Flashcards in 1.1 Deck (72):
What do gametes form from?
Diploid germ cells
When do germ cells arise and where?
3 weeks after conception
Why must germs cells separate from somatic cells early in development?
To protect them from the influence on hormones acting on the somatic cells.
To where do the primordial germ cells migrate? What kind of tissue forms these?
Formed by somatic mesenchymal tissue.
How many female gametes are produced per year? Why is this? How long are they capable of fertilisation?
12-14 (400 over reproductive life span)
Necessity to nurture embryo and fetus limits the number produced.
Ova are capable of fertilisation by sperm for about 36 hours after they are released from the gonad.
Describe male fertility.
Males are continuously fertile to exploit intermittent female fertility.
Large numbers of sperm must be produced as only a tiny proportion survive the journey.
Give male secondary sexual characteristics.
Large body size
Body composition and fat distribution
Male pattern baldness
Hair and skin
Give female secondary sexual characteristics
Small body size
Subcutaneous fat distribution
Hair and skin
What does the urogenital ridge give rise to? What tissue is it formed rom?
Gonads and kidneys
What tissues are the gonads derived from
Intermediate mesoderm fromt eh urogenital ridge and primordial germ cells.
Where doe the primordial germ cells arise?
Where do they migrate to
Arise in the wall of the yolk sac near the allantois and migrate into the retroperitoneum along the dorsal mesentery.
What determines gonadal sex?
Presence of Y chromosome even if XXY
What gene leads to the development of the male and where is it located
SRY gene on the short arm of the Y chromosome
Do medullary cords develop in testis/ovary
Develop in testis, degenerate in ovary
Do cortical cords develop in testis//ovary
None in testis, develop in ovaties
Does the tunica albuginea develop in the testis or ovary
Give the 2 duct systems that develop in embryos.
Mesonephric (Wolffian) Duct
Paramesonephric (Mullerian) Duct
Where do the duct systems end
A blind pouch where the GI, urinary and repro tracts converge and end
Describe the function of the mesonephric system
Mesonephric tubules + Mesonephric duct serve as emrboynic kidney
What is the urogenital sinus? How is it formed?
The cloaca is split into the urogenital sinus and the anorectal canal in the division of the GI and urinary/repro tracts by the urorectal septum.
What is the urogenital sinus continuous with? How? What does this become in adults?
Continuous with umbilicus via the urachus that becomes the median umbilical ligament in adults, tethering the bladder to the anterior abdominal wall.
What develops from the urogenital sinus in males and females?
Under the influence of testosterone in males, the prostate develops from the urogenital sinus.
In females it forms the lower part of the vagina.
Describe the development of the duct system in the male.
- Mesonephric ducts reach the urogenital sinus.
- Ureteric bud sprouts from MD
- Smooth musculature appears and the UGS begins to expand
- Teststerone maintains the mesonephric duct.
- This leads to the development of prostate and prostatic urethra from UGS.
- Paramesonephric duct regresses in the presence of testis derived Mullerian Inhibiting Hormone
Describe the development of the duct system in the female
Mesonephric ducts regress in the absent of androgens.
Paramesonephric ducts draw together and fuse and the loss of the uterine septum leads to the formation forming the uterus and uterine tubes.
Describe the path of the paramesonephric ducts.
Cranially open into abdominal cavity
Runs down length of embryo
Meet at cloaca
What prevents the paramesonephric ducts from developing
Mullerian Inhibiting Substance.
What happens hormonally in an XY embryo?
Androgen secretion supports mesonephric duct
Testis secretes MIH causing paramesonephric duct ot degenerate
What happens hormonally in an XX embryo
No androgen - mesonephric duct degerates
No MIH so paramesonephric ducts maintained
Describe Turner's Syndrome. Presenting signs? When?
Ovaries develop normally until week 15
Ovaries begin to degenerate
At birth, very little remains.
Presenting signs at puberty:
Failure of secondary sexual characteristics
Diagnosis earlier due to:
Peripheral lymph oedema
Redundant neck skin
What develops in and XY, XX or XO mosaic chromosome
Both ovarian and testicular tissue
Draw and label male repro system
Function and components of male external genitalia
Deliver semen into vagina
Penis and scrotum
Draw and label female repro system
Function and components of female internal genitalia
Provide environment where sperm may travel and fertilise ovum, concepts can implant and embryo can develop
Function and components of female external genitalia
Provide means of introducing sperm into female repro tract and formation of birth canal.
Vagina, vestibule, labia minora and majora, clitoris
What do male and female internal genitalia form from
Male from Wolffian/Mesonephric ducts
Female from Mullerian/Paramesonephric ducts
Describe the development of internal genitalia in females.
