Reproduction, Development and Health

what are the paired gonads

ovaries

what are the duct systems

paired uterine tubes, single midline uterus, single midline vagina

The ovary

Produce gametes and hormones, endocrine and exocrine function

Blood supply, venous and lymphatic drainage of the ovaries

Blood supply - ovarian artery, arises from aorta at level of the kidney

Venous drainage - ovarian vein, drains to IVC on right and left renal vein on the left

Lymphatics - drain to aortic nodes at the level of renal vessels

What are the ligaments of the female reproductive system and their roles

broad - peritoneal sheet draped over uterus and uterine tubes, ovaries attached to the posterior layer by short mesentery

Ovarian - fibrous cord which links ovary to uterus

Suspensory ligament - carries ovarian artery and vein, lateral wall of pelvis to ovary

Round - connects uterus to the labia majora

What are the 2 peritoneal pouches of female reproductive system

Rectouterine - extension of peritoneum into the space between the posterior wall of uterus and the rectum

Uterovesicle - fold of peritoneum over the uterus and bladder

What are the parts of the uterine tubes

infundibulum - funnel shaped opening to peritoneal cavity, fimbriae projections

ampulla - middle section where fertilisation occurs

interstitial part

isthmus - short narrow section connected to uterine wall

The uterus

lies in midline, where the embryo/foetus grows

Parts of the uterus

body

cervix - cervical canal, internal os and external os

Fundus - rounded part which projects up above the level of uterine tubes

isthmus - narrowing between body and cervix

blood supply, venous and lymphatic drainage of the uterus

uterine artery, branch of internal iliac artery

uterine vein - drains to internal iliac vein

lymphatics - drainage of body and cervix differ

• body to para-aortic nodes

• cervix to internal iliac nodes

The testes - duct system and accessory glands

exocrine and endocrine glands

duct system - closely associated with urinary system, share final duct urethra

accessory glands - one prostate, two seminal vesicles, two bulbourethral glands

what is the scrotum made up of

skin

dartos muscle

external spermatic fascia

cremaster muscle

cremaster fascia

internal spermatic fascia

cremaster muscle

skeletal muscle

deep to dermis

runs within the spermatic cord

contracts to raise testes in cold weather

Position and covering of the testes

Extra abdominal

suspended at different levels

tunica vaginalis of the testes:

a closed sac of peritoneum;

• visceral and parietal layers

• space between containing film of peritoneal fluid

what happens when there is excess fluid in the tunica vaginalis

hydrocoele

Duct system of the testes

The ends of a coiled seminiferous tubule join to form a straight tubule

all the straight tubules join to a network rete testes

from this network, efferent ductules leave and join epididymis

The epididymis

a very coiled tube, continuous with the ductus deferens

lined by pseudostratified columnar epithelium with stereocilia

• stereocilia increase the area for absorption of fluid and can monitor and adjust the fluid composition

blood supply, venous and lymphatic drainage of the testis

testicular artery

pampiniform plexus → testicular vein → IVC on right and renal vein on left

Different lymphatic drainage of testes and scrotum:

• testes to paraaortic nodes

• scrotum to inguinal node

The ductus deferens

thick walled, smooth muscle in the wall which contracts by peristalsis

Runs in spermatic cord, through inguinal canal

lies on side pf pelvis and turns medially to base of bladder

enlarges at end - ampulla region

also attached here to seminal vesicles

Seminal vesicles

convolted tubular glands

secretes alkaline viscous fluid which helps to neutralise the acidic environment of the vagina

fluid also contains:

• fructose used for ATP production by sperm

• prostaglandins which aid sperm mobility and viability and may also stimulate muscle contraction in the vagina and uterus

Ejaculatory duct

duct of the seminal vesicle joints with the ductus deferens on each side to form the ejaculatory duct

penetrates the prostate gland empties into the urethra

The prostate gland

surrounds the beginning of the urethra

secretes a slightly acidic fluid containing citrate, acid phosphates and proteolytic enzymes which liquidity coagulated sperm

passes its secretions to the urethra

Bulbourethral glands

produce a mucus like secretion

ducts open to spongy urethra

what is meiosis

a special form of cell division which is used to form gametes

prophase 1

chromosomes condense, bivalent forms between homologous chromosomes and crossing over occurs

