ILA10 - Reproductive Flashcards
What is the reproductive tracts derived from embryologically?
Intermediate mesoderm
How long are the gonads indifferent?
Until 6 weeks
When is the sex of the fetus determined?
At fertilization
What determines the sex of the fetus?
SRY gene on Y chromosome, which produces testis determining factor
What are the two ducts for reproductive development?
Mesonephric (Wolffian, male) and paramesonephric (Mullerian, female)
Describe the development of the male reproductive tract.
1) Sex determining region Y (SRY) on Y chromosome present
2) SRY protein coded for (transcription factor) causes testis determining factor to be produced
3a) Testis produce testosterone (Leydig cells) causing Wolffian duct to develop
3b) Testis also produce Mullerian inhibiting factor, causing Mullerian duct regression
4) Testosterone of also converted, by 5 alpha reductase, to dihydrotestosterone, which causes development of external genitalia
Describe the development of the female reproductive tract.
1) No Y chromosome so no SRY
2) No gonadal hormone influence
3) Female genitalia develop by default from genital ridges
4) Lack of testosterone= Wolffian regresses
5) Lack of MIF = Mullerian grows
6) Lack of dihydrotestosterone = female external genetalia
Name some of the ligaments supporting the female reproductive organs.
Round, suspensory, broad, cardinal
What does the urogenital sinus form in males?
Penis, foreskin and scrotum. Utethra and bladder
What does the urogenital sinus form in females?
Bladder, urethra, lower 1/3 vagina, paraurethal glands, greater vestibular glands
What does the round ligament support?
Attaches the uterus to the mons pubis and labia majora, travels via the inguinal canal
Maintains antiflexion of the uterus
What does the suspensory ligament support?
Connects ovary to pelvis wall. Contains ovarian artery and vein
What does the broad ligament support?
- It is a continuation of the peritoneum
- Connects the side of the uterus to the lateral pelvis
- Contains uterine tubes, ovary, ovarian artery and vein, uterine artery and vein, ovarian and round ligament
- Forms mesovarium
What does the cardinal ligaments connect?
Cervix to lateral pelvic wall
Contains uterine artery and vein
What do the internal and external os divide?
- Internal divides uterus and cervix
- External divides cervix and vagina
Describe the length of the fallopian tube (ovary to uterus).
Fibrae, infudibulum, ampulla, isthmus then intramural
Describe the blood supply of the female genitalia.
- Ovarian artery (straight from the abdominal artery)
- Uterine, vaginal and internal pudendal arteries from the internal iliac artery
What is the nerve supply of the female genitalia?
- Sympathetic is hypogastic plexus
- Parasympathetic is pelvic splachnic nerve
What is the ovaries covered by?
Modified mesothelium
Describe the stroma of the ovaries.
- Cortex is composed of spindle stromal cells and ovarian follicles
- Medulla is composed of loose fibroelastic tissue with blood vessels, lymphatics and nerves
Describe the stages of maturation for a follicle
1) Primordial follicles -lie in periphary of cortex
-simple squamous layer, granulosa cell coat
2) Primary follicles -due to FSH cell proliferate and zona pellucida forms
3) Secondary follicle -antrum forms, theca interna and externa form, all supported by cumulus oophorus
4) Graafian- thick zona pellucida, layer of granulosa cells=corona radiata (not the one in the brain)
Follicle leaves
5) Corpus luteum -if pregnancy occurs it will enlarge
6) Corpus albicans -produces progesterone
What cell types are in the fallopian tubes?
- secretory (uterine end)
- ciliated (infundibular end)
What does the uterus contain?
Endometrium and myometrium
What are the two coverings in the cervix?
1) Endocervix -simple columnar ciliated with crypts
2) Ectocervix -dense smooth muscle stroma, non-keratinising strat. squamous
These for the transformation zone, separation varies in life
What are the layers in the vagina?
- Mucosa (non-keratinising strat. squamous)
- Muscle (smooth, inner circular, outer longitudinal)
- Adventitia (loose connective tissue)
Where is gonadotropin-releasing hormone (GnRH) released from?
Hypothalamus
What does GnRH stimulate?
LH and FSH release from anterior pituitary
What does FSH stimulate?
Follicles to mature
What does LH stimulate?
Release of egg from Graafian follicle by:
Increasing antral fluid volume and fusion of follicular and ovarian membrane
When is there a LH surge?
Around 18 hours before ovulation
Where do FSH and LH act on the oocyte?
FSH- granulosa cells
LH- theca cells, stimulates oestrogen secretion
What does oestrogen do to the endometrium?
-Proliferation
-Increased stroma bulk and vascularisation
-Glands and mitotic figures
Production of progesterone
What does oestrogen do to the cervix?
Secretion of a watery mucus (before and around ovulation) to increase sperm entry
What does oestrogen do to the vagina?
Causes epithelium to proliferate and become more stratified
What does oestrogen do to the fallopian tubes?
Causes the smooth muscle to contract
Where is progesterone released from?
Corpus luteum
What is the effect of progesterone on the endometrium?
