Physician Assistant Pha 529 > Steffes > Flashcards > Physiology Lecture 13 - 9/22/2011

What are the 3 phases of the endomedtrium?

Proliferation

Development of secretory changes

Menstruation

Describe the proliferative stage of menstruation

Initiated by secretion of estrogen from developing follicles

Only a thin layer of basal stroma present at the beginning of the cycle and only remaining epithelial cells located deep in the crypts of the endometrium and deep portions of the endometrial glands

Rapid proliferation in response to estrogen

Re-epithelialized in 4 – 7 days

Over next 10 days, thickens up to 4 mm

What initiates the secretory phase of menstruation? Describe the secretory phase.

Due to changes brought about by progesterone

Progesterone causes swelling and secretory development of the endometrium

Glands secrete fluid

Endometrial cells accumulate lipids and glycogen in the cytoplasm

Energy is being stored

Vascularity increases

At peak (1 week after ovulation), endometrium is ~6 mm thick.

Describe the menstruation phase of.... menstruation

What?

Within 2 days of the involution of the corpus luteum

Endometrium rapidly involutes to 65% of its thickness

24 hours before menstruation, vessels become vasopastic and the tissue becomes ischemic/necrotic and sloughs

Not all of the cells are dead

Expulsion due to uterine contractions

What causes uterine contraction during menstruation?

Distention

Elevated levels Prostaglandin E2 from ischemic and necrotic tissue

Lower levels of progesterone

Menstrual fluid is nonclotting due to _______ from the endometrial tissue.

fibrolysin

Regulation of female monthly rhythm:

Interplay between ovarian and hypothalamic pituitary hormones

In the absence of suppression, the pituitary secretes FSH and LH. New primary follicles begin to develop and the estrogen is produced.

Estrogen in small amounts strongly inhibits secretion of FSH and LH through a direct pituitary effect.

Estrogen alone inhibits the hypothalamic secretion of _______

Progesterone has a synergistic effect with estrogen but a weak _________ effect by itself.

GnRH

inhibitory

For unknown reasons, the pituitary gland secretes a large amount of __ (despite the inhibitory effect of estrogen) immediately before ovulation. This triggers ovulation and transformation of the granulosa and thecal cells to _______ cells

LH

luteal

After ovulation, what hormones are secreted by the corpus luteum to inhibit LH and FSH?

estrogen, progesterone, inhibin (inhibits FSH more than LH)

Once __ levels fall to minimal values (due to inhibitory hormones from the corpus luteum), the corpus luteum _________s and estrogen and progesterone levels fall to near zero. As those levels fall, FSH and LH levels begin to rise

LH

involutes

What is the definition of puberty?

onset of adult sexual life, marked by gradual increase in secretion of estrogen from developing follicles responding to increasing concentrations of FSH and LH

Females 11 – 16 years (average 13 y.o.)

What is the definition of menarche?

– onset of menstruation. First several cycles are usually anovulatory

Characteristics of menopause

cycles cease and ovarian hormone levels fall to minimal values

Presence of an inadequate number of primary follicles to response to stimulatory effect of FSH

Estrogen-secretory dynamics therefore inadequate to trigger the LH surge (i.e. anovulatory cycle)

After several anovulatory cycles, estrogen production near zero

LH and FSH secretion is very high for years

What causes anovulatory cycles?

if the LH surge is insufficiently high (the first few cycles of puberty and for several months before menopause), ovulation will not occur. Therefore, the corpus luteum does not develop, there is little no progesterone in the second half other cycle, and the cycle is shortened by several days.

What are the 3 requirements for female fertility?

Properly timed ovulation

Ability of sperm to reach ovum in tube within 24 hours of ovulation

Ability of zygote to implant and survive

List the possible causes for failure to ovulate.

Mechanical obstruction

Thick ovarian capsule
Scarring from infection
Overgrowth of surface by endometriosis

Obstruction of the tubes

Infection
Endometriosis
Occasional fibroid tumors

What hormones control sexual desire in women?

Both psychic and local sensory stimulation are necessary for satisfactory performance

Sexual desire in female affected by estrogen and testosterone levels, therefore desire may be greater a few days before ovulation

________ ________ is mediated by parasympathetic nerves that release nitric oxide from their nerve ending on smooth muscle.

clitoral engorgement

Parasympathetic stimulation also increases secretion from __________’s glands

Bartholin's

Impotence in a male is lack of ________, but in women it's lack of ________.

arousal ; lubrication

both are controlled parasympathetically

What are the phases of sexual response? (5)

Desire

Excitement

Plateau

Orgasm

Resolution

Bodily changes for both sexes during the excitement phase? For women? For men?

