Development of Tracts Flashcards
What are gonadotropins?
Hormones secreted by the anterior pituitary gland which control development and secretory functions of ovaries and testes
What does sexual dimorphism mean?
There are 2 different shapes possible
What are the secondary sexual characteristics of men?
Facial hair
Male pattern baldness
Pubic hair
Increased body size
What are the secondary sexual characteristics of women?
Subcutaneous fat distribution
Breasts
Pubic hair
What is the urogenital ridge?
Region of intermediate mesoderm giving rise to both the embryonic kidney and the gonad
Gonads are derived from …
Intermediate mesoderm and primordial germ cells
What are primordial germ cells?
Special population
Arise in yolk sac and migrate into the retroperitoneum - along the dorsal mesentery
(Risk that PGCs may get lost - ectopic sites)
Which gene determines whether development is male of female?
SRY gene on the Y chromosome
Present = male
Absent = female
Describe development of gonad in male
Medullary cord develop
No cortical cords
Thick tunica albuginea - encloses gonad tightly
Describe development of gonad in women
Cortical cords develop
Medullary cords degenerate
No tunica albuginea (oocytes need to be able to burst out)
Which ducts develop in early embryo?
Mesonephric and paramesonephric ducts in both male and female (to start with)
Where do the ducts end in the embryo?
Both mesonephric and PMDs end at cloaca
What is another name for mesonephric ducts?
Wolffian ducts
Part of embryonic kidney
What happens to the mesonephric ducts in males and females?
Males: mesonephric ducts maintained
Females: as UGS expands that mesonephric ducts regress
What is another name for the paramesonephric ducts?
Müllerian ducts
Where do the PMDs open cranially and caudally?
Caudal = contact with cloaca Cranial = opens into abdominal cavity
What do PMDs differentiate into?
Fallopian tubes
Uterus
Cervix
Part of vagina
Which tissue does the vagina derive from?
Endoderm of UGS
Mesoderm of PM duct
What happens to the ducts in a male?
Testis develops - androgen secretion supports mesonephric ducts
Testis secretes Mullerian Inhibiting Substance which causes the PMD to degenerate
What happens to the ducts in a female?
No androgen therefore mesonephric duct degenerates
No testis derived MIS therefore PMD develops
What are the 3 basic components of indifferent external genitalia?
Genital tubercle
Genital folds
Genital swellings
Describe the development of the external genitalia in a male
Genital tubercle elongates
Genital folds fuse to form spongy urethra
Influence of androgens (components must have the correct receptors for the androgens)
Describe development of external genitalia in women
No fusion occurs
Urethra opens into vestibule
No elongation of GT
Describe the descent of the testes
Retroperitoneal
Testes attached by caudal genital ligament and gubernaculum to scrotal folds
Processus vaginalis pushes through anterolateral abdo wall into scrotal swelling - testis follows it, tethered by gubernaculum (through inguinal canal)
PV obliterated
