W24 The Reproductive System Flashcards
What are features of the reproductive system?
- Produces male and female gametes
- Oocyte
- sperm
- Enhances fertilisation of an oocyte by
a sperm - Female: nurtures new individual until
birth - Produces reproductive hormones –
controls above processes - Birth: Biological Sex
- Female (vagina)
- Male (penis)
- Intersex (variation)
- Anatomy doesn’t always dictate
gender identity - Covering biological sex
What makes up the male reproductive system?
Organs?
Ducts?
Glands?
Organs
- Testes
- Penis
Ducts
- Epididymis
- Ductus deferens
- Urethra
Glands
- Seminal vesicles
- Prostate
Describe features of the testes:
What produces testosterone?
What produces sperm?
- Testes covered in
- Fibrous connective tissue
- (under skin- scrotum)
Each testis contains
* Connective tissue forms lobes
* Seminiferous tubules (produce sperm)
* Rete testis
* Efferent ductules
* Epididymis
* Ductus deferens
* Leydig cells (outside seminiferous tubule)
- Produce testosterone
What is Gametogenesis?
(2)
Formation of the male and female gametes
- Gametes (ovum and spermatozoa)
-Oogonium/primary oocytes and spermatogonium
Splits into: - Females: oogenesis
- Males: spermatogenesis
-occurs in the gonads (ovary or testis)
Gametogenesis undergoes Meiosis.
Describe the process.
- One cell undergoes two consecutive cell divisions
- Four daughter cells, each half as
many chromosomes as the parent cell
Termed - meiosis I (reduction division, 23)
- meiosis II
- During fertilization, zygote receives 1 set of chromosomes (23) from each parent
What is the Seminiferous tubule?
What do Leydig and Sertoli cells produce?
- Where sperm formed
-Mature in lumen, immature on outside - Leydig cells (testosterone)
- Sertoli cells (nourish the germ cells and produce hormones)
-Germ cells partially embedded
What is Spermatogenesis?
- Creation of sperm cells within the male gonads (testes)
Spermatogonia- Spermatocytes- Spermatids- Spermatozoa
What is the Seminiferous tubule?
- Where sperm formed
-Mature in lumen, immature on outside - Leydig cells (testosterone)
- Sertoli cells (nourish the germ cells and produce hormones)
-Germ cells partially embedded
What are the functions of the testes?
How long does sperm take to mature?
- Exocrine – produce sperm
- Endocrine – produce hormone
Spermatogenesis - Process of sperm maturation
- Involves both mitosis & meiosis
- Takes ~ 74 days to complete (incl
maturation)
What makes up the female reproductive system?
Ovary
Uterine tube/ fallopian tube oviduct
Uterus
Vagina
What are the 3 Uterine tissue layers?
- Endometrium – vascular and glandular * Stratum compactum - cuboidal ciliated
epithelium* - Stratum spongiosum - loose connective
tissue** Stratum basale
*Slough during menstruation - Myometrium – 3 layers of smooth muscle
- Perimetrium - peritoneum
What are the major components of the fallopian tubes? (3)
- Also known as: Uterine tubes or Oviducts
- Each 10cm long (approx.)
- Isthmus – narrowing
- Ampulla – swelling – fertilization usually occurs here
- Infundibulum – collecting area with fimbrae
-Fimbrae that collect egg when released from ovary
What is the ovary?
- Outer: connective tissue – ovarian follicles
- Oocyte (female sex cell)
- Centre: blood vessels nervous
tissue - Developing follicles (cellular
structures) - Surrounding developing oocytes
Ovary: follicular development
- Primordial follicles (present at birth)
- Puberty:
Primary follicles - Oocyte enlarges
- Develops granulosa cells
- Build up
Secondary follicle - Fluid filled vesicles
- Thecal cells
Grafian follicle (mature follicle) - Inside are Ruptures and secondary oocytes surrounded by cells released during ovulation
What are follicles?
Small sacs filled with fluid
- Primary follicle surrounded by
granulosa cells - No. Layers of granulosa cells increase as maturation proceeds
- Cells secrete oestrogen-rich fluid into space surrounding oocyte called Antrum
- Outer layer of granulosa cells condenses into layer of theca cells
What is Oogenesis?
- Occurs in the ovaries
- Process of creation of an ovum (egg cell) from precursor cells
- Begins prior to birth
- primordial germ cells (oogonia) in foetal ovary
- spans all of pre-reproductive & reproductive life
- Similar process to spermatogenesis
- Mitosis of primordial cells (oogonia)
- (early) meiosis of primary oocytes
- (late) meiosis of secondary oocyte
Steps of Oogenesis:
Primitive germ cells differentiate into
Oogonia which peform mitosis to become
Primary oocyte, early meiosis leads to
Secondary oocyte, late meiosis leads to
Ovum
Ovary: follicular and oocyte development
- Follicle development 28 days
- Hormonal control
- Generally only one follicles forms a mature follicle
- Remaining degenerate
- Post ovulation
- Forms corpus luteum
- If pregnancy
- Corpus luteum enlarges and persists (producing hormone)
- If no pregnancy
- Corpus luteum lasts 10-12 days then degenerates (becomes small white structure)
Which follicle ruptures at ovulation?
