Reproductive Systems Flashcards
The main function of the hypothalamus:
Acts as a homeostatic regulator for reproduction, stress, body temperature, hunger, and sleep.
Called a neuroendocrine organ, as it processes both neural and hormonal information
Posterior pituitary function:
releases hormones
Name the two neurosecretory peptide hormones released by the posterior pituitary:
Oxytocin and antidiuretic hormone (ADH or vassopression)
What does oxytocin aid in the female body?
Milk ejection and childbirth
Anterior pituitary function:
Neurosecretory neurons synthesize releasing and inhibiting hormones
Name the two gonadotrophs produced by the anterior pituitary:
- Follicle-stimulating hormone (FSH)
- Luteinising hormone (LH)
In the reproductive system, the hypophyseal portal system is a _____ arrangement, in which blood flows from on capillary bed in the _______ to another capillary bed in the ______ pituitary without growing through the heart in its journey
vascular
hypothalamus
anterior
The two neurosecretory hormones are _____ and _____. They are synthesized in the _________ and transported to the ______ pituitary, where they are stored and released.
Oxytocin
Antidiuretic hormone
hypothalamus
posterior
The gonadotrophs are located in the _____ pituitary
anterior
The two gonadotrophins produced are:
- follicle-stimulating hormone (FSH)
- Luteinising hormone (LH)
The female endocrine gland where gonadotrophins act is the _____ and in men the _____.
Ovaries
testes
FSH: function
Acts on ovaries and testes to stimulate the production of gametes
LH: function
- Acts on ovaries to trigger ovulation and promote the synthesis and release of ovarian hormones
- Acts on testes to promote the synthesis of testosterone
What determines whether the bipotential gonad develops into an ovary of testis?
the SRY gene
Men: what do Sertoli cells do?
Secrete anti-mullerian hormone leads to Mullerian duct regression
Men: what do Leydig cells do?
Produce testosterone -> wolffian duct development -> internal male genetals
The criteria for staging the development of secondary sexual characteristics is known as what?
Tanner stages
Puberty sequence: girls
- Breast budding
- Pubic hair development
- achievement of peak height growth spurt
- menarche
- ovulation
Puberty sequence: boys
- testes enlarge
- penile enlargement
- pubic hair development
In boys, during puberty, the first sign of secondary sexual development is ____ enlargement. ____ cells enlarge and secrete _______, giving rise to testicular size.
Elongation and enlargement of the ____ begins within a year of ______ ________.
testes
Leydig
testosterone
penis
In girls, first ovulation does not take place until 6-9 months after ______. This delay is because the positive feedback mechanisms involving the hormone _____ have not developed.
menarche
estrogen
At puberty in response to ________ hormone (___) produced by the hypothalamus, the two gonadotropin hormones ___ and __ are secreted from the ______ pituitary gland.
Gonadotropin-stimulating
GnRH
FSH and LH
anterior
These hormones travel via the blood to the testes where LH binds to receptors on the ____ cells inducing the production of _______.
Leydig
testosterone
By approximately one year after menopause, the ovary has essentially ceased producing hormones (ovarian senescence)
Estrogen production reduces to approximately __% of previous levels.
The estrogen which is now produced is _____, which is a weak estrogen that arises mainly from the _____ cells of _____ tissue.
10
stromal
adipose
Vagina: three main functions
- Passageway for the elimination of menstrual fluids
- receives penis for intercourse, holds spermatozoa before they pass into the uterus
- forms lower portion of the birth canal
Where does fertilization occur?
