(LESSON 2) Chapter 3-Embryology Flashcards
Embryology
The study of the origin and development of an individual person.
Prenatal Period
Before Birth. Time from conception to birth. Divided into two stages: Embryonic Period (8 weeks) and Fetal Period (30 weeks).
Oocyte (pg 52)
The egg a woman’s ovary releases each month.
Conception
When a sperm fertilizes an oocyte.
Zygote
The fertilized Oocyte. Moves toward the uterus as it begins to divide repeatedly. 2,4,8…
Blastomeres
The daughter cells of the dividing Zygote.
Cleavage
the early division sequence of the the zygote/blastomeres, providing the large number of cells needed as building blocks for the embryo.
Morula
the cluster of 12-16 blastomeres created approx. 72 hours after fertilization. Still multiplying. At day 4, consisting of about 60 cells, the morula enters the uterus.
Blastocyst
Upon entering the uterus, the structure begins to take up fluid that gathers into a central cavity. Two cell types form. This stage lasts about 3 days-Days 4-7.
Inner cell mass
cluster of cells on one side of the blastocyst cavity. Will form embryo.
Trophoblast
Layer of cells surrounding blastocyst cavity. Will help form the placenta.
Placenta
Structure that transfers nutrients from the mother to the fetus.
Implantation
From day 4 to day 6 the blastocyst is floating freely about the uterus. On day 6 blastocyst begins burrowing into the wall of the uterus. Trophoblast layer begins to erode inward until the entire blastocyst is embedded in the uterine wall. Takes about a week.
Monozygotic Twins (Identical)
From one zygote. When the inner cell mass of a single blastocyst splits into 2 during early stages of cleavage.
Inner cell mass division (pg 53)
Day 9 the inner cell mass divides into 2 sheets of cells. The epiblast and the hypoblast. Extensions of both sheets form fluid filled sacs with epiblast and hypoblast being point of contact.
Bilaminar embryonic disc
together the hypoblast and epiblast make this up..which will give rise to the whole body.
Amniotic Sac
Extension of the epiblast. Outer membrane is called the amnion and the cavity is filled with amniotic fluid which acts as a buffer until birth. (“water just broke” is the rupture of the amniotic sac and release of amniotic fluid near the start of labor)
Yolk Sac
Extension of the hypoblast. Hold very small amount of yolk. Forms part of digestive tube.. Tissue around sac give rise to earliest blood cells and vessels.
Gastrulation
During week 3 the embryo grows from a two layered disc to a three layered disc. Forms three primary germ layers: ectoderm, mesoderm, and endoderm-the layers from which all body tissues develop.
Primitive Streak
On day 14-15, this raised groove appears on the dorsal surface of the epiblast. Epiblast cells migrate inward at this streak.
Endoderm
The first cells that migrate through the primitive streak displace the cells of the underlying hypoblast to become the endoderm. Day 14-15.
Mesoderm
The cells following the endoderm cells through the primitive streak form a new layer between the epiblast and endoderm. Day 16
Ectoderm
The remaining epiblast cells on the embryo’s dorsal surface make this form. All three layers derived from epiblast cells.
Epithelial Tissue
Epithelia. Sheets of tightly joined cells. Endoderm, Ectoderm.
mesenchyme tissue
mesen=middle, chyme=fluid. Cells do not attach to one another but are free to migrate within the embryo. Mesoderm.
Primitive Node
Swelling at one end of Primitive Streak
Notochord
Epiblast cells that move through the primitive node migrate straight anteriorly. These mesodermal cells, along with a few cells from the underlying endoderm, form a rod. This rod defines the body’s axis (left/right). Extends the length of the body and is the site of the future vertebral column. Appears on day 16 and by day 18 reaches the future head region.
Neurulation
As notochord develops it signals overlying ectoderm to begin forming the spinal cord and brain.
Neural Plate
Ectoderm in the dorsal midline thickens.
Neural Groove
Neural plate begins folding inward.
Neural Tube
The neural groove deepens and hollow until tube is pinched off. Complete closure of tube occurs by the end of week four.
