study guide

Allantois

What small outpocketing of embryonic tissues forms at the caudal end of the yolk sac and contributes to the structural base of the umbilical cord?

hypoblast

What forms the roof of primary yolk sac?

Aorta

Through what vessel does blood leave the left ventricle? →

Amniotic fluid

What fluid surrounds and protects the embryo within the amnion? →

Blastocyst cavity

What is the internal cavity that appears in the hollow ball of cells about 4 days after fertilization? →

Blastocyst

What is the conceptus called when the inner cell mass will develop into the embryo and extraembryonic membranes? →

Blastomeres

What are the embryonic cells that become smaller with each cleavage division? →

Bilayer embryonic disc

What structure forms when the inner cell mass organizes into two cell layers during implantation? →

Body stalk

What connects the embryo to the placenta before the umbilical cord develops? →

Cell theory

What biological theory states that cells come from preexisting cells? →

Chorion

What membrane forms the wall of the chorionic sac? →

Chorionic cavity

What is the new name for the extraembryonic coelom? →

Chorionic villi

What fingerlike projections extend from the chorion during the third week of development? →

Chorion frondosum

What is the rapidly growing chorionic villi region at the implantation pole called? →

Chorion laeve

What is the chorionic region where villi decrease in number called? →

Cleavage

What process consists of repeated mitotic divisions of the zygote producing increasing numbers of cells? →

Conceptus

What term refers to the developing offspring (embryo or fetus) during pregnancy? →

Dilation stage

What stage of labor begins with true labor contractions and cervical dilation? →

Diploid

What term describes cells containing 46 chromosomes? →

Embryonic disc

What structure lies between the amniotic cavity and the primary yolk sac? →

Embryonic period

What developmental period lasts from fertilization through week 8? →

Ectoderm

What germ layer forms from cells remaining in the epiblast? →

Endoderm

What germ layer forms when epiblast cells displace the hypoblast? →

Epiblast

What superficial cell layer forms the floor of the amniotic cavity? →

Expulsion stage

What stage of labor occurs when the cervix is fully dilated and the fetus passes through the birth canal? →

Extraembryonic membranes

What membranes form during the first 2–3 weeks and include the yolk sac, amnion, chorion, and allantois? →

Extraembryonic mesoderm

What connective tissue layer surrounds the amnion and yolk sac? →

Decidua basalis

What part of the endometrium is in contact with the placenta? →

Decidua capsularis

What part of the endometrium isolates the embryo from the uterine cavity? →

Decidua parietalis

What is the endometrium on the wall opposite the embryo called? →

Ductus venosus, foramen ovale, and ductus arteriosus

What three vascular structures are most important in fetal transitional circulation? →

Fertilization

What process joins the haploid nuclei of sperm and ovum to form a diploid zygote? →

Fetal period

What developmental period extends from week 9 through birth? →

First trimester

During which trimester do embryonic cell layers that become organ systems develop? →

Foregut

What embryonic structure develops into the pharyngeal arches and contributes to the respiratory and upper GI tract linings? →

Gametes

What are reproductive cells such as eggs and sperm called? →

Gastrulation

What process during week 3 converts the bilaminar embryonic disc into a trilaminar embryonic disc? →

Gastrula

What is the embryo called during gastrulation? →

Germ layers

What three primary layers arise through gastrulation? →

Ectoderm, mesoderm, and endoderm

What are the three germ layers? →

Gestation

What term refers to the nine-month prenatal developmental period divided into trimesters? →

Haploid

What type of cell contains only one chromosome from each homologous pair? →

Head and tail fold

What folds are present by the end of the fourth week of development? →

Heart tube

What structure forms when paired endocardial tubes fuse during the third week? →

Hindgut

What embryonic structure develops into the distal colon, sigmoid colon, rectum, urinary bladder, and most of the urethra? →

Hypoblast

What deep layer of small cuboidal cells faces the blastocyst cavity and forms the roof of the primary yolk sac? →

Implantation

What process begins on day 6 or 7 when the blastocyst contacts the uterine endometrium? →

Implanted embryo

What embryo has a trophoblast that burrows into the endometrium and differentiates into two layers? →

Inner cell mass

What group of internal morula cells gives rise to the embryo and is also called the embryoblast? →

Germinal cells

What reproductive cells residing in the gonads undergo meiosis? →

Meiosis

What process consists of two divisions that produce haploid cells from a diploid germinal cell? →

