The Reproductive Systems Flashcards
lecture 15 week 8
What are the functions of some of the male reproductive system
male reproductive system is needed for the production and delivery of sperm into the female reproductive system
seminal vesicles: produce sugar-rich fluid, provides energy for sperm motility
prostate glands: fluid contains enzymes that prevent sperm coagulation
bulbourethal gland: fluid that lubricates urethra for sperm passage
sperm reaches urethra via vas deferens
- semen is alkaline, which counteracts acidity of female reproductive tract
- movement of sperm mediated by muscle contraction
What is spermatogenesis
- sperm is produced in the seminiferous tubules
- SPERM PRECURSOR CELLS undergo mitosis and meiosis, and sperm released into lumen. sperm reaches epididymis where they become motile - can remain for 5 weeks
- sertoli cells nourish and protect developing sperm against immune system and regulate spermatogenesis
- leydig cells secrete testosterone
- myoid cells are contractile cells that aid transport of sperm along seminiferous tubules
Stages of spermatogenesis
- human spermatogenesis lasts 74 days
EMBRYO
primordial germ cell —> (MITOSIS) spermatogonium —> (MITOSIS) primary spermatocyte
ADULT
—> (MEIOSIS) secondary spermatocyte —> (MEIOSIS II) spermatid —> (MATURATION) sperm
What is the structure of sperm
(haploid cells)
- head
- midpiece
- tail (flagellum)
acrosome: contains enzymes that transverse coating of egg
- whipping motion of flagellum powered by mitochondria
- whipping motion comes from sliding of microtubules of AXONEME
What happens in the final stages of spermatogenesis
- spermatids become enlarged, a tail forms, mitochondria accumulates in midpiece
- acrosome develops from golgi body
- chromatin in condensed as histones replaced by protamines which causes a stronger binding so a tighter structure
- condensed by 5%
What is the role of the female reproductive system
- production of eggs and support of the developing embryo
- female gametes produced in ovaries and released monthly - oocyte travels through oviduct where it is fertilised to the uterus
- endometrium layer of uterus is altered in the menstural cycle
What does the development of the oocytes look like
(asymmetrical development)
EMBRYO
primordial germ cell —> (MITOSIS) oogonium —> (MITOSIS) primary oocyte
(arrests at prophase of meiosis I)
ADULT
secondary oocyte and 1st polar body —> (MEIOSIS II - arrests at metaphase II) zygote and 2nd polar body
final meiotic division occurs after fertilisation
What does the polar body do
gives its cytoplasm for nutrients for the secondary oocyte
What happens before ovulation
both oocyte and surrounding follicular cells undergo maturation
- oocyte loads up cytoplasm with nutrient material
- surrounding cells divide forming layers and secrete glycoprotein that forms zona pellucida
(granulosa cells stay in contact with oocyte and sends important substances)
What are the follicular phases
primordial follicles
- consists of primary oocyte surrounded by single layer of granulosa cells and basement membrane
prenatal (80 days)
- oocyte size increases, synthesis of ribosomal and mRNA, zona pellucida forms, stormal cells form thecal cells and granulosa cells proliferate into several layers
antral (12 days)
- granulosa cells proliferate into more layers, size of oocyte increases, follicular fluid appears forming follicular antrum, theca forms two layers
preovulatory (2 days)
- starts at LH surge, meiosis is completed, 1st polar body forms, granulosa cells withdraw, formation of cortical granules, antrum fully surrounds oocyte
What is the structure of the oocyte
- oocytes contains large amounts of cytoplasm providing nutrients for embryo and molecules important for early cell division
- zona pellucida is another layer of extracellular matrix involved in sperm RECOGNITION, cells of corona radiata provide nutrients and also attract sperm
What are the developmental origins of gonadal cells
Sox9 low, Fgf9 off, Rspo1 low, Wnl4 low
male pathway (Sry present)
- sertoli cells
Sox9 high, Fgf9 high, Rspo1 off, Wnl4 off
germ cells –> quiescent prospermatogonia
steroidgenic cells –> leydig cells
female pathway (Sry not present)
- pre-granulosa cells
Sox9 off, Fgf9 off, Rspo1 high, Wnt4 high
germ cells –> meiotic oocytes
steroidgenic cells –> theca cells
How does hormone control occur in both reproductive systems
- triggers gametogenesis
hypothalamus secretes hormones –> effects pituitary gland –> release of hormones on target organ
in males secretion is almost continuously and in females its secreted cyclically
Male hormone secretion
- GNRH
- sertoli cells stimulates sperm production in response to testosterone and FSH
- leydig cells secrete testosterone in response to LH
LH –> leydig –> testosterone
FSH + testosterone = sertoli cells promoting production of sperm
negative feedback mechanism by testosterone and inhibin maintains constant level of hormones
Female hormone secretion
- menstrual cycle
Follicular phase
- FHS and LH acts on preovulatory follicles causing several oocytes to begin to mature
- granulosa cells secrete ESTRADID which thickens uterus lining
rising ESTRATID levels causes rapid increase then sharp decrease of LH and FSH - surge causes ovulation( stimulates release of oocytes from follicle) and LUTEAL PHASE BEGINS
- folicular cells converted to corpus luteum (a temporary endocrine structure secreting progesterone which thickens uterus lining and negative effect on LH and FSH)
no fertilisation: corpus luteum degenerates, estrogen and progesterone levels fall and uterine lining is shed
fertilisation: embryo travels to uterus and implants in lining - corpus luteum secretes progesterone, maintained by hCG, placenta takes over estrogen and progesterone production maintaining uterine lining and stimulates growth of the uterus
- low levels of estrogens inhibit LH and FSH secretion high levels cause stimulation
- high levels of progesterone have inhibitory effect
