Reproductive System

Reproductive System

• does NOT function continuously —> becomes active at _____

• male and female share the SAME 4 tasks:

1. Form specialized cells for sexual reproduction called _____

• _____ in males 

• _____ (eggs) in females 

2. Bring gametes from male and female together through sexual intercourse (copulation)

3. Combine genetic info contained w/in gametes through _____

• Zygote is formed when sperm and egg fuse 

• Zygote is 1st cell of new individual and all body cells arise from it 

4. Support development of fetus (_____ ) and birth of baby (_____ )

puberty, gametes, sperm, ova, fertilization, gestation, parturition

Gonads and Accessory Reproductive Organs 

• Male and female reproductive structures are _____ structures

  • Share a common origin during development 

  • Ex. male testes and female ovaries, or male penis and female clit 

• Primary sex organs (_____ ) → testes and ovaries produce 2 products: 

  • Gametes → sperm and ova 

    • Formed by cell division (meiosis) 

  • Sex hormones (_____ hormones) → testosterone + estrogen and progesterone 

    • Vital in development and function of reproductive organs and other organs/tissues, sexual behaviour, sexual drives 

• Accessory reproductive organs = ducts, glands, and external genitalia

homologous, gonads, steroid

Hypothalamic-_____ -_____ (HPG) Axis 

• Production of gametes and sex hormone is regulated by sequence of hormonal events

• Involves: hypothalamus, _____ pituitary gland, and gonads 

  • Known as HPG axis 

  • Involves interacting hormones = GnRH, FSH, LH, testosterone, and _____

pituitary gonadal, anterior, inhibin

HPG Hormones

• _____ -releasing hormone (GnRH) 

  • Released from _____ → reaches anterior pituitary cells via _____ portal system 

• _____ -stimulating hormone (FSH) + _____ hormone (LH) 

  • Gonadropins released from _____ _____

• Sex hormones → testos + estrogen and proges 

  • Act at target tissues in body 

  • Exert _____ feedback on hypothalamus and anterior pituitary 

• Inhibin 

  • Released from _____ of both female and male 

  • Exerts NEGATIVE feedback on _____ release from anterior pit

gonadotropin, hypothalamus, hypophyseal, follicle, luteinizing, anterior pituitary, negative, gonads, FSH

Activation of HPG Axis at Puberty 

• Puberty = when reproductive organs grow to adult size and become functional 

  • Earliest time reproduction is possible 

• Steroidal sex hormones can _____ GnRH secretion 

• BEFORE puberty → low levels of circulating steroidal sex hormones are enough to suppress secretion of GnRH by hypothalamus 

• Puberty approaches → hypothalamus becomes LESS _____ to inhibition by sex hormones 

  • Hypothalamus releases GnRH in pulse-like manner 

suppress, sensitive

Activation of HPG Axis at Puberty Cont’d

• Anterior pituitary releases FSH and LH in response to increased GnRH levels 

• FSH and LH → stimulate gonads to release more _____ _____ from gonads 

• Threshold for inhibition of GnRH continues to _____ = results in more and more release of sex hormones 

• Sex hormones are released until _____ pattern of hormone interaction is achieved

sex hormones, rise, adult

Meiosis

• Nuclear division that occurs ONLY in _____

• Same process for males and females 

• Sexual reproduction CANNOT take place without meiosis 

  • Reduces number of chromosomes in gametes by _____ so zygotes does not end up with TWICE as many chromosomes

gonads, half

Meiosis - Terms

• _____ _____ = cell’s DNA is replicated during interphase 

  • Each chromosome has 2 sister chromatids that are joined together by centromere 

  • DNA coils and condenses → makes chromosomes _____ when viewed through light microscope 

• _____ pairs of chromosomes = one member of each pair is from father (_____ chromo) and one from mother (_____ chromo) 

  • Look alike and carry same genes that code for same traits

sister chromatids, visible, homologous, paternal, material

MALE REPRODUCTIVE - Anatomy

• Testes = sperm-producing male gonads that are in scrotum 

• Sperm is delivered to body through system of DUCTS: 

