1) Origin of the Sexes Flashcards
What are the male internal genitalia?
Testis Epididymis Ductus deferens Seminal glands Ejaculatory ducts Prostate Bulbourethral glands
What are the male external genitalia?
Glans penis
Shaft of penis
Scrotum
What are the female internal genitalia?
Ovaries
Uterine tubes
Uterus
Vagina
What are the female external genitalia?
Labia majora
Labia minora
Clitoris
How are the testes suspended in the scrotum?
By the spermatic cords
What do the testes produce?
Spermatozoa
Male hormones, primarily testosterone
What covers the surface of each testis?
Internal to External: Tunica albuginea Visceral layer of tunica vaginalis Cavity of tunica vaginalis (contains fluid) Parietal layer of tunica vaginalis
What are the components of the testes?
Seminiferous tubule Straight tubule Rete testis Head, body, tail of epididymis Ductus deferens
Where are sertoli cells found and what is their function?
Seminiferous tubules of testes
Spermatozoa development
Where are Leydig (Interstitial) cells found & what is their function?
Cells in the interstitial tissue, adjacent to seminiferous tubules of testes
Secrete testosterone
What is spermatogenesis?
The process in which spermatozoa are produced from male primordial germ cells by way of mitosis and meiosis
A1 spermatogonia arise from stem cells. What do they further differentiate into?
More type A (stem) cells
Type B cells, committed to differentiation to spermatozoa
How many primary spermatocytes are usually produced?
64
All linked together by cytoplasm bridges
How many spermatids are produced in total?
up to 256
What process do spermatids undergo to form sperm?
Spermiogenesis
How long does spermatogenesis usually take?
70 days
New A1 spermatogonia arise every 16 days so 4 spermatogenic processes occur simultaneously
Where do spermatozoa finally mature?
During progress through the epididymis
Briefly describe what happens during emission
Contractions of vas deferens
Sweep & mix sperm with other components of semen from seminal vesicles & prostate
Dependent on SNS
What is the spermatogenic cycle?
Development of A1 spermatogonia through to 256 sperms
The amount of time it takes for reappearance of the same stage of the cycle within a given segment of the tube
What is the spermatogenic wave?
Different parts of tube begin spermatogenic cycle at different times in a ‘wave’
Production of sperm constant
The distance in the tube between parts that are in the same stage of the spermatogenic wave
What is the rete testis?
Network of canals in mediastinum of testis that seminiferous tubules drain into
What is the epididymis?
Convoluted duct
Sperms stored & continue to mature
What is the vas deferens?
Continuation of epididymis
Thick muscular walls, minute lumen
Walls contract during copulation, force sperm along tube to mix with semen
What is the function of the seminal vesicles?
Secrete thick, alkaline fluid rich in:
- fructose (energy source for sperm)
- coagulating agent
Makes up 60% volume of semen
What is the function of the prostate?
Prostatic fluid 20% of semen
Role in activating sperms
What is the significance of the bulbourethral glands?
Lie posterolateral in intermediate part of urethra
Ducts of the glands open into proximal part of spongy urethra in bulb of penis
Mucus-like secretion enters urethra during sexual arousal
How big are the ovaries?
Almond shaped & sized
What is the function of the ovaries?
Oocyte development
Endocrine glands, produce reproductive hormones
What is the location of the ovaries?
Each ovary suspended by a short peritoneal fold - the mesovarium
Within the mesovarium, a short ovarian ligament tethers the ovary to the uterus
What is the ovarian ligament a remnant of?
Superior part of the ovarian gubernaculum
What surrounds the ovaries?
Tunica albuginea
covered with a smooth layer of ovarian mesothelium
Why does the ovarian mesothelium become progressively scarred & distorted?
Repeated rupture of follicles
How do oogonia arise?
Primordial germ cells colonise the cortex of the primordial gonad
How many oogonia begin meiosis before birth to become primary oocytes?
2 million
What stimulates the entry of oogonia into meiosis 1?
Mesonephric cells/Follicular cells
surround primary oocytes to become primordial follicles
When and why is meiosis arrested during the ovarian cycle?
Diplotene stage of prophase
due to Oocyte Maturation Inhibitor secreted from follicular cells
Between what ages do follicles further develop?
Puberty to menopause
13 to 53?!
Which 3 stages must a follicle go through to form a mature gamete?
- Pre-antral or primordial follicle
- Antral, or secondary follicle
- Pre-ovulatory follicle
How is the corpus luteum formed?
Remains of follicle reorganised
CL secretes progesterone & oestrogen under influence of LH
CL lives for 14 days before regressing spontaneously if ovum not fertilised
Give a brief description of the pre-antral or primordial follicle phase of development
Primary oocyte grows dramatically
Granulosa cells secrete glycoprotein, form zona pellucida around oocyte
Surrounding stroma (c.t) form theca folliculi
Theca & granulosa cells secrete oestrogens
Give a brief description of the antral or secondary follicle phase of development
Granulosa cells proliferate, antrum forms between
Secondary follicle expands to 2mm
Continued development req. FSH & LH
Give a brief description of the pre-ovulatory follicle phase of development
37 hours before ovulation
Oestrogen causes LH receptors to appear on granulosa cells
LH surge
Follicle restarts meiosis
After meiosis 2, secondary follicle arrests 3 hours prior to ovulation (completes if fertilised)
Follicle increases
Follicle rupture
What are the 2 layers of the Theca Folliculi?
Theca Interna - vascular & endocrine
Theca Externa - fibrous capsule
During the antral phase what do FSH & LH bind to?
FSH - Granulosa cells only
LH - Thecal cells only
