Basic Physiology of the Reproductive System Flashcards
What is the male reproductive system responsible for?
Production (by testes) and transport of sperm
Production of androgens to support secondary sexual characteristics
What is the transport channel for sperm?
Ductus/vas deferens
What is the function of semen?
Provides nutrients/transportation fluid
Where does semen come from?
60% seminal glands
30% prostate
5% bulbourethral glands
What structures are the testes made up from?
Lobules containing seminiferous tubules
V. convoluted
Where is the site of spermatogenesis?
Seminiferous tubules
The seminiferous tubules merge to form which structure?
Epididymis
What does a cross section of a ST look like?
Spermatogonium right at basement membrane and divide and move forward until they are mature sperm in the lumen
Why is it important that blood doesn’t come into contact with STs?
Sperm haploid and looks different so don’t want immune cells interpreting as non-self and destroying them
How many sperm would you get from each spermatogonium?
512
How much sperm does the epididymis store?
5ml
What are some functions of Sertoli cells?
Form blood-testis barrier
Isolate haploid secondary spermatocytes, spermatids, spermatozoa from the immune system
Physically move sperm towards the lumen (spermiation)
Provide nutrients for sperm
Remove waste from sperm
Remove excess cytoplasm following cell divisions
Define spermatogenesis
How long does it take?
Where does it occur?
Process of forming mature sperm
75 days
STs
Define spermatocytogenesis
Mitotic divisions of spermatogonia (undifferentiated male germ cells) to produce primary spermatocytes
What occurs after spermatocytogenesis?
Two meiotic divisions
Meiosis I - primary spermatocytes double up DNA and there is separation of homologous chromosomes that go to make secondary spermatocytes
Meiosis II - secondary spermatocytes half again (separation of chromatids) to make spermatids
Define spermiogenesis?
Maturation of spermatids into mature, motile sperm
Occurs in epididymis
How long is the sperm stored in the epididymis until it becomes motile?
15 days
Where is the final maturation of the sperm?
In the female genital tract that allows it to penetrate the egg and have increased motility
What is the blood supply to the testis like?
Arterial blood enters dense network of capillaries coming from testis/epididymis before reaching spermatic cord - this cools it and helps to maintain a constant testicular temperature
At what temperature do sperm optimally develop?
32 degrees
What two things contribute to keeping the testis slightly cooler than the body in order to maintain optimal spermatogenesis?
Testis outside body
Counter-current heat exchange
What factors can affect spermatogenesis?
Testis temperature, should be 2 degrees below body temp, hyperthermia, mumps, measles etc. can raise it
Endocrine: reduces gonadotrophins/androgens, anabolic steroids –> reduced testosterone
Loss of blood-testis barrier: e.g. by physical damage
Immunological reactions - autoimmune disease
Environment - occupation (e.g. car industry, pesticide exposure), radiation (reduces sperm)
Medication - some antidepressants and anti-HTN
What two things are associated with a lower sperm count?
Smoking
Alcohol
Where does LH act on?
Leydig cells to produce testosterone
Where does testosterone act on?
CNS - aggressive behaviour
Ant pituitary
Penis (erective, copulatory, ejaculatory effectiveness)
Striated muscle
Prostate & seminal vescicles
Testis
Systemically deepens voice, leads to male body hair, increased sebaceous gland activity and protein anabolism
What is the structure of the ovaries?
Outer cortex containing follicles
Inner medulla containing BVs
How many primordial follicles are there in the ovaries at birth?
2 million
What kind of cells line the primary, secondary and tertiary follicles?
What do these cells produce?
Granulosa cells
Oestrogen
Where does fertilisation most commonly occur?
Ampulla of fallopian tube one day after ovulation
Define oogenesis
Production of an ovum
Describe the process of oogenesis
Mitotic division of oogonium –> primary oocytes
Girls born with primordial follicles containing primary oocytes and surrounding later of follicular cells
Primordial follicles turn into primary follicles after puberty (follicular cells –> granulosa cells)
A few primary follicles in each menstrual cycle develop into secondary follicles and then tertiary follicles (Graafian follicles)
FSH makes a few Graafian follicles grow and produce more oestrogen
Neg feedback of oestrogen leads to less FSH –> only one follicle becomes dominant
Oestrogen leads to positive feedback eventually –> LH surge which triggers the primary oocyte to complete meiosis I (become secondary oocyte) & released into fallopian tube
From infancy to puberty, which stage of meiosis I are primary oocytes stuck in?
Prophase
After the primary oocyte is released, what does the follicle turn into?
Corpus luteum
What does the CL produce?
Inhibin which prevents pituitary making FSH and oestrogen falls so LH drops
Which cells make progesterone?
Lutenised theca cells of CL
Until when does the CL make progesterone?
Until placenta has developed
If the egg isn’t fertilised what happens to the CL?
Stops making hormones after about 10 days
Becomes fibrotic and white (corpus albicans)
Low oestrogen exerts what kind of feedback?
Negative
High oestrogen exerts what kind of feedback?
Positive –> LH surge at about day 12
What does GnRH do?
Released from hypothalamus acts on anterior pituitary to stimulate release of LH and FSH
What does LH do?
Maintains dominant follicle, induces maturation and ovulation, stimulate CL function
What does FSH do?
Stimulates follicle recruitment and development
What does oestradiol do?
Supports female secondary sexual characteristics and reproductive organs
Negative & positive feedback control
Stimulates proliferation of endometrium
What does progesterone do?
Maintains secretory epithelium
What is the average age of menopause?
51
Where does oestrogen act in the body?
CNS Ant. pituitary Hypothalamus Fat distribution Mammary glands Bone maturation and turn over Uterus, cervix, vagina, fallopian tubes
What does oestrogen do in the fallopian tubes?
Induces proliferation of ciliated cells that brush the egg into the uterus
What is a reliable sign of ovulation?
Day 21 progesterone
What values of FSH/LH/oestradiol/progesterone do you get in menopause?
High FSH and LH
Low oestradiol and progesterone
