HISTO Lec Chap 12 : Female Reproductive System

MTY1208 Lab and Lec

Structures of the Female Reproductive System

• Ovary 

• Uterine Tubes

• Uterus

• Vagina

• External Genitalia

• Placenta

• Mammary Glands

EXTERNAL GENITALIA

• Labia Majora

• Labia Minora

• Clitoris

INTERNAL GENITALIA

• Ovaries 

• Uterus

• Vagina

Gonadotropic Hormones

The development of reproductive organs is not complete until ________ of the pituitary gland initiate puberty.

OVARY

• Paired, slightly flattened oval organ, measuring approximately 3 cm x 1.5 cm x 1 cm.

• Covered by low cuboidal epithelium that forms the outer surface.

• The parenchyma is divided into two regions: the outer cortex and the inner medulla.

• The cortex contains numerous follicles of varying sizes, representing different stages of development.

• The medulla contains blood vessels, nerves, and lymphatic vessels that support ovarian function.

Primordial, Primary, Antral or Secondary, Mature or Graafian

OVARIAN FOLLICLES

Primordial Follicle

• Make up the majority of follicles in the ovary.

• Composed of a large spherical oocyte surrounded by a single layer of squamous cells.

• The only follicles present at birth, accounting for the initial ovarian reserve.

• These follicles are inactive at birth and remain in a dormant state until they are recruited for growth during the reproductive years.

• Dormancy is maintained by the surrounding squamous cells, and oocytes remain arrested in prophase I of meiosis until they are activated.

Primary Follicle

• Oocyte grows larger

• Lose their squamous epithelial covering, first becoming cuboidal, then proliferating into 2 or 3 layers of irregularly-shaped granulosa cells

• Oocyte and its surrounding granulosa cells become separated by a narrow space

  • Zona Pellucida ( a highly refractile layer of glycoprotein )

Zona Pellucida

• A glycoprotein-rich layer that surrounds the oocyte.

• Forms between the oocyte and the granulosa cells of the primary follicle.

• Functions as a barrier to prevent the entry of multiple sperm during fertilization.

• Plays a crucial role in sperm recognition and binding during fertilization.

• Contains specific proteins, such as ZP1, ZP2, and ZP3, that interact with sperm to facilitate sperm-oocyte recognition.

• Helps maintain oocyte integrity and is essential for fertilization.

Antral or Secondary Follicle

• Post-puberty, a number of primary follicles enter a phase of rapid growth in each menstrual cycle

• Oocyte enlarges further and granulosa cells proliferate rapidly

• Oocyte is displaced to one side by development of a fluid-filled cavity in the mass of granulosa cells, called the antrum

• Accumulations of a few dark-stained bodies among the granulosa cells, called Call-Exner Bodies

Call-Exner Bodies

• These are small, eosinophilic, fluid-filled cysts found within the granulosa layer of certain ovarian follicles, specifically in granulosa cell tumors.

• These bodies are characterized by a collection of granulosa cells arranged in a rosette-like or follicle-like pattern around a central space filled with clear fluid.

• The presence of these structures is considered a diagnostic feature of granulosa cell tumors, a type of sex cord-stromal tumor of the ovary.

• While they are not present in all granulosa cell tumors, their formation may reflect the hormonal activity of the tumor, particularly the secretion of estrogen.

• These are typically identified during histological examination and can help differentiate granulosa cell tumors from other types of ovarian neoplasms.

Mature or Graafian Follicle

• Oocyte resumes its meiotic division shortly before ovulation

• A large translucent vesicle occupies the full thickness of the cortex and bulges 1 cm or more above the surface of the ovary

• This is in preparation for ovulation

OVULATION

• The process by which a mature ovarian follicle ruptures to release a mature oocyte (egg) into the fallopian tube.

• The process begins with the formation of a clear vesicle within the dominant follicle, which is the antral or Graafian follicle. The vesicle contains fluid and surrounds the oocyte.

• Rupture occurs within minutes after the formation of the vesicle, leading to the extrusion of the oocyte into the peritoneal cavity and the fallopian tube.

• Along with the oocyte, a gush of follicular fluid is released, which can sometimes be observed clinically.

• Typically, only one oocyte is released per cycle, although multiple _____ can occur in some cases, such as in the case of multiple births.

• Hormonally regulated, with a peak in luteinizing hormone (LH) and follicle-stimulating hormone (FSH) triggering the final maturation and rupture of the follicle.