Grafian
Secondary
Primary
Grafian
Recap: the endocrine system
What are the major endocrine glands?
- Adrenal glands
- Hypothalamus
- Ovaries and testes
- Pancreas
- Thyroid and parathyroid
- Pineal gland
- Pituitary gland
- Thymus gland 29
Recap: the endocrine system
What are hormones?
A chemical substance produced by ductless glands within the endocrine system
What are the 3 classes of hormones?
- Three general classes
- Hormones derived from amino acids
- Dopamine, epinephrine (tyrosine precursor)
- Proteins and peptides
- Insulin (peptide), growth hormone (protein)
- Hormones derived from lipids
- Prostaglandins (derived from phospholipids)
- Steroids (derived from cholesterol)
- Most RH steroids but stimulated by other classes
- Reproductive hormones (RHs) are synthesised and secreted throughout a person’s
lifetime at different levels, increasing at puberty and normally decreasing in old age
What are Reproductive hormones?
What are the 3 classes of reproductive hormones?
What do they interact with?
- Commonly called sex steroids or steroid hormones
- Produced mainly by the gonads (ovaries and testes)
- Some production by placenta, adrenal glands
Three classes:
* Oestrogens
* Androgens
* Progestogens
* Interact with oestrogen (ER), androgen (AR) or progesterone (PR)
receptors respectively
Overview of major functions of
reproductive hormones
- Bind to specific receptors in target tissues
- AR, ER, PR
- Exert a range of effects on both organs and the body as a whole
- Primary role: maturation of reproductive organs, fertility and pregnancy
- Secondary role: development of physical characteristics
Where is testosterone produced?
In Leydig cells
Sertoli cells
Reproductive hormones: molecular
action
- Generic mechanism of action
- Hormones enter cells
- Hormones bind to an intracellular receptor
- Conformation change and translocation
- DNA binding (HRE’s)
- Gene expression (or repression)
Endocrine function of gonads is regulated by
HPG axis
Hypothalamus, Pituitary, Gonad
Where is the hypothalamus?
What does it release
Small structure at base of forebrain
It releases GnRH (Gonadotrophin Releasing Hormone) which is a peptide hormone
Stimulated and is released into the blood and reaches the pituitary
What is the Pituitary gland?
- Pea-sized gland located at the base of the
skull ventral to the hypothalamus - Comprised of two elements
- Posterior and anterior lobes
- Anterior pituitary contains specialised cells
(gonadotropes) - GnRH stimulates gonadotropes to
- Produce gonadotrophins
- glycoproteins
- FSH (follicular stimulating hormone)
- LH (Lutenising hormone)
- hCG (human chorionic gonadotrophin)
What are the 2 Gonadotropins?
How do they work?
LH and FSH
Luteinizing and Follicular stimulating hormones
Bind to different receptors expressed on cells within the ovary and testes
LH main functions
- ♀ acts on ovarian follicle INDUCING OVULATION (main)
- ♂ acts on testes producing testosterone
FSH main functions
- ♀ Promotes ovarian follicle development
& oestrogen production (main) - ♂ stimulates spermatogenesis in testes
- Sertoli cells
What are the 3 classes of hormones?
Oestrogens e.g. oestradiol
Androgens e.g. DHEA, DHT
Progestogens e.g. progesterone
HPG axis:
What hormone does the hypothalamus secrete?
What 2 hormones does the pituitary gland release?
1.GnRH
2.LH and FSH
Luteinising and Follicular Stimulating Hormones
Regulation of Reproductive Hormone
Secretion: Male reproductive System (6)
- GnRH stimulates secretion of LH and FSH from anterior pituitary
- LH stimulates testosterone secretion from Leydig Cells (interstitial cells)
- FSH stimulates Sertoli cells to increase spermatogenesis
- Testosterone
- Stimulates Sertoli cells
- Development of reproductive organs
- Testosterone: negative effect on Hypothalamus and Pituitary
- Sertoli cells secrete inhibin – negative feedback
- Puberty- ages 12-14
- Before puberty- small amounts of testosterone secreted by the testes and the adrenal cortex (inhibit GnRH, LH and FSH)
- During puberty there are developmental changes in the hypothalamus
- Cause the hypothalamus and the anterior pituitary gland to become much less sensitive to the inhibitory effect.
- Rate of GnRH
The female reproductive cycle:
What 2 cycles does it consist of?
- Reproductive cycle consists of ovarian and uterine cycles
Ovarian cycle:
-series of ovarian events that precede and follow oocyte maturation - controls oogenesis
- Uterine cycle
-Preparation of uterus to receive ovum - Mediated by reproductive hormones
Stages of the menstrual cycle in order: (4)
Menses, Follicular Phase, Ovulation (proliferative phase), Luteal Phase (secretary phase)
What happens during the ovarian cycle?
