Reproductive Physiology Flashcards
What is the function of the reproductive system?
Production of gametes
Organs for mating
Fertilization
What are the organs of the reproductive system?
Gonads
Pathway of gamete transport
Accessory reproductive organs/glands
What is the function of gonads?
Gamete production
Secrete sex hormones
What are the male gonads?
Testes
What is the scrotal sac?
Outside of the body
Testes, blood vessels, nerves
Has concurrent blood flow to regulate temperature in this region
How do the testes descend?
First found in the abdominal cavity and descend to their final position in the scrotum
During 8 and 12 weeks, the testes move down towards the inguinal canal
Between the 7th and 9th months, the testes pass through the inguinal canal and come to rest in the scrotum
What are the testes?
Male gonads
250-300 compartments
Has seminiferous tubules that are important for sperm production
What are the seminiferous tubules?
Spermatogenic cells, site of sperm production
Spermatogenesis begins at puberty
400 million sperm/3 mL of ejaculated volume
What are the cells of the testes?
Leydig cells
Sertoli cells
Smooth muscle (myoid cells)
What are Leydig cells?
Secrete testosterone
Found in the connective tissues surrounding the seminiferous tubules
What are Sertoli cells?
Support sperm development
What are the myoid cells?
Just outside of the basement membrane
Muscle-like cells
have contractile properties to help with peristalsis to move the sperm forward
What forms the blood-testis barrier?
Tight junctions
Luminal compartment
Basal compartment
What are the functions of Sertoli cells?
Support sperm development
Secrete luminal fluid for sperm housing
Secrete androgen-binding protein
Acts as target cells for testosterone and follicle-stimulating hormone
-secrete paracrine factors that stimulate spermatogenesis
Secrete inhibin
-hormone of negative feedback loop for FSH
Phagocytosis of old and damaged sperm
Site of immunosuppression
Why do testosterone and FSH use Sertoli cells?
As their target and help in sperm development
What is testosterone?
Steroid hormone synthesized from cholesterol
Produced by the adrenal cortex and gonads
What is progesterone?
An intermediary hormone synthesized from cholesterol and produced in the adrenal gland
Depending on the enyzmes present, progesterone is converted to mineralocorticoids, glucocorticoids, or androgens
Where are testosterone receptors generally located?
In intracellular locations
Testosterone is lipophilic and can diffuse across membranes and bind to intracellular receptors to exert its function
Acts by influencing gene transcription and affecting protein synthesis
How are male hormones synthesized in Leydig cells?
Cholesterol to pregnenolone to progesterone
Progesterone produce androgens
What happens when testosterone enters the bloodstream?
Maintains the lifelong male reproductive capacity
Converted to DHT and maintains tissues or sexual characteristics
Converted to estrogen
What happens during puberty?
Onset of male hormone synthesis
Sexual maturation
Reproductive organs mature
Secondary sexual characteristics develop
What is the pattern of male reproductive activity over the human lifespan?
Continually produce sperm over the lifespan
What is the hypothalamic-pituitary-Leydig cell axis?
Cues to initiate firing of the cells that produce the hormone gonadotropin-releasing hormone
What are the effects of androgens?
Stimulate spermatogenesis
Promote development of secondary sex characteristics during puberty and maintenance of these characteristics in adult life
Increase sex drive
Promote protein synthesis in skeletal muscle
Stimulate growth hormone secretion, promotes bone growth
Promote development of male reproductive structures during embryonic life
What is spermatogenesis?
The formation of the male gamete or the sperm
Where does the formation of sperm begin?
Close to the basement membrane in the seminiferous tubule and then goes to the lumen
Why does one daughter cell remain spermatogonia?
To ensure that resources are not depleted from the stockpile of spermatogonia
Where does spermatogenesis occur in relation to the Sertoli cells?
Occurs in the space between adjacent Sertoli cells
What is the final step of spermatogenesis?
