Describe and explain the hypothalamic-pituitary-gonadal axes for males
GnRh is made in the hypothalamus and signals the pituitary gland to release the Luteinizing Hormone and Follicle stimulating hormone. The LH targets the interstitial cells of the testes. The FSH targets the nurse cells of the seminiferous tubules. LH then makes leydig cells which induces secretion of testosterone and other androgens. FSH makes sertoli cells which secrete inhibin and promotes spermatogenesis and spermiogenesis and secretes inhibin which adjusts the rate of FSH productions. The tesosterone matures the sperm. The androgens prevent the over secretion of GnRH.
Describe the hypothalamic-pituitary-gonadal axes for females follicular stage
GnRH is released by the hypothalamus which stimulates the anterior pituitary gland to produce and secrete FSH and produce but not secrete LH. FSH stimulates follicle growth and maturation. LH creates thecal cells(which help with corpus lutus formation). Granulosa cells of the follicle produce and secrete estrogen which as it increases inhibits LH. The FSH the negative feedback as
Describe the hypothalamic-pituitary-gondal axes for females just before ovulation
while the follicle matures it secretes estrogen that inhibits the secretion of LH but allows for LH to be stored in the pituitary gland. Estrogen also makes the anterior pituitary cells more sensitive to the action of GnRH. GnRH releases from hypo in rhythmic pulses. The anterior respond to pulses and release stored LH. LH surge takes place which is a quick rapid amount of LH dumped into the body. 24hrs later = ovulation. If no LH surge=no ovulation. Surge weakens and ruptures the follicle wall. (positive feedback)
Describe the hypothalamic-pituitary-gondal axes for females at the Luteal Phase
begins at ovulation. Corpus Luteum secrets progesterone which stimulates and sustains an endomeatrial development. After ovulation progesterone levels rise and estrogen levels fall. This supresses GnRH secretion. If not pregnant the CL will degenerate after 12 days after progesterone levels decline. IF pregnant hcg comes in and rescues the CL to keep progesterone levels up and the baby is now in charge. (negative feedback)
Name the male and female gonads and the "typical" male and female hormones.
Gonads- male- testes, female- ovaries
Male-Tesosterone, DHT (dyhydrotestosterone)
Female- Estrogen, Progesterone
What is a dominant follicle? How is it chosen?
The more estrogen makes FSH levels go down so growing follicles increase their receptors which leads to selection of the dominant follice which is typically the biggest follicle, it gets enough FSH because it has the most granulosa cells which increases its estrogen.
How can estrogen provide both positive and negative feedback in females? When and why does it happen?
Estrogen can provide positive feedback when its stimulating the follicle growth, also during LH surge.
Negative feedback for production granulosa cells which produces Estrogen inhibin. The inhibin makes it negative feedback in follicular phase. The production of inhibin from corpus L progesterone in luteum phase
Describe the path of sperm from Sertoli cell to urethra
start at Sertoli cells which keep an eye on everything else and give rise to the sperm cells.(spermiogenesis)- sends put into epididimus where they learn to swim and mature, go through the ductus deferens (long tube), the ampulla which is the expanded distal portion of dd that joins the duct, through the seminal glands , the ejaculatory duct carries fluid from seminal gland and ampulla to the urethra.
Describe the make up of semen, the organs that contribute to it, and its roles.
White, sticky fluid containing sperm & accessory organ secretions. Roles- Purposes:1) transport
2) nutrients 3) protection 4) activation 5) facilitate movement. Organs that contribute the seminal vesicles, prostate gland, and urethra carries it out
Where do sperm learn to swim?
epididymis- stay ~20 days; learn to swim
How does an erection happen?
-Dilation of arteries caused by Nitric Oxide
-The corpus spongiosum pores fill, expands, get heavier, thicker,
-Corpora cavernosa expands & compresses drainage veins which significantly decreases blood outflow
-Initiated by emotion, mental activity, sounds, smells & tactile sensations
Mechinism of penile erection in the male
sexual stimulation-parasympathetic neurons release NO, causing dilation of small arteries to penis- veings are compressed reducing blood flow away from penis and blood is also accumulating in the vascular spaces within the erectile tissues of penis. Penis swells and becomes erect.