Ampulla of the uterine tube
Uterine (fallopian) tubes: function
- Fertilisation -> provides a rich nutritive environment containing lips and glycogen for spermatozoa, oocytes, and the developing embryo
The ______ lining of the uterine tube has both ciliated and non-ciliated ______ ______ cells.
epithelium
secretory columnar
In the uterine tube: the mucosa is surrounded by _____ layers of _____ _____.
concentric
smooth muscle
Just above the ovary extending from the tube are ____, finger-like structures, this area is called the _____
fimbriae
infundibulum
The ovary is covered in ____. Following ovulation, the oocyte is drawn into the uterine tubes by the ____ then down to the uterus.
fimbriae
fimbriae
Ovary: has three distinct regions
- Outer ovarian cortex (containing the ovarian follicles
- Central ovarian medulla (consisting of ovarian stroma and steroid producing cells)
- Inner hilus (entry point for nerves and vessels)
Ectopic pregnancy
- When the fertilized embryo is implanted in any other tissue than the uterus wall
- most occur in the uterine tube (tubal pregnancy)
About __% of women have a _____ uterus (instead of the regular ____ uterus), which could cause some pain during menstruation or intercourse
20
retroflexed
anteflexed
Histology of the ovary:
- Primordial follicle
- primary follicle
- secondary follicle
- mature (Graafian or pre-ovulatory) follicle
- ovulation
- corpus luteum
- fertilization
Primordial follicle:
- the oocyte is surrounded by a single layer of flat follicular cells (which develop into granulosa cells), form the primordial follicle
Primary follicle:
- as the follicles grow, they are called primary or pre-antral follicles
- immature primary follicles consist of only one layer of granulosa cells
- In response to FSH, some follicles get larger producing many layers of granulosa cells surrounding the oocyte
Primary follicle: more detail
The oocyte secretes _____, which form a translucent cellular layer (___ ______)
Condensation of ovarian ____ cells, known as ___ cells, start to form around the follicle
glycoproteins
zona pellucida
stromal
thecal
Secondary follicle:
- as granulosa cells proliferate they produce a viscous follicular fluid that coalesces to form a single follicular antrum
- these are called secondary or antrum follicles
- the theca develops to become inner glandular, highly vascular theca internal, and the surrounding fibrous capsule, the theca externa
Mature follicle:
- As follicular antrum grows, the oocyte becomes suspended in fluid
= it is connected to the rim of peripheral granulosa cells by a thin stalk of cells
Ovulation:
- increasing size plus position in the cortex of ovarian stroma = bulge out from ovarian surface then follicle ruptures, carrying with it the oocyte and surrounding mass of cumulus cells
- oocyte collected by the cilia on the fimbria -> taken into the fallopian tube
Corpus luteum:
- Antrum breaks down
BM between granulosa and thecal layers breaks down and blood vessels invade - yellow pigment cells form
- transformation called luteinization -> associated with increased secretion of progestagens
- whitish scar tissue remains, the corpus Albicans (white body) is absorbed back into the stromal tissue
Fertilization:
- if oocyte is fertilized and begins to divide -? corpus luteum persists past its normal 2-week lifespan
- it is reduced from degeneration by human chorionic gonadotropin (hCG)
- this hormone is produced by the chorion of the embryo beginning about 9 days after fertilization
When does mitogenesis start in men?
around puberty
Men produce around ___ sperm per second
20,000
What is contained in the structural part of the sperm cell?
Mitochondria
- provides energy (ATP) for sperm to move
Three phases of spermatogenesis:
- mitotic division
- meiotic division
- cytodifferentiation
Spermatogenesis: These mitotic divisions occur in the ____ compartment of the ______ ______
basal
seminiferous tubules
Spermatogenesis: when mitotic division is complete, the spermatogonia move between adjacent ____ cells to the ______ compartment of the _____ tubules.