Heart rate and blood pressure increase, body muscles tense, sexual flush occurs, nipples become erect, genital and pelvic blood vessels become engorged, and involuntary and voluntary muscles contract.

The vagina lengthens and widens, the clitoris swells and enlarges, breasts increase in size, the labia swell and separate, the vagina becomes lubricated

The penis becomes erect, the scrotum thickens, and the testes rise closer to the body. Erection

Bodily changes for both sexes during the plateau phase? For women? For men?

Breathing rate, heart rate, and blood pressure further increase, sexual flush deepens, and muscle tension increases. Sense of impending orgasm.

The clitoris withdraws, the Bartholin’s glands lubricate, the areolae around nipples become larger, the labia continue to swell, the uterus tips to stand high in the abdomen, and the “orgasmic platform” develops

The ridge of the glans penis becomes more prominent, the Cowper’s glands secrete preejaculatory fluid

True or false: there is an anatomical G-spot?

Uh, false.

Bodily changes for both sexes during the orgasm phase? For women? For men?

Heart rate, breathing, and blood pressure reach their peak, sexual flush spreads over the body, and there is a loss of muscle control (spasms).

The uterus, vagina, anus, and muscles of the pelvic floor contract 5 to 12 times at 0.8-second intervals.

Ejaculation occurs (contractions of the ejaculatory duct in the prostate gland cause semen to be ejected through the urethra and penis

Define "multiple orgasms"

Women can have orgasm, move back into plateau stage, and achieve another orgasm

Some males can achieve multiple organisms, although later ones are often without ejaculation.

Bodily changes during the resolution phase.

Basically, everything goes back to normal.

normal size and position; the vagina relaxes; the cervix opens to help semen travel up into the uterus—closing 20–30 minutes after orgasm; and the uterus lowers into the upper vagina (location of semen after male orgasm during penile–vaginal intercourse).

What happens at the very beginning of pregnancy?

Fertilization of ovum, transport of zygote and implantation of blastocyst

Primary oocyte (2N) undergoes meiosis shortly before ovulation. One polar body (with its 23 chromosomes) is expelled from the nucleus leaving a secondary oocyte (N) with 23 unpaired chromosomes.

At ovulation, the corona radiata is expelled from the ovary and the fallopian tube picks up the egg (weak current created by cilia of fallopian tubes)

Where does fertilization occur?

In the fallopian tubes

How long does the trip down the fallopian tube take?

3 – 4 days are required

Where does the first cell division occur?

in the fallopian tubes so that it is a blastocyst by the time it gets to the uterus

the fallopian tube is contracted right after ovulation and won't open until the corpus luteum has secreted enough progesterone to relax the smooth muscle

The fallopian tube ___________ provides nutrients to the zygote

secretions

What are the steps of implantation?

It remains free in the uterine cavity for another 3 – 4 days

About 7 days after ovulation, trophoblast cells on the surface secrete proteolytic enzymes that digest and liquefy adjacent endometrium.

Within a few days, the blastocyst has invaded and implanted in the endometrium

The nutrients from the digested cells are activity transported as substrates for the rapid growth of the blastocyst.

Discuss placental development

Fetal side: Trophoblast cells form cords. Capillaries grow into the cords from the vascular system of the embryo. Blood flow begins by day 16 after fertilization. Cords continue to grow, branching profusely, creating the placental villi.

Maternal side: Sinuses develop that are perfused by maternal blood, surround the fetal cords.

The blood from the two do NOT mix and remain separated by several cell layers

Describe the blood supply of the placenta

Two umbilical arteries (unsaturated blood) arising from the internal iliac arteries provide blood to the placenta and it returns by a single umbilical vein (saturated blood).

Discuss placental permeability to oxygen and transport of oxygen

Oxygen diffuses from maternal blood through placental membranes and into fetal blood, driven by a pressure gradient

Mean PO2 for blood in maternal sinuses ~50 mm Hg

Mean PO2 in venous end of fetal capillaries ~30

Several factors assist in the diffusion of the oxygen

What factors assist in diffusion of oxygen into the placenta?

