BLOCK 4 all

fertilization

sperm’s chromosomes combine with those of secondary oocyte to form fertilized egg, called a **zygote**

capacitated

sperm must be capacitated before they can penetrate oocyte

* motility must be enhance and cell membranes must become fragile enough to release hydrolytic enzymes

sperm must reach oocyte

–Oocyte viable for 12 to 24 hours



–Sperm viable 24 to 48 hours after ejaculation

completion of meiosis II and fertilization

1\.Ca2+ surge triggers completion of meiosis II in oocyte, resulting in ovum + second polar body

•Ovum nucleus swells to become **female pronucleus**

2\.As sperm nucleus moves toward oocyte nucleus, it also swells

•Forms **male pronucleus**

3\.DNA in each pronucleus replicates, and as pronuclei get closer, a mitotic spindle forms between them

•Nuclear envelopes dissolve, releasing chromosomes together in vicinity of mitotic spindle

4\.Maternal and paternal chromosomes combine, forming diploid *zygote*

•**Fertilization**: moment chromosomes combine

gestation

to carry

pre-embryonic stage

First 2 weeks or prenatal development (0-2 weeks).

embryonic stage

weeks 3-8

fetal period

Weeks 9-40 (until birth)



A developing human is referred to as an **embryo** during weeks 3-8; and a **fetus** from the 9th week of gestation until birth.

first trimester

conception to 12 weeks (about 3 months)

second trimester

12 to 24 weeks

third trimester

24-40 weeks

syncytiotrophoblast

trophoblast cells fuse with each other to form

(digests the endometrial cells)

what does the syntiotrophoblasts

secrete human chorionic gonadotripin (hCG)

**human chorionic gonadotropin** (**hCG**)

a hormone that signals for the maintenance of the corpus luteum and the continuous production of progesterone and estrogen to suppress menses.

extra-embryonic membranes that support/protect developing embryo

* amnion
* yolk sac
* allantois
* chorion

at 3 weeks what does the embryonic disc form into?

a 3 layered disc gastrulation

what does the embryo form?

primitive streak (dorsal surface of the epiblast)

cells migrate towards and through the primitive streak and then move laterally creating what two layers?

the **endoderm** (displaces the hypoblast and lies adjacent to the yolk sac) and the **mesoderm** (middle layer). Remaining epiblast (become **ectoderm**).

ectoderm

gives rise to cell lineages that differentiate to become the central and peripheral nervous systems, sensory organs, epidermis (skin), hair, and nails.

mesodermal

cells ultimately become the skeleton, muscles, connective tissue, heart, blood vessels, and kidneys.

endoderm

goes on to form the epithelial lining of the gastrointestinal tract, liver, and pancreas, as well as the lungs.

placenta

develops throughout the embryonic period and during the first several weeks of the fetal period

placentation

complete by weeks 14-16

first several weeks of placenta

Decidual cells of the endometrium nourish the nascent embryo. The developing placenta takes over gradually (weeks 4-12).

fetal alcohol spectrum disorders (FASD)

These include organ and facial malformations, as well as cognitive and behavioral disorders.

Pregnant women should avoid fetotoxic substances. Alcohol consumption by pregnant women,

“TORCH”

* toxoplasmosis
* other-hiv
* rubella
* cytomegallo virus
* herpes

\

neurulation

the process in which the neural plate bends

and fuses to form the hollow tube that will differentiate into the brain and the spinal cord of the CNS (ectodermally derived)

neural plate

ectoderm cells (neuroectodermal tissues) of embryo thicken to form

organogenesis week 4

Tissues on either side of the plate fold upward into a neural fold; the folds converge to form the **neural tube**. The tube lies atop the mesoderm-derived notochord (future nucleus pulposus of the intervertebral discs).