Must undergo differentiation to form the final sperm structure
How long does spermatogenesis take?
64 days
What is spermiogenesis?
The last stage within spermatogenesis
Spermatids mature into motile spermatozoa
Flagella forms
Takes 24 days
What is the structure of the head of sperm?
Contains the nucleus
Contains an acrosome
What is an acrosome?
A vesicle positioned close to the plasma membrane at the tip of the sperms head with enzymes necessary for fertilization
What is the mid-piece of sperm?
Many mitochondria which generate ATP needed for movement of the tail
What is the tail of sperm?
Whip-like movements propel the sperm
Where are spermatozoa released?
Into the lumen of the seminiferous tubules where they remain immotile for 20 days
How does the sperm get to the epididymis?
Pressure generated by the fluid secreted from the Sertoli cells pushes the sperm and fluid to the epididymis
What happens in the epididymis (sperm)?
Resides there for 6-12 days
Acquires mobility with an initial wave-like tail movement
Most of the fluid is reabsorbed
Sperm is concentrated?
How does sperm get to the vas deferens?
By peristalsis
How long does sperm stay in the vas deferens?
Until ejaculation
How does FSH control male reproduction?
Stimulates spermatogenesis
How does LH control male reproduction?
Stimulaters androgen secretion
What is the pulse generator?
GnRH
The pulse generator stimulates the anterior pituitary to release FSH which stimulates the Sertoli cells to secrete androgen binding protein and inhibin
What is inhibin?
Peptide hormone
Regulate the axis at the level of the anterior pituitary to decrease secretion of FSH
Does not act at the hypothalamic level
What does LH act on?
The Leydig cells
How is LH release controlled?
Testosterone released from Leydig cells inhibits the secretion of LH at the level on the anterior pituitary and at the level on the hypothalamus
What does FSH act on?
Sertoli cells
How is FSH release controlled?
Release of FSH from the anterior pituitary is inhibited by inhibin released from the Sertoli cells
Inhibin acts on the level of the anterior pituitary
What are the functions of seminal fluid?
Dilution of sperm
Provision of energy
Formation of semen clot
Where does seminal fluid come from?
Seminal vesicle
Prostate gland
Bulbourethral gland
What are seminal vesicles?
Secrete alkaline fluid with fructose, enzymes, and prostaglandins
- enzymes for semen clot
- alkaline to balance acidic environment in female genital tract
- prostaglandins to cause contraction of female tract for sperm to move forward
What is the prostate gland?
Secretes citrate and enzymes (PSA)
Hypertrophy is a biomarker for cancer
What are the bulbourethral glands?
Secrete viscous fluid with mucous
What makes up semen?
Sperm + seminal fluid
What is the male sexual response controlled by?
The autonomic nervous system
Involves spinal reflexes
What are the phases of the male sexual response?
Erection phase
Emission phase
Ejaculation phase
What is the erection phase?
Controlled by parasympathetic nervous system
Increased blood flow
What is the emission phase?
Sympathetic stimulation to the smooth muscle of the ducts
What is the ejaculation phase?
Rapid contraction of skeletal muscle for semen expulsion which is under somatic control
What is the parasympathetic control of an erection during and erection?
Activity in the sympathetic neurons decreases
Activity in the parasympathetic neurons to the penile structures increases, causing relaxation of the smooth muscle which increases blood flow
What is parasympathetic control of an erection?
Activation of the parasympathetic nerve causes the release of nitric oxide
NO stimulates production of cyclic GMP
Increased cGMP acts on smooth muscle of the blood vessels to cause vasodilation
cGMP is broken down by phosphodiesterarse and the erection stops
What is erectile dysfunction?
Treated with Viagra
Viagra is an inhibitor of phosphodiesterase
Whaat is the fallopian tube?
Site where fertilization occurs
Only low numbers reach the fallopian tube due to the high acidity in the female reproductive tract
What is capacitation?