1. _____

2. _____ _____

3. _____ duct 

4. _____

• Accessory sex glands → seminal glands, prostate, and bulbo-urethral glands

epididymis, ductus deferens, ejaculatory, urethra

MALE REPRODUCTIVE - Scrotum

• Sac of skin and superficial fascia 

• Hangs outside _____ cavity at root of penis 

• Contains paired testes 

  • 3°C _____ than core body temp 

  • this temp is needed for sperm production

abdominopelvic, lower

MALE REPRODUCTIVE - Testes

• Each testis is surrounded by 2 tunics: 

  • Tunica _____ = OUTER derived from _____

  • Tunica _____ = INNER layer forms _____ capsule 

• Septa (septum) divides testis into 250 lobules → each contains 1 of 4 _____ _____

  • Site of sperm production 

• Sperm is conveyed from seminiferous tubules to straight tubule → _____ testis → _____ ductules → _____

  • Epididymis is made up of head, body, and tail 

• Sperm are stored in _____ until ejaculation

vaginalis, peritoneum, albuginea, fibrous, seminiferous tubules, rete, efferent, epididymis, tail

MALE - Duct System

• Accessory ducts CARRY sperm from _____ to body _____

• Epididymis, ductus deferens, ejaculatory duct, urethra

testes, exterior

Duct System - Epididymis

• Sperm _____ here 

• Head = contains _____ _____ that empty into highly coiled duct of epididymis 

• Also has body and tail 

• Altogether = 6m long 

• _____ sperm enter → pass SLOWLY through (20 days) → finally gain ability to swim 

  • Can be stored several months 

• During ejaculation → epididymis contracts → expels sperm into _____ _____

mature, efferent ductules, nonmotile, ductus deferens

Duct System - Ductus Deferens & Ejaculatory Duct

• Ductus deferens (vas deferens) is 45 cm long 

  • Passes through inguinal canal to pelvic cavity 

  • Expands to form _____

  • Joins duct of _____ _____ to form ejaculatory duct 

• _____ _____ in walls propels sperm from epididymis to urethra 

• _____ = cutting and ligating ductus deferens 

  • Nearly 100% effective form of birth control

ampulla, seminal vesicle, smooth muscle, vasectomy

Male Accessory Glands

Seminal Glands (seminal vesicles) 

• On posterior bladder surface 

• Contains smooth muscle that contracts during ejaculation 

• Produces viscous _____ seminal fluid 

  • Fructose, citric acid, coagulating enzyme (vesiculase), and prostaglandins 

  • Increase sperm _____ of fertility 

  • Yellow pigment fluoresces w/ UV light 

  • Makes up 70% volume of _____

• Duct of seminal gland joins ductus deferens to form _____ duct

alkaline, motility, semen, ejaculatory

Male Accessory Glands

Prostate

• Encircles urethra inferior to bladder 

• Size of peach pit 

• Consists of SMOOTH muscle that contracts during ejaculation 

• Secretes milky, slightly _____ fluid

  • Contains citrate, enzymes, and prostate-specific antigen (PSA) 

  • Plays a role in sperm _____

  • Enters _____ _____ during ejaculation 

  • Makes up 1/3 of semen volume

acid, activation, prostatic urethra

Male Accessory Glands

Bulbo-urethral glands

• Pea-sized glands inferior to prostate 

• Produce thick, clear _____ during sexual arousal 

  • _____ glans penis 

  • _____ traces of acidic urine in urethra

mucus, lubricate, neutralize

Male Physiology

Spermatogenesis 

• Process of _____ male gametes 

• Occurs in _____ _____

• BEGINS at puberty → around 14 years old 

• Adult males make 90 million sperm daily

forming, seminiferous tubules

Male Physiology

Histology of Seminiferous 

• Tubules consists of a thick _____ epithelium surrounding fluid-filled _____

• Contains 4 important types of cells: 

  • _____ (sertoli cells) = large columnar cells act as supporting cells and play role in sperm formation 

  • _____ cells = cells that are surrounded by sustentocytes + give rise to sperm 

  • _____ cells = smooth muscle-like cells surrounding seminiferous tubules that contract to squeeze sperm and _____ _____ through tubules 

