1 / 42
❮ prev next ❯
1 / 42
the study of the development of a unicellular zygote into a complete, multicellular organism; in the course of nine months, a unicellular human zygote undergoes cell division, cellular differentiation, and morphogenesis in preparation for life outside teh uterus; much of what is known about mammalian development stems from the study of less complex organisms such as sea urchins and frogs
❮ prev next ❯

terms list

the study of the development of a unicellular zygote into a complete, multicellular organism; in the course of nine months, a unicellular human zygote undergoes cell division, cellular differentiation, and morphogenesis in preparation for life outside teh uterus; much of what is known about mammalian development stems from the study of less complex organisms such as sea urchins and frogs
an egg can be fertilized within 12-24 hours after ovulation; fertilization occurs in the lateral, widest portion of the oviduct when sperm traveling from the vagina encounter an egg; if more than one egg is fertilized, fraternal twins may be conceived
each embryonic development is characterized by a series of rapid mitotic divisions knows as cleavage; these divisions lead to an increase in cell number without a corresponding growth in cell protoplasm (i.e., the total volume of cytoplasm remains constant); thus, cleavage results in progressively smaller cells, with an increasing ratio of nuclear-to-cytoplasmic material; cleavage also increases the surface-to-volum ration of each cell, thereby improving gas and nutrient exchange; this early developmental process consists of a series of very rapid, synchronous mitotic divisions that converts the zygote's single large cell into a solid ball of cells, known as teh morula, then into the blastula
From cleavage to blastula
the first complete cleavage of the zygote occurs approximately 32 hours after fertilization; the second cleavage occrus after 60 hours, and the third cleavage after approximately 72 hours, at which point the eight-celled embryo reaches the uterus; as cell division continues, a solid ball of embryonic cell, known as teh morula, is formed; blastulation begins when teh morula develops a fluid-filled cavity called the blastocoel, which by the fourth day becomes a hollow sphere of cells called the blastula; the blatula is the stage of teh embryo that implants in the uterus
From blastula to gastrula
once implanted in the uterus, cell migrations transform the single-cell layer of the blastula into a three-layered structure called teh gastrula; these three primary germ layers (ectoderm, endoderm, mesoderm) are responsible for the differential development of the tissues, organs, and systems of the body at later stages of growth
the outermost of the three primary germ layers in animal embryos; gives rise to the outer covering and, in some phyla, the nervous system, inner ear, and lense of the eye
the innermost of the three primary germ layers in animal embryos; lines the archeenteron and gives rise to the liver, pancreas, lungs, and the lining of the digestive tract in species that have these structures
the middle primary germ layer in an animal embryo; develops into the notochord, the lining of the coelom, muscle, skeleton, gonads, kidneys, and most of the circulatory system in species that have thses structures
a hollow ball of cells that marks the end of the cleavage stage during early embryonic development in animals
the fluid-filled cavity that forms in the center of a blastula
an embryonic stage in animal development encompassing the formation of three layers: ectoderm, mesoderm, and endoderm
in animal development, a series of cell and tissue movements in which the blastula-stage embryo folds inwards, producing a three-layered embryo, the gastrula
a longitudinal, flexible rod made of tightly packed mesodermal cells that runs along the anterior-posterior axis of a chordate (member of the phylum chordata) in the dorsal part of teh body
Neural tube
a tube of infolded ectodermal cells that runs along the anterior-posterior axis of a vertebrate, just dorsal to the notochord; it will give rise to teh nervous system
Neural crest cells
in vertebrates, groups of cells along the sides of the neural tube where it pinches off from the ectoderm; the cells migrate to various parts of teh embryo and form pigment cells in the skin and parts of the skull, teeth, adrenal glands, and peripheral nervous system
by the end of gastrulation, regions of the germ layers begin to develop into a rudimentary nervous system; this process is known as neurulation; a rod of mesodermal cells, called teh notochord, develops along the longitudinal axis just under the dorsal layer of the ectoderm; the notochord has an inductive effect on the overlying ectoderm, causing it to bend inward and form a groove along the dorsal surface of teh embryo; the dorsal ectoderm folds on either side of the groove; these neural folds grow upwards and finally fuse, forming a closed tube; this is the neural tube, which give rise to the brain and spinal cord (central nervous system); once the neural tube is formed, it detaches from teh seurface ectoderm; the cells at the tip of each neural fold are called neural crest cells; these cells migrate laterally and give rise to many components of the peripheral nervous system, including the sensory ganglia, autonomic ganglia, adrenal medulla, and schwann cells
member of the phylum chordata, aimals that at some point during their development have a notochord; a dorsal, hollow nerve cord; pharyngeal slits or clefts; and a muscular, post-anal tail
Internal development
follows the neurulation process; includes organogenesis, growth, and gametogenesis
the body organs begin to form; in this process, the cells interact, differentiate, change physical shape, proliferate, and migrate
the organs increase in size, which is a continual process from infancy to childhood to adulthood
eggs develop in women and sperm develop in men, which results in the possibility of reproduction occuring
External development
the early development of many animals occurs outside of the mother's body, on land or in water; fish and amphibians lay eggs that are fertilized externally in the water; the embryo develops within the egg, feeding on nutrients stored in the yolk; reptiles, bird, and some mammals (like the duck-billed platypus) develop externally on land; fertillization occurs internally, and the fertilized egg is then laid; eggs provide protection for teh developing embryo; the eggs also include the following embryonic membranes: chorion, allantois, amnion, yolk sac