Occurs as sperm moves through the female reproductive tract
A functional maturation process of the sperm cell membranes
Receptors are made available through the removal of the glycoprotein layer
The area of the acrosomal cap is altered during capacitation so that the acrosomal reaction can take place
What is the acrosomal reaction?
Oocytes have an outer layer called the zona pellucida
Sperm must penetrate the zona pellucida to gain access to the egg
Binding of the sperm with the zona pellucida triggers the acrosomal reaction
Allows acrosomal enzymes to be releases by exocytosis that allow the sperm to digest a path through the zona pellucida for fertilization to occur
What are some characteristics of the female reproductive system?
Cyclic changes in activity -menstrual cycle Restricted periods of fertility -ovulation Limited gamete production -pool established at birth
What are the patterns of female reproductive activity?
Onset of puberty (menarche)
Female reproductive system cycles (menstruation)
Menopause
What are the female gonads?
Ovaries
What composes the female reproductive tract?
The uterus, uterine tube, vaginal canal
What is the site of ova maturation?
The ovaries
Are the ovaries directly linked to the uterine tubes?
No, they are suspended by ligamentous tissue in the peritoneal cavity
What are the uterine tubes (fallopian tubes, oviducts)?
Transports the ova from ovaries to uterus
Fimbria stick out and sit close to the ovary and contain hair cells that move help move the egg
What is the infundibulum?
A cup-shaped structure that captures the egg from the ovary
How does the ovum move through the uterine tube?
Initially by peristaltic contraction
Mostly ciliary actions
How long does it take to get to the uterus from the uterine tubes?
4 days
What is the perimetrium?
The outer layer of the uterus
Epithelial cells and connective tissue
What is the myometrium?
Middle layer
Thickest layer
Smooth muscle
What is the endometrium?
Inner layer of the uterus
Layer of epithelial cells and connective tissue
Numerous glands that contains things like glycogen
What is the site of fetal development?
Body = upper portion
Cervix = canal leading to vagina
Cervix + vagina = birth canal
What are follicles in female reproduction?
Densely packed shells of cells containing an immature oocyte at all stages prior to ovulation
What is the structure of the ovary?
Covered by a capsular structure
Contains follicles
Contains blood vessels
What is the corpus luteum?
Formed in the ovary at the site of a follicle, or sac, which has matured and released its egg
Remains for a while and acts as an endocrine gland
What is the hormonal-ovarian-uterine cycle?
The 3 different cycles in the female body
Cyclical change is on average 28 days
What is the first phase of the ovarian cycle?
Follicular phase = first 14 days
Development of the follicles in which the eggs are growing
Ovulation occurs on the 14th day
What is the second phase of the ovarian cycle?
Luteal phase = the last 14 days
The structure from which the egg is released and it is related to a secretory gland known as the corpus luteum
What is the first phase of the uterine cycle?
Menstrual phase
Day 1 = first day of menstrual bleeding of shedding the surface of the endometrial layer
4 to 5 days of menstrual bleeding
What is the second phase of the uterine cycle?
Proliferative phase
Phase of development or growth
Layers become wider in the endometrium and the blood vessels are growing
Function layer of the endometrium develops
What is the third phase of the uterine cycle?
Secretory phase
Further vascularization and development of uterine glands
What uterine and ovarian phases coincide?
Menstrual + proliferative phases and the follicular phase
Secretory phase and the luteal phase
What is oogenesis?
The development of the oocyte
What is folliculogenesis?
The maturation of the ovarian follicle
What does each follicle contain?
1 oocyte
What are primordial follicles?
A single oocyte surrounded by a single layer of epithelial cells (granulosa cells)
What is theca?
Internal and external
Differentiated granulosa cells that form layers
What is the primary follicle stage?
Larger than the primordial follicle
Proliferation, growth
Granulosa cells secrete proteins and glycoproteins which form the zona pellicida
What is the preantral follicle?
