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Year 1 - BRS > 4.10 - The Reproductive System > Flashcards

4.10 - The Reproductive System Flashcards

1
Q

What do the testes do?

A
  • male gonad
  • produce sperm - spermatogenesis (produce mature spermatozoa)
  • suspended in scrotum to keep temperature 2-3 degrees lower than rest of the body - any higher and sperm production ceases
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2
Q

Describe the anatomy of the testes.

A
  • a capsule surrounded by three connective tissue layers (inside –> outside):
  • tunica vasculosa - contains blood vessels
  • tunica albuginea - thick layer forming the septa that divides testis into lobules
  • tunica vaginalis - covers testis and epididymis
  • approximately 300 lobules each with 1-4 seminiferous tubules which have closed loops and drain into rete testis then epididymis for storage, then vas deferens
  • vas deferens is surrounded by smooth muscle and is what is cut in vasectomy with minimal incision - also palpable
  • arterial blood supply - testicular arteries from the aorta via the spermatic cord
  • lymphatic drainage - para-aortic lymph nodes
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3
Q

What does the epididymis do?

A
  • a single tightly-coiled tube that stores and matures sperm - if not ejaculated, then broken down
  • is palpable
  • nutrients (e.g. fructose) and glycoprotein secretion into epididymal fluid (induced by androgens)
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4
Q

What happens in the efferent ducts?

A
  • tubular reabsorption resulting in concentration
  • induced by oestrogen, which is formed from testosterone
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5
Q

What does the vas/ductus deferens do?

A

Transports sperm from testicles to penis

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6
Q

What do the prostate and seminal vesicles do?

A

Secrete seminal fluid to support ejaculated sperm

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7
Q

What is seminal fluid made of?

A
  • fructose
  • citric acid (nutrient)
  • bicarbonate (to neutralise vaginal acidity)
  • fibrinogen (thickener)
  • fibrinolytic enzymes
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8
Q

What does the penis do?

A

Deposits sperm in vagina

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9
Q

What three muscles make up the penis?

A
  • 2 x corpora cavernosa
  • 1 x corpora spongiosum
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10
Q

What type of nervous stimulation leads to erection and ejaculation?

A
  • Parasympathetic for erection due to arterial relaxation leading to increasing pressure obstructing venous drainage
  • Sympathetic for ejaculation
  • Point and Shoot
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11
Q

What do the bulbo-urethral glands do?

A

Secrete sugar-rich mucus into urethra for lubrication and contribute to pre-ejaculatory emission from penis

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12
Q

What is the spermatic cord?

A
  • suspends the testes, formed at deep inguinal ring and passes along inguinal canal down to scrotum

Contains:

  • vas deferens
  • testicular artery
  • pampiniform plexus of veins
  • autonomic and GF nerves
  • lymph vessels
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13
Q

Which part of the female reproductive tract is situated in and which is out of the peritoneal cavity?

A

Ovaries are inside peritoneal cavity, remainder is outside

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14
Q

What do the fallopian tubes do?

A
  • lined by cilia and have spiral muscle = through peristalsis and wafting of cilia, the oocyte gets moved down the tube
  • if this motility is slow then susceptible to ectopic pregnancies
  • fertilisation usually occurs in ampulla - widest section
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15
Q

What supports the uterus to stop it prolapsing out of the vagina?

A

Supported by tone of pelvic floor (levator ani and coccygeus muscles) and ligaments (broad, round, uterosacral)

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16
Q

What are the layers of the uterus?

A
  • serosa (peritoneal covering) - perimetrium
  • myometrium (thick smooth muscle layer sensitive to hormones)
  • endometrium (specialised epithelium)
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17
Q

What happens to endometrium at the end of the menstrual cycle?

A
  • endometrium shed at menses
  • progesterone levels fall –> intermittent vasoconstriction of arterioles in endometrium –> ischaemia/necrosis causing shedding and haemorrhage of menstruation
18
Q

Where is the ureter around the cervix and why is it important?

A
  • ureter is 1cm lateral to cervix on either side
  • important when considering cervical cancer
19
Q

How is sterility maintained?

A
  • all areas superior to cervix are sterile
  • shedding of endometrium
  • thick cervical mucus
  • narrow external os (hole in middle of cervix)
  • acidity - oestrogen stimulates vaginal epithelium to secrete glycogen which the bacteria digest producing lactic acid which lowers pH to kill other pathogens
  • antibiotics can disrupt this causing overgrowth and infections like candiasis
20
Q

What kind of mucus does oestrogen vs progesterone promote?

A
  • oestrogen promotes thin watery mucus allowing sperm to pass
  • progesterone promotes thick viscous mucus - one of the methods of the progesterone only pill
21
Q

What is the arterial blood supply of ovaries and uterus?

A
  • ovaries - ovarian arteries from aorta
  • uterus/vagina - uterine arteries
22
Q

What is the lymphatic drainage of ovaries and uterus?

A
  • ovaries = para-aortic lymph nodes
  • uterus/vagina = iliac, sacral, aortic and inguinal lymph nodes
23
Q

What are male germ cell levels like across lifespan?

A
  • gametogenesis begins at puberty
  • spermatogonia undergo differentiation and self-renewal to maintain pool for subsequent spermatogenic cycles through life (continuous fertility)
  • produce 1500 mature sperm/second
24
Q

What are female germ cell levels like across lifespan?

A
  • before birth, multiplication of oogonia to 6mil/ovary
  • form primary oocytes within ovarian follicles (= primordial follicle) which begin meiosis (halted in prophase)
  • some primordial follicles degenerate (atresia) leaving 2mil/ovary at birth
  • due to further atresia, by puberty <0.5mil/ovary remain
25
Q

What are the steps to spermatogenesis?