metaphase 1

spindle fibres attach to the bivalents and they will line up along the metaphase plate at the equator of the cell

anaphase 1

bivalents are pulled to opposite poles of the cell

telophase 1

chromosomes decondense, nucleus may reform, cytokinesis to form 2 haploid daughter cells

prophase 2

chromosomes condense, nuclear membrane disintegrates and centrioles move to the opposite poles

metaphase 2

spindles attach to the chromosomes at the centromere and they will line up along the equator of the cell

anaphase 2

spindles will pull the sister chromatids to opposite poles and they are now referred to as chromosomes

telophase 2

the chromosomes decondense, nucleus reforms, cytokinesis to form 4 haploid daughter cells

what is crossing over

occurs at meiosis 1, this is when he maternal and paternal genetic information will cross over, this occurs between homologous chromosomes

what is random assortment

when the chromosomes will line up in a randomised order

what is the starting germ cell of gametogenesis

primordial germ cell

Outline the process of oogenesis

primordial germ cell will move and find a home in the developing gonad, they will divide to populate the area and then undergo meiosis to form gametes. Firstly they will become oogonia, oogonia will then become a primary oocyte, this is halted at prophase 1 and will remain like this until puberty and are not primary oocytes, once puberty occurs a few of these oocytes will be selected to proceed and will undergo meiosis up until metaphase 2, they are now secondary oocytes. Each month from puberty one of these secondary oocytes will be selected to be fertilised, if fertilisation occurs when it will undergo the rest of meiosis.

what are polar bodies and when are they produced

polar bodies are produced in order to allow the oocyte to keep cytoplasm and loose as much genetic material as possible, this is lost in the polar bodies at metaphase 2 and fertilisation

what is happening parallel to the development of oocytes

the development of the follicle from primordial → primary → secondary → release of oocyte → corpus luteum

Outline the process of spermatogenesis

again it starts with primordial germ cells which will become spermatogonia, there is two types of spermatogonia - type a and type b, type a is used to populate the testes and type b is used in gamete formation, this process occurs via mitosis.

the type b spermatogonia is going to divide via mitosis to form primary spermatocytes

the primary spermatocyte will divide by meiosis to become two secondary spermatocytes

these secondary spermatocytes will divide to become 4 spermatids

outline the process of spermiogenesis

this is when the spermatids will undergo differentiation to become spermazoa, they will loose their cytoplasm to make them more motile, they will gain an acrosome over the nucleus which contains enzymes to allow them to penetrate the egg and the midpiece (the neck) which contains mitochondria which will provide energy, and will gain flagellum to allow them to be motile.

what are the layers of the uterus

perimetrium, myometrium, endometrium

what is the function of the myometrium

to contract, it is a smooth muscle, contraction during menstruation and child birth

what is the role of the endometrium

this is the mucus membrane of the uterus, this is where the embryo would implant into, if no implantation occurs when the endometrium will shed in menstruation

what are the cell of the endometrium and their layers

glandular cells, they travel from the bottom to the top, they can be divided into the stratum basalis and stratum functionalis

what happens to the glandular cells during proliferation

they get larger in order to support a potential implanting embryo

what is the blood supply of the two regions of the endometrium

stratum basalis - straight arteries

stratum functionalis - spiral arteries

what hormone will drive the proliferation of the endometrium

oestrogen - it will travel from the ovaries to the uterus and act on the glandular cells to grow and proliferate and form a nutrient rich environment for an embryo

what part of the endometrium is shed in menstruation

stratum functionalis, the basalis remains intact and this allows the formation of a new endometrium to happen much quicker as if it was lost too it would take too long, this has to be achieved monthly

what happens to the endometrium after ovulation and before potential implantation

the oocyte will move to the uterus, the hormones will change and will now mainly be progesterone due to the corpus luteum, this will drive the development of the uterus

what happens to the endometrium when fertilisation and implantation does not occur

when the oocyte is released it has the opportunity to be fertilised, if it is and pregnancy occurs then the corpus luteum will continue to produce progesterone which allows the cells to remain thick and big, if pregnancy does not occur then the corpus luteum will degenerate, this will stop the production of progesterone and therefore cause glandular cells to die. when they die they will compress the surrounding spiral arteries, this will cause reduced tissue perfusion, cells die and arteries become backed up with blood due to compression, eventually they will burst and this will be expelled as a period, alongside the dead tissues.

