Transcript Presentation

Chapter 23
Bio 202
Human Anatomy &
Physiology Part 2
Tim Pimperl
A & P Instructor
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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Important Points in Chapter 23:
Outcomes to be Assessed
23.1: Introduction
 Distinguish between growth and development.
 Distinguish between prenatal and postnatal.
23.2: Conception
 Describe the movement of sperm toward an egg
 Discuss fertilization.
23.3: Pregnancy/Prenatal Period
 List and provide details of the major events of cleavage.
 Describe implantation.
 Discuss the hormonal and other changes in the maternal body during
pregnancy.
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Important Points in Chapter 23:
Outcomes to be Assessed
 Describe the major events of the embryonic stage of development.
Explain how the primary germ layers originate, and list the structures
each layer produces.
Describe the formation and function of the placenta.
 Define fetus, and describe the major events that occur during the fetal
stage of development.
 Trace the path of blood through the fetal cardiovascular system.
 Explain the role of hormones in the birth process and milk production.
23.4: Postnatal Period
 Name the postnatal stages of development of a human, and indicate
the general characteristics of each stage.
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Important Points in Chapter 23:
Outcomes to be Assessed
 Describe the major cardiovascular and physiological adjustments that
occur in a newborn.
23.5: Aging
 Distinguish between active and passive aging.
 Contrast lifespan and life expectancy.
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23.1: Introduction
• A sperm and a secondary oocyte unite, forming a zygote,
and the journey of prenatal development begins
• After 38 weeks of cell division, growth and specialization
into distinctive tissues and organs, a new human being enters
the world
• Humans grow, develop and age
• Growth is an increase in size
• Development, which includes growth, is the continuous
process by which an individual changes from one life
phase to another
• Prenatal period is from fertilization to birth
• Postnatal period is from birth to death
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23.2: Conception
•The union of a secondary oocyte and a sperm cell is called
fertilization, or conception
• Fertilization takes place in a uterine tube
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Transport of Sex Cells
• Before fertilization can occur, a secondary oocyte must be ovulated and
enter a uterine tube
• Only a few hundred of between 200 to 600 million sperm reach a
secondary oocyte
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Path of
Sperm cells
Body of uterus
Infundibulum
Ovary
Sperm cells
Path of
egg cell
Egg cell
Cervix
Vagina
Semen deposited in vagina
during sexual intercourse
From M. Tegner and D. Epel. 16 February 1973. "Sea Urchin Sperm." Science, 179:685-688. © 1973 American
Association for the Advancement of Science
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Fertilization
• Several hundred sperm cells must be present at
the secondary oocyte to release enough enzymes
(from the sperms’ acrosomes) necessary to
penetrate the corona radiata and zona
pellucida that surround the oocyte
• As one sperm nucleus enters, the secondary oocyte
completes meiosis II, producing a tiny polar body
and an egg nucleus
• The sperm nucleus unites with the egg nucleus to
form a zygote
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23.3: Pregancy/Prenatal Period
• Pregnancy is the presence of a developing offspring in the
uterus
• Pregnancy consists of three trimesters, each about three
months long
•The prenatal period usually lasts 38 weeks from conception
• It can be divided into:
• 1. A period of cleavage
• 2. An embryonic stage
• 3. A fetal stage
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Period of Cleavage
• The rapid cell division and distribution of the zygote’s
cytoplasm into progressively smaller cells is cleavage
• The cells produced during cleavage are called
blastomeres
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(a)
(b)
(c)
a: © A. Tsiara/Photo Researchers, Inc.; b: © Omikron/Photo Researchers, Inc.; c: © Petit Format/Nestle/Photo Researchers, Inc.
