Chapter 29 - Human Development and Aging Flashcards
The study of prenatal development
Embryology
Examines changes in form and function from fertilized egg through old age
Developmental biology
3 primary germ layers of an embryo
ectoderm, mesoderm, endoderm
an individual becomes an embryo when it is _ days old
16
events leading up to the stage of an embryo
embryogenesis
what stage is the first 16 days after fertilization
pre-embryonic stage
fertilized egg at 16 days old
embryo
the egg must be fertilized within _ - _ _ of ovulation, if it is to survive
12-24 hours
how long after the sperm reaches the uterine tube does it take to fertilize the egg
10 hours
where do the sperm generally meet the egg during ovulation
distal uterine tube
How long are sperm viable for after ejaculation
6 days
when sperm encounters an egg, it undergoes what
acrosomal reaction
exocytosis of the acrosome, releasing enzymes needed to penetrate the egg
acrosomal reaction
what two things do sperm need to clear out of the way for the one sperm to penetrate the egg
granulosa cells and zona pellucida
what are the two acrosomal enzymes
hyaluronidase and acrosin
this digests hyaluronic acid that binds granulosa cells together
hyaluronidase
a protease similar to trypsin
acrosin
combines the haploid set of sperm chromosomes with the haploid set of egg chromosomes producing a diploid set
*must know for test
fertilization
fertilization by two or more sperm which would produce a doomed fertilized egg
polyspermy
two mechanisms to prevent polyspermy
fast block and slow block
binding of sperm to the egg opens na+ channels in egg membrane
fast block
involves secretory vesicles, cortical granules, just below membrane
stimulates cortical reaction, in which cortical granules release secretion beneath zona pellucida
sperm penetration releases an inflow of ca+
slow block
two eggs ovulated and both are fertilized by separate sperm forming two zygotes
implant separately in uterine wall and each have own placenta
no more genetically similar than any other siblings
2/3 of twins
dizygotic twins
one egg is fertilized but embryoblast later divides into 2
genetically identical
monozygotic twins
this begins meiosis II before ovulation but completes it only if fertilized
secondary oocyte
sperm and egg swell and become _______
pronuclei
what is a fertilized egg called
zygote
pregnancy is divided into 3 month intervals called…
trimester
during this trimester conceptus is most vulnerable to stress, drugs and nutritional deficiencies
first trimester
during this trimester organs complete most of their development
fetus looks human
second trimester
during this trimester, fetus grows rapidly and organs achieve enough cellular differentiation to support life
third trimester
the first 16 days of development culminating in the existence of an embryo
pre embryonic stage
the 3 major processes of the pre embryonic stage
cleavage, implantation, embryogenesis
mitotic divisions that occur in first 3 days while conceptus migrates down uterine tube
cleavage
what’s it called when the zygote splits in to two daughter cells
blastomeres
how long does it take for conceptus to arrive in uterus
72 hours after ovulation
a solid ball of 16 cells - resembles mulberry
occurs during cleavage process of pre embryonic stage
morula stage
how long does the morula lie free in the uterine cavity
4-5 days
when the zona pellucida disintegrates and releases conceptus - it’s called…
*know for test
blastocyst
a hollow sphere
*know for test
blastocyst
outer layer of squamous cells
destined to form placenta and nourish the embryo
trophoblast
what is the embryoblast and what does it become
*know for test
the inner cell mass of a blastocyst
it becomes the embryo
*know migration of conceptus photo for test
slide 29-16
during implantation ______ attaches to uterine wall 6 days after ovulation
usually on the fundus or posterior wall of uterus
blastocyst
the process of attachment of blastocyst to uterine wall
implantation
trophoblasts on attachment side separate into ___ layers
2
what are the layers of the trophoblast called once it separates
and where are they located
superficial layer - in contact with endometrium
deep layer - close to embryoblast
What hormone does trophoblast secrete
human chorionic gonadotropin (HCG)
trophoblast develops into membrane called….
chorion
HCG stimulates corpus luteum and it secretes (2) hormones
estrogen and progesterone
arrangement of blastomeres into 3 primary germ layers in embryoblast
embryogenesis
what are the names of the 3 primary germ layers of an embryoblast
ectoderm, mesoderm, endoderm
multiplying epiblast cells migrate medially into primitive groove
gastrulation
gastrulation replaces the original hypoblast with layer called
endoderm
migrating epiblast cells form a 3rd layer btwn first two. this layer is called…
mesoderm
the remaining epiblast layer is called…
ectoderm
this is a more loosely organized tissue which differentiates into a loose fetal connective tissue, called mesenchyme
the mesoderm
this gives rise to muscle, bone, and blood
mesoderm
what is complete once the 3 primary germ layers are formed
embryogenesis
once embryogenesis is complete, an individual is considered a….