Mitosis of granulosa cells results in many layers of granulosa cells around the oocyte
Connective tissue surrounding granulosa cells differentiate and become early theca cells
Do not have an antrum
What are early antral follicles?
A fluid-filled space known as the antrum begins to form
What is a mature follicle?
Major growth is due to the growth of an antral space
Granulosa cells just outside the oocyte undergo changes
What are the corpus Albicans?
Empty follicle which functions as a temporary endocrine structure that will die off
What is the dominant follicle?
10 to 25 follicles are randomly selected in each cycle
The follicle that secretes the highest amount of estrogen will become the dominant follicle
The remainder will die off
What other cycle happens at the same time as oogenesis?
Folliculogenesis
What do granulosa cells do?
They send out cytoplasmic processes through the zona pellucida and form gap junctions with the oocyte
Nutrients and paracrine factors are sent through these junctions to help the growth of the oocyte
What is the estrogenic phase?
During the follicular phase when the dominant follicle is selected and as they start growing they produce estrogen
What is the follicle converted to following ovulation?
The corpus luteum
If there is no pregnancy, it dies off
What are the effects of FSH during the early/mid-follicular phase?
FSH stimulates granulosa cell multiplication, produce estrogen, and further growth of granulosa cells and more estrogen
Theca cells have LH receptors
LH stimulates thecal cells to secrete androgens
Androgens permeate to granulosa cells and converted to estrogen in granulosa cells
Estrogen secretion rises and dominant follicle is selected
Can granulosa cells make estrogen from cholesterol?
No
What does FSH upregulate?
An enzyme that converts androgens to estrogen in granulosa cells (aromatase)
What are the effects of estrogen on the early/mid-follicular phase?
Upregulates LH receptors on granulosa cells
Progesterone receptors on uterine
What do the granulosa cells secrete?
Antral fluid Paracrines that support follicle development Inhibin Estrogens Substance that forms the zona pellucida
What happens during the late follicular/corpus luteum phase of the ovarian cycle?
The rise in estrogen causes granulosa cells to start developing LH receptors so that they can convert cholesterol into progesterone
What is the pulse generator in females?
GnRH
The frequency and amplitude of pulses change every 24 hours over the course of a menstrual cycle
LH and FSH act on the ovary and estrogen and progesterone are produced by the granulosa cells
How does estrogen provide feedback?
Negative feedback at the level of the anterior pituitary and the hypothalamus
-dampen amplitude of the pulse generator or reduce the responsiveness of the pituitary to GnRH
Can also be positive feedback
-can act on the hypothalamus to increase the amplitude and the responsiveness of the pituitary to GnRH
How does progesterone provide feedback?
Negative feedback effect at the level of the pituitary and the hypothalamus
No positive feedback
What is oogenesis?
The process by which female gametes, ova, are created
What is the deal with meiosis 1?
It is arrested through birth until puberty
After puberty an oocyte is released from arrest and completes its meiosis 1 division
What is the deal with meiosis 2?
Only happens after ovulation and fertilization
What is the net result of oogenesis?
1 primary oocyte produces 1 egg
What is the net result of spermatogenesis?
1 primary spermatocyte produces 4 spermatozoa
What are the physiological actions of ovarian hormones?
Not required for female sexual differentiation before birth
Required for sexual maturation at puberty and secondary sexual characteristics
Maintaining sexual capacity in adult life
Regulation of the hypothalamic-pituitary gonadal axis
-E = + and - feedback
-P= - feedback
-inhibin = - feedback on FSH
What are the hormonal influences on the menstrual cycle?
Uterine changes are caused by changes in plasma concentrations of estrogen and progesterone
What is day 14 of the menstrual cycle?
Ovulation
What happens during days 1 to 7 of the menstrual cycle?
10 to 25 follicles are secreted
What happens by day 7 of the menstrual cycle?
One follicle becomes dominant
What does estrogen have an inhibitory effect on?
