_HD-201_-E01_T02_Histology-of-Female-Reproductive-System_compressed

Overview of the Female Reproductive System

• The ability to engage in sexual intercourse and reproduction are primary functions.
• Endocrine functions facilitate the menstrual cycle.
• Complete development occurs after puberty.
• Internal genitalia include the ovary, uterus, cervix, fallopian tubes, and vagina.
• External genitalia include the clitoris, urethra, labia majora, and labia minora.

Ovary - General Areas

• Cortex: peripheral area containing ovarian follicles and cellular connective tissue.
• Medulla: inner area containing loose connective tissue, lymphatics, blood vessels, and nerves.
• No clear demarcation exists between the cortex and medulla.
• Follicles indicate observation of the cortex.

Ovarian Cortex

• Germinal epithelium lines the outer surface of the ovary, comprised of low cuboidal epithelium.
• Tunica albuginea is an avascular layer of connective tissue.
• Ovarian follicles can be found here.
• Only one mature follicle is expelled during ovulation for potential fertilization.

Ovarian Follicles

• A lone oocyte is surrounded by follicular cells.
• Distribution occurs at different developmental stages within the cortex.
• Size indicates maturity.
• Oocytes and follicular cells develop different characteristics as they mature.
• At birth only primordial follicles are present.
• Types include: primordial, primary, secondary, mature/Graafian follicles.

Primordial Follicle

• Forms during the fetal stage, specifically in the 3rd month.
• Only follicle type present in the ovaries at birth.
• Key feature: a primary oocyte enveloped by a single layer of flattened follicular cells.
• Smaller follicles are located nearer the ovarian surface.
• Follicles increase in size and grow towards the medulla as they mature, but remain within the cortex until ovulation.
• Features an eccentric nucleus.
• Organelles clump adjacent to the nucleus, forming Balbiani bodies, which include mitochondria, Golgi complex, and rough endoplasmic reticulum.
• Growth is independent of gonadotropin stimulation.
• Transitions into a primary ovarian follicle as puberty approaches.

Primary Ovarian Follicle

• Key feature: Follicular cells are simple cuboidal, forming a single or stratified layer around the primary oocyte, now called granulosa cells.
• Several primary follicles enter rapid growth, becoming secondary ovarian follicles each menstrual cycle after puberty.
• Characterized by the dispersal of organelles.

Secondary Ovarian Follicle

• Small fluid spaces appear among the proliferating granulosa cells.
• Key feature: Spaces coalesce to form an antrum when the growing follicle reaches about 200 µm in diameter.
• Granulosa cells proliferate, and the oocyte grows.
• One follicle develops into the Graafian follicle prior to ovulation.
• Liquor folliculi is liquid inside the antrum; it's a transudate of plasma with a higher concentration of steroids and gonadotropic hormones.
• Antrum is a single cavity formed by the coalescing of liquor folliculi displaces the oocyte to one side.

Zona Pellucida

• A highly refractile layer containing glycoproteins secreted by the oocyte lies between the oocyte and innermost granulosa cells.

Theca Folliculi

• Connective tissue organized around the follicle that is separated from granulosa cells by the basal lamina
• Separation is distinct.
• Theca folliculi develops into two layers.

Theca Interna

• The vascular layer of epithelioid cells acquires smooth ER and steroid-secreting cell characteristics.
• Produces androgenic steroids that diffuse into the follicle and are converted to estradiol by granulosa cells.

Theca Externa

• Connective tissue contains smooth muscle cells and bundles of collagen fibers.

Cumulus Oophorus

• Thickening of the granulosa layer projects into the antrum.

Graafian Follicle

• The most mature phase that contains a secondary oocyte with further antrum enlargement.
• Key feature: the formation of corona radiata where Granulosa cells surround the freely-floating oocyte; formed when the cumulus oophorus is replaced.
• Fluid-filled spaces appear among granulosa cells at the base of cumulus oophorus causing the oocyte to detach and float freely.