Sertoli
adluminal
seminiferous
Spermatogenesis: in the _____ compartment they are renamed ____ spermocytes, then undergo ____
adluminal
primary
meiosis
Spermiogenesis:
where round spermatids differentiate their shapes -> undergo elongation to become sperm
Hormonal control of spermatogenesis:
The _____ releases gonadotrophin-releasing hormone (GnRH) that travels via the _____ _____ system to the _____ pituitary and stimulates the release of two gonadotrophins ___ and __.
hypothalamus
hypophyseal portal
anterior
FSH and LH
LH is a protein hormone, travels from the _____ pituitary to the ____ where LH binds to receptors on the outside of ___ cells (which sit in the _____ ____ between the ____ tubules)
The response of the ____ cells is to produce _____ (an androgen)
anterior testes Leydig interstitial space seminiferous
Leydig Testosterone (important for secondary sexual characteristics)
Receptors on the surface of ____ cells receive stimulus that then initiates the release of the lipid-soluble male androgen ______.
Leydig
testosterone
High levels of testosterone are maintained by its binding to and androgen binding protein (I) produced by the _____ cells.
Sertoli
Independently these cells produce another hormone that helps regulate the process through feedback - this hormone is called _____.
Inhibin
Testosterone is also converted to a very potent androgen called __ _______, responsible for the development of secondary sexual characteristics.
5a dihydrotestosterone
Three major components of ejaculated semen
- seminal fluid
- sperm
- prostatic secretion
Seminal fluid
- Approximately 60% of ejaculate volume
- alkaline
- contains fructose
- contains clotting proteins
Sperm
- approximately 10% of ejaculate volume
- contains genetic information
Prostatic secretions
- approximately 30% of ejaculate volume
- acidic
- contains PSA
PSA (prostate-specific antigen)
A protein produces by cells in the prostate gland, which makes the fluid that carries sperm
Oligospermia
less sperm than the usual amount
azoospermia
no sperm at all
Infertility treatment: IVF
- requires approximately 50,000 sperm
- requires motile sperm
- sperm fertilize the oocyte in a petri dish
- oocytes are harvested and fertilized ex vivo
Infertility treatment: intracytoplasmic sperm injection (ICSI)
- requires only a single sperm, which is injected directly into the oocyte
- sperm does not need to be motile
- can use sperm collected by biopsy from testes
The penis has three major structures
- Corpora cavernosa
- The corpus spongiosum
- Penile urethra
Corpora cavernosa
The main erectile tissue
The corpus spongiosum
Surrounds the penile urethra and prevents occlusion during erection
Penile urethra
conducts semen and urine
An erection is initiated and maintained by the ______ branch of the autonomic nervous system
parasympathetic
In order to establish an erection, human males rely solely on the ______ pressure in the penis.
These chambers are called the _____ ____
hydrodynamic
Corpora cavernosa
Relaxation of the smooth muscle is dependent upon the intracellular messenger ____, which reduces the intracellular _____.
cGMP
calcium
The enzyme _________ ___ _ is responsible for the breakdown of this second messenger and is the target of viagra.
phosphodiesterase type 5
The _____ ____ is a circular erectile structure that surrounds and prevents the occlusion of the penile urethra during an erection
corpus spongiosum
Once erect, the penis contains approximately _ times more blood than a flaccid penis.
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Viagra: relaxation of the smooth muscle in the corpora cavernosa requires _______, a 2nd messenger which reduces calcium
Guanosine monophosphate (cGMP)
The enzyme ______ breaks down cGMP, Viagra inhibits this enzyme -> increasing GMP -> replacing the arteries supplying the ______ ______ and erection.
phophodiesterase
corpora cavernosa
The prostate secretes:
- Phosphate and calcium
- phosphate specific antigen (PSA) and other enzymes (breaks down post ejaculation coagulum)
- slightly acidic (pH 6.5)
- contains citrate (for AMP)
- a milky colour
The pH of semen is approximately __ with prostatic and seminal fluid neutralizing each other.