On gonadotropin secretion when plasma estrogen levels are relatively low during the early and mid-follicular phase
When does estrogen start increasing?
During the early proliferative phase
Estrogen starts growing from follicles
Very quick rise in estrogen levels before day 14
When does estrogen start decreasing?
Before LH peaks
What is androgen production and release during folliculogenesis dependent on?
The stimulation of the theca cells by LH
What does rapidly increasing estrogen in the late follicular phase cause?
A sharp rise in LH, called the LH surge
Estrogen at high levels causes a positive feedback on the gonadotropins
What is a sharp increase in LH accompanied by?
A small rise in FSH levels
What does the LH surge cause?
Ovulation
What happens when LH and FSH levels decrease?
Estrogen levels also decreased because the dominant follicle has gone through the process of rupture and release of the oocyte
Why does estrogen peak again during the luteal phase?
Because the corpus luteum makes estrogen
What are the levels of progesterone like during the menstrual cycle?
Levels are low during most of the follicular phase
Near the end of the follicular phase, there is a small increased in progesterone levels from the granulosa cells
After the corpus luteum is formed there is a large increase of progesterone
What are the effects of estrogen in the late follicular phase?
Initiation of LH surge due to positive feedback action of estrogen
In the late follicular phase high levels of estrogen cause the LH surge
What hormones does the corpus luteum secrete?
Both estrogen and progesterone
Why do the gonadotropins, LH and FSH remain low during the luteal phase
High plasma concentration of progesterone causes a decrease in the secretion of the gonadotropins from the pituitary
Estrogen and progesterone produce negative feedback to suppress LH and FSH
Gonadotropin levels must be kept low so that another LH surge does not occur in the luteal phase or during pregnancy
What happens in the dominant follicle?
Stimulation of meiosis 1 in the oocyte
Estrogen secretion starts decreasing after ovulation
Progesterone secretion increases
Ovulation
Transformation of the follicle into the corpus luteum
What do high levels of estrogen do?
Act on the anterior pituitary to enhance the sensitivity of LH-releasing cells to GnRH and also stimulate GnRH release from the hypothalamus
What happens during the menstrual phase of the uterine cycle?
Days 1 to 5
Shedding of uterine lining
Tissues die and slough into the vagina causing menstrual flow
What is the hormonal control of menstruation
Triggered by decreased estrogens and progesterone
Hormones decrease when the corpus luteum degenerates
What happens during the proliferative phase of the uterine cycle?
The uterus prepares for fertilized ovum
- endometrial lining develops
- endometrial layer grows
- endometrial glands enlarge
- smooth muscle layer thickens
- cervical glands secrete a thin mucus
What is the hormonal control of the proliferative phase?
Estrogens stimulate the development of the uterine lining
What happens during the secretory phase of the uterine cycle?
Endometrium is prepared for implantation
- blood supply increased
- glands enlarge and secrete glycogen-rich fluids
- cervical secretions more sticky forming a plug
What is the hormonal control of the secretory phase?
Progesterone and estrogen
How does estrogen target the ovaries?
Increased growth of follicles
Increased receptors for E, P, FSH, and LH
How does progesterone target the ovaries?
Decreased FSH-induced E production, decreased receptors for E
How does estrogen target the fallopian tubes?
Increased growth, contractility, cilia activity, and secretions
How does progesterone target the fallopian tubes?
Decreased contractility, cilia number, and secretions
How does estrogen target the uterus?
Increased growth of endometrium and myometrium, contractility, blood flow, and sensitivity to oxytocin
How does progesterone target the uterus?
Increased endometrial secretions
Decreased contractility and sensitivity to oxytocin
How does estrogen target the cervix?
Makes a sperm friendly mucus (alkaline, watery, abundant)
How does progesterone target the cervix?
Makes a sperm unfriendly mucus (viscous, cellular, small amount)
How does estrogen target the vagina?
