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Neurulation. First major event of organogenesis Gives rise to brain and spinal cord Ectoderm folds inward as a neural groove with neural folds By 22nd d, neural folds fuse into neural tube Anterior end  brain; the rest  spinal cord.

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neurulation
Neurulation
    • First major event of organogenesis
    • Gives rise to brain and spinal cord
    • Ectoderm folds inward as a neural groove with neural folds
  • By 22nd d, neural folds fuse into neural tube
    • Anterior end  brain; the rest  spinal cord
slide2

21 d after conception, folds of tissue on back of developing embryo are rapidly growing together to form neural tube. Just a day later, growth is almost complete. If tissue fails to close completely development of spine, muscle and skin in this region is affected and the baby will be born with spina bifida.

Figure 28.10c

development of fetal circulation
Development of Fetal Circulation
  • Unique vascular modifications
    • Umbilical arteries and umbilical vein
    • Three vascular shunts
  • All are occluded at birth
development of fetal circulation1
Development of Fetal Circulation
  • Vascular shunts
    • Ductusvenosus: bypasses liver (umbilical vein ductusvenosus IVC)
    • Foramen ovale: opening in interatrial septum; bypasses pulmonary circulation
    • Ductusarteriosus: bypasses pulmonary circulation (pulmonary trunk ductusarteriosus aorta)
slide5

Israeli Prime Minister Ariel Sharon suffered a significant Hemorrhagic stroke today, according to a hospital here. He had been scheduled to undergo repair of a patent foramen ovale defect tomorrow.

Sharon, 77, had suffered a cerebral hemorrhage with “massive bleeding” and was undergoing brain surgery.

slide6

Fetus

Aortic arch

Superior vena cava

Ductus arteriosus

Ligamentum arteriosum

Pulmonary artery

Pulmonary veins

Heart

Lung

Foramen ovale

Fossa ovalis

Liver

Ductus venosus

Ligamentum venosum

Hepatic portal vein

Umbilical vein

Ligamentum teres

Inferior vena cava

Umbilicus

Abdominal aorta

Common iliac artery

Umbilical arteries

Medial umbilical ligaments

Urinary bladder

Umbilical cord

Placenta

High oxygenation

Moderate oxygenation

Low oxygenation

(a)

Very low oxygenation

Figure 28.14a

slide7

Newborn

Aortic arch

Superior vena cava

Ductus arteriosus

Ligamentum arteriosum

Pulmonary artery

Pulmonary veins

Heart

Lung

Foramen ovale

Fossa ovalis

Liver

Ductus venosus

Ligamentum venosum

Hepatic portal vein

Umbilical vein

Ligamentum teres

Inferior vena cava

Umbilicus

Abdominal aorta

High oxygenation

Common iliac artery

Moderate oxygenation

Low oxygenation

Umbilical arteries

Very low oxygenation

Medial umbilical ligaments

Urinary bladder

(b)

Figure 28.14b

effects of pregnancy anatomical changes
Effects of Pregnancy: Anatomical Changes
  • Uterus expands, occupying most of abdominal cavity
  • Lordosis occurs with change in center of gravity
  • Weight gain of ~13 kg (28 lb)
  • Relaxin causes pelvic ligaments and pubic symphysis to relax to ease birth passage
effects of pregnancy metabolic changes
Effects of Pregnancy: Metabolic Changes
  • Placental hormones
    • Human placental lactogen (hPL), or human chorionic somatomammotropin (hCS)
      •  maturation of the breasts, fetal growth, and glucose sparing in the mother
    • Human chorionic thyrotropin (hCT)
      •  maternal metabolism
  • Parathyroid hormone and vitamin D levels are high throughout pregnancy
effects of pregnancy physiological changes
Effects of Pregnancy: Physiological Changes
  • GI tract
    • Morning sickness due to elevated levels of estrogen and progesterone
    • Heartburn and constipation are common
  • Urinary system
    •  Urine production due to  metabolism and fetal wastes
    • Stress incontinence may occur as bladder is compressed
effects of pregnancy physiological changes1
Effects of Pregnancy: Physiological Changes
  • Cardiovascular system
    • Blood volume increases 25–40%
    • Blood pressure and pulse rise
    • Venous return from lower limbs may be impaired, resulting in varicose veins
parturition
Parturition
  • Parturition giving birth to the baby
  • Labor events that expel the infant from the uterus
initiation of labor
Initiation of Labor
  • Surfactant protein A (SP-A) from fetal lungs causes softening of the cervix
  • Fetal oxytocin causes the placenta to produce prostaglandins
  • Oxytocin and prostaglandins: powerful uterine muscle stimulants
slide14