What is the difference between spermatogenesis and spermiogenesis?
spermato- sperm formation- Occurs in seminiferous tubules, Begins around age 14, 400 million sperm made/day
spermio- formation of tail, formation of acrosome, removal of excess cytoplasm, last step
How many sperm are produced as a result of meiosis? How many eggs?
Four haploid spermatids/ spermatazoa are produced by meiosis.
One mature haploid egg/ovum
Why must both mitosis and meiosis occur to make gametes?
Mitosis- so that each parent cells create two daughter cells. The daughter cells then go through meiosis
Meiosis -is used to produce the sperm and the egg each of which have half the number of chromosomes as the starting cell. This is so that when a sperm fertilizes an egg the total number of chromosomes is equal to that in any other cell
What does it mean to be diploid? Haploid?
Diploid- 2N= 2 copies of each type of chromosome
Haploid-N= 1 copy of each type of chromosome
Name the products of Sertoli cells/Sustentacular cells & interstitial cells/Leydig cells.
What hormones stimulate the production of these products?
Sertoli= sperm and inhibin, come from FSH hormones
Leydig=testosterone, comes from the LH hormone
What are the other roles for testosterone in the body?
Growth of reproductive ducts, glands & penis
Secondary sex characteristics
pubic, body & facial hair
-deepening of voice
-thicker, oilier skin
-longer, more dense bones
-increased skeletal muscle size & mass
-increased metabolic rate
Describe the stages of oogenesis.
Mitosis of oogonium- complete midlife divisions before birth
Meiosis I- daughter cells prepare to undergo meiosis,remain in a state of suspended development until the individual reaches puberty, when rising levels of FSH trigger the start of the ovarian cycle.
Meiosis II- each month after the ovarian cycle one or more oocytes leave the ovary suspended in metaphase , only completed if fertilization occurs.
What triggers ovulation?
What is a corpus luteum? Why does it form? What does it secrete?
It is the yellow body thats left of the follicle after a woman ovulates. It forms to ensure that no other follicles are stimulated to develop. Continues to degenerate unless there is a pregnancy and hcg. Secretes progesterone and estrogen.
Where does fertilization typically occur?
What is hCG? Where does it come from? What is its role?
It is made by cells that form the placenta, which nourishes the egg after it has been fertilized and becomes attached to the uterine wall. Its role is to sustain the Corpus Luteum when fertilization occurs.
what is the difference between identical and fraternal twins?
Identical twins occur when one egg splits after fertilization
Fraternal twins is when 2 eggs are released and fertilized by 2 sperm. They are genetically no closer related then siblings
what is the role of the uterus?
receives the embryo and sustains it's development
describe the phases of the ovarian cycle
follicular phase, before ovulation, and luteal phase
what is the two cell theory of steroidogenesis?
Thecal produce androgens, granulosa contain aromatase. Takes both FSH and LH to develop estrogen and testosterone. produce steroids from the adrenal glands
describe the menstral phase
days 1-5, shedding of uterine lining/detachment of functional layer
describe the proliferative phase
days 6-14, rebuilding of endometrium stimulated by estrogen, new functional layer formed, layer thickensm glands enlarge and spiral arteries increase in number. E stimulates PR production in endometrial cells, E changes cervical mucus from thick and sticky to thin and watery
describe the secretory phase
days 15-28, endometrium prepares for embryo. Progesterone causes spiral arteries to elaborate, P causes uterine glands to enlarge, coil and secrete glycoproteins for embryo nutrients. Progesterone causes cervical mucus to become viscous from cervical plug
what causes shedding of uterine lining?
degeneration of corpus luetum. Estrogen and Progesterone decrease. Blood vessels in endometrium constrict and lining tissues, dissinigrate, flow off.
what are the extrauterine effects of estrogen?
promotes oogenesis and folicular growth in ovary, Anabolic effects on female reprotract, growth spurt @ 12, secondary sex chx: breast development, deposits of subcutaneous fat in hips and breasts, widening and lightening of pelvis, pubic and axillary hair, low blood cholesterol, Up HDL, facilitates Ca.