Exam 1 9/20 Davenport Flashcards
Why an interest or need for studying human development?
- we don’t stop growing until about age 25
- we’ll be seeing children as dentists
Human development is a _____ process
Continuous
What are some cellular events that occur during human development?
- fertilization of an ovum
- cell division
- cell migration
- programed cell death
- differentiation
- growth
- cell rearrangement
Why does a newborn baby have a slightly diminished chin?
- Mandible is depressed due to fetal position, head is pressed against chest
- Flat bones have not approximated yet, head is slightly malleable
- Allows baby to pass through birth canal more easily
Orthognathic surgery can help improve:
Severe cases of small/depressed chin in adults
Two major developmental periods
Prenatal, postnatal
Prenatal development period consists of:
- embryonic (weeks 1-8)
- fetal (weeks 8-end)
Birth is a _____ event during development resulting in ______
dramatic; a change of environment
Embryonic stage phases
- fertilization
- Morphogenesis (differentiation of all major internal and external structures)
Development results from _____ in the chromosomes
Genetic plans (inherited from parents, represents mix of genes from family tree)
Cells that are more differentiated have less:
incentive to divide
Which cell type is the least likely to divide?
Neural, cardiac cells (which are replaced by scar tissue)
Postnatal developmental periods
- infancy
- childhood
- puberty
- adolescence
- adulthood
Between fertilization and week 4 involves what cellular events?
cellular proliferation, migration, some differentiation of cell populations
True or false: during embryonic stage, few congenital defects result
True - if severe, embryo is lost
Weeks 4-8
Morphogenesis
Morphogenesis
differentiation of all major internal and external structures
What stage of development is extremely vulnerable to teratogens/defects?
Morphogenesis (during embryonic stage)
Prenatal development is divided into ____ successive stages, which are:
3; fertilization to week 4, morphogenesis, fetal
Fetal stage is mainly:
growth and maturation
By week _, we have everything in place to have a face and teeth
8
Embryonic development is essentially:
mitosis and increasing complexity (morphogenesis and differentiation) of structure and function
Developmental potential becomes more ____ as tissues acquire the specialized features necessary for increasing their sophistication of structure and function
Restrictive
Tooth development constitutes interaction between what tissues?
Epithelial/mesenchymal interaction
Name some of our cell types that undergo high turnover rate
Skin cells (we shed our skin), high fibrous diet can increase turnover in the gut tube, cells in the oral cavity (we brush our teeth twice a day)
Patterning
the developmental process by which cells acquire different identities, depending on their relative spatial positions within the embryo; involves induction, competence, differentiation
Induction
The agent that provides cells with the signal to enter differentiation into different populations of cells
Cells must be ___ to respond to the induction signal
Competent
Competence
ability to respond to an inducer
True or false: Windows of competence stay the same in various populations of cells
False - they vary (some cells may not respond to induction signal)
Differentiation
the process of responding to an inducer to change to what it is supposed to be
Name the players of induction/competence/differentiation
- homeobox genes
- growth factors
- retinoic acid
- other miscellaneous regulatory molecules
Paracrine regulation
a growth factor produced by one cell acts on another
Autocrine regulation
A cell recaptures its own product (needs to go to its own membrane receptor)
Possible results from inductive influence
- cell death
- survive
- proliferate (may even reduce proliferation)
- differentiate
Gametogenesis
Process of forming the gametes (egg and sperm)
Fertilization
fusion of male and female gametes to form the zygote
Meiosis
Reduction cell division that takes place in germ cells
Diploid germ cells develop haploid gametes through:
spermatogenesis and oogenesis
Which division of Meiosis involves reduction division?
Division 1
How many viable cells can be used in oogonia?
1 - ovum needs all the extra cytoplasm to survive 1 week after fertilization, extra chromosomes are discarded via polar bodies
Gametogenesis in males produces:
4 sperm
Why is meiosis important?
