Jan 29 - The Reproductive System Flashcards
What is reproduction dependant on?
It depends on the union of male and female gametes to form a new individual. The male and female reproductive systems are designed to enable the union of genetic material
What are the primary reproductive organs?
The gonads. In males, they consist of a pair of testes. In females, they consist of a pair of ovaries. In a developing fetus, these are bi-potential gonads (they could go either way; testes or ovaries)
What are the functions of mature gonads?
Producing gametes (gametogenesis) -Spermatozoa (sperm) in males -Ova (eggs) in females Secreting sex hormones -Testosterone in males -Estrogen and progesterone in females
What is the reproductive tract?
A system of specialized ducts that transport or house gametes after they are produced
What are accessory sex gland?
They empty supportive secretions into reproductive tract (the female breasts are considered accessory sex organs)
What is external genitalia?
Externally visible portions of the reproductive system
What are secondary sexual characteristics?
External characteristics that are not directly involved in reproduction that distinguishes males and females (body configuration, hair distribution)
What are the male reproductive functions?
Production of sperm (spermatogenesis)
Delivery of sperm to female
What are the organs of the male reproductive system?
Testes
Accessory sex glands
Penis
Male reproductive tract
Describe the testes
They are the sperm-producing organs. They are suspended outside the abdominal tract in a skin-covered sac (scrotum)
What are the male accessory sex gland? What is their function?
They include the seminal vesicles, the prostate gland and the bulbourethral glands. Their secretions provide the bulk of semen (liquid substance that is conductive to sperm viability)
What is the function of the penis with regards to reproduction?
It is the organ used to deposit semen in the female
What makes up the male reproductive tract?
The epididymis, the ductus (vas) deferens, the ejaculatory duct, which empties into the urethra (the canal running the length of the penis that empties into the exterior
What are the functions of the female reproductive system?
Cyclical production of the ova (oogenesis)
Reception of sperm
Transport of sperm and ovum to common site for union (fertilization or conception)
Maintenance of the developing fetus until it can survive in the outside world (gestation or pregnancy)
Giving birth to the baby (parturition)
Nourishing the infant after birth by milk production (lactation)
What is the product of fertilization?
The embryo. After the first two months of intrauterine development, the embryo is known as a fetus
What are the female reproductive organs?
Oviducts
Uterus
Vagina
Vulva
Describe the oviducts
They are inclose association with the ovaries
They pick up ova on ovulation
They serve as the site for fertilization
What are the functions of the uterus?
It is responsible for maintenance of the fetus during development
It is responsible for expelling at the end of pregnancy
Describe the vagina
Muscular, expandable tube that connects the uterus to the external environment
The lower portion is called the cervix
The vaginal opening is located in the perineal region between the urethral opening and the anal opening
Partially covered by thin mucous membrane, hymen (typically disrupted by first sexual intercourse)
Labia minora and labia majora are the skin folds that surround the vaginal and urethral openings
The clitoris is a small erotic structure located at the anterior end of folds of labia minora
Describe the cervix
It is a single, small opening that serves as a pathway for sperm. It also serves as a passageway for the delivery of the baby from the uterus
What is the vulva?
A collective term for the female external genitalia
How are body cells (somatic cells) different than gametes cells?
They contain 46 chromosomes (diploid number) that can be sorted into 23 homologous pairs
Describe gametes
They have 23 chromosomes (haploid number)
They contain only one member of each homologous pair of chromosomes
How is gametogenesis accomplished?
By meiosis
What are autosomes?
22 pairs of chromosomes which code for general human characteristics and specific traits such as eye colour
What are sex chromosomes?
The remaining pair chromosomes. There are two genetically different types; the larger X chromosome and the smaller Y chromsome
Describe gametogenesis
Nuclear division in the specialized case of gametes is accomplished by meiosis. Only a half of the genetic information is distributed to each of the four new daughter cells. More than 8 million (223) different mixtures of the 23 paternal and maternal chromosomes are possible. This genetic mixing provides novel combinations of chromosomes. Crossing-over contributes even further to genetic diveristy
How is sex determined?
It depends on the combination of sex chromosomes. Genetic females have two X chromosomes. Genetic males have an X and a Y chromosome. Genetic sex is determined at the time of conception and it depends on the type of sex chromosome is contained within the fertilizing sperm
What is the function of the Y chromosome?
Responsible for all the anatomic and functional distinctions between males and females
What are the three levels of differences between males and females?