Fetal hemoglobin has a greater affinity for oxygen than adult hemoglobin (20 – 50 percent more oxygen at those levels)

Concentration of fetal hemoglobin is 50% greater than that in maternal blood (higher oxygen content)

How many trucks do you have AND how much is in them?

Delivering bread to the 7-11

The Bohr effect (effect of PCO2 on hemoglobin oxygen dissociation curves)

High fetal PCO2 diffuses into the maternal blood.

Is fetal hemoglobin identical to adult hemoglobin?

No - it has a greater affinity for oxygen and it's more highly concentrated - aka it's better and there's more of it

Adding the CO2/Bohr effect makes fetal hemoglobin _____ effective.

more

By what mechanisms do metabolic substances move into fetal cells?

Carbon dioxide diffuses readily and rapidly

Transport of metabolic substances (e.g. glucose, amino acids) is similar to transport in other areas of the body

Glucose – facilitated diffusion

Fatty acids – simple diffusion

Electrolytes – both simple diffusion and active transport

Diffusion gradients favor the movement of nonprotein nitrogenous compounds (e.g. urea, uric acid, creatinine) from the fetal to the maternal blood

What is hCG?

How long after fertilization is hCG produced?

HCG is a glycoprotein produced by trophoblast cells beginning 8 – 9 days after fertilization

What is the function of hCG?

Binds to the LH receptors on cell of corpus luteum, continuing the support of the corpus luteum and preventing the otherwise expected involution.

The hCG allows the corpus luteum to continue its secretion of large amounts of progesterone and estrogen.

The hCG also binds to LH receptors in the Leydig cells of male embryos, stimulating the testosterone secretion necessary for the differentiation of the male sex organs

What are trophoblastic cells?

estrogen and progesterone are produced, but not de novo. They are metabolized from androgenic steroids from the mothers and fetal adrenal.

How much higher is estrogen during pregnancy?

What physical changes happen to a woman because of the higher estrogen?

High levels of estrogen (30 times normal late in pregnancy)

Enlargement of the mother’s uterus

Enlargement of the mother’s breast with growth of the ductile structure

Enlargement of the mother’s external genitalia

How much higher is progesterone during pregnancy? What physical effects does this increase have?

Progesterone (10 times normal)

Promotion of storage of nutrients in the endometrial cells, transforming them to decidual cells

Reduction of contractility of uterine smooth muscle

Promotion of nutrient-rich fluids in the fallopian tube to sustain the zygote before implantation

Promotion of development of alveoli of breast

What is HCS? What does it do?

Secreted by the placenta starting in 5th week of pregnancy

Specific function unknown but activity similar to growth hormone

Reduces insulin sensitivity of tissues

Part of the cause of gestational diabetes

Decreases glucose utilization

Lipolysis with release of fatty acids from stores

What happens to the anterior pituitary during pregnancy?

Anterior pituitary –

Enlarges 50 % during pregnancy

Increased production of corticotropin, thyrotropin and prolactin over baseline

Almost complete suppression of FSH and LH (due to high estrogen and progesterone levels from the placenta)

What happens to corticosteroid secretion during pregnancy?

Glucocorticoids are moderately elevated throughout

Twofold increase in aldosterone

Estrogen and aldosterone together promote sodium retention

The body is preparing for fluid loss

What changes occur in a pregnant woman's thyroid?

Hyperplasia of pregnancy up to 50% with corresponding increase in thyroxine

hCG has a thyrotropic effect and there is a second hormone from the placenta called human chorionic thyrotropin

Increase in _______ hormone causes a loss of calcium from the bones during pregnancy to keep serum calcium normal for the baby.

parathyroid

What happens to a woman's parathyroid during pregnancy?

Hyperplasia, especially if diet is low in calcium

This promotes osteoclastic activity to keep serum calcium normal for the use of the baby

This increases during lactation because the loss of calcium in the milk

What is relaxin and where does it come from?

The corpus luteum of the ovary and the placenta secrete another substance.

Relaxin is stimulated by increased hCG levels

Polypetptide with MW of 9000.

Relaxes the ligaments of the symphysis pubis in rats and pigs, but little effect in women. Same effect including relaxation of other pelvic ligaments achieved in humans with high estrogen levels.

Debate whether softening of the cervix is due to relaxin

Response of the mother's body to pregnancy

Increase in size of internal and external sexual organs

Edema, acne, masculine or acromegalic features

Weight gain, most during last two trimesters

Increased desire for food – hormonal effect and loss of substrates.