- maintains constancy of the chromosome number
- results in a random assortment of genetic material
- relocates segments of maternal and paternal chromosomes between gametes
True or false: mixture of maternal and paternal chromosomes is about 50%
False - can be mixtures of varying degrees, is also a mixture of genes from preceding family tree
When does spermatogenesis begin in males?
At puberty (13-16); continues into old age
When does oogenesis begin in females?
Begins before birth in the female, completed after puberty (12-15), continues to menopause
Cluster of cells found around the primary oocye
Follicular cells
Antrum
Central cavity surrounding secondary oocyte, filled with fluid
____ ____ ultimately becomes the fertilized ovum/oocyte
Secondary oocyte
During ovulation, what happens to the secondary oocyte?
Moves closer to the wall of the ovary, gets expelled into the peritoneal cavity
Disturbances of meiosis during gametogenesis result in the formation of:
abnormal gametes
True or false: abnormal gametes can be compatible with life
True, but some are not (although one example is downs syndrome)
___ ___ refers to the way the oocyte and sperms meet each other in the ampulla of the uterine tube
Gamete transportation
Usual site of fertilization
Ampulla of uterine tube
Three parts of the fallopian tube
Infundibulum, ampulla, isthmus
How does the oocyte get into the uterus?
- Secondary oocyte migrates toward wall of ovary and bursts through, expels some antral fluid
- expelled into the ampulla of the uterine tube via fimbriae of the infundibulum
- transported by peristalsis toward the uterus
If there is not enough force generated to push the oocyte into the uterine tube:
risk of ectopic pregnancy
_____ sperms are deposited around the ____ of the uterus and the ____ of the vagina during intercourse
200-600 million; external os; fornix
How long does the secondary oocyte viable for in the uterine tube?
24 hours
How many sperm make the trip to the uterine tube?
200-300
Describe how sperm move through/what they do in the cervical canal
- Pass slowly through cervical canal using their tails
- vesiculase coagulates some semen to form a vaginal plug
What happens to cervical mucus after ejaculation?
Amount increases and becomes less viscous, allowing easier movements of sperms
Ejaculate volume averages:
3.5 mL (can be 2-6)
How fast do sperms move?
2-3mm/minute depending on pH of environment
Where does capacitation begin in sperm?
In the cervical/1st part of the uterine cavity or uterine tube
Capacitation is important because:
it allows sperm to become mobile
How long does it take for capacitation to occur?
7 hours
Capacitation occurs in response to
enzymes and other components in the uterine fluid
True or false: peristalsis assists sperm movement
True
Corona radiata comes from:
follicular cells
What happens during capacitation?
- Glycoprotein coat and seminal proteins are removed from the acrosome
- membrane components are extensively altered
Intact acrosome binds to ___ of the oocyte
ZP3 glycoprotein (zona pellucida)
What is released during acrosome reaction?
Hyaluronidase, acrosin
Human oocytes are usually fertilized within ____ of ovulation
12 hours
Fertilization must occur within:
1 day of ovulation
True or false: most human sperms probably do not survive more than 48 hours in the female genital tract
True (also some reports of 3-7 days)
Short term storage and release of sperms aids in:
probability of fertilization - storage in cervical mucosa
Longest and widest part of the uterine tube
Ampulla
How long does it take sperm to reach the ampulla?
5-45 minutes
What happens if the oocyte is not fertilized?
degenerates and is resorbed
Phases of fertilization
- Passage of sperm through corona radiata
- penetration of zona pellucida
- fusion of plasma membranes of oocyte and sperm
- completion of meiosis II of oocyte and formation of female pronucleus
- formation of male pronucleus
- chromosomes line up on the metaphase plate, pronuclei fuse into zygote
Results of fertilization
- stimulated the penetrated oocyte to complete the 2nd meiotic division
- restores the normal diploid chromosome number (46)
- responsible for species variation
- determines sex of new individual
- initiates cleavage
