Histology: Female Reproductive System Flashcards Preview

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Flashcards in Histology: Female Reproductive System Deck (44):

Outline the process of oogenesis

1. Embryonic gonads contain primordial germ cells
2. PGCs undergo mitosis --> oogonia
3. 5th month of foetal development: oogonia enlarge and divide --> primary oocytes
4. Primary oocytes enter meiosis I
5. 7th month of foetal development primary oocytes surrounded by layer of flattened cells --> primordial follicles
6. Primordial follicle (encapsulation) blocks first meiotic division, keeping the follicle in prophase I
7. No further changes occur until puberty


What is atresia in the ovarian cycle?

When the remained of the follicles degenerate or regress in a cycle (only one matures enough to be ovulated)


What are the three phases in the ovarian cycle?

Follicular, ovulatory, luteal


Describe the primary follicle stage in the follicular phase

Stimulated primordial follicles --> increase in size, oocyte enlargers --> cells surrounding follicle multiple (change from simple squamous to simple cuboidal) --> granulosa cells now line follicle --> zona pellucida between oocyte and granulosa is formed


What is the zona pellucida?

A thick glycoprotein and acid proteoglycan layer between the oocyte and granulosa cells


What is stroma?

General term for the supporting tissue which is rich in fibroblast-like cells


What is the ovary surrounded by?

Cuboidal/columnar germinal epithelium


Where is the tunica albuginea located in women?

Fibrous layer beneath the germinal epithelial surrounding the ovary


Describe the growing follicle stage

Granulosa cells form multi-layered capsule around the oocyte (zona granulosa, ZG), the stroma around follicle starts to organise into theca folliculi (TF) and most follicles present are primordial


Describe the secondary (antral) follicular stage

Remaining follicles take up fluid to develop the follicular antrum; the oocyte is embedded on one side in the zona granulosa cells ( cumulus oophorous cells) and the surrounding theca organises into the theca interna and theca externa


What is the cumulus oophorous?

Group of granulosa cells that connect the primary oocyte to the rest of the granulosa cells (appears to form a stem-like structure)


What does the theca interna do?

Secretes androgen precursors


Describe the Graafian follicle stage

First meiotic division completed just prior to ovulation (secondary oocyte and first polar body) --> antrum enlarges, secondary oocyte is attached to the side by bridges of granulosa (corona radiata) and the follicle begins to bulge from the side of the ovary in preparation for rupture --> ovulation


What does the ovum consist of?

Secondary oocyte, zona pellucida and corona radiata of granulosa cells


When does the second meiotic division of the secondary oocyte complete?

At fertilisation --> fertilised egg (zygote) and second polar body


Describe the ovulatory phase

Ovarian wall thins next to Graafian follicle, and ruptures in order to expel the ovum (secondary oocyte) into the peritoneal cavity


What is the role of progesterone?

Prepares endometrium for implantation


Describe the luteal phase

After ovulation, the granulosa cells and theca cells, of the ruptured Graafian follicle remnants, proliferate and form a highly vascularised endocrine structure known as the corpus luteum (yellow body) which secreted progesterone and oestrogens


What happens in the luteal phase if fertilisation/implantation doesn't occur?

If fertilisation/implantation doesn’t occur, corpus luteum degenerates and leaves a fibrous scar known as the corpus albicans (white body)


What happens in the luteal phase if fertilisation/implantation does occur?

If implantation occurs, the developing placenta secretes hCG in order to maintain the corpus luteum and its secretion of progesterone


What is the function of the oestrogen produced by the corpus luteum?

Oestrogen maintains the uterine mucosa still


What is the function of the progesterone produced by the corpus luteum?

