Upgrade to remove ads
Only $35.99/year

A&P 2 Chapter 27

Terms in this set (180)

what is gestation?
time a developing embryo and fetus spend in the uterus
- how long it takes for a baby to develop
what is pregnancy?
state of female during gestation
what is development?
process of GRADUAL anatomical and physiological changes
what is part of prenatal development?
embryonic development and fetal development
what is embryonic development?
events occurring in the first 2 months after fertilization
what is embryology?
the study of embryonic development (events occurring in the first 2 months after fertilization)
what is fetal development?
begins at the start of the 9th week and continues until birth
what occurs at fertilization?
an ovum and a sperm from a zygote prepare for cell division
what is fertilization (conception)?
fusion of two haploid gametes (23 chromosomes)
produces zygote with 46 chromosomes
where does fertilization usually occur?
in the uterine tubes, near the junction between the ampulla and isthmus
how long does fertilization take?
usually within a day after ovulation
what is oocyte activiation?
changes in metabolic activity of oocyte leading to Ca2+ release from smooth ER
what are the 3 effects of the rise of Ca2+ in oocyte activation?
- release enzymes to harden zonal pellucida to prevent fertilization by more than one sperm
- completion of meiosis II and formation of second polar body
-activation of enzymes that cause rapid increase in ovum's metabolic rate
what does sperm deliver in oocyte activation?
paternal chromosome to secondary oocyte
what does the second oocyte provide?
all organelles and inclusions, nourishment, and genetic programming to support embryo for 1 week after conception
if 200 million sperm are introduced into the vagina, and 10,000 enter the uterine tub, how many actually reach the isthmus?
fewer than 100
true or false- males with below 20 million sperm/milliliters are functionally sterile?
true - although only one sperm is needed for fertilization, multiple sperm are needed to supply enough acrosomal enzymes to penetrate corona radiata
what is cleavage?
subdivision of the zygote cytoplasm into numerous, progressively smaller blastomeres
what are a group of blastomeres created by cleavage division called?
pre-embryo
how long does cleavage last?
about 7 days - the pre-embryo travels the length of the uterine tube in that time
during day 6 of blastocyst growth what occurs?
cell division rate increased, enlarging blastocyst rapidly
when does cleavage continue until?
the blastocyst implants in the uterine wall
what day does implantation occur on?
day 7
what is implantation?
begins with the attachment of the blastocyst to the uterine endometrium
by day 10 what happens to the blastocyst?
it erodes endometrial lining and becomes enclosed within the endometrium
what are the layers of the blastocyst cell?
trophoblast layer and inner cell mass
what is a trophblast?
outer layer of cells surrounding the blastocyst
what does the trophoblast provide?
nutrients to the developing embryo
what does the trophoblast form later on?
part of the placenta
what is the inner cell mass?
insulated from contact with intrauterine environment
what will the inner cell mass form?
the embryo
how do trophoblast cells divide?
rapidly
what happens on day 9 ?
formation of amniotic cavity
when does the formation of amniotic cavity come about?
on day 9
what is the primary nutrient source for the inner cell mass for the next 2 weeks after day 10?
yolk sac
how does the formation of amniotic cavity form?
fingerlike villi extend away from the trophoblast into the the endometrium around endometrial capillaries
what does the amniotic cavity create?
a channel called lacunae that fills with maternal blood
how are nutrients absorbed on day 9 during the formation of amniotic cavity?
directly by blastodisc cells
during gastrulation what do superficial cells of the blastodisc migrate toward?
a central line known as primitive streak
what do the migrating cells do in gastrulation?
leave the surface and move between the two existing layers
what is the process of migrating called?
gastrulation
what is does gastrulation create?
three embryonic layers called germ layers
what is the end result of gastrulation?
an oval, three-layered sheet called a embryonic disc
what does the embryonic disc form?
the body of the embryo
what do other cells of the blastocyst form form?
