Lecture 9: Reproductive Physiology Flashcards
Where are the testes contained?
The scrotum
What is the purpose of the scrotum?
Support, protection, and temperature control
What do the testes store?
Sperm
What is the epididymis?
A duct that passes sperm to the vas deferens
When sperm passes the vas deferens where does it go?
The urethra, where it then exits the body
What is the “tunica dartos”?
A smooth muscle layer that wrinkles skin
What is the “cremaster muscles”?
The skeletal muscle that raises and lowers
What is the “pampiniform plexus”?
Small veins in the scrotum that form a countercurrent heat exchange
What are the testes?
A collection of seminiferous tubules embedded within interstitial tissue
Where are sperm cells produced?
Seminiferous tubules that are nourished by sertoli cells
What do leydig (interstitial) cells produce?
Androgens (testosterone, dihydrotestosterone, androstenedione)
What is spermatogenesis?
The formation of sperm
Where does spermatogenesis occur?
It occurs in the testes
What is the process of spermatogenesis?
Sperm cells start near the basal compartment and migrate towards abluminal compartment as they divide and develop.
What is the purpose of meiosis in spermatogenesis?
It results in haploid spermatids and promotes genetic diversity
What are the components of a sperm cell?
The acrosome, head, midpiece, and tail.
What purpose does the acrosome have in a sperm cell?
It is involved with fertilization
What purpose does the head have in a sperm cell?
It contains the nucleus
What purpose does the midpiece have in a sperm cell?
It generates energy needed for swimming (increased amount of mitochondria)
What purpose does the tail have in a sperm cell?
It provides the flagella for swimming
What do luteinizing hormones (LH) cause in leydig cells?
They increase testosterone synthesis, which stimulates spermatogenesis (as well as other T effects)
What do follicle stimulating hormones (FSH) do in sertoli cells?
They stimulate production of androgen binding proteins (ABP)
What does ABP bind in the male reproductive hormonal control system?
ABP binds to testosterone which increase the concentration of it in the testes
What are some functions of testosterone (androgens)?
Differentiation of fetal male internal genitalia, spermatogenesis, secondary sex characteristics (muscle mass, bone growth, etc), and libido
What are anabolic steroids?
They are testosterone antagonists that has a negative feedback effect on the pituitary (which results in less LH secretion)
What does decreased LH secretion cause in males?
Infertility, testicular atrophy, and impotence
What can the use of exogenous hormones mimic?
It can mimic hypersecretion, which is when too much or too little of a hormone is released
What is semen?
The secretion of sperm mixed with accessory gland secretions
What purposes does prostaglandins in semen serve?
Decreases the viscosity of cervical mucus & stimulates uterine contractions (facilitates the movement of sperm),
What does relaxin in semen do?
It increases the sperm’s motility
What does seminalplasmin act as?
An antibiotic
What happens to the sperm after ejaculation?
Clotting factors coagulate sperm then fibrinolysin liquifies the sticky mass
What kind of sexual stimuli can initiate erections?
Touch/mechanical stimulation of the penis, erotic sights, sounds, & smells (these are unique to higher mammals)
What is one other sexual stimuli that is unique to higher mammals?
Emotional or mental higher activity can also initiate an erection
What is the pathway that stimuli take when activating mating behaviors?
Sensory stimulus, hypothalamus, midbrain, medulla, then spinal cord
Describe in detail the sensory stimulus section.
Visual stimuli go to the optic chiasm, olfactory, auditory, and tactile stimuli also travel to the next step
Describe in detail the hypothalamus step.
There are estrogen receptors that receive an increased estrogen presence and increase nerve excitability where neurons then produce behavior specific peptides
Describe in detail the midbrain step.
It is the receiving zones for hypothalamic peptides and speeds up impulses
Describe in detail the medulla step.
It integrates pastural adaptation for lordosis (sexual receptivity) and mounting
Describe in detail the spinal cord step.
It generates signals to specific muscles for lordosis & mounting
What is oogenesis?
The production of female sex cells by meiosis
What is the oocyte, and what is it contained in?
The oocyte is an egg cell and is contained within a follicle (surrounding granulosa/follicle cells)
What is the first step in oogenesis?
In the fetal period, oogonia (2n stem cells) multiply by mitosis & store nutrients
What is the second step in the oogenesis?
Primordial follicles appear as oogonia and are transformed into primary oocytes
What is the third step in oogenesis?
Primary oocytes begin meiosis but stall in prophase I
What is the fourth step in oogenesis?
They turn into the first polar body and an oocyte
What happens to the first polar body from the fourth step on? (oogenesis)
Meiosis II of the polar body happens and they turn into two polar bodies which then degenerate
What happens to the oocyte from the fourth step on? (oogenesis)
Ovulation happens where a sperm is susceptible to sperm penetration.