7.5
Benign prostatic hyperplasia
- Excess growth of the prostate - occludes the urethra
- causes difficulty voiding bladder
- eventual bladder weakness
- urinary tract infections
- frequent urination
- kidney problems
- sensation of incomplete emptying
Treatments of benign prostatic hyperplasia
Selective 5a-reductase inhibitors (stop prostate from enlarging or shrink it)
- finasteride
- dutasteride
Surgery
other
Finasteride and dutasteride ____ the enzyme 5a-reductase, prevents production of __________, prostate grows less in response to ______ then it does _________, so it slows it down or reverses growth.
inhibit
dihydrotestosterone
dihydrotestosterone
testosterone
Treatments for prostate cancer
- watchful waiting
- androgen depletion
- inhibitors
- castration
- inhibitors of androgen synthesis
- inhibition of testosterone action, block the androgen receptor
- surgery: prostatectomy
Water-soluble reproductive hormones
peptides and proteins. Oxytocin, FSH, LH, GnRH
Oestrogens
- Oestradiol (by developing follicles)
- Oestrone (adipose tissue)
- Oestriol (in placenta just before labor)
100 x more in females than males
The main production site is the granulose cells of the developing follicle.
Mullerian tubes become
uterine tube, uterus, cervix, upper vagina
Male external genital development
- Fusion of the urethral folds to enclose the urethral tube, forming a shaft
- labioscrotal swellings fuse to form the midline of the scrotum
- glans area expands forming the glans penis
Female external sex development
urethral folds and labioscrotal swellings remain separate - forming labia minora and Majora.
Glans area forms the clitoris
Timing of puberty in girls
critical weight must be achieved to activate the hypothalamic-pituitary-gonadal axis. 47kg - signifies that sufficient storage is available to sustain pregnancy and lactation
Precocious puberty
signs of puberty before 7 years in girls and 9 in boys. usually due to a GnRH problem
Delayed puberty
lack of gonadotrophin signals from the pituitary. no signs at 13 years in girls and 14 in boys
Premenopause
40 ish onwards - regular periods
menopausal transition
46ish onwards - irregular periods
post menopause
- ovaries stop producing hormones
- 1/10 of normal oestrogen levels (primarily oestrone) from the stromal cells in adipose tissue (weaker)
Ovarian senescence
Cease of ovarian function (54ish)
Perimenopause
from the start of irregular transition till ovarian sensc
ence
Perimenopause symptoms
- Vasomotor - Hot flushes, night sweats
- genitourinary - vaginal dryness
- bone metabolism - osteoporosis
- behavioral changes - depression, tension, anxiety, mental confusion, libido
Treatment for perimenopausal symptoms
oestrogen replacement therapy
LH in spermatogenesis
binds to Leydig cells outside the seminiferous tubules, stimulating the secretion of testosterone. this feeds back to the gonadotrophs and the hypothalamus to inhibit the production of GnRH, LH, FSH
FSH in spermatogenesis
works on the Sertoli cells to stimulate the production of ABP which binds to steroid hormones and makes them water-soluble - hence preventing them from crossing the lipid bilayer. when testosterone levels are high enough Sertoli cells produce inhibin which inhibits the release of FSH from the gonadotrophs in the anterior pituitary.
vans deferens
45cm long. runs from the epididymis and ends in the ampulla.
urethra
20cm long. from the bladder through the prostate to the end of the penis
seminal vesicle
secrete mucoid, fructose (an energy source for sperm), prostaglandin (smooth muscle contraction of the female reproductive tract), clotting protein (forms coagulum helps the semen to stick to the female tract). comes in last in the ejaculate
erection occurs
release of NO and prostaglandin E1 causes the relaxation of the smooth muscle of cc. blood fills it - 8x more blood in erect penis.. venous outflow reduced too. cs keep the penile urethra open too
Sexual stimulation causes an increase in NO and Prostaglandin E1 levels causing the smooth muscle in the corpora cavernosa and corpus spongiosum to relax allowing dilation of the arteries. Dilation of the arteries allows increased blood flow to the penis which in turn prevents venous return by occluding venous outflow. There is no voluntary control of this process and the penis expands to 8x its flaccid size
brief description of the menstrual cycle.
