1. Human Anatomy & Physiology Part 2
Chapter 23
Bio 202
Human Anatomy & Physiology Part 2
Tim Pimperl
A & P Instructor 1
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2. 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. 2 2

3. 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. 3 3

4. 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. 4 4

5. 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

6. 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

7. 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
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Path of
Sperm cells
Body of uterus
Infundibulum
Ovary
Path of
egg cell
Sperm cells
Egg cell
Cervix
Vagina
Semen deposited in vagina
during sexual intercourse
From M. Tegner and D. Epel. 16 February "Sea Urchin Sperm." Science, 179: © 1973 American Association for the Advancement of Science

8. 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

9. 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

10. 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.

11. 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 trophoblast and endometrium

12. 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
PTH maintains calcium concentrations in the blood

13. 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

14. 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
Amnion
Ectoderm
Germ layers of
embryonic disc
Amniotic cavity
Mesoderm
Endoderm
Connecting stalk
Chorionic villi
Yolk sac
of embryo

15. 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

16. Copyright © The McGraw-Hill Companies, Inc
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
As the amnion develops, it surrounds the embryo, and the umbilical cord begins to form from structures in the connecting stalk
Chorion
Umbilical
cord
Maternal
blood
vessels
Amnion
Allantois
Developing
placenta
Amniotic cavity
Yolk
sac
Extraembryonic
cavity
Endometrium

17. Amniochorionic membrane
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Amniochorionic membrane
Amniotic fluid
Umbilical cord
Chorion
Endometrium
Myometrium
Placenta

18. 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

19. Birth Process
Pregnancy terminates with the birth process called parturition
The process is complex as noted in Table 23.5

20. 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

21. 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)

22. 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

23. 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

24. 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

25. 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

26. Adulthood Adulthood Adolescence to old age
The person remains relatively unchanged anatomically and physiologically
Degenerative changes begin

27. 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

28. 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

29. 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

30. 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

31. 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

32. 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