- made up of perimetrium, myometrium, and endometrium

- supplied by uterine artery

- site of implantation of ovum

- connects to endocervix and interstitial portion of uterine tube

Uterus

- outermost layer of serosa

- covers upper and posterior regions of uterus only

- adventitia surrounds the remaining portion that lie adjacent to urinary bladder

Perimetrium

- a thick, well-vascularized band of smooth muscle arranged in ill-defined layers

- froms major portion of uterus and is equivalent to muscularis externa

Myometrium

- mucosa containing tubular glands, simple columnar ciliated epithelium, and multipotential stromal cells w/ ground substance

Two zones

functional- luminal 2/3 sloughed during menstruation

basal- firmly attached to myometrium, retained during menstruation and replenishes functional zone

Endometrium

- uterine arteries supply myometrium and extend into basal layer of endometrium

- basal arteries --> spiral arteries in functional zone

- capillary plexus beneach surface epithelium

Endometrium arterial supply

- nearly straight early in menstrual cycle

- become highly coiled later

- bleed during menstruation and supply functional zone that is sloughed

Spiral arteries

- days 1-4

- clinical beginning of cycle

- end of menstruation where the functional zone is sloughed and only basal zone remains

Menstrual phase

- days 5-14

- ovarian follicles growing, secrete estrogen

- functional zone proliferates, regenerates from basal zone

- epithelial and stromal cells thicken endometrium

- glands become wavy toward end of phase

- spiral arteries not yet coiled

Proliferative phase

- corpus luteum present and functional

- uterine glands secrete glycogen and glycoproteins

- glands enlarge, become tortuous, coiled

- spiral arteries become coiled, visible

- stromal cells --> (pre)decidual cells

Secretory phase

- large, pale cells with glycogen and lipid

- located under surface epithelium, around spiral arteries

- become decidual cells with pregnancy (decidua)

- w/o pregnancy, sloughed with menses

stromal cells

- Days 26-28

- ischemic portion of secretory phase

- estrogen and progesterone production decreases

- periodic constriction of spiral arteries --> ischemia in functional zone

- endometrium becomes necrotic, bleeds

Premenstrual phase

- lowest portion of uterus

- made up of endo- and ecto- cervix

- mucosa not sloughed during menstruation

- spiral arteries absent

- mid-cycle, secretions more abundant and more fluid

- alkaline secretions buffer acidic vaginal fluids

- its mucus more viscous at other times in cycle

Cervix

- simple columnar epithelium with cilia and mucus secreting cells

- filled with epithelial folds, plica palmatae

- nabothian cysts occur when fold is occluded

- surrounds endocervical canal

Endocervix

- portion of cervix that protrudes into vagina

- covered by moist stratified squamous epithelium

- junction of epithelium with endocervical canal is abrupt (transitional zone)

- squamous metaplasia most likely occurs in this zone (cervical cancer)

- pap smear done here

Ectocervix

- stratified squamous nonkeratinized epithelium w/ glycogen but no glands

- rich numerous erectile-type blood vessels

- rugae allow for expansion

- surrounded by skeletal muscle (kegals)

- becomes thick and proliferative w/ extra glycogen mid-cycle

- lactic acid from glycogen use makes it acidic

Vagina

- composed of extraembryonic CT and two cell layers from the trophoblast

- forms within 23 days following ovulation

- trophoblast erodes into maternal endometrium

- cytotrophoblast and syncytiotrophoblast forms

- Lacunae develop

- tertiary (chorionic) villi increase surface area of placenta

Chorion (Fetal Placenta)

- inner (toward embryo) single layer that gives rise to syncytiotrophoblast

- large, discrete cells with large, euchromatic nuclei

- forms continuous uterus layer in early pregnancy

- layer thins and is lacking in some areas decreasing the barrier through which nutrients/wastes must pass

Cytotrophoblast

- multinucleated, outer synctium formed from cytotrophoblast

- aggressively invades uterine endometrium

- covers outer surface of villus

- possess microvilli and abundant organelles associated with protein and steroid hormone production

- forms part of interhemal barrier

- secretes HCG, HPL, HPT (thyrotropin), estrogen and progesterone

- villi go from thick to thin/branching (early to late)

Syncytiotrophoblast

- final in a series of villi that protrude from syncytiotrophoblast columns into lacunae

- increase surface area of placenta and maternal blood

- formed by invasion of cyto cells by fetal CT

- fetal blood vessels invade into and form within

Tertiary (definitive) chorionic villi

- separated by columns of syncytio

- develop in syncytio and coalesce to fill with maternal blood from spiral arteries

- later called intervillous spaces

Lacunae

- outer ring of fetal placenta abutting maternal placenta

- composed of cytotrophoblast between syncytio and decidua

- formed from cyto cells growing and spreading beneath syncytio columns

Trophoblastic shell

- formed from endometrial stromal cells at day 24

3 subdivisions

Decidua basalis - underlies implanted conceptus froming maternal portion of functional placenta

Decidua capsularis - covers luminal surface of conceptus, eventually fuses with decidua parietalis obliterating the uterine lumen

Decidua parietalis - lines remainder of uterus

Decidua (maternal placenta)

- form a "lobe" of placenta

- dome-shaped protrusions from the placenta

- ~35 lobes are present

- malformations can indicate fetal abnormalities

Maternal cotyledons

- two umbilical arteries from fetus thru umbilical cord to placenta

- in tertiary villi, capillaries allow diffusion

- single umbilical vein returns to conceptus

Fetal placental blood flow

- spiral arteries penetrate trophoblastic shell

- spurt blood into intervillous spaces (old lacunae), bathing villi

- branches of uterine veins carry blood away from intervillous spaces

Maternal placental blood flow

- made of capillary endothelial cell of villus and its basement membrane, fetal CT of villus, cytotrophoblast, syncytiotrophoblast

- cyto + fetal CT lacking late in pregnancy

Interhemal membrane