  • Interstitial endocrine cells (_____ cells) = produce _____ and some estrogen

stratified, lumen, sustentocytes, spermatogenic, myoid, testicular fluid, leydig, adrogens

Spermatogenesis Summary Events (3 steps)

• Spermatogenic cells give rise to sperm 

• Takes 64-72 days if conditions are hospitable 

• Sperm are UNABLE to swim, but _____ of _____ fluid pushes immotile sperm into _____ → then they gain motility and fertilizing power 

pressure, testicular, epididymis

Spermatogenesis Summary Events (3 steps)

1. _____ of _____ (stem cell) forms 2 spermatocytes 

2. _____

• Spermatocytes form secondary spermatocytes → which form _____

mitosis, spermatogonia, meiosis, spermatids

Spermatogenesis Summary Events (3 steps)

3. _____ → spermatids become SPERM

• Spermatids contain correct haploid chromo number needed for fertilization (n) → are still _____

• Spermiogenesis = streamlining process where spermatid elongates → loses excess _____ → forms a tail 

• Major regions of sperm: 

  • Head = genetic region that includes nucleus and helmet-like _____

    • this contains _____ _____ that enable sperm to PENETRATE egg 

  • Midpiece = metabolic region containing _____ that produce ATP to MOVE tail 

  • Tail = locomotor region that includes _____

spermiogenesis, nonmotile, cytoplasm, acrosome, hydrolytic enzymes, mitochondria, flagellum

Role of Sustentocytes

• Large _____cells (aka sertoli cells) 

• Extend from basal lamina to tubule lumen + surround developing _____

• Sustentocytes contain tight junctions that divide tubule into 2 compartments: 

  • _____compartment = basal lamina to tight junctions 

    • Spermatogonia and _____ _____ located here 

  • _____compartment = internal to tight junctions 

    • Area where _____ active cells and tubule lumen are located

supporting, spermatogonium, basal, primary spermatocytes, adluminal, meiotically

Role of Sustentocytes - Actions

• Provide _____and signals to dividing cells 

• Move spermatocytes and spermatids along to _____

• Secrete _____ _____ (rich in androgens and metabolic acid) into lumen for sperm _____

• Phagocytize faulty germ cells and excess cytoplasm 

• Produce 2 mediators to regulate spermatogenesis: 

  • _____ -_____ _____ (ABP) → keeps _____ levels HIGH to stimulate spermatogenesis 

  • _____ → INHIBIT spermatogenesis by inhibiting FSH release from anterior pit

nutrients, lumen, testicular fluid, transport, androgen-binding protein, testosterone, inhibin

REGULATION of Male System (7 steps)

• Production of gametes and sex hormones is regulated by sequence of _____ events 

• Involves HPG axis + interacting hormones (GnRH, FSH, LH, testos, inhibin)

hormonal

REGULATION of Male System (7 steps)

1. _____ releases GnRH 

2. GnRH binds to anterior pituitary _____ cells, causing them to secrete: 

• _____ and _____

3. FSH stimulates _____ indirectly by stimulating _____ to release _____

• ABP keeps [ ] of testos HIGH near spermatogenic cells → promote spermatogenesis 

4. LH binds to _____ _____ cells (leydig cells) → make them secrete _____

• Rising testos levels trigger spermatogenesis

hypothalamus, gonadotropic, FSH, LH, spermatogenesis, sustentocytes, ABP, interstitial endocrine, testosterone

REGULATION of Male System (7 steps)

5. Testos entering blood stimulates sex organ _____ , development/maintenance of _____ sex characteristics, and _____

6. RISING testos levels feed back on hypothalamus to _____ GnRH and on pituitary to INHIBIT _____ release 

7. Inhibin = released by _____ when sperm count is HIGH 

• Inhibits GnRH and FSH release

maturation, secondary, libido, inhibit, gonadotropin, sustentocytes

MALE Secondary Sex Characteristics

• Features induced in _____ organs by male sex hormones (mainly testosterone) 