Neural Crest
Cells that are pulled into the body along with the cells forming the neural tube. Originates from ectoderm cells on the lateral sides of neural plate. forms the sensory nerve cells.
Induction
The ability of one group of cells to influence the developmental direction of other cells. Ex. Notochord’s influence on the formation of the neural tube.
Paraxial Mesoderm
The mesoderm closest to the notochord.
Somites
The paraxial mesoderm divides into a series of blocks starting cranially and moving caudally. Are visible from surface as sub ectodermal bulges on each side of the back. First body segment to form.
Intermediate Mesoderm
Continuous strip of tissue just lateral to the paraxial mesoderm.
Lateral Plate
The most lateral part of the mesoderm. Splits into two due to a wedge that forms between. The space between is the coelom and the to divisions are the somatic mesoderm and the splanchnic.
Coelum
The space between the somatic and splanchnic mesoderm.
Derivatives of Endoderm
inner epithelial lining and glands of digestive and respiratory tracts.
Derivatives of Notochord
Gives rise to important part of spinal column: the spingy cores of the discs between vertebrae called nucleus pulposus-giving the vertebrae some bounce when we walk.
Derivatives of Ectoderm
Brain, spinal cord, epidermis of the skin (in turn hair, finger/toe nails, sweat/oil glands). Neural crest cells form sensory nerve cells. Wandering neural crest cells form melanocytes (pigment producing cells) and bones of the face.
Derivatives of Somite
Sclerotome, Dermatome, and Myotome.
Sclerotome
Vertebrae and Ribs
Dermatome
dermis of dorsal body region
Myotome
Trunk and limb musculature.
Intermediate Mesoderm
Kidneys, Gonads
Lateral Plate Mesoderm
Somatic, Splanchnic mesoderm
Somatic Mesoderm
Mesoderm next to the Ectoderm. Gives rise to parietal serosa, dermis of ventral body region, connective tissue of limbs(Bones, joints, ligaments)
Splanchnic Mesoderm
Mesoderm next to endoderm. Gives rise to wall of digestive and respiratory tract (except epithelial lining), Visceral Serosa, heart, blood vessels
Premature birth
A birth that occurs before the normal time. Normal births typically occur 38 weeks after conception. Infants born as early as week 30 (7months) usually survive without life saving measures.
Teratology
The study of birth defects—fetuses with congenital deformities (teratos = monster; logos = study of)
Teratogen
A chemical, physical, or biological factor that disrupts normal development.
Accutane
a drug taken for the most severe type of acne called cystic acne; it causes craniofacial defects.
Thalidomide
a sedative taken for morning sickness; the most common defect caused is shortened limbs
Alcohol
causes fetal alcohol syndrome (FAS)
Cigarettes
nicotine in cigarettes constricts uterine blood vessels, which causes a decrease in uterine blood flow. Also, carbon monoxide from the smoke contributes to decreased availability of oxygen to the baby as well as the mother
Cocaine and heroine
drugs that increase the risk of sudden infant death syndrome (SIDS). SIDS is the most common cause of death in infants under one year old
Viruses like Rubella (German Measles)
diseases that can cause congenital heart defects, blindness/cataracts, and deafness.
Fetal Alcohol Sydrome
causes growth and mental retardation, microcephaly (underdeveloped brain), ocular (eye) anomalies, and joint abnormalities.
Spinal Bifida
occurs when the neural tube does not close at the bottom which leaves a portion of the neural tube exposed externally. This condition can be caused by a maternal deficiency in folic acid.
Ancephaly
occurs when the neural tube does not fully develop near the head, so the brain does not form. This condition can also be caused by a maternal deficiency in folic acid.
Downs Syndrome (Trisomy 21)
the presence of an extra chromosome in the genome. Causes mental retardation and distinctive physical characteristics.
PKU
metabolic disorder where the infant is unable to metabolize a crucial amino acid
Heart Defects
there are a wide variety of disorders that occur because of abnormal development of the heart. This is the most common type of birth defect
