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Biology 212 Anatomy


Your baby will naturally try to find your breast and ... Lungs bud off from digestive system and grow ... your pubic bones tightens up again; will take ... – PowerPoint PPT presentation

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Title: Biology 212 Anatomy

Biology 212Anatomy PhysiologyHuman
  • Dr. Thompson

One of the best ways to understand the structure
of the adult human body is to understand how it
developed. Similarly abnormalities during
development produce abnormalities
in adult structure.
Assuming You paired up with an appropriate
partner You elicited normal sexual responses from
each other A few milliliters of semen,
containing 200- to 600-million sperm, were
deposited high in the vagina, just below the
cervix of the uterus
Scenario I The woman is not within a few days
before or after ovulation
  • Her cervix will be plugged with thick mucous,
    so few if any sperm will enter the uterus and
    subsequently the Fallopian tubes.
  • The few sperm which might make it into the
    Fallopian tubes are not pushed distally (toward
    the ampulla)
  • The sperm do not meet an oocyte and die within
    48 hours
  • No fertilization occurs

Scenario 2 The woman has just ovulated, or she
will ovulate within 1 - 2 days.
  • The mucous plug in her cervix will be thin and
    watery sperm can easily penetrate it
  • Most sperm will die in her vagina, but a few
    million (1 - 2) are pulled through the cervix,
    into the uterus, and into the Fallopian tubes
    where they are propelled toward the ampulla
    (100,000 make it this far)
  • Sperm meet the oocyte, and fertilization can

At ovulation, oocyte is surrounded by a thick
membrane called the zona pellucida, and by
follicular cells called the corona radiata
Fimbria surrounding the opening of the Fallopian
tube sweep this structure into the infundibulum
Oocyte is viable for 12 24 hours, so
fertilization must occur within this
time. Fertilization occurs within ampulla of
Fallopian tube
If fertilization does not occur, oocyte will
degenerate and die
A few thousand sperm reach the ampulla of the
Fallopian tube within 30 to 60 minutes after
ejaculation But They are not capable of
fertilizing oocyte
Must undergo processes called capacitation
acrosome reaction which will take 8 to 10 hours
after ejaculation
Prior to ejaculation, membrane around head of
sperm is strong Semen contains chemicals to
prevent weakening Tail is moderately active
After ejaculation, Chemicals in semen diluted /
washed away. Secretions from uterus oviducts
cause membrane to weaken. Movement of tail
Acrosome Reaction
Occurs as sperm make contact with corona radiata
and zona pellucida Requires 15 to 60 minutes
Acrosome swells, becomes leaky, releases
digestive enzymes
(Acrosome swells, becomes leaky, releases
digestive enzymes)
Enzymes digest path through corona radiata and
zona pellucida Hundreds of sperm usually
involved in this digestion
Head of one sperm makes contact with outside of
oocyte, binds onto it, and is quickly taken into
Two systems prevent entry of more than one sperm
Fast block Plasma membrane of oocyte changes
its electrical charge, which prevents other sperm
from binding onto it.
Slow block Zona pellucida swells, pushing other
sperm away from the oocyte.
Once head of sperm enters oocyte, its nucleus is
released into the cytoplasm. Nucleus of sperm (23
chromosomes) and nucleus of oocyte (23
chromosomes) meet and fuse together.
Cell now called zygote, with 46 chromosomes
Human Development 3 Periods
Fertilization 2 weeks
2 weeks 8 weeks
8 weeks 38 weeks
Zygote undergoes repeated divisions (mitosis),
called cleavage, as it is transported through
oviduct toward uterus
Eventually forms solid mass of 20 30 cells
called , same size as the zygote.
This reaches uterus 3 to 4 days after
Morula does not embed in uterus
immediately. Stays loosely attached for 4 to 5
days, nourished by secretions of endometrium.
Continues dividing into 100 cells, forming
hollow sphere called . Fluid-filled cavity in
Blastocyst develops mass of cells at one end,
which will develop into the embryo.
Cells surrounding cavity, called
, will develop into the placenta.
Cells of trophoblast secrete digestive enzyme
s, forming finger-like projections into of uterus.
As trophoblast is causing implantation and
developing into placenta, Embryoblast is
enlarging and developing into embryo
Embryoblast (12 14 days after
Pre-embryonic period now over, Embryonic period
During next six weeks of embryonic period, cells
of embryoblast will differentiate into beginnings
of all organs.
Fertilization 2 wks Pre-embryo
2 wks 8 wks Embryonic period
8 wks birth Fetal period
First Cells of embryonic disk separate into
two, and then three germ layers Endoderm
- nearest the blastocyst cavity
(changes name to yolk
sac) Mesoderm - in middle
Ectoderm - nearest amniotic cavity
View From Top, Showing Ectoderm
View From Edge (Cross-section) Showing All Three
As embryo develops Endoderm will form
epithelial linings of digestive and
respiratory systems. Mesoderm
will form skeletal, muscular, urinary,
reproductive, circulatory
systems, as well
as muscle and connective
tissue layers of digestive and
respiratory systems
. Ectoderm will form skin and nervous system
The first system to begin developing is the
nervous system. This appears as a groove along
the ectoderm, which closes over to form a neural
The neural tube
Day 22 23, sides of flat embryonic disk
begin to fold toward
yolk sac. By day 28 Embryo has normal body
shape, amniotic cavity pulled
around to surround it.
Placenta continues to develop from trophoblast
many blood vessels develop within it
Embryo floating in amniotic fluid stays attached
to placenta
Day 28 Arm buds and leg buds begin
Bones, muscles, and blood vessels develop from
mesoderm as limbs get bigger, nerves grow out
from spinal cord.
Other organs continue developing internally.
Length 4mm (width of pencil)
Late embryonic period (4 8 weeks)
Nervous system continues to develop brain
rapidly enlarges and folds
Eyes and ears begin to develop
Limbs continue developing, fingers and toes
Digestive system forms
Lungs bud off from digestive system and grow
Heart folds, divides into chambers, begins
Kidneys, bladder, gonads develop
Face develops as two halves on side of head
move to front and fuse
End of embryonic period
(8 weeks)
Beginning of fetal period
  • Body has human shape
  • Almost all organs have begun developing
  • Head growth still most pronounced
  • Limbs complete
  • Length 3 centimeters
  • Mass 1 2 grams

