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GIGU test! > Parturition, lactation, and neonatal physiology > Flashcards

Parturition, lactation, and neonatal physiology Flashcards

1
Q

when does Human birth occur and what does parturition involve?

A

Human birth usually occurs at 40 weeks gestation (s3 weeks fetal age)

Parturition involves:

  • Transformation of the myometrium from quiescent to highly contractilve
  • Remodeling of the uterine cervix to soften and dilate it
  • rupture of the fetal membranes
  • expulsion of the uterine contents
  • return of the uterus to its prepregnant state
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2
Q

What are the changes that occur in the uterine activity during parturition?

A

Most pregnancy uterus is relaxed, quiescent, relatively insensitive to hormones that stimulate contractions (prostglandins and oxytocin)

uterus grows and distends to acccommodate the developing fetus, placenta, and amniotic fluid

Uterine myometrial cells undergo significant hypotrophy

weak irregular contractions, braxton hicks contractions, occur towards end of pregnancy

  • not powerful enough to induce labor
  • thought to prepare the uterus for parturition
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3
Q

Hormonal changes in Progesterone for parturition?

A

Progesterone:

  • promotes the myometrial relaxation during pregnancy
  • blocks contractions of labor
  • treatment with nuclear progesterone antagonists increases myometrial contractility (can induce labor at any stage of pregnancy)

Thought to be a desensitization of uterine cells to the actions of progesterone

  • functional rather than systemic withdrawal
  • leads to an increase in estrogen receptor expression
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4
Q

Hormonal changes in estrogen for parturition

A

Estrogens:

  • following progesterone desensitization in uterine cells, increase in estrogen receptor expression
  • increase myometrial contractility and cervical dilation

oppose the actions of progesterone by increasing responsiveness to oxytocin and prostglandins

  • stimulate formation of gap junctions
  • increase number of oxytocin receptors in myometrium and decidual tissue

Increase production and release of prostaglandins by fetal membranes

stimulate expression of proteolytic enzymes in the cervix i.e. collagenase

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5
Q

hormonal changes in prostaglandins in parturition

A

Prostaglandins:

  • stimulate strong myometrial contraction
  • will initiate labor via large dose of PGF2a and PGE2 can induce myometrial contractions at any stage of gestation

PGF2a potentiates oxytocin induced contractions by promotion of gap junctions
-stimulate effacement of cervix in labor

synthesis of prostaglandins stimulated by:

  • estrogen in fetal membranes
  • oxytocin in uterine cells
  • uterine stretch
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6
Q

hormonal changes in oxytocin in parturition?

A

Oxytocin:

Uterus is insensitive to oxytocin until week 20

Estrogen increases the oxytocin receptor numbers

  • 80x higher than baseline at 36 weeks
  • 200x by early labor
  • uterine myometrium for smooth muscle contraction
  • decidual tissues stimulate PGF2a production
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7
Q

what is the fergusion reflex?

A

During labor, oxytocin stimulates uterine contractions that sustain labor that stimulates the production of PGF2a production in decidual cells

this is released in bursts during active labor that increases its frequency as labor progresses

this primary stimulus for release is distention of the cervix that creates a positive feedback loop to enhance labor

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8
Q

hormonal changes in relaxin in parturition

A

Relaxin:

  • cytokine structurally related to insulin
  • produced by the corpus luteum, placenta, and decidua
  • plays a role in keeping uterus in a quite state during pregnancy
  • maximal plasma concentration at weeks 38-42
  • may soften and help dilate the cervix
  • elevated levels at 30 weeks associated with premature birth
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9
Q

mechanical changes that occur in parturition

A

Uterine size:

  • a factor in regulating parturition
  • stretch of smooth muscle increases ferguson reflex positive feedback and thus further contractions
  • uterine stretch also increases prostaglandin production
  • twins average 19 day shorter gestation

Cervical remodeling is necessary for expulsion of fetus
-structural changes resulting in change from fetal support to birth canal

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10
Q

Initiation of labor

A

Placenta produces corticotropin releasing hormone (CRH)

  • maternal levels rise during late pregnancy and labor
  • promotes myometrial contractions (sensitizing uterus to prostaglandins and oxytocin
  • accumulates in fetal circulation

Stimulates fetal secretion

  • increase fetal adrenal cortisol production which stimulates furthur placental CRH release
  • increase fetoplacental estrogen which enhances myometrial contractility
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11
Q

how do contractions occur in pregnancy, labor, and parturition

A

Most of pregnancy, uterus undergoes periodic episodes of weak and slow contractions
-braxton hicks contractions

