MCAT BIO CH. 13 PART 1 Flashcards
What is the role of the scrotum, in males?
Temperature regulation
Why are the testes located outside of the body, in males?
Sperm synthesis must occur at a few degrees below normal body temperature
What are the two roles of the testes, in males?
- Synthesis of sperm
2. Secretion of male sex hormones
What is an example of a male sex hormone, in males?
Androgen
What is the site of spermatogenesis, in males?
Seminiferous tubules
What are the walls of the seminiferous tubules made out of, in males?
Sustentacular cells - Sertoli cells
What is the general role of the sustentacular cells,in males?
Protect and nurture the developing sperm
The tissue between the seminiferous tubules is what, in males?
Testicular interstitium
What are interstitial cells and where are they found, in males?
Response for androgen synthesis and coated in testiular interstitium
What are Leydig cells, in males?
Interstitial cells
What are interstitial cells responsible for, in males?
For androgen (testosterone) synthesis
What does the seminiferous tubules empty into, in males?
The epididymis
What is the epididymis and where is it located, in males?
Located on the posterior of each testicle
What does the epididymis empty into, in males?
The ductus deferens
What is the ductus deference and what does it turn into, in males?
Vas deferens; leads to the urethra
To get to the urethra, the ductus deferens leaves what, in males?
Leaves the scrotum and enters the inguinal canal
What is the inguinal canal, in males?
The inguinal canal is a gunnel that travels along the body wall toward the crest of the hip bone
How many inguinal canal is there, in males?
Two; left and right
From the inguinal canal, the ductus deferens enters, in males?
Enters the pelvic cavity
What does the pelvic cavity join into and to form what, in males?
Joins the duct of the seminal vesicle to form the ejaculatory duct
What does the ejaculatory duct join from both sides of the body, in males?
The urethra
What is the seminal vesicles located, in males?
Posterior surface of the bladder
What do the seminal vesicle secrete and where, in males?
60% of the total volume of the semen into the ejaculatory duct
What glands produces semen, in males?
Seminal vesicles, prostate, and the bulbourethral glands
What is the use of semen for the sperm, in males?
Nourishing fluid for the sperm
What is the name for the three glands that produce semen, in males?
Accessory glands
What does the ejaculatory duct empties into, in males?
The urethra as it passes through the prostate gland
Where does the bulbourethral contribute to the semen production, in males?
Near the beginning of the urethra
What percentage of the total volume of semen does the prostrate gland contribute, in males?
35%
What is the purpose of the prostate gland, in males?
Nourishment and allow semen to coagulate after ejaculation
What percentage of the total volume of semen does the bulbourethral gland contribute, in males?
3%
What is the purpose of the bulbourethral gland, in males?
Lubricate urethra, neutralize acids in male urethra and female vagina
WWhat percentage of the total volume of semen does the testes contribute, in males?
2%
What is the purpose of the testes based on semen, in males?
Male gamete
What allows erection in the penis, in males?
Specialized erectile tissue
What is the erectile tissue composed of, in males?
Modified veins and capillaries surrounded by a connective tissue sheath
When does erection occur based on the erectile tissue’s functionality, in males?
When blood accumulates at high pressure in the erectile tissue
What are the there compartments the contain erectile tissue, in males?
Corpora cavernosa (two of these) and the corpus songiosum
What are the three stages of male sexual act, in males?
Arousal, orgasm and resolution
The three stages of the male sexual act, what are they controlled by, in males?
An integrating center in the spinal cord which responds to physical stimulation and input from the brain
How can the cerebral cortex affect the integrating enter, in males?
Activate or inhibit
What type of nervous system is arousal dependent on, in males?
Parasympathetic nervous input
What are the two stages of arousal, in males?
Erection and lubrication
Based on the two stages of arousal, what is erection, in males?
Dilation of arteries supplying the erectile tissue
What happens during erection when arteries begin to dilate, in males?
Causes swelling which in turn obstructs venous outflow
Based on the two stages of arousal, what is lubrication, in males?
The bulbourehtral glands secrete a viscous mucous which saves as a lubricant
What type of nervous system is lubrication dependent on, in males?