Mass of quarter 5.7 grams
Placenta well developed
Fetal heart pumps blood from embryo to placenta
through umbilical arteries
Low in oxygen
High in carbon dioxide other wastes
In placenta
Carbon dioxide wastes
Oxygen nutrients
Blood flows from placenta back to embryo through
umbilical veins
High in oxygen nutrients
Low in carbon dioxide other wastes
Ninth week
(Organs and systems continue development) Fetus
5 cm long, 4 - 5 grams External genitalia
develop, but male and female still very similar
penis / clitoris scrotum / labia
Tenth week
(Organs and systems continue development) Fetus
7 cm long, 8 - 10 grams External genitalia
easily determined to be male or female
After tenth week
(Organs and systems continue to develop) Fetus
increases rapidly in size
After 17 weeks (four months)
Skin formed, but thin. Blood vessels easily seen
through it Hair starting to develop. Fingernails
and toenails forming. Eyelids still fused
shut. Ovaries form primordial follicles. May suck
thumb. Moves arms, legs, head Mother can feel
(No Transcript)
After 26 weeks (six months)
Hair present over entire body. Will become
longer on scalp Eyebrows and eyelashes
forming Eyelids almost open Lungs producing
surfactant Testes begin descent through inguinal
canal Swallowing amniotic fluid Movement of
hands, feet, face
After 34 weeks (eight months)
Skin pink, smooth Longer hair on head Eyes open,
respond to light Fingernails and toenails have
reached ends of fingers and toes Testes have
reached scrotum Fingers can grasp objects, fine
movement of face and eyes
Nine months
Ready for birth
Congratulations! You have just given vaginal
birth to a healthy baby.She has been inspected
all parts are where they are supposed to be.
Plus, she is hungry! Your pituitary gland has
been producing a lot of the hormone prolactin,
which has caused your breasts to enlarge and
develop many glands to produce milk. Your baby
will naturally try to find your breast and begin
to suck on it.
This stimulates your pituitary gland to secrete
the hormone oxytocin, which causes muscle cells
in the ducts of the milk glands to force the milk
toward the nipple, where it is expressed through
15-20 openings.
First few days Milk is thick, high in fat,
protein, minerals, antibodies.Called colostrum