**Somites** form on either side (axial skeleton, skeletal muscle and dermis).

spina bifida

part of spinal cord is on the outside

* myelomeningocele
* epithelial membrane
* spinal placodes
* spinal fluid
* dura mater

embryo folding

The embryo folds ”laterally” forming a C-shape with a head (cranial) and tail (caudal) end. Folding envelops a portion of the yolk sac, which protrudes with the umbilical cord from what will become the abdomen

embryonic folding

The embryo begins to take shape from the flat sheet of cells to a cylindrical shape through

organogenesis

The developing embryo establishes the rudimentary structures of all its organs and tissues from the established three-germ layers within the first 8-weeks of gestation.

development of the heart

–The heart begins its development as tube-like structure. Cells of the primitive tube-shaped heart are capable of electrical conduction and contraction. The heart can beat by the 4th week (but does not pump embryonic blood).

organogenesis weeks 4-5

–eye pits form, limb buds become apparent, and the rudiments of the pulmonary system are formed.

organogenesis week 6

–Uncontrolled fetal limb movements occur. The GI system develops too rapidly for the abdominal space: the intestines loop into the umbilical cord (temporarily). Paddle-shaped hands and feet develop fingers.

organogenesis week 7

–Nostrils, outer ears and lenses are apparent.

organogenesis week 8

–Head as large as the body (brain structures in place); external genitalia indistinguishable. Bone begins to replace cartilage in the embryonic skeleton (ossification).



–By the end of week 8 (embryonic period), the embryo is \~ 3 cm from crown to rump (\~8 grams).

fossa ovalis

at birth the valve-like foramen ovale is closed by a relative increase in left atrial pressure forcing the valve against the septum it fuses closed forming the

parent foramen ovale

if foramen ovale fails to close after birth=parent

* can become problematic if blood clots are present

ovaries

female gonads

* produce female gametes
* secrete female sex hormones, estrogen and progesterone

internal genitalia

•located in pelvic cavity; include **ovaries** and **duct system** (uterine tubes, uterus, and vagina)

external genitalia

external sex organs

ovaries

paired structures that flank the uterus

* each ovary is held in place by several ligaments
* ovarian ligament
* suspensory ligament
* mesovarium

ovarian ligament

anchors ovary medially to uterus

suspensory ligament

anchors ovary laterally to pelvic wall

mesovarium

suspends ovary

•Suspensory ligament and mesovarium are part of **broad ligament** that supports uterine tubes, uterus, and vagina

tunica albuginea

each ovary is surrounded by a fibrous

two histological regions in ovary

•Outer cortex: houses forming gametes

•Inner medulla: contains large blood vessels \n and nerves

ovarian follicles

•tiny saclike structures embedded in cortex



–Contain immature egg (**oocyte**) encased by one or more layers of very different cells

ovulation

Each month a ripened follicle ejects oocyte

tube system

–**Uterine tubes**



–**Uterus**



–**Vagina**

uterine tubes

•also called *fallopian tubes* or *oviducts*, receive ovulated oocyte and are usual site of fertilization



•Each tube \~10 cm (4 in) long and extends from area of ovary to superior region of uterus

regions of uterine tube

–**Infundibulum**



–**Ampulla**

\
–**Isthmus**

infundibulum

–funnel-shaped opening into the peritoneal cavity



•Margin contains ciliated projections called *fimbriae* that drape over ovary

ampulla

–forms half of uterine tube length



•Is site where fertilization usually occurs

isthmus

–narrow medial third that empties into superolateral region of uterus

uterine tubes are

–Covered by peritoneum

–Supported by a short mesentery called **mesosalpinx**

ectopic pregnancy

–Oocyte is fertilized in peritoneal cavity or distal uterine tube and begins developing there



•Normally abort naturally with substantial bleeding

pelvic inflammatory disease (PID)

–Oocyte is fertilized in peritoneal cavity or distal uterine tube and begins developing there



•Normally abort naturally with substantial bleeding

uterus

hollow organ located between the urinary bladder and rectum. Functions of the uterus include receiving, retaining and nourishing of the fertilized egg. The uterus consists of the **body**, **fundus** and **cervix**.

3 layers of uterine wall

* perimetrium
* myometrium
* endometrium

two endometrium layers

* stratum functionalis (functional layer)
* stratum basalis (basal layer)

stratum functionalis (functional layer)

•Changes in response to ovarian hormone cycles



•__Shed during menstruation__

stratum basalis (basal layer)

•Forms new stratum functionalis after menstruation



•Unresponsive to ovarian hormones

cervical cancer

•affects 450,000 women worldwide each year, killing half



–Most common between ages 30 and 50



–Risks: frequent cervical inflammation; STIs, including HPV; or multiple pregnancies