Wolffian ducts regress spontaneously.
Mullerian ducts develop into oviducts, uterus, cervix and upper vagina
What develops in the absence of gonads
Mullerian ducts --> Female genitalia
Describe the development of internal genitalia in males.
MIH inhibits mullerian duct development and causes them to regress
Testosterone androgen maintains the Wolffian ducts.
Where is MIH secreted from
Sertoli cells in the walls of the seminiferous tubules
Where is testosterone secreted from?
Leydig cells in the testes
What is the function of the tete testis
Join the seminiferous tubules to the Wolffian ducts, which form the epididymis, vas deferens and seminal vesicles.
What do Wolffian ducts develop into?
Epididymis, vas deferens, seminal vesicles
What do Mullerian ducts develop into?
Oviducts, uterus, cervix, upper vagina
Describe the development of male eternal genitalia
Under testosterone influence:
Labioscrotal swelling --> Scrotum
Genital tubercle --> Glans penis
Genital tubercle elongates and genital folds fuse to form ventral aspect of the penis and spongy urethra
Describe the development of female external genitalia
Absence of testosterone
No fusion of genital folds - urethra opens into vestibule
Urethral folds --> labia minora
Labioscrotal swelling --> labia majora
Genital tubercle --> Clitoris
What is the gubernaculum in males, function and vestigial remnant?
A fibrous cord that tethers the developing testis to the labioscrotal folds. Scrotal ligament is adult vestigial remnant.
Where do the testes arise
Upper lumbar regions
Describe the descent of the testes.
1. Musculofascial layer evaginates into the scrotum as it develops, together with peritoneal membrane to form the processus vaginalis.
2. Testis begins retroperitoneally, migrates over the pubig bone and reaches scrotum via deep inguinal and superficial inguinal rings surrounded by processes vaginalis.
(Pulled by gubernaculum)
3. Above the testis, fascia and peritoneum become closely opposed.
4. Fascial layers, obliterated stem of processus vaginalis, vas deferens, testicular vessels and nerves front eh spermatic cord occupy the inguinal canal.
What muscle laters are involved in the processes vaginalis
Intenral oblique, transversus abdominis and external oblique.
What does the processus vaginalis become?
What is found in the inguinal canal in males
Fascial layers, obliterated stem of processus vaginalis, vas deferens, testicular vessels and nerve from the spermatic cord.
Where do ovaries begin development and to where do they descend
Begin high up in posterior abdominal wall. Descend to pelvis.
Pulled by gubernaculum
Describe the gubernaculum function and adult remnant in females
Fibrous cord ataching ovary inferiorly to labioscrotal folds.
Becomes ovarian ligament (ovary --> uterus) and round ligament of uterus (uterus ---> labia).
What occupies the inguinal canal in females
the Round ligament of uterus only
What are the main repro hormones produced in the hypothalamus
Prolacitn releasing hormone
Prolactin inhibitng hormone
Main reprohormones from pituitary
Post pit - oxytocin
Ant pit - FSH LH Prolactin
Main repro hormones from testes
MIH Testoterone Inhibin
Main repro hormones from ovaries
Oestrogen Progesterone Inhibin
Main repro hormones from placenta
hCG Oestrogen and Progesterone
How are the testes suspended in the scrotum?
By the spermatic cords/scrotal ligament
Describe the tunica vaginalis
The surface of each testis is covered by visceral layer of tunica vaginalis except where each attaches to the epididymis and spermatic cord.
The parietal layer is adjacent to the internal spermatic fascia and is more extensive, extending superiorly for a short distance.
There is a small amount of luis between the tow layers.
Derived from processus vaginalis of peritoneum
Describe the tunica albuginea
Tough, fibrous outer surface.
Thickens into ridge on internal, posterior aspect as mediastinum of testis.
From this, fibrous septum's extend inwards into testis between lobules of seminiferous tubules.
Seminiferous tubules are joined by straight tubules to the rete testis, which joins to the the epididymis.
Give two cell types in the testes and their function
Sertoli cells: in seminiferous tubuels, secrete MIH, spermatozoa development
Leydig cells : interstitial, secrete testosterone.
What week do external genitalia differentiate?
What happens in the indifferent stage to form the male external genitali
Dihydrotestosterone --> Genital tubercle elongates
What are cloacal partitioning defects?
Failure of cloaca to split into repro-uri and GI tract
What is hypospadias
Abnormally placed urinary holes to to failuree of fusion of genital folds
What is bicorunate uterus
Uterus fails to fuse - two separated by uterine septum
Functions of GnRH
Releases LH/FSH from ant pit