Repro Flashcards
When does gonadal development begin?
4th embryonic (or 6th menstrual) week
What are primordial germ cells?
The primary undifferentiated stem cell type that will differentiate towards gametes: spermatozoa or oocyte
What will happen to an embryo in the absence of the Y chromosome?
The embryo will develop in to a female phenotype
What part of the y chromosome is responsible for determining the male sex?
The sex-determining region of the Y chromosome
SRY
Without this a fetus will develop along the default or female phenotypic pathway
Are all of the genes necessary for the male phenotype on the Y chromosome?
No, many of the genes that control testicular development are on other chromosomes - but a gene in the SRY region is needed to activate them.
Where are primordial germ cells made? What from?
Yolk sac
From the endoderm that lines it
1) What is the first step of gonadal development?
Migration of undifferentiated primordial germ cells - they detach from the lining of the yolk sac, and migrate dorsally along the yolk stalk, midgut and dorsal mesentery to reach the genital ridges.
Where are the ‘genital ridges’?
Medial to mesonephric ridge
Urogenital ridge: Region of intermediate mesoderm giving rise to both the embryonic kidney and the gonad
2) What happens after primordial germ cells have migrated to the genital bridge?
Mitosis. Much mitosis forming many precursor gametes.
What can lead to complete failure of gonadal formation?
A failure of the primordial germ cells to develop and populate the genital ridges
3) What happens when germ cells reach the coelomic epithelium that lines the genital ridge?
Cellular contact causes coelomic epithelia to differentiate into primitive germinal epithelium. During this process, the germ cells become embedded in the epithelium.
This combination of cells is now the sex cords.
At this point, they are still connected to the coelomic wall.
What forms the sex cords?
The combination of germ cells and primitive germinal epithelia that is formed when the germ cells make contact with the coelomic epithelium.
E4) What happens to the sex cords in the presence of a Y chromosome?
They enlarge, split and begin to form the primitive testis
In a male embryo, what happens after the sex cords begin to form the primitive testis (hint: at this point, they are still connected to the coelomic (gonadal) wall.
Subepithelial mesenchyme arises between the germinal epithelium and sex chords - cutting them off from the gonadal surface.
The sex cords are now housed within the testicular medulla (the inner portion of the gonad).
E5) In a male embryo, what happens to:
(a) the primordial germ cells
(b) the supporting sex cord cells
…once the sex cords have been housed within the testicular medulla?
(a) The primordial germ cells within them begin to differentiate in to immature sperm cells called spermatogonia.
(b) The supporting sex cells form precursor Sertoli cells.
What is sexual differentiation dependent on once the undifferentiated gonad has begun to develop?
Secretions from the testis
In their absence, female phenotype
Pelvis
Lower limit of abdo cavity
Routes of exit for génito-urinaire dsahjdhaskjfhsfhaio
Significance of pelvic outlet
Genitourinal and gastro outlet
Band of muscles holds in place
How is the pelvic floor similar to a teacup on a saucer?
Cup = levator ani (iliococcygeus and two others)
Pelvic side wall: obturator internus and piriformis
Saucer = perineal group
Cup and saucer has potential space in between
Muscles of pelvic side walls
Obturator internus and piriformis
Muscles of the pelvic diaphragm
Levator ani is the cup in cup and saucer analogy
All run from either ilium or pubis to coccyx
Iliococcygeus
Puborectalis
Pubococcygeus
(Ischio)Coccygeus
Muscles of the perineum (both layers)
Deep layer
Superficial layer
Urogenital triangle
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What do the. Perineal muscles do?
Contributes to continence
External anal sphincter - v superficial
External urethral sphincter - a little bit deeper to ^
Ischioanal fossa
Space between levator ani and perineal group - space that fluid abscess can form
Has. Anterior and. Posterior recesses
Posterior recesses communicate but anterior dont - like horseshoe rather than doughnut
Perineal body
Fibrous insertion
Most muscles attach here - interesting because most muscles attach to bone
Makes sure pelvic floor can do what it needs to do but
Is vulnerable to damage i,e. Tearing and stretching
Neurovascular supply to pelvic floor
Posterior trunk iliac nerve
Pudendal nerve - roots S2, S3, S4 keep your guts off the floor
Functions of pelvic floor
Pelvic organ support - maintain appropriate position
Contributes to continence
Puborectalis - how does it contribute to faecal continence?
critical role in maintaining anorectal flexure
Combined with external anal sphincter important in faecal continence
How can the pelvic floor be damage?
Childbirth:
- mechanical i.e. Muscles stretched/nerve damage
- iatrogenic i.e. Episiotomy
Pelvic floor dysfunction
Pelvic organ prolapse - i.e. Pelvic viscera not in right place
Incontinence
Lymphatic drainage of uterus
Remember uterus develops as two separate tubes
They are going to run from the posterior wall where the kidneys are and it’s going to drop
Hence we will have iliac nodes and sacral nodes
Para-aortic nodes imp in fundus due to point of origin of some ligament
Fundus also drains to superficial inguinal node because of the round ligament of the uterus
Body of uterus - lymphatic node
External and internal iliac
Most common causes of unpredictable, irregular upper genital tract bleeding?
Anovulation - this is a menstrual cycle problem
Pregnancy shouldn’t have bleeding
With what feature is increased progesterone production in the post-ovulatoire (luteal) phase f the ovarian cycle associated?
Basal temp rise of 0.5 c to 1 c
What does oestrogen and progesterone do the endometrium?
Oestrogen grows and increase progesterone receptors on endometrium
Progesterone specialises the cells
What stimulates the ovaries
Gonadotropin hormones
What happens if no fertilised egg?
No HCG hence corpus leuteum dies
Lose oestrogen and progesterone
Loss of those hormones cuts blood supply due to spasms
Shedding
PID - Pelvic inflammatory disease
Infection leading to inflammation
Typically STI, ascends from endocervix to upper genital tract –> may go up to peritoneum in which case peritonitis
What happens if PID is left untreated?
Inflammation and adhesions can lead to délicate tubes being blocked - infertility
Also Tuboovarian abscess - potentially life threatening because can rupture and cause sepsis
Symptoms of PID
Lower abdo and Deep dyspareunia - pain during sex
Fever
Abnormal discharge/bleeding
PID suspected - what questions do you ask? I.e. Risk factors
Sexual partner number
Condoms?
Previous history of STI
IUD