extra-embryonic membranes
what are two examples of extra embryonic membranes?
yolk sac and amnion
what are the three germ layers?
ectoderm, endoderm, mesoderm
what is the ectoderm germ layer?
superficial blastodisc cells that did not migrate
what is the endoderm germ layer?
cells facing the yolk sac
what is the mesoderm?
poorly organized layer of migrating cells between other two germ layers
what does the extra embryonic membranes form?
the placenta that supports fetal growth and development
what are the extra embryonic membranes formed by the germ layers?
yolk sac, amnion, allantois, & chorion
what two germ layers make up the yolk sac?
endoderm + mesoderm
what two germ layers make up the amnion?
ectoderm + mesoderm
what two germ layers make up the allantois?
endoderm + mesoderm
what two germ layers make up the chorion?
mesoderm + trophoblast
what does the extra-embryonic membranes support?
embryonic and fetal development
when is the yolk sac visible?
10 days after fertilization
what is the yolk sac?
vascular network collects and distributes nutrients absorbed from the blastocoele
what is the yolk sac an important site for?
blood cell formation
what does the amnion cavity contain?
amniotic fluid
what does the amniotic fluid do?
cushions developing embryo or fetus
what will the base of allantois form?
the urinary bladder
what does the placenta do?
develops and becomes the primary embryo support
what is oxygen and nutrient exchanged for?
carbon dioxide and wastes
when does the formation of chorion, amnion and yolk sac form?
week 2
what occurs during week 3?
embryonic disc bulges into the amniotic cavity at the head fold
when does the embryonic heart start to beat?
week 3
during week 3 what do the mesoderm extensions along the core of trophoblastic villi form?
the chorionic villi
what are the villi contact with in week 3 and what develops within each villus?
maternal tissue and blood vessels are developed within
what forms during week 4?
tail fold, body stalk, & yolk stalk
what is body stalk in week 4?
between embryo and chorion and carries blood to and from the placenta
what is the yolk stalk in week 4?
narrow connection between endoderm and yolk sac
what happens in week 10?
embryo has now become a fetus
how is the fetus connected to the placenta?
by the umbilical cord
what does the umbilical cord contain?
portions of the allantois, blood vessels, and remnants of the yolk stalk
during week 10 what fills the uterine cavity?
amniotic cavity
what do the umbilical arteries do?
carry blood from developing fetus to the placenta
blood is deoxygenated and full of waste products
what does the umbilical vein do?
carries blood from the placenta to fetus
blood contains nutrients and oxygen
what are placental hormones?
synthesized by the syncytiotrophoblast (hormone that makes females more flexible)
what is organogenesis?
the process of organ formation
when does the organ system form?
in the first trimester and become functional in the second and third trimesters
what is developing during week 3?
the central nervous system & neural plate (which will form the brain)
when does the heart start being?
week 4
what does the placenta form?
week 6
what does the embryo float in?
amniotic cavity
what happens to the limbs in week 6?
grow longer
when do skull bones form around the brain?
week 6
when does the second trimester start?
by the end of 4 months
what has formed/occurred in the second trimester?
face and palate
cerebral hemispheres are enlarging
hair follicles are present, and hair is growing
peripheral nerves are formed
what weeks are the most rapid for fetal growth?
first 8 weeks
what happens in the third trimester?
organ systems become ready for normal function
what are dizygotic twins and how do they develop?
fraternal twins and develop when two separate oocytes are ovulated and fertilized
what are monozygotic twins and how do they develop?
identical twins and result from separation of blastomeres early in cleavage
- can also result when inner cell mass splits before gastrulation
what is the genetic makeup like for monozygotic twins?
identical (both formed from the same set of gametes)
what are some strains on maternal systems?
mother has to absorb enough oxygen, nutrients and vitamins for herself and the fetus
- she must also eliminate all wastes generated
what is a physical strain that happens to women during pregnancy?
increasing size of uterus and fetus pushes maternal abdominal organs out of normal position
true or false- pregnant women over the age of 35 are twice as likely to die from pregnancy-related complications as from an automobile accident
true
what is labor?
spontaneous contractions of the smooth muscle in the uterine myometrium
what causes a gradual increase rate of contractions?
stretching of the uterus
what inhibits contractions during early pregnancy?
progesterone from the placenta
what are braxton hicks contractions?
