final bio test part 2

6.7 menstrual cycle

menstural cycle

ovarian hormones

estrogen and progesterone

pituitary hormones

LH (luteinizing hormone) and FSH (follicle stimulating hormone)

Follicular phase

• day one of the cycle is the onset of the follicular phase

• the endometrium (inner lining) starts to thicken

• follicles start to grow on the ovaries

follicular phase pt.2

• FSH signals an increase in ovarian estrogen (positive feedback)

• this estrogen thickens the endometrium again

• FSH also signals a group of follicles to develop (each follicle an egg is stimulated to grow)

Phase 1

• the follicles release even more estrogen. this increase in estrogen stimulates the release of from the pituary gland

• LH also builds the follecular walll

LH and estrogen have what kind of relationship?

Positive feedback as a large follicular wall means more estrogen is released

ovulation

• when LH spikes, the most developed follicle grows enough to rupture, releasing its ovum into the oviduct (fallopian tube)

• marks the end of the follicular phase

Very high estrogen levels inhibit……

LH and FSH to allow the frogression to phase 2

• this is negative feeback

Phase 2: Luteal

• endometrium continues to thicken

• the ruptured follicle becomes a corpus luteum which releases estrogen and progesterone

• progesterone maintains the endometrium

estrogen and progesterone

continue to inhibit LH and FSH until the next cycle begins (negative feedback)

if fertilization does not occur

• the corpus luteum breaks down

• progesterone and estrogen drop, causing the endometrium to break down

• the endometrium is shed during mentation

• menstruation marks the end of the cycle and beginning of the next follicular phase

progression of hormones

6.8 reproduction

In an unchanging environment what type of reproduction is likely to occur?

asexual reproduction

sexual reproduction

increases the variation required to adapt to a changing environment

human reproduction

• humans are sexually dimorphic

• hormones control the development of sex specific characteristics

• 10 weeks into pregnancy Gonadotropin releasing hormones are released by the fetus

Gonadotropin hormones

• allow for sex specific characteristics

• when present maternal hormones encourage female typical development

• testosterone form the fetal testis encouraging male-typical development

6 months after birth, gonadotropin…….

• stops being produced

• and children develop in similar ways until puberty

during puberty

• GnRH is released again by the hypothalamus

• GnRH flows directly to the pituary gland which release LH and FSH and these change the gonands

• (testies and ovarys)

LH and FSH

• bring on the menstrual cycle in females, increases estradiol and progesterone causing sex specific changes

• increase growth of the testies and secreation of testosterone in males causing changes

human egg (ovum)

Human sperm (Spermatozoa)

Spermatogenesis

• starts in the outer part of the seminiferous tubules and progresses inward toward the lumen

seminiferous tubules

• surrounded by a basement membrane

• there is a layer of diploid germinal epithelial cells beneath this membrane

• these are called spermatogonia (they go through mitosis)

spermatogonia

• stems cells that divide repeatedly by mitosis to replace themselves

• may also divide my meiosis to produce sperm

Sertoli cells

• nurse cells

• supply enerfy for differentialtion