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Biology 2220 Chapter 4 Anatomy Northwestern State University
Chapter Four @ NSU Shreveport Dr.Darvish
48
Biology
Undergraduate 1
09/24/2009

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Term
What happens in Sperm migration?
Definition
A typical ejaculation contains 300 million sperm
Vaginal acid & Failling to get to the uterus & sperm gets destoryed by leukocytes in the uterus

Less than .001% reaches the general vicinity of the egg.
Term
What happens in Sperm Capacitation?
Definition
Removal of cholesterol from sperm membrane & it becomes more permeable to Ca++ which diffuse into the sperm, which stimulate tail movement & the anterior tip of the sperm contains specialized lysosome called ACROSOME.
Term
Acrosomal Reaction is also known as a
Definition
Packet of Enzyme
Term
Acrosomal Reaction
Definition
happens when the sperm contacts an egg, the acrosome undergoes exocytosis.
Term
Where is the Acrosome found?
Definition
The anterior tip of the sperm.. it is a specialized lysosome.
Term
Fertilization happens when?
Definition
Sperm contacts the eggs plasma membrane, the sperm and egg membranes fuse. & nucleus and mid piece of the sperm enters the egg.
Term
What is polyspermy?
Definition
If two or more sperm enter the egg this will result in polyspermy.
Term
what is the fertilization membrane only function? and describe the 2 different types of blocks..
Definition
Blocks the possibility of polyspermy. There is a Fast Block which uses ( 50 times the amount of Na [sodium] on outside of cell) Na+ channels on the egg open allowing the sodium to come in, changes the membrane and results in the inhibition of any more sperm binding to the egg. and the slow block Ca++ inflow, Ca++ stimulates cortical reaction vesicles called cortical granules to secrete proteins, which swells with water pushing all the remaining sperms away.
Term
what is the 1st zygote division called
Definition
Amphimxis
Term
Prenatal Development - how many Trimesters
Definition
3 trimesters.. the first one is the first 12 weeks
the second is weeks 13-24 and the third is from week 25-birth
Term
What does the first trimester consist of?
Definition
Extends from fertilization through the first month of fetal life. More than half of all embryos die in first trimester. Stress, Drugs, and Nutritional deficiencies
Term
What does the 2nd trimester consist of?
Definition
Most organ development completed. Sonography is used to see anatomical detail in the fetus. Infants born at the end of second trimester have a chance of survival.
Term
What does the 3rd trimester consist of?
Definition
Organs achieve enough cellular differentiation to support life outside the womb. Brain, liver and kidneys require further differentiation after birth. 5.5 lb. or 2.5kg after 35 weeks considered mature.
Term
Biological standpoints ( there are 3)
Definition
Pre-embryonic stage
Embryonic Stage
Fetal Stage
Term
Pre-embryonic stage ( 3 parts )
Definition
Cleavage
Implantation
Embryogenesis
Term
Pre-embryonic stage - CLEAVAGE-
Definition
Consists of mitotic divisions that occur in the first 3 days after fertilization. Smaller cells are called blastomeres. At 16 blastomeres the zygote is called Morula. After Morula divided into 100 cells it becomes a hollow sphere called blastocyst with an internal cavity called Blastocoel. The wall of blastocyst has a layer of squamous cells called trophoblast.
Term
What does the trophoblast form?
Definition
a part of the placenta
Term
Embryoblast are blastomeres destined to become the _____ itself
Definition
embryo
Term
Implantation takes about how long to complete?
Definition
a week (pg 110)
Term
Implantation consists of
Definition
Blastocyst attaches to the endometrium. Trophoblast becomes syncytiotrophoblast and cytotrophoblast
Term
Syncytiotrophoblast is a
Definition
multinucleated mass of cells
Term
Syncytiotrophoblast cells grow into the uterus like roots digesting ________
Definition
Endometrial cells
Term
The __________ reacts to this digrestion by growing over the trophoblast so the conceptus becaomes completely buried in the endometrial tissue
Definition
endometrium.
Term
what happens in Embryo Genesis
Definition
In gastrulation three different cell layers are formed from blastomeres ( embryoblast). Endoderm is the inner lining of the digestive tract.