(false labor) - spasms in the uterine muscles that are neither regular nor persistent
what is true labor?
involves placental and fetal factors for initiation
what are the three stages of labor?
dilation, expulsion & placental stage
what is the goal of labor?
parturition (childbirth) - the forcible expulsion of the fetus and placenta
what is the dilation stage of labor?
begins with the onset of true labor
cervix dilates and fetus shifts toward the cervical canal, moved by gravity and uterine contractions
how long does the dilation stage last for?
8 or more hours
how long do contractions at the beginning of the dilation stage occur?
last up to 30 seconds and occur once every 10-30 minutes
- the frequency and duration of contractions will increase
what ruptures late in the dilation stage?
amnion - "having your water break"
what is the expulsion stage of labor?
begins as the cervix completes dilation and is pushed open by the fetus
when do contractions reach maximum intensity?
in the expulsion stage
how long can contractions last in the expulsion stage?
last up to a full minute and occur 2-3 minutes apart
how long does the expulsion stage last?
continues until the fetus has emerged from the vagina
- usually last less than 2 hours
what does delivery mean?
the arrival of the newborn outside the mother's body
what is the placental stage?
uterine contractions continue
size of the uterus gradually decreases
contraction tear the connection between the endometrium & the placenta
the placenta is ejected
during the placenta stage what helps restrict blood loss?
continued contractions that are compressing the uterine blood vessels
what is premature labor?
occurs when true labor begins before normal fetal development is completed
what are the survival chances related to in premature labors?
directly related to body weight at birth
what is considered to be a premature delivery?
birth at 28-36 weeks (birth weight over 2.2 lb)
true or false- with care, premature newborns have a good chance of surviving and developing normally?
true
what is the neonatal period?
first 28 days of life
- developmental processes continue
- dependent on mother for nourishment, transportation and protection
what is milk production?
by the end of the 6th month of pregnancy, mammary glands are full developed and secreting colostrum
what does colostrum contain?
antibodies to help fight infection until newborn's immune system develops
when do mammary glands start producing breast milk?
few days into nursing
what does the mothers milk contain?
much higher fat content than colostrum and contains antibodies and lysozyme (antibiotic enzyme)
what is milk ejection reflex (milk let-down reflex)?
stimulation of tactile receptors (by infant suckling)
neural impulse transmission (to the spinal cord and brain)
what is oxytocin secretion?
by secretory neurons in the paraventricular nucleus of the maternal hypothalamus
what is oxytocin release?
by the posterior lobe of the pituitary gland and is distributed throughout the body by the bloodstream
what is milk ejected?
oxytocin cause contraction of myoepithelial cells in the walls of the lactiferous ducts and sinuses
what are the five stages in postnatal development?
neonatal period, infancy, childhood, adolescence & adulthood
what is growth during early stages coordinated by?
hormones such as growth hormones, steroids, and thyroid hormones
when does the neonatal period begin?
first 28 days
when does infancy occur?
first year
still dependent on mother
what does childhood occur?
weaned from breast milk in early childhood
body proportions gradually change
what does adolescence occur?
begins at puberty (period of sexual maturation)
ends when growth is complete
when does maturity begin?
after maturity, gradual changes continue in the process of senescence or aging
when do many body systems alter their activities in response to changes in levels of sex hormones?
at puberty
what are effects of testosterone and estrogens when enhanced by other hormones?
growth hormone
thyroid hormone
prolactin
adrenocortical hormone
what is inheritance (heredity)?
transfer of genetically determined characteristics from generation to generation
what is genetics?
study of mechanisms responsible for inheritance
what increases the release of GnRH?
hypothalamus
in response to the hypothalamus releasing more GnRH what responds?
anterior pituitary releases LH and FSH
in response to the anterior pituitary releasing LH and FSH, what do the testicular and ovarian cells initiate?