Proliferation and cornification of the epithelium
How does progesterone target the vagina?
WBC infiltration, decreased cornification
How does estrogen target the breasts?
Increased duct growth, fat deposition, and size and pigmentation of the areola
How does progesterone target the breasts?
Increased alveolar growth
What is fertilization?
The process by which the male and female gametes fuse to form a viable zygote
What is a zygote?
A fertilized egg cell that results from the union of a female gamete, an egg or an ovum, with a male gamete, sperm
What is gestation?
The length of time of intrauterine fetal development
9 months or 40 weeks
What is an embryo?
An organism during the early stages of development
first 2 months of intrauterine life
What is a fetus?
Describes a developing human from 2 months until birth
When is gestation terminated?
With the onset of parturition (childbirth)
How is the timing of fertilization limited?
Sperm is viable for about 5 days
Oocyte is viable for only 12 to 24 hours
Why are sperm not initially capable of fertilization?
They require capacitation
How do sperm move in the uterine tubes?
They swim to the uterus and uterine tube
How come only a few hundred sperm make it to the uterine tubes?
Damage due to acidic pH of the female tract
Some loss due to leakage from the cervix
Loss of energy
What is polyspermy?
An egg that has been fertilized by more than one sperm
Why is polyspermy not favoured?
Prevented to maintain the diploid chromosome number
What is a pronucleus?
A pair of gametic nuclei before their fusion leads to the formation of a nucleus of the zygote
Each parents chromosome content is surrounded by a distinct membrane
What are the events of fertilization?
Capacitation happens in the female reproductive tract
Many sperm bind to receptors on the zona pellucida and undergo the acrosome reaction
Sperm move through the zona pellucida
One sperm binds to the egg plasma membrane
Sperm in drawn into the egg, the egg completes 2nd meiotic division, the nuclei of the sperm and egg unite and the egg enzymes are inactivated for the zygote to begin embyrogenesis
The egg also releases the contents of the secretory vesicles and enzymes enter the zona pellucida to block polyspermy
What are ways we can block polyspermy?
Change in membrane potential
Release fo contents from cortical granules
Enzymes enter and harden the zona pellucida
Enzymes inactivate sperm and binding receptor
What happens to the oocyte during fertilization?
Fusion of sperm with oocyte stimulates the 2nd meiotic division
The oocyte is converted to an ovum
The sperm plasma membrane disintegrates
Chromosomes from sperm and ovum migrate to the center
DNA is replicated to make a zygote
What is a morula?
Contains many cells Zona pellucida intact Division from early cleavage to the morula is known as cell cleavage Cells at this stage are totipotent 16-32 cells Develops into the blastocyst
How are twins formed?
Division of totipotent morula cells results in identical twins
Fertilization of two oocytes results in non-identical twins
What is a blastocyst?
4-5 days after fertilization
Cells lose their totipotentiality and begin to differentiate
No zona pellucida
What is the outer cell layer of the blastocyst?
The trophoblast which will become the fetal placenta
What is the inner cell mass of the blastocyst?
Will become the embryo
What is the fluid-filled cavity of the blastocyst?
The blastocoele
What is implantation?
Happens 6-7 days after fertilization
Blastocyst anchors itself to the wall of the endometrial lining with the side containing the inner cell mass positioned against the endometrium
Sticky trophoblast cells anchor themselves onto the walls of the endometrial lining and anchor themselves
-stimulates proliferation of trophoblast which divide into two parts
What are the two parts of the divided trophoblast cells?
Syncytiotrophoblast (fused) and the cytotrophoblast
What is the syncytiotrophoblast?
Enter deep into the endometrial layer and form a syncytium where there are multiple nuclei but no cell membranes
What is the cytotrophoblast?
Layer closest to the inner cell mass and secrete the early hormones for growing the embryo
What is the decidual response?
A response of the endometrial tissue where there is the appearance of blood vessels and glycogen-secreting glands for the newly anchored or implanted embryo or blastocyst
What are the two components of the placenta?
