Transcript Chapter 29 - HCC Learning Web

Anatomy and Physiology, Sixth Edition
Rod R. Seeley
Idaho State University
Trent D. Stephens
Idaho State University
Philip Tate
Phoenix College
Chapter 29
Lecture Outline*
*See PowerPoint Image Slides for all figures and tables pre-inserted into PowerPoint without notes.
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Chapter 29
Development, Growth,
Aging, and Genetics
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Prenatal Development
• From conception to birth
– Three stages
• Germinal period
– First 2 weeks of
development during
formation of primitive
germ layers
• Embryonic period
– 2nd to end of 8th week,
organ systems develop
• Fetal period
– Last 30 weeks, organ
systems grow and mature
• Clinical age
– Mother’s LMP to
calculate age of unborn
child
• Postovulatory age
– Describes timing of
developmental events
– Calculated as 14 days
less than clinical age
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Fertilization
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Early Cell Division
• Zygote divides to form
2 cells about 18-39
• Blastocyst or hollow
hours after fertilization
sphere of cells
– 2 cells divide to form
4, 8, and so on
– Pluripotent: Ability to
develop into wide
range of tissues
• Morula
– Implantation
• Burrowing into uterine
wall
– Placenta develops from
trophoblast cells
– Solid ball of 12 or
more cells
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Early Stages of Development
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Blastocyst
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Formation of Placenta
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Mature Placenta and Fetus
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Formation of Germ Layers
• Amniotic cavity
– After implantation, new cavity forms inside inner mass
and separates
• Embryonic disk composed of ectoderm and endoderm
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Primitive Streak
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• Mesoderm: the middle primary germ layer
that gives rise to connective tissues, blood
and blood vessels, and muscles
• Endoderm: a primary germ layer of the
developing embryo; gives rise to the
gastrointestinal tract, urinary bladder
urethra, and respiratory tract
• Ectoderm: a primary germ layer of the
developing embryo that give rise to the
nervous system, and the epidermis of the
skin and it’s derivatives
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Neural Tube Formation
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Somite Formation and
Gut Formation
• Gut formation
• Somite formation
– As neural tube
develops, segments or
somites form or
indistinct somitomeres
– Eventually become
part of skull, vertebral
column, skeletal
muscle
– Developing digestive
tract pinches off from
yolk sac as a tube but
remain attached by
yolk stalk
• Oropharyngeal
membrane
• Cloacal membrane
– Evaginations
– Celom or body cavity
development
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Formation of Digestive Tract
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Limb Bud Development and
Face Development
• Face development
• Limb bud development
– Arms and legs appear at
about 28 days
– Apical ectodermal ridge
develops on lateral
margin of each limb and
stimulates outgrowth
– Limb tissue laid down in
proximal-to-distal
sequence
– Fusion of 5 embryonic
structures
• Frontonasal process
• Maxillary processes
• Mandibular processes
– Nasal placodes
• Cleft lip
– Failure of frontonasal
and 2 maxillary
processes to fuse
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Face Development
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Organ Systems Development
• Muscle
• Skin
– Epidermis derived
from ectoderm
– Dermis derived form
mesoderm or neural
crest cells as in face
• Skeleton
– Develops from
mesoderm or neural
crest cells
– Myoblasts are early
embryonic cells that
develop into skeletal
muscle fibers
• Nervous System
– Derived from neural
tube and crest cells
• Circulatory System
– Heart develops from 2
endothelial tubes
which fuse
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Heart Development
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Organ Systems Development
• Respiratory system
– Lungs develop as
single midline
evagination from
foregut in region of
future esophagus
• Urinary system
– Kidneys develop from
mesoderm located
between somites and
lateral part of embryo
• Reproductive system
– Male and female
gonads appear as
gonadal ridges
• Primordial germ cells
are destined to become
oocytes or sperm cells
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Lung Development
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Kidney and
Urinary Bladder Development
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Reproductive System
Development
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Fetal Growth
• Fetus
– At 60 days embryo
becomes a fetus
• Fetal period
– From day 60 to birth is
rapid growth
– Lanugo
• Fine soft hair covering
– Vernix caseosa
• Waxy coat of protection
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Parturition
• Parturition
– Process by which a
baby is born
• In mother
– Estrogens overcome
inhibitory influence of
progesterone
– Oxytocin is released
• In fetus
– Adrenal gland is
enlarged prior
• Labor
– First stage
• Onset of regular uterine
contraction until cervix
dilates to fetal head
diameter
– Second stage
• From maximum
cervical dilation until
baby exits vagina
– Third stage
• Expulsion of placenta
from uterus
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Parturition
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Factors Influencing Parturition
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Changes at Birth
• Respiratory System and
Circulatory System
– Foramen ovale closes,
two atria separated
– Ductus arteriosus
closed, blood no longer
flows between
pulmonary trunk and
aorta
– Umbilical vein and
arteries degenerate
• Digestive System
– Meconium (anal
discharge) is mixture of
cells from digestive tract,
amniotic fluid, bile, and
mucus excreted by
newborn
– Stomach begin to secrete
acid
– Liver does not form adult
bilirubin for 1st 2 weeks
– Lactose can be digested,
but other food must be
gradually introduced
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Circulatory Conditions in Fetus
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Circulatory Changes at Birth
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Apgar Scores
• Assessment of newborn baby
– Appearance, pulse, grimace, activity, respiratory effect
– Rated on scale of 0-2, 2 denotes normal function
– Total Apgar score is sum from five characteristics
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Genetics and Chromosomes
• Genetics
– Study of heredity
• DNA
– Hereditary material of
cells and controls cell
activities
– Chromosomes
• Karyotype or display
• Autosomal and sex (X
or Y)
• Contain thousands of
genes
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Inheritance of Sex
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Genes
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Genes
• Functional unit of
heredity
– Portion of DNA
• Types
• Dominant and Recessive
– Dominant masks effects of
recessive genes
• Sex-linked traits
– Structural: Serve as
– Traits affected by genes on
template for mRNA,
sex chromosomes
code for amino acid
• Genotype
sequences
– Actual set of alleles a
– Regulatory: Control
person has for a given trait
which structural genes
transcribed in given
• Phenotype
tissue
– Person’s appearance
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Traits
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Other Types of Gene Expression
• Incomplete dominance
– Dominant gene doesn’t
completely mask effects
of recessive gene
– Sickle-cell disease
• Polygenic traits
– Determined by
expression of multiple
genes on different
chromosomes
– Person’s height, eye and
skin color, intelligence
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Genetic Disorders
• Genetic disorders
– Abnormalities in DNA
• Congenital disorders
– Birth defects not
necessarily genetic
– Teratogens
• Agents that cause birth
defects
• Mutation
– Mutagens
• Agents that cause
mutations
• Cancer
– Tumor resulting from
uncontrolled cell
divisions
– Oncogenes
• Genes associated with
cancer
– Tumor suppressor
genes
– Carcinogens
– Genetic susceptibility
or predisposition
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Genetic Counseling
• Predicting possible
results of matings
involving carriers of
harmful genes
• Talking to prospective
parents about possible
outcomes and
treatments of a genetic
disorder
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Human Genomic Map
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