What happens to the oocyte after sperm penetration? (oogenesis)
Meiosis II is completed and the penetrated sperm becomes an ovum (plus the degenerated second polar body)
What are theca cells?
Cells in the ovary that respond to LH (lutenizing hormones)
What are granulosa cells?
Cells in the ovary that respond to FSH (follicle stimulating hormone)
What does estrogen (E2) do in the ovary?
It encourages follicle development and signs of estrus (heat)
What does progesterone (P4) do in the ovary?
It supports pregnancy
What does prostaglandin (PGF2a) do in the ovary?
It signals when/if the animal did not become pregnant, and ceases progesterone
What is the estrous cycle?
Coordinated changes that occur cyclically until the animal becomes pregnant, it happens by ovarian, uterine, and behavioral events
What does polyestrous mean?
The animal cycles until they become pregnant (cow, queen, pig, rodents)
What are long day breeders?
They are seasonally polyestrous animals that breed when the days are long. (mares in the spring)
What are short day breeders?
They are seasonally polyestrous animals that breed when the days are short. (ewe, doe, elk, nanny in autumn)
What does monoestrus mean?
Animals that cycle once a year at a specific time (dog, wolf, fox, bear)
What is the follicular phase of the estrus cycle?
It is when the follicle on the ovary grows and develops. It ends with ovulation as the follicle turns into an oocyte.
What is the luteal phase of the estrus cycle?
There are two parts: metestrus & disestrus. The follicle collapses & CL becomes the dominant structure.
What does the CL (corpus luteum) secrete during the luteal phase?
The CL secretes progesterone & estrogen.
What happens to the CL when there is no pregnancy?
Prostglandin lyses the CL (which degenerates into the corpus albicans). This ceases the secretion of progesterone & estrogen.
What happens to the CL when there is a pregnancy?
The CL will continue to secrete progesterone & estrogen to support it until the placenta can take over
What are the ideal conditions needed for fertilization to occur?
Sperm deposition must occur no more than 3 days prior to ovulation or 24 hours after ovulation.
What is fertilization?
It is the sperm fusing to an egg, which results in a zygote
What are some examples of what happens to ejaculated sperm?
It can leak from vagina after deposition, be destroyed by vaginal acidic environment, fail to transverse cervix, be dispersed into the uterine cavity, or ideally, reach the uterine tubes
What is capacitation?
It is the removal of adherent seminal plasma proteins and the reorganization of plasma membrane lipids & proteins
What is an ovulated oocyte encapsulated by?
The corona radiata & zone pellucida
What is the corona radiata?
An outer layer of follicular (granulosa) cells that form around a developing oocyte within the ovary
What is the zona pellucida?
A thick, extracellular matrix that surrounds eggs & early embryos
What does sperm binding to the zona pellucida do?
It undergoes an acrosomal reaction which releases enzymes near the oocyte. Then, hundreds of acrosomes release their enzymes to digest the zona pellucida.
What is the fast block to polyspermy?
The fast block to polyspermy is membrane depolarization prevents more than one sperm from fusing with the oocyte membrane.
What is the slow block to polyspermy?
The cortical granules release enzymes that destroy sperm receptors. They also cause sperm already bound to receptors to detach.
Upon entry of the sperm, what does the second oocyte do?
It completes meiosis II and casts out the second polar body
What is it called when two pronuclei come together?
Fertilization
How are pronuclei created?
When the ovum nucleus swells, the 2 nuclei approach each other. When fully swollen, the two nuclei are called pronuclei.
What happens when the developing blastocyst “implants” in the uterus?
The inner cell mass becomes an embryo while the outer portion becomes part of the placenta.
What is maternal recognition of pregnancy?
The blastocyst produces factors that prevent PGF2a from degrading the CL. The CL continues to produce progesterone to maintain pregnancy.
What causes myometrial weakness & irritability in the last weeks of pregnancy?
An increase of estrogen
What causes uterine contractions as birth nears?
Oxycotin & prostlandin
What does emotional & physical stress create?
It activates the hypothalamus and sets up a feedback mechanism which releases more oxycotin
How many stages of parturition are there?
There are three.
What happens in the first stage of parturition?
The uterus contracts and pushes the fetus into the birth canal. The cervix begins to dilate and the water breaks at this point (amnion rupture). This takes anywhere from 1-6 hours.
What happens in the 2nd stage of parturition?
It begins with the fetus entering the birth canal and ends with the birth of fetus(es). There are usually 15-30 minutes in between multiple fetuses and takes from 20 minutes to 2 hours.
What happens in the 3rd stage of parturition?
The expulsion of the placenta.
What does prolactin do for lactation?
Prolactin stimulates milk production
What does oxytocin do for lactation?
Oxycotin stimulates milk “let down”
What does suckling do for lactation?
It stimulates the hypothalamus and sends signals to the pituitary to produce more oxycotin needed for milk “let down”