(membrane of eggs) lines the inside of the shell; it is a moist membrane that permits gas exchance
(membrane of eggs) this sac-like structure is involved in respiration and excretion and contains numerous blood vessels to transport O2, CO2, water, salt, and nitrogenous wastes
(membrane of eggs) this membrane encloses the amniotic fluid; amniotic fluid provides an aqueous environment that protects the developing embryo from shock
Yolk sac
(membrane of eggs) encloses the yolk; blood vessels in the yolk sac transfer food to the developing embryo
Nonplacental internal development
early development within the body of the mother protects the young; certain animals, including marsupials and some tropical fish, develop in the mother without a placenta; without a placenta, exchange of food and oxygen between teh young and the mother is limited; the young may be born very early in development
Placental internal development
the growing fetus receives oxygen directly from its mother through a specialized cirulatory system; this system not only supplies oxygen and nutrients to the fetus but removes carbon dioxide and metabolic wastes as well; the two components of this system are the placentaa and the umbilical cord, which both develop in teh first few weeks after fertilization
a structure in the pregnant uterus for nourishing a vivaparous fetus with the mother's blood supply; formed from the uterine lining and the embryonic membranes
Umbilical cord
The cord that connects the developing embryo or fetus with the placenta and through which run the umbilical arteries and vein. The matrix (the substance) of the umbilical cord is known as Wharton's jelly and is a rich source of stem cells. At birth the umbilical cord measures about 20 inches (50 cm) in length. The cord is clamped and cut after birth and its residual tip forms the umbilicus (bellybutton).
Placenta and Umbilical cord formation
the placenta and the umbilical cord are outgrowths of the four extra-embryonic membranes formed during development: the amnion, chorion, allantois, and yolk sac; the amnion is a thin, tough membrane containing a watery fluid called amniotic fluid; amniotic fluid acts as a shock absorber of external pressure and localized pressure from the uterine contraction during labor; placenta formation begins with the chorion, a membrane that completely surrounds the amnion; a third membrane, the allantois, develops as an outpocketing of the gut; the blood vessels of the allantoid wall enlarge and become the umbilical vessels, which will connect teh fetus to teh developing placenta; the yolk sac, the site of early developmental blood vessels, becomes associated with the umbilical vessels
pregnancy; the state of carrying developing young within the female reproductive tract; human pregnancy is about 9 months (266 days) and can be subdivided into three trimesters
First trimester
during the first weeks, the major organs begin to develop; the heart begins to beat at approximately 22 days, and soon afterwards, the eyes, gonads, limbs, and liver start to form; by five weeks the embryo is 10mm in lenght; by six weeks the embryo has grown to 15mm; the cartilaginous skeleton begins to turn into bone by the seventh week; by the end of eight weeks, most of teh organs have formed, the brain is fairly developed, and the embryo is referred to as a fetus; at teh end of teh third month, the fetus is about 9 cm long
Second trimester
the fetus does a tremendous amount of growing; it begins to move around in teh amniotic fluid; its face appears human, and its toes and fingers elongate; by the end of the sixth month, the fetus is 30-36 cm long
a developing human from the 9th week of gestation until birth; has all the major structures of an adult
Third trimester
the seventh and eighth months are characterized by continued rapid growth and further brain development; during the ninth month, antibodies are transported by highly selective active transport from teh mother to the fetus for protection against foreign matter; the growth rate slows and the fetus become less active, as it has less room to move about
childbirth is accomplished by labor, a series of strong unterine contractions; labor can be divided into three distinct stages; in teh first stage, the cervix thins out and dilates, and the amniotic sac ruptures, releasing tis fluids; during this time, contractions are relatively mild; the second stage is characterized by rapid contractions, resulting in the birth of the baby, followed by the cutting of the umbilical cord; during the final stage, the uterus contracts, expelling the placenta and the umbilical cord
the embryo develops into the adult through the process of maturation, which involves cell division, growth, and differentiation; in some animals, maturation is suspended in a temporary state; for example, arthropods have a pupal stage; mammals develop uninterrupted; differentiation of cells is complete when all organs reach adult form
Ectopic pregnancy
the embryo implants outside the uterus; for example, in the fallopian tube; an embryo cannot be maintained for long outside of teh uterus; it will abort spntaneously, and hemorrhaging will follow
Determinate cleavage
after the intitial cell division the fate of the resulting daughter cells is determined -- they can only develop into specific tissues, not the whole organisms.
Indeterminate cleavage
fter the initial cell division the fate of the resulting daughter cells is not determined -- each has the potent ial to develop into an entire organism. Sometimes this occurs; resulting individuals are genetically identical (in humans, they are called identical twins)
bleeding or the abnormal flow of blood

more from user

MPEP Most Tested Sections

378 items math en

MPEP 600, 700, 800, 1200, 1800, 2100 TOC

178 items en en

Con Law 1 - 2/25 - Boerne

8 items en en

Con Law 1 - 2/4 - Marbury

12 items en en

Con Law 1 - Facts

6 items en en

Leal Questions

68 items en en

Civil Procedure - FRCP - 15

8 items en en

Leal Oral Argument

22 items en en

Civil Procedure - FRCP - 6

12 items en en


Chapter 26 Reproductive System

61 items en en

DAT Biology Developmental Biology

52 items en en

Kaplan Reproductive System

85 items en en

BIOLOGY 4: Vertebrate Embryology

14 items en en



67 items en en

Short Answers Final AP BIO

21 items en en

History 3000 Final Exam

80 items en en

English 11 Vocab Semester 2 List 21-22

60 items en en