Pregnancy growth and development Chapter 23 Introduction After

Pregnancy, growth, and development Chapter 23

Introduction • After fertilization, 38 weeks of cell division • Specialization into distinct tissues/organs • Growth- increase in size • Development- continuous process, one life phase to another, includes growth – Prenatal- fertilization to birth (pregnancy) – Postnatal- birth to death

Fertilization • Sperm nucleus unties with egg nucleus • Zygote

Prenatal period • Presence of developing offspring in uterus • Consists of three trimesters (3 months) • 38 weeks from conception to birth • Three stages – Cleavage – Embryonic – Fetal

Cleavage stage • Rapid cell division • Cytoplasm divided, smaller and smaller cells (blastomeres)

Cleavage stage • Zygote- fertilized egg • Morula- solid ball of cells, cleavage and no growth • Blastocyst- hollow ball of cells, embryoblast, trophoblast

Trophoblast Blastocyst Inner cell mass Uterine wall Invading trophoblast Trophoblast Inner cell mass Endometrium Implantation

Trophoblast cells secrete h. CG maintains corpus luteum Corpus luteum continues to secrete estrogens and progesterone Estrogens and progesterone promote growth, development, and maintenance of uterine wall

Embryonic stage • Beginning of second week through eighth week • Placenta forms • Internal organs develop • Major external body structures appear

Embryonic development • Gastrulation • Three layers Neural tube (Spinal cord) Skin Amniotic fluid Digestive tract Yolk sac Heart Brain Endoderm Ectoderm Mesoderm

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Embryonic stage • Structures – Chorion- outer membrane, invades endometrium – Amnion- inner layer, forms amniotic sac – Yolk sac- nourishment before placenta – Placenta • Oxygen, nutrients, waste products, diffuse across membrane • Bad stuff- carbon monoxide, alcohol, drugs, Rh antibodies, HIV, bacteria, viruses – Umbilical cord- transport above, two arteries, one vein

Uterine wall Umbilical arteries Umbilical vein Fetal capillaries Maternal blood in lacuna Diffusion Oxygen and nutrients into fetal blood Placenta Blood flow from fetus, branch of umbilical artery Blood flow to fetus, branch of umbilical vein Diffusion Waste substances into maternal blood Chorionic villus

Fetal cardiovascular adaptations • Blood- hemoglobin has greater oxygencarrying capacity • Fetal hemoglobin vs. adult hemoglobin • Takes 2 years, postnatal

Lens Maxillary process Mandibular process Developing eye Forebrain Developing ear Elbow Handplate Hindlimb Paddle-shaped forelimb (a) 35 ± 1 day (10– 12 mm) (b) 37 ± 1 day (12. 5– 15. 75 mm) External acoustic Midbrain meatus External ear Pigmented External ear eye Wrist Heart prominence Digital rays Toe rays Paddle-shaped (d) 45 ± 1 day (22– 24 mm) foot plate – (c) 40 ± 1 day (16– 21 mm) Eyelid Webbed fingers Notches between toe rays Ear (e) 49 ± 1 day (28– 30 mm) Fingers separated Toes separated Fan-shaped webbed toes (f) 52 ± 1 day (32– 34 mm) (g) 56 ± 1 day (34– 40 mm)

When physical structures develop Reproductive system Ears Eyes Upper and lower limbs Heart Central nervous system 0 1 2 3 4 5 6 Month 7 8 9

Fetal stage • End of 8 th week • Growth is rapid, body changes considerably • At beginning, head is disproportionately large and limbs are short

2 month 3 month embryo fetus Newborn 2 years 5 years 13 years 22 years

Increasing hormone concentration • Placenta takes over hormone production – Maintains uterine lining – Inhibits FSH, LH – Stimulates development of mammary glands – Inhibit uterine contractions Human chorionic gonadotropin Estrogens Progesterone 0 1 2 3 4 5 6 7 Months of pregnancy 8 9

Other Changes During Pregnancy • Growth of the uterus displace organs, heartburn and increased urinary frequency • Increase in oxygen and waste, increase in blood volume, cardiac output, breathing rate, and urine production • Increased intake of vitamins, minerals, and proteins

Parturition • Birth of baby • Secretion of progesterone decreases, lessens inhibiting effect on contractions, stimulates secretion of prostaglandins • Stretching of uterus stimulates oxytocin release, stimulates uterine contractions (positive feedback)

Baby drops lower in uterus to initiate labor Cervical stretch causing stimulates Push baby against cervix Oxytocin release Positive feedback loop Uterine contractions Delivery of baby stops the cycle causes

Amniotic sac Urinary bladder Placenta Ruptured amniotic sac Urethra Vagina Cervix Rectum Uterus Placenta Umbilical cord

Milk production/secretion • Placental estrogens/progesterone stimulate development of mammary glands • Prolactin • Secretion doesn’t begin until after birth Glandular tissue Connective tissue Glandular tissue with secretions

Release Secretion Nipple or areola of breast is stimulated Duct Milk Nerve impulses travel to hypothalamus Lumen Myoepithelial cells Hypothalamus signals posterior lobe of pituitary gland to release oxytocin Oxytocin causes myoepithelial cells surrounding alveolar glands to contract Milk is ejected from ductile system through nipple

Colostrum- proteins, antibodies, lower amounts of carbs/fats

Postnatal period • Birth until death – Neonatal – Infancy – Childhood – Adolescence – Adulthood – Senescence

Neonatal • Birth until end of 4 th week • Body adjusting to outside world- respiration, obtaining nutrients, digestion, excrete wastes, regulate body temp

Infancy End of 4 th week to one year High growth rate Teeth Maturation of muscular/nervous system • Communication • •

Childhood One year to puberty High growth rate Permanent teeth Muscle control (bladder/bowel) • Increased intellectual abilities • •

Adolescence • • Puberty to adulthood Reproductively/emotionally more mature Growth spurts Increased motor skills/intellect

Adulthood • Adolescence to old age • Relatively unchanged anatomically/physiologically • Degenerative changes begin

Senescence • Old age to death • Degenerative changes continue • Body becomes less able to cope with demands • Death from various conditions/diseases

Senescence • Integumentary- loss of collagen/elastin, pigmentation • Skeletal- bone loss, compression of vertebrae • Muscular- loss of muscle fibers • Nervous- loss of connections, diminished processing ability • Endocrine- inability to maintain homeostasis • Cardiovascular- decreased resistance, output • Immune- decreased efficiency • Respiratory- reduced capacity • Urinary- fewer functional nephrons

Aging • Difficult to analyze, individualized • Gerontology- biological changes of aging • Active/passive

Passive aging • Something that happens over time • Break down of structures and slowing of functions • Degradation of elastin/collagen, cell degradation- free radicals

Active aging • New activities or substances • Autoimmunity • Apoptosis

Human life span • Life expectancy is a projection of how long an individual will live • 75. 4 years men, 83. 2 years women • Medical advances contribute to improved life expectancy

End of semester stuff • Fun times! • SRTE • Final exam schedule