Biology Ch 3. Embryogenesis and Development Flashcards
Fertilization
The joining of a sperm and a secondary oocyte where a sperm uses acrosomal enzymes to penetrate the corona radiate and zone pellucida, once the sperm contacts an oocytes plasma membrane, it establishes the acrosomal apparatus and injects its pronucleus
Ampulla
Widest part of the Fallopian tube where fertilization occurs
Cortical reaction
When the first sperm penetrates an ovum it causes a release of calcium ions to prevent additional sperm for fertilizing the egg, it also increases the metabolic rate of the resulting diploid zygote
Acrosomal apparatus
Tubelike structure which extends from the sperm and penetrates the oocyte’s cell membrane
Zygote
Diploid cell created after fertilization, unicellular, besoms embryo after first cleavage
Fraternal twins
Dizyogitc - result from the fertilization of two eggs by two different sperm, each own zygote and placenta, chorion, and amnion, no more genetically similar than any other sibling
Identical twins
Monozygotic - result from the splitting of a zygote in two, can be classified by the placental structure they share (mono vs diamniotic and mono vs dichorionic)
Cleavage
Early divisions of cells in the embryo, result in a larger number of smaller cells as the overall volume does not change, occurs while zygote moves to the uterus for implantation, larger nuclear to cytoplasm ratio and larger SA to vol ratio (good for gas and nutrient exchange)
Embryo
The zygote becomes an embryo after the first cleavage because it is no longer unicellular, becomes morula after multiple more divisions
Indeterminate cleavage
Results in cells that are capable of becoming any cell in the organism
Determinate cleavage
Results in cells that are committed to differentiating into a specific cell type
Morula
Solid mass of cells seen in early development
Blastula
aka blastocyst in mammals - has a blastocoel center and two different structures: the trophoblast and the inner cell mass
Blastocoel
Fluid filled center of a blastula
Trophoblast
Part of a blastula that surrounds the blastocoel, becomes the placental structure/chorion, create interface between the maternal blood supply and developing embryo
Inner cell mass
Part of a blastula that protrudes into the blastocoel, becomes the developing organism
Placenta
Forms when the blastula implants in the endometrial lining, where nutrient, gas, and waste exchange occurs, serves as immure protection against many pathogen, allows for antibodies to be passed from mother to child, serves endocrine functions such as secreting estrogen, progesterone, and human chorionic gonadotropin
Chorion
An extra embryonic membrane that develops into the placenta, contains chorionic cilli
Chorionic villi
Microscopic fingerlike projections that penetrate the endometrium and create the interface between maternal and fetal blood, develop into placenta
Yolk sac
Supports the embryo before the placenta is established, site of early blood cell development
Allantois
Early fluid exchange between the embryo and the yolk sac
Amnion
Thin, tough membrane that surrounds the allantois and is filled with amniotic fluid, outer membrane is the chorion
Umbilical cord
Connects the developing organism to the placenta, consists of two arteries and one vein encased in a gelatinous substance, formed from remnants of the yolk sac and allantois
Gastrulation
Process where the archenteron is formed with a blastopore at the end, the archenteron grows through the blastocoel and contacts the opposite side, which establishes three primary germ layers
Archenteron
When the membrane invaginates into the blastocoel, develops into the gut
Blastopore
The opening of the blastopore, develops into anus in deuterostomes and the mouth in protostomes
Ectoderm
Outermost layer of the gastrula, becomes the epidermis, hair, nails, and the epithelia of the nose, mouth, anal canal, the nervous system, and the lens of the eye
Mesoderm
Becomes much of the musculoskeletal, circulatory, and excretory systems, gives rise to gonads and muscular and connective tissue layers of he digestive and respiratory systems, also the adrenal cortex
Endoderm
Becomes much of the epithelial linings of the respiratory and digestive tracts, also parts of the pancreas, thyroid, bladder, and distal urinary tracts
Neurulation
Development of the nervous system, begins after formation of the three germ layers
Notochord
A rod of mesodermal cells that forms along the long axis of the organism like a primitive spin and induces a group of overlying ectodermal cells to form neural folds surrounding a neural groove
Neural folds
Formed by ectodermal cells overlying the notochord, grow towards each other until they fuse into neural tube, the tip of each fold contains neural crest cells
Neural tube
Formed by the fusing of the neural folds, becomes the central nervous system
Neural crest cells
Present at the tip of each neural fold, becomes the peripheral nervous system and other specific cell types
Teratogens
Substances that interfere with development, causing defects or even death of the developing embryo, include alcohol, drugs, viruses, bacteria, and environmental chemicals
Diabetes in maternal development
Increased fetal size and hypoglycemia after birth
Folic acid deficiency in maternal development
Neural tube defects
Determination
Commitment to a specific cell lineage, which may be accomplished by uneven segregation of cellular material during mitosis or with morphogens, follows specification, irreversible commitment
