1. Growth and Development
ST 120

2. 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

3. 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

4. Growth and Development
Prenatal period: begins at conception and ends at birth
Postnatal period: the period after birth

5. 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

6. 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

7. 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

8. 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
The ovum has a store of nutrients to help support the embryonic development

9. 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

10. Fertilization to Implantation
The yolk sac in humans does not provide nutrition, instead, it functions to produce blood cells
The amniotic cavity becomes a fluid-filled, shock absorbing sac in which the embryo floats during development

11. Fertilization to Implantation
The chorion develops into the placenta
The chorionic villi connect the blood vessels of the chorion to the placenta

12. 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

13. Periods of Development
Gestation is divided into three 3-month segments called trimesters
During the 1st trimester, the zygote develops into the morula and then the blastocyst

14. 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

15. 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

16. 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

17. Endoderm 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

18. Mesoderm Dermis of skin Circulatory system Many glands Kidneys Gonads
Muscle
Bones (except facial)

19. Ectoderm Epidermis Tooth enamel Lens and cornea of eye Outer ear
Nasal cavity
Facial bones
Skeletal muscles of head
Brain and spinal cord
Sensory neurons

20. Histogenesis
The process of how the primary germ layers develop into many different kinds of tissues

21. Organogenesis
The way the tissues arrange themselves into organs

22. 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

23. 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

24. 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

25. 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

26. End of Day 1
Questions???????

27. Postnatal Period Begins at birth and lasts until death
Growth and development occur gradually throughout life

28. 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

29. How Big is Your Face? The infant face is 1/8 of the skull surface
The adult face is ½ of the skull surface

30. Postnatal Periods Infancy Childhood Adolescence and adulthood
Older adulthood

31. Infancy Lasts about 18 months
1st 4 weeks are referred to as neonatal period
Newborn must become totally self-supporting after being fully dependent on the mother
Rapid development of the nervous and muscular systems

32. Childhood The end of infancy to puberty
Overall, growth is rapid, but month-to-month gains are less consistent
Deciduous teeth, which appear at ~6 months, are lost at ~ 6 years

33. Childhood Becomes less chubby Potbelly gets flatter
Development of numerous motor and coordination skills

34. 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

35. 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

36. Older Adulthood
Gradual, but certain decline in the functioning of every major organ system
Senescence: older adulthood

37. 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

38. Effects of Aging Skin Dry Thin Inelastic
Increased wrinkles and skinfolds
Pigmentation changes
Thinning and loss of hair

39. 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

40. 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

41. 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

42. 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

43. 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

44. End of Day 2
Questions??????