins (LH and FSH).

The secondary oocyte present in the follicle enters into meoisis II in what phase? a. anaphase b. metaphase c. telophase d. prophase

b. metaphase Arrests in metaphase about 3 hours before ovulation. When the egg is released it is the secondary oocyte and it is in metaphase of meioisis II.

What is the duration of the luteal phase? a. 3 days b. 7 days c. 14 days c. 21 days d. 28 days

c. 14 days The luteal phase stays constant at 14 days. The follicular phase can vary depending on the length of the cycle.

If a woman had a 48 day cycle, when would ovulation occur? a. 7 days b. 14 days c. 34 days d. 24 days

c. 34 days

Progesterone is stimulated by LH via follicular stromal cells in a process called? a. Proliferation b. Ovulation c. Luteinization d. Progestational phase

c. Luteinization

What cycle is divided into the three phases: Menstrual, Proliferative, and Secretory. a. Menstrual cycle b. Ovarian cycle c. Uterine cycle d. FSH cycle

c. Uterine cycle

A secondary oocyte is developing normally. At which of the following times does the second maturation division of meiosis become completed? a. in the ovarian cortex b. during ovulation c. at fertilization d. in the blastocyst e. upon implantation

c. at fertilization When the sperm penetrates the ovum, the process of meiosis is completed, with expulsion of the last polar body.

What stage of meiosis occurs after a spermatozoon has entered the oocyte? a. meiosis I b. meiosis II metaphase c. completion of second meiotic division d. start of second meiotic division

c. completion of second meiotic division (fertilization) One of the daughter cells, which receives hardly any cytoplasm, is known as the second polar body; the other daughter cell is the definitive oocyte. Its chromosomes (22 plus X) arrange themselves in a vesicular nucleus known as the female pronucleus.

What stage of meiotic division would a primary oocyte following prophase or in the resting state be called? a. primary resting phase b. metaphase c. diplotene stage d. fertilization

c. diplotene stage

As soon as the spermatozoon has entered the oocyte, the oocyte membrane becomes impenetrable to other spermatozoa and the zona pellucida alters its structure and composition to prevent sperm binding and penetration. These reactions prevent ______ from occurring? a. zona reaction b. cortical reaction c. polyspermy d. production of a female pronucleus

c. polyspermy Penetration of more than one spermatozoon into the oocyte is known as polyspermy.

A primary follicle becomes a ________ after fluid filled vesicles develop among the granulosa cells. a. primordial follicle b. primary oocyte c. secondary follicle d. oogonia

c. secondary follicle

Following ovulation and fertilization of an ovum, a blastocyst develops. Growth and differentiation occurs following implantation. Which of the following will develop into the placenta? a. neural plate b. yolk sac c. trophoblast d. sclerotome e. epimere

c. trophoblast Early in development, cells in the blastocyst destined to become the placenta become trophoblasts that line a blastocystic cavity, with an inner cell mass composed of embryoblasts destined to become the fetus. Hence, the placenta is a fetal structure, not a maternal structure.

Head of the sperm enlarges and becomes the male pronucleus, due to replication of its DNA. The tail degernates and the male and female pronuclei fuse to form the? a. dinuclei b. definitive oocyte c. zygote d. gonadozote

c. zygote

What cavity surrounds the primitive yolk sac and amniotic cavity except for the yolk sac?

chorionic cavity

What hormone is needed for the primary follicle to become the secondary follicle? a. Progesterone b. LH c. estrogen d. FSH

d. FSH FSH rescues primary follicles from dying off. 15-20 primary follicles will become secondary follicles at the start of each ovarian cycle. Only 1 of the 15 to 20 primary follicles will reach full maturity and will release during ovulation. The remaining follicles will degenerate and die.

What phase is marked by the presence of maturing follicles? a. Luteal phase b. LH surge c. FSH phase d. Follicular phase

d. Follicular phase

What term refers to the # of copies of each chromosome in cell nucleus? a. "N" number b. Aneuploid c. Euploid d. Ploidy

d. Ploidy

A primordial follicle is characterized by the presence of? a. Oogonia. b. A secondary oocyst getting rid of its polar body. c. An increase in FSH. d. Primary Oocyte and surrounded by a single layer of squamous granulosa cells.

d. Primary Oocyte and surrounded by a single layer of squamous granulosa cells.

When does oogenesis occur? a. 1 month after birth b. six months after birth c. at pubery d. before birth

d. before birth Females already have germ cells in gonads at birth.

Morula enter the uterine cavity and fluid will begin to penetrate through the zona pellucida, into the intercellular spaces of the inner cell mass ,forming a single cavity called the blastocele. At this time the embryo is known as a ______? a. embryoblast b. trophoblast c. embryocyst d. blastocyst

d. blastocyst

When the zygote has reached the two-cell stage, it undergoes a series of mitotic divisions, increasing the number of cells. These cells, which become smaller with each cleavage division, are know as ? a. morula b. embryo proper c. trohpblast d. blastomeres

d. blastomeres

What hormone is responsible for allows the uterine endometrium to enter the follicular or proliferative phase and causes thinning of cervical mucus? a. progesterone b. FSH c. LH d. estrogen

d. estrogen

Any exact multiple of N (diploid or triploid)? a. aneuploid b. trisomy c. polypluidy d. euploid

d. euploid

What is the process in which germ cells undergo to complete maturation which includes meiosis and cytodifferentiation? a. mitosis b. zygogenesis c. gonadotrophogenesis d. gametogenesis

d. gametogenesis

What hormone inhibits degeneration of the corpus luteum after implantation, which is secreted by the synctiotrophoblast of the developing embryo? a. FSH b. LH c. Estrogen d. human chorionic gonadotropin (hCG)

d. human chorionic gonadotropin (hCG)

What is the term when a male gamete and female gamete unite? a. sperm b. oocyte c. oocyte d. zygote

d. zygote

What phase begins 2 to 3 days after ovulation in response to progesterone produced by the corpus luteum? a. menstrual phase b. follicular (proliferative phase) c. secretory phase d. progestational phase e. both c. and d.

e. c. and d. Secretory phase and progestational phase

Cells that remain in the epiblast and do not invaginate become what layer?

ectoderm

_______________ circulation begins to form when the syncytiotrophoblast starts to acquire lacunas.

utero-placental