Transcript Growth and Development

Growth and
Development
ST 120
Objectives
• Discuss the concept of development
as a biological process
• Discuss the major developmental
changes characteristic of the
prenatal stage
• Discuss the three stages of labor
Objectives
• Identify the three primary germ layers
and several derivatives in the adult body
• List and discuss the major developmental
changes of the four postnatal periods of
life
• Discuss the effects of aging on the organ
systems
Growth and Development
• Prenatal period: begins at conception
and ends at birth
• Postnatal period: the period after
birth
Prenatal Period
• Embryology: the science of the
development of the individual before birth
• Describes the means by which a new human
life is started and the steps by which a
single microscopic cell is transformed into
a human being
Fertilization to
Implantation
• Uterine tubes are divided into three
segments / cornea, middle, fimbriae
• Fertilization most often occurs in the
outer one third of the oviduct
• The zygote is genetically complete
• The zygote almost immediately begins
mitotic division and in about 3 days is a
solid mass of cells called a morula
Fertilization to
Implantation
• The cells of the morula continue to
divide, and by the time the
developing embryo reaches the
uterus, it is a hollow ball of cells
called a blastocyst
Fertilization to
Implantation
• It takes about ten days from the
time of fertilization to the time when
the blastocyst is completely
implanted in the uterine lining
No nutrients are available from the
mother during these 10 days
Fertilization to
Implantation
• The blastocyst cosists of an outer
layer of cell and an inner cell mass
• As the blastocyst develops, it forms
a structure with two cavities, the
yolk sac and amniotic cavity
Fertilization to
Implantation
• The yolk sac in humans does not
provide nutrition, instead, it
functions to produce blood cells
• The amniotic cavity becomes a fluidfilled, shock absorbing sac in which
the embryo floats during
development
Fertilization to
Implantation
• The chorion develops into the
placenta
• The chorionic villi connect the blood
vessels of the chorion to the
placenta
Fertilization to
Implantation
• The placenta anchors the developing
fetus to the uterus for the exchange
of nutrients and waste products
• This barrier may be penetrated by
some toxic substances
Periods of Development
• Gestation is divided into three 3month segments called trimesters
• During the 1st trimester, the zygote
develops into the morula and then the
blastocyst
Periods of Development
• The embryonic phase extends from
the 3rd week after fertilization until
the end of the 8th week of gestation
• The fetal phase is used to describe
the 9th week to week 39. During this
period, the term embryo is replaced
by fetus
Periods of Development
• By day 35, the heart is beating, and
the eyes and limb buds are visible
• The end of the third trimester
results in the completion of the
limbs, facial features are apparent,
and gender can be identified
Formation of the Primary
Germ Layers
• Three layers of specialized cells
develop early in the first trimester
called the primary germ layers
– Endoderm
– Mesoderm
– Ectoderm
Endoderm
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Lining of GI tract
Lining of lungs
Lining of hepatic and pancreatic ducts
Kidney ducts and bladder
Anterior pituitary
Thymus gland
Thyroid gland
Parathyroid gland
Tonsils
Adrenal medulla
Mesoderm
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Dermis of skin
Circulatory system
Many glands
Kidneys
Gonads
Muscle
Bones (except facial)
Ectoderm
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Epidermis
Tooth enamel
Lens and cornea of eye
Outer ear
Nasal cavity
Facial bones
Skeletal muscles of head
Brain and spinal cord
Sensory neurons
Histogenesis
• The process of how the primary germ
layers develop into many different
kinds of tissues
Organogenesis
• The way the tissues arrange
themselves into organs
Birth Defects
• Developmental problems present at birth
• May be structural or functional
• May be caused by genetic factors or
exposure to environmental factors called
teratogens. Ex: x-rays, chemicals, drugs,
cigarettes, alcohol, and infections like
herpes or rubella
Birth Defects
• The 1st trimester is a period when
the tissues are beginning to
differentiate and the organs are just
starting to develop, so the effect of
teratogens are most likely to cause
damage
Parturition
• The point of transition between the
prenatal and postnatal periods of life
• Process usually begins when the fetus
takes a head-down position against
the cervix
Stages of Labor
• Three stages
– Stage one: period from onset of uterine
contractions until dilation of the cervix is
complete
– Stage two: period from the time of maximal
cervical dilation until the baby exits through
the vagina
– Stage three: process of expulsion of the
placenta
End of Day 1
Questions???????
Postnatal Period
• Begins at birth and lasts until death
• Growth and development occur
gradually throughout life
The Human Head….
• The infant head is approximately ¼
the total height of the body
• The adult head is about 1/8 the total
height
How Big is Your Face?
• The infant face is 1/8 of the skull
surface
• The adult face is ½ of the skull
surface
Postnatal Periods
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Infancy
Childhood
Adolescence and adulthood
Older adulthood
Infancy
• Lasts about 18 months
• 1st 4 weeks are referred to as neonatal
period
• Newborn must become totally selfsupporting after being fully dependent on
the mother
• Rapid development of the nervous and
muscular systems
Childhood
• The end of infancy to puberty
• Overall, growth is rapid, but monthto-month gains are less consistent
• Deciduous teeth, which appear at ~6
months, are lost at ~ 6 years
Childhood
• Becomes less chubby
• Potbelly gets flatter
• Development of numerous motor and
coordination skills
Adolescence
• Generally considered to be the
teenage years
• Rapid and intense physical growth
• Developmental changes are controlled
by sex hormones and are classified as
secondary sex characteristics
Adulthood
• Completion of developmental changes
• Bone maturation, full closure of
growth plates, changes in the size
and placement of body components
• Balding patterns may become
apparent
• Maintenance of existing body tissues
Older Adulthood
• Gradual, but certain decline in the
functioning of every major organ
system
• Senescence: older adulthood
Effects of Aging
• Skeletal System
– Bones undergo changes in texture,
degree of calcification, and shape
– Shaggy appearance called lipping
– Cervical and thoracic vertebrae are
frequent sites of fractures
– Degenerative joint diseases such as
osteoarthritis are common
Effects of Aging
• Skin
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Dry
Thin
Inelastic
Increased wrinkles and skinfolds
Pigmentation changes
Thinning and loss of hair
Effects of Aging
• Urinary System
– Nephron units decrease by almost 50%
– Reduction in overall function and
excretory capacity or the ability to
produce urine
– Diminished muscle tone of bladder
Effects of Aging
• Respiratory System
– Costal cartilage becomes hardened or
calcified
– Chest movements become difficult
– Loss of muscle cells decreases the
strength of the muscles associated with
inspiration and expiration
Effects of Aging
• Cardiovascular System
– Degenerative heart and blood vessel
disease
– Atherosclerosis: fatty deposits build up
in the walls of blood vessels
– Arteriosclerosis: actual hardening of
the arteries
– Hypertension: high blood pressure
Effects of Aging
• Special Senses
– All show a gradual decline in
performance and capacity
– Most are farsighted
– Presbyopia: hardening of the lens so it
cannot become curved to accommodate
for near vision
Effects of Aging
• Special Senses
– Cataract: lens becomes cloudy
– Glaucoma: increased pressure in the eye
– Loss of hair cells in the Organ of Corti cause a
decline in the ability to hear certain
frequencies
– Eardrum and ossicles may become fixed
– Sense of taste decreases
– Taste buds replaced with connective tissue
End of Day 2
Questions??????