Reproductive System

Mammary Glands  Present in both sexes, but only function in females  Modified sweat glands  Function is to produce milk  Stimulated by sex hormones (mostly estrogens) to increase in size

Skin (cut) Pectoralis major muscle Connective tissue suspensory ligament Adipose tissue Lobe Areola Nipple Opening of lactiferous duct Lactiferous sinus Lactiferous duct Lobule containing alveoli Hypodermis (superficial fascia) Intercostal muscles First rib (a)(b)

Reproductive System Function

Endocrine system plays a large role  2 hormones:  Follicle Stimulating hormone – helps produce sperm and oocyte (egg)  Luteinizing hormone – helps produce testosterone and induce ovulation

Male Reproductive Functions Chief role – to produce sperm and testosterone

Spermatogenesis  Sperm production  Begins during puberty and continues throughout life  Only one sperm fertilizes an egg but a man make millions everyday  Involves meiosis – special nuclear division that halves the chromosomes  This process produces 4 functional sperm

 Sperm pack light – the sperm head contains compacted DNA (nucleus)  Anterior to the nucleus is the helmet like acrosome  When sperm comes into contact with a oocyte the membrane of the acrosome breaks down the follicle (outside) cells of the egg

(a) (b) Plasma membrane Tail Axial filament of tail Mitochondria Proximal centriole Nucleus Acrosome Distal centriole Midpiece Neck Head

Testosterone Production  Produced by the interstitial tissue of the testes but also released by the pituitary gland  Starts in puberty (in response to LH) and produced continuously (more or less) throughout life  Rising levels stimulate adolescent growth spurt, prompts reproductive organs to develop, underlies sex drive, and causes secondary sex characteristics

Secondary Sex characteristics  Deepening of voice  Increased hair growth  Enlargement of skeletal muscles  Increased bone growth and density

Female Reproductive Functions and Cycles

Ovarian Cycle  The total supply of eggs are present at birth  Ability to release eggs begins at puberty  Reproductive ability ends at menopause

Ovarian cycle  Cycle of how a egg undergoes change from an oocyte in the ovary, to an oocyte that is expelled for ovulation  This is triggered by LH and FSH  FSH starts the change  LH expels it from the ovary

(b) Ovarian cycle: Structural changes in the ovarian follicles during the ovarian cycle are correlated with (d) changes in the endometrium of the uterus during the uterine cycle. Primary follicle Secondary follicle Vesicular follicle Corpus luteum Ovulation Degenerating corpus luteum Luteal phase Ovulation (Day 14) Follicular phase

 After expulsion from the ovary the oocyte travels down the fallopian tube  If fertilized, produces an ovum which combines with the 23 chromosomes of the sperm to form a fertilized egg (46 chromosomes)  Meiosis here only produces one functional egg and 3 polar bodies (non functional)  If not penetrated by a sperm it simply breaks apart

(d) The three phases of the uterine cycle: Menstrual: Shedding of the functional layer of the endometrium. Proliferative: Rebuilding of the functional layer of the endometrium. Secretory: Begins immediately after ovulation. Enrichment of the blood supply and glandular secretion of nutrients prepare the endometrium to receive an embryo. The menstrual and proliferative phases occur before ovulation, and together correspond to the follicular phase of the ovarian cycle. The secretory phase corresponds in time to the luteal phase of the ovarian cycle. Menstrual flow Basal layer Functional layer Endometrial glands Menstrual phase Proliferative phase Secretory phase Blood vessels 28 Days

Uterine (Menstrual) Cycle  The window for implantation is only for a very short period each month  Occurs approx. 7 days after implantation  Menstrual cycle – cyclic changes that the endometrium goes through month after month, responding to changes in the levels of ovarian hormones in the blood  Progesterone and Estrogen (produced in ovaries) is regulated by FSH and LH  Estrogen produced in response to FSH  Progesterone in response to LH

 Generally both female cycles occur in 28 days  Ovulation typically occurs midway in the cycles (day 14)

Days 1-5  Endometrial layer is sloughing off  Accompanied by bleeding for 3-5 days

Day 6-14  Proliferative phase  Stimulated by a rise in estrogen levels produced by growing follicles of the ovaries  Endometrium starts to regenerate and blood supply increases  Ovulation occurs in the end of this stage in response to the sudden surge of LH in the blood

Day  Rising levels of progesterone act on the estrogen primed endometrium and increase its blood supply even more  It is the uterus preparing for fertilization and implantation  If fertilization does not occur ovarian hormones decrease which causes the blood supply in the endometrium to go into spasms and kink. Endometrial cells begin to die and sets the stage for menses to begin again on day 28

Secondary sex characteristics  Enlargement of accessory organs  Development of breasts  Appearance of axillary and pubic hair  Increased deposits of fat beneath the skin in general, particularly the hips and breasts  Widening and lightening of pelvis  Onset of menses