Reproductive System Flashcards
How do humans start off life?
- bipotential (ability to form male or female reproductive tract)
What is sexual reproduction?
- involves fusion of gametes from two parents resulting in genetic variation among offspring
Why is sexual reproduction necessary?
- creates genetic variation among a species/offspring
- enhances reproductive success in changing environments
- allows for variety of phenotypes
- genetic variation is needed to survive new pathogens and environments-> diversity driven by ability to survive disease
What makes up the reproductive system in humans?
-gonads
- series of ducts for delivery of gametes and structures for copulation
What are gonads?
- primary sex organs that produce gametes and secrete hormones
- male gonad (testes) produce sperm
- female gonad (ovaries) produce ova (eggs)
What determines who is “named” male or female in a species?
- based on size of gametes
- Females have larger gamete
- Males have more gametes
What are the primary structures of the male reproductive system?
- Testes
- Duct system (epididymis, vas deferens, urethra)
- Accessory glands (seminal vesicles, prostate, bulbourethral glands)
- External genitalia (penis, scrotum)
What structures of the male reproductive system are shared with the urinary system?
- Accessory glands: seminal vesicles, prostate, bulbourethral glands
What are the coverings of the testes
- tunica albuginea (capsule surrounding each testis)
- septa (extensions of the capsule that extend into the testis + divide it into lobules)
Describe a lobule of the testes
- Each contains 1-4 seminiferous tubules (tightly coiled structures, function as sperm-forming factories, empty sperm into rete testis)
- Sperm travel through rete testis to epididymis
What are Leydig (interstitial) cells>
- cells in the seminiferous tubules that produce androgens (generic term for sex hormone) such as testosterone + DHT (supercharged testosterone)
What are the Ductus (Vas) Deferens?
- Carry sperm from epididymis to ejaculatory duct
- Passes through inguinal canal + over bladder
- Moves sperm by peristalsis (rhythmic cmooth muscle contractions)
- Spermatic cord includes ductus deferens, blood vessels, nerves in CT sheath
- Ends in ejeculatory duct which unites with urethra
- Expanded end is the ampulla
When does ejaculation occur?
- When smooth muscle in walls of ductus deferens create peristaltic waves to squeeze sperm forward
What is a vasectomy?
- Occurs by cutting/cauterizing ductus deferens at testes to prevent transportation of sperm through ejeculatory duct
- Sperm is reabsorbed into tissue instead
What is the structure and function of the male urethra?
-Extends from base of urinary bladder to tip of penis
- Carries both urine + sperm
- Sperm enters from ejaculatory duct
- Regions of urethra: Prostatic urethra (surrounded by prostate); Membranous urethra (runs from prostatic urethra to penis); Spongy (penile) urethra (runs length of penis)
What is semen?
- Mixture of sperm + accessory gland secretions from bulbourethral glands, seminal vesicles, and prostate
What are the bulbourethral glands?
- pea-sized glands inferior to prostate
- produce thick, clear mucus known as pre-ejaculate (cleanses urethra of acidic urine, serves as lubricant during sexual intercourse, secreted into penile urethra)
What are the seminal vesicles?
- Located at base of bladder
- Produces thick, alkaline, yellowish secretion (60% of semen):
- fructose to provide energy for ATP synthesis (neeeded for sperm to swim to egg)
- Vitamin C (potent antioxidant to prevent damage from cellular respiration)
- Prostaglandins to promote smooth muscle contraction
- Other substances that nourish + activate sperm in the oviducts
What is the prostate?
- Encircles upper part of urethra
- Secretes milky fluid (helps activate sperm + enters urethra through several small ducts)
What can occur when the prostate is enlarged?
- Can pinch urethra shut which can cause a need for frequent urination due to urine build up in the bladder
What is the scrotum?
- Part of male external genitalia
- Divided sac of skin outside abdomen
- maintains testes at ~3 degrees C lower than normal body temp to protect sperm viability
- Can be used for heat-based contraception (stick testicles in boiling water to stop sperm from forming)
What is the penis?
- Delivers sperm into female reproductive tract
- Regions of penis:
- Shaft
- Glans penis (enlarged tip)
- Prepuce (foreskin)- folded cuff of skin around proximal end that may be removed by circumcision
What are descending testes?
- testes usually descend before birth around 32-36 weeks through the inguinal canal and end up in the scrotum (testes usually develop in abdomen)
- Undescended testes can occur in premature boys + can be corrected with surgery
Describe the internal structure of the penis
- 3 areas of spongy erectile tissue around urethra (no baculum- penile bone)
- Erections occur when erectile tissue fills with blood during sexual excitement- run by parasympathetic NS
- Ejaculation driven by sympathetic NS input
What is spermatogenesis?