Genetic (depends on a combination of sex chromosomes at the time of conception)
Gonadal (depends on the development of testes or ovaries, which depends on the presence or absence of the Y chromosome)
Phenotypic (the apparent anatomic sex of the individual, which is determined by gonadal sex)
When does gonadal specificity begin to appear?
It appears during the seventh week of intrauterine life when the indifferent gonadal tissue of a genetic male begins to differentiate into testes under the influence of sex-determining region of the Y chromosome (SRY)
What is phenotypic sex?
The apparent anatomic sex of an individual, which depends on the genetically determined gonadal sex
What is sexual differentiation?
The term sexual differentiation refers to the embryonic development of the external genitalia and reproductive tract along either male or female lines
How does the male-type reproductive system develop?
Differentiation into a male-type reproductive system is induced by androgens, which are masculinizing hormones secreted by the developing testes
What does undifferentiated external gentials consist of?
Gential tubercle, paired urethral folds surrounding the urethral groove and more laterally, gential (labioscrotal) swellings
How is development of the reproductive tract along the male or female line determined?
It is determined by the presence or abscence of two hormones secreted by the fetal testes - testosterone and Mullerian-inhibiting factor
What does the abscence of testosterone and Mullerian-inhibiting result in?
The development into the female reproductive tract (oviducts, uterus and superior portion of the vagina) and the external genitalia to differentiate into the clitoris and labia
What does the undifferentiated reproductive system consist of?
Undifferentiated gonads at the ends of Wolffian ducts, and Mullerian ducts
How does happens to the undifferentiated reproductive system?
In the presence of testosterone and Mullerian-inhibiting factor, the Mullerian ducts degenerate and the gonads and Wolffian ducts develop into testes, the epididymis, the ductus deferens and seminal vesicles. In the abscence of these hormones, the Mullein ducts develop into the female reproductive tract (oviducts, uterus and the superior portion of the vagina) and the external genitalia differentiate into the clitoris and the labia
Where do the testes descend to? When? Why?
The testes descend into the scrotum. The descent is usually complete by the seventh month of gestation. The location provides a cooler environment essential for spermatogenesis
What are the functions of the testes?
They produce sperm, which occurs within the seminiferous tubules.
They secrete testosterone, which is produced by Leydig (interstitial) cells that lie in the connective tissue between seminiferous tubules
What is testosterone?
A steroid hormone derived from cholesterol precursor molecule
What are the 5 categories of testosterone effects?
Reproductive system before birth Sex-specific tissues after birth Other reproductive-related effects Secondary sexual characteristics Non-reproductive actions
What is the result of spermatogenesis?
It results in many highly specialized, mobile sperm
What is spermatogenesis?
A complex process by which undifferentiated diploid primordial germ cells (spermatogonia) are converted into haploid spermatozoa (sperm)
What are the three major stages of spermatogenesis?
Mitotic proliferation
Meiosis
Packaging (spermiogenesis)
Describe the mitotic proliferation stage of spermatogenesis?
Sperm-forming daughter cell divides mitotically twice more to form four identical primary spermatocytes
Describe the meiosis stage of spermatogenesis?
Each primary spermatocyte forms two secondary spermatocytes yielding four spermatids after the second meiotic division. Theoretically, sixteen spermatozoa result from each spermatogonium that goes through this process
What are the effects of testosterone before birth?
It masculinizes the reproductive tract and external genitalia.
It promotes the descent of the testes into the scrotum
What are the effects of testosterone on sex-specific tissues after birth?
It promotes growth and maturation of the reproductive system at puberty.
It is essential for spermatogenesis
It maintains the reproductive tract throughout adulthood
What are the effects of testosterone on other reproduction-related effects?
It develops the sex-drive at puberty
It controls gonadotropin hormone secretion
What are the effects of testosterone on secondary sexual characteristics?
It induces the male pattern of hair growth (e.g., beard)
It causes the voice to deepen because of the thickening of the vocal folds.
It promotes muscle growth responsible for male body configuration
What are the effects of testosterone on nonreproductive actions?
Is exerts a protein anabolic effect
It promotes bone growth at puberty
It closes the epiphyseal plates after being converted to estrogen by aromatase
It may induce aggressive behaviour
What do spermatozoa associate with throughout development?
Spermatozoa remain closely associated with Sertoli cells throughout development
What does a spermatozoan consist of?
