Read Microsoft PowerPoint - Parturition, Lacation and early neonatal physiology.pptx text version

5/6/2010

Parturition, Lacation and early neonatal physiology

Dale Buchanan Hales, PhD [email protected]

Fetal hemoglobin binds Oxygen at lower partial pressures

1

5/6/2010

Maternal and Fetal Oxygen Levels

Site Maternal Values Uterine artery Intervillous space Uterine vein PO2 (mm Hg) 100 30-35 30 Hemoglobin Saturation 97.5% 57%-67% 57%

Fetal Values Umbilical arteries Umbilical vein 23 30 60.5% 85.5%

Figure 572 Fetal circulation. A, This schematic drawing shows the major elements of the fetal circulation. Note thatin the main drawingthe heart is upside down, for the sake of presenting the blood flow as simply as possible. The heart is right side up in the inset. Because the inputs and outputs of the right and left hearts mix, we define the CCO as the sum of the outputs of the right and left ventricles. The percentage of the CCO that passes various checkpoints is represented as a number in a black box. The CCOs of the right ventricle (66%) and the left ventricle (34%) add up to 100%. The fetal circulation has four major shunts: the placenta, the ductus venosus, the foramen ovale, and the ductus arteriosus. B, The schematic drawing is the same as in A, exceptat each checkpointwe show the O2 saturation of HbF against a black background and the PO2 (in mm Hg) against a white background. The relationship between the O2 saturation and PO2 figures is based on the O2 saturation curve for HbF (similar to the curve labeled Hb + CO2 in Fig. 297).

Downloaded from: StudentConsult (on 27 April 2010 10:16 PM) © 2005 Elsevier

2

5/6/2010

Patent Foramen Ovale PFO

Figure 573 Effect of birth on pulmonary vascular resistance, blood flow, and mean arterial pressure. In the fetus, pulmonary vascular resistance is high, pulmonary blood flow is low, and mean pulmonary arterial pressure is high. At birth, each of these three situations rapidly reverses. The primary event is the fall in resistance, which occurs because of the following: (1) the pulmonary blood vessels are no longer being crushed; (2) breathing causes increased PO2, which, in turn, causes vasodilation; and (3) local prostaglandins cause vasodilation. The reason that pressure falls after birth is that the fall in pulmonary vascular resistance is greater than the rise in blood flow. (Data from Rudolf AM: Congenital Diseases of the Heart: ClinicalPhysiological Considerations. Armonk, NY: Futura, 2001.)

Downloaded from: StudentConsult (on 27 April 2010 10:16 PM) © 2005 Elsevier

3

5/6/2010

Figure 574 Changes in the circulation at and around birth. A, Closure of these two shunts establishes separate right and left circulatory systems. As the pressure in the left atrium rises higher than the pressure in the right atriumowing to the large decrease in pulmonary vascular resistancethe flap of the foramen ovale pushes against the septum, thus preventing blood flow from the left to the right atrium. Eventually, this flap seals shut. As aortic pressure exceeds the pressure of the pulmonary artery, blood flow through the ductus arteriosus reverses. Welloxygenated aortic blood now flows through the ductus arteriosus. This high PO2 causes vasoconstriction, which functionally closes the ductus arteriosus within a few hours. Falling prostaglandin levels also contribute to the rapid closure. Eventually, the lumen of the ductus becomes anatomically obliterated. B, The elimination of the fetal shunts and the oxygenation of blood in the lungs lead to major increases in the O2 saturation and PO2 in the circulation.

Downloaded from: StudentConsult (on 27 April 2010 10:16 PM) © 2005 Elsevier

Figure 571 Synthesis of DPPC. Before birth, cortisol upregulates several enzymes that are important for the synthesis of surfactant, including FA synthase and phosphocholine transferase. CoA, coenzyme A.