- The production of sperm cells
- Main function: Reduce number of chromosomes so offspring total is 46 not 92
- Begins at puberty and continues throughout life
- Occurs in seminiferous tubules
-Spermatogonia undergo rapid mitosis to produce more stem cells before puberty
What are the most important horomones of the testes? How are they produced?
Testosterone and DHT
- Produced by Leydig cells
- Luteinizing hormone (LH) activates Leydig cells when signaled by Gonadotropin hormone-releasing hormone (GnRH) from hypothalymus
- causes Leydig cells to produce testosterone
What are the functions of testosterone?
- Stimulate reproductive organ development
- Underlies sex drive
- Causes secondary sex characteristics (deepening of voice; increased hair growth; enlargment of skeletal muscles; thickening of bones)
What does exogenous testosterone do?
- Causes testes to shrink bc Leydig cells stop producing because there is already testosterone from steroid use
How are testosterone, FSH, and LH involved in reducing chromosome number in spermatogenesis?
- Testosterone + FSH directly modulate spermatogonia division
- LH regulates testosterone production (1 cell type produced is stem cell called type A daughter cell; other cell type produced becomes primary spermatocyte called type B daughter cell)
Describe the process of spermatogenesis
- Primary spermatocytes undergo meiosis
- One primary spermatocyte produces four haploid spermatids
- Spermatids have 23 chromosomes
- Late spermatids produced with distinct regions: head, midpiece, tail
- Sperm cells result after maturing of spermatids
- Spermatogenesis takes ~65 days
How is spermatogenesis regulated?
- Regulated by inhibin
- Inhibin secreted from Sertoli cells in seminiferous tubules inside the testes
- Testosterone + DHT stimulate inhibin production (helps locally regulate spermatogenesis)
- Testosterone, progesterone, estrogen synthesized from cholesterol + need carrier
Describe the anatomy of a mature sperm cell
- Only human flagellated cell
- Head (contains DNA, acrosome is a “helmet” protecting nucleus)
- Midpiece (contains mitochondria for ATP generation)
- Tail (allows for motion)
What is the purpose of follicles in the female reproductive system?
- Nurture eggs + produce sex hormones
- Located on the ovaries
What is the purpose of an orgasm?
- To cause an association between reproduction and pleasure
What is an ovary?
- Primary sex organ in females
- Composed of ovarian follicles (each follicle consists of a primary oocyte + follicular cells that surround oocyte)
What are the uterine tubes?
- Receive ovulated oocyte
- Procide site for fertilization
- attach to uterus
- little-no contact between ovaries + uterine tuves
- Supported + enclosed by broad ligament
What is the uterus?
- Hollow organ
- Located between urinary bladder + rectum
- Functions of uterus: Retain, receive, + nourish fertilized egg
What is the vagina?
-Part of the birth canal
What are fimbiae?
- Finger-like projections at distal end of uterine tube that receive oocyte from ovary
What are cilia?
- Located inside uterine tube + slowly move oocyte towards uterus (takes 3-4 days)
Where does fertilization occur?
- inside uterine tube since oocyte lives ~24 hours
What are the regions of the uterus?
- body = main potion
- fundus = superior rounded region above where uterine tube enters
- cervix = narrow outlet that protrudes into vagina
What are the three walls of the uterus and their purposes?
- Endometrium- inner layer (allows for implantation of a fertilized egg; sloughs off if no pregnancy occurs (mestruation))
- Myometrium- middle layer made of smooth muscle
- Perimetrium (visceral layer)- outermost serous layer
What is the mons pubis?
- fatty area overlying the pubic symphysis
- covered with the pubic hair after puberty
What is the labia?
- Skin folds
- Labia majora: hair-covered skin folds
- labia minora: dilicate, hair-free
What are the 3 orifices of the external genitalia?
1) Urethral orifice- pee
2) Vaginal orifice- reproduction
3) the anus
What are the greater vestibular glands?
- Bartholin’s glands
- Secrete fluid that helps lubricate the vagina
What is the vagina?
- Extends from cervix to exterior of body
- Located between bladder + rectum
- Serves as birth canal + receives penis during intercourse
- hymen partially closes vagina until ruptured
What is the clitoris?
- Contains erectile tissue
- Corresponds to the male penis
- Hooded by a prepuce composed of sensitive erectile tissue + becomes swollen with blood during sexual excitement