Mesenchyme

What tissue of loosely arranged cells suspended in a gelatinous matrix forms as cells leave the surface at the primitive streak? →

Midgut

What embryonic structure develops into the epithelial lining of the small intestine and proximal large intestine? →

Mitosis

What process produces daughter cells with chromosomes identical to the parent cell? →

Morphogenesis

What term describes all the processes involved in cell specialization and migration to form anatomical structures? →

Morula

What solid ball of 16 or more blastomeres is formed during early development? →

Neurulation

What is the first major event in organogenesis involving differentiation of ectoderm into the brain and spinal cord? →

Neural tube

What structure forms when the neural plate invaginates and pinches off? →

Forebrain, midbrain, and hindbrain

Into what three primary vesicles does the neural tube develop? →

Notochord

What rod of mesodermal cells forms beneath the primitive streak? →

Optic vesicles

What structures are the primordia of the retinae and optic nerves? →

Organogenesis

What developmental stage involves the formation of body organs and organ systems? →

Ovulation

What process occurs when the ovary releases an egg into the uterine tube? →

Parturition

What term refers to birth involving uterine contractions that expel the fetus? →

Placental stage

During what stage is the placenta detached from the endometrium and delivered as the afterbirth? →

Polar body

What smaller cell produced during meiosis I may continue development and undergo meiosis II? →

Portal vein

What vein joins the right umbilical branch on the right side of the liver? →

Pronucleus

What is each set of nuclear material in the sperm and egg called before fusion? →

Primitive gut

What internal cavity forms when the three embryonic layers fold? →

primitive gut

The three layers of the embryo folds forming an internal cavity called ?

Primitive streak

What region forms when epiblast cells move toward the median plane of the blastodisc? →

Second trimester

Which trimester is characterized by growth in length, mass gain, and the appearance of functional organ systems? →

Somatic cells

What body cells (all except reproductive cells) divide by mitosis? →

Somites

What paired cuboidal bodies develop from paraxial mesoderm? →

Syncytiotrophoblast

What trophoblast layer consists of a multinucleated cytoplasmic mass with no visible cell boundaries? →

Third trimester

Which trimester is characterized by continued growth and maturation of organ systems for function at birth? →

Trophoblast

What outer layer of cells burrows into the uterine lining and forms the embryonic part of the placenta? →

Umbilical arteries

What vessels transport deoxygenated blood from the embryo to the placenta? →

Umbilical cord

What structure links the embryo to the placenta and is formed by the body stalk and yolk stalk? →

Umbilical vein

What vessel returns oxygenated, nutrient-rich blood from the placenta to the embryo? →

Uterine cavity

What cavity has walls composed of the endometrium and myometrium? →

Yolk stalk

What structure attaches the yolk sac to the endoderm of the embryo? →

Zona pellucida

What glycoprotein-rich layer surrounds the ovulated egg? →

Zygote

What cell is formed by the fusion of male and female gametes? →

Mesenchyme

What tissue consists of loosely arranged cells suspended in a gelatinous matrix? →

Midgut

What embryonic structure develops into the epithelial lining of the small intestine and proximal large intestine? →

Mitosis

What process produces daughter cells genetically identical to the parent cell? →

Morphogenesis

What developmental process includes cell specialization and migration to form body structures? →

Morula

What embryonic structure is composed of 16 or more nearly identical blastomeres? →

Neurulation

What is the first major event of organogenesis? →

Neural tube

What embryonic structure ultimately develops into the brain and spinal cord? →

Forebrain, midbrain, and hindbrain

What are the three primary brain vesicles formed from the neural tube? →

Optic vesicles

What are the primordia of the retina and optic nerves? →

Organogenesis

What stage of development involves formation of organs and organ systems? →

Corona radiata

What layer surrounds the ovulated egg in addition to the zona pellucida? →

endoderm

What structure becomes the mucosal lining of the gastrointestinal and respiratory tracts? →

Foregut, midgut, and hindgut

Into what three regions is the primitive gut divided? →

Somites

What embryonic structure develops into sclerotomes, myotomes, and dermatomes? →

Syncytiotrophoblast

What trophoblast layer establishes the diffusional link with maternal blood? →

Umbilical arteries

What vessels carry deoxygenated blood from the fetus to the placenta? →