Parasympathetic system
Which nervous system is required to be stimulated for orgasm, in males?
The sympathetic nervous system
What are the two stages of orgasm stimulation from the sympathetic nervous system, in males?
- Emission
2. Ejaculation
What is emission, based on orgasm, in males?
Propulsion of sperm from the ductus deferens and semen from the accessory glands into the urethra
How does mission cause propulsion of sperm, in males?
By contractions of the smooth muscle surrounding these organs
What is emission followed by, in males?
Ejaculation
What happens during ejaculation in males?
Semen is propelled out of the urethra
In males, during ejaculation, semen is propelled out of the urethra by what?
By rhythmic contractions of muscles surrounding the base of the penis
What type of reaction is ejaculation considered?
Reflex reaction caused by the presence of semen in the urethra
What constitutes of the male orgasm?
Emission and ejaculation together
What is resolution based on male orgasm?
Return to a normal unstimulated state
What is resolution controlled by, based on male orgasm?
Sympathetic nervous system
What is resolution of male orgasm caused by?
Constricting the erectile arteries
What happens when the erectile arteries are constricted based on male orgasm?
Deceased blood flow to the erectile tissue and allows the veins to carry away the trapped blood
What is the difference between emission and ejaculation?
Emission: Movement of sperm and semen components into the urethra
Ejaculation: Movement of semen from the urethra out of the body
What processes in a human being involve meiosis?
Gametogenesis
What is produced through meiosis?
Haploid gamaetes
The gametes produced by male during meiosis are know as…?
Spermatozoa or sperm
The gametes produced by female during meiosis are know as…?
Ova or egg
What is the fusion of the egg and sperm called?
Syngamy
What is the result of syngamy?
Zygote
The female gamete contributes more of the genome of the zygote than the male. T/F
False: gametes produced by males and females contribute EQUALLY to the genome of the zygote
When does the gametes produced by males and females not contribute equally?
Special case of the two different sex chromosomes X and Y giving rise to male offspring
Although both gametes contribute equally to the genome…..finish the sentence
The egg provides every other part of the zygote since the only part of the sperm which enters the egg is haploid genome
What is sperm synthesis called?
Spermatogenesis
When does spermatogenesis begin?
At puberty and occurs in the testes throughout adult life
What is the site of spermatogenesis?
The seminiferous tubules
What aids the seminiferous tubules through spermatogenesis?
The sustentacular cells found in the wall of the seminiferous tubules
Where are immature sperm precursors found?
In the outer wall of the tubule
Where are matured spermatozoa deposited?
In the lumen
What happens to the sperm once they are deposited into the lumen?
Transported to the epididymis
What are the cells that give rise to the spermatogonia and the oogonia?
Germ cells
What is the purpose of the spermatogonium?
Mitosis, replicate DNA in S phase
What does the primary spermatocyte undergo?
Meiosis I
What does the secondary spermatocyte undergo?
Meiosis 2
What is the role of the spermatid?
Immature sperm; turn in spermatozoan
What is the role of the spermatozoan?
Finish maturing; in seminiferous tubule and in epididymis
The final stages of sperm maturation occurs where?
In the epididymis
The spermatozoan can utilize motility upon entry into the epididymis. T/F
False: incapable of motility
When do spermatozoan become fully capable of motility?
When they reach the ductus deferens
What is the benefit of spermatozoan being incapable of motility until ductus deferens?
Very low metabolic rate that allows them to conserve energy and remain fertile during storage in the ductus defense
How does the shape of the spermatid change in order to become a sperm?
Dna condenses, cytoplasm shrinks, head and tail of flagellum forms
What is located on the tail of the sperm?
Base of the tail contains many mitochondria
Where does the mitochondrial in the tail of the sperm get their energy?
From the fructose which the seminal vesicles contribute to the semen and from vaginal secretions
What is the acrosome?
A compartment on the head of the sperm that contains hydrolytic enzymes
Why do the acrosome contain hydrolytic enzymes?
Required for penetration of the ovum’s protective layer
What is bindin?
A protein on the sperm’s surface
What is bindin protein?
Attaches to receptors on the zona pellucida surrounding the ovum
What are the main hormones that help control spermatogenesis?
