Chapter 28 - Reproductive System Flashcards
What is sexual reproduction?
The process by which organisms produce offspring by making germ cells (gametes)
What two things come together during fertilization?
A male gamete (sperm cell) and a female gamete (secondary oocyte)
What are the names of the gonads in males and females?
What is their function?
Testes in males
Ovaries in females
- produce gametes and secrete sex hormones
What is the function of accessory sex glands?
Produce substances that protect the gametes and facilitate their movement
What organs are included in the male reproductive system?
Testes
System of ducts: epididymis, ductus deferens, ejaculatory ducts, urethra
Accessory sex glands: seminal vesicles, prostate, bulbourethral glands
Supporting structures: scrotum and penis
What is the scrotum?
What does it consist of?
The supporting structure for the testes
- consists of loose skin
- hangs from the root of the penis
What is the raphe?
Median ridge of the scrotum
What is the scrotal septum?
Internally divides the scrotum into two sacs
- each containing a single testis
What is dartos muscle?
Muscle tissue in the subcutaneous layer of the scrotum
What is the cremaster muscle?
The muscle of the spermatic cord, by which the testicle can be partially raised
What regulates the temperature of the testes?
Location of the scrotum and the contraction of its muscle fibres
- cold temps = cremaster and dartos muscles contract
- warm temps = cremaster and dartos muscles relax
At what temperature does normal sperm production occur?
Requires to be 2-3 degrees cooler than body temperature
What is the function of the testes?
Produce sperm and secrete hormones (testosterone)
What does the tunica vaginalis cover?
Partially covers the testes
- forms during the descent of the testes
What is the tunica albuginea?
White fibrous capsule that covers the testes
- composed of dense irregular connective tissue
- extends inward
- forms the septa that divide the testis into lobules
What are lobules of the testes?
Series of internal compartments
- approx 200-300 lobules per testis
What is contained within the lobules of the testes?
Contains 1-3 tightly coiled tubules
- seminiferous tubules
What happens inside seminiferous tubules?
Sperm is produced
What is spermatogensis?
Process by which seminiferous tubules produce sperm
What two kinds of cells are found within seminiferous tubules?
- Spermatogenic cells - sperm-forming cells
2. Sertolic cells - support spermatogensis
What are spermatogonium (spermatogonia)?
Stem cells
- a cell produced at an early stage in the formation of spermatozoa
What is a spermatozoon?
A sperm cell
What is the function of the blood-testis barrier?
Protects the developing sperm cells from an immune response
- the immune system detects surface antigens on sperm as “foreign”
Where are Leydig (insterstitial) cells located and what do they do?
Located between adjacent seminiferous tubules
- secrete testosterone
What is an androgen?
A hormone that promotes the development of masculine characteristics (testosterone is an androgen)
How many days does spermatogensis take?
65-75 days
What do spermatogonia differentiate into?
Primary spermatocytes (diploid, 2n) - they still have 46 chromosomes
What happens to a primary spermatocyte after it forms?
It undergoes meiosis I
- forms secondary spermatocytes (haploid, n)
(only has 23 chromosomes)
What happens to secondary spermatocytes after they form?
Ungergoes meiosis II
- results in 4 HAPLOID cells called spermatids
How many spermatids will a SINGLE primary spermatocyte produce?
4
What is spermiogenesis?
Development of haploid spermatids into sperm
- each spermatid becomes a single sperm
- spherical spermatids transform into elongated, slender sperm
What are the main parts of a sperm cell?
Head - contains the nucleus (23 chromosomes)
Tail (neck, middle piece, principal piece, end piece)
What is an acrosome?
A cap-like vesicle covering the front 2/3 of the nucleus
- filled with enzymes that help a sperm to penetrate a secondary oocyte to bring about fertilization
What does the middle piece of a sperm tail contain?
Mitochondria
- provide energy for locomotion and for sperm metabolism
What is the function of GnRH in relation to the male reproductive system?
Gonadotropin-releasing hormone
- stimulates the secretion of two gonadotropins (luteinizing hormone and follicle stimulating hormone)
What effect does LH (luteinizing hormone) have on the male reproductive system?
Stimulates Leydig cells (located between seminiferous tubules) to secrete testosterone
- through negative feedback, testosterone suppresses the secretion of LH
What effect does FSH (follicle stimulating hormone) have on the male reproductive system?
Indirectly stimulates spermatogenesis
- FSH and testosterone act synergistically on the sertoli cells to stimulate secretion of androgen-binding protein (ABP)
What does ABP do? (androgen-binding protein)
Binds to testosterone
- keeping its concentration high
What does testosterone do in spermatogenesis?
Finalizes the final steps
How does inhibin come into play with regards to the male reproductive system?
Sertoli cells release inhibin
- inhibits the release of FSH
- if spermatogenesis is proceeding too slowly, less inhibin is released which allows more FSH secretion
What are the effects of androgens?
- prenatal development
- development of male sexual characteristics
- development of sexual function
- stimulation of anabolism
How do sperm move along the lumen of the semiiniferous tubules and then into the straight tubules?
