Life Is Precious. Uterine (Menstrual) Cycle Cyclic changes of the endometrium Regulated by cyclic...

Life Is Precious

Uterine (Menstrual) Cycle

• Cyclic changes of the endometrium

• Regulated by cyclic production of estrogens and progesterone

• FSH and LH regulate the production of estrogens & progesterone

• Cycle=28 days • Ovulation=occurs day 14

Stages of the Uterine (Menstrual) Cycle• Menstrual phase

– Days 1–5– Functional layer of the endometrium

is sloughed – Bleeding occurs for 3–5 days– By day 5, growing ovarian follicles

are producing more estrogen

Uterine (Menstrual) Cycle

• Proliferative stage – Days 6–14– Regeneration of functional layer of

the endometrium– Estrogen levels rise– Ovulation occurs in the ovary at the

end of this stage

Uterine (Menstrual) Cycle

• Secretory stage – Days 15–28– Progesterone Levels rise and

increase the blood supply to the endometrium

– Endometrium increases in size and readies for implantation

Uterine (Menstrual) Cycle

• Secretory stage (continued)– If fertilization does occur

• Embryo produces a hormone that causes the corpus luteum to continue producing its hormones

– If fertilization does NOT occur• Corpus luteum degenerates as LH blood

levels decline

Fluctuation of Gonadotropin Levels

Figure 16.12a

Fluctuation of Ovarian Hormone Levels

Figure 16.12b

Ovarian Cycle

Figure 16.12c

Uterine (Menstrual) Cycle

Figure 16.12d

Hormone Production by Ovaries• Estrogens: Produced by follicle cells

• Cause secondary sex characteristics• Development of breasts• Increased hair• Increase in fat beneath the skin,

particularly in hips and breasts• Widening and lightening of the pelvis• Onset of menses (menstrual cycle)

Hormone Production Ovaries• Progesterone

– Produced by corpus luteum– major effects

• Helps maintain pregnancy• Prepare the breasts for milk production

Developmental Stages of Ovarian Follicle

Figure 16.7

Mammary Glands

• Present in both sexes, but only function in females– Modified sweat glands

• Function is to produce milk• Stimulated by sex hormones

(mostly estrogens) to increase in size

Mammography• X-ray examination that detects breast

cancers too small to feel• Recommended every 2 years for

women between 40 and 49 years old and yearly thereafter

Stages of Pregnancy & Development: Fertilization

• Oocyte viable 12-24 hrs after ovulation• Sperm viable 24-48 hrs after ejaculation• Fertilization occur? Intercourse must

occur ≤ 2 days before ovulation & ≤ 24 hours after

• Sperm cells must make their way to the uterine tube for fertilization to be possible

Mechanisms of Fertilization

• Acrosomal Reaction: Sperm use break down enzymes to digest holes in oocyte membrane

• Membrane receptors on oocyte pull in the head of the first sperm cell to make contact

Mechanisms of Fertilization

• Oocyte membrane does not permit a 2nd sperm head to enter—unless?

• Fertilization occurs when the genetic material of a sperm combines with that of an oocyte to form a zygote

The Zygote

• First cell of a new individual! Carries as much genetic info as 50 sets of the 33-volume Encyclopedia Britannica!

• The result of the fusion of DNA from sperm and egg

• The zygote begins rapid mitotic cell divisions

• The zygote is in uterine tube, moving toward the uterus

Cleavage

Three to 4 days after ovulation, the embryo reaches the uterus and floats freely for 2–3 days

Figure 16.15, step 1

Cleavage

Secondaryoocyte

Ovulation Uterus

Endometrium

Uterine tube

Ovary

Figure 16.15, step 2

Cleavage

Fertilization

Secondaryoocyte

Ovulation Uterus

Endometrium

Uterine tube

Zygote(fertilizedegg)

Ovary

(a)

(a)

Figure 16.15, step 3

Cleavage

Fertilization

Secondaryoocyte

Ovulation Uterus

Endometrium

Uterine tube

Zygote(fertilizedegg)

Earlycleavage4-cell stage

Ovary

(a) (b)

(a)(b)

Figure 16.15, step 4

Cleavage

Fertilization

Secondaryoocyte

Ovulation Uterus

Endometrium

Uterine tube

Zygote(fertilizedegg)

Earlycleavage4-cell stage

Morula

Ovary

(a) (b) (c)

(a)(b) (c)

Figure 16.15, step 5

Cleavage

Fertilization

Secondaryoocyte

Ovulation Uterus

Endometrium

Uterine tube

Blastocystcavity

Zygote(fertilizedegg)

Earlycleavage4-cell stage

Earlyblastocyst

Morula

Ovary

(a) (b) (d)(c)

(a)(b) (c)

(d)

Figure 16.15, step 6

Cleavage

Fertilization

Secondaryoocyte

Ovulation Uterus

Endometrium

Uterine tube

Blastocystcavity

Inner cellmass

Trophoblast

Zygote(fertilizedegg)

Earlycleavage4-cell stage

Earlyblastocyst

Late blastocyst(implanting)

Morula

Ovary

(a) (b) (d) (e)(c)

(a)(b) (c)

(d)

(e)

Developmental Stages

• Morula: Stage before cells differentiate

• blastocyst stage (100 cell stage) embryo implants in endometrium

• Cells differentiate into muscular, nervous, skeletal cells.