after the death of the corpus luteum reduced positive feedback leads to slightly increased LH and FSH levels.
stimulates follicular development. stimulates the production of oestradiol - inhibiting the release of FSH and LH.
around day 12 if oestradiol levels are sustained negative feedback switches to positive feedback. leads to LH surge - leads to ovulation. day 14 corpus luteum formed secretes progestagens and estrogens which represses LH and FSH. corpus luteum dies off and progestagen and oestrogen levels reduce.
phases and time frames for uterine cycle
proliferative - day 5ish to day 14. secretory - day 14 to day 28. menstruation - 28 - 5
phases of the ovarian cycle
follicular phase and luteal phase - luteal phase always 14 days. other phase variables so the length of the menstrual cycle varies between women.
Sperm structure: acrosome
structure in a sperm cell which covers the nucleus with enzymes (proteases and hyaluronidase) that digest the oocyte wall allowing fertilization
Sperm structure: Head
Region of the sperm cell above neck containing the nucleus and acrosome
Sperm structure: Tail
Region of the sperm cell from neck and below containing the neck, middle piece, principal piece, and end piece
Sperm structure: Neck
Area in sperm cell between the nucleus and middle piece
Sperm structure: middle piece
Structure in sperm below the neck and above the principal piece which contains many mitochondria which can generate sufficient energy to propel the sperm
Sperm structure: principal piece
The large section of the tail which produce most of the movement of the sperm contains microtubules that allow it to link with the mitochondria
end piece
the thinner part at the very end of the tail
Inhibin
the hormone produced by Sertoli cells in the presence of testosterone which reduces the secretion of FSH by the anterior pituitary
Androgen Binding Protein
The hormone produced by Sertoli cells in the presence of testosterone released by the Leydig cells increases the binding affinity of testosterone keeping levels high in the seminiferous tubule
Kisspeptin
Neurotransmitter and hormone in the brain which controls the release of GnRH
Hormonal control of testicular functions
GnRH is released by the hypothalamus which acts on gonadotrophs in the anterior pituitary to increase the release of FSH and LH. LH acts on Leydig cells, stimulating the release of testosterone which acts on Sertoli cells and can also be converted into 5-alpha dihydrotestosterone. FSH acts synergistically with LH to stimulate the secretion of ABP. Increased FSH levels provide negative feedback in reducing the secretion of FSH from the pituitary while LH provides negative feedback by reducing the secretion of FSH and LH from the pituitary and GnRH from the hypothalamus
Basal compartment
The area towards the interstitium in seminiferous tubules where mitosis occurs 2-3 times
Cryptorchidism
A condition where the testes do not descend to the scrotum from the pelvis. Often associated with infertility
Ductus (vas) deferens
The large duct (45cm) is made of pseudo-stratified epithelium which begins at the end of the epididymis which stores sperm for up to several months. It also has numerous layers of smooth muscle which contract parasitically to move sperm along.
Seminal vesicle
The accessory sexual gland is located anterior to the ampulla of the vas deferens and secretes into the ejaculatory duct.
Secretes a mucoid substance which alkaline and contains fructose to allow sperm to produce energy for movement, prostaglandins for movement and vitality of sperm, and clotting proteins to coagulate the sperm in the vagina
PSA
An enzyme that decoagulates sperm to allow it to move through the vagina and into the uterus and so on
Inguinal canal
The canal which the testes descend through and convey the spermatic cord
Bulbourethral gland
Small accessory sex gland located next to the deep perineum muscles. Makes a small contribution to the makeup of semen and lubricates the urethra
Glans penis
Extension of the corpus spongiosum at the tip of the penis
Crus of penis
The area where the corpora cavernosa connects to the perineal membrane
Bulb of penis
Connection of the corpus spongiosum to the perineal membrane
Prostaglandin E1
The hormone which causes relaxation of smooth muscle in the penis