Oogenesis

• The development of female germ cells that starts before birth during fetal development.

6th Week Fetal Development

• Primordial germ cells (oogonia) migrate from the secondary yolk sac to the genital ridge, where the ovary develops.
• Continuous mitosis of oogonia occurs up to the 5th month of embryonic life.

3rd Month of Fetal Development

• Oogonia develop into primary oocytes, the only oocytes present at birth.
• Primary oocytes begin Meiosis I, arrested at Prophase I, and ~2 million are produced.

Ovulation

• The primary oocyte in the developing Graafian follicle continues meiosis and results in two haploid (23 chromosomes) daughter cells: a secondary oocyte (gets most cytoplasm and is released) and a first polar body.
• Meiosis I is completed, but meiosis II is arrested at metaphase II; it will only continue upon fertilization
• Continuation of meiotic division produces first polar body and secondary oocyte
• Meiosis is arrested at metaphase II, resuming during fertilization when there are two daughter cells
• Fertilized oocyte
• Second polar body

Process of Ovulation

1. The secondary oocyte is released by the Graafian follicle.
2. Fimbriae catch the oocyte.
3. The oocyte travels to the ampulla for fertilization.
4. If fertilization happens, the oocyte implants in the uterus. a. Ectopic pregnancy results when the fertilized oocyte implants in the Fallopian tube
5. If unfertilized within 24 hours, the oocyte gets reabsorbed.

Factors in Ovualtion

• LH surge, released from the pituitary gland, causes ovulation and maintains the corpus luteum.
• Formation of the stigma/macula pellucida, a translucent area on the bulging surface of the mature follicle where blood flow ceases.
• Increase in collagenase digests collagen in the theca and thins the tunica albuginea.
• Contraction of theca externa smooth muscle fibers.

Anovulatory Cycle

• A menstrual cycle happens without ovulation with irregular menstruation.

Changes in Ovarian Surface

• Ovaries with more repeated ovulation have more scarring.
• The degree of scarring is proportional to age.
• Birth control pills result in smoother ovarian surfaces by preventing ovulation.

Corpus Luteum

• Results from the reorganization of the collapsed follicle after ovulation, located in the ovarian cortex.

Transformation From Graafian Follicle to Corpus Luteum

1. After ovulation, the Graafian follicle wall collapses.
2. Blood vessels invade the granulosa cell layer.
3. Granulosa and theca interna cells hypertrophy.
4. Cells develop smooth endoplasmic reticulum and accumulate lipid droplets to transform into lutein cells.

Corpus Luteum Types

• Depends whether fertilization comes about.
• Corpus luteum of menstruation regresses in 9-10 days without fertilization.
• Corpus luteum of pregnancy forms when oocyte gets fertilized and persists for the first two months of pregnancy (placenta still developing).
  • Needed source of progesterone.
  • Secretes relaxin, which relaxes uterine smooth muscle cells.

Lutein Cells

• Abundant with smooth endoplasmic reticulum and lipid droplets for steroid secretion.
• Arise from granulosa from granulosa cells (80% of parenchyma); pale cytoplasm containing lipid droplets, secrete mainly progesterone and some estrogens.Theca lutein arise from theca interna cells, are located at periphery as small, deeply staining cells, secrete estrogen and estradiol.

Follicular Atresia

• The degeneration of all ovarian follicles not developing into the Graafian follicle, occurring continually before birth until menopause.
• Acceleration occurs during birth, puberty, and pregnancy, at any stage of follicular development.
• Breakdown of the oocyte and granulosa cells, with granulosa cells shed into the antrum.
• Basal lamina thickens to form a glassy membrane, indicative of follicular atresia.
• Some follicles undergo follicular atresia at any given time.

Uterus Anatomy

• Pear-shaped human uterus with a thick muscular wall
• Fundus: rounded upper portion.
• Body/Corpus: wide upper 2/3.
• Isthmus: narrower portion below the body that separates it from the cervix.
• Cervix: lower portion.