Later 90 water 7 sugar
Also includes proteins, fats, vitamins,
Your uterus continues to contract for a few days
to expel functional layer of endometrium.
Assisted when nursing stimulates oxytocin.These
contractions also cause your uterus to begin
returning to its normal, nonpregnant shape and
size will take a few weeksJoint between your
pubic bones tightens up again will take couple
of weeks.
Baby, of course, started breathing as soon as she
was born.
With each breath, more microscopic air sacs
(alveoli) in her lungs open up Within few
minutes adequate to support her need for
Complete opening of all alveoli couple of days.
Two openings in / near heart had allowed blood to
bypass lungs.These two openings now close, so
blood flows through lungs to pick up oxygen and
get rid of carbon dioxide. Will take couple
of days.
(Adjustments of the newborn)
Right after birth Her temperature dropped by a
couple of degrees.Within few minutes able to
generate heat to regulate body temperature.
(Adjustments of the newborn)
Few days Stub of umbilical cord will dry up and
fall off, leaving the umbilicus (belly button)
as a scar.
First 12 to 15 months called Infancy.Period of
rapid growth notably nervous, circulatory,
skeletal, muscle systems
Learning gross motor coordination Legs become
strong enough to bear weight walking begins to
develop Visual acuity develops Learns to
recognize patterns of vison, hearing Verbal
expression and comprehension increase rapidly
speech begins to develop Lungs heart strong
enough to support active movement
Childhood end of infancy until puberty begins.
Less rapid growth Continued improvement in
function of most systems, particularly nervous
and muscular Significant increase in cognitive
function verbal expression and comprehension
fine motor skills
Interestingly very few other species have
extended childhoods Evolved to allow for this
cognitive development
Pubescent period lasts through puberty.Caused
when pituitary begins secretion of follicle
stimulating hormone and luteinizing hormone.
Rapid skeletal and muscular growth again. Hips
and shoulders widen proportionately
more Ovaries, uterus, oviducts, vagina,
testicles, prostate, seminal vesicles begin
adult functions
Pubescent period lasts through puberty.Caused
when pituitary begins secretion of follicle
stimulating hormone and luteinizing hormone.
Rapid skeletal and muscular growth again. Hips
and shoulders widen proportionately
more Ovaries, uterus, oviducts, vagina,
testicles, prostate, seminal vesicles begin
adult functions
Secondary sexual characteristics develop
Enlargement of clitoris/penis, labia/scrotum
Growth of pubic, anal, and axillary (armpit)
hair Specialized sweat glands begin
functioning Breasts develop in both girls
and boys (gynecomastia) Voice changes occur
Hair coursens over most of body
Cognitive function and verbal skills increase
quickly Emotional changes common.
Typical sequence of events in puberty
Age Female Male
10 Increase in height and fat deposition. Breast development begins. Spermatogenesis begins. Interstitial cells appear secrete testosterone
11 Breast development continues. Pelvis widens. Pubic hair appears. Growth spurt begins. Increased fat deposition. Testes begin to enlarge
12 Ovaries, oviducts, uterus, vagina, clitorus, labia mature. Pubic hair more apparent. Menstruation begins. Epididymis, prostate, vas deferens, seminal vesicles, penis, scrotum mature. Pubic hair appears.
13 Breasts fuller. Axillary hair appears. Regular ovulation and menstruation. Pubic hair more apparent. Frequent erections and nocturnal emissions.
14 Skeletal growth slows. Breasts complete. Sebaceous (oil) and sweat glands increase. Acne common. Growth of larynx deepens voice. Axillary and facial hair appear. Shoulders begin to widen.
15 Voice deepens slightly. Regular menstrual periods. Ejaculations fully fertile. Moderate breast development.
16 Adult stature reached. Chest hair appears. Continued muscle skeletal growth. Sebaceous (oil) and sweat glands increase. Acne common.
17 Adult stature reached.
Average age of puberty has decreased in past
1900 14.2 years in girls 1920 13.8
years 1940 13.4 years 1960 12.8 years 1980
12.6 years 2000 11.6 years 2011 10.8 years
Strangely Few people seems to be following this
type of information in boys, but it also appears
to be declining.
Factors influencing decreasing age of puberty
a) Better general health and growth b)
Better nutrition More fat and protein in diet
c) Increase periods of light
Interestingly Body weight at beginning of
puberty has remained relatively constant in girls
at about 47 kg (104 pounds), assuming body fat of
at least 18. No such correlation between
weight and puberty appears to exist in boys.
Adolescent period lasts three to four years after
Bone and muscle mass continue to increase in
both sexes, but more pronounced in males. Fat
deposition continues to increase in both sexes,
but more pronounced in women. Mental maturity
increases Emotions typically stabilize.
Adult period Very little growth or
neural development occur. Fat
deposition continues in both sexes.
Reproduction and child-rearing typically
occur in this period. Decreased
function and diseases of many organs
(e.g. cancers, heart disease,
respiratory disease) common. Gradual loss
of verbal skills, visual and auditory acuity
Adult period Very little growth or
neural development occur. Fat
deposition continues in both sexes.
Reproduction and child-rearing typically
occur in this period. Decreased
function and diseases of many organs
(e.g. cancers, heart disease,
respiratory disease) common. Gradual loss
of verbal skills, visual and auditory acuity
Senescence (old age) involves deterioration and
loss of function of most organs. Bone and
muscle mass lost. Mental and verbal skills