Head
Acrosome
Midpiece
Tail
Describe a spermatozoan head
Consists primarily of the nucleus (contains DNA)
Describe the acrosome
Enzyme filled vesicle that caps the tip of the head
It is used to penetrate the ovum
It is formed by the endoplasmic reticulum and Golgi complex before these organelles are discarded
Describe the midpiece of spermatozoa
It is the area where mitochondria are concentrated
Describe the spermatozoan tail
It provides motility for the spermatozoan
Where are Sertoli cells located?
In the seminiferous tubules
What are the functions of the Sertoli cells located in the seminiferous tubules?
Form blood-testes barrier
Provides nourishment
Phagocytic function
Secretion of seminiferous tubule fluid which flushes released sperm from the tubule into the epididymis for storage and additional processing
Secretion of androgen-binding protein
Site of action to control spermatogenesis (release of inhibin; acts in a negative-feedback fashion to regulate FSH secretion)
What is the function of the epididymis and ductus deferens?
Storage and concentration of sperm
Increase of sperm motility and fertility prior to ejaculation
During ejaculation, sperm are mixed with secretions released by accessory glands (seminal vesicles, prostate, gland and bulbourethral glands)
What do the seminal vesicles provide in terms of seminal secretions?
They supply fructose for energy
They supply prostaglandins, which promotes smooth muscle motility in both male and female reproductive tracts (enhances sperm transport)
Provides more than half the semen
Secretes fibrinogen
What does the prostate gland provide in terms of seminal secretions?
It contributes alkaline fluid that neutralizes acidic vaginal secretions
Provides clotting enzymes and fibrinolysin
What do the bulbourethral glands provide in terms of seminal secretions?
They release lubricating mucus
Name the two gonadotropic hormones that control the testes
The testes are controlled by the two gonadotropic hormones secreted by the anterior pituitary, luteinizing hormone (LH) and follicle-stimulating hormone (FSH), which are named for their functions in females
How does LH affect the male reproductive system?
Testosterone is essential to maintaining spermatogenesis in the adult male, and it is under direct control of LH
What stimulates the secretion of LH and FSH?
Secretion of both LH and FSH from the anterior pituitary is stimulated in turn by a single hypothalamic hormone, gonadotropin-releasing hormone (GnRH)
How does the negative-feedback control of testosterone function?
The predominant negative-feedback effect of testosterone is to decrease GnRH release by acting on the hypothalamus, thus directly decreasing both LH and FSH release by the anterior pituitary
What are the actions of prostaglandins on the reproductive system?
It promotes sperm transport by action on smooth muscle in the male and female reproductive tracts
It plays a role in ovulation
It play an important role in menstruation
It contributes to preparation of the maternal portion of the placenta
It contributes to parturition
What are the two components of the male sex act?
Erection
Ejaculation
What is the definition of erection?
Hardening of the normally flaccid penis to permit its entry into the vagina
How is erection accomplished?
Engorgement of the penis erectile tissue with blood as a result of marked parasympathetically induced vasodilation of the penile arterioles and mechanical compression of the veins
What are the two phases of ejaculation?
Emission phase
Expulsion phase
What is the definition of emission phase?
Emptying of sperm and accessory sex gland secretion (semen) into the urethra
How is the emission phase accomplished?
Sympathetically induced contraction of smooth muscle in the walls of the ducts and accessory sex glands
What is the definition of expulsion phase?
Forceful expulsion of semen from the penis
How is the expulsion phase accomplished?
Motor-neuron-induced contraction of the skeletal muscles at the base of the penis
What are the different phases of the sexual response cycle?
Excitement phase
Plateau phase
Orgasmic phase
Resolution phase
Describe the excitement phase of the male sexual response cycle
It includes erection and heightened sexual awareness
Describe the plateau phase of the male sexual response cycle
Characterized by steadily increasing heart rate, blood pressure, respiratory rate and muscle tension
Describe the orgasmic phase of the male sexual response cycle
It includes ejaculation and other responses that are collectively experienced as intense physical pleasure
Describe the resolution phase of the male sexual response cycle
Return of genitalia and body systems to prearousal state
Describe the excitement phase of the female sexual response cycle
Initiated by either physical or psychological stimuli
Describe the plateau phase of the female sexual response cycle
Changes initiated during the excitement phase intensify
Systemic responses similar to those in male occur
Describe the orgasmic phase of the female sexual response cycle
The experience in females is similar to that in males except:
- no female counterpart to ejaculation
- do not become refractory following orgasm
Describe the resolution phase of the female sexual response cycle
Pelvic vasocongestion and systemic manifestations gradually subside
Time of great physical relaxation