Layers of the Uterine Wall

• Endometrium: Lined with simple columnar epithelial cells
• Myometrium: Middle muscle layer of the uterus with interlacing bundles of smooth muscle separated by connective tissue
• Perimetrium: Outermost serosal layer composed of connective tissue
• Cervix: smooth muscles decrease and connective tissue increases (from the isthmus to the cervix)

Uterine Circulation

• The order of branching is Uterine > arcuate > radial > basal > spiral.
• The uterine artery supplies the uterus.
• Arcuate artery takes a circumferential course in the middle of the myometrium.
• Radial artery are penetrating branches of the arcuate artery.
• Basal arteries are lateral branches of the radial artery that supply the basalis layer of the endometrium.
• Spiral arteries supply the functionalis layer and are sensitive to changes in hormone levels.

Uterine Endometrium

• The innermost layer of the uterus and is lined with simple columnar epithelium.
• Notable components: Tubular uterine glands extending from the epithelium.
• Endometrial stroma is a thick layer of connective tissue.
• It receives the blastocyst for implantation and the embryo's nutrition. Forms the maternal portion of the placenta.
• It undergoes cyclic alterations due to hormone changes.

Endometrium Layers

• Stratum Functionalis/Functional Layer is the superficial layer that is sloughed off during menstruation.
• Stratum Basalis/Basal Layer is the deeper layer that functions in regeneration in the next menstrual cycle.

Menstrual Cycle

• Contains two synchronized and interrelated processes in the ovaries and uterus.
• Ovarian cycle: Development of ovarian follicle leading to ovulation.
• Uterine cycle: Formation of the functional layer in response to ovarian activity for 28 days on average
• Menstrual Phase occurs in days 1-5; the first stage of the cycle that occurs because of low progesterone/estrogen levels
• Ischemia happens as decreased levels of hormones happens, leading to contraction and the detachment of the endothelium
• Proliferative Phase happens days 6-14 and is marked by cell proliferation as levels rise. Endometrial thickening, where changes happen in the uterine glands by becoming straight and increases glycogen content
• Secretory Phase happens between days 15-28; the uterine glands in the startum functionale become tortuous.

Ovarian Cycle

• Relevant hormones affect it along with the uterine cycles.

Starts of Menstrual Cycle

• Accompanied by a decrease in estrogen and progesterone
• Follicle stimulating hormone (FSH) stimulate the development of follicles in the ovaries

Uterine Proliferative Phase

• The proliferation of cells in the epithelium occurs in the startum basal, which makes regeneration come about within the surface
• Coiled parts of the arteries that were lost regenerate
• The endometrium has become identified by identifying what is present within the uterine glands

Secretory Phase

• The glands in the functionalis layer become tortous and uterine glands actively aquire lateral sacculations
• Stromal has also become edematous as gland becomes dilated

Mentstrual Phase

• The secondary oocyte is unfertized
• This loss results in the degeneration of the stratum functionlis layer by shedding of the necrotic lumps from the endometrium

Cervix Parts

• Lower portion of uterus, made of fibro-muscular.
• Ectocervix, also known as portio vaginalis, lower end of the cervix that projects into the vagina.
• Endocervix is the space that surrounds the endocervical canal

Cervix Components

• Lined by tall columnar epithelium
• Nuclei displace mucos droplets, while endocervial glands has is high branching within the simple columnar
• They get impacted by hromones

Fallopian parts

• Measures 12 cm
• Extends to the uterus
• It provides an environment for the ovum for the main purpose of getting fertizilation
• Divided into 4 parts: Intramural, Isthmus, Ampulla and Infundibulum

Vaginal Muscular Types

• Mucosa
• Longitudinally oriented muscle bottoms Outermost for support. Contains 3 laters- inner, mid and outer

External Genitalia

• Made up of the clitors, as well as the labia majora and minora
• Labia minora- folds of skin that has spongy tissue and few pigments