- During each ovarian cycle, up to 20 primordial follicles are activated (by FSH) to begin the maturation process
- Usually only one reaches full maturity, the remainder regress
- The ovarian cycle can be divided into 3 phases:
- Follicular phase
(Secondary follicles develop and development of Graafian follicle) - Ovulatory phase
(Release of mature follicle) - Luteal phase
(Formation of corpus luteum)
If fertilisation doesn’t happen, corpus luteum degenerates and becomes corpus albicans (stops producing progesterone) and slowly disappears.
Ovarian and endometrial cycle:
What happens in the Proliferative (follicular) phase?
- Secondary follicles mature
- Granulosa cells secrete oestrogens
- Oestrogen: causes the epithelial cells of the endometrium to divide rapidly.
- Endometrium thickens
Ovarian and endometrial cycle
What happens in the Secretory (Luteal) phase?
- The corpus luteum begins to secrete progesterone and smaller amounts of oestrogen.
- Progesterone: causes the cells of the endometrium to become larger and to secrete a small amount of fluid.
- Fullest development of endometrium
- If no fertilisation – corpus luteum degenerates – progesterone drops
What cells/structure in the ovary secrete oestrogen?
Granulosa cells?
Corpus luteum?
Theca cells?
Granulosa cells
Are oogonia haploid or diploid?
Oogonia are tiny DIPLOID germ cells that pass through mitotic divisions and originate the primary oocytes.
Oocytes are haploid, anything before that are diploid
Feed back mechanisms: overall
- Oestrogen
- Postive feedback before ovulation,
- resulting in increased LH and FSH secretion;
- Negative feedback (with progesterone) on the hypothalamus and anterior
pituitary after ovulation, resulting in decreased LH and FSH secretion - Progesterone
- Negative feedback (with oestrogen) on the hypothalamus and anterior
pituitary after ovulation, resulting in decreased LH and FSH secretion
Hormonal control of the reproductive cycle
Follicular Phase
- Oestrogen (developing follicles) stimulates GnRH secretion from hypothalamus
- GnRH triggers FSH and LH
- FSH stimulates oestrogen secretion at an increasing rate from the developing follicles.
- This positive-feedback loop produces a series of larger and larger surges of FSH and LH
secretion
Hormonal control of the reproductive cycle
Ovulation
- Ovulation occurs in response to
the large increases in LH levels - about day 14 of the menstrual
cycle - This large increase in LH is also
responsible for the
development of the corpus
luteum
Hormonal control of the reproductive cycle
Luteal Phase
- Corpus luteum begins to secrete progesterone and oestrogen
- Progesterone: cells of the endometrium to become larger
- Negative Feedback: Together, progesterone and oestrogen act on the hypothalamus and
anterior pituitary gland to
inhibit GnRH, LH, and FSH
secretion. - LH and FSH levels decline
- No stimulation of follicles
- Corpus luteum degenerates -
Lower progesterone
Inhibin has a smaller role, helps maintain steady levels
Hormonal control of the reproductive cycle
Menses
- Oestrogen and progesterone secretion is low
- In response to declining progesterone levels, the endometrial lining of the uterus
sloughs off, resulting in menses - The rate of LH remains low, and
- The rate of FSH secretion increases as progesterone levels decline (negative feedback
released) - Stimulates development of follicles
- Start to release oestrogen
When Fertilisation does not occur:
- The egg lives for 12-24 hrs
- Takes 5 days to reach Uterus
- Fertilisation must occur in uterine tube
- Endometrial development continues
- Progesterone production
Fertilisation
- hCG from pituitary and later placenta maintains corpus luteum
- Oestrogen and progesterone levels maintained
- Endometrium doesn’t break down
- Subsequently Placenta takes over progesterone and oestrogen
production
Contraception
Chemical Methods
* Synthetic oestrogen and progesterone in oral contraceptives * among the most effective contraceptives - 99.9% effectiveness.
* Synthetic steroids can have more than one action* Generally they reduce LH and FSH release from the anterior pituitary.
* Oestrogen and progesterone are present in high enough concentrations to have a negative-feedback effect on the pituitary* prevents the large increase in LH and FSH secretion that triggers ovulation
* Mini-pill
* contains only synthetic progesterone* reduces and thickens the mucus of the cervix
* Prevents sperm cells from reaching the oocyte
what cells/structure in the ovary secrete androgens
Theca cells
Corpus luteum
Granulosa cells
Theca cells
(granulosa cells secrete oestrogens)
Which hormone stimulates ovulation?
LH or FSH
LH
What does FSH do?
Stimulates follicular development
Which hormone triggers the LH surge?
Oestrogen
Which hormones do pregnancy tests detect?
hCG- human chorionic gonadotrophin
What are sertoli cells?
A structure that nuture the developing spermatozoa
A duct that transports spermatozoa
Location where spermatozoa are formed
Location where spermatozoa mature
What is the function of the epididymis?
A structure that nuture the developing spermatozoa
A duct that transports spermatozoa
Location where spermatozoa are formed
Location where spermatozoa mature
What is the function of the vas deferens?
A coiled tube that carries the sperm out of the testes
Where are sperm cells produced?
Are spermatids haploid or diploid?
Graafian follicle
Which follicle ruptures at ovulation?
What are the important features of gametes?
What are the 3 classes of RH?
What is the corpus luteum?
What does inhibin do?