Become exceptionally strong during last hours of pregnancy into active labor

  • begin to stretch cervix, shorten muscle walls
  • retract lower uterine segment and cervix upward
  • cervix becomes increasingly dilated and is drawn up to just below the pelvic inlet

Fully dilated cervix is drawn up just below the pelvic inlet

subsequent uteine contractions push fetus downward and through the pelvis

Entire process varies in duration

  • first stage occupies most of the time
  • second stage is generally less than an hour
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12
Q

5 Phases of delivery

A

1) presentation of head
2) rotation and delivery of anterior shoulder
3) delivery of posterior shoulder
4) delivery of lower body and umbilical cord
5) expulsion of the placenta

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13
Q

How does the body expulse the placenta?

A

Uterus contracts reducing area of attachment

separation of placenta results in bleeding and clotting

  • oxytocin constricts uterine blood vessels
  • nipple stimulation induces oxytocin release
  • synthetic oxytocin sometimes given to assist uterine contractions
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14
Q

what does surfactant do in the lungs?

A

Secreted by type II alveolar epithelial cells

synthesis begins in the last semester

once alveoli open, harder to close them when exhaling with surfactant

this is because surfactant decreases the surface tension

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15
Q

what is the stimuli of breathing at birth and what if it is delayed

A

Breathing initiates within seconds of birth

stimuli:

  • Asphyxiation during birth
  • sudden drop in temperature/cooling of the skin

delayed breathing upon birth

  • use of general anesthesia during delivery
  • prolonged labor
  • head trauma, depressed respiratory center
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16
Q

pressure changes for the first breath

A

At birth alveoli are collapsed and amniotic fluid fills them

more than 25mmHg negative inspiratory pressure needed to overcome surface tension and open the alveoli

1st inspiration the infant is capable of 60mmHg of O2
1st inspiratory movements brings in nearly 40 ml of air

deflation requires strong positive power
-must overcome viscous resistance of fluid in bronchioles

17
Q

pressure changes for the second breath?

A

Second breath requires less effort and so forth

doesnt become normal until 40 min after birth

settles to 40 breaths per minute and the tidal volume of 6-10ml/kg

18
Q

fetal blood flow vi the placenta

A

Massive blood flow to placenta shunts blood away from the lower trunk

umbilical arteries

  • branch repeatedly
  • returns deoxygenated blood
  • dense capillary network at terminal villi
  • legs connect to the inferior vena cava

umbilical vein:

  • returns oxygenated blood to fetus from placenta
  • PO2 = 30-35 mmHg
  • blood enters ductus venosus
19
Q

what is the ductus venosus

A

liver bypass

  • liver is largely non functional
  • direct route from umbilical vein to the inferior vena cava
20
Q

function of the foramen ovale

A

Hole in septum dividing the atria found in the posterior aspect of the right atrium

  • right to left shunt
  • bypass around the right ventricle
  • PO2 about 27mmHg inferior vena cava right through to left ventricle to supply the carotid and brain
  • of blood entering the right atrium 27% is shunted through the foramen ovale
21
Q

function of the ductus arteriosus

A

Pulmonary artery to aorta

  • another right to left shunt
  • substantial amount of smooth muscle that is being dilated by prostaglandins (PGE2)
22
Q

how does closure of the foramen ovale occur?

A

Reversal of pressure gradient across the atria

pushes foramen ovales valve shut

due to:

  • increased venous return to left atrium and elevated left atrial pressure
  • decreased right atrial pressure

eventually flap will seal

23
Q

how does the ductus arteriosus close?

A

Aortic pressure rises above the pilmonary artery pressure making blood flow the wrong way

now well oxygenated aortic blood flows through the ductus arteriosus

  • high pO2 causes vasoconstriction within an hour
  • falling prostaglandin levels
  • 1-8 day constriction is sufficent
  • 1-4 mo anatomically occluded
24
Q

what does closure of the ductus arteriosus and foramen ovale establish?

A

a right and left circulatory system

  • sytemic
  • pulmonary
25
Q

what is a patent foramen ovale

A

In 20percent of individuals by 2 years of age the foramen ovale does not close permanetly

  • increased right atrial pressure can push open the flap
  • sustained pulmonary hypertension or transient increases (bowel movement, coughing, and sneezing)
26
Q

patent ductus arteriosus (PDA)

A

Heart problem occurs soon after birth

  • van be heard as a heart murmur on stethoscope
  • oxygenated blood in aorta mixes with deoxygenated blood in pulmonary artery
  • puts strain on heart and increases pulmonary blood pressure
27
Q

how does the ductus venosus close?