what cells are found in the ovary

follicular cells

what is the starting follicle in the ovary

primordial follicle

what is the function of the follicles

they are there to support the oocyte and provide it with nutrients

what does the appearance of a primordial follicle look like compared to a primary follicle

primordial only has one layer of cells surrounding the oocyte vs primary will have multiple layers of cells surrounding the occyte

discuss the development of follicles throughout life

at birth they will be primordial, at puberty they will be selected in clusters to become primary and then monthly a few will be selected to become secondary, of the secondary one will be chosen to release an oocyte

what does the appearance of a secondary follicle look like

it has the oocyte, also an antrum which is a fluid cavity

they also have follicular cells which can be split into theca or granulosa

• granulosa is found surrounding the oocyte

• theca is found surrounding the entire cell

what are the two divisions of theca cells in the secondary follicle

interna and externa (interna contains blood vessels)

what is released by theca cells

androgens

what happens to androgens in the follicular cells

they will be converted to oestrogen using aromatase which is produced by the granular cells

how does the follicle cause release of the oocyte

it occurs due to enlargement of the antrum, the antrum gets too large and pressure build up will cause the follicle to burst, this will cause the release of the oocyte, the oocyte can now be fertilised and can carry out meiosis 2

pregnancy, what happens within the ovaries

the corpus luteum will form and will secrete progesterone, this will maintain a healthy endometrium which is supportive for the embryo

what does the corpus luteum contain

it has a lot of white fatty spaces, this is filled with cholesterol as cholesterol is essential in the hormonal synthesis and these hormones are required to maintain pregnancy

what are the main proteins and steroids of hormones

follicle stimulating hormone, luteinising hormone, oestrogen, progesterone and androgens

what are steroids synthesised from

cholesterol - this is why there is fatty deposits of cholesterol found in the corpus luteum

what are the types of oestrogens

oestrogen and oestrodiol

where is oestrodiol produced

ovary, derived by direct synthesis of developing follicles or through conversion of oestrogen

where is oestrogen produced from

ovary and converted from androstenedione

what is responsible for conversion of androgen to oestrogen

aromatase

what are oestrogens involved in

development in secondary sex characteristics, control of menstrual cycle and pregnancy

where are androgens produced

testes, the ovary and the adrenal gland

what is the function of androgens

development of male primary sex organs, secondary sex characteristics and are important in libido and sexual arousal

where are progesterones synthesised

synthesised from cholesterol via pregnenolone

primarily produced in corpus luteum of ovary, the adrenal gland and in the placenta

hypothalamic pituitary gonadal axis

the hypothalamus secretes gonadotrophin released hormone, which stimulates the anterior pituitary to release follicle stimulating hormone and luteinising hormone. the ovary responds to levels of GnRH and secrete sex hormones

role of pituitary gland in menstrual cycle

anterior pituitary secretes peptide hormones - GnRH, FSH, LH which act on the ovary

posterior pituitary secretes oxytocin - involved in child birth and lactation

ovaries and the 3rd level of hormonal control

Levels of FSH and LH trigger follicle maturation and regulate steroid hormone production in the ovary

These hormones act on the target tissues in the reproductive tract

Responding to blood levels of the anterior pituitary hormones, the granulosa cells of the ovarian follicles convert androgens (androstenedione and testosterone) which are secreted by the thecal cells into oestrogens (oestrone and oestrogen) which pass into the bloodstream

what is the principle secretory product of the follicle after ovulation

progesterone

FSH

Initiated recruitment of follicles

Supports growth of the follicle, especially the granulosa cells

LH

Supports theca cells

Receptors expressed on maturing follicle

LH surge triggers ovulation

stages of the menstrual cycle

preovulatory follicular phase and postovulatory luteal phase 

Hormonal control of the menstrual cycle in follicular phase

Varies in length (10-14d)

Characterised by growth of dominant follicle

Progesterone production is low

Oestrogen is rising due to conversion of androgens to oestrogens via aromatase

15-20 follicles selected to grow

 

development of secondary follicle in regards to hormonal control

FSH secretion increases slightly, stimulating further growth of recruited follicles

Circulating LH levels increases slowly, beginning 1 to 2 days after the increase in FSH

Theca develops - follicle gains an independent blood supply

Granulosa cells develop FSH, oestrogen, and androgen receptors

Recruited follicles increase production of oestrodiol via conversion of androgens produced in the theca interna into oestrogens by the granulosa cells - aromatase