Downloaded from: StudentConsult (on 27 April 2010 10:16 PM) © 2005 Elsevier

4

5/6/2010

Parturition

Oxytocin stimulates smooth muscle contractions Oxytocin secretion from posterior pituitary

Fetal cortisol

Cortisol inhibits progesterone which promotes contractions Mechano receptors signal to brain Fetal CRH/ ACTH Pressure against cervix

Parturition

5

5/6/2010

Uterine wall contractions

Oxytocin and parturition

6

5/6/2010

Parturition starts with locally organized uterine contractions. These stimulate nucleus tractus solitarii (NTS) A2 noradrenergic neurons that project to oxytocin neurons. The noradrenergic input primes and activates a burst mechanism in the oxytocin neurons, and this activation is further enabled by weak coupling between the oxytocin neurons. Noradrenaline also stimulates somatodendritic oxytocin release which, through binding of oxytocin to autoreceptors, is critically important in bi di f i i i i ll i i driving burstfiring. The coordinated burstfiring of oxytocin neurons leads to pulsatile oxytocin secretion from the posterior lobe of the pituitary into the circulation, promoting uterine contractions. Oxytocinneuron activity is kept in check by a central opioid mechanism, which tonically inhibits the neurons and can thus slow or suspend oxytocin secretion and births during environmental disturbance. Increased local oxytocin release and decreased allopregnanolone levels at parturition together reduce GABAAreceptor (aminobutyric acid A receptor) function. This reduced effectiveness of inhibitory GABA synapses on oxytocin neurons enables greater effectiveness of excitatory input effectiveness of excitatory input

Proposed "parturition cascade" for labor induction at term. The spontaneous induction of labor at term in the human is regulated by a series of paracrine/autocrine hormones acting in an integrated parturition cascade responsible for promoting uterine contractions. ti t i t ti PGE2, prostaglandin E2; PGEM, 13, 14-dihydro-15-keto-PGE2; PGF2, prostaglandin F2; PGFM, 13, 14dihydro-15keto-PGF2.

7

5/6/2010

Changes in the uterus caused by pregnancy and parturition. The hormonal changes of pregnancy as well as dynamic forces of labor cause the development of the lower uterine segment from the vestigial uterine isthmus. After parturition, these changes regress dramatically. Low transverse cesarean delivery incisions are performed through this thinned isthmic region, known as the lower uterine segment

8

5/6/2010

Parturition

Anatomy of y the lactating breast

9

5/6/2010

Lactation: milk let down and ejection

Figure 5611 Cross section of the breasts and milk production. A, The breast consists of a series of secretory lobules, which empty into ductules. The ductules from 15 to 20 lobules combine into a duct, which widens at the ampullaa small reservoir. The lactiferous duct carries the secretions to the outside. B, The lobule is made up of many alveoli, the fundamental secretory units. C, Each alveolus consists of secretory epithelial cells (alveolar cells) that actually secrete the milk, as well as contractile myoepithelial cells, which are, in turn, surrounded by adipose cells. D, The alveolar cell secretes the components of milk through five pathways.

Downloaded from: StudentConsult (on 27 April 2010 10:16 PM) © 2005 Elsevier

10

5/6/2010

Mechanical stimulation of nipples promotes milk production and ejection

Figure 5612 Effect of suckling on the release of PRL, OT, and GnRH. Suckling has four effects. First, it stimulates sensory nerves, which carry the signal from the breast to the spinal cord, where the nerves synapse with neurons that carry the signal to the brain. Second, in the arcuate nucleus of the hypothalamus, the afferent input from the nipple inhibits neurons that release DA. DA normally travels through the hypothalamicportal system to the anterior pituitary, where it inhibits PRL release by lactotrophs. Thus, inhibition of DA release leads to an increase in PRL release. Third, in the supraoptic and paraventricular nuclei of the hypothalamus, the afferent input from the nipple triggers the production and release of OT in the posterior pituitary. Fourth, in the preoptic area and arcuate nucleus, the afferent input from the nipple inhibits GnRH release. GnRH normally travels through the hypothalamicportal system to the anterior pituitary, where it stimulates the synthesis and release of FSH and LH. Thus, inhibiting GnRH release curbs FSH and LH release and thereby inhibits the ovarian cycle.

Downloaded from: StudentConsult (on 27 April 2010 10:16 PM) © 2005 Elsevier

11

Information

Microsoft PowerPoint - Parturition, Lacation and early neonatal physiology.pptx

11 pages

Find more like this

Report File (DMCA)

Our content is added by our users. We aim to remove reported files within 1 working day. Please use this link to notify us:

Report this file as copyright or inappropriate

1087482


You might also be interested in

BETA
Pairman-1st-revised.indd
31-07-01.PDF
National Goat Handbook