Basic metabolic rate increased about 15% during latter half of pregnancy

How much weight gain and where are expected during a normal pregnancy?

Fetus – 7 pounds

Amniotic fluids and placental tissues – 4 pounds

Uterus – 2 pounds

Breasts – 2 pounds

Retention of fluids – 6 pounds

Fat accumulation – 3 pounds

What causes increased metabolism during pregnancy?

Due to increased thyroxine, adrenocortical hormones and sex hormones

Increased heat production due to increased energy to move mass

Changes in maternal nutrition during pregnancy

Does not absorb sufficient protein, calcium, phosphates and iron during last months of pregnancy.

Uses body stores

Supplemental vitamins, calcium, iron and high protein diet is needed

What happens to cardiac output up to the 27th week of pregnancy?

Increase in cardiac output of 30 – 40% up to 27th week and then it drops to a little above normal during the last 8 weeks. Mechanism for this unclear

Blood volume of mother is 30% above normal due to fluid retention due to hormones. Bone marrow also kicks

How much above normal is blood volume during pregnancy?

1-2 liters

How are serum protein levels affected by pregnancy?

Serum proteins drop by ~1 gm/dL, largely due to drops in albumin level to 2.2 to 2.8 g/dL

Serum fibringogen and many clotting factors are mildly elevated. Prothrombin (PT) and partial thromboplastin times (PTT) are shortened but clotting and bleeding times remain normal

Shortly before birth, oxygen demand increases by _____%. Ventilation per minute _________s, and PaCO2 ________s

20%

increases, decreases

Changes in urine output during pregnancy

Volume slightly increased

Reabsorption of sodium, chloride and water is increased by up to 50% due to hormone effects

Working against that, the glomerular filtration rate increases as much as 50% which tends to increase the loss of water and sodium

Increased GFR

Discuss amniotic fluid make-up and turnover rate

Volume 500 – 1000 cc.

Water is turned over once every three hours; electrolytes turned over once every 15 hours

~50% of the turnover is amniotic; 50% fetal

What are the main events of partuition?

Increased irritability and uterine contractility

Stretch of the uterus and cervix increases uterine contractility

Onset of labor – positive feedback theory

Lactation

What hormone increases contractility?

Progesterone level reaches a maximal level (reduces contractility) but estrogen levels continue to climb (increases contractility)

What hormone causes uterine contractions?

Oxytocin from the posterior pituitary can cause uterine contractions

_______ receptors on the cells of uterine smooth muscle increase during the final weeks of pregnancy.

oxytocin

What factors contribute to uterine contractility?

Size of the fetus and movement of the fetus

Cervical distention can stimulate contraction in the body

Cervical distention elicit reflexes that increase oxytocin levels, released from the posterior pituitary

What are Braxton-Hicks contractions?

Beginning in the 6th month, the uterus undergoes periodic slow rhythmic contractions called Braxton-Hicks contractions

They increase in frequency and intensity throughout labor until they begin to cause increasing levels of contraction and irritability and labor ensues

What hormones prepare the breast for lactation? What hormone causes milk formation? What hormone causes milk let-down?

High levels of estrogen (ductile growth) and progesterone (alveolar growth) prepare the breasts for lactation

Milk formation caused by prolactin, from anterior pituitary, but the effects of the high levels of prolactin during pregnancy are blocked by the high concentrations of estrogen and progesterone from the placenta; therefore no milk until the placenta is delivered and the levels fall rapidly

Oxytocin causes mechanical release of milk

Prolactin is regulated by prolactin-inhibitory factor (PIF) believed to be dopamine. Hypothalamic control is ___________, not stimulatory.

inhibitory

What are the components of human milk? Why is colostrum so important?

88.5% water

3.3% fat

6.8% lactose (50% greater than cow’s milk)

1.3% protein (less than 50% of cow’s milk)

May secrete 2-3 grams of calcium phosphate a day into the milk. A diet rich in calcium is necessary to prevent calcium depletion.

Up to 1.5 liters per day (single child); greater if multiple children

Multiple antibodies are transferred, as well as neutrophils and macrophages

During breast feeding, the ___________ cycle is interrupted so that ovulation and menstruation do not occur for several months after delivery. The mechanism is unknown

ovarian

Physiology Lecture 13 - 9/22/2011

Physician Assistant Pha 529 with Steffes at Methodist College

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