Anatomy and pattern recognition of the Female reproductive system and embryology Flashcards
Functions of the female reproductive system
. Produces secondary oocytes and hormones
. Provides sites offertilisation, implantation and
development and delivery of the fetus
The uterus
Functions
• Pathway for sperm to reach the fallopian
tubes
• To receive, retain, protect and nourish the
fertilised ovum and developing embryo / fetus
• To expel the mature fetus at the end of
pregnancy
Blood supply to the uterus
Arterial blood passes into the internal iliac artery
and then into the uterine arteries
The uterus has an extensive blood supple
which is essential to support regrowth of the
endometrium and implantation of the ovum
and development of the placenta
Functions of the cervix
. Acts as a mechanical barrier to infectious microorganisms present in the vagina
. The external os is a very small opening with thick sticky mucous – plug
. During ovulation, the plug becomes watery to facilitate sperm travel under the influence of oestrogen
Fallopian tubes
Function
• Transport the mature ova from the ovaries to the uterus
• The site where fertilisation commonly takes place if spermatozoa are present
Blood supply to the fallopian tubes
• Blood supply is from branches of the
ovarian and uterine arteries
• Blood drainage is via the ovarian and uterine veins
How do the fallopian tubes work?
• An oocyte is released from the ovary into the
peritoneal cavity
• The fimbriae of the tubes drape over the ovary
• The oocyte is captured by the fimbriae and
swept into the tube
• Cilia line the fallopian tubes
• The cilia move in a beating movement in the
direction of the uterus to create current in the
surrounding peritoneal fluid towards the ampulla
• The smooth muscles of the fallopian tube
generate peristalsis movements which move the
ovum along the tube towards the uterus
The ovaries – functions
Oogenesis = Production and release of mature ova (egg)
Endocrine function = • Secretion of hormones
• Oestrogen
• Progesterone
Ovaries – blood and nerve supply
• Nerve supply to the ovaries runs with the vasculature and enters at the hilum
• Lymphatic drainage is to the lateral aortic and iliac nodes
• Blood supply is via the ovarian artery which branches form the descending aorta
• The ovarian artery and vein enter at the hilum
• Left ovary drains into the left renal vein
• The right ovary drains into the inferior vena cava
Pathophysiology of follicle development
• Small groups of follicles mature in a cyclic manner under the influence of FSH after puberty
• The follicles develop from a primordial follicle, to a secondary follicle and then 1 follicle becomes the tertiary or Graafian follicle.
• The Graafian follicle contains the primary oocyte and fluid.
• The primary oocyte divides by meiosis to form a secondary oocyte which is released into the abdominal cavity during ovulation (day 14 of the menstrual cycle)
• The Graafian follicle ruptures and the released oocyte is caught and transported to the uterus.
• The tissue left over from the rupture of the Graafian follicle forms into a mass called the corpus luteum. This will persist if there is fertilisation and implantation or will regress into a fibrous scar called corpus albicans if implantation does not occur
The menstrual cycle
• The menstrual cycle is regulated by the complex interaction of hormones:
Pituitary hormones
• Follicle stimulating hormones (FSH)
• Luteinizing hormone (LH)
Ovarian hormones
• Oestrogen
• progesterone
The menstrual cycle
• It consists of 2 cycles
• The uterine cycle
- The menstrual, proliferative and secretory phases
• The ovarian cycle
- The follicular phase, ovulation and the luteal
phase
release of hormones = support pregnancy
purpose of ovarian hormones
The purpose of ovarian hormones are to
• Produce a mature ovum for fertilisation
• Prepare the endometrium for the fertilised ovum
• Support an early pregnancy
Days 1-4 – menstruation Uterine cycle
• The endometrium is shed as hormonal support is withdrawn
• Vaginal bleeding occurs
• Myometrial contractions
• Rising oestrogen levels stimulate growth of new endometrium
Days 1-4 – menstruation
Ovarian cycle – days 1-14
• Called the follicular phase
• Menstruation lasts approximately 1-7 days
• FSH and LH are released from the pituitary gland
• This induces development of the follicles
• The ovarian follicles produce oestradiol and inhibin
• This supresses FSH
