Reproduction in the female L15 Flashcards
Anteflexed uterus
In an anteflexed uterus, the uterus is tilted forward so that it is bent or flexed anteriorly (toward the bladder).
Retroflexed uterus
In a retroflexed uterus, the uterus is tilted backward so that it is bent or flexed posteriorly (toward the spine).
Some women with a retroflexed uterus might experience discomfort or pain during menstruation or intercourse, though many remain asymptomatic.
Female reproductive organs
Vagina, uterus, uterine (fallopian) tubes, ovaries
Functions of the vagina
Elastic muscular 7.5-9cm tube extending from the cervix to the exterior of the body with three main functions.
- Serves as a passageway for the elimination of menstrual fluid.
- Receives the penis during sexual intercourse, and holds spermatozoa (sperm) before they pass into the uterus.
- Forms the lower portion of the birth canal through which the fetus passes during delivery.
Functions of the uterus
Small, pear-shaped organ that weighs 30-40g. The cervix prevents the entry of sperm and bacteria and viruses through the cervical mucus. Forms a constriction during childbirth - prevents the baby from being released prematurely. It then softens and relaxes to allow the exit of the baby in the process of childbirth.
Endothelium and myometrium in the uterus
The endometrium can be subdivided into the inner functional zone (stratum functionalis), that contains most of the uterine glands and the outer basilar zone (stratum basalis; adjacent to the myometrium). The basilar zone attaches the endometrium to the myometrium.
Predicting fetal growth
Fundal height - the top of the uterus to the pubic bone. The number of centrimetres is approximately the number of weeks gestation (the period during which a fetus develops inside the mother’s womb, from conception until birth). Increased with twins, breech birth, gestational diabetes. Decreased for small for gestational age and intrauterine growth restriction.
Main functions of the uterus
- Pathway for sperm transport
- Provides mechanical protection, nutritional support, and waste removal for the developing embryo and fetus.
- Contractions in the muscular wwall (myometrium) of the uterus are important in ejecting the fetus at the time of birth.
- Source of menstrual fluid
Endometrium subdivision
Inner functional zone (stratum functionalis) which contains most of the uterine glands.
Outer basilar zone (stratum basalis; adjacent to the myometrium). The basilar zone attaches the endometrium to the myometrium.
The uterine (fallopian) tube
Fertilisation typically occurs in the ampulla. The uterine tube provides a rich, nutritive environment containing lipids and glycogen, for spermatozoa, oocytes (immature egg cell) and the developing embryo.
Structure of the uterine (fallopian) tube
The epithelium lining of the uterine tube has both ciliated and non-ciliated secretory columnar cells to allow for both movement and nutrition of the oocyte, sperm, and embryo.
The mucosa (tissue that lines internal organs of the body) is surrounded by concentric layers of smooth muscle.
Transport along the tube involves a combination of both cillary movement and peristaltic contractions.
Ectopic pregnancy
When the fertilised embryo is implanted in any tissue other than the uterine wall.
Most ectopic pregnancies occur in the uterine tube (tubal pregnancy).
Smoking, advanced maternal age and prior tubal damage are risk factors.
Ovarian follicles
Small fluid-filled sacs within the ovaries that contain immature egg cells (oocytes). Each follicle nurtures and protects the oocyte as it develops and prepares for ovulation.
Structure of the ovary
Oval and weigh approx 5-10g. The ovary is comprised of three distinct regions. The outer ovarian cortex contains the ovarian follicles, the central ovarian medulla consists of ovarian stroma and steroid-producing cells, and the inner hilum (hilus) which acts a point of entry for nerves and blood vessels.
Primordial follicle
The oocyte once surrounded by follicular (granulosa) cells form the primordial follicle.
Primary follicles
As the follicles grow, they are called primary or pre-antral follicles. Immature primary follicles consist of only one layer of granulosa cells.
Function of the primary follicle
The oocyte secretes glycoproteins, which form a translucent acellular layer (zona pellucida).
Condensation of ovarian stromal cells, known as thecal cells, begin to form around the follicle.
In response to FSH, some follicles get larger producing many layers of granulosa cells surrounding the oocyte.
Secondary follicle
As granulosa cells proliferate (increase in number) they produce a viscous follicular fluid that coalesces (merges) to form a single follicular antrum. These are called secondary or antral follicles.
The innermost layer of granulosa cells becomes firmly attached to the zona pellucida and is called the corona radiate.
The mass of loosely associated granulosa cells is known as the cumulus oophorus.
Thecal cells of the secondary follicle
The theca develops to become the inner glandular, highly vascular theca internal, and the surrounding fibrous capsule, the theca external.