Estrogen

Oxytocin

(+)

from

placenta

from fetus

and mother’s

posterior pituitary

Induces oxytocin

receptors on uterus

Stimulates uterus

to contract

Stimulates

placenta to make

(+)

Prostaglandins

Stimulate more

vigorous contractions

of uterus

Figure 28.17

stages of labor dilation stage
Stages of Labor: Dilation Stage
  • Longest stage of labor: 6–12 hours or more
  • Initial weak contractions:
    • 15–30 minutes apart, 10–30 seconds long
    • Become more vigorous and rapid
  • Cervix effaces and dilates fully to 10 cm
  • Amnion ruptures, releasing amniotic fluid
  • Engagement occurs: head enters the true pelvis
slide16

Umbilical

cord

Placenta

Uterus

Cervix

Vagina

(a) Dilation (early)

Figure 28.18a

slide17

Pubic

symphysis

Sacrum

(b) Dilation (late)

Figure 28.18b

stages of labor expulsion stage
Stages of Labor: Expulsion Stage
  • Strong contractions every 2–3 minutes, about 1 minute long
  • Urge to push increases (in absence of local anesthesia)
  • Crowning occurs when the largest dimension of the head distends vulva
  • Delivery of infant
slide19

Perineum

(c) Expulsion

Figure 28.18c

stages of labor placental stage
Stages of Labor: Placental Stage
  • Strong contractions continue, causing detachment of placenta and compression of uterine blood vessels
  • Delivery of the afterbirth (placenta and membranes) occurs ~30 minutes after birth
  • All placenta fragments must be removed to prevent postpartum bleeding
slide21

Uterus

Placenta

(detaching)

Umbilical

cord

(d) Placental

Figure 28.18d

first breath
First Breath
  •  CO2 central acidosis  stimulates respiratory control centers to trigger first inspiration
    • Requires tremendous effort: airways are tiny and the lungs are collapsed
    • Surfactant in alveolar fluid helps reduce surface tension
  • Respiratory rate: ~45 per minute for first two weeks, then declines
occlusion of fetal blood vessels
Occlusion of Fetal Blood Vessels
  • Umbilical vein becomes the ligamentum teres
  • Ductus venosus  ligamentum venosum
  • Foramen ovale  fossa ovalis
  • Ductus arteriosus  ligamentum arteriosum
lactation
Lactation
  • Colostrum
    • Yellowish secretion rich in vitamin A, protein, minerals, and IgA antibodies
    • Released the first 2–3 days
    • Followed by true milk production
  • Suckling initiates a positive feedback mechanism
  • Oxytocin causes the letdown reflex
slide25

Inhibits hypothalamic neurons that

release dopamine. Hypothalamus

releases prolactin releasing factors

(PRF) to portal circulation.

Start

Stimulation of

mechanoreceptors

in nipples by

suckling infant

sends afferent

impulses to the

hypothalamus.

Hypothalamus

sends efferent

impulses to the

posterior

pituitary where

oxytocin is stored.

Anterior pituitary

secretes prolactin

to blood.

Oxytocin is

released from the

posterior pituitary

and stimulates

myoepithelial cells

of breasts to contract.

Prolactin targets

lactiferous glands.

Milk production

Alveolar glands

respond by

releasing milk

through ducts of

nipples.

Figure 28.19

advantages of breast milk
Advantages of Breast Milk
  • Fats and iron easily absorbed; amino acids easily metabolized, compared with cow’s milk
  • Beneficial chemicals: IgA, complement, lysozyme, interferon, and lactoperoxidase
  • Interleukins and prostaglandins prevent overzealous inflammatory responses
advantages of breast milk1
Advantages of Breast Milk
  • Natural laxative effect helps eliminate bile-rich meconium, helping to prevent physiological jaundice
  • Encourages bacterial colonization of the large intestine