• As a result normally only 1 oocyte develops
• The dominant follicle forms
Day 5-13 – proliferative
Uterine cycle
• Hormones from the hypothalamus stimulate
FSH and LH release from the pituitary gland
• There is proliferation of the cells in the
endometrium causing thickening
Day 12-15 – peri-ovulatory
Uterine cycle
• Pituitary and hypothalamus cause LH
levels to rise sharply
• Ovulation occues 36 hours after the LH surge
Ovarian cycle
• Called ovulation
• Increased levels of oestradiol reach a
maximum on day 13
• LH levels rise sharply
• Ovulation occurs 36 hours after the LH surge
Day 15-28 – secretory
Uterine cycle
• The ovarian corpus luteum produces
progesterone and oestradiol
• Progesterone levels peak around day
21 causing changes in the endometrium – blood supply increases and cells enlarge
• Without fertilisation the ovarian corpus
luteum fails and progesterone and
oestrogen levels fall
• Hormonal support is withdrawn
• The endometrium breaks down and menstruation occurs
Day 15-28 – secretory Ovarian cycle
Following release of the ovum, the dominant
follicle becomes the corpus luteum
The corpus luteum produces oestradiol and
increasing levels of progesterone
This peaks around day 21
This peak induces
Summary – normal ovarian cyclical changes
• Normal ovary develops follicles every 28 days
• The dominant follicle develops (follicular phase)
• The dominant follicle ruptures mid cycle at ovulation as LH reaches a peak and oestrogen
levels are high (ovulatory phase).
• After ovulation the corpus luteum forms (early luteal phase)
• Without fertilisation the corpus luteum regresse (late luteal)
Postmenopausal ovaries
• Decrease in size with age – often hard to see on US
Premenarchal ovaries
• Best viewed transabdominally
• Look like small structures
• During adolescence there is a growth of follicles which can be mistaken for polycystic ovaries
reproductive age ovaries
• Changes occur due to hormone fluctuations
What is embryology
The study of
• Molecular – sequencing the human genome and gene expression
• Cellular – creation of organs
• Structural
• It is the factors that make up an organism
embryogenesis
Single cell to organ primordia (0-8weeks)
foetal period
From 9 weeks to birth
teratology
The study of embryological origins and causes for birth defects
First
trimester
Includes
- Pre-embryonic
- Embryonic
• Cleavage
• Implantation
• Placentation
• Embryogenesis
Fertilisation
Fertilisation is the first step
This is when a sperm and an oocyte unite to
create a diploid cell called a zygote (46
chromosomes)
Only 1 sperm can fertilise the oocyte due to
changes in the cell membrane
This occurs in the uterine tube
Chromosomal sex of the embryo is determined at fertilisation
Initiation of cleavage then commences
Cleavage
rapid division of egg into smaller parts
• This is a series of mitotic divisions increasing the number of cells – blastomeres
Blastocyst
• The blastocyst implants in the endometrium of
the body of the uterus 6-7 days after ovulation
• The endometrial glands enlarge and there is an
increase in blood supply
• The blastocyst burrows into the endometrium
and becomes surrounded
• There are 2 parts of the blastocyst
• Embryoblast – develops into the embryo
• Trophoblast – outer later that becomes
part of the placenta.
• Implantation is complete is complete by day 14
The bilaminar embryonic disc
• The trophoblast erodes the lining of the maternal capillaries of the endometrium
• Maternal blood begins to flow through the trophoblastic system – forming a uterus / placenta circulation
• The embryoblast forms a flat disc called the bilaminar embryonic disc.
• A small cavity forms within the blastocyst to form the amniotic cavity
Development of the yolk sac
The yolk sac:
• Supplies nutrients to the embryo during weeks 2-3
• Is a source of blood cells during weeks 3-6
• Contains the first germ cells (eventual oocytes)
• Is a shock absorber
• Stops the embryo drying out
Development of the chorion
• It protects from an immune response from the mother
• Secretes proteins blocking antibody production by the mother
• Promotes the production of lymphocytes that suppress immune response in the uterus
• Produces HSG
Day 15 – gastrulation
A third layer of cells form in the embryoblast Theselayers form the body systems
• Ectoderm – nervous system, skin, skeletal
• Mesoderm – major organs
• Endoderm – lining of the digestive, urinary and respiratory tract