Progesterone promotes secretion from the mucosal glands to provide a suitable environment for a fertilised ovum to implant


Describe the formation of the corpus luteum

After ovulation, the granulosa cells of the Graafian follicle hypertrophy (called granulosa lutein cells), the theca lutein cells are derived from the theca interna cells and continue to produce mainly androgens and there is also connective tissue septa which carry blood vessels into the structure


Outline the hormonal control of the ovarian cycle

1. GnRH --> FSH and LH production
2. LH and FSH --> growth and development of ovarian follicles
3. Growing follicles produce oestrogen which, alongside inhibin production --> negative feedback to go to hypothalamus and pituitary --> inhibit LH and FSH release
4. Rising oestrogen levels --> positive feedback loop --> LH and FSH surge
5. This LH surge --> completion of meiosis I of the primary oocyte --> secondary oocyte --> production of enzymes that weaken the ovary wall, leading to ovulation
6. After ovulation, LH promotes the transformation of the ruptured Graafian follicle --> corpus luteum
7. The corpus luteum then produces progesterone, oestrogen and inhibin --> inhibits FSH and LH production as well as inhibit the development of any further follicles
8. Decrease in LH --> corpus luteum starts to degenerate --> oestrogen and progesterone levels fall --> allows FSH and LH to be produced again by the pituitary gland --> cycle starts again


What are the different parts of the uterus?

Fallopian tubes, fundus (body) of uterus and cervix


What is the stratum functionalis?

The stratum functionalis is a thick superficial layer of the endometrium that is sloughed off during menstruation and grows anew during each cycle


What is the stratum basalis?

Just superficial from the myometrium and this is not shed during menstruation and new glands develop from it


What is the fallopian tube covered by?



What is the endocervical canal?

Links the vagina to the body of the uterus


Describe the histology of the uterine cervix

Has folded mucosa, and is lined by simple columnar epithelial cells which make a mucous secretion


What is the function of the cervix?

Role of cervix is to admit spermatozoa to allow fertilisation of the ovum around time of ovulation, and to protect upper parts of tract from bacterial invasion


How does the cervix facilitate changes so that it's 'sperm-friendly' or 'sperm-hostile'?

Secretions of the glandular mucosa undergo cyclical change during the menstrual cycle to facilitate these roles (sperm-friendly, sperm-hostile)


What is the histology of the endocervical canal

By the external os, the endocervical mucosa epithelium is stratified squamous like that of the vagina due to exposure to more hostile, acidic environment


What is the vagina?

A fibromuscular canal


Describe the histology of the vagina

Lined by mucosal, stratified squamous epithelia, has dense lamina propria with many elastic fibres and a rich vasculature, lubrication of mucosa derived from cervical mucus and trans-epithelial exudate from thin-walled vessels in the lamina propria


What is the adventitia of the vagina continuous with?

This connective tissue merges with the adventitia of the bladder anteriorly and the rectum posteriorly


What is the myometrium?

Muscle layer of the uterus


Describe the histology of the myometrium

Fascicles of muscle fibres run in different directions forming ill-defined layers and it contains rich network of arteries and veins which are supported by dense fibrocollagenous tissue


How does the myometrium change during pregnancy?

Increases greatly in size in response to oestrogen and this increase in mass is mostly due to hypertrophy of the smooth muscle cells, but increased cell number (hyperplasia) also plays a role


What are the three phases of the menstrual cycle?

Menstrual phase (1-5), proliferative (6-14), secretory (15-28)


Describe the menstrual phase of the menstrual cycle

Days 1-5: functional layer of endometrium becomes detached from uterine wall and bleeding and detached tissue and blood passes through vagina as menstrual flow


Describe the proliferative phase of the menstrual cycle

Days 6-14: due to increased oestrogen levels, endometrium begins to proliferate and thicken, the tubular glands extend and spiral arteries form. The oestrogen produced stimulates the expression of endometrial progesterone receptors and ovulation occurs at the end of this phase


Describe the secretory phase of the menstrual cycle

Days 15-28: rising progesterone levels (from corpus luteum) act on endometrium to stimulate enlargement of endometrial glands and their secretion of mucus and glycogen in preparation for implantation of the fertilised ovum. If fertilisation doesn’t occur --> corpus luteum degenerates --> progesterone levels drop --> endometrium degenerates. Cycle then begins again


Describe the capacitation of sperm

This is where changes in the acrosome (of sperm) take place to permit the release of hydrolytic enzymes which allow the sperm to penetrate the zona pellucida which surrounds the secondary oocyte