• Appearance of pubic, axillary, and facial hair 

• Enhanced growth of hair on chest or other areas 

• _____ enlargements causes deepening of voice 

• Skin thickens and becomes _____

• Bones grow → increase in density 

• Skeletal muscles increase in size and mass 

• Boosts basal metabolic rate 

• Basis of sex drive (_____ ) in males

nonreproductive, larynx, oily, libido

FEMALE REPRODUCTIVE SYSTEM

• MORE complex b/c of pregnancy 

• Ovaries = female _____

  • Produce female _____ (ova) 

  • Secrete female sex hormones, _____ (estradiol, estrone, estriol), and _____

• INTERNAL genitalia = located in _____ _____

  • Include ovaries and duct system (uterine tubes, uterus, and vagina) 

• EXTERNAL genitalia = external_____ _____

gonads, gametes, estrogen, progesterone, pelvic cavity, sex organs

Ovaries

• Paired structures flank the uterus + almond shaped and about twice as large 

• Each ovary surrounded by fibrous _____ _____ → then covered by _____ _____ epithelium OUTER layer 

• OUTER cortex = contains forming _____

• INNER medulla = contains large _____ _____ and nerves

• _____ _____ → tiny sac-like structures embedded in cortex 

  • Contain immature egg (_____ ) encased by 1 or more layers of very diff cells 

  • Each month → a ripened follicles ejects oocyte in event called _____

tunica albuginea, germinal cuboidal, gametes, blood vessels, ovarian follicles, oocyte, ovulation

Female Duct System

• Uterine tube system does NOT have direct contact w/ ovaries 

  • Ovulated oocyte is released into _____ cavity → this is where some oocytes never make it to tube system 

• Tube system: 

  • _____ _____

  • _____

  • _____

peritoneal, uterine tubes, uterus, vagina

Uterine Tubes

• Aka _____ tubes or _____

• Receive ovulated oocyte and are usual site of _____

• Each tube extends from area of ovary to superior region of uterus = 10 cm long 

fallopian, oviducts, fertilization

Uterine Tubes

Regions: 

• _____ → funnel-shaped opening into peritoneal cavity 

  • Margin contains ciliated projections called _____ that drape over ovary 

• _____ → forms half of uterine tube length 

  • Site where FERTILIZATION actually occurs 

• _____ → narrow medial third that empties into superolateral region of uterus

infundibulum, fimbriae, ampulla, isthmus,

Homeostatic Imbalance - _____ Pregnancy

• Oocyte is fertilized in _____ _____ or distal uterine tube and begins developing there 

• Normally abort naturally w/ substantial bleeding

ectopic, peritoneal cavity

Uterus

• Hollow, thick-walled, _____ organ 

• Function = receive, retain, and nourish fertilized ovum 

• Uterine wall (3 layers)

muscular

Uterus Wall Layers (3)

• _____

  • OUTERMOST serous layer (visceral peritoneum) 

• _____

  • Bulky middle layer → consists of interlacing layers of _____ _____

  • Contracts rhythmically during childbirth 

• _____

  • _____ lining 

  • Simple columnar epithelium on top of thick lamina propria 

  • Fertilized egg burrows into here and resides there during childbirth

perimetrium, myometrium, smooth muscle, endometrium, mucosal

Mammary Glands

• Present in both male and female but NORMALLY only function in females 

• Main function = _____ production to nourish newborn

milk

Female Physiology - Oogenesis

• Production of female gametes 

• Begins in _____ _____

  • _____ (diploid stem cells) divide by _____ to produce→ _____ oocytes

  • Primary oocytes undergo _____ 1 to produce → secondary oocytes 

  • Secondary oocytes undergo meiosis 2 to produce → ova 

  • OVERALL: oogonia → primary oocyte → secondary oocyte → ova

• At BIRTH = female presumed to have LIFETIME supply of primary oocytes 

fetal period, oogonia, mitosis, primary, meiosis

Oogenesis vs. Spermatogenesis

1. Production of primary oocytes occurs only _____ (puberty for males) 

2. In primary oocytes, meiosis STOPS in late _____ I and resumes only YEARS later (if at all) 

3. In secondary oocytes, meiosis stops in _____ II and is only completed if _____ occurs

fetus, prophase, metaphase, fertilization

Oocytes & Follicles

• Ovarian follicles → functional unit of ovary that encloses a _____ oocyte, surrounded by: 