The fetal placenta
The maternal placenta
What is the fetal placenta?
Develops from the same blastocyst that forms the fetus
What is the maternal placenta?
Develops from the maternal uterine tissue
What does the placenta contain?
Amniotic cavity filled with amniotic fluid
Amnion fused with the chorion (chorionic villi allow the transfer of material between maternal blood and the fetal blood)
Umbilical cord (two umbilical arteries carry deoxygenated blood from fetus to placenta, umbilical vein Carrie’s oxygenated blood from placenta to fetus)
What are the functions of the placenta?
A temporary endocrine gland
An exchange tissue for respiratory gases, nutrients, and waste products
Filter/immunological barrier
What are the major hormones of the placenta?
Human chorionic gonadotropin (hCG)
Human chorionic somatomammotropin (hCS) or human placental lactogen (hPL)
Progesterone
Estrogen
What is the use of hCG from the placenta?
Maintains the corpus luteum functions in early pregnancy
At 2 months, there is a sharp peak of hCG which then decreases
First hormone found in blood once pregnant?
What is the use of hPL from the placenta?
GH-like and anti-insulin actions in the mother
Helps the fetus to take up more glucose through the placenta
What is the use of progesterone from the placenta?
Decreases uterine contractions
Inhibition of LH and FSH
Growth of mammary alveolar glands
Secretes sperm unfriendly mucus
What is the use of estrogen from the placenta?
Growth of the uterus
Growth of mammary ducts
Inhibition of LH and FSH
Why must the conversion of steroid hormones occur in other tissues?
The enzymatic pathways for these conversions are not present in all of the tissue
What is parturition?
The events leading to and including the delivery of the infant
What happens during childbirth?
Weak uterine contractions develop slowly and push the fetus forwards towards the cervix
The pressure of the fetus against the cervix sends a positive message to the posterior pituitary to release oxytocin
oxytocin acts on the uterine myometrial layer, binding to the tissue and causing more contractions
Positive feedback until contractions are strong enough to push baby out
What are the hormones involved in parturition
Myometrial contractions are increased by estrogen, prostaglandins, oxytocin, and stretch from the fetus’ head pushing down on the cervix
What is cervical ripening?
Process that prepares the tissue in such a way that the cervix becomes soft, making it easier for expansion
Occurs due to prostaglandins and relaxin
What is relaxin?
A hormone that relaxes the cervix and comes from the corpus luteum
What is the mammary gland?
Contain mammary alveoli which are the site of milk production and storage
What are the mammary glands like prior to puberty?
Rudimentary ducts, few if any alveoli
What are the mammary glands like at puberty?
Ducts grow and branch out (E)
Some alveolar growth (P)
Deposition of fat around alveolar tissue
What are the mammary glands like during pregnancy and lactation?
Full development, estrogen, progesterone, prolactin and hPL are required
Prolactin is released from the anterior pituitary and promotes lactation
Oxytocin is required for milk let-down or ejection from the breast tissue
What is lactogenesis?
Process by which cells in the breast tissue start making milk
What is galactopoiesis?
Process of maintenance of lactation while the mother breast feeds
What is the alveolar structure of a mammary gland?
Alveolar epithelial cells synthesize milk
Myoepithelial cells contract to expel the milk
Have receptors for oxytocin for at the time of breast feeding or hearing the cries of the baby
What is suckling?
Suckling activates tactile receptors in the mother’s breast tissue which activates the hypothalamus and stimulates the neurosecretoy cells of the posterior pituitary to secrete oxytocin. Oxytocin causes contraction of the myoepithelial cells of the breasts and milk is ejected
What does dopamine do (Suckling)?
Inhibits prolactin secretion by the anterior pituitary cells
Activation of the hypothalamus by suckling decreases dopamine secretion
What is determined at the exact moment of fertilization?