Causes the endometrium to become secretory (from proliferative) (spiral arteries, glands become twisted
What is the effect of progesterone on the cervix?
Thick mucus secretions to form a plug to bacteria
What is the window sperm must enter the uterus for pregnancy?
5 days before to 1 day after ovulation
What is responsible for a low number of spermatozoa reaching the upper female reproductive tract?
Sperm motility and female tract
What us capacitation and where does it happen?
When sperm enter uterus they undergo final maturation
Glycoprotein layer of membrane is removed to expose receptors for egg
Acrosome cap is altered
How do oocyte move along the fallopian tubes?
Peristaltic contractions and cilia
Where do sperm usually meet the secondary oocytes?
Bonus points for what directs it.
Ampulla of fallopian tubes
Chemotaxis
What do the sperm bind to on the egg?
Zona pellucida. ZP1- primary binding, ZP2- secondary binding (acrosome).
- triggers autosomal reaction which releases digestive enzymes
- this triggers Ca2+ release and cortical granules to harden ZP and digest sperm receptors to prevent second sperm entry
What does the entering of the sperm trigger?
Second meiotic division for the egg, producing second polar body and mature ovum
When are pronuclei formed?
4-7 hours after gamete fusion, from 2 sets of haploid chromosomes
Describe syngamy.
- Male and female proniclei migrate to centre, forming the zygote
- Haploid chromosomes pair and replicate DNA in preparation for first mitotic division
- Pronuclear membranes break down, 46 chromosomes align at the equator
When does cleavage occur?
Day 2-3 after fertilisation
What happens during cleavage?
- Ooplasm divides into 2 equal halves, then a series of mitotic divisions follows
- Cells get smaller with each cleavage
- Individual cells are a blastomere, each are totipotent
- Morula
- High levels of progesterone relax the fallopian tubes allowing the conceptus to reach the uterus
- Pre 4-8 cells maternal RNA control, post = activation of embryonic genome
How many cells is a morula?
8-16
What happens on day 4?
Compaction. Cells flatten, maximisation of intracellular contacts, with tight junctions forming
What day does cavitation and differentiation occur?
5
What happens during cavitation and differentiation?
-Tight junctions between outer cells form trophectoderm
-Fluid filled cavity expands, fluid from trophectoderm
-Becomes blastocyst
-Intercellular spaces have become confluent, meaning one cavity (blastocoele)
-Blastocyst =inner(embryo proper, pluripotent)
outer(trophoblast)
How many cells is a blastocyst?
More than 80 cells (50-66% is trophectoderm, rest is inner cell mass)
What happens from day 6 onwards?
1) ZP thins, blastocyst expansion and enxymatic factors cause embryo to hatch from ZP
2) Nutrients supplied by: -cumulus cells
- Fallopian tube secretions
- Uterine secretions
3) Growth factors and cytokines (IGF I and II, LIF)
When does implantation occur?
Day 8-9
What happens during implantation?
1) Apposition
2) Attachment
3) Differentiation of trophoblast
4) Syncytiotrophoblast implants bastocyst
5) Decidual reaction
6) Maternal recognition
7) hCG production
What is the genetic control early cleavage vs blastocyst?
Maternal then embryonic
What is the metabolic activity early cleavage vs blastocyst?
Low then high
What is the biosynthetic activity early cleavage vs blastocyst?
Low then high
What is the nutrient requirement early cleavage vs blastocyst?
Simple then complex
What happens during apposition?
- hatched blastocyst orientates via embryonic pole
- sychronised positioning (cavity towards lumen)
- day 19-22 window
What happens during attachment?
- Apical surface of hormonally conditioned endometrial cells express variety of adhesion mols.
- trophoblast cells express integrins
- bridging occurs
What does the trophoblast differentiate into?
- Cytotrophoblast (inner)
- Sycytiotrophoblast (outer)
How syncytiotrophoblast implant into the epithelium of the uterus?
Projections of chorionic villi into the epithelial cells, these penetrate the basal lamina
Invades and erodes endometrial stroma (enzymatically mediated)
What happens in the decidual reaction?
- Progesterone primed endometrial stromal cells adjacent to blastocyst turn into metabolically active secretory cells (Decidual cells)
- Endometrial glands in the vicinity enlarge and local uterine wall becomes more vascularised
- Secretions including growth factors and other nutrients for growth
What happens during the maternal recognition phase of implantation?
- Embryo is antigenically different from mother
- Concurrent with decidual reaction, leucocytes in endometrial stroma secrete interleukin 2, which prevents maternal recognition as foreign
What produces hCG? WHat does it do?
Trophoblast. Supports corpus luteum, which produces progesterone which is needed for the endometrium and so pregnancy
Name some hormonal contraception methods.
1) Combined oestrogen and progesterone, -ive feedback to GnRH, stops FSH and so ovulation
2) Progesterone only, -ive feedback again
3) Coil- local effect on endometrium
4) Perichondrium- increased vascularisation, meaning mesenchymal cells turn into osteoblasts