  • _____ -_____ cells if a SINGLE layer of cells present 

  • _____ cells if MORE than one layer present 

• Follicles go through stages of development 

  • _____ follicles = SINGLE layer of squamous pre-granulosa cells surrounding primary oocyte 

• Primary follicles → have a _____ layer of _____ pre-granulosa cells surrounding primary oocyte 

• Secondary follicles → have _____ layers of granulosa cells surrounding primary oocyte

single, pre-granulosa, granulosa, primordial, single, cuboidal, multiple

Oocytes & Follicles - Cont’d

• _____ (antral) follicles → have fluid-filled cavity called an _____

  • Tertiary follicles 

  • BEFORE ovulation = primary oocyte inside vesicular follicle resume meiosis and becomes _____ oocyte

• Oogenesis begins at fetal period and takes YEARS to complete 

• _____ follicles first develop in fetus 

  • Primary oocytes are stopped in prophase I

  • Only small fraction recruited into pool

vesicular, antrum, secondary, primordial

Oocytes & Follicles - direction (2)

1. _____ = Apoptosis of oocyte and surrounding cells 

• 99.9% of all follicles are never recruited 

2. _____ = each month after puberty, a select few primary oocytes are activated 

• Caused by HIGH _____ levels (especially FSH) 

• One from this group is “selected” each month to become _____ follicle

atresia, ovulation, hormonal, dominant

Products of Meiosis in Females

• Dominant follicles resume meiosis I just BEFORE ovulation 

• After division of meiosis I is complete → 2 haploid cells of DIFFERENT sizes are produced: 

  • FIRST polar body = _____ cell that is almost devoid of _____

  • Secondary oocyte = _____ cell w/ almost ALL of mother cell cytoplasm and organelles

smaller, cytoplasm, large

Products of Meiosis in Females - Cont’d

• Secondary oocyte stops in metaphase II → this is the cell that will become _____ _____

  • If NOT penetrated by sperm = oocyte deteriorates 

  • If penetrated by sperm = secondary oocyte quickly COMPLETES meiosis II 

• Penetrated oocyte creates: 

  • _____ = large cell with enough cytoplasm to nourish fertilized egg for 6-7 day journey to uterus 

  • _____ _____ _____ = small cell lacking cytoplasm degenerates and DIES

ovulated ovum, ovum, second polar body

Ovarian Cycle

• Monthly (about 28 days) series of events associated w/ maturation of egg 

  • 2 consecutive phases 

  • _____ phase = period of _____ follicle growth (day 1-14) 

  • Ovulation occurs MIDCYCLE BETWEEN phases

  • _____ Phase = period of _____ _____ activity (day 14-28) 

• Only 10-15% women have 28-day cycle 

  • Follicular phase varies

  • BUT luteal phase is ALWAYS _____ days from ovulation to end of cycle

follicular, vesicular, luteal, corpus luteum, 14

Follicular Phase

• Several vesicular (antral) follicles become SENSITIVE to FSH and are stimulated to _____

  • One dominant follicle becomes especially sensitive to FSH 

• FSH levels _____ around middle of follicular phase 

  • Dominant follicle outcompetes other follicles and is the ONLY one to continue on 

  • Other non-dominant follicles with undergo _____

• Primary oocyte of dominant follicle completes meiosis I to form secondary oocyte and first polar body 

• _____ cells then send signal to oocyte → cause it to _____ meiosis

grow, drop, atresia, granulosa, stop

Ovulation

• Ballooning _____ _____ ruptures → expels _____ oocyte with its _____ _____ into peritoneal cavity 

  • Mittelschmerz = twinge of pain sometimes felt at ovulation by some women 

• 1-2% of ovulations release MORE than one secondary oocyte → fertilized results in _____ twins 

  • _____ twins result from fertilization of ONE oocyte → then separation of daughter cells 