The chromosomal or genetic sex
What is the gonadal sex?
Determined by chromosomal sex
What does the presence of SRY gene on the Y chromosome dictate?
The differentiation of bipotential gonads to become testes
What does the absence of a Y chromosome dictate?
The differentiation of bipotential gonads to become ovaries by default
What does the presence of more than one X chromosome do?
Impairs spermatogenesis
What is Klinefelter’s syndrome?
XXY
Infertile
What is Turner’s syndrome?
Lack of X chromosome leads to Turner’s syndrome
Streak ovaries = flattened structure
What is genital or phenotypic sex?
Dictated by factors produced by the gonads
What happens during sexual differentiation in males?
Testes secrete Mullerian inhibiting hormones (MIH) from Sertoli cells
MIH causes regression of the Mullerian duct
Testes secrete testosterone from Leydig cells
Testosterone causes development of male internal genitalia
Testosterone is converted into DHT which causes masculinization of male external genitalia
What happens during sexual differentiation in females?
In the absence of MIH, the mullerian duct grows into female internal genitalia
Absence of testosterone prevents the development of Wolffian duct
Absence of DHT prevents the masculinization of external genitalia
Happens by default
What do the Wolffian ducts transform into?
The epididymis, vas deferens, seminal vesicles, and the ejaculatory duct
What does DHT support the development of?
The penis, scrotum, and prostate
What do the Mullerian ducts transform into?
The uterus, fallopian tubes, inner vagina
What does the absence of DHT support the development of?
The outer vagina and the female external genitalia
What is congenital adrenal hyperplasia?
Genetically female but the phenotype is male
There is a problem with the adrenal steroid secretory pathway
Too much androgen production in the fetal stage causes the development of the male external appearance
Infertile
What is the pathway for congenital adrenal hyperplasia?
Decreased cortisol causes increased ACTH which produces adrenal androgens and causes the mascularization of external genitalia
What is androgen insensitivity syndrome?
Genetically male but phenotypically female
Female and male internal structures do not develop
Body is female-like: breasts develop
Androgens are converted to estrogen in target tissues
Infertile
What is puberty?
A period of time in which a child becomes sexually mature
What triggers the onset of puberty?
Increased secretion of GnRh results in more LH and FSH secreted from the anterior pituitary which causes more sex steroids to be released from the gonads
What alters GnRH secretion at certain times?
Genetic influences
Environmental influences
What are female physical changes during puberty?
Breast development, sexual hair growth, general growth spurt, first menstruation (menarche)
What are male physical changes during puberty?
Growth of testes and penis, sexual hair growth, general growth spurt, facial hair, voice changes
What is the hypothalamic-pituitary-gonadal axis in a prepubertal child
The axis is dormant because centres in the hypothalamus are suppressed
At this stage, low levels of sex steroids provide a strong negative feedback to keep the higher centres suppressed
What is the hypothalamic-pituitary-gonadal axis at the time of puberty?
During puberty the hypothalamic area begins to come out of the central suppression
The hypothalamus begins to generate high frequency, pulsatile secretion of GnRH
What is kisspeptin?
A neuropeptide that acts on the cells that release GnRH in the hypothalamus
A cue triggers changes in the cells that cause the production of kisspeptin at the time of puberty
What is adipose tissue?
A source of the hormone leptin
Leptin acts in the hypothalamus on the cells which release kisspeptin
Important for regulating the pulse generator
What is andropause?
Happens in males
Starts 40 onwards
Lowering of the male hormone
What is menopause?
In females
Reproductive status comes to a halt
What are the hormonal changes during menopause?
Follicular depletion occurs throughout life by apoptosis
Decreased follicle numbers and decreased responsiveness to gonadotrophs cause decreased estrogen and decreased inhibin
Ovulation ceases
Decreased progesterone because no corpus luteum
Decreased estrogen, inhibin, and progesterone removes negative feedback inhibition so FSH and LH levels increase