- Testosterone
- Luteinizing hormone
- Follicle stimulating hormone
- Inhibin
What is the role of testosterone in spermatogenesis?
Plays the essential role of stimulating division of spermatogonia
What is the role of luteinizing hormone in spermatogenesis?
Stimulates interstitial cells to secrete testosterone
What is the role of follicle stimulating hormone in spermatogenesis?
Stimulates the sustenacular cells
What is the role of inhibin hormone in spermatogenesis?
Secreted by sustenacular to inhibit follicle stimulating hormone
From where are FSH and LH spermatogenesis hormone released? Why should they sometimes be inhibited?
Gonadtropins secreted by the anterior pituitary; provide negative feedback
What do the undifferentiated gonads possess that can develop into male?
Wolffian ducts
What do the undifferentiated gonads possess that can develop into female?
Mullerian ducts
What happens to undifferentiated gonads in the absence of a Y chromosome?
Mullerian duct development occurs by default and female internal genitalia result
The external female genitalia result from mullerian duct development. T/F
False: not derived from the Mullerian ducts
What happens when the Y chromosome leads to development of male internal and external genitalia; which hormones are produced?
Testosterone an Mullerian inhibiting factor (MIF)
What produces Mulliran inhibit factor and what does it cause and prevent?
Testes; regression of Mullerian duct, prevents development of female internal genitalia
When does testosterone secretion begin?
Around week 7 of gestation
When are the testes formed based on gestation?
Week 9
What supplies testosterone in gestation?
Interstitial cells
What happens to the testosterone responsible for the development of male external genitalia?
Enters the systemic circulation and must be converted to dihydrotestosterone in target tissues to exert its effect
What are the three main fetal precursors of the reproductive organs?
Wolffan ducts, Mullerian ducts and gonads
What happens to the Wolffian ducts during female development?
They disappear in female reproductive system
What happens for the Mullerian ducts during male development?
Disappear
Why are female and male structures considered analogous?
Because they arise from different precursors
What are testes and ovaries considered in relation to development and why?
Homologous organs because they are derived from the same undeveloped structures
Based on the testis, what is this homologous organ in female and what is the function?
Ovary; gamete and hormone reproduction
Based on the penis, what is this homologous organ in female and what is the function?
Clitoris; erectile tissue and sensation
Based on the bulbourethral gland, what is this homologous organ in female and what is the function?
Greater vestibular glands; lubrication
Based on the scrotum, what is this homologous organ in female and what is the function?
Labia majora, external skin folds
What are androgens?
All hormones involved in the development and maintenance of male characteristics
What are estrogen?
All hormones involved in development and maintenance of female characteristics
What is the primary estrogen produced in ovaries?
Estradiol
Elevated levels of testosterone are responsible for the development and maintenance of male……(based on puberty and adult life) ?
Secondary sexual characteristics
What results from the maintenance of secondary sexual characteristics done by testosterone?
Pubertal growth spurt and fusion of the epiphyses
The role of estrogen in the female is________to the role of testosterone in the male.
Analogous
What is estrogen required for at the beginning of puberty for females?
- Regulate the uterine cycle
2. Development and maintenance of female secondary sexual characteristics
What causes the fusion of epiphyses in females?
Estrogen
What is sex steroid production controlled by and by which hormone?
The hypothalamus and the anterior pituitary; gonadotropin releasing hormone
Where is the gonadotropin releasing hormone found?
In hypothalamus
What does the gonadotropin releases hormones stimulate?
Stimulates the pituitary to release the gonadotropins
What do the gonadotropins release based on pituitary stimulation?
- Follicle-stimulating hormone (FSH)
2. Luteinizing hormone (LH)
What does the LH stimulate in men?
The luteinizing hormone acts in interstitial cells to stimulate testosterone production
What does the FSH stimulate in men?
The follicle-stimulating hormone stimulates the sustenacular cells
What does the LH stimulate in women?
The luteinizing hormone stimulates the formation of the corpus lute and progesterone secretion
What does the FSH stimulate in women?
Stimulates the granulose cells to secrete estrogen
What does feedback inhibition by the steroids based on androgens and estrogens?
