Chapter 28 Pregnancy and Human Development


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Chapter 28 Pregnancy and Human Development
1

Preeclampsia-Eclampsia Syndrome
• Symptoms – Hypertension and proteinuria caused by vascular spasms – decreased blood flow in fetus
• Classifications – Mild – systolic increase of >30 mmHg or diastolic of >15 mmHg. – Severe = Eclampsia – convulsive state
• Treatment – bed rest, high protein diet, reduced sodium (?), Calcium and Mag supplements, drugs for hypertension and sedatives – if severe give Mag sulfate
• Believed due to immunological abnormalities • Correlated with number of fetal cells that enter maternal circulation

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2

Lactation
• Production of milk by the mammary glands • Toward the end of pregnancy
– Placental estrogens, progesterone, and lactogen stimulate the hypothalamus to release prolactin-releasing factors (PRFs)
– Anterior pituitary releases prolactin

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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

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Figure 28.19 Milk production and the positive feedback mechanism of the milk let-down reflex.

Start
Stimulation of mechanoreceptors in nipples by suckling infant sends afferent
impulses to the hypothalamus.

Hypothalamus releases prolactin releasing factors (PRF) to portal circulation.

Hypothalamus sends efferent impulses to the
posterior pituitary where oxytocin is stored.

Anterior pituitary secretes prolactin
to blood.

Positive feedback

Oxytocin is released from the posterior pituitary
and stimulates myoepithelial cells of breasts to contract.

Prolactin targets mammary glands
of breasts.
Milk production

Let-down reflex. Milk is ejected through ducts of nipples.

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Advantages of Breast Milk

• Fats and iron are easily absorbed; amino acids more easily metabolized, compared with cow’s milk

• Beneficial chemicals: IgA, complement, lysozyme, interferon, and lactoperoxidase

• Interleukins and prostaglandins prevent overzealous inflammatory responses

• Natural laxative effect helps eliminate bile-rich meconium, helping to prevent physiological jaundice

• Encourages bacterial colonization of the large intestine

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Development of Fetal Circulation
• First blood cells arise in the yolk sac • By the end of the third week
– Embryo has a system of paired vessels – Vessels forming the heart have fused

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Figure 28.13 Circulation in fetus and newborn. 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

Newborn

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Placenta

High oxygenation Moderate oxygenation Low oxygenation Very low oxygenation

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Congenital Heart Defects

• Patent ductus arteriosis – duct does not close which leads to increase pulmonary BP
• Atrial septal defect – foramen ovale does not close which leads to poor oxygenation of blood
• Coarctation of aorta – aorta is constricted which leads to increase workload on heart
• Tetralogy of Fallot – multiple defects

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Figure 18.25 Three examples of congenital heart defects.

Occurs in about 1 in every 500 births

Narrowed aorta
Occurs in about 1 in every 1500 births

Occurs in about 1 in every 2000 births

Ventricular septal defect. The superior part of the inter-ventricular septum fails to form, allowing blood to mix between the two ventricles. More blood is shunted from left to right because the left ventricle is stronger.

Coarctation of the aorta. A part of the aorta is narrowed, increasing the workload of the left ventricle.

Tetralogy of Fallot. Multiple defects (tetra = four): (1) Pulmonary trunk too narrow and pulmonary valve stenosed, resulting in (2) hypertrophied right ventricle; (3) ventricular septal defect; (4) aorta opens from both ventricles.

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Chapter 28 Pregnancy and Human Development