extraembryonic mesoderm contributes to the formation of placenta.
Term
In the amniotic cavity the _________ separates from the ________ creating the amniotic cavity
Definition
Embryoblast, Trophoblast
Term
Embryonic stage consists of
Definition
It begins around day 16 and extends to the end of 8 weeks., the placenta is developed, the embro begins recieving nutrition from the placenta. Germ layers differentiate into organs and organ systems. embryonic folding and organogenesis, embryonic membrances, and prenatal nutrition.
Term
Embryonic folding and organogenesis
Definition
Development of nural tube, pharyngeal pouches, somites are major events of this stage. The formation of nural tube is called Neurulation. Ectoderm cells called neural plate appears along the midline of the embryonic disc. Neural plate cells sinks and becomes a neural groove, the edges of the neural groove meet and close this process creates an enclosed channe, the neural tube.
Term
The formation of the neural tube is called
Definition
Neurulation
Term
Developmental disorders of the nervous systems
Definition
Neural tube defects (NTDs)
Spina bifida
Women can significantly reduce the risk of bearing a child with spina bifida by taking Folic acid (it is a B vitamin)
This works only if taken habitually before the egg is fertilized. Folic acids are ineffective if began after a woman already knows she is pregnant.
Term
Microcephaly-
Definition
The face is of normal size but the brain is abnormally small. Profound mental retardation
Term
Anencephaly
Definition
Results in failure of the rostral end of the neural tube to close. Brain tissue degenerates, most of the brain is absent at birth. Generally die within a few hours.
Term
Pharyngeal pouches
Definition
Five pairs of pockets that form in the wall of the future throat of the embryo, separated by pharyngeal arches. They give rise to middle ear cavity, tonsil, thymus, parathyroid glands, and part of thyroid.
Term
Somites -
Definition
Bilaterally paird blocks of mesoderm, represent primitive vertebrate segmentation. Each somite subdivides into three dissues,
Sclerotome, Myotome Dermatome
Term
Somite - Sclerotome,
Definition
it surrounds the neural tube and gives rise to bone tissue of the vertebral column.
Term
Somite - myotome,
Definition
muscles of the trunk
Term
Somite - dermatome
Definition
is the dermis of the skin and the associated subcutaneous tissue.
Term
Embryonic Membranes-
Definition
Amnion - transport sac that develops from Epiblast cells of embryonic disc, completely encloses the embryo and it is penetrated by umbilical cord. Develops symmetrically. Protects the embryo from infection & temperature flucuations, freedom of movement important for mucle development. Important in lung development as the fetus breaths the fluid. Amniotic fluid is formed by filtration of the mothers blood plasma. Fetus urinates into amniotic cavity about once an hour. Amniotic fluid is about 700-1000mL of fluid
Term
Yolk Sac
Definition
arises from hypoblast cells and it produces the first blood cells and the stem cells of gametogenesis
Term
Allantois
Definition
forms the umbilical ford and becomes part of the urinary bladder.
Term
Chorion
Definition
is the outer most membrane, enclosing all the membranes and the embryo. Forms the fetal portion of the placenta
Term
Prenatal Nutrition (fig 4.10)
Definition
Before implantation of the conceptus it absorbs a glycogen(carbohydrate) rich secretion of the uterine glands called uterine milk. as it implants trophoblastic nutrition, Trophoblast digest cells of the endometrium called decidual cells. The decidual cells accumulate a rich store of glycogen, proteins, and lipids which is used by the embryoblast in weeks 1-8 this period is called trophoblastic phase.
Term
Placental Nutrition
Definition
Placenta is a vascular organ attached to uterine wall and connected to fetus by umbilical cord. Begins week 9 until birth, Placental Phase.
Term
Genetic Disorders - Aneuploidy
Definition
is an abnormal number of chromosomes in the zygote. Chromosomal Nondisjunction - is a failure one of the 23 pairs of chromosomes to separate during meiosis
Term
Genetic Disorders - Zygote will have XXX
Definition
Triplo_X syndrome
Triplo X female will be infertile
Intelectual impairments
Term
Genetic Disorders - XXY zygote
Definition
Causing Klinefelter syndrome
male will be sterile
average intelligence
undeveloped testes
enlarged breasts
Term
Y Zygote
Definition
Dies due to lack of genes from the X chromosome
Term
X Zygote
Definition
Female with turner syndrome
3% of fetuses survive to birth
webbed neck and widley spaced nipples
at puberty secondary sex characteristic fail to develop. absent ovary / sterile
Term
Nondisjunction-
Definition
Trisomy 13 patau syndrome
Trisomy 18 edward syndrome
Trisomy 21 - most common - down syndrome
*retarded physical development
relatively flat face and enlarged protruding tongue
mental retardation is common
epicanthal folds at corners of the eys
the chance of having child with downs is 1 in 3000 in women under 30. one in 365 at 35 and 1 in 9 at age of 48
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