Inhibits the production of GnRH, LH and FSH
What cells produce inhibin based on estrogen and androgen?
Produced by sustenacular cells and the granulosa cells
What type of feedback does inhibin provide?
Provides further feedback regulation of FSH production
Why are the structures of female and male genitalia considered homologous?
Derived from a common undifferentiated precursor
When there is the undifferentiated precursor, what does the testosterone cause to happen during male formation?
Causes a pair of skin folds known as labioscrotal swellings to grow and fuse, forming the scrotum
When there is the undifferentiated precursor, the lack of testosterone causes what to happen during female formation?
The labioscrotal swellings form the labia majora of the vagina
The structure that becomes the clitoris in the female is located where?
Located within the labia majora in the uppermost part of the vulva
What is the name of the body part in female where the urine exists the body?
Urethral opening
What surrounds the urethral opening?
Another pair of skin folds called the labia minora
Why doesn’t the female internal genitalia have no homologous structures in the males?
Because female internal genitalia are derived from the Mullerian ducts
What is the cervix?
The part of the uterus which opens into the vagina
What is the endometrium and what is it responsible for?
Innermost lining of the uterus; responsible for nourishment and menstrual bleeding
What surrounded the endometrium of the uterus?
Myometrium
What is the myometrium?
A thick layer of smooth muscle comprising the wall of the uterus
What does the uterus end into?
Two uterine tubes of finger-like structures called fimbriae
What does the fimbriae brush ups gainst?
The ovary
Is estrogen production by the ovaries required for the development of the uterine tubes and uterus?
No, the Mullerian ducts develop into vaagina, uterus and uterine tubes by default as long as MIF is absent
What are the stages of the female sexual act?
Arousal, orgasm and resolution
What parts in females contains the erectile tissue?
Clitoris and labia minora
What is lubrication provided by in female sexual act?
Greater vestibular glands and vaginal epithelium
When does oogenesis begin?
Prenatally
What do germ cells do in the ovary of a female fetus?
Divide mitotically to produce large numbers of oogonia
What is the difference between germ cells mitotic division in female and males?
Only happens in adult males
Oogonia go through all meiosis during fetus development in females T/F
False: enter first phase of meiosis and arrested in orphan I - primary oocytes
When does the number of oogonia peak?
Peaks at about 7 million at mid-gestation (20 weeks into the fetal life)
What happens when the number of oogonia is peaked?
Mitosis ceases, conversion to primary oocytes begins and progressive loss of cells to only about 2 million primary oocytes
How many oocytes are ever actually ovulated in the average women?
400
How long can primary oocytes and female stay frozen in prophase I of meiosis?
For decades, until they re-enter the meiotic cycle
What stimulates completion of the first meiotic division and ovulation in female body’s?
Hormonal changes
The first meiotic division caused by hormonal changes yields what in females?
A large secondary oocyte and a small polar body
What does a small polar body contain in females?
Half of the DNA and no cytoplasm or organelles
When does the second meiotic division occur in females?
Only if the secondary oocyte if fertilized by a sperm
What is the result of the second meiotic division in females ?
Large ovum and second polar body
What must the sperm and egg what for in order to fuse?
Wait for the secondary oocyte to release the second polar body and finish maturing to an ootid and then an ovum
Where is the primary oocyte found?
Granulosa cells, clump of sporting cells
The oocyte and the granulosa cells are called what?
Follicle
Granulosa cells assist with what?
Maturation
What is the male counterpart of granulosa cells?
Sustenacular cells
What is an immature primary oocyte surrounded by? What does it form?
Surrounded by a single layer of granulosa cells forming a primordial follicle
What is the zona pellucida?
Oocyte forms a protective layer of mucopolysaccharides
If there are several follicles in an ovary, what are they surrounded and separated by?
Thecal cells
What is the male counterpart of the thecal cells? What do they respond to?
Testicular interstitial cells, stimulated by LH
What happens to the several maturing follicles in the ovary?
One of them progresses to the point of ovulation each month and all the others degenerate
Since one of the follicles progress, what is it called based on maturating of follicles?