•Gardasil: three-dose vaccine; protects against HPV



–Recommended for 11- and 12-year-old girls



–Papanicolaou (Pap) smear for detection



•Recommended every 3 years for ages 21–30



–Every 5 years for ages 30–65, but include HPV testing



–Discontinue at 65, after hysterectomy, or with sexual inactivity

supports of the uterus

–**Mesometrium**: lateral support of broad ligament

–**Cardinal** (**lateral cervical**) **ligaments**: from cervix and superior vagina to pelvic lateral walls

–**Uterosacral ligaments**: secure uterus to sacrum

–**Round ligaments**: bind uterus to anterior wall

sacs of peritoneum exits around uterus

\
–*Vesicouterine pouch* between bladder and uterus

–*Rectouterine pouch* between rectum and uterus

vagina

•Thin-walled tube 8–10 cm (3–4 inches) in length



•Functions as birth canal, passageway for menstrual flow, and organ of copulation



•Extends between bladder and rectum from cervix to exterior



•Urethra runs parallels to vagina anteriorly



•Vaginal secretions are acidic in adult females, but alkaline in adolescents

layers of vaginal wall

–Fibroelastic *adventitia*



–Smooth muscle *muscularis*



–Stratified squamous *mucosa* with rugae

labia majora

hair-covered fatty skin folds

labia minora

skin folds lying w/in labia majora

mons pubis

fatty overlying pubic symphysis

vestibule

recess w/in labia minora

fourchette

•ridge formed by joining of posterior vestibule and labia minora

greater vestibular glands

homologous to bulbo-urethral glands

* release mucus into vestibule for lubrication

clitoris

ant to vestibule

glands of clitoris

exposed portion

prepuce of the clitoris

hoods glans

bulbs of the vestibule

lie along each side of orifice that engorge with blood during sexual stimulation

mammary glands

• present in both male and female, but normally function only in female

•Main function is milk production to nourish newborn

•Modified sweat glands consisting of 15–25 **lobes**

•**Areola**: pigmented skin surrounding **nipple**

•**Suspensory ligaments**: attach breast to underlying muscle

•Lobules within lobes contain glandular **alveoli** that produce milk

–Milk is passed into **lactiferous ducts**, then into **lactiferous sinuses** that open to outside at nipple

–In non-nursing women, glandular structure is undeveloped

•Breast size is due to amount of fat deposits

breast cancer

•Invasive breast cancer is the most common malignancy and second most common cause \n of cancer death in U.S. women



•13% of women will develop condition



•Usually arises from epithelial cells of smallest ducts that eventually metastasize

breast cancer risk factors

\
–Early onset of menstruation and late menopause



–No pregnancies or first pregnancy late in life



–No or short periods of breast feeding



–Family history of breast cancer

breast cancer diagnosis

–Early detection via self-examination and **mammography**, a type of X-ray examination

lumpectomy

less invasive and excises only cancerous lump

simple mastectomy

–removes only breast tissue, sometimes some axillary lymph nodes

oogenesis

production of female game

oogonia

(diploid stem cells) divide by mitosis to produce

* primary oocytes
* secondary oocytes
* ova

secondary oocytes

undergo meiosis II to produce ova

primary oocytes

meiosis Ito produce secondary oocytes

3 key differences between oogenesis and spermatogenesis

1\.Production of primary oocytes occurs only in the fetus



2\.In primary oocytes, meiosis is arrested in late prophase I and resumes only years later (if at all)



3\.In secondary oocytes, meiosis is arrested in metaphase II and is only completed if fertilization occurs

ovarian follicle

functional unit of ovary that encloses a single oocyte surrounded by pre-granulosa cells and granulosa cells

pre granulosa cells

if single layer of cells present

granulosa cells

if more than one layer present

primordial follicle

single layer of squamous pre-granulosa cells surrounding primary oocyte

primary follicles

•– have a single layer of cuboidal pre-granulosa cells surrounding primary oocyte

secondary follicles

have multiple layers of granulosa cells surrounding primary oocyte

vesicular (antral) follicles

•(tertiary follicles) have a fluid-filled cavity called an **antrum**



–Before ovulation primary oocyte inside vesicular follicle resumes meiosis and becomes secondary oocyte

follicles have two fates

* atresia
* ovulation

atresia

•apoptosis (programmed cell death) of oocyte and surrounding cells



–99.9% of all follicles are never recruited