A

Immediately after birth, most portal blood flow through ductus venosus

  • 1-3 hours muscle wall of ductus venosus contracts and closes
  • portal venosus pressure rises forcing venous blood through liver sinus
  • rarely fails to close
28
Q

Characteristics of the fetal kidney

A

nephrogenesis begins at 8 weeks gestation and completed at 36 weeks

urine production begins as early as 10 weeks through 20 weeks gestation

fetal urine accounts for 70-80 percent of amniotic fluid

renal function matures rapidly in the 3rd trimester
-body fluid balance, acid-base balance, and electrolyte balance

Functional development completes closet to `1 month of age

29
Q

Characteristics of the fetal liver

A

Poor conjugation of bilirubin, deficiency in forming plasma proteins and coagulation factors, deficient gluconeogenesis
-blood glucose levels the 1st day could be as low as 30-40mg/dL

infant uses its stored fats and proteins for metabolism until mothers milk can be provided

30
Q

Characteristics of the fetal hemoglobin

A 
Hb F (a2y2) is the major hemoglobin of fetal life
-oxygen has a higher binding affinity than to an adults Hb A (a2b2)

normal adult levels of HB A2 are achieved by the 12th week of life

31
Q

what are the nutritional needs of the neonate?

A

Ca+ and vitamin D for rpid ossification of bones
-normally the adequate amount can be supplied by the usual diet of milk

Iron:

  • liver has stored enough iron to keep forming blood for 6 months
  • iron content of breast milk is low, but high bioavailabillity
  • this is the reverse in formula

Vitamin C:

  • vitamin C is not stored in significant quantities in the fetal tissues
  • adequate amounts can be provided by the mothers breast milk
32
Q

Characteristics of neonatal immunity

A

Neonate inherits a great degree of immunity from the mother and does not form antibodies of its own to a significant extent

antibodies inherited from the mother protect the infant for about 6 months against most major diseases

Baby own immune system begins to form antibodies and gamma globulin concentrations return to normal by age of 12-20 months

33
Q

Breast development from birth to sexual maturity

A

At birth, mammary gland almost entirely lactiferous duct with few alveoli
-apart from some branch development, the breast remains in this state until puberty

under the actions of estrogens, lactiferous ducts sprout and branch
-ends form small solid, spheroidal masses of cells which develop into alveoli

as menstrual cycle is establishe, mammary tissue is exposed to estrogen and progesterone
-induces additional ductal-lobular-alveolar growth

breast increases in size

  • deposition of adipose and connective tissue
  • involution
  • some secretory activity occurs
  • breast tenderness
34
Q

cells of the breast tissue

A

Alveolar epithelium:

  • luminal epithelial
  • cells responsible for milk synthesis and secretion

Myoepithelial cells:

  • between epithelial cells and basement membrane
  • contractile function
  • move milk from alveoli to duct
35
Q

Hormones that affect breast development

A

puberty:

  • estrogens
  • progesterone

pregnancy:

  • prolactin
  • hPL
  • estrogens
  • progesterones

these homones that affect the breast are:

  • mammogenic: promoting the proliferation of alveolar and duct cells
  • lactogenic: promoting contraction of myoepithelial cells and thus milk ejection
  • galactopoietic: maintaining milk production after it has been established
36
Q

what are the 5 main ways that alveolar epithelial cells excrete milk?

A

1) secretory pathway through the ER and Golgi
2) Transcellular endocytosis and exocytosis
3) Lipid pathway via milk lipids
4) Transcellular salt and water transport
5) paracellular pathway

37
Q

4 effects of suckling on hormone release

A

1) suckling stimuli or sight of a child
- activates afferent neural pathway from breast to spinal cord and then to hypothalamus

2) Dopamine release is inhibited
- releases inhibition of lactotrophs and results in release of prolactin which stimulates milk production

3) Stimulation of production and release of oxytocin from posterior pituitary
- interacts with myoepithelial cells resulting in let down of milk

4) inhibition of hypothalamus GnRH production
- results in decreased release of LH and FSH and inhibits the ovarian cycle

38
Q

Cessation of lactation

A

When the suc\kling stimulus is discontinued milk accumulates

  • distension and mechanical atrophy of epithelial structures
  • rupture of alveolar walls
  • compression of capillaries resulting in alveolar hypoxia

Cell and glandular debris are phagocytosed

lobular acinar structures become smaller

ductal system predominates

full involution can take up to 3 months

GIGU test! (40 decks)

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