Corpus Luteum

• Post-ovulation, the Graafian follicle collapses, and its wall becomes deeply folded.

• This process transforms the follicle into the corpus luteum, which secretes progesterone to prepare the endometrium for potential implantation.

• If pregnancy does not occur, this structure degenerates into the corpus albicans.

Estradiol

plays a critical role in maturing oocytes and stimulating the development of the follicle during the menstrual cycle.

FSH (Follicle-Stimulating Hormone)

stimulates granulosa cells in the ovarian follicles to secrete estradiol, which is the precursor to estrogen.

Estrogen

helps mature oocytes and also helps to prepare the uterine lining for possible implantation and regulates the overall reproductive cycle.

LH (Luteinizing Hormone)

causes granulosa cells to decrease estradiol production, and instead, their primary product becomes progesterone.

Progesterone

plays a crucial role in thickening the uterine lining (endometrium) to prepare for possible implantation of a fertilized egg.

Theca Cells

• Interstitial cells found around the follicles

• Have receptors for LH which stimulate theca cells to secrete testosterone which later are converted to estradiol

• Found surrounding the granulosa cells in the ovarian follicles.

• Produce androgens (e.g., testosterone), which are converted to estradiol by granulosa cells under the influence of FSH.

• Essential for estrogen synthesis during the follicular phase of the menstrual cycle.

• Stimulated by LH to increase androgen production, which supports follicular development and ovulation

OVIDUCT OR FALLOPIAN TUBE

• Muscular tube about 12 cm long

• Its lumen is open to the peritoneal cavity at its distal end and opposite end opens into the uterine cavity

• Carries the oocyte or egg cell

• Lined by simple columnar epithelium

• 3 Portions : Isthmus, Ampulla, Infundibulum

ISTHMUS

• is the medial 3rd near the uterus

AMPULLA

• is the middle 3rd

INFUNDIBULUM

• is the distal 3rd, funnel-shaped and its margins have numerous tapering fringe-like processes called fimbriae

Fimbriae

• Finger-like projections at the distal end of the fallopian tube.

• Function to capture the ovum (egg) released during ovulation and guide it into the tube.

• Covered with ciliated epithelium that helps move the ovum towards the uterus.

• Play a key role in fertilization by facilitating the meeting of sperm and egg within the tube.

Functions of Oviduct

• Receives the ovum released from the ovary

• Provides the appropriate environment for its fertilization and transport to the uterus

UTERUS

• Pear-shaped 

• 7 cm x 4 cm x 2.5 cm 

• Divided into fundus, corpus uteri or body, isthmus, and a cylindrical lower segment, the cervix

• Uterine cavity is flattened and triangular 

• Receives the product of conception from one of the oviducts for implantation

MYOMETRIUM

• 1.25 cm thick middle layer of uterine wall

• Consist of flat or cylindrical bundles of interlacing smooth muscles

ENDOMETRIUM

• 4.5 mm thick mucosal lining of the uterine cavity 

• Consist of : 

  • Endometrial glands lined by simple columnar cells 

  • Endometrial stroma

Functions of Endometrium

• Prepare for the reception of the fertilized ovum 

• Participate in its implantation and nutrition

• Form the maternal portion of the placenta

Functionalis

•  the upper to ⅔ of the endometrium that is sloughed off during menstruation

Basalis

•  a deeper portion of the endometrium that remains and regenerates

CYCLIC CHANGES IN THE ENDOMETRIUM ( 28 DAY CYCLE )

• Menstrual Phase (Days 1-5): Shedding of the functional endometrial layer due to low hormone levels, resulting in menstrual bleeding.

• Proliferative Phase (Days 6-14): Estrogen stimulates endometrial regeneration and thickening, preparing for potential pregnancy.

• Secretory Phase (Days 15-28): Progesterone supports endometrial gland secretion for embryo nourishment; if no pregnancy, endometrium sheds, starting the cycle again.

PROLIFERATIVE PHASE

• Coincides with estrogen secretion

• Beginning at the end of menstrual flow and continuing for 12-14 days

• There is a 3-to-4-fold increase in the thickness of the endometrium

• Endometrial glands lengthen and are straight and narrow

SECRETORY PHASE

• Estrogen surge that catalyzes LH surge

• Coincides with secretion of progesterone

• Endometrium further thickens but this is due mainly to edema of the stroma and accumulation of secretion in the glands

• Glands continue to grow becoming tortuous and sacculated

MENSTRUAL PHASE

• Period of degeneration associated with rapid decline in stimulation of the endometrium by ovarian hormones

• Occur about 2 weeks after ovulation

• Endometrium is denuded of surface epithelium, glands collapsed and short

PLACENTA

• The implanted blastocyst continue to enlarge at the expense of the surrounding endometrium

• From the 15th day, cords of trophoblasts grow that will form the chorionic villi of the placenta

• Structure: An organ that develops during pregnancy, attached to the uterine wall, and connected to the fetus via the umbilical cord.