Mature (Graafian or pre-ovulatory) follicle
As the follicular antrum grows, the oocyte becomes suspended in fluid. It is connected to the rim of peripheral granulosa cells by a thin stalk of cells.
Ovulation
The increasing size of the follicle and its position in the cortex of the ovarian stroma causes it to bulge out from the ovarian surface.
Following ovulation
The follicle ruptures, carrying with it the oocyte and its surrounding mass of cumulus cells.
The oocyte is collected by cilia on the fimbria, which sweep the cumulus mass into the uterine tube.
Blood clot in the corpus luteum
The antrum breaks down, the basement membrane between the granulosa and thecal layers breaks down and the blood vessels invade.
The granulosa cells from large lutein (yellow pigment) cells (Corpus luteum = yellow body)
This transformation is referred to as luteinisation and is associated with an increasing secretion of progestagens.
Corpus Albicans
The remaining whitish scar tissue, the corpus albians (white body), is absorbed back into the stromal tissue of the ovary over weeks to months. If fertilisation does not occur, then the cycle starts all over again.
Fertilisation
If the oocyte is fertilised and begins to divide, the corpus luteum persists past its normal 2 week life span.
It is rescued from degeneration by human chorionic gonadotropin (hCG). The hormone is produced by the chorion of the embryo beginning about 8 days after ferilisation.
The presence of hCG in maternal blood or urine is an indicator of pregnancy and is the hormone detected by home pregnancy tests.
The menstrual cycle
Avergae cycle is about 28 days. Two phases in the ovarian cycle: follicular phase (day 1 to ovulation) and luteal phase (ovulation to menstruation). Three phases in the uterine/menstrual cycle; menstruation, proliferative and secretory.
Why a menstrual cycle
Variation in length of menstrual cycle
The length of the luteal phase is usually 14 days. The length of the follicular phase is variable, and changes as the female ages.
Female reproductive cycle in a nutshell
No fertilisation occurs
1. Corpus luteum regresses, oestrogen and progesterone levels are low, see increased FSH.
2. FSH stimulation (negative feedback on the hypothalamus and pituitary) leads to increased follicular growth.
3. Around day 6-7, see selection of dominant follicle (grows bigger), with increased oestradiol from granulosa cells.
4. Oestradiol suppress FSH (and LH) production in the pituitary and FSH declines.
5. Oestrogen levels rise, by ~day 12, a threshold concentration of oestradiol is exceeded. If this is maintained for ~36 hours, there is a temporary switch from negative to positive feedback
6. Oestrogen mediated positive feedback triggers a rise in GnRH leading to an LH surge
7. LH surge induces ovulation
High levels of oestrogen exert a positive feedback effect on the hypothalamus and anterior pituitary, thereby increasing secretion of GnRH and LH.
When does Oogenesis - creation of female gametes, begin in females?
before birth! females are born with millions of follicular cells at birth. So oogensis has begun, it’s just that it can’t go any further than a primordial follicle due to the absence of FSH
The secretory cells of an ovarian follicle are located in the region called the:
The theca interna, a glandular layer of thecal cells which secrete androgens
When would progesterone be at its highest levels during the menstrual cycle?
Progesterone levels are highest late in the postovulatory phase, also known as the luteal phase. This occurs after ovulation and before menstruation, typically around days 21-23 in a standard 28-day menstrual cycle. During this time, the corpus luteum is actively producing progesterone to maintain the uterine lining for potential implantation.
During the menstrual cycle, when would the endometrium be at its thickest?
Late in the postovulatory phase, the corpus luteum has formed, producing good amounts of progesterone. Progesterone and oestradiol will continue to act on the endometrium, proliferating it and preparing it for pregnancy however it also at this stage that the increasing levels of progesterone inhibit FSH release from the pituitary. From there, menstruation occurs which is a shedding of the endometrial layer.
What is the main function of progesterone during the menstrual cycle?
The purpose of progesterone is to prepare for pregnancy. One of the ways it does this is by thickening and maintaining the thickness of the endometrium.
Onset of puberty in both sexes is signalled by increases in levels of which hormone?
LH
The interstitial cells of the testes are an important target for which hormone?
LH
What is the role of follicle-stimulating hormone?
Acts on the ovaries to stimulate the growth and development of gametes.
Acts on the testes to stimulate the production of gametes.
What is the role of luteinising hormone?
Acts on the testes to promote the synthesis of testosterone.
Acts on the ovaries to trigger ovulation and promote the sythesis and release of ovarian hormones.
When do the ovaries of human females contain the greatest number of oocytes?
Before birth
The LH surge is primarily responsible for which event duing the menstrual cycle?
Triggering ovulation