Stimulates FSH and LH synthesis but inhibits their secretions

FSH levels decrease. FSH and LH levels diverge partly because oestrodiol inhibits FSH secretion more than LH secretion

Developing follicles produce the hormone inhibin, which inhibits FSH secretion but not LH secretion

Levels of oestrogen, particularly oestrodiol increase exponentially

 

Ovulation and hormonal control

Towards the end of the proliferative phase, rising oestrogens

• Increase responsiveness of pituitary to GnRH

• Surge in hypothalamic secretion of GnRH

Oestrodiol peaks and progesterone levels begin to increase

High levels of oestrodiol trigger LH secretion by gonadotropes (positive feedback)

Stored LH is released in massive amounts (LH surge), usually over 36 to 48 hours, with a smaller increase in FSH

Ovulation occurs around day 14

Oestrodiol decreases

 

The LG surge stimulated enzymes that indicate breakdown of the follicle wall and release of mature oocyte within about 16 to 32 hours

The LH surge also triggers completion of the first meiotic division of the oocyte within about 36 hours of ovulation

 

Luteal and secretory phase - hormonal control

The length of this phase is the most constant, averaging 14 days

Formation of the corpus luteum from the follicle

The corpus luteum secretes primarily progesterone in increasing quantities, peaking at about 6-8 days after ovulation

Progesterone stimulates development of the severity endometrium

Because levels of circulating oestradiol, progesterone and inhibin are high during most of the luteal phase, FSH and LH levels decrease

Oestradiol and progesterone levels decrease late in this phase

If implantation occurs, the corpus luteum does not degenerate but remains, supported by human chorionic gonadotropin that is produced by the developing embryo

 

Corpus luteum secretes progesterone

• Progesterone has a negative feedback effect to inhibit LH/FSH secretion

Corpus luteum

The corpus luteum plays a crucial role in the establishment and maintenance of pregnancy

If pregnancy occurs, cells within the developing embryo begin to produce a hormone called Human Chorionic Gonadotrophim (hCG) at around 9 days

hCG is the hormone which a pregnancy test will detect

hCG signals to the corpus luteum to continue to secrete progesterone, which in turn maintains the lining of the endometrium

Menstruation - hormonal control

Regression of the corpus luteum and a reduction in the secretion of progesterone

Leukocyte infiltration of endometrium

Constriction and breakdown of spiral arteries - ischaemia

Menstruation begins

Inhibin is carried by the bloodstream to the pituitary where it directly inhibits the secretion of gonadotrophins, especially FSH, although LH is also decreased. This inhibition results in the regression of the CL and a reduction in the secretion of progesterone by the ovary.

hormonal effects on the vagina

early follicular phase - oestrogen is low - vaginal epithelium is thin and pale

late follicular phase - oestrogen increases - squamous cells mature, causing epithelial thickening

luteal phase - mature squamous cells shed as cellular debris

hormonal effect on the cervix

late follicular phase - oestrogen levels increase - increased cervical vascularity and watery mucus - allows sperm passage, external os opens slightly and fills with mucus

luteal phase - progesterone levels increase - thickens cervical mucus, reduces elasicity

where in the body is sexual behaviours regulated

brain and spinal cord

what is coitus

the engagement in sexual intercourse which resorts in the deposition of semen into the vagina at the level of the cervix.

what are the stages that occur in humans which allow the fertilisation of an oocyte by sperm

coitus and conception

how can an individual become sexually aroused

by touch or visual stimuli

what are factors which can influence sexual arousal

attitude, behaviour, mood and health

is penis erection needed for coitus

yes

physiology of penis erection

the penis becomes engorged with blood, and the testis and penis both enlarge in size

what nerve levels are responsible for erection

S2 and S3

what are other systemic effects that occur as a result or erection

increased breathing rate, increased heart rate and skeletal muscle will become tense

what can cause erectile dysfunction

neurological damage

provide an example of a drug used in a case of erectile dysfunction

viagra

is erection needed for arousal in a female

no

physiology of the vagina in coitus

the vagina and clitoris will engorge with blood, the circumference of the vaginal opening will increase, labia minora will deepen in colour. there is an increase in the secretions of the vagina via glands and cervix which will provide lubrication