• Function: Facilitates nutrient, gas, and waste exchange between the mother and fetus; produces hormones such as human chorionic gonadotropin (hCG), estrogen, and progesterone to support pregnancy.

• Components: Includes the maternal decidua (uterine lining) and fetal chorion (fetal membranes), forming a barrier that protects the fetus while allowing exchange of substances.

• Inner Cytotrophoblast

• Outer Syncytiotrophoblast

2 Types of Trophoblast

Inner Cytotrophoblast

• Structure: The innermost layer of trophoblast cells in the placenta, consisting of mononucleated cells.

• Function: Responsible for the formation of the syncytiotrophoblast and contributes to the implantation of the embryo into the uterine wall. It also plays a role in the formation of the placental villi and is involved in maternal-fetal nutrient exchange.

• Location: Found in close contact with the fetal blood vessels and the syncytiotrophoblast layer in the placenta.

Outer Syncytiotrophoblast

• Structure: The outer layer of the trophoblast, composed of multinucleated, syncytial cells that lack distinct cell borders.

• Function: Facilitates implantation into the uterine lining by invading the maternal endometrium. It produces hormones such as human chorionic gonadotropin (hCG), which supports pregnancy by maintaining the corpus luteum and regulating the maternal immune response to the fetus.

• Location: Covers the outer surface of the placenta and directly interfaces with the maternal blood in the intervillous spaces.

CERVIX UTERI

• Surrounds a cervical canal about 3 cm in length

• Continuous above with the uterine cavity through a constriction called the internal os with the vagina below through the external os

• Lined by simple columnar cells, near the external os there is an abrupt transition to stratified squamous, the transformation zone

VAGINA

• Distensible fibromuscular tube 

• 8-9 cm in length

• Mucosa is lined by nonkeratinized stratified squamous epithelium

• Muscular coat consist of interlacing bundles of smooth muscles

Clitoris

• Corresponds to the dorsal portion of the penis ; has 2 erectile corpora cavernosa

• Structure: A small, erectile organ located at the anterior junction of the labia minora. It consists of a glans, a body, and crura (which extend internally). The glans is the exposed part, while the body and crura are internal structures made of erectile tissue.

• Function: This structure is primarily involved in sexual arousal and pleasure. It contains a high concentration of nerve endings, making it the most sensitive part of the female genitalia. It becomes engorged with blood during sexual arousal, contributing to sexual sensation and response.

• Location: Situated at the top of the vulva, just above the urethral opening.

Nonkeratinized Stratified Squamous Epithelium

lines the Labia Majora and Minora

Vestibule Between the Labia Minora

• Area where the urethra and vagina open

• Structure: The area located between the labia minora in the female genitalia. It contains the openings of the urethra, vagina, and various glands (such as Bartholin's glands). The vestibular mucosa is highly vascularized and typically pinkish in color.

• Function: Serves as the entryway to the vagina and urethra. It is involved in sexual arousal, as it contains sensitive nerve endings. Additionally, the glands within the vestibule secrete mucus that helps lubricate the vaginal opening during sexual activity.

• Location: Found between the inner folds of the labia minora, extending from the clitoral hood to the vaginal opening.

MAMMARY GLANDS

• Paired gland found on the ventral aspect of the thorax on either side of the midline

• Nipple is located in the center of a circular pigmented area of the skin called the areola

• 15-20 lactiferous ducts open into the tip of the nipple

• Compound tubulo-alveolar gland consisting of 15-20 lobes surrounded by adipose tissue

• Functional unit is the terminal duct lobular unit (TDLU)

15-20 Lactiferous Ducts

open into the tip of the nipple

Compound Tubulo-Alveolar Gland

The mammary gland is a ___________ consisting of 15-20 lobes surrounded by adipose tissue.

Terminal Duct Lobular Unit (TDLU)

• Functional unit of the breast composed of a lobule (milk-producing tissue) and its associated duct.

• Responsible for milk production and secretion.

• Size and activity regulated by hormonal changes.

• Primary site for the development of most breast cancers.