Human Bio Ch. 2

Broad Ligament

Double layer of peritoneum that supports uterus, uterine tubes, and ovaries

Anteverted

Uterus position for 75% of females

Retroverted

Anteflexed

Retroflexed

Oogonia

Starting form for oocytes; peak at ~7 million by 5th month of gestation

Primary Oocytes

Form after oogonia begin meiosis I (end of 7th month), then arrest in prophase I

Atresia

Natura oocyte degeneration before birth/throughout life; reduces to ~1 million eggs at birth

Ovarian Follicles

Oocyte + supportive cells (theca and granulosa cells)

Theca and Granulosa Cells

Produces estrogen

Avg. number of ovulations in a lifetime

450

Follicle Stimulating Hormone (FSH)

Stimulates cohort of primordial follicles to start maturation every cycle

Graafian Follicle

The only follicle that fully matures and ovulates after FSH

Luteinizing Hormone (LH)

LH surge triggers ovulation

Corpus Luteum

Ruptured follicle after ovulation; secretes progesterone/estrogen to maintain uterine lining for implantation

Menstruation Trigger

Corpus luteum degenerates → progesterone/estrogen drop → becomes corpus albicans

Fimbriae

Finger projections on fallopian tube that capture secondary oocyte after ovulation

Where fertilization occurs

Distal 1/3 of tube (ampulla)

Zygote

Fertilized ovum (mature egg) with 2n = 46 chromosomes

Oogenesis

Process of forming ova; begins before birth until menopause

Ova

Female gametes that are surrounded by follicle cells that release estrogen

Viability Period of Released Secondary Oocyte

12-24 hours

Fertilization

Completes meiosis II and begins cleavage; fertilized ovum divides and conserves 23 pairs of chromosomes

Meiosis I

Homologous chromosomes separate → 2 haploid cells with duplicated chromosomes

Meiosis II

Sister chromosomes separate → 4 total genetically unique haploid cells

Polar Bodies

Non-functional extra cells from 1st meiotic division and 2nd meiotic division (fertilization)

Metaphase II Arrest

Preserves secondary oocyte for ovulation

Menstrual Cycle Pathway

GnRH (hypothalamus) → stimulates ant. pituitary → AP release FSH and LH → FSH triggers follicle development → estrogen and LH surge trigger ovulation → corpus luteum secretes progesterone and estrogen

Endometrium during Menstrual Cycle

Menstrual phase → proliferative phase → secretory phase

Menstrual Phase

Progesterone/estrogen drops → spiral arteries constrict → outer functional layer sheds

Proliferative Phase

Estrogen signal → functional layer starts regenerating → glands are straight and narrow

Secretory Phase

Functional layer thickens → coiled uterine glands secrete glycogen-rich fluid → maintained by progesterone

Follicular Phase

Estrogen levels rise → fallopian tubes move closer to ovary, fimbriae beat faster, ciliated cells increase in fimbriae → egg capture success increase

Egg vs Sperm

Egg is larger with more mitochondria, while sperm can survive for up to 5 days in female reproductive tract

Acrosomal Reaction

Sperm head (acrosome) contains enzymes that digest zona pellucida

Cortical Reaction

Cortical granules inside egg release after fertilization and harden zona pellucida

Zona Pellucida

Egg’s outer glycoprotein layer; changes electrical charge or hardens after sperm contact

Post Menopause Changes

Estrogen drops → increases osteoporosis risk

Zygote Development

Cleavage → morula → early blastocyst → hatching blastocyst → implantation

Trophoblast

Outer layer of implanted blastocyst; differentiates into cytotrophoblast and syncytiotrophoblast

Cytotrophoblast

Maintains implanted blastocyst cellular structure

Syncytiotrophoblast

Secretes enzymes to anchor blastocyst to uterine tissue

Bilaminar Germinal Disc

Made from hypoblast and epiblast; later develops into germ layers

Placenta

Made from maternal tissue and outer layer of trophoblast (chorion); site of nutrient, gas, and waste exchange

Immune System Rejection Prevention

Trophoblast secretes suppression enzymes and lacks surface proteins needed to show antigens

Placenta Hormone Production

Replaces progesterone/estrogen production by corpus luteum after fully forming by end of 1st trimester

Placenta Structure

Villi (anchor), spiral arteries, intervillous space

Amniotic Sac and Fluid

Strong membrane containing fluid for free movement and cushioning

Preeclampsia

Abnormal placental development that causes hypertension and organ damage (kidney and liver)

Ectopic Pregnancy

Implantation occurs outside the uterus (tubal, interstitial, ovarian, cervical), resulting in non-viable and potentially fatal pregnancy

Abdominal Pregnancy and Lithopedion

Implantation occurs in peritoneum, ovary, or intestines; fetus can calcify into “stone baby”

Germinal Period

Weeks 0-2; from fertilization to embryo establishment in uterus

Embryonic Period

Weeks 3-8; critical period containing organogenesis and formation of neural tube, heart, limbs, etc.

Fetal Period

Weeks 9-birth; growth/refinement of organs and rise in viability after ~24 weeks

Primitive Streak

Forms around week 3; forms in epiblast and where epiblast cells migrate through during gastrulation

Trilaminar Embryonic Disc

Formed after gastrulation; contains endoderm, mesoderm, and ectoderm

Endoderm

Inner layer → epithelial lining of digestive and respiratory organs, glands

Mesoderm

Middle layer → muscle, bone, connective tissue, blood, kidneys, gonads

Ectoderm

Outer layer → skin, nervous system