By pressure generated by the fluid secreted by sertoli cells
After leaving the seminiferous tubules, where do the sperm go to next? (until they reach the ductus epididymis)
Seminiferous tubules –> Straight tubules –> Rete testis –> Efferent ducts –> Ductus Epididymis
What is the function of the epididymis?
Site of sperm maturation
- takes about 14 days
- also helps to propel sperm into ductus (vas) deferens during sexual arousal
- stores sperm
What happens to sperm during sperm maturation?
Process by which sperm acquire motility and the ability to fertilize an ovum
What is the ductus deferens (vas deferens)?
The duct that conveys sperm from the testicle to the urethra
What is the function of the spermatic cord?
Supporting structure that ascends out of the scrotum
- consists of ductus (vas) deferens, testicular artery, veins that drains the testes, autonomic nerves, lymphathic vessels and the cremaster muscle
What forms the ejaculatory duct?
Formed by the union of the duct from the seminal vesicle and the ampulla of the ductus (vas) deferens
What does the urethra serve as a passage way for?
Urine and semen
- subdivided into three parts.
What are the three parts of the male urethra?
- Prostatic urethra - passes through the prostrate
- Membranous urethra - passes through the corpus spongiosum of the penis
- Spongy (penial) urethra
- ends at the external urethral orifice
What do the accessory sex glands include?
Seminal vesicles, the prostrate, and the bulbourethral glands
What do the seminal vesicles secrete?
Secrete an alkaline, viscous fluid that contains fructose, prostagladins and clotting proteins.
- neurtalize acidic environments (female tract and male urethra)
- fructose is used for ATP production
- prostaglandins contribute to sperm motility and viability
- clotting proteins help semen coagulate after ejaculation
What does the prostrate secrete?
A milky, slightly acidic fluid that contains citric acid (used for ATP), proteolytic enyzmes (break down the clotting proteins from seminal vesicles), acid phosphate (unknown function) and seminalplasmin (antibiotic, destroys bacteria).
What do the Cowper’s glands secrete? (bulbourethral glands)
Secrete an alkaline fluid into the urethra that protects the passing sperm by neutralizing acids from urine in the urethra.
- also secrete a mucus that lubricates the end of the penis, decreasing the number of sperm damaged during ejaculation
What is semen?
Mixture of sperm and seminal fluid
- secretion from seminal vesicles, prostate, Cowper’s glands
Is semen slightly acidic or basic? Why?
BASIC!
- counteracts the acidity of the female tract and the male urethra
What is the function of the penis?
Passageway for the ejaculation of semen and the excretion of urine
What three cylindrical masses of tissue that make up the penis?
- Corpora cavernosa penis (x2)
2. Corpus spongiosum penis - keeps it open during ejaculation
What is erectile tissue composed of?
Numerous blood sinuses, lined by endothelial cells and surrounded by smooth muscle and elastic connective tissue
What is the glans penis?
The distal end of the penis
- slightly enlarged
What is the external urethral orifice?
The terminal slit-like opening of the urethra
What is prepuce or foreskin?
Loose fitting skin covering the glans penis
- uncircumcised
What is an erection?
The enlargement and stiffening of the penis
- parasympathetic fibers produce and release NO (vasodilator)
- allows blood vessels to dilate
What helps maintain an erection?
The expansion of the blood sinuses compress the veins that drains the penis
- slowing blood outflow
What is ejaculation?
The powerful release of semen from the urethra to the exterior
- sympathetic reflex
- urinary bladder sphincter closes (no pee!)
What is emission?
The discharge of a small volume of semen before ejaculation
- may also occur during sleep
How does a penis return to the flaccid state?
Arterioles supplying the erectile tissue of the penis constrict and the smooth muscle contracts, making blood sinuses smaller
- relieves pressure on the veins, allows them to drain
What are the organs of the female reproductive system?
Ovaries, uterine (fallopian tubes), uterus, vagina, external organs
What are the ovaries?
What do they produce?
The female gonads
- produce gametes
- produce hormones
What is the tunica albuginea?
A whitish capsule of dense irregular connective tissue located immediately deep to the germinal epithelium
What do ovarian follicles consist of?
Oocytes (in various stages of development) and the cells surrounding them
What are follicular cells?
What is their function?
Surrounding cells (in a single layer) in the ovarian follicles - nourish the developing oocyte and begin to secrete estrogens as the follicle grows larger
What are granulosa cells?
Follicular cells that have developed further
- form several layers
What is a mature (graafian) follicle?
A large, fluid-filled follicle that is ready to rupture and expel its secondary oocyte
- process known as ovulation
What is ovulation?
Process whereby a mature ovarian follicle (part of the ovary) discharges an egg (also known as an ovum, oocyte, or female gamete)
What does the corpus luteum contain?
What doe it produce?
Contains the remnants of a mature follicle after ovulation
- produces progesterone, estrogens, relaxin, and inhibin
What is corpus albicans?
Fibrous scar tissue leftover from the corpus luteum
What is oogenesis?
Formation of gametes in the ovaries
- begins in females before they are born