embryo
this begins when all 3 primary germ layers are present (usually day 16)
embryonic stage
this is the embryo’s primary source of nutrition. after the first 2 weeks are complete, it forms over the next 6 weeks
the placenta
germ layers differentiate into organs and organ systems
organogenesis
organs are present at how many weeks
at 8 weeks when the embryo becomes a fetus
formation of organs from primary germ layers:
what derivatives from the ectoderm
epidermis, nervous system, lens and cornea, internal ear
formation of organs from primary germ layers:
derivatives of mesoderm
skeleton, muscle, cartilage, blood, lymphoid tissue, gonads and ducts, kidneys and ureters
formation of organs from primary germ layers:
derivatives of endoderm
gut and respirator epithelium and glands, bladder and urethra
what are the accessory organs that develop with embryo
placenta, umbilical cord and 4 embryonic membranes
what are the 4 embryonic membranes
amnion, yolk sac, allantois, and chorion
the transparent sac that develops from epiblast
amnion
arises from hypoblast cells opposite amnion
yolk sac
begins as an outpocketing of yolk sac
forms foundation for umbilical cord
becomes part of urinary bladder
allantois
outermost membrane enclosing all the rest of membranes and embryo
chorion
the shaggy outgrowths of the chorion. are around the entire surface
chorionic villi
know photo on 29-30
during gestation, the conceptus is nourished in 3 different ways. what are the 3 ways
uterine milk, trophoblastic nutrition, placental nutrition
this is the glycogen rich secretion of the uterine tubes and endometrial glands
uterine milk
conceptus consumes decidual cells of endometrium
trophoblastic nutrition
as conceptus burrows into endometrium, ___________ digests these cells and supplies nutrients to embryoblast
syncytiotrophoblast
from the corpus luteum, this stimulates decidual cells to proliferate
progesterone
nutrients diffuse from mother’s blood through placenta into fetal blood
placental nutrition
disc shaped organ attached to uterine wall; attached by way of umbilical cord to fetus
placenta
period beginning week 9
placental phase
by the end of week 8 - what is the embryo like
- all organ systems are present
- considered a fetus
- bones have begun to calcify
- heart has been beating since week 4, now circulates blood
- head is nearly half of total body length
- skeletal muscles have spontaneous contractions
what is the baby called from week 9 - birth
fetus
6-8 hour period immediately following birth when neonate must adapt to life outside mother
transitional period
the first 6 weeks of life
neonatal period
what is considered a premature baby
infants born weighing less than 5.5lbs
infants born before 7 months suffer from (4)
infant respiratory distress syndrome (IRDS)
thermoregulatory
digestive issues
immature liver
what causes infant respiratory distress syndrome
insufficient surfactant which causes alveolar collapse with exhalation
what digestive issues does a premature baby have
small stomach volume, undeveloped sucking and swallowing reflexes
what liver problems do premature babies have
failure to synthesize adequate proteins which results in edema, and clotting deficiency
jaundice
abnormal structures or positions of organs at birth resulting from defect in prenatal development
birth defect or congenital anomalies
what is the study of birth defects
teratology
- these are agents that cause anatomical deformities in the fetus
- they fall into 3 categories - what are the 3 classes
- teratogens
2. drugs and other chemicals, infectious diseases, radiation such as xrays
what is the drug that caused birth defects; was taken by mothers for morning sickness or insomnia
thalidomide
what causes more birth defects than any other drug
alcohol
this is characterized by small head, stunted growth, nervousness, poor attention span, cardiac and central nervous system defects
cause by alcohol
fetal alcohol syndrome
this contributes to fetal and infant mortality, ectopic pregnancy, cleft palate and cardiac anomalies
cigarette smoking
what kinds of microorganisms can cross placenta and cause serious anomalies, stillbirth, neonatal death
viral infections and bacterial infections
- these appear to account for one third of all birth defects
- there are two types - what are they
- genetic anomalies
2. mutations and mutagens
changes in dna structure
mutations
environmental agents cause mutation
mutagens
failure of homologous chromosomes to separate in meiosis; can cause genetic disorder
nondisjunction
the presence of an extra chromosome or lack of one
aneuploidy
lack of a chromosome leaves one without a match
monosomy
the extra chromosome produces a triple set
trisomy
examination of cells in amniotic fluid
amniocentesis
biopsy of cells from chorion
chorionic villi sampling
egg receiving two X chromosomes fertilized by X carrying sperm
-infertile female with mild intellectual impairment
triplo-X syndrome (XXX)
egg receiving two X chromosomes fertilized by Y carrying sperm
-sterile males with average intelligence (undeveloped testes)
klinefelter syndrome (XXY)
egg contains no X chromosome but is fertilized by X carrying sperm
- 97% die before birth
- webbed necks, widely space nipples, sterile, short stature, sexual characteristics fail to develop at puberty
turner syndrome (XO)
what 3 autosomal trisomies are survivable
involve chromosomes 13, 18, 21
trisomy -13
patau syndrome
nearly all die before birth
infants born are severely deformed and less than 5% survive first year
trisomy-18
edward syndrome
nearly all die before birth
infants born are severely deformed, and less than 5% survive 1 year
trisomy - 21
down syndrome - most survivable trisomy
