Frolich, Human Anatomy, Reproduction, Early Dev., Pregnancy Reproduction, Early Development,...

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Frolich, Human Anatomy, Reproduction, Early Dev., Pregnancy

Reproduction, Early Development, Pregnancy

l 1. From 2 cells• …a 3-layer embryo• …a yolk sac, amniotic cavity, chorionic

cavity• …a placenta

l 2. Pregnancy and Childbirth • Changes to female anatomy• Labor and birth

Ovulation 1o oocytes arrested in

Meiosis I in female fetus After puberty, 1 primary

oocyte/month completes Meiosis I as follicle matures

Follicle ruptures--ATTENTION--CELL LOOSE IN CELOM

Oocyte enters Fallopian tube If fertilization occurs, Meiosis

II occurs and oocyte becomes ovum

Ovulation and Meiosis

Fig. 24.15

Spermatogenesis Sperms form in walls of

seminiferous tubules Spermatogenic cells within

sustentacular cells Meiosos proceeds as

spermatocytes move towards lumen (4 sperm from each spermatocyte)

Seminiferous tubulerete testis head/body/tail epididymis vas deferens (through spermatic cord around bladder) urethra

Fig. 24.3

Sustentacular cells Form thick epithelial

lining of seminiferous tubules

Tight junctiones between keep sperm proteins from entering bood

Produce testicular fluid which helps move sperm

Concentrate testosterone to stimulate sperm production

Produce inhibin which slows sperm production Fig. 24.4

First week of development

Oocyte(fertilization)zygote4-cell stage (2 days) morula (ball)blastocysteinner cell mass (embryo)

Trophoblast (extraembronic membranes)

From oocyte to blastocyst

Fig. 3. 3

Implantation

Endometium ready for implantation Blastocyst implants with ICM against uterine wal Ectopic pregnancy--implantation outside built-up

endometrium (potential for bleeding since embryo stimulates vascularization)

Endometrium Two layers

– Stratum basalis– Stratum functionalis

Stratum functionalis builds up each month in response to ovarian hormones

Uterine glands secrete glycoproteins--nutrients for potential zygote--into uterine cavity

At menstruation, functional layer self-digests, spiral arteries kink and constrict so cells die.

Just before menstrual flow starts, spiral aa. Open wide, capillaries burst and functional layer sloughs off.

Fig. 24.18

Endometrium and menstrual

Fig. 24.19

Endometrium and menstrual

Menstrual Phase (Days 1-5): Sloughed Functional layer of endometrium expelled through vagina as menstrua flow

Proliferative phase (Days 6-14): In response to estrogen from growing ovarian follicle, new functional layer elaborates

Ovulation (about Day 14) Secretory phase (Days 15-28):

– Spiral aa. Elongate and coil– Uterine glands secret glycoproteins– More estrogen (and progesterone) from

corpus luteum If pregnancy, secretory phase continues

due to embryonic estrogen production If no pregnancy, corpus luteum

degenerates, estrogen drops leading to menstruation

Implantation with ICM towards uterine wall Trophoblast

– Cytotrophoblast (cells around ICM)– Synctiotrophoblast (synctium of cells that becomes placenta)

Meanwhile…back in the embryo

Fig. 24.25

Placenta formation

Lacunae form within synctiotrophoblast--maternal blood fills these spaces

Vili form with embryonic capillaries down middle

Fig. 24.25

Placenta formation

Villi bathed in maternal blood in lacunae--exchange of nutrients, O2, CO2

After 13 weeks, full placenta--pancake-shaped organ.Fig. 24.25

Other extraembryonic tissues Cellular trophoblast forms

amnion, yolk sac Fetal cells shed into

amniotic cavity which fills with fluid from fetal kidneys extreted through ureter, bladder, urethra

Amniocentesis--sample of amniotic fluid taken with hypodermic needle

Part of yolk sac “sucked” into embryo to form endermic bladder Fig. 3.4

Embryo proper

ICM forms hypoblast (yellow--becomes endoderm) and epitblast (blue--becomes ectoderm)

See handout for all adult derivatives of embryonic tissues--HOW FAR WE’VE COME!!

Fig. 3. 4Animated movie of fetal deveopmenthttp://www.cvillepregnancy.org/fetal.html

Pregnancy--changes in female anatomy Shift in organs

– Bladder, rectum pushed superiorly, squeezed--change in urination, defecation patterns

– Stomach compressed--eat more often, less at each meal

– Immune response may change appetite to avoid possible poisons for fetus

Postural changes to compensate for anterior weight

Breasts enlarge--first milk production

Birth Stage 1. Dilation Stage

– Ligaments loosen– Cervix dilates

Stage 2. Expulsion– Baby moves through pelvic girdle--head is rotated

90 degrees– Floor of pelvis

Kegel exercises Perineal support Avoid ripping or episiotomy

– Baby skull--sutures not fused, bones can be slide on top of each other giving pointed look

Stage 3. Placenta.– Detaches and is expulsed within one hour.

Fig. 24.27

Frolich, Human Anatomy, Reproduction, Early Dev., Pregnancy Reproduction, Early Development,...

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