A
  • happens in intratubular compartment of seminiferous tubules
  • 2n germ cell - spermatogonium (44XY) - diploid
  • mitosis
  • primary spermatocytes (44XY)
  • 1st meiotic division
  • secondary spermatocytes (22X or 22Y) - haploid
  • 2nd meiotic division
  • spermatids (22X or 22Y)
  • differentiation
  • spermatozoa (22X or 22Y)
26
Q

What are seminiferous tubules made of?

A
  • tunica propria - several layers of flattened cells forming a basement membrane next to which spermatogonia lie
  • Leydig cells (between tubules)
  • Sertoli cells (within tubules)
  • spermatogonium
  • primary spermatocyte
  • spermatid
27
Q

How does spermatogenesis happen across the tubule?

A
  • spermatogonia next to tunica propria mature and move inwards forming primary and secondary spermatocytes (latter is rarely seen) and ultimately spermatids that are released into duct
  • continuous fertility is achieved as spermatogenesis at different stages in different parts of tubule
28
Q

What do Sertoli cells do?

A
  • have FSH receptors and are within seminiferous tubules
  • support developing germ cells by assisting their movement into tubular lumen, transfer nutrient from capillaries to them, phagocytosis of damaged germ cells
  • make inhibin and activin (has negative/positive feedback on FSH secretion from pituitary)
  • make anti-Mullerian hormone (AMH) to aid regression of Mullerian ducts in male sex development which otherwise would form fallopian tubes/uterus/cervix –> FSH promotes AMH transcription in absence of androgen signalling, testosterone inhibits
  • make androgen-binding protein (ABP)
29
Q

What do Leydig cells do?

A
  • have LH receptors between seminiferous tubules
  • pale cytoplasm as cholesterol-rich
  • on LH stimulation, secrete androgens like testosterone, dehydroepiandrosterone (DHEA) and androstenedione (all aromatised to oestrogens)
30
Q

What are the steps to oogenesis?

A
  • polar bodies - small haploid cells as oocyte cytoplasm does not divide evenly, undergoes apoptosis
  • 2n germ cell –> oogonium (44XX) - diploid
  • mitosis
  • primary oocytes (44XX)
  • 1st meiotic division
  • secondary oocytes (22X) + 1st polar bodies - haploid
  • 2nd meiotic division
  • ootids (22X) + 2nd polar bodies
  • differentiation
  • ova (22X)
31
Q

What happens to oogonia in 2nd trimester of pregnancy?

A

All oogonia in foetus develop into primary oocytes (forming primordial follicles)

32
Q

What is menarche?

A
  • the first menstrual cycle (between 10-16 years old)
  • menarche –> first meiotic division
  • sperm fusion –> second meiotic division
33
Q

What are the steps to folliculogenesis (follicle development)?

A
  1. primordial follicle (primary oocyte at birth)
  2. primary (aka preantral) follicle - primary oocyte and layers of granulosa cells and outer theca cells
  3. secondary (aka antral) follicle - fluid-filled cavity (antrum) develops and has FSH+LH receptors
  4. mature (aka Graafian/preovulatory) follicle - forms due to LH surge and secondary oocyte formed
  5. ruptures surface of ovary –> liberated ovum
  6. corpus luteum - produces progesterone and oestrogen (stimulated by LH/hCG) and in pregnancy, production of these is taken over by placenta
34
Q

What do theca cells do?

A
  • associated with outer part of ovarian follicles
  • bind LH to produce androgens
  • support folliculogenesis - structural and nutritional support of growing follicle
  • overactivity of theca cells is one of commonest causes of infertility due to hyperandrogenism
35
Q

What do the granulosa cells do?

A
  • associated with inner part of ovarian follicles
  • bind FSH to aromatise androgens from theca cells to oestrogens (by aromatase)
  • secrete inhibin and activin (negative/positive feedback of FSH secretion from pituitary)
  • after ovulation they turn into granulosa lutei cells that produce progesterone (negative feedback on hypothalamus and anterior pituitary, and promotes pregnancy by maintaining endometrium) and relaxin (prepares endometrium for pregnancy and softens pelvic ligaments/cervix)
36
Q

How does the dominant follicle form?

A
  • lots of follicles initially develop but dominant follicle takes over
  • as it produces most oestrogen (this shuts down FSH stimulation of other follicles)
37
Q

What is human steroidogenesis?

A
  • granulosa can make progesterone but stops there, then gets androgens from theca cells to convert to oestrogens
  • in men, steroidogenesis occurs in Leydig cells
  • cholesterol is the basis
38
Q

Describe the hypothalamic-pituitary-gonadal (HPG) axis?

A

Kisspeptin –> GnRH (gonadotropin releasing hormone, hypothalamus) –> LH/FSH (pituitary, gonadotroph –> release) –> gonads (targets - testes/ovaries) –> oestrogen/testosterone/progesterone/androgen (target hormones)

39
Q

What effect does hyperprolactinaemia have on the HPG axis?

A
  • prolactin binds to prolactin receptors on kisspeptin neurones in hypothalamus
  • inhibits kisspeptin release
  • decreases in downstream GnRH, LH, FSH, testosterone, oestrogen
  • leads to oligomenorrhoea (> 35 days menses) or amenorrhoea (3-6 month no menses) / low libido / infertility / osteoporosis
40
Q

What kind of release does GnRH and FSH/LH have?

A

Pulsatile

41
Q

What kind of rhythm do sex steroids (especially testosterone) have?

A

Diurnal rhythm

Year 1 - BRS (73 decks)

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