- gamete production
- secretion of sex hormones, which stimulates secondary sex characteristics and behaviors
- sudden acceleration in growth rate, ending with closure of the epiphyseal cartilages
what does genotype mean?
chromosomes and their component genes
the blueprint of someone
what does phenotype mean?
anatomical and physiological characteristics displayed by the collective expression of your genes
- ex: someone hair color
what is epigenetics?
study of gene expression due to alterations in the reading of the DNA sequences
what are karyotype?
entire set of chromosomes
how many pairs of chromosomes does a fully functional human have?
23 pairs
where do each pair of chromosomes come from?
one pair from sperm & the other pair from oocyte
what are the two pairs of chromosomes called together?
homologous chromosomes
what does autosomal chromosomes mean?
22 pairs of chromosomes
affect somatic characteristics - such as eye color
how many pairs of sex chromosomes do we have and what does it determine?
1 pair and determines whether you are male or female
what do females have for their pair of sex chromosomes?
two X chromosomes
what do males have for their pair of sex chromosomes?
one X chromosome and one Y chromosome
what are homologous chromosomes?
chromosomes with homologous pairs have the same structure and carry genes affecting the same traits
true or false- two chromosomes may carry the same or different form (allele) of the gene?
true
what is the most common form of interaction?
simple inheritance
what is strict dominance?
any dominate allele present is expressed in the phenotype regardless of any other allele
when is a recessive allele trait expressed?
only if it is present on both chromosomes of the homologous pair
what is a punnett square?
grid used to predict genetic probabilities
what are dominant alleles represented by in a punnett square?
capital letters
what are recessive alleles represented by in a punnett square?
lower case letters
what does tt mean?
homozygous recessive
what does TT mean?
homozygous dominant
what does Tt mean?
heterozygous
what is polygenic inheritance?
interactions among several genes determine phenotypic characteristics
- cannot be simple punnett square to predict phenotype
- ex: brown or black hair color
what is codominance?
heterozygous individuals (for given trait) exhibit both phenotypes for trait
ex: Type AB blood
what is incomplete dominance?
heterozygous alleles produce phenotype as intermediate to homozygous individuals
what percentage of our genotype is simple inheriance?
about 80%
what are two major patterns of inheritance?
simple inheritance and inheritance involving sex chromosomes
what does simple inheritance involve?
strict dominance, incomplete dominance, and codominance & polygenic inheritance
what is sex-linked inheritence?
involves genes on the sex chromosomes
what are X-linked genes?
genes found on the X chromosome but not the Y chromosome
- ex- gene for red-green color blindness
what are Y-link genes?
genes found on the Y chromosome but not the X chromosome
ex: SRY gene for "maleness"
what are chromosomal abnormalities?
can involve thousands of genes so usually lethal
only a few autosomal chromosomes abnormalities do mot result in prenatal death
what is human genone?
the full set of genetic material (DNA) in our chromosomes
what is Klinefelter syndrome?
male phenotype but reduced androgen production
- testis fail to mature (causing sterility)
- breasts slightly enlarged
- sex chromosome = XXY
what is Turner syndrome?
individual only has a single X chromosome
- maturational changes do not appear at puberty
-ovaries are nonfunctional, with negligible estrogen production
what is trisomy 21 (Down Syndrome)?
most common viable chromosome abnormality
three copies of chromosome 21
causes intellectual disability and physical malformation
(degree of disability ranges from moderate to severe)
(anatomical problems affecting the cardiovascular system are often fatal)
true or false- there is a direct correlation between maternal age and risk of having a child with trisomy 21?
true- it is more risky when women are older and are trying to have children
Other sets by this creator