short stature, relatively flat face with flat nasal bridge, low set ears, epicanthal folds at medial corners of eye, stubby fingers
1 in 700-800 live births in US
chance of down syndrome is 1 in 3000 in woman under 30; 1 in 365 in woman over 35; 1 in 9 in woman by 48
all changes occurring in body with passage of time: growth, development, and degenerative changes occur later in life
aging
degeneration occurs in organ systems after age of peak functional efficiency
senescence
what is intrinsic aging of skin
photoaging - degeneration in proportion to UV exposure: skin spots, skin cancer, wrinkling
senescence of the skeletal system
osteopenia - loss of bone mass
osteoporosis - loss is severe enough to affect person’s physical activity and health
senescence of joint diseases
osteoarthritis - common cause of physical disability
synovial fluid less abundant and articular cartilage thinner or absent producing friction that causes pain
senescence of muscular system
muscular atrophy - causes replacement of muscle with fat
senescence of the nervous system
involves cerebral and neuronal atrophy
nervous system reaches peak at 30 years
plaques of fibrillar proteins appear: Alzheimer disease - most common nervous disability of old age
senescence of the endocrine system
degenerates less than any other system
only reproductive, growth and thyroid hormones show major declines
type II diabetes more common
senescence of vison and hearing
vision: cataracts; loss of flexibility of lenses; glaucoma; night vision impaired
hearing: tympanic membrane and ossicle joints stiffen; death of vestibular neurons results in dizziness;
taste and smell are blunted as receptors decline
loss of flexibility of lenses in eye
presbyopia
senescence of the circulatory system
anemia - results from poor nutrition, lack of exercise, diseases, low level of intrinsic factor needed for vitamin B12 absorption and low levels of erythropoietin
coronary atherosclerosis - leads to degeneration of myocardium
varicose veins - due to weaker valves
senescence of immune system
lymphatic tissue and red bone marrow decline with age
lymphocytes fail to mature
both types of immune response are less efficient - less protection from cancer and infectious disease
senescence of the respiratory system
declining pulmonary ventilation
elderly less able to clear lungs of irritants, pathogens
- pneumonia - respiratory infections
chronic obstructive pulmonary diseases (copd):
-emphysema and chronic bronchitis
senescence of urinary system
renal atrophy: 20-40% smaller by age 90 vs 30
fluid balance
voiding and bladder control
senescence of urinary system
renal atrophy: 20-40% smaller by age 90 vs 30
-loss of nephrons; filtration rate decreases
fluid balance
- dehydration common - less responsive to antidiuretics, sense of thirst reduced
voiding and bladder control
-80% men over 80 have benign prostatic hyperplasia
senescence of digestive system
reduced saliva makes teeth more prone to cavities and makes swallowing difficult.
gastric mucus atrophies and secretes less acid and intrinsic factor***
intestinal motility decreased due to weaker muscle tone, less fiber, water and exercise
constipation
reduced food intake due to loss of appetite increases malnutrition
**know for exam
senescence of male reproductive system
gradual decline in testosterone secretion, sperm count and libido
fertile in old age
impotence may occur due to atherosclerosis, hypertension, medication or psychological reasons
senescence of female reproductive system
abrupt changes due to menopause
elevated risk of osteoporosis and atherosclerosis
vaginal dryness, genital atrophy and reduced libido
best ways to slow senescence
good nutrition and exercise
resistance exercise reduces ____ ____
bone fractures
decline in mitotic potential with age
- telomeres
- organ functions depends on cell renewal keeping pace with cell death, but human cells only divide a limited number of times
replicative senescence
ends of the chromosomes that diminish with each division
telomeres
what plays role in senescence
extrinsic (environmental) factors - progressively damage cells over lifetime
heredity
intrinsic process governed by inevitable or even programmed changes in cell function
genetic disorder showing accelerated aging
progeria
- dna suffers thousands of damaging events per day
- most damages are repaired, some persist and accumulate as cells age, especially in nondividing cells
- cumulative damage impairs function
DNA damage theory
- autoimmune diseases become more common with old age
- altered macromolecules may be recognized as foreign
- may stimulate lymphocytes to mount an immune response against bodys own tissues
autoimmune theory
is there a definable instant of biological death
no
- some organs function for an hour after heart stops
- brain death is lack of cerebral activity, reflexes, heartbeat and respiration for 30 min-24 hrs
What is letter A
Cleavage
what is letter B
zygote
What is letter C
Second polar body
what is letter D
morula
what is letter E
Blastocyst
what is letter F
implanted blastocyst
what is letter G
blastomeres
what is H
egg
what is I
sperm
what is J
zona pellucida
what is K
fertilization
what is L
first polar body
what is M
ovary
what is N
Maturing follicle
what is O
corpus luteum
What is P
ovulation
What day of implantation is this
6-7 days
what day of implantation is this
day 8
what germ layer is A
ectoderm
what germ layer is B
mesoderm
what germ layer is C
endoderm
What is letter A
chorionic villlus
what is letter B
placenta
what is letter C
yolk sac
what is letter D
umbilical cord
what is letter E
amniotic fluid
what is letter F
amnion
what is letter G
chorion
what is letter H
lumen of uterus