• In some women → oocytes may be released at times unrelated to hormone levels

ovary wall, secondary, corona radiata, fraternal, identical

Luteal Phase

• After ovulation → ruptured follicle collapses → antrum fills with clotted blood 

  • Aka corpus hemorrhagicum, will eventually be absorbed

• Remaining granulosa cells and internal thecal cells enlarge to form _____ _____

• Corpus luteum secretes _____ and some estrogen 

• If NO pregnancy → corpus luteum degenerates into corpus _____ (scar) in 10 days 

• Pregnancy → corpus luteum produces hormones that sustain pregnancy until _____ takes over (at about 3 months)

corpus luteum, progesterone, albicans, placenta

Regulation of Female Reproductive System - Hormonal

1. _____ stimulates FSH and LH secretion 

2. FSH and LH stimulate _____ to GROW, mature, and secrete sex hormones

• FSH stimulates _____ to release _____

• LH stimulates _____ cells to produce _____ → which granulosa converts to estrogens 

3. _____ feedback INHIBITS gonadotropin release 

• Increasing levels of plasma estrogen levels = negative feedback _____ on FSH and H release 

• _____ from granulosa cells also inhibits FSH release 

• Only _____ follicles can withstand this dip in FSH 

  • Other developing follicles deteriorate 

GnRH, follicles, granulosa, estrogen, thecal, androgens, negative, inhibition, inhibin, dominant

Regulation of Female Reproductive System - Hormonal

4. _____ feedback stimulates gonadotropin release

• Estrogen levels continue to RISE as a result of continued release by dominant follicles 

• When levels reach a critical HIGH value = _____ POSITIVE feedback happens on brain and anterior pituitary 

• Triggers _____ surge 

positive, brief, LH

Regulation of Female Reproductive System - Hormonal
5. LH surge triggers ovulation and formation of _____ _____

• HIGH estrogen trigger release of stored LH, and some FSH by anterior pit at _____

• Surge triggers _____

  • LH surge triggers primary oocyte to complete meiosis I to become _____ oocyte 

  • Secondary oocyte then enters meiosis II → continue to metaphase II 

• Shortly AFTER ovulation:

  • Estrogen levels _____

  • LH transforms ruptured follicle into corpus luteum

  • LH stimulates corpus luteum to secrete _____ and some estrogen almost immediately 

    • Progesterone helps maintain functional layer of _____

    • Maintains pregnancy if it occurs 

corpus luteum, midcycle, ovulation, secondary, drop, progesterone, endometrium

Regulation of Female Reproductive System - Hormonal
6. NEGATIVE feedback inhibits LH and FSH release

• Negative feedback from rising plasma progesterone and estrogen = INHIBIT LH and FSH release

• Inhibin (from corpus luteum and granulosa cells) → enhances inhibitory effect 

• Declining LH _____ luteal activity and inhibits _____ _____

ends, follicle development

Regulation of Female Reproductive System - Hormonal
If NO fertilization: 

• Corpus luteum degenerates when LH levels start to fall 

• Causes a sharp DECREASE in _____ and _____ → ends blockage of FSH and LH secretion → causes cycle to start all over again

estrogen, progesterone

Uterine (Menstrual) Cycle

• Cyclic series of changes in _____ that occur in response to fluctuating ovarian _____ levels

• 3 phases

endometrium, hormone

Uterine (Menstrual) Cycle (3)

1. _____ phase (day 0-4)

• _____ layer of endometrium is SHED 

• Ovarian hormones are at _____ levels 

• _____ levels are beginning to RISE 

• Stratum functionalis detaches from uterine wall and is shed 

  • Menstrual flow of blood and tissue lasts 3-5 days 

• By day 5 → growing ovarian follicles start to produce more _____

menstrual, functional, lowest, gonadotropin, estrogen

Uterine (Menstrual) Cycle (3)

2. _____ (preovulatory) phase → Day 5-14

• Functional layer of endometrium is REBUILT 

• RISING estrogen levels → prompt generation of new _____ _____ layer 

  • As layer thickens → glands enlarge → _____ _____ increase in number 

• Estrogen also increases synthesis of progesterone receptors in endometrium 

• THINS out sticky _____ _____ to facilitate _____ passage (normally thick) 

