Repro 1.1 Flashcards
Approximately how long are ova viable?
36 hours
What does the female internal genitalia accommodate?
travel (ova and sperm) fertilisation implantation development of the embryo delivery of the foetus
When do secondary sexual characteristics develop?
Puberty
WHat are the principle female secondary sexual characteristics?
Breast enlargement
Growth of body hair
Widening of hips
More subcutaneous fat (buttocks, hips and thighs)
What are the male secondary sexual characteristics?
Body and facial hair
Enlargement of larynx and deepening of the voice
Increased muscle mass and stature
Broadening of shoulders
What do reproductive hormones influence?
Production of gametes
Mechanism of gestation and parturition
Where are reproductive hormones produced?
Hypothalamus
Posterior pituitary (oxytocin through neural control from hypothalamus)
Anterior pituitary gland
Gonads
Placenta
What hormones are produced in the hypothalamus?
Peptide releasing factors:
GnRH - gonadotrophin releasing hormone
PRH - prolactin releasing hormone
PIH - prolactin inhibiting hormone
What is produced in the anterior pituitary gland?
Gonadotrophins:
FSH
LH
Prolactin
What hormones are produced in the male gonads?
androgens eg testosterone (leydig interstitial cells)
What hormones are produced in the female gonads?
Oestrogen (mainly oestrodiol but also oestrogen and oestriol)
Progesterone (less)
Inhibin
What is the urogenital ridge?
A region of mesoderm giving rise to both the embryonic kidney and gonad. Gonad derived from intermediate mesoderm and primordial germ cells (migrate into mesoderm)
From where do the germ cells arise?
Epithelium of the yolk sac near the base of the allantois
To where do the germ cells migrate and at what stage?
Primordial gonad, 6 weeks post conception
Where do the primordial gonads lie?
superficial and medial to the mesonephric tissue
What does the mesonephros form?
Primitive medullary cords
What does the coelomic epithelium form?
Sex cords
What happens to the sex cords if the germ cells are male?
Vigorous growth of the sex cords into the medullary region of the gonad to meet the mesonephric cords and form the definitive testis cords (precursors to rate testes)
How do the seminiferous tubules arise?
Germ cells enter the definitive testis cords
What type of cells do mesodermal cells give rise to in males?
Sertoli cells
What gene do sertoli cells express and what does it do?
SRY determines formation of the testes. In its absence, ovaries form
What happens to mesonephric cords in females?
Do not develop - regress
What happens to female germ cells?
They become surrounded by mesenchymal cells to form primordial follicles (oogonia). Germ cells are now surrounded by a single layer of granulosa cells.
What happens if there is no germ cell?
Development of primitive cords is not initiated therefore no gonadal ridges form and consequently mature gonads do not develop.
From where and how does the male internal genitalia evolve?
Wolffian or mesonephric ducts.
Interstitial cells secrete testosterone causing the Wolffian ducts to develop. The seminiferous cords join the ducts at the rete testis and the remainder forms the epidydimus, vas deferens and seminal vesicles.
What happens to the Mullerian ducts in males?
Regress due to the influence of Mullerian inhibiting hormone (MIH) secreted by the sertoli cells
From where and how does the female genitalia evolve?
Mullerian or paramesonephric ducts. These develop into oviducts, uterus, cervix and upper vagina in the absence of MIH
What happens to the Wolffian ducts in the female?
Regress due to insufficient testosterone
If there are no gonads, what develops?
Mullerian ducts
What do the urethral folds form?
labia minora or penis
What do the genital swellings form?
labia majora or scrotum
What does the genital tubercle form?
clitoris or glans penis
Where do the testes arise?
Upper lumbar region, tethered to the labiosacral folds by the gubernaculum
What evaginates into the scrotum and what does it form?
Musculo-fascial layer and a layer of peritoneal membrane to form the processus vaginalis
What forms as a result of the testes descent?
Inguinal canal containing the spermatic cord
What forms the spermatic cord?
Fascial layers, obliterated stem of the processus vaginalis, vas deferens, testicular vessels and nerves
What is the vestigial remnant of the gubernaculum?
Scrotal ligament in males and ovarian ligament (connects ovary to uterus) and round ligament (connects uterus to labia) in female
What occupies the inguinal canal in females?
Round ligament
How can individuals with ambiguous genitalia at birth be assigned a sex?
Hormone levels Karyotype Palpation of gonads Length and diameter of any phallus Position of urethral meatus Degree of labio-scrotal fold fusion Presence of vagina, pouch, urogenital sinus (ultrasound)
Why are germ cells differentiated from somatic cell line early in development?
To protect them from influences arising during development of the rest of the body as they initially remain undifferentiated
Where do the primordial germ cells migrate into?
Somatic mesenchymal tissue
What are the presenting signs of Turners syndrome (45,XO)?
Peripheral lymphoedema Redundant neck skin Congenital heart disease Failure to develop secondary sexual characteristic (may undergo some breast development) Primary amenorrhoea (usually)
What is primary hermaphroditism?
Presence of both ovarian and testicular tissue (XY, XX or XY, XO)
May appear as apparently normal men and boys and go unnoticed to puberty or later if at all.
What chromosome determines gonads?
Y - if present, male, if absent, female
What does the urogenital sinus develop into?
Lower vagina and hymen or prostate.
If an individual has genotype XY but is insensitive to testosterone, how will genitalia develop?
Wolffian ducts and mullarian ducts regress, external genitalia appears to be female but internal genitalia involves testes in the abdomen (testicular feminisation)
Partial androgen insensitivity produces variable degrees of genital ambiguity
How will the genitalia develop in a female foetus (XX) with excessive androgen secretion?
Wolffian and mullerian ducts persist. External genitalia is variably masculinised female. May be appearance of male genitalia. Internal genitalia both male and female.
Only cause of congenital ambiguity that may be life threatening at birth - hyperplasia of the adrenals, enzyme deficient in steroid production.
What would occur in a male with low levels of MIH?
Some persistence of mullein ducts
Internal genitalia of both
External male genitalia
Undescended testes because of fibrous adhesions in inguinal canal, narrowing of inguinal canal or shortening of spermatic cord
When do germ cells arise?
3 weeks after conception
How long is the vas deferens in adults?
approx. 45cm