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Period of Cleavage
• Zygote – fertilized egg
• Morula – solid ball of cells
• Blastocyst – hollow ball of cells that implants in
uterus
• Inner cell mass – gives rise to embryo
• Trophoblast – cells forming wall of blastocyst –
develops into structures that assist
embryo….also produces hCG
• Placenta – vascular structure formed by cells of
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trophoblast and endometrium
Hormonal Changes
During Pregnancy
• Secretion of hCG maintains the corpus luteum (remains of
follicle after ovulation, stays in ovary) and inhibits FSH and
LH
• The corpus luteum secretes estrogens and progesterone
• The placenta secretes large amounts of estrogens and
progesterone
• Estrogens and progesterone stimulate and maintain the
uterine lining, inhibit FSH and LH, inhibit uterine
contractions, and enlarge the reproductive organs
• Relaxin from the corpus luteum inhibits uterine contractions
and relaxes the pelvic ligaments
• Placental lactogen stimulates breast development
• Aldosterone promotes sodium retention
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• PTH maintains calcium concentrations in the blood
Other Changes
During Pregnancy
• Growth of the uterus can displace abdominal
organs and disrupt meals, including the development
of heartburn and increased urinary frequency
• More oxygen is needed and more waste is excreted
causing increases in blood volume, cardiac output,
breathing rate, and urine production
• To obtain adequate nutrition, intake must be
sufficient to supply needed vitamins, minerals and
proteins
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Embryonic Stage
• The embryonic stage extends from the beginning of the second
week through the eighth week, when the placenta forms, the main
internal organs develop, and the major external body structures
appear
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Lumen of
uterus
Endometrium
Chorion
Extraembryonic cavity
Germ layers of
embryonic disc
Ectoderm
Mesoderm
Endoderm
Amnion
Amniotic cavity
Connecting stalk
Chorionic villi
Yolk sac
of embryo
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Embryonic Stage
• Structures which help support and nourish the
embryo:
• Chorion
• Amnion
• Yolk sac
• Placenta
• Umbilical cord
• By the end of the 2nd week, the primordial embryo
has formed three primary germ layers and is
termed a gastrula
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Chorion
• As the amnion
develops, it
surrounds the
embryo, and the
umbilical cord begins
to form from
structures in the
connecting stalk
Umbilical
cord
Allantois
Amnion
Amniotic cavity
Yolk
sac
Extraembryonic
cavity
Maternal
blood
vessels
Developing
placenta
Endometrium
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Amniochorionic membrane
Amniotic fluid
Umbilical cord
Chorion
Endometrium Myometrium
Placenta
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Fetal Stage
• The fetal stage begins at the end of the eighth week of
prenatal development
• Here growth is rapid, and body portions change
considerably
• At the beginning of this stage, the head is disproportionately
large, and the lower limbs are relatively short
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Birth Process
• Pregnancy terminates with the birth process called parturition
• The process is complex as noted in Table 23.5
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Milk Production and Secretion
• During pregnancy, placental estrogens and
progesterone stimulate further development of the
mammary glands, and prolactin is released by the
anterior pituitary
• But milk secretion does not begin until after birth
• The “first milk” is a thin, watery fluid called
colostrum (rich in proteins and antibodies but has
lower amounts of carbohydrates and fats)
• Mature milk is produced within a few days
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23.4: Postnatal Period
• Following birth, both mother and newborn experience
physiological and structural changes
• The postnatal period lasts from birth until death
• It can be divided into:
• The neonatal period
• Infancy
• Childhood
• Adolescence
• Adulthood
• Senescence (including dying)
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Neonatal Period
• Neonatal period
• From birth to the end of the 4th week
• The newborn begins to carry on respiration, obtain
nutrients, digest nutrients, excrete wastes, regulate body
temperature, and make cardiovascular adjustments
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Infancy
• Infancy
• From the end of the 4th week to one year
• The growth rate is high
• The teeth begin to erupt
• The muscular and nervous systems mature
• Communication begins
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Childhood
• Childhood
• From one year to puberty
• The growth rate is high
• Permanent teeth appear
• Muscular control is achieved
• Bladder and bowel controls are established
• Intellectual abilities mature
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Adolescence
• Adolescence
• From puberty to adulthood
• The person becomes reproductively functional and
emotionally more mature
• Growth spurts occur
• Motor skills continue to develop
• Intellectual abilities continue to mature
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Adulthood
• Adulthood
• Adolescence to old age
• The person remains relatively unchanged anatomically
and physiologically
• Degenerative changes begin
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Senescence
• Senescence
• Old age to death
• Degenerative changes continue
• The body becomes less able to cope with the demands
placed on it
• Death results from various conditions and diseases
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The End of Life
• Nearing the end of life is a personal process, influenced by
belief as well as circumstance
• A person who has been chronically ill may show signs of
impending death, often in a sequence
• Two stages of the dying process include:
• Preactive dying which may take up to three months
• Active dying with a distinct set of signs
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23.5: Aging
• The aging process is difficult to analyze
• The medical field of gerontology examines the biological
changes of aging at the molecular, cellular, organismal, and
population levels
• Aging is both active and passive
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Passive Aging
• Aging as a passive process is a breakdown of structures and
slowing of functions
• Molecularly a degeneration of elastin and collagen
proteins
• Biochemically lipids breakdown
• Cellular degradation is associated with free radicals
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Active Aging
• Aging also entails new activities or the appearance of new
substances
• Lipofuscin granules from the breakdown of lipids
• Autoimmunity
• Apoptosis - the process of programmed cell death
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The Human Life Span
• The human life span is approximately 120 years
• Life expectancy is a realistic projection of how long an
individual will live
• The current U.S. life expectancy is 75.4 years for men and
83.2 years for women
• Medical advances contribute to improved life expectancy
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