Graafian follicle
What happens to the Graafian follicle during ovulation?
Bursts, releasing the secondary oocyte with its zone pellucid and protective granolas cells into the Fallopian tube
What is the corona radiata?
The layer of the granulosa cells surrounding the ovum
What is the corpus luteum?
The follicular cells remaining in the ovary after ovulation form this structure
Where is estrogen made and secreted during first half of menstrual cycle?
By the granulosa cells with help from the thecal cells
What happens based on hormones during the second half of the menstrual cycle?
Both estrogen and progesterone are secreted by corpus luteum
How does estrogen exert its effect on a cell?
Cytoplasmic receptor binds estrogen and binds to specific DNA elements in promoters and enhancers to regulate transcription
What events does the menstrual cycle include?
- Ovarian cycle
2. Uterine cycle
What are the three phases of the ovarian cycle?
- Follicular phase
- Ovulatory phase
- Luteal phase
What happens during the follicular phase of the ovarian cycle?
A primary follicle matures and secretes estrogen
What controls the maturation of the follicle during the follicular phase?
The control of follicle stimulating hormone (FSH)
Where is the follicle stimulating hormone from?
From the anterior pituitary
How long does the follicular phase lasts for?
About 13 days
What happens during the ovulatory phase of the ovarian cycle?
A secondary oocyte is released from the ovary
What is the ovulatory phase, the release of the secondary oocyte, triggered by?
A surge of luteinizing hormone (LH) from the anterior pituitary
During the ovulatory phase, what causes does the surge cause?
The remnants of the follicle to become the corpus luteum
When does ovulation typically occurs?
Day 14 of the cycle
What happens during the luteal phase of the ovarian cycle?
Full formation of the corpus luteum in the ovary
What does the corpus luteum secrete based on the ovarian cycle?
Secretes both estrogen and progesterone and has a life spa of about two weeks
What is the average length of the luteal phase?
About 14 days
What is the focus of the uterine cycle?
The preparation of the endometrium for potential implantation of a fertilized egg
What are the three phases of the uterine cycle?
- Menstruation
- Proliferative phase
- Secretory phase
What is menstruation triggered by?
The degeneration of the corpus luteum and subsequent drop in estrogen and progesterone levels
After the menstruation is triggered and there’s degeneration of the corpus luteum, what happens due to the drop in hormone level?
Previous cycle’s endometrial lining to slog out of the uterus which produces the bleeding associated with this time period
How long does menstruation last for?
Menstruations lasts about 5 days
What happens during the proliferative phase of the uterine cycle?
Estrogen produced by the follicle induces the proliferation of a new endometrium
How long does proliferation phase last for?
About 9 days
What happens during the secretory phase of the uterine cycle?
Estrogen and progesterone produced by the corpus item further increase development of the endometrium
What types of secretion does he secretory phase include?
Secretion of glycogen and lipids and other materials
How long does secretory phase last for?
14 days
What hormones regulate the secretion of estrogen and progesterone from the ovary during the menstrual cycle?
Anterior pituitary and hypothalamus
What hormones regulate the vents in the uterus?
Estrogen and progesterone
What hormones are LH, FSH and GnRH?
Luteinizing hormone, follicle-stimulating hormone and gonadotropin
What hormone starts the menstrual cycle?
Gonadotropin
What is gonadotropin released from and what does it do?
From the hypothalamus and stimulates the release of FSH and LH
Where are LH and FSH released from? What do they stand for?
From the anterior pituitary and stand for luteinizing hormone and follicle-stimulating hormone
What happens under the influence of FSH that was stimulated from GnRH in the hypothalamus?
The granulosa and thecal cells develop during the follicular phase and secrete estrogen
What does the secretion of estrogen from the granulosa and thecal cells do?
Inhibits the secretion of GnRH, FSH and LH
What happens to estrogen through the follicular stage?
Increases throughout the follicular stage and reaches a threshold near the end of this case - has a positive effect on LH secretion
Near the end of the follicular stage phase, the positive effect on LH secretion from estrogen aids in what?
Sudden surge in LH causesovulation
What happens to LH after ovulation?