Embryo Approx 18 Days

Figure 16.16

Development After Implantation

• “Embryo”—until ninth week• “Fetus”—beginning in ninth week

of development • Amnion—fluid-filled sac that

surrounds the embryo • Umbilical cord

– Blood-vessel containing stalk of tissue – Attaches the embryo to the placenta

The 7-week Embryo

Figure 16.17

Functions of the Placenta

• Forms a barrier between mother and embryo (blood not exchanged)

• Delivers nutrients & oxygen, Removes waste

• Produces hormones & takes over for corpus luteum by producing– Estrogen– Progesterone

Photographs of a Developing Fetus

Figure 16.18a

Effects of Pregnancy on the Mother• Pregnancy: period from conception until

birth

• Anatomical changes– Enlargement of uterus• Accentuated lumbar curvature • Relaxation of pelvic ligaments &

pubic symphysis due to production of relaxin

Physiological Effects of Pregnancy on the Mother

– Gastrointestinal system• Morning sickness is common due to

elevated progesterone & estrogens• Heartburn common: organ crowding by the

fetus• Constipation caused by declining motility of

digestive tract

Physiological Effects of Pregnancy on the Mother

– Urinary system• Kidneys have additional burden and

produce more urine• The uterus compresses the bladder,

causing stress incontinence

•Cardiovascular system• Blood volume increases by 25–40%• Blood pressure and pulse increase• Varicose veins are common

Childbirth (Parturition)

• Labor—the series of events that expel the infant from the uterus– Rhythmic, expulsive contractions

• Braxton Hicks: False labor contractions are weak, irregular uterine contractions

Childbirth (Parturition)

• Initiation of labor– Estrogen levels rise– Uterine contractions begin– Placenta releases prostaglandins– Pituitary releases oxytocin– Combination of these hormones

oxytocin and prostaglandins produces contractions

Stages of Labor

• Dilation– Cervix becomes dilated– Full dilation=10 cm– Uterine contractions begin and

increase– Cervix softens and thins– The amnion ruptures (“breaking the

water”)– Longest stage at 6–12 hours

Figure 16.20 (1 of 3)

Stages of Labor

Stages of Labor

• Expulsion– Infant passes through cervix &

vagina– Can last as long as 2 hours, but

typically is 50 minutes in the first birth and 20 minutes in subsequent births

– Normal delivery is head first – Breech presentation is buttocks-first

Stages of Labor

Figure 16.20 (2 of 3)

Stages of Labor

• Placental stage– Delivery of the placenta– Within 15 minutes after birth of

infant– Afterbirth—placenta and attached

fetal membranes – All placental fragments should be

removed to avoid postpartum bleeding

Stages of Labor

Figure 16.20 (3 of 3)

Developmental Aspects Reproductive System• Menarche—first menstrual period • Menopause—a whole year has

passed without menstruation– Ovaries stop functioning as endocrine

organs– Childbearing ability ends

• There is a no equivalent of menopause in males, but there is a steady decline in testosterone

A Closer Look: Contraception• Birth control pill: (most-used contraceptive)

– Relatively constant supply of ovarian hormones from pill is similar to pregnancy.

– can work in one of three ways:1) It can prevent ovulation (releasing an

egg from the ovary)2) It can cause the mucus in the cervix to

change so that if sperm reach the cervix, they are not allowed to enter,

BCP3) It can irritate the lining of the

uterus – chemical abortion – if first two actions fail, & woman

does become pregnant, the tiny baby will die before the ability to attach to the lining of the uterus

– Although the primary mechanism of this BCP’s action is inhibition of ovulation, other alterations include changes in the cervical mucus, which increase the difficulty of sperm entry into the uterus, and changes in the endometrium which reduce the likelihood of implantation.[5] 

(PDR + FDA)

Contraception: Morning after pill

A Closer Look: Contraception• Morning-after pill (MAP)

– Taken within 3 days of unprotected intercourse

– Disrupts normal hormonal signals to the point that fertilization is prevented

– U18 ruling by Judge Edward Korman 

1. Levonelle 2 (morning-after pill) two tablets each containing 750µg of levonorgestrel that are taken as a single dose. Patient receives 1,500µg, 50 times the normal dose of b.c.p

2. Patients who have used this type of pill and who nevertheless become pregnant should be evaluated for ectopic pregnancy.

MAPSide Effects: • Lack of Menstrual Cycle• Passing Large Blood Clots• Nausea/Vomiting• Ectopic Pregnancy

A Closer Look: Contraception• Other hormonal birth control

devices cause cervical mucus to thicken– Minipill: progesterone only tablet– Norplant (rods placed under the

skin)

A Closer Look: Contraception• Intrauterine device (IUD)

– Plastic or metal device inserted into uterus

– Prevents implantation of fertilized egg

• Sterilization– Tubal ligation (females)—cut or

cauterize uterine tubes– Vasectomy (males)—cut or cauterize

the ductus deferens

A Closer Look: Contraception• Natural Family Planning(NFP)

(fertility awareness)—avoid intercourse during period of ovulation or fertility– Record daily basal temperature

(body temperature rises after ovulation) – Record changes in pattern of

salivary mucus

A Closer Look: Contraception• Barrier methods

– Diaphragms– Cervical caps– Condoms– Spermicidal foams– Gels– Sponges

A Closer Look: Contraception• Abortion—termination of

pregnancy• Miscarriage—spontaneous

abortion common & frequently occurs before pregnancy is known. RU486 or “abortion pill”—induces miscarriage during first 7 weeks of pregnancy

Some Contraceptive Devices

Figure 16.21 (2 of 2)

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Figure 16.21 (1 of 2)