Morphogens
Molecules that promote neighboring cells to develop down a specific cell line, cell must have competency to respond
Competency
Cell must have it to respond to morphogen
Differentiation
The changes a cell undergoes due to selective transcription to take on characteristics appropriate to its cell line
Selective transcription
Only the genes needed for that particular cell type are transcribed
Stem cells
Capable of developing into various cell types, classified by potency
Stem cell potency classifications
Totipotent, pluripotent, multipotent
Totipotent cells
Stem cells that are able to differential into all cell types, including the three germ layers and placental structures, embryonic stem cells are totipotent
Pluripotent cells
Stem cells that are able to differentiate into all three germ layers and their derivatives, present after cells differentiate into three germ layers
Multipotent cells
Stem cells that are able to differentiate only into a specific subset of cell types
Inducer
Chemical substances that release factors to promote differentiation of a competent responder, diffuse from organizing cells to responsive cells, may also be the cell secreting the signal, often growth factors
Responder
Cell that is induced or influenced by inducers
Autocrine signals
Act on the same cell that released the signal
Paracrine signals
Act on local cells
Juxtacine signals
Act through direct stimulation of adjacent cells
Endocrine signals
Act on distant tissues after traveling through the blood stream
Growth factors
Peptides that promote differentiation and mitosis in certain tissues, usually only function on specific cell types
Reciprocal induction
When two tissues both induce further differentiation on each other
Apoptosis
Programmed cell death via the division of the cell into many apoptotic blebs that can subsequently be absorbed and digested by other cells for recycling of materials, prevents release of harmful substances into extracellular environment, can be used be sculpting certain anatomical structures such as removing the webbing between digits
Regenerative capacity
The ability of an organism to regrow certain parts of the body
Senescence
Biological aging, the result of multiple molecular and metabolic processes such as the shortening of telomeres during cell division
Placenta exchange
Oxygen and carbon dioxide are passively exachanged because of concentration gradients
Fetal hemoglobin
HbF - higher affinity for oxygen than adult hemoglobin, assists in the transfer and retention of oxygen into the fetal circulatory system
Umbilical arteries
Carry deoxygenated blood from the fetus to the placenta
Umbilical vein
Carries oxygenated blood from the placenta back to the fetus
Fetal circulatory shunts
Necessary because fetus lungs and liver underdeveloped and sensitive to high blood pressures so these shunts are created to actively direct blood away from them, foramen ovale, ductus arteriosus, ductus venosus
Foramen ovale
One way valve, connects the right atrium to the left atrium, bypasses the lungs, pressure difference in birth causes this shunt to be shut
Ductus arteriosus
Connects the pulmonary artery to the aorta, bypasses the lungs
Ductus venosus
Connects the umbilical vein to the inferior vena cava, bypasses the liver
First trimester growth
Organogenesis occurs, bones harden, embryo becomes fetus
Organogenesis
Development of the heart, eyes, gonads, limbs, liver, and brain
Second trimester growth
Tremendous growth occurs, movement begins, face becomes distinctly human, digits elongate
Third trimester growth
Rapid growth and brain development continue, transfer of antibodies to the fetus, near the end, growth rate slows and the fetus becomes less active as their is less room
Birth
Cervix thins out and the amniotic sac ruptures, uterine contractions occur with the help of prostaglandins and oxytocin, birth of fetus occurs followed by the placenta and umbilical cord being expelled (afterbirth)
Protaglandins and oxytocin
Cause uterine contractions which result in birth of fetus
Conjoined twins
Division of identical or monozygotic twins is not complete
Blastulation
Forms a blastula from the morula
Umbilical vein
Carries freshly oxygenated blood rich with nutrients from the placenta to the embryo
Umbilical arteries
Carry deoxygenated blood and waste to the placenta from the embryo
Amniotic fluid
Shock absorber during pregnancy
Deuterostomes
-
Protostomes
-
Primary germ layers
Form after membrane invagination and when some cells migrate into the remains of the blastocoel, the ectoderm, mesoderm, and endoderm are formed
Induction
When one group of cells influences the fate of nearby cells, mediated by inducers
Specification
Initial stage of cell specialization in which the cell is reversibly designated as a specific cell type, followed by determination
Apoptotic blebs
Self-contained protrusions that a cell divides into during apoptosis
Apoptotic bodies
Apoptotic blebs that are broken up and can be digested by other cells to recycle materials
Necrosis
Process of cell death in which a cell dies as a result of injury, internal substances can be laded causing irritation of nearby tissues or immune response
Complete regeneration
Lost of damaged tissues are replaced with identical tissues
Incomplete regeneration
Newly formed tissue is not identical in structure or function to the tissue that has been injured or lost
Shunt
Hole or passage that moves fluid from one part of the body to another
Parturition
Vaginal childbirth