Induces the follicle to become the corpus luteum and to secrete estrogen and progesterone
The secretion of estrogen and progesterone after the follicle becomes the corpus luteum marks the beginning of what?
Of the secretory phase
When pregnancy doesn’t occur, what happens to ovulation that had formed?
Combined levels of estrogen and progesterone feedback to strongly inhibit secretion of GnRH, FSH and LH
What happens when LH secretion drops near the end of the secretory phase?
LH secretion drops, the corpus luteum regresses, no longer secretes estrogen or progesterone and menstruation occurs
What is the physiological reason for endometrial shedding?
Decrease in estrogen and progesterone levels which occurs as the corpus luteum degenerates
Why does the corpus luteum degenerate?
Due to a decrease in luteinizing hormone
Why does LH hormone decrease?
Feedback inhibition from the high levels of estrogen and progesterone secreted by the corpus luteum
What should be prevented during pregnancy?
Ovulation
What is doe to prevent ovulation during pregnancy?
Constant high levels of estrogen and progesterone seen during pregnancy to inhibit secretion of LH by the pituitary
No LH equals…..
No ovulation
What happens within a few days if fertilization takes place?
Embryo becomes implanted in the endometrium
When the embryo is implanted in the endometrium, what begins to develop?
The placenta
What is the chorion?
Portion of the placenta that is derived from the zygote
What does the chorion secrete?
Human chorionic gonadotropin
What does the human chorionic gonadtropin allow during the hormonal change of pregnancy ?
For corpus luteum to be maintained
What hormone is tested for pregnancy tests?
hGC because its presence absolutely confirm the presence of an embryo
What is the secondary oocyte surrounded by?
- Corona radiata
2. Zona pellucida
What is the corona radiata?
A protective layer of granulosa cells
Where is the zona pellucida located?
Located just outside the egg cell membrane
What is sperm capacitation?
Involves the dilution of inhibitory substances present in semen
During fertilization, what fuses?
Spermatozoa and secondary oocyte
What must a sperm penetrate in order to fertilize?
Corona radiata and zona pellucida
What does the sperm use in order to penetrate the two layers to fertilize?
The acrosome reaction
What is the acrosome of a sperm?
Large vesicle in the sperm head containing hydrolytic enzymes which are released by exocytosis
What happens after the corona radiata has been penetrated, what does the acrosome of the sperm completes?
The acrosome process which contains actin elongates towards the zona pellucida
What does the acrosome process contain?
Bindin, a species-specific protein which bins to receptors in the zona pellucida
What happens when the acerosome of the sperm binds to the zona pellucida?
Sperm and egg plasma membrane fuse and the sperm nucleus enters the secondary oocyte
What is polyspermy?
Penetration of an ovum by more than one per
What is polyspermy usually prevented by?
Fast block to polyspermy and slow block to polyspermy
What is fast block to polyspermy?
Depolarization of the egg plasma membrane
What is the slow block to polyspermy?
Calcium influx caused by the initial depolarization
What is the slow block also known as?
Cortical reaction
What are the two components of the cortical reaction?
- Swelling of the space between the zona pellucida & plasma membrane
- Hardening of the zona pellucida
What is the effect. of the calcium influx during the slow blow polyspermy?
Causes increased metabolism and protein synthesis, also known as egg activation
What is the first stage of fertilization?
Cleavage
What is the result of the first few cell divisions that occur?
The morula
The morula is the same size as the zygote, dividing cells spend most of their time where?
In the S and M phases, skipping the G1 and G2 phases
What stage is after the morula?
Blastocyst
What is the process of creating the blastocyst?
Blastulation
What does the blastocyst contain?
A ring of cells called the trophoblast surrounding a cavity and an inner cell mass
Where is the inner cell mass located based on the blastocyst?
Inner cell mass adhering to the inside of the trophoblast at one end of the cavity
What will the trophoblast give rise to?
The chorion (zygote’s contribution to the placenta)
What does the inner cell mass of the blastocyst become?
Become the embryo
If two inner cell masses form in the blastula, what will be the result?
Pair of identical twins sharing the same placenta
What happens to the developing blastocyst based on its location?
Reaches the uterus and burrows into the endometrium