• Ovulation occurs at END of proliferate phase on day 14

proliferate, stratum functionalis, spiral arteries, cervical mucus, sperm

Uterine (Menstrual) Cycle (3)

3. _____ (postovulatory) phase → Day 15-28

• Begins RIGHT AFTER ovulation 

  • Enrichment of _____ supply and _____ secretion of nutrients → prepare endometrium to receive an embryo 

• Phase that is MOST consistent in duration 

• Endometrium prepares embryo to implant 

• RISING progesterone levels from corpus luteum prompt: 

  • Functional layer to become a _____ _____

  • Endometrial glands to enlarge and secrete _____ into _____ cavity

secretory, blood, glandular, secretory mucosa, nutrients, uterine

Uterine (Menstrual) Cycle (3)

3. Secretory (postovulatory) phase - If NO fertilization: 

• Corpus luteum degenerates toward END of secretory phase + progesterone levels FALL 

• Causes spiral arteries to kink and _____

• Endometrial cells die + glands regress 

• Spiral arteries _____ again → then relax and _____ wide → causing rush of blood into weakened capillary beds 

• Blood vessels _____ + functional layer sloughs off and uterine cycle STARTS all over again on 1st day of menstruation

spasm, constrict, open, fragment

Pregnancy & Human Development

• _____ = developing offspring 

• Pregnancy = state of carrying a developing conceptus 

• _____ period = time from LAST menstrual period until birth (abt 280 days)

• _____ = conceptus from fertilization through week 8

• _____ = conceptus from week 9 through birth

conceptus, gestation, embryo, fetus

Zygote to Blastocyst (2 steps)

Embryonic development continues as _____ → travels through _____ _____ to _____ (here it floats freely until it implants)

embryo, uterine tube, uterus

Zygote to Blastocyst (2 steps)

1. _____

• Occurs while zygote moves towards uterus 

• RAPID _____ divisions of zygote occur

  • Produces cells w/ HIGH surface-to-volume ratio that enhances _____ of nutrients and O2 + disposal of wastes 

• FIRST cleavage occurs after 36 hours + produces 2 daughters cells called _____ → which continue to divide 

• After 72 hours = cluster of cells contains 16 or more cells (referred to as _____ )

cleavage, mitotic, uptake, blastomeres, morula

Zygote to Blastocyst (2 steps)

2. Blastocyst Formation 

• Around day 4 or 5 → embryo reaches uterus 

  • Consists of 100 cells + now called _____

• Blastocyst is fluid-filled hollow sphere composed of: 

  • _____ cells

    • Display immunosuppressive factors 

    • Participate in _____ formation

  • _____ (inner cell mass)

    • Cluster of 20-30 rounded cells 

    • Becomes embryonic disc → which will form embryo + 3 or 4 extraembryonic membranes 

    • 4th extraembryonic membrane (chorion) is formed by trophoblast

blastocyst, trophoblast, placenta, embryoblast

Implantation and Placentation

• Blastocyst floats for about 2-3 days → nourished by uterine secretions 

• Implantation begins 6-7 days after ovulation 

  • _____ cells stick to site w/ proper receptors and chemical signals 

  • Inflammatory-like response occurs in endometrium 

    • Uterine blood vessels become more _____ and leaky → inflammatory cells invade area

trophoblast, permeable

Implantation and Placentation - Cont’d

• Trophoblast cells proliferate and form 2 distinct layers: 

  • _____ (cellular trophoblast) = INNER layer of cells 

  • Syncytiotrophoblast (syncytial trophoblast) = cells in OUTER layer 

    • Lose plasma membranes → become multinuclear mass 

    • Send out LONG protrusions that invade and digest _____

• As endometrium is eroded → blastocyst burrows into lining, surrounded by pool of leaked _____

• Endometrial cells then cover and seal off implanted blastocyst

• Implantation is usually completed by day 12 after ovulation (day 26 of menstrual cycle) 

  • About the same time menstruation would occur

cytotrophoblast, endometrium, blood